Alendronate reduces periprosthetic bone loss after uncemented primary total hip arthroplasty - a 5-year follow-up of 16 patients.

BACKGROUND AND AIMS: Periprosthetic bone loss, especially in the proximal part of the femur, is common after cemented and uncemented total hip arthroplasty (THA). Short-term studies suggest that bisphosponates can minimize this bone loss related to stress-shielding phenomenon. The aim of the present randomized study was to investigate whether the positive effect of a 6 months alendronate treatment postoperatively still exists at five-year follow up. MATERIALS AND METHODS: Sixteen uncemented primary THA patients were randomized to receive either 10mg alendronate + 500 mg calcium (n = 7) or 500 mg calcium only (n = 9) daily for 6 months postoperatively. Periprosthetic bone mineral density (BMD) was measured with the dual X-ray absorptiometry (DXA) postoperatively and at 6, 12, 24, 36 and 60 months follow-up. RESULTS: At the 5-year follow up, the calcium group showed mean BMD decreases of 23.1% (SD 14.6) in the proximal part of the femur (prROI) and 9.6% (SD 14.9) in total femoral regions of interest (totROI). In the alendronate group the corresponding BMD decreases were 13.6% (SD 19.0) and 3.9% (SD 7.6) respectively. The positive effect of alendronate was already demonstrated during the first six months postoperatively. Subsequently the bone loss was equal in both groups, and the 5-year BMD changes were not significantly different between the groups. CONCLUSIONS: Alendronate seems to decrease early periprosthetic bone loss after arthroplasty but this pilot study could not provide enough evidence that the positive effect noted in the early postoperative period is still maintained 5 years after the operation.

Discrimination between cases of hip fracture and controls is improved by hip structural analysis compared to areal bone mineral density. An ex vivo study of the femoral neck.

In vivo bone densitometry is affected by measurement inaccuracies arising from the assumptions made about soft tissue and marrow composition. This study tested the hypothesis that section modulus (SM, a measure of bending resistance) when measured ex vivo, would discriminate cases of hip fracture from controls better than areal bone mineral density (aBMD). The biopsies were from (n = 22, female) subjects that had suffered an intracapsular hip fracture. The control material (n = 24, female) was from post-mortem subjects. Serial peripheral quantitative computed tomography (pQCT) 1-mm thick cross-sectional images of femoral neck previously embedded in methacrylate were obtained with the Densiscan 1000 pQCT densitometer and matched for lateral location. The image voxels were converted to units of bone mass, which were then used to derive the section modulus. The data were used to derive means from which receiver operating characteristic (ROC) curves could be generated. The area under the curves (AUC) showed that discrimination between the fracture cases and controls was better for SM than aBMD [SM: AUC = 0.83 (95% confidence interval: 0.71, 0.96), aBMD: AUC = 0.70 (0.54, 0.85); P = 0.034]. To simulate the forces experienced during a sideways fall, the model's neutral axis was rotated by 210 degrees. The results for section modulus were predictable from those at 0 degrees (r(2) = 0.97). We conclude that biomechanical analysis of the distribution of bone within the femoral neck may offer a marked improvement in the ability to discriminate patients with an increased risk of intracapsular fracture. Progress towards implementing this form of analysis in clinical densitometry should improve its diagnostic value, but may depend in part on better image resolution and more accurate corrections for the variability between subjects in regional soft tissue composition.

Need and sequence of large joint replacements in rheumatoid arthritis. A 25-year follow-up study.

OBJECTIVE: The aim of the present study was to evaluate the number and sequence of large joint replacements (LJR) performed in long-term rheumatoid arthritis (RA) from an inception cohort of 103 patients with rheumatoid factor (RF)-positive RA followed over 25 years. METHODS: A total of 83 patients attended the 15-year and 68 patients the 20-year follow-up. Patient documents and radiographs were evaluated in the beginning of 2001 and a complementary interview was arranged to assess the number and sequence (timing) of LJRs performed. RESULTS: The cumulative number of LJRs performed for 22 patients (19 women) during the 25 years of follow-up was 41. Seventeen total hip joint replacements (THR) (42% of the total number of 41 LURs) were performed on 13 patients, median time from the diagnosis to the operation being 14 years; 14 total knee replacements (TKR) (34%) on 11 patients (after a median time of 17 years); 3 total shoulder replacements (TSR) (7%) on 3 patients (median time of 18 years); and 7 total elbow replacements (TER) (17%) on 4 patients (median time of 21 years), respectively. Six patients had undergone three or more LJRs during the follow-up period. CONCLUSION: During our 25 years of follow-up, in 27% of RA patients LUR was needed, and 41% of them needed more than one replacement.