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

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

目的基于CT三维重建分析股骨头颈部及股骨近端的精细解剖形态,探讨3枚空心螺钉固定股骨颈骨折术中如何避免后上方螺钉in-out-in。方法回顾性收集2021年9月至2024年3月期间大连医科大学附属第一医院创伤骨科收治的22例髋部骨折患者健侧股骨CT数据。男12例,女10例;年龄(52.5±16.8)岁。将患者健侧股骨CT数据导入Mimics19.0软件,建立股骨近端3D模型,测量并分析股骨头颈部及股骨近端的精细解剖,确定股骨颈轴位髓腔最狭窄处3枚空心螺钉分散排布的最佳构型。3D模型模拟分析不同构型3枚空心螺钉固定股骨颈骨折后上方螺钉in-out-in的发生情况。测量股骨颈后上方皮质斜面倾斜角度(即负前倾角),模拟负前倾角位透视,观察3枚空心螺钉固定股骨颈骨折后上方螺钉发生in-out-in的情况。并在2例股骨颈骨折患者(1例为51岁男性患者,另1例为68岁女性患者)的临床治疗中验证最佳构型与负前倾角位透视。结果3D模型显示:股骨头颈部髓腔与股骨近端髓腔并非同一平面,而是较股骨近端向前偏移1/4左右,偏移距离为(6.16±0.86)mm;股骨颈髓腔最狭窄处为不规则形态,3枚空心螺钉分散排布最合理构型为接近倒直角形态(改良倒直角构型),而不是传统倒三角构型。3D模型模拟传统倒三角构型置入3枚螺钉,后上方螺钉发生in-out-in;而模拟改良倒直角构型置入3枚螺钉,后上方螺钉未发生in-out-in。术中采用负前倾角(31.02°±3.32°)位透视可以发现后上方螺钉是否发生in-out-in。2例股骨颈骨折患者均采用改良倒直角构型3枚空心螺钉固定,术中负前倾角位透视及术后CT扫描均未发现螺钉in-out-in。结论股骨头颈部及股骨近端的精细解剖形态决定了传统倒三角构型空心螺钉固定股骨颈骨折时后上方螺钉易发生in-out-in,改良倒直角构型3枚空心螺钉固定能有效降低后上方螺钉in-out-in的发生风险。术中采用负前倾角位透视可以及时发现后上方螺钉是否发生in-out-in。

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.