A reliable DEXA measurement technique for metal-on-metal hip resurfacing

Introduction Dual energy X-ray absorptiometry (DEXA) has been used to measure bone mineral density (BMD) around total hip prostheses. With the recent increase in the use of metal-on-metal hip resurfacing, such as the Birmingham hip resurfacing (BHR), we aimed to produce a reliable method of measuring bone density around a metal-on-metal hip resurfacing.

Methods We performed DEXA scans on 5 patients (7 BHRs), who had undergone resurfacing with the BHR within the past 2 years. A zonal reporting technique was devised and evaluated.

Results The intraclass correlation (i.e. the correlation between any two assessments of one region of interest) was 0.997, with an overall coefficient of variation of 5%.

Interpretation We have designed and demonstrated a safe, noninvasive and highly reproducible method for interpreting and reporting the results of DEXA scanning of BHR implants in vivo. We will now use this method to prospectively study our BHR population to assess the changes in bone density following BHR within the femoral neck. This method may add to the current techniques available for detection of impending failure.