Bone mineral density as a marker of hip implant longevity: a prospective assessment of a cementless stem with dual-energy X-ray absorptiometry at twenty years

Abstract

Purpose: Bone remodeling around the femoral component after total hip arthroplasty (THA) is considered to be an important factor in long-term stability and seems to be strictly related to the stem design, coating, and fixation. Stress shielding, micro-movement, and high intra-articular fluid pressure might activate macrophages and osteoclasts, causing progressive bone density decreases. Here we analyze the bone mineral density (BMD) around a cementless femoral stem during a 20-year period to better understand the adaptive bone changes around such implants during long-term follow-up.

Methods: In this retrospective study, 14 patients treated by THA were reviewed from a cohort of 84. Clinical evaluation with Harris Hip Score and radiographic assessment were performed throughout a 20-year follow-up. To evaluate the bone remodeling around the stem, we monitored the femoral BMD in four regions of interest with a dual-energy X-ray absorptiometry (DEXA) post-operatively and at one, two, three, five and 20 years of follow-up.

Results: The main BMD changes between the post-operative examination and the 20-year follow-up varied between + 11.19% and + 24.30%. Patients with signs of loosening, low Harris Hip Scores, and pain showed decreasing BMD values.

Conclusions: The correlation between the clinical result and BMD values could suggest DEXA results as a predictor of implant loosening or longevity.

Keywords: Cementless stem; DEXA; Periprosthetic BMD; Prosthetic loosening; Total hip arthroplasty.