GB2631591A

GB2631591A - Shoulder arthroplasty method and apparatus

Info

Publication number: GB2631591A
Application number: GB2408691.0A
Authority: GB
Inventors: Monga Puneet
Original assignee: Wrightington Wigan & Leigh Teaching Hospitals Nhs Found Trust
Current assignee: Wrightington Wigan & Leigh Teaching Hospitals Nhs Found Trust
Priority date: 2023-06-15
Filing date: 2024-06-17
Publication date: 2025-01-08
Also published as: GB202408691D0

Abstract

Method and apparatus for calculating the optimal position and/or axis for wire insertion on the Glenoid Face through the Glenoid Vault. The first step is defining the scapular body plane 12 using reference points away from the Glenoid Face. The reference points including the Trigonum Spinae and/or one or more points on the lateral border of the scapular body. A transverse plane 14 is then defined, or a plane transverse to the scapular body plane. The transverse plane transecting the scapular body plane at the trigonum spine medially. The lateral transection of this transverse plane is through the centre of the glenoid face, and wherein the glenoid axis and thereby the optimal position and/or axis for wire insertion on the Glenoid Face through the Glenoid Vault is defined in the absence or presence of Glenoid Face deformities. A reference point may be form the inferior glenoid tubercle.

Description

Shoulder Arthroplasty Method and Apparatus The present invention relates to an apparatus and method for conducting shoulder arthroplasty and in particular replacing the articulating surface of the Glenoid.

As with all joint replacements correct alignment of the implanted prosthesis is essential to ensure correct functioning and reduce the risk of failure over time.

Shoulder replacement often involves replacement of the ball shaped upper end of the arm bone (humerus) and replacement of the socket shaped part of the shoulder blade (scapula). The socket is the far end (lateral aspect) of the scapula and is called the glenoid. In the human shoulder joint, the socket is relatively small compared to the larger ball and such an arrangement allows humans to have a large range of movement of the shoulder joint. In contrast, the hip joint has a much deeper socket compared to the ball, which gives it higher stability at the cost of reduced range of motion.

When the shoulder joint is damaged from problems such as arthritis or injury, the patients may present with severe pain and disability and a shoulder replacement may be advised. When performing a shoulder replacement, it is of paramount importance that the new components are placed precisely and accurately. This produces unique challenges. It is often the case that the glenoid shape has changed due to the problem. Also, the glenoid itself is a deeply placed structure and access to it for a surgeon is often technically demanding. One can see how the relatively small size of the glenoid, limited access and bone deformities can combine to create a challenge in the precise placement of a shoulder replacement component.

One of a surgeons' first tasks for placement of a shoulder replacement component is to expose the articular (joint forming) surface of the glenoid; the "Glenoid Face" as shown in Figure 1. The bone surface is then prepared to accept the replacement (Figure 2). A wire is placed through the Glenoid Face into the bone immediately behind it, known as the "Glenoid Vault" along an appropriate axis to define the alignment of this component. This first step of axis selection and wire placement is the most crucial, as it determines the rest of the steps following it. In other words, imprecise placement of the wire will translate into an imprecise placement of the final implant. It is indeed the foundation over which the rest of the surgery, and indeed the outcomes, are reliant.

One can imagine that in the presence of deformities (which is often the case when a joint is being replaced), the reference surface of the Glenoid Face is unreliable. Ilence the wire placement is often based on an estimate relying heavily on the surgeon's experience. To circumvent the inaccuracies inherent in estimation or 'eye-balling', more recently several technologies to support surgeons have been developed utilizing custom made guides or with intra-operative guidance using infrared / radio-wave based positioning systems.

The custom-made guides rely on digital pre-operative planning for their production which is generally by all printing. The guides have a central channel which allows a predetermined entry point of the guide wire on the Glenoid Face with an appropriate axis through the remainder of the glenoid. In contrast, the intra-operative positioning systems allow 'live' guidance during surgery for wire positioning along a predefined 'virtual' axis, which the surgeon has defined using pre-operative CT scans. Intraoperative guidance is reliant on placement of marker pins through the coracoid, which on movement may lead to errors. The current markers also need to rely on "line of sight" orientation between the sensors and the computing station, making them cumbersome to use.

The technology of 3D printed guides / guidance systems offer a solution of being able to perform wire placement as per preoperative planning. There are, however, challenges commonly encountered with both these available techniques. One challenge is the estimation of the optimal point of entry for the guide wire on the Glenoid Face. This is a particular problem when the Glenoid Face itself is deformed. The current descriptions rely on the "normal" Glenoid Face and the entry point is based on the center of the best fit circle on the Glenoid Face. There is currently no reliable methodology available to define where the optimal axis exists in three-dimensional planes when the glenoid face is deformed. In other words there is currently no standard accepted definition of the 3 Dimensional glcnoid axis in the presence of a Glenoid Face deformity. This is paradoxical as the need for the guidance is greatest when the glenoid face is deformed! The second practical issue often faced by surgeons using currently available custom-made guides is that they are extremely bulky, flexible or made of modular parts. As the access to the glenoid is very limited, such an unwieldy device may lead to errors in wire placement.

The currently available guides may also not have enough stability during usage. They are often designed by the surgeon themselves on software platforms and allow the user to define where the relatively narrow feet of the guides sit. These feet often sit on the edge/ rim of the Glenoid Face and may not be mechanically stable during surgery.

In addition, the currently available guides rely on a limited number of (3 or 4) strategically placed feet. Any changes on the shape of the bone or inaccurate removal of soft tissues under these "feet" can mis-align the guide, hence affect their precision.

It is therefore an aim of the invention to provide a method of calculating the optimal (a) position and (b) axis for wire insertion on the Glenoid Face and through the Glenoid Vault for shoulder arthroplasty that addresses the aforementioned problems.

It is a further aim of the present invention to provide a guide that facilitates both locating and drilling at the optimal (a) position and (b) axis for wire insertion on the Glenoid Face and through the Glenoid Vault during shoulder arthroplasty that addresses the above-mentioned problems.

It is a further aim of the present invention to provide a patient specific glenoid guide system suitable for use in shoulder arthroplasty that addresses the abovementioned problems.

In a first aspect of the invention there is provided a method of calculating the optimal position and/or axis for wire insertion on the Glenoid Face through the Glenoid Vault, said method including; the first step of defining the scapular body plane using reference points away from the Glenoid Face, said reference points including the Trigonum Spinae and/or one or more points on the lateral border of the scapular body, a transverse plane is then defined, or a plane transverse to the scapular body plane, said transverse plane transecting the scapular body plane at the trigonum spine medially, wherein the lateral transection of this transverse plane is through the center of the glenoid face, and wherein the glenoid axis and thereby the optimal position and/or axis for wire insertion on the Glenoid Face through the Glenoid Vault is defined in the absence or presence of Glenoid Face deformities..

In a preferred embodiment three points define the scapular body 5 plane. Further typically the scapular body plane is defined by two points on the lateral border of the scapular body and one on the Trigonum Spinae Typically the lateral transection of the transverse plane is through 10 the center of the glenoid face in a non-deformed glenoid.

Tn one embodiment, the point or reference point on the glenoid face is at the center of the glenoid vault and/or 15mm above the infra-glenoid tubercle. Typically this is where a glenoid deformity is present.

Further typically the infra-glenoid tubercle as a reference point is maintained even in severe arthritis, which often affects the superior and posterior aspect (and occasionally the anterior 20 aspect) of the Glcnoid Face.

In one embodiment, for additional confirmation in cases of severe deformity, the calculation can reference a section view transversely through the proposed axis.

In one embodiment, in the case of advanced erosion of the glenoid, where the landmarks on the glenoid face and glenoid vault are also eroded, the method includes the step of using a reference point or landmark from the inferior glenoid tubercle as this is not usually involved in the arthritic process.

Typically the vertical dimension of the glenoid is 25 to 40 mm and the transverse plane passes '12.5mm to 20mm superior to the inferior glenoid tubercle. This measurement is applicable in the setting of an anatomical total shoulder replacement.

In one embodiment, for reverse shoulder replacement, the axis is defined by the desire to place the glenoid base plate in a position where it aligns with the inferior border of the glenoid face. The transverse plane passes 12.5mm to 1 5rrim superior to inferior glenoid tubercle in this scenario. The Transverse plane would pass through the trigonum spinae medially in all scenarios as it is away from the arthritic process.

Tn a second aspect of the invention there is provided a glenoid guide apparatus, said guide apparatus does not rely on the glenoid surface for its design or configuration, but on external landmarks, wherein at least part of the guide apparatus is configured and/or adapted to reference, receive and/or conform to the shape of the anterior rim of the glenoid.

Typically this reference or conformity allows precise placement 20 under average surgical conditions without the need for extra surgical exposure.

In one embodiment at least part of the guide apparatus is configured and/or adapted to reference, receive and/or conform 25 to the inferior surface of the base of the coracoid.

Typically the inferior surface of the base of the coracoid is not deformed even in the worst deformities affecting the shoulder joint. The guide can hence be used in cases with severe 30 deformities.

In one embodiment at least part of the guide apparatus is configured and/or adapted to reference, receive and/or conform to the surface of the Glen° d Face.'Typically this provides a number of contact points.

Typically the guide is not subject to errors related to changes in 5 the shape of the bone or inadequate removal of soft tissues, from under the feet of limited contact guides.

Further typically the guide comprises or consists of a single material.

In one embodiment the guide is made of a mono block material preventing disassembly during usage.

In one embodiment the guide apparatus is "arrow" shape in overall profile. Typically the narrow part of the arrow is placed in the posterior part of the glenoid. This shape, and hence ease of usage, allows precise placement.

In a preferred embodiment the guide apparatus includes two or more members or outriggers. Typically the members or outriggers have one or more spaces therebetween and do not completely covering the glenoid and thereby allow the surgeon to visually confirm precise placement of the guide, and at the same time providing stability.

Further typically the guide apparatus includes a plurality of members or outriggers that extend out from substantially the central part or axis of the guide apparatus.

In one embodiment the guides or outriggers extend radially from the center or centrally axis of the guide.

In one embodiment the guide apparatus includes 3-8 members or outriggers.

Typically the members or outriggers are substantially linear.

In one embodiment the guide apparatus includes 4-7 members or outriggers, preferably six outriggers.

In one embodiment the guide apparatus includes at least one drilling channel. Typically the drilling channel is an aperture configured or adapted to lie on or along the optimal position and/or axis for wire insertion. Further typically in use the drilling channel is configured the receive and guide a drill bit on and/or along the optimal position and/or axis for wire insertion.

Preferably the drilling channel ends and/or is a spaced distance 15 from the Glenoid Face.

In one embodiment the drilling channel of the guide ends adjacent the Glenoid Face. Typically the drilling channel exit aperture is 0.1-1.0 mm from the Glenoid Face. Further typically the channel terminates or ends 0.6mm from the Glenoid Face. hence minimising any deflection from occurring between the guide and the bone.

In one embodiment the guide apparatus includes a handle portion. 25 Typically the handle portion extends from a body portion. Further typically the body portion includes the at least one drilling channel apperture.

In one embodiment the handle portion extends at an angle or 30 direction different to the longitudinal or central axis of the drilling channel or aperture.

In one embodiment the handle portion is arcuare in cross section.

In one embodiment the members or outriggers extend from the body portion.

In a third aspect of the invention there is provided a method of creating a patient specific drilling guide and/or axis for wire insertion on the Glenoid Face for shoulder arthroplasty, said method including the step of; creating a plane comprising at least three points or landmarks, said points or landmarks including at least two points or landmarks using lateral border of the scapular body and at least one point using the Trigonum Spinae.

Tn a further aspect of the invention there is provided a drilling guide apparatus or device, said apparatus including a receiving portion adapted to receive, abut and/or attach to at least part of the anterior border of the Glenoid and a guide portion or aperture adapted to guide a drill or drill bit into the Glenoid surface along and/or substantially on the axis for wire insertion.

Specific embodiments of the invention are now described with reference to the following figures, wherein: Figure 1 shows the anatomy of the scapula and location of the Glenoid; Figure 2 shows a shoulder replacement implant replacing the surface of the Glenoid; Figures 3, 4, and 5 show the calculated scapular body plane using 30 two points in the lateral border of the scapula and one point on the Trigonum spinae; Figure 6 shows the determination of the transverse plane, transecting the scapular body plane at the Trigonum spinae; and Figure 7A-7K shows a guide constructed in accordance with an embodiment of the invention.

The current invention provides a method of calculating the optimal (i) position and (ii) axis for wire insertion on the Glenoid Face 2 through the Glenoid Vault 4, which would be applicable, even in the presence of a glenoid deformity. The first step in calculating such an axis is by defining the scapular plane using reference points away from the Glenoid Face 2. The Trigonum Spinae 6 and the lateral border 8 of the scapular body 10 are used to define a plane 12 (Figure 3, 4, 5). In other words, three points define the Scapular body plane; two on the lateral border 8 of the scapular body 10 and one on the Trigonum spinae 6 medially. The Transverse plane 14 is then described perpendicular to the scapular body plane, transecting it at the trigonum spine medially (Figure 6). The lateral transaction of this transverse plane is through the center of the glenoid face 2 in an undeformed glenoid. In the presence of glenoid deformity such reference point is sought at the center of the glenoid vault or 15mm above the infra-glenoid tubercle. This infraglenoid tubercle as a reference point is maintained even in severe arthritis, which often affect the superior and posterior aspect (and occasionally the anterior aspect) of the Glenoid Face. Hence one is able to define the glenoid axis in the absence or presence of Glenoid Face deformities. Igor additional confirmation in cases of severe deformity, the calculation can reference a section view transversely through the proposed axis.

In case of advanced erosion of the glenoid, where the landmarks on the glenoid face and glenoid vault are also eroded, one would reference off the inferior glenoid tubercle as a landmark as this is not usually involved in the arthritic process. The vertical dimension of the glenoid is 25 to 40mm (Reference) and the transverse plane would hence pass 12.5mm to 20mm superior to the inferior glenoid tubercle. This measurement is applicable in the setting of an anatomical total shoulder replacement. For reverse shoulder replacement the axis is defined by the desire to place the glcnoid base plate in a position where is aligns with the inferior border of the glenoid face. The transverse plane would pass 12.5mm to 15mm superior to inferior glenoid tubercle in this scenario. The Transverse plane would pass through the trigonum spinae medially in all scenarios as it is away for the arthritic process.

The second aspect of the invention, relates to the unique shape of the glcnoid guide. We describe some unique features incorporated within the guide, in combination or individually with reference to figure 7 A-K.

1. The guide design does not rely on the glcnoid surface 2 for its design, but on external landmarks.

2. The guide references to the shape of the anterior rim 16 of the glenoid, which is often the easier areas of the Glenoid Face for the surgeons to access. This allows precise placement under average surgical conditions without the need for extra surgical exposure.

3. The guide references to the inferior surface of the base of the coracoid which is not deformed even in the worst deformities affecting the shoulder joint. The guide can hence be used in cases with severe deformities.

4. The guide references the surface of the Glenoid Face providing an infinite number of contact points in contrast to currently available custom guides which utilise 3 or 4 reference points.

The guide is hence not subject to errors related to changes in the shape of the bone or inadequate removal of soft tissues, from under the feet of limited contact guides.

5. The guide is made of a mono block material preventing disassembly during usage.

6. The shape of the guide is "arrow" shape in overall profile. The narrow part of this arrow is placed in the posterior part of the glenoid, which is more challenging to access for surgeons. This shape, and hence ease of usage, allows precise placement.

7. Rather than a negative imprint of the Glenoid Face 2 which covers the glenoid completely, the guide has here are six outriggers 20 from the central part of the guide. The purpose of this shape is to allow the surgeon to visually confirm precise placement of the guide, and at the same time providing stability.

8. The drilling channel of the guide ends immediately adjacent (0.6mm) from the Glenoid lace, hence minimising any deflection from occurring between the guide and the bone.

Claims

Claims 1. A method of calculating the optimal position and/or axis for wire insertion on the Glenoid Pace through the Glenoid Vault, 5 said method including; the first step of defining the scapular body plane using reference points away from the Glenoid Face, said reference points including the Trigonum Spinac and/or one or more points on the lateral border of the scapular body, a transverse plane is then defined, or a plane transverse to the scapular body plane, said transverse plane transecting the scapular body plane at the trigonum spine medially, wherein the lateral transaction of this transverse plane is through the center of the glenoid face, and wherein the glenoid axis and thereby the optimal position and/or axis for wire insertion on the Glenoid Face through the Glenoid Vault is defined in the absence or presence of Glenoid Face deformities.
2. A method according to claim 1 wherein at least three points 20 define the scapular body plane.
3. A method according to claim 1 wherein the scapular body plane is defined by two points on the lateral border of the scapular body and one on the Trigonum Spinae medially.
4. A method according to any preceding claim wherein the lateral transection of the transverse plane is through the center of the glenoid face in a non-deformed glenoid.
5. A method according to claims 1-3 wherein the point or reference point on the glenoid face is at the center of the glenoid vault and/or 15mm above the infra-glenoid tubercle.
6. A method according to claim 5 wherein the infra-glenoid tubercle as a reference point is maintained even in the presence of Glenoid lace deformities.
7. A method according to claims 1-3 wherein the method includes reference to a section view transversely through the proposed axis.
8. A method according to claim 1-3 wherein the method includes 10 the step of using a reference point or landmark from the inferior glenoid tubercle.
9. A method according to any preceding claim wherein the vertical dimension of the glenoid is 25 to 40 mm and the 15 transverse plane passes 12.5mm to 20mm superior to the inferior glenoid tubercle.
10. A method according to claim 9 wherein he transverse plane passes 12.5mm to 15mm superior to inferior glenoid tubercle. 20
11. A glenoid guide apparatus wherein at least part of the guide apparatus is configured and/or adapted to reference, receive and/or conform to the shape of the anterior rim of the glenoid, and at least part of the apparatus is configured the receive and guide a drill bit on and/or along the optimal position and/or axis for wire insertion calculated in claim 1.
12. A glenoid guide apparatus according to claim 11 wherein at least part of the guide apparatus is configured and/or adapted to 30 reference, receive and/or conform to the inferior surface of the base of the coracoid.
13. A glenoid guide apparatus according to claim 12 wherein at least part of the guide apparatus is configured and/or adapted to reference, receive and/or conform to the surface of the Glenoid Face.
14. A glenoid guide apparatus according to claims 11-13 wherein the guide comprises or consists of a single material.
15. A glenoid guide apparatus according to claims 11-14 wherein the guide apparatus includes two or more members or outriggers have one or more spaces therebetween and thereby do not completely cover the glenoid and allow visual confirmation of placement of the guide.
16. A glenoid guide apparatus according to claim 15 wherein a 15 plurality of members or outriggers that extend out from substantially the central part or axis of the guide apparatus.
17. A glenoid guide apparatus according to claim 11 wherein the members or outriggers are substantially linear and extend radially 20 from the center or centrally axis of the guide.
18. A glenoid guide apparatus according to claims 11-17 wherein the guide apparatus includes at least one drilling channel, the drilling channel being an aperture configured or adapted to lie on 25 or along the optimal position and/or axis for wire insertion.
19. A glenoid guide apparatus according to claim 18 wherein the drilling channel ends and/or is a spaced distance from the Glenoid lace.
20. A glenoid guide apparatus according to claim 18 wherein the drilling channel of the guide ends adjacent the Glenoid Face.
21. A glenoid guide apparatus according to claims 11-20 wherein the guide apparatus includes a handle portion extending from a body portion that includes the at least one drilling channel apperture.
22. A glenoid guide apparatus according to claim 21 wherein the handle portion extends at an angle or direction different to the longitudinal or central axis of the drilling channel or aperture.
23. A glenoid guide apparatus according to claim 22 wherein the handle portion is arcuate in cross section.
24. A glcnoid guide apparatus according to claims 15-23 wherein the members or outriggers extend from the body portion.