A comparison of the biomechanical effects of opening and closing wedge varus osteotomies in Perthes' disease.

Varus femoral osteotomy is a commonly employed surgical method of effecting containment in the management of Perthes' disease. This can be achieved by performing either an opening lateral wedge or a closing medial wedge osteotomy. The effects of these two techniques on the biomechanical interrelationships about the involved hip were compared using a three-dimensional computer simulation. Both procedures lead to femoral shortening and reduce the moment capacity of the hip abductors. The shortening effect and consequent leg length discrepancy are greater for the closing wedge osteotomy than for the opening wedge procedure. Pelvic obliquity compensation, likely to be greater for a closing wedge osteotomy, provides a beneficial increase in femoral head coverage but at the cost of a further reduction in the hip abductor moment capacity.