Abstract
PURPOSE: In this study the course of unstable hips after successful treatment with Fettweis plaster of Paris (POP) is examined. Special focus will be given to age at beginning of treatment and initial hip type. METHODS: The development of 93 unstable hips treated between November 2001 and April 2015 was examined. Inclusion criteria were: 1) unstable hips with successful treatment with Fettweis POP; 2) presence of two pelvic radiographs (12 to 24 months and 24 to 48 months). We analyzed: 1) the initial ultrasound hip type according to Graf; 2) the average age at first and second radiograph; 3) the Tönnis classification: normal findings (< 1 SD), slightly (1 SD to 2 SD) and severely dysplastic hips (> 2 SD). RESULTS: In all, there were 14 hips type D, 41 hips type III and 38 hips type IV. Mean age of the first radiograph was 13.9 months and of the second 28.5 months. The first radiograph showed: (< 1 SD): 36, (1 SD to 2 SD): 34, (> 2 SD): 23 hips, the second radiograph: (< 1 SD): 33, (1 SD to 2 SD): 19, (> 2 SD): 30 hips. With subdivision at the start of treatment at age eight or fewer weeks 2/16 hips (12.5%) and with initiation of the treatment more than eight weeks 22/77 (26.0%) deteriorated. During the course between first and second radiograph a total of 35.7% of initial hip type D, 19.5% of type III and 23.7% of type IV deteriorated. CONCLUSION: Radiograph controls after treatment with Fettweis POP show poorer outcome after delaying the start of treatment more than 8 weeks. These findings were independent of the initial ultrasound hip type. Regular radiograph controls of all hip types treated for unstable hips are justified to detect residual dysplasia. LEVEL OF EVIDENCE: IV.