Does shelf acetabuloplasty influence acetabular growth and remodeling?

BACKGROUND

Shelf acetabuloplasty has the potential to cause iatrogenic acetabular growth arrest, although accelerated acetabular growth has been reported based on plain radiographic evaluations in patients with Legg-Calvé-Perthes disease. Because plain radiographs may be limited in depicting actual acetabular morphology, it is unclear whether there are growth disturbances.

QUESTIONS/PURPOSES: We therefore determined (1) whether focal or generalized acetabular growth stimulation or retardation occurred based on CT analysis in combination with plain radiographic assessment; and (2) whether radiographically assessed femoral head deformity, subluxation, and acetabular dysplasia were associated with residual zonal rim dysplasia of the acetabulum.

METHODS

We examined 14 patients who had undergone shelf acetabuloplasty for "reducible subluxation" and underwent CT scans at a mean 7 years after surgery (range, 3-11 years). We measured radiographic indices reflecting acetabular depth and rim dysplasia on multiplanar reformatted images in 10 radial planes and on plain radiographs and calculated their operation-to-control ratios to assess growth changes. The mean age at surgery was 9.3 years (range, 7-12 years).

RESULTS

We observed generalized accelerated growth in 11 hips and equivocal growth in three. None of the 14 hips showed an abrupt change in acetabular geometry. Despite improved acetabular depth in all hips, eight hips had focal rim dysplasia in the superior zone on CT examinations, and this was associated with a smaller center-edge angle, a greater deformity index, and preexisting acetabular dysplasia.

CONCLUSIONS

Our observations support the notion that shelf acetabuloplasty has a favorable, stimulatory effect on acetabular growth. However, the possible persistence of preexisting zonal rim dysplasia should be considered.