Abstract
Introduction
When performing a total hip arthroplasty (THA), some surgeons routinely perform an intraoperative anteroposterior (AP) pelvis radiograph to assess components. The purpose of this study was to evaluate the reliability of the intraoperative radiograph to accurately reflect acetabular inclination, leg length, and femoral offset as compared to the immediate postoperative supine AP radiograph.
Methods
The intraoperative (lateral decubitus position) and immediate postoperative (supine position) AP pelvis x-rays of 100 consecutive patients undergoing primary THA were retrospectively reviewed. Acetabular inclination, leg length, and femoral offset were measured on both radiographs. We analyzed the correlation coefficient of the recorded measurements between the two films as well as the interobserver reliability of each measurement obtained.
Results
Our data demonstrated a high positive correlation between the intraoperative and postoperative acetabular inclination measurements of both reviewers (r=.886 and .896). In addition, no significant difference was observed between the inclination measurements (p= .06 and .37). There was a moderate correlation among the leg length (r= .58 and .66) and poor correlation among the offset (r= .29 and .25) between the two radiographs. One observer generated a significant difference between leg length measurements while both reviewers generated a significant difference between offset measurements. Interobserver reliability was high for all measurements.
Conclusion
Intraoperative AP radiographs are commonly obtained during THA to aid in evaluation of component position and size, femoral neck cut, femoral canal fill, and detection of occult fractures. Results from this study suggest that this film could also be used to accurately measure acetabular inclination, but is a less reliable indicator of femoral offset and leg length when compared to the immediate postoperative film. In addition, the high interobserver correlation illustrates the high reproducibility of the measurement methods utilized.
