# The effect of fully threaded cannulated screws in sliding fixation of femoral neck fractures: a retrospective study

## TL;DR

This study found that fully threaded cannulated screws may reduce complications like femoral neck shortening and osteonecrosis in femoral neck fracture patients compared to partially threaded screws.

## Contribution

The study provides empirical evidence comparing fully and partially threaded cannulated screws in femoral neck fracture fixation, highlighting reduced complication rates with fully threaded screws.

## Key findings

- Fully threaded cannulated screws showed significantly lower rates of osteonecrosis of the femoral head (8.2% vs 21.3%) and femoral neck shortening (8.2% vs 25%) compared to partially threaded screws.
- Subgroup analysis revealed higher complication rates in displaced fractures and Pauwels III fractures compared to non-displaced and Pauwels I–II fractures.

## Abstract

The purpose of this study was to compare the clinical efficacy of fully-threaded cannulated screws (FCS) and partially-threaded cannulated screws (PCS) in femoral neck fractures (FNFs).

This retrospective study included 141 patients with FNFs treated with cannulated screw internal fixation between January 2019 and December 2023. Based on the implant type, patients were allocated into two groups: the FCS group (n = 61) and the PCS group (n = 80). Baseline demographic and clinical characteristics were collected and compared between the two groups, including age, sex, body mass index (BMI), comorbidities and fracture classification. The primary outcome measure was the incidence of postoperative complications at final follow-up, including femoral neck shortening, osteonecrosis of the femoral head (ONFH), nonunion, and internal fixation failure. The secondary outcomes included the following measures: the Garden’s alignment index and surgical data.

A total of 141 patients with FNF were enrolled in this study, comprising 80 in the PCS group and 61 in the FCS group. The cohort had a mean age of 44.18 ± 12.5 years, with 87 (61.7%) males and 54 (38.3%) females. Based on preoperative imaging, 84 (59.6%) of the fractures were classified as displaced. The FCS group demonstrated significantly lower rates of both ONFH (8.2% vs 21.3%, p = 0.034) and femoral neck shortening (8.2% vs 25%, p = 0.010) compared with the PCS group. No statistically significant differences were observed in nonunion (4.9% vs 6.3%, p = 0.735) or internal fixation failure rates (0% vs 3.8%, p = 0.126). Subgroup analysis demonstrated significantly higher rates of ONFH (22.6% vs 5.3%, p = 0.005) and femoral neck shortening (26.2% vs 5.3%, p = 0.001) in displaced (Garden III–IV) fractures compared with non-displaced fractures, as well as elevated complication rates in Pauwels III fractures versus Pauwels I–II fractures (ONFH: 19.8% vs 5.0%, p = 0.029; femoral neck shortening: 21.8% vs 7.5%, p = 0.045).

Compared with conventional PCS, FCS for FNF fixation achieves comparable union rates while showing potential advantages in reducing postoperative complications such as femoral neck shortening and ONFH.