Risk factors for avascular necrosis after closed hip reduction in developmental dysplasia of the hip.

Background. Avascular necrosis of the femoral head occurring after surgery for developmental dysplasia of the hip can negatively affect the long-term prognosis of the involved hip. The purpose of our study was to evaluate a number of clinical and radiological risk factors for AVN after non-operative treatment of DDH. Material and methods. Clinical data and radiographs of 77 patients (103 hips) treated for DDH by closed reduction followed by cast immobilization were reviewed retrospectively. The average age at the time of reduction was 16 months (range 4 to 28), and the average final follow-up was at age 22.4 years (range 13 to 47). The Kalamchi and MacEwen classification system was used to evaluate AVN. Results. Avascular necrosis was found in 35.9% of the treated hips (37 cases). Comclusions. We established the impact of several kinds of radiological and clinical data on the incidence and severity of AVN. In our analysis the degree of initial dislocation (Tönnis classification) and age at the onset of treatment are important risk factors for AVN. The presence and size of the ossific nucleus, the use and duration of preliminary traction, previous treatment with Frejka pillow or Pavlik splint, and lateralization were not associated with the incidence and severity of ischemic necrosis.