The potential role of the Alsberg angle as a predictor of lateral growth disturbance of the capital femoral epiphysis in children with developmental dysplasia of the hip treated by closed reduction

Abstract

Purpose: Early diagnosis and prevention of lateral growth disturbance of the capital femoral epiphysis is challenging after treatment for developmental dysplasia of the hip (DDH). The aim of the study was to evaluate the radiographic changes of the Alsberg angle (AA) in normal children and those with DDH, and to assess the role of AA as a potential predictor of lateral growth disturbance of the capital femoral epiphysis.

Methods: AA was measured on the anterior-posterior pelvic radiographs of 1000 normal children ranging in age from one to ten years and in 66 children (92 hips) with DDH treated by closed reduction (CR). A comparative analysis was performed.

Results: In the normal children, mean AA decreased linearly with age, from 76° at age one year to 65° at age ten years, irrespective of gender and laterality. In children with DDH, the average AA was 81.5°(sd 3.9°; 74° to 87°) prior to CR; it was 75.9° (sd 4.5°; 68° to 83°) in normal children of the same age (p < 0.001). Among the 42 children (64 hips) with successfully and uneventfully treated DDH, AA reached normal values between the ages of five and six years. In contrast, children with lateral growth disturbance of the proximal femur physis (24 children, 28 hips) showed significantly higher AA values in comparison with the age-matched controls.

Conclusion: In DDH patients with successful CR, AA could be expected to match normal values in children between the ages of five and six years. On the other hand, AA can be used as an early predictor for lateral growth disturbance of the capital femoral epiphysis.

Level of evidence: Level III.

Keywords: Alsberg angle; avascular necrosis; closed reduction; developmental dysplasia of the hip; lateral growth disturbance.

Fig. 1

The Alsberg angle.

Fig. 2

Changes in the Alsberg angle based on age in normal children (left side and right side).

Fig. 3

Changes in the Alsberg angle in children with developmental dysplasia of the hip (DDH) managed by closed reduction and spica cast immobilization versus normal children (AVN, avascular necrosis).

Fig. 4

Anteroposterior pelvis radiographs showing the changes in the Alsberg angle in a 17-month-old girl with bilateral developmental dysplasia of the hip treated by closed reduction (a). The patient developed type II growth disturbance. At the age of six years, the Alsberg angle was 76° on the left side and 74° on the right side (b); at the age of nine years, it was 78° on the left side and 75° on the right side (c); at the age of 12 years, it was 82° on the left side and 79° on the right side (d).