Influence of the modified Dunn procedure on the spine–pelvis relationship in children with severe slipped capital femoral epiphysis

BACKGROUND: Slipped capital femoral epiphysis (SCFE) is one of the most severe hip joint diseases in children. It is characterized by the development of unilateral or bilateral deformity of the proximal femoral epimetaphysis of varying degrees. The pronounced deformity of the femoral component of the affected joint leads to pelvic retroversion, decreased lumbar lordosis, increased thoracic kyphosis (TK), and formation of type I (hypolordotic) vertical posture according to the Roussouly classification, contributing to degenerative and dystrophic processes in the lumbosacral spine. At present, no data in the literature present the effect of surgical treatment on frontal and sagittal spine–pelvis relationships in the patients examined. AIM:To performacomparative radiological evaluation of the sagittal spine–pelvis relationship in children with severe SCFE before and after the modified Dunn procedure. MATERIALS AND METHODS:The study included 30 patients (30 hip joints) aged 14–18 years with severe SCFE characterized byaposterior epiphysis displacement of 60° and downward of no more than 10° in one of the joints and no displacement (preslip stage) in the other. All children underwent the modified Dunn procedure on one side and fixation of the epiphysis of the femoral head withacannulated screw on the other side. Before and after surgery, the patients underwent clinical and radiologic examinations. Standing radiographs were used to evaluate lumbar lordosis, TK, pelvic incidence (PI), pelvic tilt (PT), sacral slope (SS), and sagittal vertical axis (SVA). The obtained data were analyzed statistically. RESULTS:At the examination 3–3.5 years after the abovementioned interventions,apronounced increase was noted in the mean PI value, which began to correspond to type III (harmonious) of upright posture according to the Roussouly classification.Achange was noted in the mean values of positional indices PT (decreased) and SS (increased), and pelvic retroversion disappeared. The mean global lumbar lordosis (GLL) and lumbar lordosis increased, which led toadecrease in TK and the mean value of TK. All clinical observations showedasignificant decrease in the mean global sagittal balance index (the sagittal vertical axis (SVA)) and absence of torso imbalance. CONCLUSIONS:After performing the modified Dunn procedure on the one side and fixation of the epiphysis of the femoral head withascrew on the other side, children with severe SCFE demonstrated improvements in all the studied indices of sagittal spine–pelvis ratios. Consequently, the type of vertical posture according to the Roussouly classification changes from type I (hypolordotic) to type III (harmonious), and the probability of degenerative and dystrophic process development in the lumbosacral spine decreases.