Morphologic characteristics of acetabular dysplasia in proximal femoral focal deficiency

A retrospective radiographic analysis of the acetabulum of 13 patients (14 hips) with proximal femoral focal deficiency (PFFD), clinically classified into Gillespie and Torode type 1, was performed to better understand its morphologic features at maturity. The version of the proximal part of the acetabulum was determined quantitatively and qualitatively. All 14 hips showed residual or borderline acetabular dysplasia with a mean lateral centre-edge angle of -1.5degrees and an acetabular index of 30degrees. The acetabular dome was retroverted in all hips and averaged -24degrees. Acetabular deficiency compared with the opposite side, while not present with respect to the anterior wall, averaged 12% with respect to the posterior wall. Dysplasia associated with type 1 PFFD is therefore fundamentally different from that seen in developmental residual hip dysplasia. Clinically, despite radiographic evidence of dysplasia, 57% were without clinical manifestations of hip pathology. This may be due to a number of factors including age of last radiograph, severity of dysplasia, and the decreased functional demand placed on the hip in some individuals with associated malformations. For the symptomatic hip, the posterior insufficiency and relative retroversion of the acetabular dome should be taken into consideration in planning reorientation procedures. This can help to prevent problems of persistent subluxation or acetabulo-femoral impingement following reconstruction.