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SummaryAcetabular cup displacement (ACD) was identified as a complication of cemented modular total hip replacement in seven dogs. ACD is characterized by mechanical failure of the polyethylene-cement interface and subsequent cup migration, and is a clinical entity distinct from classical aseptic loosening. ACD is a sequela of extrusion of the cup and lateralization of the prosthetic load-bearing axis. The acetabular cup displacement ratio (ACDR) has a statistically significant effect on whether ACD develops (P

SummaryFifty healthy adult Suffolk cross sheep were evaluated as a research animal for cemented total hip replacement. The surgical technique, peri-operative care, and long-term evaluation of the animals is reported. A modular cemented canine hip replacement system was used in this project. Postoperative fractures of the operated femur were observed in five animals. Two sheep developed septic loosening of the acetabular components. Two sheep experienced immediate postoperative luxations. One animal developed an acetabular fracture and infection. Five sheep exhibited mild lameness of the operated limb one year postoperatively, while all others had a normal gait. Postoperative activity level played a significant role in the development of femur fractures.Fifty adult Suffolk cross sheep were evaluated as a research animal for cemented total hip replacement. The surgical technique, peri-operative care and long-term evaluation of the animals are reported.

Total hip replacements in the dog have become well established over the past 20 years as an effective method for treating disabling hip conditions. A fixed head prosthesis has been the mainstay during most of this period. Return to normal function with this prosthesis has been reported at 95 per cent. Although patient selection, pre- and post surgical care, the surgical technique and the treatment or prevention of complications has been continually improved, it was not until recently that the prosthesis and its instrumentation were improved. Now a modular prosthesis with improved instrumentation gives the veterinary surgeon ‘state of the art’ implants and instruments. The prosthesis is easier to implant, the surgeon has greater flexibility in surgery and improved results are expected. Total hip replacement continues to be an effective way to give dogs a pain-free, mechanically sound hip joint.

A fracture is a complete or incomplete break in the continuity of bone or cartilage or both. It is accompanied by soft tissue injury and impairment of blood supply and function. Fracture disease may be defined as any pathological change in the soft tissues, joint, or bones associated with treatment of a fracture and resulting in impaired limb function. The term clinical union indicates a state in which healing bone is sufficiently strong for all fixation devices to be removed. The term osteosynthesis is used for internal fixation of a fracture by means of a mechanical device, e.g., pin, screw, plate.

SummaryThe aim of this pilot study was to define the mechanism and mode of polyethylene wear in acetabular components retrieved from seven dogs following therapeutic total hip replacement. The articular surface of each acetabular component was examined using contact profilometry and scanning electron microscopy (SEM). Peak-tovalley distance (P-V) and arithmetic average surface roughness (Ra) were calculated for each quadrant of the surface. Deformation of the regular profile of the machining lines was the least severe form of surface alteration. Randomly orientated scratches, fine tapered filaments, ripples, and coarse surface shredding were common SEM observations. Gouging of the convex surface of the cup was seen in two cases following failure of the polyethylenecement interface. Wear of the nonarticular acetabular rim suggested neck impingement in one case. P-V and Ra were significantly lower in the craniodorsal zone, compared to the average roughness of the other three quadrants (p < 0.05). Abrasion, adhesion and fatigue were the principal mechanisms of polyethylene wear, and were implicated in the production of polyethylene particulate debris. Meticulous removal of abrasive third bodies at the time of surgery, and correct orientation of the acetabular component, should reduce early and severe wear.Polyethylene wear is inevitable following metal-on-polyethylene total hip replacement. In this study, the nature of polyethylene wear in retrieved canine acetabular components was defined, using contact profilometry and scanning electron microscopy. Abrasion, adhesion and fatigue were the principal mechanisms of wear, and were implicated in the production of polyethylene particulate debris.