Low Positive Predictive Value of Bone Scan to Predict Impending Complete Fracture among Incomplete Atypical Femoral Fracture

摘要

Background Although bone scan might be useful to detect incomplete atypical femoral fractures (AFFs) earlier than radiographs, there is no study on predicting further progression to a complete fracture among incomplete AFFs. Our purposes are to determine whether bone scan detects impending complete fracture among incomplete AFFs. Methods We reviewed 18 patients (20 AFFs) who underwent bone scan at the diagnosis of incomplete AFF and were not treated with prophylactic fixation. A diagnosis of impending complete fracture was made, when the femur completely fractured within 6 months after the scan. We correlated radioisotope uptake with the impending complete fracture to calculate sensitivity, specificity, positive predictive value and negative predictive value of bone scan. Results Thirteen AFFs (65%, 13/20) showed a positive uptake in bone scan. Among the 13, only one femur was completely fractured within 6 months. None of the 7 femurs without uptake in bone scan fractured. In diagnosing impending complete fracture, the sensitivity of bone scan was 100% and negative predictive value was 100%. However, the specificity (36.8%) and positive predictive value (7.7%) were quite low. Conclusion Bone scan has no significant role in detecting the impending complete fracture, and a positive uptake does not mean the necessity of prophylactic fixation of incomplete AFF. Go to: Graphical Abstract