Femoral offset restauration and clinical function after total hip arthroplasty and surface replacement of the hip: A randomized study

Purpose of the study. - The preservation of femoral offset is an important element of total hip arthropalsty (THA), since it reduces the Load transferred to the cup and favors better function by enabling better joint stability. After total hip resurfacing (THR), the femoral offset is generally reduced. The purpose of this study was to compare clinical function after THA and THR as a function of the femoral offset. Material and methods. - The series included 210 patients aged 23 to 65 years with degenerative hip disease. The patients were randomized into two groups for THA or THR. All arthroplasties were implanted via a posterior approach. The pre- and postoperative plain X-rays were studied and the clinical scores were noted. The presence of limping and/or a Trendelenburg sign as well as the jump tests and the double walk test were noted. Results. - In the initial series, 145 hips (69 THR and 76 THR) were analyzed. Radiographic and demographic data were similar in the two groups. Compared with the contralateral side, femoral offset increased 4.2 mm for the THA group and declined 2.8 mm for the THR group (P < 0.001). The Postel-Merle-d'Aubigne score was 17.07 +/- 0.4 points in the THA group and 17 +/- 0.35 points in the THR group (P = 0.94). The SF-36 score was 101 +/- 1.25 points in the THA group and 100.7 +/- 1.14 in the THA group (p = 0.205). The WOMAC score was 11.7 +/- 11.4 in the THA group and 9.2 +/- 15.1 in the.THR group (p = 0.363). The results of the jump test and the double walking test were better in the THR group. There was no significant difference in the incidence of Limping and Trendeleburg sign between the two groups. There were three dislocations in the THA group and none in the THR group. Discusssion. - In this study, we observed a significant decline in femoral offset after THR. However, this reduction did not appear to affect clinical function and could even have been beneficial (in terms of implant longevity) due to the axial compression force on the femoral component. The excellent clinical scores observed after THR appear to suggest that restoration of the femoral offset is not as crucial as for THA. (C) 2007 Elsevier Masson SAS. Tous droits reserves.