Femoral Torsion: Reliability and Validity of the Trochanteric Prominence Angle Test

Abstract

Influence of femoral torsion on femoroacetabular impingement and other hip conditions is not well documented and its assessment by imaging methods during clinical work-up is not routinely performed. We studied whether physical examination could reliably measure or at least screen for gross anomalies of femoral torsion or if appropriate imaging should routinely be performed. Assessing femoral torsion of 45 volunteers using the "trochanteric prominence angle test" and magnetic resonance imaging (MRI), inter- and intra-observer reliability ranged from poor to moderate and agreement with MRI values was only fair. Considering a 5° to 10° difference of femoral torsion as clinically relevant, physical examination failed to match MRI values within ±10° in more than 50%. Arbitrarily defining thresholds for pathological femoral torsion, the "trochanteric prominence angle test" could not recognise torsions outside the >30°/<0° range and diagnosed torsions outside the >20°/<10° range with a sensitivity of 18%-75% and a specificity of 58%-98% only. Physical assessment of femoral torsion using the "trochanteric prominence angle test" does not allow reliable measurement or screening for gross anomalies. We therefore integrate an adapted MRI protocol allowing measurement of femoral torsion within our clinical work up.