Assessment of cam morphology of the hip with ultra sound imaging by physical therapists is reliable and valid

Background: Femoroacetabular impingement syndrome is considered present when a combination of clinical symptoms, signs and morphological features of the hip co-exist. Imaging is increasingly popular in primary health care settings with physical therapists performing ultrasound (US). Objective: The aim of this study was to assess the diagnostic accuracy and inter-rater reliability of ultrasound in determining presence of cam morphology. Design: A concurrent validity and inter-rater reliability study. Methods: The presence of cam morphology of the hip was determined by α angle measures using Kinovea software. A cam was defined present when the α angle >60°. The index test was US and radiographs served as a gold standard. Results: Correlation between the radiographic α angle and ultrasound measures was r = 0.82 (p < 0.01). Inter-rater reliability was high with an ICC of 0.74 (95% CI 0.61–0.84). The predictive value for presence of cam morphology had a sensitivity of 79% and a specificity of 94%. The positive predictive value was 79% whereas the negative predictive value was 94%. Total accuracy was 90%. Conclusions: Ultrasound conducted by trained physical therapists is a valid, reliable, specific and sensitive diagnostic tool to assess the presence of cam morphology.