Mechanical effects of valgus osteotomy angle and re-fixation strategies on re-fixation of the femoral neck fracture: a finite element analysis.

This study examined the biomechanical outcomes of osteotomy angles and the internal fixation devices for re-fixation of the femoral neck fracture. The finite element model of femoral neck fracture was initially fixed with three cannulated screws, followed by 10° and 20° valgus osteotomy. The models were re-fixed using sliding hip screw (DHS) + anti-rotation screw (AS) or DHS + medial buttress plate (MBP). Physiological loads were applied to all models. With 10° and 20° valgus osteotomy, the interfragmentary shear stress, sliding distance, and gap decreased, the compressive stress increased. With a further 10° osteotomy angle, the interfragmentary sliding distance in DHS + AS group decreased by 38.4%, and the interfragmentary compressive stress in DHS + MBP group increased by 20.9%. The interfragmentary shear stress and gap showed changes of no more than 10%. For the sliding distance, gap, and shear stress, DHS + AS is slightly superior to DHS + MBP at both osteotomy angle. The Von Mises stress of the internal fixation device for DHS + AS is 22.61% higher than that for DHS + MBP at a 20° osteotomy angle. Both 10° and 20° osteotomy angles enhance the mechanical strength and stability at the fracture site, which may offer potential options for the clinical selection of valgus osteotomy angles. DHS + AS exhibits better mechanical stability but may carry a higher risk of internal fixation failure. Patients treated with DHS + AS may require more cautious postoperative weight-bearing; however, this should be validated in clinical studies. Meanwhile, with the development of bone tissue engineering, the material strength of internal fixation devices may improve, reducing the risk of internal fixation device failure.