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A retrospective multi-centre study was carried out in order to compare outcomes between cemented and uncemented total hip arthoplasties (THA). A quantitative orthopaedic outcome assessment scoring system was devised in order to relate functional outcome to a numerical score, to allow comparison between treatments and amongst centres. The system combined a radiographic score and a clinical score. Lower scores reflect better outcomes than higher scores. Consecutive cases of THA were included from two specialist practices between July 2002 and December 2005. The study included 46 THA patients (22 uncemented THA followed for 8.3 +/- 4.7M and 24 cemented THA for 26.0 +/- 15.7M) with a mean age of 4.4 +/- 3.3 years at surgery. Multi-variable linear and logistical regression analyses were performed with adjustments for age at surgery, surgeon, follow-up time, uni- versus bilateral disease, gender and body weight. The differences between treatment groups in terms of functional scores or total scores were not significant (p > 0.05). Radiographic scores were different between treatment groups. However, these scores were usually assessed within two months of surgery and proved unreliable predictors of functional outcome (p > 0.05). The findings reflect relatively short-term follow-up, especially for the uncemented group, and do not include clinician-derived measures, such as goniometry and thigh circumference. Longer-term follow-up for the radiographic assessments is essential. A prospective study including the clinician-derived outcomes needs to be performed in order to validate the outcome instrument in its modified form.

While hydroxyapatite coatings have been shown to enhance osseointegration of metal prostheses, the optimal extent of the coating over the femoral stem component remains unclear. In this study, we investigated the effect of the application of hydroxyapatite to the proximal half of the femoral stem vs. full hydroxyapatite coating on the madreporic-surfaced femoral stems in a canine model over time. Total hip arthroplasties were performed on 22 dogs. Fifteen had half-HA coated stems, and seven had fully HA coated stems. The dogs were followed for 3 weeks, 3 months, or 1 year postoperatively. Micromotion near the femoral component was assessed at three levels along the medial aspect of the stems. Percent bone apposition, trabecular strut width, connectivity index, and cortical porosity measurements were performed at five levels and in four quadrants about the femoral stems. Micromotion was greater adjacent to the half-coated stems at 3 weeks postoperatively only. There was a trend to decreased micromotion from proximal to distal in both stem types. Both designs fixed proximally and tended to load share laterally more than in the other three quadrants. Fully HA coated stems induced greater percent bone apposition, wider trabecular struts, and more connectivity compared to half-HA coated stems., (Copyright 2000 John Wiley & Sons, Inc.)

Objective: To evaluate the bone-remodelling response at 6 and 24 months after total hip arthroplasty around a two-thirds Madreporic-surfaced femoral component in a canine model., Design: A research study in dogs. Statistical analysis was by multivariate analysis of variance., Setting: A musculoskeletal research laboratory in a university teaching hospital., Material: Ten mature mixed-breed dogs., Intervention: Unilateral implantation of total hip arthroplasty in the right femur with a Madreporic-surfaced prosthesis. Studies were conducted at 6 months in five dogs and at 24 months in five dogs. In each case, the nonoperated femur was the study control., Main Outcome Measures: Fluorescence microscopy analysis on comparable sections at four levels of the femora, percent porosity computed by image analysis, cortical atrophy., Results: Cancellous hypertrophy was most prominent at the junction of the beaded and smooth portions of the femoral stem. At 6 months the cortex demonstrated atrophy predominant in the anteromedial quadrant. Active bone turnover was present within the interstices of the prosthesis at 6 and 24 months. No significant cortical bone loss occurred between 6 and 24 months. Stress transfer to the bone-prosthesis interface and endosteal cortical "cancellization" appear to be linked phenomena.

A canine total hip arthroplasty model was used to examine micromotion and bone apposition to a proximally two-thirds madreporic-surfaced femoral prosthesis. Micromotion was also measured following initial press-fit implantation into canine cadaveric femora. After initial press-fit fixation and either 6 or 24 months of biologic fixation, micromotion was less than 23 microns in the proximal and midstem regions, a magnitude consistent with bone apposition. Bone apposition was greatest near the junction of the madreporic and smooth surfaces and was not significantly different between 6 and 24 months (51% at 6 months and 47% at 24 months). The quality of the interface tissue appears to be conductive to long-term fixation.

The synovial membrane response to polyethylene wear debris was analyzed in canine total hip arthroplasties (THA). Fifty-four THAs were performed in healthy, mature dogs. None of the arthroplasties demonstrated clinical or radiographic signs of loosening. Synovial membrane biopsies were harvested 4 (n = 13), 6 (n = 5), 8 (n = 8), 12 (n = 15), and 24 (n = 6) months after surgery and were scored for inflammation, polyethylene (PE) wear debris, histiocyte density, and membrane thickness. The amount of PE wear debris tended to increase with time. However, the inflammatory changes within the joint capsule and synovial membrane did not progress, and the total thickness of the alveolar and surface layers decreased (P = .008). It appears that the amount of wear debris at 2 years in canine hip arthroplasties, without evidence of loosening, is well tolerated by the joint capsule.