Study finds, Biomechanical effect of intertrochanteric curve
Intertrochanteric curved varus osteotomy (CVO) has been widely used to remove the necrotic bone away from the weight-bearing portion in the treatment of osteonecrosis of the femoral head (ONFH). The purpose of the study was to evaluate the influence of CVO on the stress reduction in necrotic bone using a finite element analysis (FEA) with different CE angles.

CVO finite element models of the hip joint were simulated with a lesion of 60°. The osteotomy angles were divided into four configurations (15°, 20°, 25°, and 30°), and three types (A, B, and C1) of lesions were established based on the Japanese Investigation Committee (JIC) classification. In addition, two CE angles (18° and 33°) of acetabulum were considered. The maximum and mean von Mises stress were analyzed in terms of the necrotic bone by a physiological loading condition. Moreover, the correlation of the intact ratio measured in 3D and the stress distribution after CVO was analyzed.

--Stress reduction was obtained after CVO. For type B, the CVO angle was 20°, and for type C1, the CVO angle was 30°, if the mean stress level was close to type A (0.61 MPa), as a standard.

--The maximum and mean von Mises stress were higher in the CE angle of 18°models, respectively.

--The intact ratio measured in 3D had a good negative correlation with stress after CVO and had more influence on stress distribution in comparison to other geometric parameters.

A CVO angle of more than 20° was advised for type B, while a CVO angle of more than 30° was safe for type C1. The insufficiency of the weight-bearing section following CVO increases the likelihood of subsequent collapse. Information on clinical outcomes and stress distribution following a CVO could be obtained from the intact ratio.