To investigate the effect of neck-shaft angle in surgical hip dislocation combined with femoral neck rotational osteotomy in the treatment of osteonecrosis of the femoral head and to combine with finite element analysis.

BACKGROUND

The Neck-shaft Angle (NSA) is a reliable predictor of the outcome of internal fixation for femoral neck fractures. Surgical Hip Dislocation Combined with Femoral Neck Rotational Osteotomy (SHD-FNRO) is an effective surgical method for treating femoral head necrosis. However, the potential role of NSA in predicting the outcomes of hip preservation after SHD-FNRO has not been explored.

OBJECTIVE

This study aims to investigate the value of NSA in predicting the outcomes of hip preservation after SHD-FNRO by comparing the results among different patients with osteonecrosis of the femoral head (ONFH) who were treated with SHD-FNRO.

METHODS

We retrospectively analyzed clinical data from 33 patients (33 hips) who underwent SHD-FNRO at our hospital between January 2017 and December 2021. Based on the outcome of hip preservation, patients were divided into two groups: group A (successful hip preservation) and group B (failed hip preservation). Statistical analysis was performed to evaluate any differences between these groups. Additionally, three-dimensional models with varying NSA values were created to analyze changes in maximum displacement and stress on the osteotomy surface.

RESULTS

During a mean follow-up period of approximately 40 months, successful hip preservation was achieved in 26 patients while 7 patients experienced failure. There was a statistically significant difference in NSA between these two groups (P < 0.05). Biomechanical analysis demonstrated a close relationship between NSA and postoperative biomechanical changes.

CONCLUSION

The size of NSA is closely associated with the success rate of hip preservation when treating osteonecrosis of the femoral head using SHD-FNRO. Therefore, careful attention should be given to selecting an appropriate osteotomy surface that can adjust NSA size effectively, thus achieving better outcomes for hip preservation.