![]()
1
The History of Joint Replacement in Veterinary Surgery
Mariana Quina and Jeffrey N. Peck
Total joint replacement has gained an important place in veterinary orthopedic surgery. There are currently commercially available prosthetic components and instrumentation for canine and feline total hip replacement, canine total elbow replacement, and canine total knee replacement. Although many different implant systems have been developed for experimental use, descriptions of the implants in this chapter are limited to the commercially available systems.
Total Hip Replacement
Total hip replacement became commercially available in the dog in 1974 (Hoefle 1974). The implant system used was a cemented, fixed-head, stainless steel femoral component and polyethylene acetabular cup that was available in three sizes (Richards Manufacturing, Memphis, TN; Figure 1.1). The Richards II canine total hip prosthesis was the only commercially available canine system until 1990. Design modifications to the implants were made in the late 1970s in order to decrease the tendency for luxation, provide more consistent placement of the acetabular component, and reduce the possibility of damage to the femoral component during preparation of the femur. These changes included a 20-degree cutaway on the dorsal aspect of the acetabular component, establishment of a guide system for placement of the acetabular component, several minor changes to the femoral component design, and introduction of a femoral component trial prosthesis to be used during preparation of the femur.
In 1979, Leighton reported on the use of the Richards II system in nine experimental dogs. Each of the three available sizes of prostheses was implanted in three dogs each. Of the nine dogs, there was one failure due to infection resulting in acetabular component loosening. The remaining eight dogs reportedly had good or excellent function 1 year after surgery. Use of the Richards II system was reported in a clinical setting with good success (Lewis and Jones 1980; Olmstead et al. 1983). Lewis and Jones performed 20 total hip replacements in 15 dogs and reported the results with a minimum of 1-year follow-up. The most common complication was loosening of the acetabular component, the femoral component, or both. Causes of aseptic loosening were not clearly identified or understood at the time of the Lewis publication. Contributing factors to implant loosening that were identified included infection, inadequate preparation of the bone prior to cement placement, undersizing of implants, and improper positioning of the implants. Other complications included failure of the femoral component via bending or breakage at the stemāneck angle and luxation. Only six of the hips did not have postoperative complications. Four of the 20 hips were eventually explanted. Of the remaining 16, 75% were considered to have excellent outcome.
Olmstead et al. (1983) reviewed 221 total hip replacements over a 5-year period. Follow-up information was available for 216 of the cases. The minimum follow-up period for inclusion in the study was 4 weeks, and of the 149 hips that were not lost to follow-up at study completion, none had an evaluation period shorter than 25 weeks. At the final evaluation, 91% were reported to have satisfactory function, with owners reporting increased activity levels, improved muscle mass, and elimination of pain. Of the dogs with bilateral hip dysplasia, unilateral hip replacement resulted in enough improvement in clinical signs that surgery on the contralateral side was not deemed necessary for 80% of dogs. Complications included luxation, infection, aseptic loosening of the acetabular component, femoral fracture, and sciatic neurapraxia. The overall complication rate was 20%, with 58% of cases with complications eventually achieving a satisfactory outcome. Evaluation of follow-up radiographs, as well as what constituted a satisfactory outcome, was not discussed.
In June 1990, the BioMedtrix CFXĀ® system (BioMedtrix, Boonton, NJ), a modular cemented total hip prosthesis and instrumentation set, was introduced (Olmstead 1995). The most significant change in this modular system compared with the fixed-head system was the introduction of a two-piece femoral component. The femoral component consists of a stem and a head secured together via a locking taper mechanism. This change allowed for three different neck lengths for each stem. The original CFX femoral stem was made of titanium alloy (TiAlVn) and was available in five sizes. The head was made of cobalt-chrome and available in three sizes. New instrumentation was also introduced, including power reaming of the femur and acetabulum to increase accuracy and the ease of the procedure. Olmstead (1995) reported preliminary clinical results for 52 total hip replacements using this system. Follow-up ranged from 2 months to 15 months (mean: 6 months) and consisted of owner questionnaires regarding the dogsā function following total hip replacement. Only two complications were reported, one luxation and one iatrogenic intrapelvic hematoma causing urethral compression, both of which were resolved successfully with additional surgical intervention. In 2004, Liska reported on 730 consecutive hip replacements using the BioMedtrix CFX system, with a mean follow-up of 3.9 years.1 Complications included both craniodorsal and ventral luxation, infection, aseptic loosening, femur fracture, sciatic neuropraxia, pulmonary embolism, incision granuloma, extraosseous cement granuloma, medullary infarction, and osteosarcoma. The procedure was considered successful in 96% of cases. The Liska study included the most comprehensive description of outcome and complications to date. While several of these complications had been described in case reports (Roe et al. 1996; Marcellin-Little et al. 1999a,b; Sebestyen et al. 2000; Bergh et al. 2006), this large study was the most comprehensive to date and it allowed a direct comparison of the rate of all complications. The BioMedtrix CFX system is discussed in detail in Chapter 7.
The original total hip replacement femoral implants were made of stainless steel. Newer generations of femoral implants were made of titanium alloy. Titanium is resistant to corrosion and is highly biocompatible, making it an attractive material for surgical implants. However, under certain conditions, particularly when used as a cemented stem, titanium alloys are more susceptible to severe abrasive corrosive wear than stainless steel or cobalt-chrome alloys (Agins et al. 1988). This is primarily associated with the elastic modulus mismatch between cement and titanium and the proclivity of titanium alloys to generate wear debris under such condition (see Chapters 3 and 6). Lee et al. (1992) found an unusually large amount of metal debris in the tissues around titanium alloy prostheses showing early failure as well as larger polyethylene particles in tissues from failed titanium alloy than from cobalt-chrome or stainless steel prostheses. These particles lead to wear debris, which stimulates macrophage recruitment and cytokine release and result in bone resorption and, therefore, aseptic loosening (Goldring et al. 1983).
Uncemented total hip replacement techniques have been developed to avoid the use of cement, which, despite improvements in cementing techniques, continues to be implicated in irreversible infections and aseptic loosening (DeYoung et al. 1992; Marcellin-Little et al. 1999b). Skurla et al. (2005) investigated aseptic loosening in 38 total hip replacements from 29 client-owned dogs. The duration of implantation ranged from 8 months to over 11 years and all were postmortem retrieval specimens. Nine of the femoral components were grossly loose and 15 were mechanically loose, for a total of 63.2% loose implants. Stem loosening occurred more commonly at the cementāimplant interface than at the cementābone interface. No significant difference was found in loosening rates for implants retrieved in the short term (defined as less than 3 years) and in the long term. Edwards et al. (1997) also reviewed aseptic loosening in 11 total hip replacements in 10 dogs. Loosening of the femoral component occurred at the cementāimplant interface at a mean of 30 months postoperatively. Radiographic changes associated with aseptic loosening included asymmetrical periosteal reaction along the femoral diaphysis, radiolucent zone at the stemācement interface, altered implant position, and femur fracture. They found that aseptic loosening was significantly more common when the distal tip of the femoral component was in contact with the cortical endosteum than when there was no contact.
The clinical use of the PCA Canine Total Hip system (Howmedica, Mahwah, NJ) was reported, but was not commercially produced for the veterinary market (DeYoung et al. 1992; Marcellin-Little et al. 1999a). However, the PCA system is considered the predecessor for the BioMedtrix BFXĀ® system. DeYoung et al. (1992) described the PCA implant design as well as the surgical technique for implantation. The femoral component of this system was available in four sizes, each made of cast cobalt-chromium alloy with porous coating at the proximal one-third of the stem. The modular femoral head allowed for two different femoral neck lengths and to be used interchangeably with the stems and acetabular components. The acetabular component was a cast cobalt-chromium alloy with a backing of three layers of beads and an ultrahigh-molecular-weight polyethylene insert. Two polyethylene insert depths were also available. Both the acetabular and femoral components were a press-fit with long-term stability imparted by porous bone ingrowth. A preliminary study was done on 60 experimental hips followed by 40 clinically affected hips in 32 client-owned dogs. The overall success rate for the 100 total hips was 98%. There were six complications including three luxations, two fissure fractures of the femur, and one displacement of the acetabular component due to improper positioning. Only two of the hips were eventually explanted. Marcellin-Little et al. (1999b) reported on 50 consecutive total hip replacements in 41 dogs. Mean long-term follow-up was 63 months. Radiographically, all cups and stems had bone ingrowth fixation and no evidence of osteolysis, late stem subsidence, or cup tilting. At the long-term follow-up, 74% of hips had normal function. Of those with abnormal function, three had luxations and the remainder had unrelated problems causing abnormal hind limb gait.
The Zurich Cementless Total Hip Replacement system (Kyon, Zurich, Switzerland) has been available since the late 1990s (Guerrero and Montavon 2009). In this system, the femoral components are made of titanium and titanium alloy and the acetabular component is lined with ultrahigh-molecular-weight polyethylene. The femoral stem in this system is anchored to the medial cortex of the femur with locking screws. This design is intended to decrease complications resulting from subsidence, as well as micromotion at the boneāimplant interface. Stress shielding of the bone is also meant to be minimized.2 This prosthesis is discussed in detail in Chapter 7. The BioMedtrix BFX system is an uncemented total hip replacement system designed to be interchangeable with the BioMedtrix CFX system. It was commercially introduced in 2003. The femoral and acetabular components of the BFX system are press-fit and designed to allow porous ingrowth for long-term stability. This prosthesis is discussed in detail in Chapter 7.
The dog has been used as a model for human total hip replacement for decades. Total hip replacement in the dog as a model for the development of a prosthesis for human use was first reported in 1957 (Gorman 1957). Gorman implanted a cementless, stainless steel prosthesis in over 50 dogs. The acetabular component was stabilized using three toggle bolts and the femoral component was simply inserted into the femoral canal without fixation, although the first-generation stem was transfixed to the medullary canal (Figure 1.2). The femoral head was retained within the acetabular component by a retaining rim to prevent luxation. The author reported generally positive results.
Chen et al. (1983) performed total hip replacement in 13 dogs. The cementless femoral component was square in cross section and with a titanium core and a 2-mm outer layer of unalloyed 50% fiber titanium composite. Seven dogs were implanted with a cementless acetabular component of ultrahigh-molecular-weight polyethylene and a cylindrical outer surface, coated with unalloyed titanium fiber. The remaining six dogs were implanted with cemented acetabular components. Bone ingrowth occurred in all porous-coated implants; however, no mechanical testing was performed in this study to evaluate the strength characteristics of the implants. All of the animals walked without functional deficits and all femoral stems and acetabular cups were stable at 6 months postoperatively.
Gitelis et al. (1982) studied the effects of weight bearing on the boneācement interface in cemented total hip replacements in two groups of six dogs. A cobalt-chrome femoral component and ultrahighāmolecular-weight polyethylene acetabular component were implanted using acrylic cement. In one group, immediate weight bearing with unrestricted activity was allowed, while in the second group amputation distal to the knee was performed in order to prevent weight bearing. Three of the dogs in the weight-bearing group had postoperative luxation. These dogs were eliminated from the study and replaced with three new dogs. Endosteal bone remodeling with a fibrous membrane located between the endosteal surface of the bone and cement was found in both weight-bearing and nonweight-bearing dogs. The study found that early postoperative weight bearing was not a factor in bone remodeling at the boneācement interface and surrounding bone.
Dowd et al. (1995) investigated the role of implant motion, titanium alloy, cobalt-chrome alloy, and polyethylene particles in the process of osteolysis and aseptic loosening. Forty dogs had total hip replacements and were assigned to the control group or one of five experimental groups. The control group had a standard prosthesis implanted. The prosthesis was modified for the experimental groups to create a motion model, a gap model, and three particulate debris mod...
