Free bone fragments are associated with the development of heterotopic ossification after hemiarthroplasty for femoral neck fracture: a retrospective observational study.

Purpose: Heterotopic ossification (HO) can occur after hemiarthroplasty (HA) for femoral neck fractures (FNF). This study aimed to investigate the frequency and factors contributing to the development of HO after HA.

Methods: The study included data from 92 of 183 patients (26 male and 66 female) who sustained FNF and underwent HA between April 2019 and January 2022. HO was identified on postoperative radiographic images. Patient background, operative duration, blood loss, and presence of free bone fragments immediately after surgery were compared between the HO and non-HO groups. Statistical analyses included the independent-sample t-test for continuous variables and the chi-squared test for categorical variables. A multivariate logistic regression analysis was performed using HO as an objective variable.

Results: HO occurred in 50 of the 92 (54%) patients. There were no statistically significant differences in patient backgrounds. Univariate analysis revealed significantly longer mean operative duration and greater blood loss in the HO group. Free bone fragments in the immediate postoperative period were observed in 29 of 50 (58%) patients in the HO group and in 3 of 42 (7.1%) patients in the non-HO group, a statistically significant difference. Logistic regression analysis revealed that the presence of free bone fragments was an independent explanatory factor for HO development.

Conclusion: The presence of free bone fragments immediately after surgery may be significantly associated with the development of HO. Therefore, it is necessary to sufficiently remove such fragments during surgery because they may trigger HO.