OBJECTIVETo evaluate the biomechanical changes of balloon inflating and cement filling in avascular necrosis of the femoral head using finite-element analysis.

METHODSThe procedure of percutaneous balloon inflating and cement filling was simulated in fresh specimen of human femoral head. CT scan and three-dimensional reconstruction were used to establish the three-dimensional model of the femoral head. The physiological load was analyzed using three-dimensional finite element model to simulate the load and calculate stress on the hip during walking. Finite element analysis was performed on the avascular necrosis model and balloon inflating and bone cement filling model to measure the Von-Mises force at the top, neck and weight-bearing area of the femoral head. Another 8 fresh specimens of femoral head necrosis of human were obtained to stimulate balloon inflating and bone cement filling procedures, and the displacement of the femoral head under different loads was recorded before and after the procedures.

RESULTSAfter bone cement filling in the necrosis area, the load reduced significantly in the weight-bearing area of the femoral head, and the load distribution became more uniform at the femoral neck and the top of the head. The anti-deformation ability of the necrosis femoral head increased after bone cement filling. The infinite-element analysis and specimen biomedical test showed similar results.

CONCLUSIONPercutaneous balloon inflating and bone cement filling in the necrosis area can change the biomechanics mechanism of the femoral head and neck, improve the supporting capacity under load, and prevent the progression of head collapse.