Natural history of type III growth disturbance after treatment of developmental dislocation of the hip.

Background: Type III growth disturbance (T3GD) following reduction for developmental dysplasia of the hip (DDH) is a relatively rare, but potentially devastating complication. This study evaluated the long-term outcomes of patients treated for DDH who developed a T3GD hip compared to those who didn't, with an emphasis on possible risk factors.

Methods: A case-control design was used. All radiographs of a consecutive set of patients with DDH were evaluated. Twenty-two patients (29 hips) developed T3GD. The control group consisted of 57 patients (72 hips) without any sign of growth disturbance. Variables examined included age at reduction, type of reduction and serial radiographic parameters reflecting pre- and post-reduction status. Average age at final follow up was 26 years in the T3GD group and 34 years in the control group.

Results: Evidence of T3GD was first noticed radiographically at 11 months after reduction and healing of the epiphysis occurred an average of 8.5 months later. Univariate analysis demonstrated no increased risk of T3GD related to age at presentation, presence or absence of the ossific nucleus, type of reduction, initial acetabular index or Smith's centering ratios. However, the Tönnis grade was significantly associated with an increased risk of T3GD. Tönnis grade 4 hips (high-degree dislocations) had 3.43 times greater risk of developing T3GD compared to those with lower dislocations. At maturity, 90% of the T3GD hips were classified as Severin III/IV, compared to 35% of the controls. At last follow-up, 7 of the 29 T3GD hips (32%) had undergone total hip replacement at an average age of 39 years (range 19 to 57 years).

Conclusions: T3GD remains the most severe and devastating complication after treatment of DDH in children. In most cases, poor acetabular development and flattening of the femoral head lead to early degenerative changes in the hip joint. The risk increases in high-degree dislocations, independent of the treatment performed.