WO2012075349A2

WO2012075349A2 - Orthopedic cage

Info

Publication number: WO2012075349A2
Application number: PCT/US2011/062977
Authority: WO
Inventors: Loic Dejardin
Original assignee: Board Of Trustees Of The Michigan State University
Priority date: 2010-12-03
Filing date: 2011-12-02
Publication date: 2012-06-07
Also published as: WO2012075349A3

Abstract

An adjustable joint implant including a single logarithmic spiral shaped body including adjustment devices for adjusting positions of the body relative to a bone is provided. The implant can be used in a tibial tuberosity advancement procedure. Also provided is an adjustable joint implant including a single body including an adjustment device for adjusting positions of the body relative to a bone, wherein the adjustment device includes a slotted cylinder having a deformable neck. The implant can be used in a tibial tuberosity advancement procedure. There is also provided an adjustable joint implant including a single V-shaped body including an adjustment device for adjusting positions of the body relative to a bone. The implant can be used in a tibial tuberosity advancement procedure.

Description

ORTHOPEDIC CAGE

BACKGROUND OF THE INVENTION

1 . Field of the Invention

Generally, the present invention relates to the field of medicine. More specifically, the present invention relates to a device for use in veterinary medicine.

2. Description of the Related Art

The top of the tibia that is in contact with the bottom of the femur is angled and sloped toward the back of a dog's leg. When the CCL is torn, weight-bearing movement causes the femur bone to slide down this slope. Not only is this painful, but also causes the stifle to "give out" during weight-bearing. As the femur slides down the slope of the tibia, the meniscal cartilage— a cushion between the bones that acts as a shock absorber may be crushed. In about 50% of the dogs with CCL injuries, the meniscal cartilage has been injured as well. This type of injury is often accompanied by a "click" that can be heard when a dog walks.

When the CCL is weakened or torn, the most significant long-term change in the joint is the development of arthritis. All joints with instability will develop arthritis; however the severity and the effect of the arthritis will vary from dog to dog. Most dogs with a complete CCL tear show an immediate onset of lameness. While there may be some initial improvement over several days, there usually is a dramatic decline in limb function over time. There is no benefit gained from taking a "wait and see" approach. Stabilization of the joint soon after the injury has occurred is recommended.

In small dogs, nylon bands can be used to tighten the knee, however, this technique usually is not consistently effective in large breeds. There are two main types of surgery that are recommended for medium and large breed dogs that have CCL tears: the tibial tuberosity advancement (TTA) and the tibial plateau leveling osteotomy (TPLO). The TTA is a somewhat less invasive surgery and gives similar results to the TPLO. Dogs that receive the TTA procedure will recover quicker initially, however, by 4 months after surgery both procedures have similar outcomes. (See 2009 paper by Boudrieau for a detailed comparison of both procedures.) The latter is virtually identical to the Maquet procedure developed in the 60's to address knee chondromalacia in women. The TTA is a simpler procedure than the TPLO and, as a result, its use is steadily gaining momentum among general practitioners. One of the limiting factors to its further acceptance is the need for numerous implants of variable sizes and thus, the necessity for manufacturers to produce and for general practice veterinarians to maintain a costly inventory. Yet another limiting factor is the potential for complications that may be difficult to manage by non-specialized veterinarians.

The current TTA procedure requires cages of variable sizes to move and maintain the tibial tuberosity cranially (currently several cage sizes are necessary to accommodate dogs of various configurations). A bone plate is used in association with a cage to further stabilize the tibial tuberosity. Complications such as implant failure and tibial crest fractures have been attributed to the design of these implants.

The veterinary surgical procedure known as tibial tuberosity advancement is used to treat rupture of the CrCL in the knee of dogs. "See Tibial Tuberosity Advancement" by Dr. Jeff Mayo incorporated herein by this reference. Typically, a TTA requires a selection of cages, tension band plates and forks.

During the procedure an incision about 4 to 6 inches is made along the dog's stifle to provide the surgeon access to the knee joint. The torn/ruptured cranial cruciate ligament, or CCL, is completely removed and the mensicii are examined. The veterinary surgeon will determine at the time of surgery the extent to which the (medial) meniscus has sustained damage and will remove the injured tissue. The veterinary surgeon will take care to only remove meniscal tissue that is damaged, as dogs with some intact, healthy meniscus tend to do better long-term than dogs receiving a complete meniscectomy.

A jig is first used to place consecutive holes in the tibial tuberosity at a specific angle and spacing for future plate fixation via a fork. Following a frontal plane osteotomy extending from the upper tibial joint surface to the terminus of the tibial crest, the tibial tuberosity is advanced cranially using T-handle with spreaders. The osteotomy site is held open while testing for appropriate cage size.

The amount of advancement, and thus the proper cage size, is determined from preoperative radiographs. The tibial tuberosity is advanced to achieve a perpendicular relationship between the tibial plateau slope and patellar tendon, resulting in a stable joint during weight bearing. The selected cage is wedged in the open osteotomy site approximately 4-6 mm below the joint surface and secured medially using bone screws inserted through holes in the wings of the cage. A fork inserter is then used to press fit the fork through the upper section of the tension band plate and into the tibial tuberosity. The distal aspect of the plate is secured to the tibial diaphysis using 2 bone screws. The cage neutralizes the compression component of the patellar ligament force while the tension band that counteracts the tensile component of the patellar ligament. A plate bender may be used to contour the plate and the ears of the cage to fit the medial surface of the tibia. To accelerate healing, the open osteotomy, distal to the cage, is grafted with autologous cancellous bone or other graft material such as allograft or hydroxyapatite (HA). Layered wound closure concludes the procedure.

SUMMARY OF THE INVENTION

According to the present invention there is provided an adjustable joint implant including a single logarithmic spiral shaped body including adjustment devices for adjusting positions of the body relative to a bone. The implant can be used in a tibial tuberosity advancement procedure. Also provided is an adjustable joint implant including a single body including an adjustment device for adjusting positions of the body relative to a bone, wherein the adjustment device includes a slotted cylinder having a deformable neck. The implant can be used in a tibial tuberosity advancement procedure. There is also provided an adjustable joint implant including a single V- shaped body including an adjustment device for adjusting positions of the body relative to a bone. The implant can be used in a tibial tuberosity advancement procedure.

BRIEF DESCRIPTION OF THE DRAWINGS

Other advantages of the present invention will be readily appreciated as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings wherein:

Figure 1 is a top view of one embodiment of the implant of the present invention; Figures 2A-D are top views of several embodiments of the logarithmic spiral design for the implant of the present invention;

Figure 3 is a partial side view of the implant of the present invention prior to the implant being cut to length; Figure 4 shows an example of a bone with a longitudinal groove drilled therein for implantation of the implant of the present invention;

Figure 5 is a close up view of the bone of Figure 4;

Figure 6 is a close up view of the bone of Figure 4 with a spreader inserted into the groove;

Figure 7 is a close up showing the use of wire to maintain the opening without causing a break;

Figure 8 is a close up of the wire wound about the bone;

Figure 9 shows an implant within the bone opening;

Figure 10 shows the implant of Figure 9 having been turned or adjusted;

Figure 1 1 shows the implant of Figure 9 having been turned or adjusted;

Figure 12 shows an alternative embodiment of the implant;

Figure 13 shows the implant of Figure 12 having been turned or adjusted;

Figure 14 shows the implant of Figure 12 having been turned or adjusted;

Figure 15 shows an alternative embodiment of the implant; and

Figures 16A-C show the deformable neck of an alternative embodiment of the implant.

DETAILED DESCRIPTION OF THE INVENTION

Generally, the present invention provides a variable size implant/cage for use in a TTA or other similar procedure. The implant is formed such that upon implantation the implant can be adjusted to custom fit the animal into which it is implanted. This allows single device to be used to effectively treat a variety of animals without requiring multiple plates.

The implant can be implanted into a joint of an animal capable of being opened and maintained in the appropriate configuration based upon the disclosed implant. The joint can be selected by one of skill in the art based on the size of the implant and the applicability of the disclosed implant. One of skill in the art can readily determine such appropriate joints.

Additionally, the implant can be used in any animal having a joint capable of receiving the disclosed implant. Examples include, but are not limited to, canines, felines, and equines. The examples provided herein relate to the use of the implant in a canine for exemplary purposes. Changes in size can be made to accommodate the animal in need.

The implant of the present invention can be formed of any material known to those of skill in the art to be a surgical grade material capable of performing as disclosed herein. Examples of such materials include, but are not limited to PGA PLA co-polymers, 316-L stainless steel, HA coated titanium and CoCr alloy.

The implant design further simplifies the TTA procedure by using a combined single cage/plate implant for use in dogs of variable sizes. The implant design expands on this surgical simplification and uses a single size implant regardless of the size of the dog. The implant can be formed of a sequence of thinner units that can be removed prior to implantation that account for the variable thickness of the tibial crest. In other words, the implant 10 can be formed as a segmented or solid rod of material. The depth of the implant 10 can be measured based upon the size of the animal that is receiving the implant 10. The implant 10 can then be cut, using either standard cutting devices that are known to those of skill in the art or a specially made tool that can easily and accurately cut the implant 10. This enable the implant 10 to be used for any sized dog and is merely made deeper or thinner as necessary based on dog size. Alternatively, the implant can be formed of several sizes, such as small, medium, and large. While the general size of the implant can vary in size, it generally has a diameter between 10-100mm. The standard sizes can be created for ease of use, but optionally could still be formed with the variable depth as disclosed above.

More specifically, the implant of the present invention is generally shown in the figures as 10. When viewed from the side the implant 10 can look like a logarithmic spiral (i.e. the cross section of a nautilus) such that a lip 1 1 is formed that extends out from a generally circular main body 9. The lip 1 1 prevents the implant 10 from continuous turned during the implantation process. When viewed in profile, the implant 10 can be either continuous or polygonal. The transverse cross section of the implant is preferably that of an isosceles trapezoid. This can be altered as necessary in order to create the implant or as deemed necessary by one of skill in the art.

The exterior surface 12 of the implant can be smooth. In other words, the outside surface can have a regular configuration that allows for greater ease in positioning the implant 10. Alternatively, the exterior surface 12 can be abrased or otherwise include an irregular configuration to create more friction in which to maintain the implant 10 in place. In another embodiment, the exterior surface 12 contains sections of smooth surface and section of irregular configuration as deemed necessary to one of skill in the art. The exterior surface 12 can also include a beveled edge (not shown). The edge can be beveled about the circumference of the exterior surface 12.

The side surface 14 can also be regularly shaped, such that there are no corners or edges. Alternatively, the side surface 12 can be formed of a series of sides as shown in Figure 12-14. This configuration enables a more frictional fit to be used to maintain the implant 10 in the proper position.

The side 14 or top 13 of the implant 10 can include regularly spaced peripheral screw holes 16 for fixation. An alternate design uses a pivoting longitudinal plate for maintaining the implant 10 in position. The screw holes 16 are preferably integral with the implant 10. Alternatively, a plate 18 containing the screw holes 16' can be either wedged, screwed, or otherwise affixed or attached to the implant. The plate 18 can be affixed in a manner that enables the implant 10 to rotate as necessary during use. The plate 18 (circular or longitudinal) can be deformable, thus enabling the plate 18 to follow the bone contour.

Alternatively, the fixation of the implant 10 can be accomplished using a "skewer" pin through the tibial crest/cage/caudal tibial cortex or using alternative technology that maintains the implant 10 in the proper orientation while maintaining the implant 10 properties outlined herein.

The implant 10 can be affixed to the bone using standard bone screws 20 or other fixation devices known to those of skill in the art. Examples of such screws 20 are well known to those of skill in the art. Alternatively, conical screws 20 can be used to affix the implant 10.

With regard to the implant 10, the center 22 of the implant 10 can include a drive hole 24 for rotation of the implant 10. The hole 24 can be specially shaped, such as star-shaped to enable only a specially made tool to be utilized for adjusting the implant 10 during the implantation. Alternatively, the implant 10 can include at least two diametrically opposed holes 26,28 and a matching fork-like wrench 30. The wrench 30 can be used for implant placement, rotation and to insure proper positioning such that the implant 10 will not move unintentionally. The implant 10 can include alternative means by which the implant 10 can be adjusted during the implantation. Other examples of tools that can be utilized include, but are not limited to a torque or hexagonal wrench and other devices known to those of skill in the art.

Additionally, the implant ' can also be formed as a slotted cylinder 32 featuring a deformable neck 34 along the opposite edge 36 of the slot 32 as shown in Figure 16. The design of the cylinder 32 is such that the exterior 38 is cylindrical and the interior 40 is shaped to accept a screw. For example the screw can be conically shaped as shown in the figures. In this embodiment the interior conical shape 40 is formed to allow insertion of a screw. The interior shape 40 enables the neck 34 or implant 10 to deform to the desired shape during the insertion of the screw. In other words, the more the screw is inserted or the larger the screw utilized, the more the neck or cage is deformed or stretched open. Alternatively, the inner surface of the hollow, slotted cylindrical implant 10' can feature opposite notches. A spreader blade 42 can be inserted between notches to stretch the implant 10'.

The implant 10 and associated components including the spreader blades 42 are formed of a plastic material that is able to withstand slight deformation such as that disclosed herein. Examples of such materials are well known to those of skill in the art. Some examples include PGA PLA, titanium and stainless steel. Other materials can also be used without departing from the spirit of the invention.

Yet another implant design is of a V-shaped cage 10"'. The arms 44 of the V can be cut to the appropriate length to match the length of the tibial tuberosity of different size dogs. The base 46 of the V-shaped implant 10"' acts as a deformable hinge. Each arm 44 rests on the inner surface of the tibial tuberosity osteotomy. The inner surface of the implant 48 features opposite groves 50 for placement of a spreader blade 42'.

The distal aspect of the tibial tuberosity can be stabilized via a figure of 8 tension band wire 52 (as described in a variation of the original TTA technique by Sebastien Etchepareborde) as shown in Figures 7-13 or a T-plate or a hook plate.

In use, the implant 10 is inserted as follows. First, holes are drilled in the appropriate area. The wedge is used to open the space for the implant. The implant is placed in the opening. Implant is twisted or turned into place, such that it creates the appropriate opening in the tibial crest. The implant is locked into place and affixed.

Alternatively, the neck of the device is formed such that it is deformable. A device is then placed within the neck to cause the neck to deform outward and conform to the dimensions of the opening to properly configure the opening to create the appropriate dimensions.

After the device is affixed in place, or prior to being inserted the width of the device can be altered such that the device does not extend past the opening. This enables the same device to be utilized for multiple sized animals.

It should be appreciated by those of skill in the art that the techniques disclosed herein represent techniques known to those of skill in the art and can be used in conjunction with the device of the present invention. However, those of skill in the art should, in light of the present disclosure, appreciate that many changes can be made in the specific embodiments which are disclosed and still obtain a like or similar result without departing from the spirit and scope of embodiments disclosed herein.

Throughout this application, author and year and patents by number reference various publications, including United States patents. Full citations for the publications are listed below. The disclosures of these publications and patents in their entireties are hereby incorporated by reference into this application in order to more fully describe the state of the art to which this invention pertains.

The invention has been described in an illustrative manner, and it is to be understood that the terminology, which has been used herein, is intended to be in the nature of words of description rather than of limitation.

Obviously, many modifications and variations of the present invention are possible in light of the above teachings. It is, therefore, to be understood that within the scope of the described invention, the invention can be practiced otherwise than as specifically described.

Claims

CLAIMS What is claimed is:

1 . An adjustable implant comprising:

a single logarithmic spiral shaped body including adjustment means for adjusting positions of said body relative to a bone.

2. The implant according to claim 1 , wherein said implant is formed of a surgical grade material.

3. The implant according to claim 2, wherein said material is selected from the group consisting essentially of PGA/PLA co-polymers, stainless steel, titanium, coated titanium, and CoCr alloy.

4. The implant according to claim 1 , wherein said adjusting means is a drive hole.

5. The implant according to claim 4, wherein said drive hole is formed in a

shaped selected from the group consisting essentially of a star-shape, a hexagonal shape, and two diametrically opposed circular holes.

6. The implant according to claim 1 , wherein said body includes an exterior surface.

7. The implant according to claim 6 wherein said exterior surface includes a configuration selected from the group consisting essentially of irregular and regular.

8. The implant according to claim 6 wherein said exterior surface further

includes a beveled edge.

9. The implant according to claim 1 , wherein said body further includes affixation means.

10. The implant according to claim 9, wherein said affixation means includes at least one hole and screw means.

1 1 .The implant according to claim 10, wherein said screw means are selected from the group consisting essentially of bone screws, conical screws, and skewers.

12. The implant according to claim 10, wherein said affixation means includes a plate and screw means.

13. The implant according to claim 12, wherein said plate is deformable.

14. An adjustable joint implant comprising:

a single body including adjustment means for adjusting positions of said body relative to a bone, wherein said adjustment means includes a slotted cylinder having a deformable neck.

15. The implant according to claim 14, wherein said deformable neck is formed to matingly engage an affixing means for affixing said body in place and causing said deformable neck to fill a space.

16. An adjustable joint implant comprising:

a single V-shaped body including adjustment means for adjusting positions of said body relative to a bone.

17. The implant according to claim 16, wherein said V-shaped body includes two arms and a base connecting said arms.

18. The implant according to claim 1 for use in a tibial tuberosity advancement procedure.

19. The implant according to claim 14 for use in a tibial tuberosity advancement procedure.

20. The implant according to claim 16 for use in a tibial tuberosity advancement procedure.