Preoperative computed tomography morphological characteristics of displaced femoral neck fractures

Abstract

Objectives: This study aims to investigate the morphological classification of preoperative computed tomography (CT) in patients with femoral neck fracture treated by hollow nail.

Patients and methods: Between January 2014 and December 2021, a total of 34 patients (23 males, 11 females; mean age: 51.97±11.80 years; range, 18 to 85 years) with displaced femoral neck fracture according to Garden classification (Stage Ⅲ-Ⅳ) were included in this study. The preoperative CT data of the patients with femoral neck fractures treated with a hollow screw were collected. According to the morphological characteristics of femoral neck fracture, the slope angle of CT, three-dimensional reconstruction, the lateral upward angle of coronal position, the opening angle, the head-back tilt angle and the head backward distance ratio in horizontal position were measured.

Results: According to the study of CT morphology, femoral neck fracture was classified into varus separated type 1, varus separated type 2, and valgus impacted type. The mean slope angle was 52.95°±10.36°, the mean lateral upward angle was 15.45°±5.59°, the mean head-back tilt angle was 33.89°±11.20°, the mean head backward distance ratio was 0.822±0.114, and the mean forward opening angle was 23.82°±6.11° in varus separated type 1. The mean slope angle was 65.72°±3.36°, the mean head-back tilt angle was 18.44°±5.18°, and the mean head backward distance ratio was 0.460±0.181 in varus separated type 2. The mean head-back tilt angle was 18.65°±12.54° and the mean head backward distance ratio was 0.362 in valgus impacted type. For varus separation type, the proportion of male patients (93.75%), high-energy injuries (56.25%), and Garden type 4 fractures (87.50%) was higher than that of valgus impacted type (38.89%, 11.11%, and 5.56%, respectively), indicating a statistically significant difference (p<0.01). The amount of intraoperative blood loss, head-back tilt angle, and backward distance ratio of patients with varus separation were higher than those of patients with valgus impaction, indicating a statistically significant difference (p<0.01).

Conclusion: The morphology of preoperative CT of femoral neck fracture treated with hollow screw can be divided into varus separated type and valgus impacted type. This fracture classification can guide the intraoperative reduction and improve the quality of reduction. The functional exercise is reasonably guided by evaluating prognosis according to the classification characteristics.