ABNORMAL SHAPE OF THE HIP JOINT WITHIN THE FIRST YEAR OF LIFE – A PREDICTOR FOR POOR OUTCOME OF RELOCATIVE SURGERY

Abstract

Introduction: Although hip dislocation is of little functional importance concerning walking ability in most spina bifida patients, relocative surgery may be considered to improve sitting balance or gait pattern in some. The risk for re-dislocation may provide further information to be considered in decision making.

Material and methods: A retrospective cohort study included all patients with spina bifida of our unit in which dislocated hip joints were surgically relocated between 1983 and 2000. This procedure including femoral and pelvic corrective surgery, open reduction and soft tissue procedures if necessary, was carried out as a routine in all hip dislocations because hip stability was regarded beneficial for function. The patients were grouped according to the presence of hip dislocation or subluxation: A) within the first year of life, B) later. Group A consisted of 8 (3m, 3f), group B of 10 patients (5m, 5f). In group A 11 (5r, 6l), and in group B 13 hips (7r, 6l) were treated. The neurological levels did not differ between the groups. The hip subluxation or dislocation was diagnosed at age 0.3 years (+0.5 / -0.2 years) in group A and 8.7 years (+6.8 / -5.6 years) in group B.

The first corrective hip intervention was done at age 4.6 years (+3.4 / -1.9 years) in group A, at age 9.5 years (+6.6 / -6.2 years) in group B. The follow-up time was 6.8 years (+6.2 / -6.5 years) in group A and 5.0 years (+6.7 / -4.8 years) in group B (p = 0.42) (mean values, range). Results: In group A (n=11 hips) only 1 hip remained stable located. Altogether 14 re- dislocations occurred and 10 additional re-locative operations were performed (some hips were operated on several ocasions). Seven hips were dislocated at final control. In group B (n=13 hips) 10 hips remained stable located, and 3 hips re-dislocated. One re-operation was successful, another one failed. Hence 2 hips were dislocated at final control. The difference between group A and B were statistically significant (p = 0.008). Discussion: Hip deformity present already within the first year of life is a predictor for a poor outcome of relocating surgery, whereas such surgery has a good prognosis in deformities developed later in life. This may be even more important as it has been shown that muscle balance is not a problem .