Validity of the DEXA diagnosis of involutional osteoporosis in patients with femoral neck fractures

Background: There exists no study comparing dual energy X-ray absorptimetry (DEXA) with histomorphometry to evaluate its accuracy and validity as an assessment tool. A prospective study was done comparing the measurements of osteoporosis in patients with femoral neck fractures using the histological method of diagnosis and in the same patients with DEXA postoperatively. Patients and Methods: The histological method depends on histomorphometric analysis of bone biopsies taken from the neck of femur during surgical treatment of the fracture. We depend on three indices in histomorphometric analysis: these are osteoid seam width, osteoblast surface, and osteoid surface. The radiological method depends on the measurement of the bone mineral density using DEXA for fractured patients with the scan performed onto the contralateral nonfractured hips and lumbar spines. Results: We found positive histological histomorphometric parameters of osteoporosis in 68% of patients with the femoral neck fracture, and there is a moderate correlation between histological histomorphometric analysis and DEXA in the diagnosis of osteoporosis in these patients. In our study, DEXA can detect up to 88.2% of possible cases of osteoporosis (sensitivity 88.2%), but the specificity of this diagnostic tool is 62.5% at a t-score of <= -2, i.e., it is sensitive but less specific. The mean difference in the t-score in femoral DEXA and lumbar DEXA is almost zero. Conclusions: DEXA is a noninvasive and an affordable and easy method for the diagnosis of osteoporosis but less efficient than the histological histomorphometric method of diagnosis with a low specificity. We also found that the mean difference in the t-score in femoral DEXA and lumbar DEXA is almost zero, so DEXA of one region can reflect the change in the other region and there is no need for DEXA of both regions as a routine unless indicated for a special reason. This avoids exposing the patient to unnecessary risk of radiation and reduces cost.