Cunningham Gregory, Bernardo Lauryne, Brandariz Rodrigo, Holzer Nicolas, Da Rocha Daniel, Beaulieu Jean-Yves
Shoulder and Elbow Center La Colline, Geneva, Switzerland.
Division of Orthopaedics and Trauma Surgery, Department of Surgery, Geneva University Hospitals, Geneva, Switzerland.
JSES Int. 2024 Apr 16;8(4):873-879. doi: 10.1016/j.jseint.2024.03.013. eCollection 2024 Jul.
Peripheral nerve injury is a recognized complication after reverse shoulder arthroplasty (RSA) that has mainly been studied at the level of the brachial plexus and its proximal branches. However, the impact of RSA on distal peripheral nerves and the influence of elbow and wrist position is not known. This cadaveric study aimed to analyze the effect of RSA implantation and upper limb position on tension in the distal median and radial nerves. The hypothesis was that RSA increased distal nerve tension, which could be further affected by elbow and wrist position.
12 upper limbs in 9 full fresh-frozen cadavers were dissected. Nerve tension was measured in the median nerve at the level of the proximal arm, elbow, and distal forearm, and in the radial nerve at the level of the elbow, using a customized three-point tensiometer. Measurements were carried out before and after RSA implantation, using a semi-inlay implant (Medacta, Castel San Pietro, Switzerland). Two different configurations were tested, using the smallest and largest available implant sizes. Three upper-limb key positions were considered (plexus at risk, plexus relief, and neutral), from which the effect of elbow and wrist position was further tested.
RSA implantation significantly increased median and radial nerve tension throughout the upper limb. The distal nerve segments were particularly dependent on elbow and wrist position. The plexus at risk position induced the most tension in all nerve segments, especially with the large implant configuration. On the other hand, the plexus relief position induced the least amount of tension. Flexing the elbow was the most efficient way to decrease nerve tension in all tested nerve segments and key positions. Wrist flexion significantly decreased nerve tension in the median nerve, whereas wrist extension decreased tension in the radial nerve.
RSA significantly increases tension in the median and radial nerves and makes them more susceptible to wrist and elbow positioning. The mechanism behind distal peripheral neuropathy after RSA may thus result from increased compression of tensioned nerves against anatomical fulcrums rather than nerve elongation alone. Elbow flexion was the most effective way to decrease nerve tension, while elbow extension should be avoided when implanting the humeral component. Further studies are needed to assess the ulnar nerve.
周围神经损伤是反式肩关节置换术（RSA）后一种公认的并发症，此前主要是在臂丛及其近端分支层面进行研究。然而，RSA对远端周围神经的影响以及肘部和腕部位置的影响尚不清楚。这项尸体研究旨在分析RSA植入和上肢位置对远端正中神经和桡神经张力的影响。假设是RSA会增加远端神经张力，而这可能会受到肘部和腕部位置的进一步影响。
对9具完整新鲜冷冻尸体的12条上肢进行解剖。使用定制的三点张力计，在近端手臂、肘部和远端前臂水平测量正中神经的张力，并在肘部水平测量桡神经的张力。在植入RSA之前和之后进行测量，使用半镶嵌植入物（Medacta，瑞士圣彼得罗城堡）。使用最小和最大可用植入物尺寸测试两种不同配置。考虑了三个上肢关键位置（有风险的神经丛、缓解神经丛的位置和中立位置），并在此基础上进一步测试肘部和腕部位置的影响。
RSA植入显著增加了整个上肢的正中神经和桡神经张力。远端神经节段尤其依赖于肘部和腕部位置。有风险的神经丛位置在所有神经节段中引起的张力最大，尤其是在大尺寸植入物配置下。另一方面，缓解神经丛的位置引起的张力最小。屈曲肘部是在所有测试的神经节段和关键位置降低神经张力的最有效方法。腕部屈曲显著降低正中神经的张力，而腕部伸展则降低桡神经的张力。
RSA显著增加正中神经和桡神经的张力，并使它们更容易受到腕部和肘部位置的影响。因此，RSA后远端周围神经病变背后的机制可能是由于紧张的神经与解剖支点之间的压迫增加，而不仅仅是神经伸长。屈曲肘部是降低神经张力的最有效方法，在植入肱骨组件时应避免伸直肘部。需要进一步研究来评估尺神经。
