Yam Michael, Chawla Anuj, Kwek Ernest
Tan Tock Seng Hospital, Singapore.
Injury. 2017 Aug;48(8):1843-1847. doi: 10.1016/j.injury.2017.06.020. Epub 2017 Jul 1.
The proximal femur nail anti-rotation (PFNA-II) (Synthes GmbH, Oberdorf, Switzerland) is the most commonly used implant for intramedullary nailing of unstable intertrochanteric fractures in our centre. However, mechanical failure of the bone with respect to the implant is a cause of concern due to its significant morbidity especially in the elderly. To date, factors for fixation failures are not well defined in the literature. This study aims to evaluate the factors that predispose to cut out of the PFNA implant and to provide a guide for surgical fixation.
This study was a retrospective analysis of 340 patients who underwent PFNA-II insertion from 2011 to 2013 in our centre. Intraoperative image intensifier images were used for calculation of tip apex distance, neck shaft angles, determination of Cleveland zones. Demographic data was collected on patients age and gender. The fractures were classified based on AO-OTA classification (Marsh et al., 2007) [1]. Patients were followed up for a minimum of 4 months and union of the fracture or until a complication occurred. Risk ratio for cut out was also compared with each statistically significant variable to determine the cut-off point.
The incidence of cut out was 6.7% Tip apex distance, neck shaft angles and female gender were statistically significant for cut out. The study found that tip apex distance beyond 27mm increased the risk of cut out. Neck shaft angles less than 128° also increased the risk of cut out. Posterior and superior blade position in the femoral head and AO 31A3 fractures trended towards significance for cut out but were not statistically significant.
To avoid cut out, one should aim for a tip apex distance of not more than 27mm and preserve a neck shaft angle of more than 128°. Risk stratification of the patient allows the surgeon to take greater caution in the post-operative period to detect early cut out.
股骨近端抗旋髓内钉（PFNA-II）（瑞士奥伯多夫的 Synthes 公司）是我们中心治疗不稳定型股骨转子间骨折髓内固定最常用的植入物。然而，由于其显著的发病率，尤其是在老年人中，骨骼相对于植入物的机械性失效令人担忧。迄今为止，文献中对固定失败的因素尚未明确界定。本研究旨在评估导致 PFNA 植入物穿出的因素，并为手术固定提供指导。
本研究是对 2011 年至 2013 年在我们中心接受 PFNA-II 植入的 340 例患者进行的回顾性分析。术中使用影像增强器图像计算尖顶距、颈干角，确定克利夫兰分区。收集患者年龄和性别的人口统计学数据。骨折根据 AO-OTA 分类（Marsh 等人，2007 年）[1]进行分类。对患者进行至少 4 个月的随访，直至骨折愈合或出现并发症。还将穿出的风险比与每个具有统计学意义的变量进行比较，以确定临界点。
穿出的发生率为 6.7%。尖顶距、颈干角和女性性别对穿出具有统计学意义。研究发现，尖顶距超过 27mm 会增加穿出风险。颈干角小于 128°也会增加穿出风险。股骨头中后刀片和上刀片位置以及 AO 31A3 骨折在穿出方面有显著趋势，但无统计学意义。
为避免穿出，应使尖顶距不超过 27mm，并保持颈干角大于 128°。对患者进行风险分层可使外科医生在术后更加谨慎，以便早期发现穿出情况。
