Diagnostic performance of bilateral false profile radiographs in early hip osteoarthritis.

OBJECTIVES: 1. To show that the anterior hip joint space is profiled only on the contralateral false profile radiograph. 2. To provide normal values of hip joint space width on anteroposterior and false profile radiographs. 3. To identify the best sites for joint space radiographic measurements to depict early hip osteoarthritis.

METHODS: Anteroposterior and bilateral false profile radiographs of a cadaveric pelvis with markers around the anterior part of the hip joint were obtained. Joint space width was measured at ten sites on anteroposterior pelvis and bilateral hip false profile radiographs in 37 patients without hip pain (mean age, 59 years) and 65 patients with hip pain (mean age, 57.5 years), including 30 with and 35 without radiographic osteoarthritic subchondral bone changes. Between-groups differences in joint space width at each site were evaluated using ANOVA. The ability of joint space width at each site to discriminate between patients groups was investigated using logistic regression.

RESULTS: The anterior joint space was only profiled on a contralateral false profile radiograph. Presumably, normal joint space widths were obtained in the group without hip pain. Joint space widths measured on the false profile radiographs differed significantly between the patient groups while measurements on the anteroposterior pelvis radiograph did not.

CONCLUSIONS: Bilateral false profile radiographs profile the entire hip joint space, including its anterior part, and discriminate better between patients with and without hip pain than the anteroposterior pelvis radiograph. The AS/P joint space width ratio (anterosuperior/posterior) was the best parameter.