Total joint replacement of the elbow and hip (Proceedings)

The most common indication for total joint replacement in the small animal is osteoarthritis or degenerative joint disease that is a cause of significant and frequent pain. The initial cause for the development of degenerative joint disease may vary but as long as there is adequate bone and normal conformation of the joint to accept the implant as well as soft tissue stability to hold the implant in place, various initial causes can be acceptable for joint replacement.

Replacement of the hip joint or total hip arthroplasty (THA) is performed as a salvage procedure in dogs with severe pain in one or both hips. Candidates for THA must have no other orthopedic disease in the limb that is to be operated as well as clients that are willing to perform the postoperative care necessary for a successful outcome. In other words, clients whose dogs undergo THA must be willing to restrict the dogs activity for several months (at least 2) after surgery, prevent them from infecting the incision postoperatively, and be willing to have their dog undergo a second surgery if complications develop. Dogs that are not candidates for THA include those with orthopedic disease in the same limb, neurologic disorders such as intervertebral disk disease, lumbosacral disease, Wobbler's syndrome, or degenerative myelopathy. At the time of surgery they should be free of infections such as gingivitis, cystitis, otitis externa, pyoderma or other infections.1 If the patient develops a distant infection postoperatively, the owners must be vigilant enough to recognize it early and seek treatment as soon as possible. The patients are at an increased incidence of infection at the surgical site if the joint has been operated on previously or the patient is prone to distant infections that can spread hematogenously to the THA.1

Two basic differences in THA exist in veterinary medicine, whether the implant is cemented in place or a cementless implant has been inserted with a press-fit. The press-fit technique avoids the use of the bone cement polymethyl methacrylate which, in theory, would decrease the incidence of aseptic loosening.2 Cemented implants have the benefits that they do not require extreme reaming of the femoral intramedullary canal and therefore would be less likely to develop fissure femoral fractures or subsidence postoperatively, work well in femurs that have a "stovepipe" isthmus as well as decreased cortical thickness.3-5 Cementless implants have the benefits that they have a potentially decreased incidence of infection, intrapelvic granulomas, and neuropathies.1,2,6 By 6 years postoperatively, 87% of cementless implants are still intact and functioning well, which makes these implants a more attractive option for placement in younger dogs. German Shepherds, with their lack of narrowing of the femoral diaphysis ("stovepipe") and relatively decreased cortical bone thickness are better candidates for a cemented implant in order to prevent complications such as subsidence and femoral fracture postoperatively.1,4

Both types of THA have complications in common and include aseptic loosening of the implants (10-15% of human cases).7 With cemented implants the technique with which the cement was mixed and injected into the femur as well as the thickness of the cement mantle all affect the incidence and rate at which aseptic loosening develops.8 In recent studies cemented THA were analyzed post-mortem in dogs that had died for reasons unrelated to their THA. Implants without aseptic loosening were on average 5 years postoperative compared to 6 years in those implants with aseptic loosening.8,9 This does not tell us definitively how long either a cemented or uncemented THA will last and that depends on many factors. For aseptic loosening, the development of wear debris increases the rate of aseptic loosening since the wear particles from the cup contact with the femoral head insight an inflammatory response and resorption of bone surrounding the implants.1 Larger acetabular cup sizes result in increased wear rates and wear debris so it follows that the larger the dog the faster wear debris and aseptic loosening will develop, however no clinical studies have proven this.10,11

Luxation of the THA is an uncommon occurrence, usually within the first month postoperatively, that most often requires a second revision surgery, sometimes a triple pelvic osteotomy is required to keep the implants seated.1 Careful surgical technique and prevention of increased activity postoperatively can prevent luxation. In addition, candidates for THA should not have severe muscle atrophy present at the time of surgery since atrophy increases the likelihood of luxation postoperatively.

Total elbow arthroplasty continues to be under development. The first system was semiconstrained, that is, capable of flexion, extension, pronation, and suponation to a limited degree.12 This system was then modified and has been used experimentally in healthy dogs as well as in dogs with severe degenerative joint disease of one or both elbows.13,14 This model has a successful out come in 16/20 dogs but complications included fractures, infection, and luxation. This system is technically demanding and may be the reason it is not used more widely by veterinary surgeons. The latest total elbow system is a constrained system called the T.A.T.E. system and has been placed in approximately 10 dogs with very few complications to date.15 There have not been any fractures or luxations and the system is less technically demanding to implant (personal communication, R. Acker). Unfortunately, there is no long-term data to support its use and it may fatigue quickly since it is so constrained, that is the dog can no longer supinate or pronate after the implants are placed. Therefore, this system should only be used in dogs with severe degenerative joint disease of the elbow that can no longer supinate or pronate the limb due to osteophytes and arthrosis in order to prevent early wear of the implants.

Much research still needs to be performed to determine the method for arthroplasty of the elbow in dogs and humans alike. The complex nature of the joint itself and the precision with which the humerus, radius and ulna interact make it one of the most unforgiving joints-one milimeter off and all function is lost.

References

1. Conzemius MG, Vandervoort J. Total joint replacement in the dog. Vet Clin North Am Small Anim Pract 2005;35:1213-1231, vii.

2. Marcellin-Little DJ, DeYoung BA, Doyens DH, et al. Canine uncemented porous-coated anatomic total hip arthroplasty: results of a long-term prospective evaluation of 50 consecutive cases. Vet Surg 1999;28:10-20.

3. Mallory TH, Kraus TJ, Vaughn BK. Intraoperative femoral fractures associated with cementless total hip arthroplasty. Orthopedics 1989;12:231-239.

4. Rashmir-Raven AM, DeYoung DJ, Abrams CF, Jr., et al. Subsidence of an uncemented canine femoral stem. Vet Surg 1992;21:327-331.

5. Pernell RT, Gross RS, Milton JL, et al. Femoral strain distribution and subsidence after physiological loading of a cementless canine femoral prosthesis: the effects of implant orientation, canal fill, and implant fit. Vet Surg 1994;23:503-518.

6. Freeman CB, Adin CA, Lewis DD, et al. Intrapelvic granuloma formation six years after total hip arthroplasty in a dog. J Am Vet Med Assoc 2003;223:1446-1449, 1433.

7. El-Warrak AO, Olmstead ML, von Rechenberg B. A review of aseptic loosening in total hip arthroplasty. Vet Comp Orthop Traumatol 2001;14:115-124.

8. Bergh MS, Muir P, Markel MD, et al. Femoral bone adaptation to unstable long-term cemented total hip arthroplasty in dogs. Vet Surg 2004;33:238-245.

9. Bergh MS, Gilley RS, Shofer FS, et al. Complications and radiographic findings following cemented total hip replacement: a retrospective evaluation of 97 dogs. Vet Comp Orthop Traumatol 2006;19:172-179.

10. Puolakka TJ, Laine HJ, Moilanen TP, et al. Alarming wear of the first-generation polyethylene liner of the cementless porous-coated Biomet Universal cup: 107 hips followed for mean 6 years. Acta Orthop Scand 2001;72:1-7.

11. Orishimo KF, Claus AM, Sychterz CJ, et al. Relationship between polyethylene wear and osteolysis in hips with a second-generation porous-coated cementless cup after seven years of follow-up. J Bone Joint Surg Am 2003;85-A:1095-1099.

12. Conzemius M, Aper RL. Development and evaluation of semiconstrained arthroplasty for the treatment of elbow osteoarthritis in the dog. Vet Comp Orthop Traumatol 1998;11:A54.

13. Conzemius MG, Aper RL, Hill CM. Evaluation of a canine total-elbow arthroplasty system: a preliminary study in normal dogs. Vet Surg 2001;30:11-20.

14. Conzemius MG, Aper RL, Corti LB. Short-term outcome after total elbow arthroplasty in dogs with severe, naturally occurring osteoarthritis. Vet Surg 2003;32:545-552.

15. Acker R, Vandermuellen G. Resurfacing arthroplasty of the canine elbow. Vet Comp Orthop Traumatol 2007;20.