IMMEDIATE WEIGHTBEARING AFTER UNCEMENTED TOTAL HIP-ARTHROPLASTY

Radiographic subsidence of the femoral prosthesis and clinical results after unilateral and simultaneous bilateral uncemented total hip arth roplasty were compared. Patients who had bilateral total hip arthropla sty began weight-bearing as tolerated on both lower extremities the da y after surgery. Patients who had undergone unilateral total hip arthr oplasty were maintained at 10% weightbearing on the operative limb for 6 weeks after surgery. Patients in both groups were matched for age, gender, and weight. Minimal followup was 2 years. There was no differe nce between the two groups in terms of clinical results. Radiographic assessments were performed immediately after surgery, 6 weeks after su rgery, and again at 2 years after surgery. Radiographs were reviewed b y a single observer and analyzed with a digitized data recorder. Incre ased subsidence of the femoral prosthesis within the bilateral group w as found at 6 weeks. The mean subsidence of the femoral prosthesis at 6 weeks for the bilateral total hip arthroplasty group was 0.86 mm (ra nge, 0.18-2.60 mm) and for the unilateral group was 0.39 mm (range, 0. 07-1.46 mm). However, subsidence occurring between 6 weeks and 2 years averaged 0.50 mm (range, 0.09-1.10 mm) for the bilateral group and 0. 54 mm (range, 0.03-0.99 mm) for the unilateral group. This difference was not significant. At the 2-year followup, all femoral prostheses in both groups appeared radiographically stable with evidence of bone in growth and no indications of loosening. Thus, immediate weightbearing after bilateral total hip arthroplasty in this study resulted in more initial subsidence (during the first 6 weeks after surgery) of the fem oral prosthesis but did not preclude the prosthesis from becoming stab le and achieving bone ingrowth. Patients in both groups obtained satis factory clinical results. Because initial stability and bane ingrowth are factors influenced by prosthesis design, the results of this study may not be applicable to all implants.