Anti-Shortening Screw for the Prevention of Postoperative Shortening in Displaced Femoral Neck Fractures: A Retrospective Cohort Study.

Background: Early femoral neck shortening after femoral neck system (FNS) fixation for displaced femoral neck fractures can occur in 22.3%-39.1% of cases, leading to decreased hip joint function. This study aimed to investigate the effectiveness of using an anti-shortening screw (ASS) in FNS fixation to prevent postoperative femoral neck shortening in displaced femoral neck fractures.

Methods: We retrospectively analyzed 106 cases of displaced femoral neck fractures treated with FNS at the Hospital from April 2020 to April 2023. Patients were divided into two groups based on the use of an ASS: the traditional group and the ASS group, each consisting of 53 cases. The ASS group was age-matched with the traditional group treated during the same period without an ASS. The study variables included age, sex, body mass index (BMI), smoking and drinking history, injury mechanism, side of injury, fracture type, surgical time, intraoperative blood loss, Harris Hip Score (HHS) at the final follow-up, radiographic assessment (femoral neck shortening), and complications (infection, femoral head necrosis, nonunion, and secondary surgery). Statistical analysis was performed using SPSS software, with continuous and categorical variables analyzed using appropriate parametric (t-test) and nonparametric (Mann-Whitney U test) tests, and chi-square or Fisher's exact tests, respectively. A p-value <0.05 was considered significant.

Results: There were no significant differences in background characteristics between the traditional and ASS groups. The shortening distance at postoperative day 1 did not differ significantly between the two groups (0 vs. 0 mm, p = 0.120). However, at 1, 3 months, and 1 year postoperatively, the femoral neck shortening in the ASS group was significantly less than that in the traditional group (1 month: 2.3 vs. 3.1 mm, p = 0.007; 3 months: 2.6 vs. 3.5 mm, p = 0.005; 1 year: 2.6 vs. 3.5 mm, p = 0.002). The ASS group also had a significantly lower shortening distance during the fracture healing process (0.9 vs. 2.7 mm, p = 0.005). The incidence of moderate to severe shortening (≥5 mm) at 1 year postoperatively was lower in the ASS group compared with the traditional group (15.1% vs. 37.7%, p = 0.001). The ASS group had a longer surgical time (63.0 ± 13.4 vs. 73.0 ± 23.2 min, p = 0.008) and a higher HHS (90.7 vs. 94.8, p = 0.008). There was no significant difference in fracture healing time or postoperative complications between the two groups. The traditional group had 3.8% cutouts, 7.5% nonunions, 5.7% avascular necrosis, and 7.5% secondary hip replacements. The ASS group saw 0% cutouts, 1.9% nonunions, 3.8% avascular necrosis, and 3.8% hip replacements. No significant differences in complication rates (p > 0.05).

Conclusion: The use of an ASS in FNS fixation for displaced femoral neck fractures can reduce the degree of postoperative shortening and improve hip joint function.