Background: The indication for the use of the Tübingen hip flexion splint is a dysplastic hip without instability. According to current knowledge dysplastic unstable or dislocated hips should be treated with a stable retention device such as a modified Fettweis cast. The aim of this study was to evaluate the treatment effect of the Tübingen hip flexion splint when applied to dysplastic unstable hips (type IIc unstable according to the classification of Graf) and dislocated hips (types D, III and IV according to the classification of Graf) within the first week of life.
Patients and methods: All newborns with an unstable hip type IIc or worse detected by ultrasound in the first week of life were treated with a Tübingen hip flexion splint. A prospective cohort trial was performed between November 2007 and December 2010. The initial hip type according to the ultrasound classification of Graf, the start and the duration of treatment with the Tübingen hip flexion splint as well as the rate of success were evaluated. Due to the small number of patients non-parametric tests were used for statistical analysis.
Results: A total of 50 dysplastic unstable or dislocated hips in 42 newborns were treated with the Tübingen hip flexion splint. The distribution of pathological hip types was 6 type IIc unstable, 33 type D, 10 type III and 1 type IV. Therapy was started on average on day 3.5 (range 1-8 days) of life and 49 out of 50 hips were successfully treated with the Tübingen hip flexion splint. Solely the type IV hip could not be reduced in the Tübingen hip flexion splint. Thus 98% of the dysplastic unstable or dislocated hips were successfully converted into type I hips with an α-angle of more than 64° in the splint. The mean time for achieving an α-angle ≥ 64° was 51.6 ± 18.9 days (range 21-87 days). No statistically significant relationship was found between the duration of therapy and the time when treatment was started, early or late within the first week of life (p = 0.152). Furthermore, no correlation was detected between the duration of therapy and the initial hip type determined by ultrasound (p = 0.886). In all successfully treated cases therapy could be discontinued during the exponential part of Tschauner's maturation curve of hip development.
Conclusion: When recognized within the first week of life dysplastic unstable hips (type IIc unstable according to the classification of Graf) and dislocated hips with a cranially dislocated cartilage roof (types D and III according to the classification of Graf) can be successfully treated with the Tübingen hip flexion splint provided that the parents show good compliance concerning the treatment regimen.