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The purpose of the present article was to compare the results of primary total hip arthroplasty (THA) done because of developmental dysplasia of the hip (DDH) with the results of THA done because of idiopathic coxarthrosis (osteoarthritis) using data from the nationwide Norwegian Arthroplasty Register (NAR). In the period from 1987 to 2003, 84871 primary THAs were reported to the NAR. Of these, 6347 (7.5%) were performed because of sequelae after DDH, 788 (0.9%) because of sequelae after DDH with complete dislocation of the femoral head, and 59774 (71.0%) because of idiopathic coxarthrosis. The results of THAs after DDH were the same as those of THAs after idiopathic coxarthrosis after adjustments for younger age and for the use of more uncemented prostheses in patients with DDH.

Introduction: The cementation of a total hip prosthesis may cause bone necrosis, either by direct toxicity or by generation of heat during the polymerization process. This necrotic bone may create conditions that encourage the growth of bacteria. We compared the revision rates due to infection in primary uncemented total hip arthroplasties (THAs) with those of cemented THAs with antibiotic-loaded cement and to those of cemented THAs without antibiotic cement., Methods: Data from the Norwegian Arthroplasty Register for the period 1987-2003 were used. To have comparable groups, we analyzed only primary THAs performed because of primary osteoarthrosis, and where both the acetabular and the femoral component of the prosthesis were either uncemented or cemented (n = 56,275)., Results: In total, 252 revisions due to infection were reported. Compared to the uncemented THAs (n = 5,259), the risk of revision due to infection for THAs without antibiotic cement (n = 15,802) was increased 1.8 times (CI 1.0-3.1; p = 0.04). No differences could be detected when compared to THAs with antibiotic-loaded cement (n = 35,214) (RR 1.2, CI 0.7-2.0; p = 0.5). The average operating time for uncemented THAs was 15 min less than for cemented THAs., Interpretation: The risk of revision due to infection was the same for uncemented and for cemented arthroplasties with antibiotic-loaded cement, but higher for cemented arthroplasties without antibiotic cement. Our findings can be explained by reduced resistance to infection caused by the cement, which appears to be neutralized by adding antibiotic to the cement.

Artificial hip joints are used in only one hip for about 85 per cent of the patients and in both hips (bilateral) for about 15 per cent of the patients. The occurrence of bilateral prostheses and the influence they have in survival analyses of joint arthroplasties are seldom considered. In this study we therefore focus on issues related to bilateral primary hip prostheses, time to revision surgery, and some commonly used statistical methods. We used information from 47,355 patients with 55,782 primary hip prostheses reported to the Norwegian Arthroplasty Register between 1987 and 2000. Due to the large number of diagnoses, fixation techniques for the prostheses, and combination of prostheses brands, we furthermore considered a 'homogeneous' subset of 8703 prostheses from 7930 patients with primary osteoarthritis, and Charnley prosthesis fixed with antibiotic-containing Palacos cement. Kaplan-Meier curves for all prostheses, ignoring that some patients have bilateral prostheses, were compared with Kaplan-Meier curves using only the first inserted prostheses, and with survival curves modified for patients with bilateral prostheses. Cox regression analyses were used to assess explanatory variables and to adjust for confounding factors. The results from the ordinary Cox regression analyses were compared with results from a marginal model, a shared gamma frailty model, and a model using a time dependent covariate to condition on failures in the opposite hip. We found no practical difference between the three calculated survival curves for the hip replacement data. The ordinary Cox-model and the marginal model gave equivalent results. In the shared gamma frailty model estimates for the risk factors were comparable with the former two approaches. The estimated frailty variance was higher when all data were used, even after adjustment for confounding factors. For the 'homogeneous' data the estimated frailty variance was negligible. Using a time dependent covariate to condition on previous revisions in the opposite hip, we found a higher risk of revision for the remaining primary hip prosthesis if the opposite hip had been revised (RR = 3.49, p < 0.0001). There was no difference in risk for revision between right and left hip prostheses. If the time interval between the two primary operations was more than two years, for the full data, the first hip prosthesis had an increased risk of revision compared to prostheses in patients with only one prosthesis (RR = 1.25, p = 0.01). For the 'homogeneous' data no statistically significant difference was found between unilateral and bilateral prostheses. A revision in one hip, for patients with bilateral prostheses, is a risk factor for revision of the other hip. Thus, in analyses of prostheses survival, dependencies between two hip prostheses from one patient should be considered. However, ignoring possible dependencies does not necessarily have an impact on the results on standard risk factors., (Copyright 2004 John Wiley & Sons, Ltd.)

We studied the effects of antibiotic prophylaxis, systemically and in bone cement, on the revision rate of cemented total hip arthroplasties (THAs) in data from the Norwegian Arthroplasty Register during the period 1987-2001. To have comparable groups, only THAs performed because of primary osteoarthritis, using cemented implants with documented good results, and high-viscosity cement were included. If systemic antibiotic prophylaxis had been given, only operations with cephalosporin or penicillin were selected. Cox-estimated survival relative revision risks (RR) are presented with adjustment for differences among groups in gender, age, cement brand, type of systemic antibiotic prophylaxis, type of prosthesis, type of operating room, and duration of the operation. Of 22,170 THAs studied, 696 THAs (3.1%) were revised, 440 (2.0%) for aseptic loosening and 102 (0.5%) for deep infection. We found the lowest risk of revision when the antibiotic prophylaxis was given both systemically and in the cement (15,676 THAs). Compared to this combined regime, patients who received antibiotic prophylaxis only systemically (5,960 THAs) had a 1.4 times higher revision rate with all reasons for revision as endpoint (p = 0.001), 1.3 times higher with aseptic loosening (p = 0.02) and 1.8 times higher with infection as the endpoint (p = 0.01). With the combined antibiotic regime, the results were better if antibiotics were given 4 times on the day of surgery (2,194 THAs), as compared to once (1,424 THAs) (p < 0.001), twice (2,680 THAs) (p < 0.001), or 3 times (5,522 THAs) (p = 0.02). Those who received systemic prophylaxis a single day 1, 2 or 3 times, as compared to 4 times, had a revision rate 1.8-3.5 times higher with all reasons for revision as endpoint, 1.5-3.1 times higher with aseptic loosening, and 2.7-6.8 times higher with infection. When we compared systemic prophylaxis 4 times in 1 day, no further improvement resulted in those given systemic prophylaxis for 2 days (1,928 THAs) or 3 days (717 THAs). In a subset of data including only the Charnley prosthesis, we obtained similar results. This observational study shows that the best results were recorded when antibiotic prophylaxis was given both systemically and in the bone cement, and if the systemic antibiotic was given 4 times on the day of surgery.