RU2741860C1 - A method of using a virtual digital model of a patient's walking for the differentiated construction of an individual program of physical rehabilitation in the early recovery period of ischemic stroke, depending on the affected region - Google Patents

Abstract

FIELD: medicine/neurology.

SUBSTANCE: invention relates to kinesiology, neurophysiology, medical rehabilitation, functional diagnostics, and can be used on outpatient basis, rehabilitation centers for diagnostics, differential diagnostics, methods of studying motor dysfunctions in acute cerebrovascular accident (ACVI), choice of rehabilitation methods and control of its effectiveness in patients with manifestations and consequences of strokes. To build an individual program of physical rehabilitation (IPFR), including the selection of physical exercises, specific kinematic parameters of walking should be considered, determined depending on area affected by ischemic stroke (IS) according to virtual digital model of patient's gait (VDMG) obtained during 3D video analysis of movements using high-resolution digital optoelectronic system SMART-D, equipped with high-resolution cameras with motion scanning frequency of up to 100 Hz per second, followed by animation and graphic construction of virtual motion model. The defining kinematic parameters of the motor pattern for VDMG in IS in the vertebrobasilar system (VBS) should follow correction-requiring signs: forward tilt of pelvis in sagittal plane during phase of support and transfer, with corresponding displacement of center of mass, with magnitude of angle of displacement of the pelvis anteriorly - more than 10° from average standard indicator of 7°, in absence of deviations of pelvis from standard indicators in frontal plane; on paretic and healthy side - increased flexion in hip joint (HJ) in transfer phase with insufficient extension in support phase, by more than 10° compared to upper limit of normative indicator given in table 1 in description, and insufficient plantar flexion of paretic and healthy side during the support-transfer period. As correction-requiring signs, following kinematic parameters of motor pattern of VDMG are taken in IS in the middle cerebral artery (MCA): displacement of pelvis in frontal plane with elevation of pelvis on paresis side by more than 1.5° compared to the norm in transfer phase with corresponding reciprocal lowering of pelvis on healthy side, in absence of pathological displacement of center of mass in sagittal plane; excessive internal rotation in hip joint in horizontal plane on both sides during entire step cycle compared to normative indicator, with impaired flexion and extension functions, with predominantly pronounced dysfunction of hip extensor muscles on paresis side, and insufficient plantar flexion on paretic and healthy side during support-transfer period.

EFFECT: method provides shorter physical rehabilitation times by increasing its personalization and quality characteristics, targeting elimination of neurological deficit, depending on affected area; targeted training provides more complete and high-quality restoration of motor functions.

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Description

The invention relates to the field of medicine, neurology, kinesiology, neurophysiology, methods used in medical rehabilitation, functional diagnostics, and can be used on an outpatient basis, rehabilitation centers for diagnostics, differential diagnosis, methods for studying motor dysfunctions in stroke, when choosing rehabilitation methods and monitoring its effectiveness in patients with manifestations and consequences of strokes.

Stroke is the main cause of disability in cerebrovascular pathology. More than 80% of patients after acute cerebrovascular accident (ACVA) have disabilities of varying severity. Improving walking function after a stroke is one of the most important goals of rehabilitation therapy.

Walking is a well-automated cyclic locomotion. In the field of gait research, a set of primary characteristics of parameters and methods of their registration was formed: temporal characteristics, kinematic characteristics, support reactions. Temporal characteristics are divided into general parameters themselves (time of the step cycle, time of support and transfer of each leg, time of support on both legs and one leg) and special (moment and time of support on various parts of the foot). The basis of the method for studying kinematic characteristics is the registration of movements in the large joints of the lower extremity in three mutually perpendicular planes - sagittal, frontal and horizontal (Vitenzon A.S. Research of biomechanical and neurophysiological patterns of normal and pathological human walking. Moscow, 1983; Skvortsov D.V. Biomechanical methods of rehabilitation of gait pathology and body balance. Moscow, 2008).

The basic functional unit of walking is the step cycle. Functionally, the right and left legs are almost identical, with only slight physiological asymmetries. The main characteristics of the step cycle include spatio-temporal, kinematic and kinetic indicators (SJ Olney, C. Richards. Hemiparetic gait following stroke: part I: characteristics, Gait Posture 4 (2) (1996) 136-148; D.V. Skvortsov . Clinical analysis of movements. Analysis of gait. "Stimulus". 1996). Measurements of variability in step parameters are used to assess sensorimotor function (Grabiner PC, Biswas ST, Grabiner MD. Age-related changes in spatial and temporal gait variables. Arch Phys Med Rehabil 2001; 82: 31–35. Doi: 10.1053 / apmr.2001.18219 ; Herman T, Giladi N, Gurevich T, Hausdorff JM. Gait instability and fractal dynamics of older adults with a “cautious” gait: why do certain older adults walk fearfully? Gait Posture 2005; 21: 178–185. Doi: 10.1016 / j.gaitpost.2004.01.014).

The "gold standard" for human locomotion research is biomechanical analysis of video images of movements (Wonsetler EC, Bowden MG A systematic review of mechanisms of gait speed change poststroke. Part 2: Exercise capacity, muscle activation, kinetics, and kinematics. Top Stroke Rehabil 2017; 24 ( 5): 394-403. Doi: 10.1080 / 10749357.2017.1282413; Andriacchi TP, Alexander EJ Studies of human locomotion: past, present and future. Journal of Biomechanics 2000; 33 (10): 1217-1224. DOI: org / 10.1016 / S0021-9290 (00) 00061-0; TB Moeslund, E. Granum. A survey of computer vision based human motion capture. Computer Vision and Image Understanding 2001; 81: 231-268. Doi: 10.1006 / cviu.2000.0897).

Previously, video analysis was used primarily in high performance sports to improve performance and evaluate fine, highly specialized movements. Now close attention is paid to the study of the features of the spatio-temporal, kinematic and kinetic parameters of the step cycle in medical rehabilitation, their connection with the pathological process and the possibilities of restorative treatment (Jin Seok Seo, Hee Seung Yang, Suk Jung, Chang Soon Kang, Sunghun Jang, Dae Hyun Kim. Effect of reducing assistance during robotassisted gait training on step length asymmetry in patients with hemiplegic stroke Medicine (Baltimore) 2018; 97 (33): e11792. Doi: 10.1097 / MD.0000000000011792; Steven H. Collins, Arthur D. Kuo . Two Independent Contributions to Step Variability during. Over-Ground Human Walking. PLoS One. 2013; 28; 8 (8): e73597. Doi: 10.1371 / journal.pone.0073597; Hiba Souissi, Raphael Zorya, Julien Boudarhamb, Didier Pradonb , Nicolas Roche and Pauline Gerusa. Muscle force strategies for poststroke hemiparetic patients during gait. Topics in stroke rehabilitation. Top Stroke Rehabil; 2018 Oct 24: 1-8. Doi: 10.1080 / 10749357.2018.1536023; Yin g Xinga, Si-Dong Yangb, Fang Dongc, Man-Man Wanga, Ya-Shuo Fenga, Feng Zhang. The beneficial role of early exercise training following stroke and possible mechanism. Life Science 2018; one; 198: 32-37. doi: 10.1016 / j.lfs.2018.02.018).

Leading research centers abroad and in Russia are showing interest in this method for assessing the motor pattern. A number of scientific publications contain data on changes in motor act in ischemic stroke (IS) obtained using video analysis (C. Beyaert, R. Vasa, GE Frykberg. Gait post-stroke: Pathophysiology and rehabilitation strategies. Clinical Neurophysiology 2015; 45 (4 -5): 335-55.doi: 10.1016 / j.neucli.2015.09.005; Jin Seok Seo, Hee Seung Yang, Suk Jung, Chang Soon Kang, Sunghun Jang, Dae Hyun Kim. Effect of reducing assistance during robotassisted gait training on step length asymmetry in patients with hemiplegic stroke. Medicine (Baltimore) 2018; 97 (33): e11792.doi: 10.1097 / MD.0000000000011792).

The proposed method was the result of many years of research into the features of changes in movement depending on a particular stroke basin, which had not been previously studied.

Although subclinical structural and functional changes in the neuromuscular system develop with age, however, gait parameters (absolute duration of the step cycle, frequency, step base, support period and transfer period, kinematic curves) do not undergo significant changes. Only the speed and stride length were statistically significantly reduced in the age groups 67-86 years old. Previous studies do not demonstrate significant differences in the amplitudes of joint movements in elderly healthy people.

If the function of the lower extremities is impaired as a result of illness or injury, the locomotor process splits, which normally ensures the simultaneous performance of the main functions: movement and maintaining balance (postural control). The gait of persons who have suffered a stroke acquires a peculiar pattern, characterized by a decrease in speed, violation of kinetic and kinematic profiles, pathological asymmetry, an increase in the energy consumption of a motor act (C. Maria Kim, Eng JJ Magnitude and pattern of 3D kinematic and kinetic gait profiles in persons with stroke: Relationship to walking speed.Gait Posture 2004; 20 (2): 140-146.DOI: 10.1016 / j.gaitpost.2003.07.002; Stanhope VA, Knarr BA, Reisman DS, Higginson JS. Frontal plane compensatory strategies associated with self- selected walking speed in individuals post-stroke. HHS Author Manuscripts 2014; 29 (5): 518–522. doi: 10.1016 / j.clinbiomech.2014.03.013; Tyrell CM, Roos MA, Rudolph KS, Reisman DS. Influence of Systematic Increases in Treadmill Walking Speed on Gait Kinematics After Stroke. Physical Therapy. 2011; 91 (3): 392-403. Doi: 10.2522 / ptj.20090425).

The asymmetry of the step parameters largely depends on the developed differences in spatio-temporal and kinematic characteristics between the affected and healthy sides, muscle strength and support stability of the paretic limb (Patterson KK, Parafianowicz I, Danells CJ, Closson V, Verrier MC, Staines WR, Black SE, McIlroy WE. Gait asymmetry in community-ambulating stroke survivors. Arch Phys Med Rehabil 2008; 89: 304-10. Doi: 10.1016 / j.apmr.2007.08.142).

These disorders negatively affect the function of walking and lead to the fact that people after ACVA lead a more passive lifestyle than healthy persons of comparable age: more than 80% of the time is spent on a sedentary lifestyle, which results in a further decrease in cardiorespiratory reserves and general endurance. the quality of their rehabilitation suffers (Lynch EA, Jones TM, Simpson DB, Fini NA, Kuys S, Borschmann K, Kramer S, Johnson L, Callisaya ML, Mahendran N, Janssen H, English C2. Activity monitors for increasing physical activity in adult stroke survivors Cochrane Systematic Review Stroke 2018; 21: STROKEAHA118023088.doi: 10.1161 / STROKEAHA.118.023088).

Thus, medical researchers and practitioners are faced with the task of identifying such specific parameters, characteristics of walking in a particular localization of stroke, which could be taken into account for a significant acceleration and improvement of the quality of physical rehabilitation.

When studying movement patterns in patients with different localization of ischemic strokes at different times and different researchers studied various parameters of movement, in particular, walking, among which physicians tried to find specific for a particular localization of the stroke focus, but not the stroke basin.

A known method of partial assessment of violations of the walking pattern using biofeedback, including using the "Lokomat" system, in patients after a stroke, by studying the effect of the system on the clinical parameters of walking (speed, stride length, mobility when moving) (Klochkov A .S. Robotic systems in the restoration of walking skills in patients with stroke, abstract of thesis ... Ph.D., M., 2012, p. 26). Thus, pathological locomotor synergies are a characteristic manifestation of gait disorders in post-stroke patients, defined as the inability to perform isolated voluntary movements in a separate joint due to the fact that movements in other joints accompanying this movement cease to be voluntarily controlled. With the course of the recovery process, motor synergies, initially selective or reflex, acquire a close relationship with spasticity and friendly reactions (Knutsson E. et al., 1980; Mizrahi E.M. et al, 1979).

It is shown that the pathological pattern does not change according to the available estimated parameters for Lokomat. Assessment of the features of the motor stereotype of walking in this known method is an objective analysis of the kinematics of a person's walking using an opto-electronic system for registering locomotions (Dotsenko V.I., Voronov A.V. et al., 2005). The data obtained with the help of this analysis make it possible to determine the biomechanical features of human movements, and also, which is especially important, to study the kinematics of joint movements, which makes it possible to objectively assess changes in the angles of movement in the joints during walking. In the known method, the clinical and biomechanical characteristics of walking in patients with post-stroke hemiparesis were assessed, revealing pathological locomotor patterns in them. It was found that in most patients with post-stroke hemiparesis, circumduction of the paretic leg is observed during the transfer of the limb. The severity of circumduction can determine the subtype of the pathological locomotor pattern. At the same time, the peculiarity of these subtypes is determined not only by the clinical features and the severity of circumduction, but also by intra- and inter-articular interactions, both in the sagittal and frontal planes in the joints of the paretic leg when walking. At the same time, for video analysis of movements, we used the optoelectronic hardware and software complex "Video analysis of movements", produced by the scientific and medical firm "Statokin". With the help of software for the paretic limb, such temporal parameters of walking were calculated as the time of the support and transfer period in the step cycle, as well as the kinematic characteristics - the amplitude of movements (A), the range of angular velocity (AV) in the hip joint (HJ) in the sagittal and frontal planes and in the knee joint (KJ) in the sagittal plane. To study intra-articular and inter-articular angular synkinesias in the sagittal and frontal planes, specific synkinesia coefficients (K) were introduced. The examination of the biomechanical characteristics of walking using video analysis was carried out before and after the rehabilitation course on a treadmill moving at a speed of 0.5 km / h. As a result of clinical and biomechanical analysis, it was shown that patients with post-stroke hemiparesis have a significant violation of the temporal and kinematic parameters of walking in comparison with the norm.

However, this method does not provide the definition of clear criteria for the selection of a differentiated IPFR in a post-stroke patient, moreover, depending on the ischemic lesion basin (MCA or vertebrobasilar system, VBS).

It is also known (Borzikov V.V. et al. Video analysis of human movements in clinical practice (review) // STM ∫ 2015, v. 7, No. 4, pp. 201-210) the use of modern systems for video analysis of movements that allow obtaining three-dimensional images locomotion and combine video analysis data with the analysis of signals received from other measuring devices, such as a force platform, myograph, stabilographic platform. The method of video analysis (video capture) of movements is based on the technology of computer analysis of video images of the subject's movements, while video capture is carried out contactlessly, without using a cable connection between the recording device and the object of study. There are two types of video capture systems - marker (using markers, or sensors that are attached to the subject's body), and markerless, based on computer vision and pattern recognition technologies. Markers are active (transmit information about their state, provide simplicity and accuracy of information processing, but are often large and therefore can impede the movement of the object itself) and passive (reflector markers). Markerless video analysis technologies are based on the analysis of the relative position of inhomogeneous parts of an object's images in successive frames and require more complex calculations. The most widespread video capture technologies are using passive markers. Reflective sensors are attached to the subject's body, the signals from which are recorded by video cameras; the data is transferred to a computer, where information is processed on the basis of a specific computer model: the movements of a real object are animated, and a report is generated that allows you to analyze the graphically presented angular and linear kinematic characteristics of the studied movements. Obtaining objective and useful information depends on the number of video cameras, the design, the number and location of markers, the construction of a model that meets the research objectives and the choice of a software package for analytical data processing.

Passive markers used in biomechanical video filming are usually spherical, small in size (about 10–15 mm in diameter) and low in weight; they are covered with a retroreflective (ie directionally reflecting light) material. Directional illumination of markers is carried out by infrared LEDs located around the camera lenses (the use of the infrared range makes it possible to conduct research in visible light); light is reflected from the markers and returns to the camera lens with the subsequent determination of the coordinates of the markers in space.

To register the position of the studied body segment in space, it is necessary that several cameras work simultaneously. They should be located at different angles so that the object of study is always within their line of sight. There are two-dimensional (analyze the movement of an object on a plane) and three-dimensional, more popular motion capture systems. To obtain three-dimensional images, the minimum number of cameras must be at least eight; the greater the number of cameras increases the accuracy of the study, but makes it more labor intensive and expensive. All cameras in video capture systems are synchronized, their control is carried out using a local computer network. The video recording rate is usually 100 Hz (100 frames per second), i.e. marker recognition is updated 100 times per second, which is several times higher than the frequency spectrum of angular displacements during ground locomotion. In order for each pair of cameras to form a binocular field of vision of the required dimensions, the area of the room where the video analysis is carried out should be 100-150 m2. The interposition of the cameras and the coordinate system of the study area are determined using the calibration procedure (for this, a reference marked object with known geometric characteristics and position in space is used).

The number of markers installed on body segments depends on the research task: there should always be at least three markers within the visibility of at least two cameras (since the plane is defined in space by three points). In real conditions, a significantly larger number of markers are usually used to account for changes in the position of a body segment during movement and overlapping of the movement zones of different segments. As a rule, modern video capture systems provide ready-made clusters of markers in the form of plates with four markers placed on them for long segments of the limbs, “caps” with markers for the head, etc.

Recognition of the shape and position of body segments based on information received from sensors is the most difficult stage of video analysis. In modern video analysis systems, the possibility of constructing any two- and three-dimensional multi-link research models is usually realized, allowing to display the segments of the locomotor apparatus of interest to the researcher.

To "tie" the individual dimensions of the recorded body segments to the computer model, the subject is calibrated before the start of the study. For this, calibration markers are placed on it, which are necessary to determine the physical dimensions of the studied segments, as, for example, provided by the Simi Motion program (Germany). Calibration markers are placed on the bony protrusions of the subject's body in such a way as to indicate the boundaries of the limb or trunk segments; the exact localization of these markers is determined by the used computer model and accepted standards.

Software tools of modern video analysis systems provide the provision of primary kinematic data in accordance with the standards of the International Society of Biomechanics. These standards were developed by the Committee for Standardization and Terminology of this society so that the primary data of all biomechanical studies of human kinematics provided by different researchers were comparable with each other.

The standards for biomechanical reporting of joint kinematics are based on the use of a joint coordinate system that was proposed back in 1983 by E.S. Grood and W.Y. Suntay for the knee joint. The standards regulate terminology, bone landmarks for determining the boundaries of body segments, types of movements and their coordinate system (axes). Such standards have been developed for movements of the foot, lower leg, thigh, pelvis, spine, hand, forearm, shoulder (Wu G. et al. ISB recommendation on definitions of joint coordinate systems of various joints for the reporting of human joint motion - part II: shoulder , elbow, wrist and hand. J Biomech 2005; 38 (5): 981–992, http://dx.doi.org/10.1016/j.jbiomech.2004.05.042; Wu G. et al. ISB recommendation on definitions of joint coordinate system of various joints for the reporting of human joint motion - part I: ankle, hip, and spine. J Biomech 2002; 35 (4): 543-548). For example, to describe the movements of the foot in the ankle joint, anatomical landmarks are the apex of the medial malleolus, the apex of the lateral malleolus, the most medially located point of the inner condyle of the tibia, the most laterally located point of the lateral condyle of the tibia, tuberosity of the tibia, the median malleolus distance between the latices , the middle of the distance between the extreme points of the inner and outer condyles of the tibia.

Taking into account the indicated bone landmarks, definitions of standard anatomical planes of motion in the ankle joint (frontal, sagittal, transverse, torsional), neutral position in the ankle joint, coordinate systems (axes) of movements in it are given.

In clinical practice, video analysis of human movements is used to diagnose locomotor disorders and monitor the dynamics of recovery of motor functions during treatment (Simon RS Quantification of human motion: gait analysis benefits and limitations to its application to clinical problems. J Biomech 2004; 37 (12): 1869-1880, http://dx.doi.org/10.1016/j.jbiomech.2004.02.047). It allows you to study kinematics (spatial organization, or geometry, movements and their changes in time without taking into account the acting forces). The combined use of video analysis, tensodinamometric platforms, electromyography makes it possible to study the kinetics (power and energy characteristics) of movements, the level of activity of various muscle groups, intermuscular interactions and synergy of motor acts.

Video analysis has the most significant impact on the quality of decisions made in restorative medicine (optimization of kinesitherapy regimens, assessment of the results of rehabilitation of patients with cerebral palsy, the consequences of stroke, TBI), in traumatology and orthopedics (when deciding on surgery, when testing orthopedic equipment), when selecting prostheses and means of support.

Depending on the tasks to be solved, the patient's walking, movements of individual segments of the upper or lower extremities are studied using video analysis. The most common type of locomotion studied with the help of video systems is walking. The full walking cycle (double step period) is composed for each leg from the support phase and the limb transfer phase and is limited by the time period from the beginning of contact of the foot with the support until the beginning of the next contact of the same foot with the support. When conducting biomechanical video filming, the patient walks along a marked locomotor track, along and outside of which there are video cameras. The subject should be in the binocular field all the time, i.e. be seen simultaneously by at least two adjacent cameras. The area of the locomotive track covered by the video camera is called the active zone. The length of the core is determined by the length of the double step: at least one double step and about 50% of its length on each side must enter the core.

The nature and pace of the studied walking (normal, with support, with assistive devices, at the usual or at a different pace) are determined by the objectives of the study. For example, when analyzing walking at an arbitrary pace, the subject is asked to walk along the path at the usual speed at a comfortable pace; Having reached the end of the track, the subject turns 180 ° and goes to the other end of the track. In the kinematic analysis of gait, the movement of the general center of mass of the body and angular displacement in the joints of the lower extremities are determined with the calculation of linear and angular velocities and accelerations, with the determination of the shape and area of phase trajectories in the joints (Whittle MW et al. Defining normal ranges for gait parameter. In: Gait Anal Med Photogramm. Vol. 1-3. Oxford, Headington; 1987; pp. 46-47).

The bioelectrical activity of the muscles involved in walking and the strength response of the support are often recorded simultaneously, which makes it possible to study intermuscular interactions and synergies of the motor act. Various protocols and biomechanical models of video analysis of the kinematics and kinetics of the trunk, pelvis and lower extremities during walking are used, while the data obtained on their basis, as shown by a comparative study, correlate well with each other and therefore are suitable for comparison (Gorton GE, Hebert DA, Gannotti ME Assessment of the kinematic variability among 12 motion analysis laboratories.Gait and Posture 29 (3): 398–402, http://dx.doi.org/10.1016/j.gaitpost.2008.10.060; Ferrari A. et al. Quantitative comparison of five current protocols in gait analysis. Gait Posture 2008; 28 (2): 207-216, http://dx.doi.org/10.1016/j.gaitpost.2007.11.009).

In patients with cerebral stroke, video gait analysis makes it possible to identify pathological walking patterns and determine the directions of rehabilitation, complementing traditional methods of biomechanical examination of patients (Stokic DS et al. Agreement between temporospatial gait parameters of an electronic walkway and a motion capture system in healthy and chronic stroke populations. Am J Phys Med Rehabil 2009; 88 (6): 437-444, http://dx.doi.org/10.1097/PHM.0b013e3181a5b1ec).

It is known to conduct a three-dimensional analysis of kinematic curves at different walking speeds in 20 patients with hemiparesis, which developed as a result of stroke (Kim CM, Eng JJ Magnitude and pattern of 3D kinematic and kinetic gait profiles in persons with stroke: relationship to walking speed. Gait Posture 2004; 20 (2): 140-146, http://dx.doi.org/10.1016/j.gaitpost.2003.07.002). It was shown that even with minor movement disorders, when the patient manages to maintain a walking speed comparable to that of healthy individuals, the walking pattern changes significantly. Several typical pathological gait patterns have been described, with the most pronounced changes recorded in the frontal and sagittal planes, primarily manifested by hyperfunction of the adductor muscles of the thigh, insufficient flexion in the knee and hip joint, and a decrease in the dorsiflexion angle of the foot.

The degree of impairment correlated with walking speed. The authors convincingly prove that a detailed analysis of three-dimensional kinematic and kinetic profiles of gait makes it possible to purposefully stimulate certain muscles and achieve a higher level of rehabilitation in patients who have suffered a cerebral stroke (see above: Kim C.M., Eng J.J., 2004).

In general, video analysis of movements makes it possible to obtain objective information that is important for the clinician, which makes it possible to clarify the nature of motor disorders in various diseases of the musculoskeletal system and the nervous system and monitor recovery processes with greater accuracy and with less time.

However, in the above-mentioned known methods, there is no indication of the criteria that could be used in the study and assessment of violations of the motor pattern of walking in post-stroke patients in order to compile an IPFR depending on the presence of these disorders, taking into account a certain localization of the stroke (MCA pool or VHD).

It is known to conduct a video analysis of the movements of post-stroke patients (Voronov A.V. et al. Diagnostic and prognostic capabilities of computer video analysis of movements in neurorehabilitation, http://expodata.ru/~expopress/2005/mr/pmr05tez_voronov.php) using the above-mentioned computer complex "Video motion analysis" ("Statokin"), functioning with the use of video equipment of various formats: VHS, S-VHS, DIGITAL VIDEO. Registration of kinematic parameters of movements, depending on the used hardware and software, is possible with different frequencies: 25-50 Hz (PAL) and 30-60 Hz (NTSC). In a minimal configuration, you can use only one video camera with standard video input to a computer. The hardware and software parts of the complex make it possible to recreate and analyze the kinematic parameters of the step and other movements in the so-called “flat”, two-dimensional model, which naturally introduces certain restrictions on biomechanical research. The results of such a study were compared with the results of motion studies using the Qualisys Medical computer complex (Sweden), which recreates a volumetric motion model. This complex uses software packages Qualisys Track Manager (Sweden) and Visual3D (C-Motion Inc., USA).

In the presence of a number of restrictions associated with the absence of a volumetric model of the patient's movement, the domestic hardware and software complex "Video Analysis of Motions", nevertheless, allowed the researcher to obtain all the classical indicators of the angular and linear kinematics of a person, his phase trajectories and angular synkinesias, and also carried out mathematical modeling of optimal modes of neuromotor "re-education" of the patient. This modeling was achieved in this known method by determining trauma-safe modes of locomotion and other motor activity by minimizing inter-articular forces, taking into account the results of video analysis of movements. In this method, this is shown on the example of patients with cerebral palsy, in whom, during treatment, there was a gradual reduction to the normative indicators of the values of the articular angles, their ratios in different phases of the step. This normalization of the dynamic characteristics of locomotion was observed earlier than the therapeutic effect of the treatment was consolidated in its maximum expression. According to the authors of this study, this allows us to hope for the subsequent determination of the criteria for predicting the effectiveness of a particular treatment at the very beginning of its use.

However, this well-known publication also does not disclose the choice of criteria that could be used to construct the IPFR of a patient after ischemic stroke (IS), taking into account its localization (MCA basin or VHD).

There is also known a method for quantifying the effects of rehabilitation of patients after a stroke with lesions of the lower extremities (CN 106821388 A, 06/13/2017, authors: GE FEIYANG et al., Applicant: UNIV. SHANGHAI), relating to the technology of motion capture and its use in assessing the rehabilitation of function extremities, namely to step speed, step frequency, difference of steps to the left and to the right, both on the affected and on the healthy side. The restoration of the function of the lower extremities is assessed by the amount of lateral support compared with the contralateral swing of the affected side. For this, a systemic motion capture is performed using a display system, combining the use of information technology and medicine to analyze the parameters of a person's gait through the entire body motion capture system. The assessment steps are as follows:

- through the whole body motion capture system, the intelligent computer system collects and processes data on the position and rotation of the human skeleton in real time;

- taking the patient's healthy side as an object of comparison, measure the pace, step frequency, the difference between the left and right steps, as criteria for quantitatively assessing the degree of rehabilitation of the lower extremities, both at the current moment and throughout the entire rehabilitation period, calculate the "value of support for the affected side" and "healthy face swing value".

Walking is a deliberate action that is initiated voluntarily by an individual and is controlled by the cerebral cortex. The basic functional unit of walking is the step cycle. The average step cycle time for natural walking approaches one second. The stride cycle for each limb consists of two periods: the support period and the carryover period. The length of the stance period is 58 to 61% of the stride cycle, and the carryover period is 42 to 39%. In accordance with the presence of a right and left limb, a right and left step cycle is distinguished. The gait in persons with acute cerebrovascular accidents (ACVI), compared with the gait of healthy people, is characterized by a decrease in voluntary speed, changes in the kinematic and kinetic profiles of gait (range of angles of motion in the joints, peak moment, peak power) and pattern of movement in various planes.

The video analysis method makes it possible to clarify the nature of motor disorders, provides opportunities for targeted rehabilitation, as well as monitoring the recovery process.

Physical rehabilitation is recognized as a first-line strategy for reducing impairments of sensorimotor function and motor deficits in ischemic stroke (IS), stimulating brain reorganization, and reducing the lesion. According to the 2016 AHA / ASA Guidelines for Adult Stroke Rehabilitation and Recovery, physical rehabilitation methods have varying degrees of evidence from level 1A to II B.

Previously, as foreign researchers, (Elizabeth C. Wonsetler et al. A systematic review of mechanisms of gait speed change post-stroke. Part 2: Exercise capacity, muscle activation, kinetics, and kinematics // Top Stroke Rehabil. 2017 July; 24 (5): 394-403. Doi: 10.1080 / 10749357.2017.1282413) and domestic, in particular, in the works of the co-authors of this invention, it was shown (Belyaeva I.A., M.Yu. Martynov, Ya.G. Pekhova , A. A. Vershinin, A. P. Rachin, M. A. Eremushkin, E. I. Gusev. Relationship between the motor stereotype and localization of the focus in the early recovery period of mild ischemic stroke // Journal of Neurology and Psychiatry, 2019, vol. 119 , No.3, pp.53-61) that walking patterns are of great importance for assessing the functional state of the patient in the recovery period after a stroke. At the same time, our studies were a priority in establishing clear correlations between violations of certain specific characteristics of the patient's individual walking pattern and the localization of his stroke in the basin of the internal carotid artery (more often directly in the basin of the middle cerebral artery, MCA) or in the basin of the vertebrobasilar system (VBS) ...

The prototype of the proposed method for using a virtual digital model of a patient's walking for differentiated construction of an individual program of physical rehabilitation (IPFR) of a patient depending on the lesion basin in ischemic stroke (IS) in the early recovery period can be considered the method disclosed in a previous publication of the co-authors of the invention (Belyaeva I.A. ., M.Yu. Martynov, Ya.G. Pekhova, A. A. Vershinin, A. P. Rachin, M. A. Eremushkin, E. I. Gusev. Relationship between the motor stereotype and localization of the focus in the early recovery period of lung ischemic stroke // Journal of Neurology and Psychiatry, 2019, t.119, No.3, pp.53-61). It shows a study in the early recovery period of AI of differences in motor stereotype disorders depending on the basin in which the stroke occurred: SMA (middle cerebral artery) or VBS (vertebrobasilar system), and also gives general recommendations regarding the program rehabilitation of such patients should be selected depending on the specific gait disorders identified with one or another IS localization using a video motion analysis system.

In this known method, using biomechanical analysis of video images of movements (video analysis of movements), the nature of motor disorders was clarified by examining many different characteristics of walking:

a) spatio-temporal parameters of the stride cycle (length, base, speed, stride frequency, foot turn angle, percentage of the period of support and transfer),

b) kinematics (spatial organization of movements in the joints),

c) kinetic parameters,

d) the level of activity of various muscle groups and intermuscular interactions during movement using dynamic electromyography.

Video analysis of movements was carried out in a specialized laboratory equipped with a high-precision digital high-resolution optical-electronic system SMART-D for the analysis of all types of movement. The study was carried out twice, 2-14 days after admission to the hospital. According to the Davis protocol, 22 reflective sensors up to 20 mm in size were attached to the subject, the signals from which were recorded by 10 main digital cameras, as well as 3 video cameras for additional video filming. The cameras have high-sensitivity matrices and a scanning frequency of 100 Hz, which is many times higher than the frequency spectrum of angular movements during normal movements. All cameras were synchronized, their control was carried out using a local computer network with data transfer to a computer and subsequent information processing. When filming the video, the patient was offered to walk along the marked locomotor track with a usual gait at a comfortable pace, making 3-5 consecutive cycles. The movements were animated, and a report was generated to visually analyze the presented kinematic characteristics of the movements. As a result of the study, an “individual drawing” (pattern) of movement was created, i.e. its a virtual model.

In a comparative analysis of the spatio-temporal parameters of the step cycle and the IS pool, it was found that regardless of the IS pool, the length and speed of the step significantly decreased, as a result of which the step cycle increased. However, in stroke in the MCA basin, despite the presence of mild to moderate paresis, changes in these parameters were less pronounced than in stroke in the VHD without force paresis. When assessing the stride length depending on the IS pool, significant differences were found for the paretic limb: in patients with the lesion localized in the VHD, the stride was significantly shorter than in patients with the MCA localization (t = 2.46, p = 0.036). The stride length of the healthy limb also differed between the groups: t = 1.93, p = 0.085 - a tendency towards significant differences.

We also studied such an important parameter of the step cycle as the width (base) of the step, which determines the stability when walking. A typical stroke response — an increase in stride base — indicates imbalance. The step width in both variants of stroke localization (VPS and MCA) significantly increased compared to the norm (t> 3.72, p <0.003). With the localization of stroke in the VPS basin, a more pronounced increase in the step width was noted than with localization in the MCA. Comparative analysis of the movement showed that the base of the step is associated not only with a decrease in muscle strength, but also with a decrease in the function of postural control and motor skills.

Postural control is defined as the ability to stabilize the center of mass of the body above the support surface during dynamic movement, as predicting the place of application of the center of gravity (centering) and maintaining the correct ratio of body segments for balance.

Postural motor skills are motor work that guarantees support for the alignment of the center of mass under static and dynamic conditions within certain limits, in order to maintain the correct body proportions and balance.

When analyzing the time indicators that make up the step cycle, there was a significant increase in both the absolute and relative time of the support period of the paretic limb in sec and% (t> 2.19, p <0.048) and the lengthening of the step cycle compared to the norm (t> 2 , 19, p <0.048), which is a consequence of a decrease in speed and / or step frequency. It is important to note that the stride cycle increased somewhat more on the healthy side than on the paretic side. When analyzing the phase indicators that make up the step cycle, no pronounced deviations from the norm were found in patients with a mild degree of movement disorders.

A comparative analysis of the kinematic parameters of the step cycle was carried out depending on the IS basin. During the step cycle, the pelvis normally moves in the frontal plane with an amplitude of about 4 °. When analyzing the data in patients with stroke in the MCA basin, the pelvis on the paresis side was raised above the healthy side by an average of 1.5 °. There was no pronounced displacement of the pelvis anteriorly in the sagittal plane.

On the contrary, in patients with IS in the IHD basin, a pronounced displacement of the pelvis anteriorly (the angle of deviation from the norm is more than 10 °) was revealed, which also suggests a displacement of the center of mass. The anterior position of the pelvis is most likely due to the shortening of the hip flexor muscles (the tendon of the wide fascia of the thigh) and the lengthening (insufficiency) of the hip extensor muscles (gluteus maximus and medius), whose function is to stabilize the pelvis in the sagittal plane. Hypofunction of the extensors of the hip joint is also indicated by excessive flexion of the hip joint with insufficient extension in the sagittal plane. A more pronounced tilt of the pelvis anteriorly is also associated with a shift in the center of mass. In individuals with IS, no such dependence was noted in the SMA system.

Thus, the prototype presents a descriptive study of a number of the above-mentioned parameters of movement of patients depending on the pool of ischemic ACVA, but without highlighting specific exhaustive criteria for determining a specific individual program of physical rehabilitation (IPFR) for a patient with lesions in the MCA or VHD pool.

The analysis of the obtained results showed that in patients with IS, even with a slight severity of paresis, when it is possible to maintain a walking speed close to the normal variant, the walking pattern is significantly changed. Deviations of both spatio-temporal and kinematic parameters are noted. Mobility in the joints is impaired (flexion / extension in the hip joint and knee joint suffers first of all), the center of body mass is shifted, the base of the step increases, the posture of the lower limb changes during movement as a result of muscle dysfunction and postural motility. With more pronounced paresis, all spatio-temporal parameters suffer, the structure of the step cycle is disrupted, and pathological asymmetry of movement increases.

For further research, we set the task of determining the criterion parameters of gait disorders, which would make it possible to compose IPFR from target exercises aimed at eliminating directly detected disorders that have a key role in the development of a pathological motor stereotype, in contrast to a number of other disorders that are only a consequence data of primary violations. This would make it possible to shorten the terms of rehabilitation by increasing its individualization, targeting it to eliminate the initial, key motor disorders that depend on the affected area.

Thus, clinical and experimental studies convincingly prove that active physical training is the main means of rehabilitation, surpasses in efficiency the widespread methods (massage, physiotherapy, reflexology, herbal medicine, etc.) in restoring the motor pattern. Separately, the role of targeted training for certain muscle groups and motor disorders, mainly those suffering from one type of paresis or another, is highlighted. The goal of targeted training is to maximize functional impairments due to stroke in order to restore specific motor skills. Undifferentiated kinesiotherapy is inferior to the effectiveness of the results of targeted training.

Currently, more and more attention is paid to the differentiation between true (focal lesion of the brain substance) disorders of motor functions and compensatory, adaptive reactions of the body to the existing deficit, the difference in the processes of true recovery and adaptation in rehabilitation after a stroke (C. Beyaert, R. Vasa, GE Frykberg. Gait post-stroke: Pathophysiology and rehabilitation strategies. Clinical Neurophysiology 2015; 45 (4-5): 335-55. Doi: 10.1016 / j.neucli.2015.09.005; Van Criekinge T, Saeys W, Hallemans A, Velghe S, Viskens PJ, Vereeck L, De Hertogh W, Truijen S. Trunk biomechanics during hemiplegic gait after stroke: A systematic review. Gait Posture 2017; 54: 133-143. DOI: 10.1016 / j.gaitpost.2017.03.004).

At the same time, at the moment there is still no understanding of the criteria for choosing the optimal model of physical training for restoring a motor stereotype. Standard rehabilitation programs for patients who have undergone IS are aimed at working with a paretic limb. Until recently, the healthy side function was used as a reference point. There was also no differentiation of treatment activities depending on the ONMK basin.

An important detail that makes it possible to choose an effective individual training model (IPFR) after undergoing AI is knowledge of the features of the kinematic parameters of the motor pattern in stroke in MCA or IHD. True motor impairments need to be recognized and rehabilitated with a dedicated exercise program; secondary, compensatory disorders may not require specific rehabilitation interventions and are solved by eliminating only the main motor disorders.

The technical result of the proposed invention is to reduce the rehabilitation period by increasing the individualization of physical rehabilitation, its targeted focus on the elimination of specific key neurological disorders that depend on the lesion basin - SMA or VHD, while compensatory disorders do not require special rehabilitation, recovery, since they are leveled in the future by restoring key movements, such targeted training provides a more complete and high-quality restoration of motor functions.

For this, we have proposed a method for using a virtual digital model of a patient's walking in the differentiated construction of an individual program of physical rehabilitation (IPFR) in the early recovery period of ischemic stroke (IS), depending on the affected area.

To construct an IPFR, including the selection of physical exercises, specific kinematic parameters of walking are taken into account, which are determined depending on the AI pool using a virtual digital model of a patient's walking, obtained during 3D video analysis of movements using a high-resolution digital optical-electronic system SMART-D, equipped with cameras with high-resolution matrices with a motion scanning frequency of up to 100 Hz per second, followed by animation and graphic construction of a virtual motion model.

At the same time, the presence of a combination of the following features requiring correction is taken as the kinematic parameters of the motor pattern for characterizing the virtual digital model of a patient with IS in the vertebrobasilar system (VBS):

- the forward tilt of the pelvis in the sagittal plane during the phase of support and transfer, with a corresponding displacement of the center of mass, with an angle of displacement of the pelvis anteriorly - more than 10 ° from the average standard indicator of 7 °, in the absence of deviations of the pelvis from the standard indicators in the frontal plane,

- on the paretic and healthy side - increased flexion in the hip joint (HJ) in the transfer phase with insufficient extension in the support phase, by more than 10 ° compared to the upper limit of the standard indicator given in table 1 in the description,

- insufficiency of plantar flexion of the paretic and healthy side during the support-transfer period.

As the kinematic parameters of the motor pattern to characterize the virtual digital model of the patient's walking with IS in the middle cerebral artery (MCA) basin, the presence of a combination of the following features requiring correction is taken:

- displacement of the pelvis in the frontal plane with the raising of the pelvis on the side of paresis by more than 1.5 ° compared to the standard indicator (table 1, the norm is the range from -4 to 4 °) in the transfer phase with the corresponding reciprocal lowering of the pelvis on the healthy side, in the absence of pathological displacement of the center of mass in the sagittal plane,

- excessive internal rotation in the hip joint in the horizontal plane on both sides during the entire step cycle compared to the standard indicator, with dysfunction of flexion and extension, with predominantly pronounced dysfunction of the hip extensor muscles on the side of paresis. Rotation is determined with the patient supine, with legs extended. The patella is facing up. The soles of the feet are at a 90 ° angle to the lower leg. The protractor is attached to the middle of the foot, the jaws are closed, going to the second toe, the protractor screw is in the middle of the heel. It is possible to determine rotational movements with a bent limb in the hip and knee joints at an angle of 90 °, the goniometer branches are located along the axis of the lower leg. When rotating inward or outward, the entire leg rotates inward or outward, while one branch follows the movement of the foot, the other remains in place. Normally (standard indicators) rotation outwards by 60 °, inward 45 ° (depends on the elasticity and fitness of the ligamentous apparatus). When determined by Marx, rotation is external / internal 50 ° / 0 ° / 50 °;

- lack of plantar flexion on the paretic and healthy side during the support-transfer period.

Below are clinical data (example) confirming the possibility of implementing the proposed method and achieving its technical result.

In the early recovery period of IS, 30 patients were examined. The clinical diagnosis and localization of the ischemic focus was confirmed by the results of neuroimaging - MRI / CT of the brain. The ischemic focus in 50% of patients was localized in the MCA basin (middle cerebral artery, MCA), and in 50% - VHD. There were 13 men and 17 women. In the group of patients who had suffered a stroke in the VHD, the number of women was higher (66.7% and 33.3%, respectively); in the group with stroke in SMA, women and men accounted for approximately the same number (53.3% and 46.7%, respectively). The average age in the SMA group was 61.7 ± 7.2 years, in the VBA group - 59.5 ± 5.3 years. The examined patients were comparable in terms of body mass index, the presence of diabetes mellitus and the percentage of smoking. Among the vascular risk factors in both groups of patients, the following were mainly noted: atherosclerosis of the brachiocephalic vessels of varying severity, poorly controlled arterial hypertension, smoking, dyslipidemia. At the same time, in the study groups there were no: heart failure of the III degree and higher, unstable angina pectoris, heart defects.

The study included patients without pronounced movement disorders with a decrease in muscle strength up to 3-4.5 points. The criterion for the inclusion of patients in the study was the absence of diseases of the musculoskeletal system and arthroplasty.

Upon admission to the second stage of rehabilitation (3-4 weeks after the underwent IS, early recovery period), all patients underwent clinical and neurological examination, which showed the comparability of the clinical course of the disease.

All patients underwent clinical examination using validated international rating scales. Independence in daily life, mobility, and patient self-care were assessed using the Functional Independence Measure (FIM) scale. The severity of paresis and manifestations of spasticity was assessed using the 6-point scale for assessing the severity of paresis and the Modified Ashworth Scale for Grading Spasticity, modifided Bohannon and Smith, respectively. Hand function, fine motor skills, and finger dexterity were assessed using pegs and nine holes (NINE-HOLE PEG TEST - NHPT). Patient mobility was assessed using the Time up and go test (TUG). Balance function was evaluated using the Berg Balance Scale (BBS) test and a 20-point vertigo scale. Emotional status and cognitive functions were assessed using the Mini-Mental State Examination (MMSE), the Beck Depression Inventory (BDI), and the Spielberger anxiety scale (State-Trait Anxiety Inventory - STAI). The patients included in the study did not have severe paresis, pronounced manifestations of spasticity and cognitive impairment.

All patients included in the study underwent examination using video analysis of movement at 3-4 weeks after the acute period of IS to clarify the features of changes in the kinematic parameters of the motor pattern in case of unexpressed paresis, depending on the affected area.

Video analysis of movements was carried out in a specialized laboratory SMART (Germany), equipped with a high-precision digital high-resolution optical-electronic system SMART-D for the analysis of all types of movement, as in the prototype method.

The average duration of the study is 60 minutes, of which work with the patient is 20-30 minutes and the formation of the conclusion protocol is 30 minutes. The gait analysis uses the validated international Davis protocol. According to the protocol, 22 reflective sensors up to 20 mm in size are used, the signals from which are recorded by cameras. The cameras have a scanning frequency of 100 Hz, which is many times higher than the frequency spectrum of angular displacements during normal movements. The cameras are synchronized, control is carried out using a local computer network with data transfer to a computer with subsequent information processing.

The system also includes power platforms based on piezoelectric sensors. The platforms are multicomponent and register the force kinetic parameters of walking in three directions x, y and z (transverse, longitudinal and vertical support reactions), the projection of the center of gravity (Px, Py) and the moment of force (Mz).

During the study, the patient was asked to walk along the marked path with a usual gait, barefoot at a comfortable pace, performing 5 consecutive cycles of movements. The movement was animated and a report was generated to analyze the visualized kinematic characteristics of the movements. As a result of the study, an "individual pattern" of movement was created - a virtual digital model of walking. Information processing was carried out using the Smart-Clinic software tool.

Statistical analysis was performed using Microsoft Excel for Windows XP and IBM SPSS Statistics, version 23, 2015. Descriptive and comparative statistics were used in the study. To evaluate quantitative parameters, the arithmetic mean and standard deviation (M ± SD) were calculated. The analysis used the nonparametric Mann-Whitney test for unrelated (non-conjugated) populations, as the most powerful for samples of less than 30 observations. Differences were considered statistically significant if the error probability (p) was less than 0.05.

With the help of a three-dimensional video analysis of the function of movement and support, an individual program of locomotor reconstruction was formed, and targets were set for rehabilitation strategies aimed at restoring the effective functioning of the patient.

In our study, patients of both groups (with strokes in the MCA and VHD basins) did not differ clinically in the severity of central paresis in the leg, had minor but significant differences in the degree of paresis in the arm. The location of the foci in stroke in the MCA and VHD system was characteristic of localization for each of the pools. At the same time, according to the MRI data, there were no localization features of the lesions affecting the severity of leg paresis.

At the same time, the study of the gait structure in these patients with central paresis by the video analysis method showed significant differences in the kinematic parameters of the motor pattern of the MCA and VPS basins.

Normal and pathological (depending on the area of the lesion) values of the amplitudes of movements of the pelvis (girdle of the lower extremities) and joints of the lower extremities during movement are presented in Table 1.

Table 1

Parameters of the kinematic characteristics of the pelvis (girdle of the lower limb) and lower limb, depending on the basin (M ± SD).

Indicator SMA pool
(n = 15) Norm
degrees Pool VBS
(n = 15) p-value
(between groups)
on the side of paresis Healthy
side
(degrees) Paretic side
(degrees) Healthy
side
(degrees) Paretic side
(degrees) Oblique pelvic tilt (frontal plane) -4.6 ± 1.5 * 4.6 ± 1.5 * From -4
up to 4 -2.4 ± 1.9 2.4 ± 1.9 <0.003 ** Straight pelvic tilt (sagittal plane) 8.1 ± 3.3 8.1 ± 3.3 7 ± 5 16.4 ± 3.8 * 16.4 ± 3.8 * <0.001 ** Hip flexion 36.7 ± 6.5 * 36.5 ± 7.5 * 30 ± 10 45.4 ± 7.2 * 43.9 ± 8.4 * 0.02 ** Hip extension -5 ± 8 * -3.5 ± 8.1 * -10 ± 5 5.3 ± 7.0 * 6.6 ± 9.2 * 0.002 ** Knee flexion 59.5 ± 7.4 60 ± 8.5 60 ± 5 64.6 ± 8.4 61.6 ± 11.3 0.49 Knee extension 6 ± 7.5 * 9.1 ± 5.6 * 2 ± 8 13.2 ± 11.7 * 13.7 ± 11.6 * 0.27 Dorsiflexion of the foot 16.8 ± 5.1 * 17.8 ± 4.9 15 ± 5 20.2 ± 3.5 * 18.8 ± 3.4 * 0.29 Plantar flexion of the foot -4 ± 6.4 * -4.5 ± 5.2 * -15 ± 3 -0.9 ± 7.9 * -2.3 ± 6.9 * 0.20

Note: * - differences from the norm are reliable at p <0.05;

** - differences between groups are significant at p <0.05.

Normally, the movement of the pelvis in the frontal plane is characterized by deviations not exceeding 4 ° (table 1). Stabilization of the pelvis is achieved by the combined functioning of the muscles-stabilizers of the spine: the transverse abdominal muscle, the muscle that straightens the spine, the iliopsoas muscle; gluteal muscles and muscles of the thigh. The muscle-tensor of the wide fascia of the thigh, together with the middle and small gluteus muscles, makes the main contribution to maintaining the horizontal position of the pelvis (stabilization in the frontal plane), and the gluteus maximus muscle - to stabilize the pelvis in the sagittal plane.

The stride cycle for each limb consists of two main periods: support and transfer. In this case, the angles of movement in the joints are directly related to the spatio-temporal indicators of the step cycle (length, frequency, step speed). In the middle of the transfer phase of the hip joint, the knee and ankle joints are in the position of maximum flexion.

The video analysis showed that in all patients after IS, the walking pattern in all three planes deviated from normal values. There is a change in both kinematic and space-time characteristics. The spatio-temporal parameters of the step cycle significantly differed from the norm in the direction of decreasing for the length and speed of the step, as a result of which the step cycle was lengthened (the time of support and the time of transfer of the paretic and simultaneously healthy limb); a significant increase in the step base is noted. At the same time, no statistically significant differences were found between the healthy and paretic sides.

However, the study also showed that, in comparison with the norm, such kinematic parameters as : displacement of the pelvis in the sagittal and frontal planes, the angles of deviations of the hip joint, knee and ankle joints, depending on the affected area, change . Moreover, the changes in the hip joint and ankle are of the greatest importance. These impairments reduce gait reliability, increase the risk of falls, and complicate postural control during movement. At the same time, for the aforementioned kinematic parameters of the motor act, we established significant differences depending on the ischemic stroke basin.

When assessing the movements of the pelvis after IS in the VPS, its pronounced forward displacement in the sagittal plane was noted during the phase of support and transfer (movement). In the frontal plane, there were no deviations in the movement of the pelvis from the standard indicators (table 1). The forward tilt of the pelvis in the sagittal plane is associated with the forward displacement of the center of mass, which significantly reduces the reliability and safety of walking, increases the risk of falls when walking, increases energy consumption when leveling the postural tone and maintaining body balance. The tilt of the pelvis is due to compensatory mechanisms for maintaining the posture.

One of the most important functions of the hip joint extensor muscles, in particular the gluteus maximus muscle, is the stabilization of the pelvis in the sagittal plane. Anterior displacement of the pelvis indicates hypofunction of the gluteus maximus and medius (Table 1, Figure 1, I.A). If it is impossible to make full extension in the hip joint, one of the compensation mechanisms is activated due to the opposite hip joint. A healthy limb “copies” the pattern of movement of the paretic one, that is, on the healthy side, flexion in the hip joint is also enhanced with insufficient extension - a mechanism for compensating for violations. If, despite this compensatory mechanism, it is not possible to achieve optimal verticalization of the body, the center of mass shifts, which we see in this group of patients - the pelvis is tilted forward. The location of the center of mass, and, consequently, the safety and reliability of movement, depends on the inclination of the pelvis in this plane. In this regard, the magnitude of the anterior displacement of the pelvis due to the dysfunction of the listed specific muscles, in this case, was chosen as one of the most important signs, which should be targeted at targeted physical rehabilitation.

When analyzing movements in the hip joint after a stroke in the basin of the IHD, changes in the kinematics of movements in the sagittal plane and no changes in the frontal plane were noted. In the sagittal plane, excessive flexion of the hip joint was recorded during the transfer period and insufficient extension during the support phase on both the paretic and healthy sides (Table 1, Figure 1, II.A). Even with mild paresis, an increase in flexion was detected, which is regarded as an adaptive response necessary for an increase in stride length. Insufficient extension could also be due to spastic tone of the flexor muscles (fascia lata tenor, rectus femoris) and / or insufficiency of the extensor muscles (gluteus maximus, posterior thigh muscle group).

With the severity of paresis no more than 4 points, the kinematic parameters of the knee joint movement were within the reference values (Table 1). With more pronounced paresis (less than or equal to 3 points), there was an increase in flexion in the knee joint with its insufficient extension (Table 1, Figure 1, III.A). However, in this case, changes in the knee joint were regarded more as derivatives of pathological changes in two other large joints - the hip joint and the ankle; subsequently, these changes in the work of the knee joint were leveled out during the implementation of rehabilitation measures aimed at these two main joints.

In the ankle joint, there was a lack of plantar flexion from 2 sides during the support-transfer period (Table 1, Figure 1, IV.A).

Thus, hyperfunction of the flexor muscles was detected in case of insufficient function of the extensor muscles of the hip joint and knee joints (impaired functional relationships between agonist and antagonist muscles), displacement of the pelvis anteriorly in the sagittal plane (Table 2), which explains the increased risk of falls in this group of patients even with unexpressed power paresis.

table 2

Features of the kinematic characteristics of the motor pattern in individuals in the early recovery period of IS, depending on the area of the lesion

The investigated parameter VBS SMA Displacement of the pelvis
sagittal plane Significant displacement of the pelvis anteriorly in the sagittal plane (angle of deviation more than 10 °), p <0.001 * There is no pronounced displacement of the pelvis anteriorly (the angle of deviation is not more than 5-10 °), p = 0.36 Displacement of the pelvis
frontal plane Pelvic movements in the frontal plane are not disturbed, p = 0.7 Pronounced pelvic tilt in the frontal plane (the side of the pelvis at the level of paresis is raised), p <0.001 * TBS
flexion / extension Increased flexion in the hip joint ( p <0.001 * ) with insufficient extension from 2 sides (angle of deviation more than 10 °), p <0.001 * Less pronounced extension in the hip joint, mainly pronounced on the side of paresis ( p <0.001 * ) with normal flexion from 2 sides.
Increased internal rotation of the thigh, mainly on the side of the paresis. Knee-joint
flexion / extension Normal or increased flexion in the knee joint ( p <0.14) with insufficient extension from 2 sides, p <0.001 * Normal flexion in the knee joint from 2 sides ( p = 1 on the paresis side, p = 0.65 on the healthy side) , with less pronounced extension on the paresis side, p <0.001 * Ankle joint
flexion / extension Insufficiency of plantar flexion on 2 sides, p <0.001 * Insufficiency of plantar flexion on 2 sides, p <0.001 *

Note: * - differences from the norm are reliable at p <0.05

A feature of the pelvic movements in the localization of foci in the MCA basin was the inclination of the pelvis in the frontal plane (up-and-down displacement, oblique tilt), while in the sagittal plane the pelvic movements were within the standard values. The inclination of the pelvis in the frontal plane was characterized by the fact that the pelvis was raised on the paretic side during the swing phase and did not fully descend during the stance phase, the indicators were significantly different from the norm (Table 1, Figure 1, I.B). At the same time, reciprocal lowering of the pelvis occurred on the healthy side.

When analyzing the movements in the sagittal plane, a predominant lack of extension in the hip joint was noted. Extension disorders were detected on the affected and healthy side, but more pronounced on the paresis side. Flexion in the hip joint on the paretic and healthy sides significantly differed from the norm, but the disturbances were significantly less pronounced than in stroke in the VHD (Table 1, Figure 1, II.B).

When analyzing the movements of the hip joint in the horizontal plane, in contrast to the basin of the lesion in the IHD, with a lesion in the basin of the MCA, excessive internal rotation (rotation) was revealed on both sides with an increase in the range of motion and undifferentiated maxima (that is, the pattern of movement deviated from the normal picture, there were no peak deviations in Hip joint with internal rotation of the thigh). Rotation was more pronounced on the side of paresis during the entire step cycle. This can be explained by the weakness of the muscles involved in the external rotation of the thigh: the gluteus maximus muscle, the piriformis and other short muscles that rotate the thigh outward (the upper and lower twins, the internal obturator, the square muscle of the thigh), or an increase in the tone of the internal thigh muscle group.

When analyzing the knee joint movements in the sagittal plane, the most common tendency was insufficient extension on both sides, but more pronounced on the paresis side (Table 2, Figure 1, III.B). Lack of extension in the knee joint could be due to hypofunction of the anterior thigh muscle group, i.e. was associated with existing violations in the TBS. No significant differences with the norm were found in knee flexion (Table 1).

With the localization of the lesion in the MCA basin, as well as with localization in the IHD, there was a lack of plantar flexion on 2 sides (Table 1, Figure 1, IV.B), which affects a significant clinical indicator - walking speed and is associated with disability of the patient. At the same time, no significant differences were found between the groups of patients with stroke in MCA and VHD. However, this joint, as it plays an important role in the function of support, is one of the key ones for rehabilitation purposes.

The pathological asymmetry of movement parameters that develops after a stroke largely depends on the differences in kinematic characteristics between the affected and healthy sides; muscle strength and support stability of the paretic limb. In our study, in patients of both groups, the healthy side was also involved in the pathological motor act. Involvement of the healthy side indicated a lack of support function of the paretic leg. Due to the muscular weakness of the paretic leg, the period of its support decreased, which in turn led to a decrease in the period of transfer on the healthy side, and, consequently, the stride length on the healthy side.

Thus, it is the disturbances in the kinematic parameters of movement of large joints in certain planes on the paretic side, the displacement of the center of mass in the sagittal or frontal plane, depending on the localization of the stroke focus in the corresponding basin, that lead to changes that involve a healthy limb in the pathological process. Therefore, the targeted elimination of impaired functions on the paretic side through the training of certain muscle groups involved in the movement of the main large joints of the lower limb reciprocally leads to an improvement in the function and the healthy side, reducing the rehabilitation time and improving the quality of the motor pattern.

A comparative video analysis of the walking of patients in the early recovery period of IS in the basins of the MCA and VBS made it possible to identify the features and differences in the disorders of the kinematics of the motor stereotype, which are important when choosing rehabilitation exercises with a focus on the target muscle groups of the target joints (Table 1, Table 2). At the same time, the following were recognized as significant indicators established using the analysis of correlations:

1. As the kinematic parameters of the motor pattern for the characteristics of the virtual digital model of the patient's walking with IS in the vertebrobasilar system (VBS) , the presence of a combination of the following features requiring correction is taken:

- the forward tilt of the pelvis in the sagittal plane during the phase of support and transfer, with a corresponding displacement of the center of mass, with an angle of displacement of the pelvis anteriorly - more than 10 ° from the average standard indicator of 7 °, in the absence of deviations of the pelvis from the standard indicators in the frontal plane,

- on the paretic and healthy side - increased flexion in the hip joint (HJ) in the transfer phase with insufficient extension in the support phase, by more than 10 ° compared to the upper limit of the standard indicator given in table 1 in the description,

- insufficiency of plantar flexion of the paretic and healthy side during the support-transfer period.

2. As the kinematic parameters of the motor pattern for the characteristics of the virtual digital model of the patient's walking with IS in the middle cerebral artery (MCA) basin , the presence of a combination of the following signs requiring correction is taken:

- displacement of the pelvis in the frontal plane with an elevation of the pelvis on the paresis side by more than 1.5 ° compared to the standard indicator in the transfer phase with the corresponding reciprocal lowering of the pelvis on the healthy side, in the absence of pathological displacement of the center of mass in the sagittal plane,

- excessive internal rotation in the hip joint in the horizontal plane on both sides during the entire cycle of the stride compared to the normative indicator, with impaired flexion and extension functions, with predominantly pronounced impairment of the functions of the hip extensor muscles on the side of paresis,

- lack of plantar flexion on the paretic and healthy side during the support-transfer period.

In this regard, for the rehabilitation of patients with IS in the basin of the IHD and MCA, exercises aimed at eliminating the dysfunctions of the corresponding muscles responsible for movements in the hip joint and ankle joints were used.

The study groups with IS localization in the MCA and VBS pools were divided in half (7-8 people from two groups of 15 people each, a total of 30 people), while one part of the patients underwent physical rehabilitation taking into account the revealed violations of the kinematic parameters of walking (according to the declared method), and the second part - physical rehabilitation in an undifferentiated manner, without taking into account the localization of the stroke and the specific criteria we identified that fundamentally characterize the walking model depending on the lesion basin in the MCA or VHD.

In addition to active and passive physical exercises aimed at relaxing or stimulating the tone of specific, corresponding muscles, according to the characteristics of the kinematic chain of movements of the pelvis and lower extremities established by video analysis of differentiated disorders, as part of physical rehabilitation, all patients underwent exercises using hardware techniques, for example, functional electromyostimulation of weakened muscles, gait training on a sensory neuropath, stabilometric training to control the center of mass. We also used exercises for the lower extremities and the trunk within the framework of the NIRVANA system (http://www.keleanz.ru/catalog/65/195/), programmed in such a way as to use the muscles corresponding to the identified criterional disorders. However, during the operation of this system in this case, the disadvantage was the presence of a sufficiently pronounced visual control, while for the purposes of the claimed rehabilitation, it is more important to form a conscious teaching motor act for the formation of reflex proprioceptive control. For this purpose, we used the usual active and passive therapeutic gymnastics, including exercises to restore the functions of the corresponding muscle groups identified during the construction of the mentioned virtual digital walking model.

For these purposes, in addition, targeted training programs are possible using movements to control the position of the center of mass of the body, respectively, in the sagittal or in the frontal plane (for example, movements with torso tilts with additional weight forward and backward or to the sides, etc., with training to hold the achieved position).

Clinical example 1.

Patient O., 58 years old, was admitted with a diagnosis of ischemic stroke in the right MCA basin, early recovery period, moderate left-sided hemiparesis, dysfunction of the limbs and walking. Background disease: Hypertension grade III, risk 4. Neurological status: FMN - c. paresis VII n. left. The range of active movements is limited in the left limbs. Muscle strength is reduced in the proximal arm up to 4 points, in the distal - up to 3 points; in n / c up to 3 points proximally, 3.5 points distally. Muscle tone is slightly spastic on the left. Gait is hemiparetic. Tendon reflexes with i / c, n / c S> D. S. Babinsky (+) on the left. Left hemigipesthesia. In the Romberg position, there is instability, without sideways; coordination tests: on the right - performs satisfactorily; on the left - the execution is difficult due to paresis. Controls pelvic functions.

Assessment of the severity of neurological deficits: Test Rivermead Mobility Index: 10/15. Walking test with time and distance registration: distance covered: 215 m; elapsed time: 6 minutes; walking speed: 0.6 m / s; Test Hauser Ambulation Index - 3 points; Bartel's index - 85.

In the study of the cognitive status, emotional and personal sphere with the use of neuropsychological examination, the following were revealed: moderate situational and high personal anxiety; mixed type of attitude towards the disease (obsessive-phobic). Decrease in indicators for the parameters that determine the quality of life (scale SF-36): 1) PF (physical functioning) - 0; 2) RP (influence of physical condition on role functioning (work, performance of everyday activities) - 0; 3) VR (intensity of pain and its effect on the ability to engage in daily activities) - 21; 4) GH (general health) - 40; 5) VT (vitality (implies feeling full of strength and energy or, on the contrary, exhausted) - 30; 6) SF (social functioning) - 12; 7) RE (the influence of an emotional state on role functioning) - 0; 8) MN (self-assessment of mental health, characterizes mood (presence of depression, anxiety, general indicator of positive emotions) - 68; PH (general indicator “Physical component of health”) - 21; MN (general indicator “Physical component of health”) - 31, 56. On the VAS scale, the patient assessed the quality of life at 1 point.

To select an individual program of physical rehabilitation, video analysis of movements during walking was carried out, in accordance with the proposed method. The presence of a combination of criterion characteristics of the kinematic chain of movements of the pelvis and lower extremities during walking for the basin of ischemic lesion of the MCA was established (displacement of the pelvis in the frontal plane by 2.5 ° on the paretic side with reciprocal lowering of the pelvis on the healthy side, excessive internal rotation of the pelvis with predominantly dysfunction of the extensors thigh, plantar flexion failure on both sides).

We used targeted training using robotic mechanotherapy, incl. lessons on a sensory neuropathic pathway with biofeedback, lessons on a stabiloplatform with biofeedback, also lessons with an exercise therapy instructor on targeted programs to improve the function of muscles involved in these motor disorders.

To train the plantar flexion of the foot, a robotic mechanical complex with biofeedback “Contrex” was used in the mode of training plantar flexion in the ankle joint with a gradual increase in the intensity of the load, the session duration was from 10 to 20 minutes.

We also used the following exercises (according to K. B. Petrov, D. M. Ivanchin, Novokuznetsk Institute for Advanced Training of Physicians, Federal Scientific and Practical Center for Medical and Social Expertise and Rehabilitation of the Disabled. Novokuznetsk):

- The patient shifts the center of gravity forward, which contributes to hyperextension of the knee joints and activation of mainly the upper gastrocnemius muscles (jump reflex).

- The patient sits on a chair with his legs crossed "in a European way." The trained leg is on top. By slightly unbending the leg at the knee joint, the patient tries to simultaneously do plantar flexion of the foot.

- The patient sits on a chair, the exercised leg rests on the heel, the knee joint is slightly bent (half bent). By extending the leg at the knee through the lever formed by the heel, the patient achieves passive plantar flexion of the foot. To stimulate plantar flexion, the facilitator strengthens the flexion of the fingers with his hand.

- The patient is on his knees and tilts the torso forward, trying to maintain balance. The methodologist supports the patient for the lower third of the legs. Stabilization of the body is achieved mainly by the ischiocrural muscles, however, the calf muscles are also tense synergistically.

- The patient applies pressure to a spring-loaded pedal or thick foam rubber with the forefoot.

-The patient pedals the exercise bike. The weight of the pedals gradually increases.

- The patient stands facing the wall, resting against it with both palms and chest. One leg is straightened and closed at the knee joint, the trained leg is bent at the knee and the entire plane of the foot rests against the horizontal support. From this position, the patient extends the leg at the knee, trying to passively close it, which contributes to the tension of the gastrocnemius muscle.

- Holding onto the support, the patient rises and falls on the toes. The forefoot can be elevated to increase movement excursions. Shoes should have thick, soft soles.

In parallel, exercises to restore the functions of the upper limbs were also conducted.

On the 15th day of hospitalization, the patient noted an improvement in general health, mood; in addition, the volume of active movements in the paretic limbs expanded, the muscle strength increased in the hand to 4 points; in the proximal part of the leg up to 3.5 points, in the distal parts up to 4 points; the indicators of walking walking improved, the speed and pace of movement increased. Rivermead Mobility Index test 13/15. Walking test with registration of time and distance: distance covered: 340 m; elapsed time: 6 min. Walking speed: 0.74 m / s; Hauser Walking Index test - 4 points; Bartel's index - 100; life quality assessment according to the YOUR scale - 5 points

In addition, the patient's anxiety-phobic features were smoothed out. The study of the quality of life using the SF-36 test revealed a significant improvement in terms of indicators: "physical functioning" (40 points), "general health" (70 points), "vitality" (65 points), "social functioning" (38 b.), "emotional role" (33 p.), "physical component of health" (31 p.), "mental health component" (42 p.).

Decreased the search time for numbers in Schulte tables; the number of associations (nouns) cited by the patient increased in 1 min, the indicators of attention and conceptualization according to the Montreal scale improved. The stabilographic indicators have improved. According to the control video analysis of walking movements, the criterion characteristics of the kinematic chain of pelvic and lower limb movements are close to normal values.

Clinical example 2.

Patient N., 56 years old, was undergoing rehabilitation with a diagnosis of ischemic stroke in the vertebrobasilar basin (early recovery period), atherothrombotic pathogenetic subtype. Moderately pronounced atactic syndrome.

Upon admission, the condition is satisfactory. BP 130/80 mm Hg. Heart rate 76 beats per minute. NPV 17 per minute. The heart sounds are muffled, the rhythm is correct.

Neurological status: conscious, in contact. There are no meningeal signs. FMN: palpebral fissures d> = s. Positioning horizontal nystagmus in the extreme abduction of the eyeballs. Photoreactions are saved. The reaction to convergence and accommodation is reduced. Smoothness of the left nasolabial fold. There are no bulbar violations. Tongue in the midline. The range of active and passive movements is not limited. The tone is not changed. Left-sided hemiparesis up to 4 points. Periosteal and tendon reflexes d <= s, medium liveliness. There are no pathological signs. Coordination tests: PNP - with a short hit on the left, EPP - with ataxia on the left. Dysdiadochokinesis. Not stable in the Romberg position.

When conducting a video analysis of the patient's gait movements, criterion signs of ischemic lesion in the IHD basin were revealed (forward tilt of the pelvis (displacement of the center of mass in the sagittal plane while maintaining the position in the frontal plane), impaired flexion-extension in the hip joint when walking, and plantar flexion failure.

The patient was trained on a stabilometric platform for 5 minutes, the training test "Target" was performed, 3 sessions. Then the execution time of the training test "Target" was increased at each lesson by 2 minutes, bringing it to 20 minutes.

After exercising on a stabilometric platform, the patient rested for 10 minutes. Then, after monitoring the patient's condition, targeted exercises for training dynamic balance, exercises for stabilizing the center of mass in the sagittal plane began.

To train plantar flexion in parallel, after exercise on a stabilometric platform and a short break, the techniques described in Example 1 were used.

Against the background of the treatment, there was a positive trend: the severity of dizziness decreased, the patient became more active, the accuracy of the coordination tests and the stability when walking increased. Also, there was a positive dynamics of indicators according to the scale for assessing balance in a standing position (R. Bohannon, 1989) from 0 points to 2 points; scales of functional mobility when walking (Perry J. et al., 1995) from 0 to 2 points; scales for assessing walking disorders (Stolyarova L.G. et al., 1982) from 4 to 2 points; Spielberger-Hanin anxiety and depression from 43 to 34 points. The criterion indicators determined by video analysis of gait movements improved significantly.

When observed after 3, 6 months, the patient's condition remained stable. No deterioration was noted. 6 months after the repeated course of rehabilitation, the mentioned criterion indicators approach the normative ones.

It was statistically significant that among patients of the corresponding groups with one or another localization of stroke (in the MCA or VHD basin), a faster recovery of the walking pattern, a decrease in the manifestations of the severity of central paresis was observed in patients who received a targeted differentiated rehabilitation program, built taking into account changes in kinematic parameters. the motor pattern and functions of certain muscle groups depending on the localization of the IS pool, according to our method, in comparison with patients who received the generally accepted standard rehabilitation program, drawn up without interconnection with the stroke localization pool and the criterion indicators of disorders we identified.

The recovery time of patients' gait parameters when using the proposed method was reduced by about 30%, since targeted targeted exercises were used that corrected certain kinematic indicators, directly affecting key muscle groups and stimulating specified neuronal connections, while other disorders were leveled in the kinematic chain of movement indirectly and gradually, following the key links of the motor pattern.

In addition, as shown by repeated studies using valid clinical tests listed above, the acceleration of the rehabilitation period and an increase in its effectiveness had a significant positive effect on the general condition of patients (a decrease in general fatigue and an increase in patient endurance, a decrease in anxiety and depression according to the corresponding scales) , since it led to faster and more complete socialization, restored vitality, and increased patient satisfaction with treatment.

Consequently, a targeted differentiated approach to rehabilitation, depending on the reservoir of IS localization, makes it possible to increase the effectiveness of rehabilitation, productivity and accelerate the recovery processes of motion control after AI. At the same time, the preparation of individual training programs for the restoration of the walking pattern in the early recovery period of IS should be carried out taking into account the criterion signs that we identified that are specific to the stroke pool, used in the formulation of a rehabilitation diagnosis according to the International Classification of Functioning (ICF, ICF), determination of the rehabilitation potential, as well as for the selection of individually directed target methods of physical rehabilitation for the restoration of the motor pattern, depending on the ACVA pool, improving the target control of the work of certain muscle groups, impaired in stroke in the corresponding vascular pool.

Claims (10)

A method of using a virtual digital model of a patient's gait for the differentiated construction of an individual physical rehabilitation program (IPFR) in the early recovery period of ischemic stroke (IS), depending on the area of the lesion, where, to construct an IPFR, including the selection of physical exercises, specific kinematic parameters of walking are taken into account, determined depending on the AI pool according to a virtual digital model of the patient's walking, obtained during 3D video analysis of movements using a high-resolution digital optical-electronic system SMART-D, equipped with cameras with high-resolution matrices with a motion scanning frequency of up to 100 Hz per second, followed by animation and graphic construction of a virtual motion model; at the same time, as the kinematic parameters of the motor pattern for the characteristics of the virtual digital model of the patient's gait with IS in the vertebrobasilar system (VBS) take the presence of a combination of the following signs that require correction: - the forward tilt of the pelvis in the sagittal plane during the phase of support and transfer, with a corresponding displacement of the center of mass, with an angle of displacement of the pelvis anteriorly - more than 10 ° from the average standard indicator of 7 °, in the absence of deviations of the pelvis from the standard indicators in the frontal plane, - on the paretic and healthy side - increased flexion in the hip joint (HJ) in the transfer phase with insufficient extension in the support phase by more than 10 ° in comparison with the upper limit of the standard indicator given in table 1 in the description, - insufficiency of plantar flexion of the paretic and healthy side during the support-transfer period; and as the kinematic parameters of the motor pattern to characterize the virtual digital model of the patient's walking with IS in the middle cerebral artery (MCA) basin, the presence of a combination of the following features requiring correction is taken: - displacement of the pelvis in the frontal plane with an elevation of the pelvis on the paresis side by more than 1.5 ° compared to the standard indicator in the transfer phase with the corresponding reciprocal lowering of the pelvis on the healthy side, in the absence of pathological displacement of the center of mass in the sagittal plane, - excessive internal rotation in the hip joint in the horizontal plane on both sides during the entire cycle of the stride compared to the normative indicator, with impaired flexion and extension functions, with predominantly pronounced impairment of the functions of the hip extensor muscles on the side of paresis, - lack of plantar flexion on the paretic and healthy side during the support-transfer period.

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