NSAID’S REDUCE THE RISK FOR REVISION DUE ASEPTIC LOOSENING IN CEMENTED TOTAL HIP REPLACEMENT – RESULTS FROM THE DANISH HIP ARTHROPLASTY REGISTER

Abstract

Introduction: NSAID’s are routinely used as either pain-killer or in prevention of heterotopic bone formation (HBF) after total hip replacement (THR). Experimental animal studies have in two decades shown NSAID’s to influence bone remodelling, and thereby also to reduce fixation and bone healing round non-cemented implants. Clinical studies have, however, non been able to demonstrate these observations, too. This may be due a low power in such studies with only few observations. The present study present results from The Danish Hip Arthroplasty Register (DHR) on the effect of NSAID’s to revision of cemented implants due aseptic loosening.

Materials and Methods: DHR was established January 1, 1995 and covers all Danish clinics. All report both primary and revision cases to a central database. Every Danish citizen have an unique civil register number - making it possible to follow both primary and revision cases and to investigate survival due various circumstances. Cox’s regression analysis to estimate the relative risks (RR) of revision and data are presented with 95% confidence intervals.

Results: During the period 1995–2006 total 64.725 primary THR’s were recorded in DHR. Of these 8.531 cases had prophylactic NSAID after surgery in prevention of HBF. Total 409 hips (4.8%) of this population undergoing revision THR had been treated with NSAID’s after surgery. In contrast, 2.536 (4.3%) undergoing revision in the population had no NSAID’s. Overall the risk for revision for any reason was reduced for patients treated with NSAID’s (RR = 0.88 (0.79–0.98) p=0.02). This was even more significant in revision due to aseptic loosening (RR = 0.76 (0.64–0.90) p< 0.01). Subgroup analysis showed that the reduction was in the cemented THR (RR = 0.82 (0.70–0.95) p=0.01) with a further more significant sign in revision due aseptic loosening (RR = 0.69 (0.55–0.87) p< 0.01). In contrast there was no differences in cementless THR neither in revision for any reason (RR = 1.19 (0.86–1.63) p=0.30) nor for aseptic loosening (RR = 1.72 (0.87–3.43) p=0.12).

Discussion and Conclusion: The present investigation from the DHR is a good example of what can be evaluated from a register, and never possibly concluded from standard clinical studies. The results demonstrate that NSAID’s administrated in order to prevent HBF after primary THR surprisingly did not increase the risk of revision in non-cemented implants, but in contrast did reduce the risk for revision in cemented THR. The reason for this reduction is speculated, and be relate to the phenomenon that NSAID’s did not only influence the osteoblastic activity, but also the osteoclasts and thereby prevent early postoperative bone degradation after cemented THR where heat from the bone-cement may impose devascu-larisation of vital bone near the implant.