The timing of bone SPECT to predict osteonecrosis after internal fixation of femur neck fractures

Background Bone SPECT can be used after a femur neck fracture to assess the circulation of the femoral head in the immediate postoperative period because the blood supply is one of the major factors affecting bone uptake of radiotracer on bone scintigraphy. The purpose of our present study was to investigate whether osteonecrosis of the femoral head (OFH) after internal fixation of femoral neck fracture could be predicted by early and late bone SPECT. Methods This retrospective cohort study enrolled 44 patients (33 women; mean age, 66.9 years) who underwent surgical fixation for femoral neck fractures. Early and late bone SPECT images were obtained within 2 weeks postoperatively and at 3 months postoperatively. Patients were followed up for a minimum of 24 months (average, 34 months). Results OFH developed in 9 out of 44 patients but no patient showed nonunion. Seventeen patients with normal femoral head uptake on early bone SPECT were healed. Of 27 patients with decreased femoral head uptake on early bone SPECT, 2 patients developed OFH on radiography before 3 months postoperatively, 18 patients recovered to normal uptake on the late SPECT, and the remaining 7 patients still showed decreased uptake on the late SPECT at 3 months postoperatively. All of these 7 cases finally developed OFH on radiography. Conclusion Bone SPECT can reliably predict the possibility of OFH with after femoral neck fracture at least 3 months after surgery, while early bone SPECT showed low specificity. Study design Clinical.