WO2025204077A1 - Tracker device - Google Patents

Abstract

The purpose of the present invention is to provide a tracker device which is less invasive to a patient, is excellent in safety, can be firmly fixed to the pelvis of the patient, can be easily removed after surgery, and is less invasive to the skin and bone after removal. This tracker device constitutes a navigation system used when performing orthopedic surgery, and comprises: a tracker unit (110) having optical markers (111)-(114); and a fixing member (120) for fixing the tracker unit (110) to the pelvis of a patient. The fixing member (120) comprises a spiral coil having a pointed end (121).

Description

Tracker Device

The present invention relates to a tracker device, particularly a bone tracker device, that is part of a navigation system or robotic system used in performing orthopedic surgery.

Conventionally, for example, in total hip replacement surgery, navigation systems and robotic systems have been proposed that assist in guiding and inserting an acetabular cup into the patient's acetabulum in the ideal position and direction (see Patent Document 1 below).

The navigation system includes a stereo camera equipped with a near-infrared light-emitting unit, a pelvis tracker unit fixed to the patient's pelvis, a registration tracker unit placed at a landmark or reference position on the pelvis, a tracker unit connected to the acetabulum cutting tool, and a femur tracker unit connected to the patient's femur.

Each of these tracker units is equipped with multiple or single reflective or self-luminous markers, and by photographing these tracker units with a stereo camera and measuring the position of each individual tracker using the principles of trigonometry, the relative positional relationships between the tracker units can be obtained.

After the positional relationship determined in this way is registered in the computing device, the positional relationship between the pelvic tracker unit and the tracker unit connected to the acetabular cutting tool can be continuously measured (tracked) to grasp changes in the relative position of the acetabular insertion tool with respect to the patient's pelvis (changes associated with body movement and/or tool movement). As a result, in total hip replacement surgery, an implant called an acetabular cup can be placed in the correct pelvic position with the desired lateral and anteversion angles.

JP 2014-508549 A

The pelvis tracker unit with markers is typically secured to the patient's pelvis using pins or bone screws as fixation members.
Specifically, the procedure involves first drilling a pilot hole through an incision in the skin into a region of the pelvis called the iliac crest using an electric drill, and then inserting a bone screw while self-tapping.

However, in a structure in which the marker section and the bone tracker unit are separated, the fixation member made of a bone screw that attaches the tracker section does not necessarily have sufficient resistance to pull-out when it is embedded in the pelvis (cancellous portion), and there is a problem that the tracker section may come out of the pelvis or the screw section may loosen, causing the tracker section to wobble and reducing positional accuracy. This loosening is particularly likely to occur when the patient changes position during surgery, and this is the most troublesome issue for uses that require high accuracy and precision in implant placement.
Furthermore, because pins or bone screws, usually with an outer diameter of 4 to 6 mm or more, are inserted through an incision larger than several millimeters, scars (suture marks) remain on the skin after surgery in addition to the incision made for implant placement. Furthermore, holes remain in the pelvis after the bone screws are removed, which take time to close.

Furthermore, the invasiveness of such fixation methods to the patient can be extremely dangerous.
There have been reported cases where the direction of the electric drill deviated when drilling pilot holes, causing damage to the pelvis or blood vessels (H. Kan, I. Nusem/Arthroplasty Today 19(2023)101070). Therefore, there are limitations to solving the problem by increasing the number of bone screws or increasing their diameter from the perspective of patient safety.

The present invention has been made based on the above circumstances.
The object of the present invention is to provide a tracker device that is minimally invasive to the patient, highly safe, can be firmly fixed to the patient's pelvis, can be easily removed after surgery, leaves small scars on the skin after removal, and is minimally invasive to the bones.

The tracker device of the present invention is a part of a navigation system used when performing orthopedic surgery, and is characterized in that it comprises a tracker unit having at least one optical marker and a fixation member for fixing the tracker unit to the patient's bone, the fixation member being a helical coil having a pointed end.

In the tracker device of the present invention, it is preferable that the spiral coil is formed from a wire having a circular cross section, the diameter (d) of the wire being 1.2 to 3.0 mm, the coil diameter (D) being 2.8 to 12 mm, the coil pitch (p) being 2.4 to 30 mm, and the coil length (L) being 8 to 140 mm.
In this case, it is particularly preferable that the ratio of the coil diameter to the wire diameter (D/d) is 1.5 to 5, and the coil pitch to the wire diameter (p/d) is 1.35 to 6.

In the tracker device of the present invention, it is preferable that the spiral coil is formed from wire having a polygonal cross section, such as a circle, semicircle, ellipse, triangle, quadrangle (square, rhombus, rectangle, trapezoid, etc.), pentagon, or hexagon.
However, these wires tend to twist around their central axis when formed into a spiral coil. This twisting can widen the entrance or penetration path when screwing the coil body into the bone, loosening the fixation of the spiral coil to the pelvis, etc. Therefore, a circular or polygonal shape is desirable for the wire.

In the tracker device of the present invention, if the tip of the spiral coil is machined with a cutting edge, it is preferable because there is no need to drill a pilot hole when penetrating the cortical bone on the bone surface.

It is also preferable that the fixing member is detachable from the tracker unit.
It is also preferable that the tracker unit has at least one light-reflecting or light-emitting marker.
The tracker unit may also have a two-dimensional tracker on which optically readable information (image information such as a two-dimensional matrix) is printed.

The tracker device of the present invention is preferably used for fixation to a patient's bones when performing a total joint replacement procedure.
For example, it may be suitably used for fixation to a patient's pelvis or femur when performing a total hip replacement surgery.
It is also suitable for use in fixing to the patient's femur or tibia when performing total knee replacement surgery.
It can also be suitably used for fixing to the necessary bones of a patient when performing other artificial joint replacement procedures (for example, shoulder joint replacement).
However, the tracker device is not limited to use in joint replacement surgery, but can also be used in other surgeries requiring precise navigation, such as pelvic fracture repair.

According to the tracker device of the present invention, the fixing member is composed of a helical coil with a pointed end (preferably with a sharp cutting edge), which makes it easy to attach and detach the tracker device from the patient's bone (pelvis).In addition, the tracker device can be attached by hand without using an electric drill or the like, and the depth can be adjusted slowly, making it very safe.
The tracker device of the present invention is firmly fixed to the bone and has extremely high resistance to being pulled out or loosened. It can also be removed manually.

Furthermore, any scars remaining on the skin after removing the tracker device of the present invention are caused by the penetration of the wire of the spiral coil (holes equivalent in diameter to the diameter of the wire), and are significantly smaller than those left when pins or bone screws are used, so in most cases no suturing is required. Furthermore, because only a small amount of bone tissue is removed when the spiral coil is implanted into the bone, the hole left in the bone after the fixation member (spiral coil) is removed is also small. Consequently, use of the tracker device of the present invention is extremely minimally invasive to the patient.

FIG. 1 is a front view showing a tracker device according to a first embodiment of the present invention. FIG. 1 is a side view showing a tracker device of a first embodiment. FIG. 2 is a cross-sectional view of a fixing member that constitutes the tracker device of the first embodiment. FIG. 10 is a front view showing a tracker device according to a second embodiment of the present invention. FIG. 10 is a cross-sectional view of a fixing member constituting a tracker device of a second embodiment. FIG. 10 is a front view showing a tracker device according to a third embodiment of the present invention. FIG. 10 is a front view showing a tracker device according to a fourth embodiment of the present invention.

First Embodiment
The tracker device 100 of this embodiment shown in FIGS. 1A to 1C is a tracker device that constitutes a navigation system used in performing total hip replacement surgery, and is fixed to the patient's pelvis.

The tracker device 100 includes a tracker unit 110 and a fixing member 120.
During a hip replacement surgery, the tracker unit 110 is positioned outside the patient's body, and the fixation member 120 has its distal side implanted in the pelvis and its proximal side located outside the body.

The tracker unit 110 that makes up the tracker device 100 has four reflective markers (tracking targets) 111-114, which are near-infrared reflective ball markers.

A fixing member 120 is detachably attached to the distal end of the tracker unit 110. The mechanism for attaching and detaching the fixing member 120 is not particularly limited, and an example of such a mechanism is a locking mechanism such as a screw.
The fixation member 120 that makes up the tracker device 100 consists of a helical coil with a tip 121 at its distal end.

The fixing member 120, which consists of a spiral coil, is formed from wire (round wire) with a circular cross section, and the tip 121 of the fixing member 120 is approximately conical or approximately truncated conical (the apex of the truncated cone may be rounded).

The fixing member 120 can be made of metals such as stainless steel, Ni-Ti alloy, Co-Cr alloy, or tantalum, or these materials coated with low-friction resin.

The diameter d of the wire forming the fixing member 120 is preferably 1.2 to 3.0 mm, and more preferably 1.8 to 2.5 mm.
If the wire diameter d is too small, it becomes difficult to form a fixation member with high pull-out strength, whereas if the wire diameter d is too large, the objectives of the present invention, namely, minimal invasiveness and minimal scarring, cannot be fully achieved.

The outer diameter (coil diameter) D of the fixing member 120 is preferably generally 2.8 to 12 mm, and more preferably 5 to 10 mm.

Here, the ratio (D/d) of the coil diameter D to the wire diameter d is preferably 1.5 to 5.
A fixation member with an excessively small ratio (D/d) cannot exhibit sufficient pull-out strength, whereas a fixation member with an excessively large ratio (D/d) is difficult to embed in bone (attach the tracker device) and remove from bone (remove the tracker device).

The pitch (coil pitch) p of the fixing member 120 is preferably 2.4 to 30 mm.

The ratio (p/d) of the coil pitch p to the wire diameter d is preferably 1.35 to 6.
A fixation member with an excessively small ratio (p/d) (tightly wound) cannot fully achieve the goal of minimal invasiveness, while a fixation member with an excessively large ratio (p/d) (loosely wound) cannot exhibit sufficient pull-out strength.

The length (coil length) L of the fixing member 120 is preferably 8 to 140 mm to ensure sufficient pull-out resistance.

Prior to performing a hip replacement surgery, the tracker device 100 of this embodiment is attached to the patient's pelvis.
Specifically, the tip 121 of the fixing member 120 is brought into contact with the patient's skin covering the pelvis (the attachment site of the device), and the fixing member 120 is rotated about its axis, in this example clockwise, to introduce the tip 121 into the body until it reaches the pelvis. If necessary, the tip provided at the tip is set perpendicular to the cortical bone and twisted to penetrate it. Then, by continuing to rotate further in the direction along its original spiral shape, the fixing member 120 advances spirally and is embedded in the pelvis. This allows the tracker device 100 to be attached to the patient's pelvis.

Here, the operation of embedding the fixing member 120 into the pelvis to attach the tracker device 100 may be performed with the tracker unit 110 attached to the fixing member 120, but it is also possible to first remove the fixing member 120 from the tracker unit 110, and then embed the removed fixing member 120 into the pelvis using a jig such as a T-shaped handle, and then attach the tracker unit 110 to the proximal end of the fixing member 120 extending from the skin.

The reflective markers 111 to 114 provided on the tracker unit 110 can be photographed (recognized) by an infrared camera that constitutes the navigation system.
Here, the "position of tracker unit 110 on the patient's pelvis" can be determined by placing registered trackers equipped with reflective markers similar to reflective markers 111 to 114 at multiple landmarks or reference positions on the pelvis (e.g., the anterior superior iliac spine, the anterior inferior iliac spine, and the iliac crest), photographing them with an infrared camera, and measuring the relative positional relationship between each registered tracker and tracker unit 110.
The "position of the tracker unit 110 on the patient's pelvis" determined in this manner is registered in the navigation system computer, and by tracking the position (changes) of the tracker unit 110, it is possible to grasp changes in the position and orientation of the patient's pelvis.

After the hip replacement surgery is performed, tracker device 100 is removed from the pelvis.
Specifically, the tracker device 100 can be removed by rotating the fixing member 120 around its axis, in this example to the left (counterclockwise), and then retracting the fixing member 120 along the implanted path and removing it from the pelvis.

According to the tracker device 100 of this embodiment, it is possible to easily attach and detach the tracker device 100 to and from the patient's pelvis.
Furthermore, the tracker device 100 can be attached and detached by manually rotating it using a jig (for example, a T-shaped handle for rotating the fixing member 120) as needed, which provides excellent safety.
Furthermore, the fixation member 120 embedded in the pelvis is in a state in which the wire that forms it is contained within the bone tissue, and while conventional screws are anchored to the bone by the unevenness of peaks and valleys on their surface, the wire is in contact along the spiral perforation, so the tracker device 100 of the present invention is firmly fixed to the pelvis when pulled out in the direction of the central axis of the screw or the central axis of the spiral circle, and its pull-out resistance is extremely high.
Furthermore, after the fixing member 120 is removed, the scar remaining on the skin is extremely small, equivalent to the diameter of the wire, and no treatment such as suturing is required for a wound of this size. Furthermore, the hole remaining in the pelvis is small and can be closed with bone tissue that regenerates in a short period of time.
Taking these factors into consideration, the tracker device 100 of this embodiment is extremely minimally invasive to the patient.

Second Embodiment
The tracker device 200 of this embodiment shown in FIGS. 2A and 2B is a tracker device that constitutes a navigation system used when performing total hip replacement surgery, and is fixed to the patient's pelvis in the same manner as the tracker device 100 of the first embodiment.

The tracker device 200 includes a tracker unit 210 and a fixing member 220.
The configuration of the tracker unit 210 (reflective markers 211 to 214) is similar to that of the tracker unit 110 (reflective markers 111 to 114) in the first embodiment.

The fixing member 220 constituting the tracker device 200 comprises a helical coil having a pointed end 221, and this fixing member 220 is formed from wire having a square cross section, and the pointed end 221 of the fixing member 220 is in the shape of a substantially square pyramid or a substantially square truncated pyramid (which may have a rounded top).
The fixing member 220 may be made of the same material as the fixing member 120 of the tracker device 100 of the first embodiment.

The thickness of the wire material forming the fixing member 220 (the length s of the sides of the square cross-sectional shape) is preferably 1.5 to 3.0 mm, and more preferably 1.8 to 2.5 mm. Furthermore, the outer diameter (coil diameter) D, pitch (coil pitch) p, and length (coil length) L of the fixing member 220 are the same as those of the fixing member 120 of the tracker device 100 of the first embodiment.

The tracker device 200 of this embodiment can achieve the same effects as the tracker device 100 of the first embodiment.

Third Embodiment
The tracker device 300 of this embodiment shown in FIG. 3 is a tracker device that constitutes a navigation system used when performing total hip replacement surgery, and is fixed to the patient's pelvis in the same manner as the tracker device 100 of the first embodiment.

The tracker device 300 includes a tracker unit 310 and a fixing member 320.
The configuration of the tracker unit 310 (reflective markers 311 to 314) is similar to that of the tracker unit 110 (reflective markers 111 to 114) in the first embodiment.

Tracker device 300 comprises a fixation member 320 that consists of a helical coil with a tip 321 at its distal end.
Fixing member 320, which is made of a spiral coil, is formed from a wire rod (round wire) having a circular cross section, and has a cutting edge machined at its tip 321. That is, fixing member 320 has the same configuration as fixing member 120 of tracker device 100 of the first embodiment, except that tip 321 has a cutting edge machined.

As shown in Figure 3, the cutting edge processed tip 321 has a roughly equilateral triangular pyramid shape, with edges formed on the sides (side edges) of the equilateral triangular pyramid.

The tracker device 300 of this embodiment can achieve the same effects as those achieved by the tracker device 100 of the first embodiment.
Furthermore, since the tip 321 of the fixing member 320 is machined with a cutting edge, its sharpness is increased, and the formed edge can efficiently scrape away the cortical bone tissue on the surface of the pelvis, making it possible to more smoothly implant the fixing member 320 into the pelvis.

Fourth Embodiment
The tracker device 400 of this embodiment shown in FIG. 4 is a tracker device that constitutes a navigation system used when performing total hip replacement surgery, and is fixed to the patient's pelvis.

The tracker device 400 includes a tracker unit 410 and a fixing member 420.
The configuration of the fixing member 420 is similar to that of the fixing member 120 in the first embodiment.

The tracker unit 410 that constitutes the tracker device 400 has a two-dimensional tracker on which optically readable information (image information such as a two-dimensional matrix) is printed.

The tracker device 400 of this embodiment can achieve the same effects as the tracker device 100 of the first embodiment.

Although the embodiments of the present invention have been described above, the present invention is not limited to these and various modifications are possible.
For example, the marker mounted on the tracker unit may be a self-luminous marker.
The tracker unit may also be equipped with an optical sensor.
Furthermore, the cross section of the wire that forms the fixing member (spiral coil) may be quadrilateral other than a square (such as a diamond, rectangle, or trapezoid), semicircular, elliptical, triangular, pentagonal, or hexagonal.
Furthermore, the pointed end of the fixing member may be subjected to cutting edge processing other than that shown in the third embodiment.
Additionally, the tracker device of the present invention can be fixed to the femur, tibia, or other bones of the patient in addition to the pelvis.

100 Tracker device 110 Tracker unit 111 to 114 Reflective marker 120 Fixing member 121 Tip of fixing member 200, 300, 400 Tracker device 210, 310, 410 Tracker unit 220, 320, 420 Fixing member 221 321, 421 Tip of fixing member

Claims (12)

A tracker device that constitutes a navigation system used when performing orthopedic surgery, comprising a tracker unit having at least one optical marker and a fixation member for fixing the tracker unit to a patient's bone, the fixation member being a helical coil having a pointed end. The tracker device of claim 1, wherein the spiral coil is formed from a wire having a circular cross section, the wire diameter (d) is 1.2 to 3.0 mm, the coil diameter (D) is 2.8 to 12 mm, the coil pitch (p) is 2.4 to 30 mm, and the coil length (L) is 8 to 140 mm. a ratio (D/d) of the coil diameter to the wire diameter is 1.5 to 5;
3. The tracker device of claim 2, wherein the coil pitch to the wire diameter (p/d) is 1.35 to 6. The tracker device of claim 1, wherein the spiral coil is formed from wire having a polygonal cross section, such as a circular, semicircular, elliptical, triangular, rectangular, pentagonal, or hexagonal cross section. A tracker device according to any one of claims 1 to 4, wherein the pointed end of the spiral coil is machined to have a cutting edge. A tracker device according to any one of claims 1 to 4, wherein the fixing member is detachable from the tracker unit. A tracker device according to any one of claims 1 to 4, wherein the tracker unit has at least one light-reflecting marker or light-emitting marker. A tracker device according to any one of claims 1 to 4, wherein the tracker unit has a two-dimensional tracker on which optically readable information is printed. The tracker device described in any one of claims 1 to 4 is fixed to a patient's bone when performing total joint replacement surgery. The tracker device of claim 9 is fixed to a patient's pelvis when performing total hip replacement surgery. The tracker device of claim 9 is fixed to a patient's femur when performing total hip replacement surgery. The tracker device of claim 9 is fixed to a patient's femur or tibia when performing total knee replacement surgery.