Treatment of unstable hips with the Tübingen splint in early postnatal period: radiological mid-term results of 75 hips with mean follow-up of 5.5 years

PURPOSE: For treatment of unstable hips, the Tübingen splint is a treatment option. After the initial treatment, regular radiological follow-up examinations are recommended but there is a lack of long-term outcome studies. Therefore, the further development of unstable hips treated with the Tübingen splint were evaluated. METHODS: From 2004 to 2015 116 patients with 161 unstable hips treated with the Tübingen splint were evaluated. Inclusion criteria were: 1) successfully treated unstable hip (type D, III and IV); 2) pelvic radiographs at the age of one to ≤ two, two to ≤ four and four to ≤ eight years. The acetabular index (ACI) of all and the centre-edge angle (CEA) of the third radiograph were measured and classified according to the Tönnis classification. RESULTS: A total of 53 patients with 75 unstable hips (type D 34 (45.3%), III 33 (44.0%), IV 8 (10.7%)) were included. In comparison of the first, second and third radiograph, an increase of normal findings was seen in 31 (41.3%) to 53 (70.7%) and 60 (80.0%) hips, respectively. However, a decrease of slightly dysplastic hips from 31 (41.3%) to 19 (25.3%) and 14 (18.7%) respectively and severely dysplastic hips from 13 (17.3%) to three (4.0%) and one (1.3%) hip respectively was detected. In comparison of first to second radiograph, 32 hips improved and five hips deteriorated and of second to third radiograph 16 hips improved and six hips deteriorated. The Tönnis classification of ACI compared with CEA showed no significant differences (p = 0.442). CONCLUSION: This study shows a good development of unstable hips treated with the Tübingen splint with mean follow-up 5.5 years. Nevertheless, unexpected deteriorations could be identified. The CEA is an alternative to the ACI. LEVEL OF EVIDENCE: IV