Dual Energy X-ray Absorptiometry (DXA) The clinical survival of joint prostheses depends on the quality of the surrounding bone and bone mineral density (BMD) is an important measure of bone strength and quality. The periprosthetic bone density can be measured with Dual Energy X-ray Absorptiometry (DXA), which is a precise method for measuring even small changes in BMD around hip prostheses. Patients are exposed to a very little dose of radiation with these studies and scanning only takes a few minutes. Typically, four to five scans are taken during a 2 to 5 year follow-up. For assessment of the bone surrounding the acetabular cup the 3 DeLee zones or the 4 Wilkinson Zones are often used, and Gruen zones are used for assesment around the stem.