A modified ogata-goldsand technique for simplified intraoperative measurement of femoral version

Background: Femoral anteversion can be difficult to determine intraoperatively, particularly in cases with complicated deformity. Although biplanar methodology exists for measuring femoral anteversion, the measurements are generally based on the proximal femur, without consideration for the femoral bow. Methods: We directly measured femoral version in 70 mature cadaveric femora. Using the standard Ogata-Goldsand approach, femoral version was geometrically calculated after measuring apparent neck-shaft angle and the β-angle, which is the angle between the femoral neck and proximal femoral shaft on a direct lateral view. We then used a modified β-angle, measured between the femoral neck and a line representing the entire femur. Results: Mean anatomic femoral anteversion was 20±11 degrees. Mean calculated femoral version using the standard Ogata-Goldsand technique was 32±13 degrees, whereas mean calculated femoral version using the modified Ogata-Goldsand technique was 22±12 degrees. Repeated measures ANOVA analysis found an overall statistically significant difference between the 3 groups (P<0.0001). Pairwise comparisons revealed a significant difference between directly measured version and the standard Ogata-Goldsand technique (P<0.0001) but not between directly measured version and the modified Ogata-Goldsand technique (P=0.76). Conclusions: Standard biplanar imaging techniques do not account for the femoral bow and can significantly overestimate femoral anteversion. If a line is drawn from the posterior femoral condyles to the posterior aspect of the greater trochanter, femoral anteversion is better approximated. Intraoperatively, we obtain this line by positioning a marker over the skin under fluoroscopy. Clinically, if one aims for a modified β-angle of 5 degrees, a postosteotomy anteroposterior radiograph is no longer necessary, given the knowledge that with apparent neckshaft angles ranging from 115 to 155 degrees, version will lie within a generally accepted range between 2 and 11 degrees. Clinical Relevance: In complex operative cases where imaging is desired to measure intraoperative femoral version, we recommend a modified and simplified lateral view measurement technique, which improves accuracy by accounting for the femoral bow.