Purpose: Morquio-Brailsford syndrome (MS) is an autosomal recessive lysosomal storage disorder, a mucopolysaccharidosis, characterized by abnormal metabolism of glycosaminoglycans. Major treatable concerns in patients with MS involve C1 to C2 instability, genu valgum, and hip subluxation. Untreated hip subluxation has been shown to predispose to early onset of arthritis of the hip. Early appropriate pelvic osteotomies may restore (improve) load transmission and retard the onset of arthritis. Computed tomographic (CT) measurements can help determine the site and severity of acetabular deficiency, aiding in selection of the appropriate acetabular procedure. Acetabular morphology in MS has not been described in the literature. The purpose of this study was to evaluate morphology (shape) of the acetabulum in MS using two-dimensional (2-D) CT scans.
Methods: To assess the acetabular roof, the acetabular index was measured on anteroposterior radiographs of the pelvis. Various CT measures were used to assess the acetabular anatomy in the axial plane.
Results: The average acetabular index on the anteroposterior radiographs of the pelvis was 33 degrees (average age-matched difference from normal, 12 degrees). Two-dimensional CT (axial cuts) showed that the average acetabular anteversion angle was close to normal, measuring 10.9 degrees. The average anterior acetabular index was 58.8 degrees (average age-matched difference from normal, 10.6 degrees), and posterior acetabular index was 53.8 degrees (average age-matched difference from normal, 3.8 degrees). Calculated axial acetabular index ranged from 90 to 133 degrees (mean, 112.6 degrees; average difference from normal, 14.5 degrees).
Conclusions: Two-dimensional CT of the hip in patients with MS demonstrated a severe dysplasia of the anterior acetabular wall and the roof of the acetabulum, although the acetabular version was normal. Treatment of hip dysplasia in MS should focus on increasing the overall depth of the acetabulum to better contain the femoral head. Two-dimensional CT is recommended before bony acetabular procedures to assess the degree of acetabular deficiencies.
Significance: Computed tomography of the acetabulum is helpful in preoperative decision making and planning before an acetabular procedure in patients with Morquio-Brailsford syndrome.