Coxa magna following surgical treatment of congenital hip dislocation

We studied coxa magna after operative treatment of congenital dislocation of the hip, including incidence, relationship to treatment, and influence of coxa magna on the acetabulum. Coxa magna was defined as a femoral head with a horizontal diameter at least 15% greater than the symmetrical position on the opposite side. Coxa magna developed in 16 hips (33%). The mean increase was 20.9% (range 15-30%). Three factors correlated with coxa magna: femoral osteotomy (100%), open reduction (75%), and operation at a younger age (mean 15.6 vs. 35.8 months). Four of the 16 hips developed coxa magna following Type 1 avascular necrosis; no other growth deformities appeared. At follow-up, the acetabular indices and the center edge angles were not statistically different between the coxa magna and the control groups. One must avoid confusing coxa magna with hip subluxation or inadequate reduction, of which the latter requires appropriate treatment. Coxa magna gives a good hip if a concentric, congruous reduction is obtained, providing the acetabulum has enough growth potential for remodeling.