To determine the effect of the femoral head ossific nucleus on the development of avascular necrosis (AVN) after reduction of a dislocated hip. We included consecutive patients treated for a dislocated hip secondary to DDH with either closed or open reduction under the age of 30 months (mean, 9.6□4.8) in this retrospective cohort study. 85 patients or 100 hips were included. Radiographs were analysed for the presence of the ossific nucleus at the time of hip reduction, and for the presence of AVN at 9.2□3.4 years after hip reduction by 3 blinded assessors. There was no significant effect of the femoral head ossific nucleus on the development of osteonecrosis, with 16/40 (40%) cases of osteonecrosis in infants with an ossific nucleus absent compared with 18/60 (30%) in the group with an ossific nucleus (adjusted relative risk = 0.83; 95% CI = 0.38 to 1.83; p=0.65). When only radiographic changes of grade II or worse were considered osteonecrosis, the association remained statistically insignificant (adjusted relative risk = 0.84; 95% CI = 0.35 to 2.00; p=0.69). Our study reports the longest follow-up addressing the question of a potential protective effect of the ossific nucleus on the development of AVN. We could not demonstrate such an effect. Strategies aimed at delaying the treatment of a dislocated hip in the absence of the ossific nucleus cannot be recommended as they will not affect the risk for subsequent AVN.Purpose
Conclusion
