Peri-prosthetic bone remodeling and change in bone mineral density in the femur after cemented polished tapered stem implantation.

Abstract

We examined longitudinal changes in bone mineral density (BMD) around the femur for 5years after total hip arthroplasty (THA) using cemented collarless polished double-tapered stem implantation and investigated the influence of BMD changes on radiological remodeling of the femur. Sixty hips from 56 patients who underwent cemented THA with a collarless polished double-tapered stem were included. BMD was measured 2weeks postoperatively (baseline), 3months, 6months, 1year and annually thereafter until 5years after surgery using dual-energy X-ray absorptiometry on the lumbar spine and proximal femur of the operated side according to the Gruen's zone classification. We analyzed predictable factors for BMD preservation in the proximal femur and compared radiological remodeling of the femur and changes in BMD. BMD at 5years in zone 7 decreased less than 10%, whereas BMD in zone 1 increased to over the baseline (+ 1.9%). Multiple linear regression analyses revealed that body weight was a predictor for positive BMD change in the proximal femur. The frequency of radiolucency of the femur was significantly lower in patients who exhibited an increase in BMD at 5years compared with BMD at 2weeks in zone 7. BMD preservation of the proximal femur after cemented collarless polished double-tapered stem implantation was more effective in heavier patients. Furthermore, the frequency of radiolucency around the stem was significantly lower in patients who exceeded 100% of the baseline BMD in zone 7 at 5years.