Early treatment with the von Rosen splint for neonatal instability of the hip is safe regarding avascular necrosis of the femoral head: 229 consecutive children observed for 6.5 years

Abstract

Background and purpose: Avascular necrosis of the femoral head (AVN) is a complication in treatment of developmental dysplasia of the hip (DDH). We evaluated the risk of AVN after early treatment in the von Rosen splint and measured the diameter of the ossific nucleus at 1 year of age.

Children and methods: All children born in Malmö, Sweden, undergo clinical screening for neonatal instability of the hip (NIH). We reviewed 1-year radiographs of all children treated early for NIH in our department from 2003 through 2010. The diameter of the ossific nucleus was measured, and signs of AVN were classified according to Kalamchi-MacEwen. Subsequent radiographs, taken for any reason, were reviewed and a local registry of diagnoses was used to identify subsequent AVN.

Results: 229 of 586 children referred because of suspected NIH received early treatment (age ≤ 1 week) for NIH during the study period. 2 of the 229 treated children (0.9%, 95% CI: 0.1-3.1) had grade-1 AVN. Both had spontaneous resolution and were asymptomatic during the observation time (6 and 8 years). 466 children met the inclusion criteria for measurement of the ossific nucleus. Neonatally dislocated hips had significantly smaller ossific nuclei than neonatally stable hips: mean 9.4 mm (95% CI: 9.1-9.8) vs. 11.1 mm (95% CI: 10.9-11.3) at 1 year (p < 0.001).

Interpretation: Early treatment with the von Rosen splint for NIH is safe regarding AVN. The ossification of the femoral head is slower in children with NIH than in untreated children with neonatally stable hips.

Figure 1.

Measurement of the maximum diameter of the ossific nuclei.

Figure 2.

A. A girl with fragmentation of the left ossific nucleus (grade-1 AVN) at 12-month follow-up. Treatment had been initiated at 2 days of age for left-sided instability. B. Normal appearance of the femoral head at 3 years. C. Normal hip development at final check-up. The observation time was 5 years 7 months.

Figure 3.

A. A boy with mottled appearance of the left ossific nucleus (grade-1 AVN) at 12-month follow-up. Treatment had been initiated at 2 days of age for left-sided dislocation (Barlow-positive). B. Normal appearance of the femoral head at 8 years.

Figure 4.

Flow chart detailing inclusion of patients in the study. Assessment of AVN was performed by review of 1-year and subsequent radiographs (Kalamchi-MacEwen grading), hospital files, and a diagnosis registry to a mean observation time of 6.5 years.

Figure 5.

A higher degree of neonatal instability was associated with a smaller ossific nucleus at 12 months. Treatment differed between these groups (red dots). Hips with a positive Ortolani test (i.e. dislocated in resting position) had smaller ossific nuclei than hips with a positive Barlow test (i.e. resting in the acetabulum but dislocatable) at 12 months. All these hips had 12 weeks of treatment (blue dots, subgroup analysis of dislocated hips). (n denotes the number of hips in each group. Error bars represent the 95% CI of the mean).