Cannulated screw fixation in the inverted right angle configuration for femoral neck fractures based on 3D fine anatomical morphology of the femoral head and neck: a preliminary study
10.3760/cma.j.cn115530-20240507-00200
- VernacularTitle:基于股骨头颈部三维精细解剖特征的倒直角构型空心螺钉固定股骨颈骨折的初步研究
- Author:
Changjian LIU
1
;
Peihan LIU
;
Yang HOU
Author Information
1. 大连医科大学附属第一医院创伤骨科，大连 116000
- Keywords:
Femoral neck fractures;
Fracture fixation, internal;
Bone nails;
Inverted right angle configuration;
Anteversion
- From:
Chinese Journal of Orthopaedic Trauma
2024;26(9):768-774
- CountryChina
- Language:Chinese
-
Abstract:
Objective:To explore how to avoid screw in-out-in in fixation of femoral neck fractures with 3 cannulated screws based on analysis of 3D fine anatomical morphology of the head, neck, and proximal end of the femur.Methods:The CT data of the healthy femurs were collected retrospectively of the 22 patients with hip fracture who had been admitted to Department of Orthopaedics and Traumatology, The First Hospital Affiliated to Dalian Medical University from September 2021 to March 2024. There were 12 males and 10 females with an age of (52.5±16.8) years. The CT data of the healthy femurs of the patients were imported into software Mimics 19.0 to establish a 3D model of the proximal femur. The fine anatomy of the head, neck, and proximal end of the femur was measured and analyzed to determine the optimal decentralized arrangement of the 3 cannulated screws at the narrowest medullary cavity along the femoral neck axis. 3D model simulation was conducted to observe and analyze the occurrence of screw in-out-in after fixation of femoral neck fracture with 3 cannulated screws in different configurations. The inclination angle of the posterior superior cortical slope of the femoral neck (i.e. negative anteversion angle) was measured. Fluoroscopy was simulated at the negative anteversion angle to observe the occurrence of in-out-in of the posterior upper screw after fixation of femoral neck fracture with 3 cannulated screws. The efficacy of the optimal configuration and fluoroscopy at the negative anteversion angle was validated in the clinical treatment of 2 patients with femoral neck fracture (one 51-year-old male patient and one 68-year-old female patient).Results:The 3D model of the head, neck, and proximal end of the femur showed that the medullary cavity of the femoral head and neck was not on the same plane of the medullary cavity of the proximal femur, but was offset forward by about 1/4 from the proximal femur [(6.16±0.86) mm]. The narrowest part of the femoral neck medullary cavity was irregular in shape. The most reasonable configuration for the decentralized arrangement of 3 cannulated screws was like an inverted right angle in shape (improved inverted right angle configuration), but not the traditional configuration of an inverted triangle in shape. In 3D model simulation, the traditional inverted triangle configuration with 3 cannulated screws led to occurrence of in-out-in of the posterior upper screw while the improved inverted right angle configuration led to no occurrence of in-out-in of the posterior upper screw. Intraoperative fluoroscopy at the negative anteversion angle (31.02°±3.32°) could be used to detect whether in-out-in of the posterior upper screw occurred or not. In the 2 patients with femoral neck fracture undergoing fixation with 3 cannulated screws in the improved inverted right angle configuration, screw in-out-in was not detected by intraoperative fluoroscopy at the negative anteversion angle or by postoperative CT scan.Conclusions:The fine anatomical morphology of the head, neck, and proximal end of the femur determines that the traditional inverted triangle configuration of cannulated screws in fixation of femoral neck fracture is likely to lead to in-out-in of the posterior upper screw while the improved inverted right angle configuration may effectively reduce the risk of in-out-in of the posterior upper screw. Intraoperative fluoroscopy at the negative anteversion angle can be used to detect timely whether in-out-in of the posterior upper screw occurs or not.
