The role of experience level in radiographic evaluation of femoroacetabular impingement and acetabular dysplasia

Accurate radiographic interpretation is essential for properly diagnosing the etiology of pre-arthritic hip pain such as femoroacetabular impingement (FAI) and acetabular dysplasia (AD); however, radiographic interpretation can be significantly influenced by the observer’s experience level. This study assesses the accuracy and inter- and intraobserver reliability in the radiographic evaluation of FAI and AD based on experience level. Fifty-five patients diagnosed with FAI, AD or normal hip morphology were identified from the principal investigator’s institutional database. Four observers performed an independent and blinded radiographic review, assessing 14 radiographic parameters and an interpretation of a final diagnosis. A second radiographic evaluation of 20 preselected cases was completed 6 weeks after the initial reading to assess intraobserver reliability. Inter- and intraobserver reliability was determined using Cohen’s Kappa Coefficient (κ) and intraclass correlation coefficient (ICC) for continuous parameters in a four-rater design. Interobserver reliability was highest across experience levels for lateral centre edge angle (ICC = 0.92) and alpha angle (ICC = 0.90) and lowest (κ < 0.3, ICC < 0.3) for joint congruency and detection of herniation pits. Intraobserver reliability was highest for acetabular depth (κ = 0.89) and alpha angle (ICC = 0.80) and lowest for head–neck offset ratio and Tönnis grade. Final diagnosis was consistent with the original blinded clinical diagnosis 75–84% of the time across four experience levels. The attending orthopaedic hip surgeon demonstrated greatest diagnostic sensitivity but lowest specificity for making an accurate radiographic diagnosis. Subjective parameters must be redefined, and objective parameters must be further developed to improve the reliability of accurately diagnosing FAI or AD.