Trauma Department, Hannover Medical School, Carl-Neuberg-Str. 1, 30625, Hannover, Germany,
Arch Orthop Trauma Surg. 2014 May;134(5):645-50. doi: 10.1007/s00402-014-1964-1. Epub 2014 Mar 4.
Accurate restoration of mechanical alignment is an important factor in reconstructive surgery of the lower extremity. Conventional intraoperative methods, such as using an electrocautery cable, provide only a momentary evaluation of alignment. In this study, we evaluated a novel technique using a laser emitter, which projected the mechanical axis of the lower extremity, providing continuous intraoperative information on alignment.
Alignment of 16 cadaver lower extremities was measured using the electrocautery cable method, the laser method, and CT scan as the standard measurement. The mechanical axis was defined by a line from the center of the femoral head to the center of the ankle. For simplifying measurements the intersection with the tibial plateau was divided into percentages from the medial border (0 %) to the lateral border (100 %). For using the laser method a laser emitting and laser catching device was developed, which is positioned and centered on the femoral head and the ankle using an image intensifier. By catching the laser on the knee region the actual mechanical axis is marked.
The data demonstrated good correlation of the laser method when compared to the cable method (P = 0.44). Comparison of the average mechanical axis between cable method and CT (P = 0.819) and laser method and CT (P = 0.647) did not show a statistically significant difference. Average radiation time in comparison between cable method and laser method showed a statistically significant difference (P = 0.013), with the laser method requiring more radiation time.
Determination of the mechanical axis during surgery remains a difficult clinical problem. Restoration of alignment is an important prognostic factor for surgical outcome. Based on these data, the laser method represents a simple, yet effective tool for continuous intraoperative evaluation of lower extremity alignment.
准确恢复下肢的机械对线是重建手术的一个重要因素。传统的术中方法，如使用电烙术电缆，只能提供对线的瞬间评估。在这项研究中，我们评估了一种使用激光发射器的新方法，该方法投射下肢的机械轴，提供对线的连续术中信息。
使用电烙术电缆法、激光法和 CT 扫描作为标准测量方法测量 16 具尸体下肢的对线。机械轴由从股骨头中心到踝关节中心的线定义。为了简化测量，将胫骨平台的交点从内侧边界（0%）到外侧边界（100%）分为百分比。为了使用激光方法，开发了一种激光发射和激光接收装置，该装置使用影像增强器定位和集中在股骨头和踝关节上。通过在膝关节区域捕捉激光，可以标记实际的机械轴。
数据表明，与电缆法相比，激光法具有良好的相关性（P=0.44）。电缆法与 CT （P=0.819）和激光法与 CT （P=0.647）之间的平均机械轴比较没有显示出统计学上的显著差异。电缆法和激光法之间的平均辐射时间比较显示出统计学上的显著差异（P=0.013），激光法需要更多的辐射时间。
在手术中确定机械轴仍然是一个困难的临床问题。对线的恢复是手术结果的一个重要预后因素。基于这些数据，激光法代表了一种简单而有效的连续术中评估下肢对线的工具。
