Objective: To analyze the reasons and the influence of internal fixation about the guide pin eccentricity of helical blade during proximal femoral nail anti-rotation (PFNA) internal fixation for femoral intertrochanteric fractures.
Methods: A retrospective analysis of the intraoperative imaging data of 175 patients with femoral intertrochanteric fractures, who underwent closed reduction and PFNA internal fixation between January 2018 and January 2020, was performed. There were 76 males and 99 females with an average age of 79.8 years (mean, 61-103 years). The internal between admission and operation was 12-141 hours (median, 32 hours). According to AO/Orthopaedic Trauma Association (AO/OTA) classification, the fractures were rated as type 31-A1 in 64 cases and type 31-A2 in 111 cases. In the intraoperative fluoroscopy image by C-arm X-ray machine, the caputcollum-diaphysis (CCD) was measured after closed reduction and internal fixation, respectively; the angles between the center line of the head nail hole and the axis of proximal nail and between the axis of guide pin and proximal nail were measured, and the difference between the two angles was evaluated; the quality of fracture reduction was evaluated according to the alignment of the medial cortex, anterior cortex of the head and neck bone block, and femoral shaft cortex; the position of the helical blade in the femoral head was evaluated according to the Cleveland method.
Results: The CCDs of proximal femur were (134.6±6.8)° after closed reduction and (134.9±4.3)° after internal fixation. There was no significant difference between pre- and post-internal fixation ( t=0.432, P=0.766). The angles between the center line of the head nail hole and the axis of proximal nail and between the axis of guide pin and proximal nail were (125.4±2.44)° and (126.3±2.3)°, respectively, showing significant difference ( t=2.809, P=0.044). The difference between the two angles was (0.8±2.2)°. The guide pin eccentricity of helical blade occurred in 47 cases. After tapping the helical blade along the eccentric guide pin, 10 cases had fracture reduction loss, and 5 cases had a poor position of the helical blade in the femoral head.
Conclusion: During PFNA internal fixation, a variety of reasons can lead to the eccentric position of the guide pin of helical blade, including unstable fracture, soft tissue inserted, severe osteoporosis, mismatched tool, and fluoroscopic imaging factors. It is possible that the fracture end would be displaced again and the helical blade position may be poor when knocking into the helical blade along the eccentric guide pin. During operation, it should be judged whether the direction of the guide pin needs to be adjusted according to the eccentric angle.
目的: 探讨股骨近端防旋髓内钉（proximal femoral nail anti-rotation，PFNA）治疗老年股骨转子间骨折术中螺旋刀片导针偏心化原因及其对骨折内固定的影响。.
方法: 回顾性分析 2018 年 1 月—2020 年 1 月接受闭合复位 PFNA 内固定的 175 例股骨转子间骨折患者的术中影像资料。男 76 例，女 99 例；年龄 61～103 岁，平均 79.8 岁。入院至手术时间为 12～141 h，中位数 32 h。骨折国际内固定研究协会/美国骨创伤协会（AO/OTA）分型：31-A1 型 64 例，31-A2 型 111 例。在术中 C 臂 X 线机透视图像上，分别测量骨折闭合复位后与内固定后股骨近端颈干角（caputcollum-diaphysis，CCD）；头钉孔中轴线及螺旋刀片导针分别与髓内钉近段轴线的夹角，并计算两角度差值；根据头颈骨块内侧皮质、前侧皮质与股骨干皮质对位情况，评价骨折复位情况；根据 Cleveland 的方法评价螺旋刀片在股骨头内位置。.
结果: 术中骨折闭合复位后，股骨近端 CCD 为（134.6±6.8）°，内固定后为（134.9±4.3）°，内固定前、后比较差异无统计学意义（ t=0.432， P=0.766）。头钉孔中轴线、螺旋刀片导针与髓内钉近段轴线夹角分别为（125.4±2.4）° 和（126.3±2.3）°，差异有统计学意义（ t=2.809， P=0.044）；两者差值为（0.8±2.2）°。术中 47 例螺旋刀片导针发生偏心化，沿偏心化导针敲入螺旋刀片后 10 例发生骨折复位丢失、5 例螺旋刀片在股骨头内位置欠佳。.
结论: PFNA 内固定术中，多种原因会导致螺旋刀片导针发生偏心化，包括骨折端不稳定、软组织嵌入、严重骨质疏松、工具不配套以及透视成像影响等。沿偏心化导针敲入螺旋刀片存在骨折端再移位和螺旋刀片位置不佳的可能，术中应根据偏心角度判断是否需要调整导针方向。.
Keywords: Femoral intertrochanteric fracture; eccentricity; helical blade; intramedullary nail.