Untreated residual subluxation after early closed reduction for developmental dislocation of the hip (DDH) leads to early degenerative osteoarthritis. The aim of our study was to investigate the role of early surgical timing and its indications.
Thirty-six patients (48 hips) with untreated residual subluxation after closed reduction who had serial follow-up radiographs until they had reached skeletal maturity were retrospectively reviewed. The average age at closed reduction was 1.6 years and at the last follow-up 13.8 years. The last radiographs were evaluated according to the Severin classification: Severin grades I and II were defined as satisfactory and Severin grades III and IV as unsatisfactory. Several measurements of the acetabular index (AI), Reimer's index (RI), center edge angle of Wiberg (CE angle) and orientation of the sourcil of the acetabulum were evaluated.
The satisfactory group comprised 18/48 hips (37%), whereas the unsatisfactory group comprised 30/48 hips (63%). The average RI in the unsatisfactory group was significantly worse than that in the satisfactory group at the age of ≥3-4 years, as was the average CE angle at the age of ≥4-5 years and AI at the age of ≥5-6 years. As remodeling occurs over time, some subluxations diagnosed at age of 2-3 years developed into normal hips. At 3-4 years, 42 hips were still subluxed; 71% of these had unsatisfactory final Severin grades. At 4-5 years, 30 hips were still subluxed; 87% of these had unsatisfactory Severin grades (III and IV). Very little remodeling after the age of 5 years. Eighteen/18 hips with (34.4% ± 4.5% vs 43.0% ± 4.6%, P < 0.00) RI >38% at the age of 3-4 years fell into the unsatisfactory (21.0° ± 5.5° vs 10.6° ± 5.2°, P < 0.01) group. In addition, 26/30 hips with RI >33% at the age of 4-5 years were in the unsatisfactory group, as were 26/26 hips with upward sourcil orientation.
To avoid early osteoarthritis, surgery correction of residual subluxation is recommended when the RI >38% at the age of 3-4 years or the RI >33% with the sourcil upward at the age of 4-5 years.