Abstract
Background and purpose — There are few studies on overgrowth of the affected limb after treatment of developmental dysplasia of the hip (DDH). We investigated the incidence of overgrowth and its risk factors in DDH patients.Patients and methods — 101 patients were included in this study. Overgrowth was defined by 2 criteria: when the height of the femoral head of the affected side was higher than that of the contralateral side by more than 10 mm, or by more than 15 mm. The potential risk factors of distinct overgrowth were retrospectively examined using multivariable analysis.Results — When overgrowth was defined as femoral head height difference (FHHD) > 10 mm, its incidence was 44%, and only femoral osteotomy was identified as a significant risk factor with a relative risk (RR) of 1.6 (95% confidence interval [CI] 1.0–2.5). When overgrowth was defined as FHHD > 15 mm, its incidence was 23%, and femoral osteotomy was identified as the only significant risk factor with an RR of 2.3 (CI 1.2–4.5). Overgrowth developed more frequently in patients who underwent femoral osteotomy at the age of 2 to 4 years (87%) than in the others (46%) (p = 0.04).Interpretation — Overgrowth of the affected limb is common in DDH patients. Patients who underwent femoral osteotomy, especially at the age of 2 to 4 years, may require careful follow-up because of the substantial risk for overgrowth.
Highlights
We investigated the incidence of overgrowth and its risk factors in developmental dysplasia of the hip (DDH) patients
When overgrowth was defined as femoral head height difference (FHHD) > 10 mm, its incidence was 44%, and only femoral osteotomy was identified as a significant risk factor with a relative risk (RR) of 1.6 (95% confidence interval [CI] 1.0–2.5)
When overgrowth was defined as FHHD > 15 mm, its incidence was 23%, and femoral osteotomy was identified as the only significant risk factor with an RR of 2.3 (CI 1.2–4.5)
Summary
LLD was determined on standing anteroposterior radiographs of the hip by measuring the femoral head height difference (FHHD) at skeletal maturity or at the time of intervention for overgrowth (Figure 1) (Friberg 1983). To evaluate deformity of proximal femur, osteonecrosis was classified according to Bucholz–Ogden criteria (Roposch et al 2012), and the widest diameter of the femoral head was measured at skeletal maturity or just before the intervention for overgrowth. In the subgroup of patients who underwent a single femoral or pelvic osteotomy, the association between age at osteotomy and development of distinct overgrowth was analyzed. The association between the AI and center–head distance discrepancy (CHDD) (Chen et al 1994) around 3 years of age and development of overgrowth was analyzed in these patients (Figure 2).
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