Radiographic Assessment of Coxarthrosis following Slipped Capital Femoral Epiphysis

In all, 108 patients (151 hips) previously treated for slipped capital femoral epiphysis (SCFE), were evaluated radiographically for assessment of coxarthrosis at an average age of 47 years. Five projections were obtained of each hip (supine a.p., supine modified frog lateral, standing a.p., standing anterolateral oblique, and standing posterolateral oblique) and the superior, anterior, and posterior joint space heights were measured (abnormal: superior < or = 3.0 mm and/or anterior and/or posterior < or = 2.5 mm). Sixty-three hips (42%) had joint space narrowing in at least one projection. The standing a.p. and 2 lateral oblique views identified 54 hips as abnormal, and the supine a.p. and modified frog lateral views uncovered an additional 9. The supine a.p. view was the least helpful; 12 abnormal hips on the standing a.p. view were normal on the supine a.p. view. Isolated narrowing in the anterior and/or posterior joint space was found in 9 hips (6%). These changes could only be assessed by the 2 lateral oblique views. Our results illustrate that a combination of standing radiographs, visualising the circumference of the articular space of the hip joint, and modified frog lateral projections is necessary to fully identify coxarthrosis in hips previously treated for SCFE.