Factors influencing the outcome of hip preservation in femoral head necrosis treated with rotational osteotomy via the base of the femoral neck, combined with finite element analysis

Abstract

Abstract Background :The tip-apex distance (TAD), calcar referenced tip-apex distance (Cal-TAD), and neck-shaft angle (NSA) demonstrate reliability in predicting outcomes following internal fixation of femoral neck fractures. However, the potential influence of TAD, Cal-TAD, and NSA on predicting hip preservation outcomes through trans-trochanteric rotational osteotomy at the base of the femoral neck for treating femoral head necrosis remains unexplored. Purposes: To assess the prognostic value of TAD, Cal-TAD, and NSA for hip preservation outcomes following rotational osteotomy at the base of the femoral neck in conjunction with finite element analysis, we compared the outcomes of different patients who underwent this procedure for femoral head necrosis. Methods: The clinical data of 33 patients (33 hips) who underwent rotational osteotomy at the base of the femoral neck between January 2017 and December 2021 in our hospital were retrospectively analyzed. TAD, Cal-TAD, and NSA were measured on immediate postoperative radiographs, and the patients were categorized into Alive and Dead groups based on hip preservation outcomes for statistical analysis. Additionally, three-dimensional models with varying neck shaft angles were constructed to examine changes in maximum displacement of the femoral head and stress on the osteotomy surface. Results:During a mean follow-up period of approximately 40 months, 26 patients survived while 7 patients experienced hip preservation failure. The differences in age, TAD, and Cal-TAD between the two groups were not statistically significant (P>0.05), whereas NSA exhibited statistical significance (P<0.05). Biomechanical analysis revealed a close association between NSA and postoperative biomechanical changes. Conclusion: When performing rotational osteotomy at the base of the femoral neck for the treatment of femoral head necrosis, both TAD and Cal-TAD exhibit negligible impact on hip preservation outcomes, while the size of NSA significantly influences surgical success rates. Therefore, meticulous attention should be given to precise measurement and adjustment of NSA during surgery in order to achieve optimal surgical outcomes.