Bone remodeling and cortical thinning distal to the femoral stem: a retrospective review.

Abstract

There is a paucity of information on the bone remodeling that occurs distal to the femoral stem following total hip arthroplasty as most previous studies have focused on proximal changes. In this study, we report the cortical thinning that occur distal to the femoral stem after primary total hip arthroplasty. A retrospective review was performed at one institution over a 5-year period. 156 primary total hip arthroplasty procedures were included. The Cortical Thickness Index (CTI) was measured on both operative and non-operative hips at 1cm, 3cm and 5cm below the prosthetic stem tip on anteroposterior radiographic images pre-operatively as well as at 6months, 12months and 24months post-operatively. The difference in average CTI was measured using paired t-tests. There were statistically significant decreases in CTI distal to the femoral stem at 12months and 24months (-1.3% and -2.8%, respectively). Greater losses were seen in female patients, patients older than 75, and patients with BMI less than 35 at 6months postoperative. There were no differences in CTI at any time point on the non-operative side. The current study demonstrates that patients undergo bone loss as measured by CTI distal to the stem in the first 2years following total hip arthroplasty. Comparison to the contralateral non-operative side confirms that this change is greater than expected for the natural aging process. A greater understanding of these changes will help optimize post-operative management and direct future innovations in implant design.