Diagnostic accuracy of clinical assessment, magnetic resonance imaging, magnetic resonance arthrography, and intra-articular injection in hip arthroscopy patients.

BACKGROUND: Hip arthroscopy has defined elusive causes of hip pain.

HYPOTHESIS/PURPOSE: It is postulated that the reliability of various investigative methods is inconsistent. The purpose of this study is to evaluate the diagnostic accuracy of these methods.

STUDY DESIGN: Retrospective review of prospectively collected data.

METHODS: Five parameters were assessed in 40 patients: clinical assessment, high-resolution magnetic resonance imaging, magnetic resonance imaging with gadolinium arthrography, intra-articular bupivacaine injection, and arthroscopy. Using arthroscopy as the definitive diagnosis, the other parameters were evaluated for reliability.

RESULTS: Hip abnormality was clinically suspected in all cases with 98% accuracy (1 false positive). However, the nature of the abnormality was identified in only 13 cases with 92% accuracy. Magnetic resonance imaging variously demonstrated direct or indirect evidence of abnormality but overall demonstrated a 42% false-negative and a 10% false-positive interpretation. Magnetic resonance arthrography demonstrated an 8% false-negative and 20% false-positive interpretation. Response to the intra-articular injection of anesthetic was 90% accurate (3 false-negative and 1 false-positive responses) for detecting the presence of intra-articular abnormality.

CONCLUSIONS: In this series, clinical assessment accurately determined the existence of intra-articular abnormality but was poor at defining its nature. Magnetic resonance arthrography was much more sensitive than magnetic resonance imaging at detecting various lesions but had twice as many false-positive interpretations. Response to an intra-articular injection of anesthetic was a 90% reliable indicator of intra-articular abnormality.