Magnetic resonance imaging in the evaluation of periprosthetic acetabular osteolysis: a cadaveric study.

Periprosthetic osteolysis is a well recognized complication of total hip arthroplasty that leads to implant failure. The ability to accurately assess and visualize the position and volume of periacetabular bone defects is paramount for clinical observation and medical treatment, as well as pre-operative planning of revision surgery. We have developed a modified magnetic resonance imaging (MRI) protocol that is useful in detection and quantification of periacetabular bone loss. The purpose of this study is to compare MRI to plain film analysis in the assessment of periacetabular bone loss using a cadaver model. MRI was 95% sensitive in the detection of lesions. Specificity was 98%, and accuracy was 96%. Lesion detection was not statistically dependent on lesion location (p=0.27). The mean absolute error in determining lesion size was 0.8+/-2.2 cm3. There was a correlation between increasing lesion size and lesion detection (p=0.02, logistic regression). The largest lesion that was missed by MRI analysis measured 2.8 cm3, and all lesions 3.0 cm3 were correctly identified, with a relative error volume measurement of 12.4+/-25.3%. This correlated to an absolute error of 1.4+/-2.4 cm3. Using conventional radiographic analysis, the overall sensitivity of lesion detection was 52%, and the specificity was 96%. Using plain film analysis, identification of true lesions depended on the location with 83% of ilial lesions, 64% of pubic lesions, 55% of ischial lesions, and 0% of posterior wall lesions correctly identified. The modified MRI technique utilized did allow for accurate visualization of simulated osteolytic lesions, and may provide a suitable noninvasive method to provide serial assessment of clinical periacetabular osteolysis without the use of ionizing radiation.