Wiggers J K, Snijders R M, Dobbe J G G, Streekstra G J, den Hartog D, Schep N W L
Trauma Unit, Department of Surgery, Academic Medical Center, Meibergdreef 9, 1105 AZ, Amsterdam, The Netherlands.
Department of Biomedical Engineering and Physics, Academic Medical Center, Amsterdam, The Netherlands.
Strategies Trauma Limb Reconstr. 2017 Nov;12(3):133-139. doi: 10.1007/s11751-017-0289-3. Epub 2017 Jun 7.
External fixation of the elbow requires identification of the elbow rotation axis, but the accuracy of traditional landmarks (capitellum and trochlea) on fluoroscopy is limited. The relative distance (RD) of the humerus may be helpful as additional landmark. The first aim of this study was to determine the optimal RD that corresponds to an on-axis lateral image of the elbow. The second aim was to assess whether the use of the optimal RD improves the surgical accuracy to identify the elbow rotation axis on fluoroscopy. CT scans of elbows from five volunteers were used to simulate fluoroscopy; the actual rotation axis was calculated with CT-based flexion-extension analysis. First, three observers measured the optimal RD on simulated fluoroscopy. The RD is defined as the distance between the dorsal part of the humerus and the projection of the posteromedial cortex of the distal humerus, divided by the anteroposterior diameter of the humerus. Second, eight trauma surgeons assessed the elbow rotation axis on simulated fluoroscopy. In a preteaching session, surgeons used traditional landmarks. The surgeons were then instructed how to use the optimal RD as additional landmark in a postteaching session. The deviation from the actual rotation axis was expressed as rotational and translational error (±SD). Measurement of the RD was robust and easily reproducible; the optimal RD was 45%. The surgeons identified the elbow rotation axis with a mean rotational error decreasing from 7.6° ± 3.4° to 6.7° ± 3.3° after teaching how to use the RD. The mean translational error decreased from 4.2 ± 2.0 to 3.7 ± 2.0 mm after teaching. The humeral RD as additional landmark yielded small but relevant improvements. Although fluoroscopy-based external fixator alignment to the elbow remains prone to error, it is recommended to use the RD as additional landmark.
肘部的外固定需要确定肘部的旋转轴，但传统标志点（肱骨小头和滑车）在透视下的准确性有限。肱骨的相对距离（RD）作为额外的标志点可能会有所帮助。本研究的首要目的是确定与肘部轴向侧位影像相对应的最佳RD。第二个目的是评估使用最佳RD是否能提高在透视下确定肘部旋转轴的手术准确性。使用五名志愿者肘部的CT扫描来模拟透视；通过基于CT的屈伸分析计算实际旋转轴。首先，三名观察者在模拟透视下测量最佳RD。RD定义为肱骨背侧与肱骨远端后内侧皮质投影之间的距离除以肱骨的前后径。其次，八名创伤外科医生在模拟透视下评估肘部旋转轴。在预教学环节，外科医生使用传统标志点。然后在教学后环节指导外科医生如何将最佳RD用作额外的标志点。与实际旋转轴的偏差表示为旋转和平移误差（±标准差）。RD的测量稳定且易于重复；最佳RD为45%。在教授如何使用RD后，外科医生确定肘部旋转轴的平均旋转误差从7.6°±3.4°降至6.7°±3.3°。教学后平均平移误差从4.2±2.0降至3.7±2.0毫米。肱骨RD作为额外的标志点产生了虽小但相关的改善。尽管基于透视的肘部外固定器对线仍容易出错，但建议将RD用作额外的标志点。
