A randomized study using DXA and RSA in 38 patients followed for 5 years

Background and purpose: There is no real consensus on the best rehabilitation regime after uncemented total hip arthroplasty. Theoretically, bone ingrowth into the implant should benefit from initial partial weight bearing. We investigated whether the degree of postoperative weight bearing influences the periprosthetic bone mineral density (BMD) and/or the stability of the CLS stem.Patients and methods: 38 patients received an uncemented CLS stem and were randomized to either unrestricted postoperative weight bearing or to partial weight bearing for 3 months. Periprosthetic BMD was measured in the 7 Gruen zones with DXA and the stability of the femoral stem was assessed by radiostereometric analyses (RSA) after surgery and at 3, 12, 24, and 60 months.Results: Periprosthetic BMD was not influenced by the type of postoperative weight bearing. BMD was reduced by 8-15% in all Gruen zones at 3 months. Restoration toward initial BMD was observed in all zones except in zone 7 (calcar region), where BMD was decreased by 22% at 5 years. Immediate weight bearing after surgery did not influence the stability of the CLS stem, as assessed by RSA.Interpretation: Immediate full weight bearing after uncemented total hip arthroplasty is safe. There is no difference in the periprosthetic BMD or stability of the stem as measured with RSA compared to partial weight bearing for 3 months. BMD is decreased by more than 20% in the calcar region around a CLS stem after 5 years.