Decreased femoral periprosthetic bone mineral density: a comparative study using DXA in patients after cementless total hip arthroplasty with osteonecrosis of the femoral head versus primary osteoarthritis.

INTRODUCTION: Trabecular properties in osteonecrosis of the femoral head (ONFH) are altered for bone volume and structure in the femoral head and proximal femoral canal. We analysed the periprosthetic bone mineral density (BMD) as a correlate to bony ingrowth in patients with ONFH who received a cementless THA.

MATERIALS AND METHODS: We performed a matched-pair analysis of 100 patients with ONFH (n = 50) and primary osteoarthritis (n = 50) who received the same, unilateral cementless THA. We compared the periprosthetic BMD 5 years after surgery by means of dual energy X-ray absorptiometry (DXA) analysing the seven femoral regions of interest (ROIs) according to Gruen.

RESULTS: Within the ONFH group, significantly lower BMD values were found in the ROI 1 and 7 (p < 0.05). No statistically significant difference was found for ROIs 2-6.

CONCLUSIONS: An altered periprosthetic bone stock in the proximal femur in patients with prior ONFH might be a possible risk factor for premature loosening of the femoral stem in THA. Surgeons need to consider coating and fixation philosophy of cementless implants when choosing the right stem for patients with ONFH.