Berhouet Julien, Kontaxis Andreas, Gulotta Lawrence V, Craig Edward, Warren Russel, Dines Joshua, Dines David
Department of Sports Medicine and Shoulder, Hospital For Special Surgery, New York, NY, USA; The Leon Root, M.D. Motion Analysis Laboratory, Hospital For Special Surgery, New York, NY, USA.
The Leon Root, M.D. Motion Analysis Laboratory, Hospital For Special Surgery, New York, NY, USA.
J Shoulder Elbow Surg. 2015 Apr;24(4):569-77. doi: 10.1016/j.jse.2014.09.022. Epub 2014 Nov 6.
Recent shoulder prostheses have introduced a concept of a universal humeral stem component platform that has an onlay humeral tray for the reverse total shoulder arthroplasty (RTSA). No studies have reported how humeral tray positioning can affect the biomechanics of RTSA.
The Newcastle Shoulder Model was used to investigate the biomechanical effect of humeral tray positioning in the Biomet Comprehensive Total Shoulder System (Biomet, Warsaw, IN, USA) RTSA. Five humeral tray configuration positions were tested: no offset, and 5 mm offset in the anterior, posterior, medial, and lateral positions. Superior and inferior impingement were evaluated for abduction, scapular plane elevation, forward flexion, and external/internal rotation with the elbow at the side (adduction) and at 90° of shoulder abduction. Muscle lengths and moment arms (elevating and rotational) were calculated for the deltoid, the infraspinatus, the teres minor, and the subscapularis.
Inferior impingement was not affected by the humeral tray position. There was less superior impingement during abduction, scapular plane elevation, and rotation with the shoulder when the tray was placed laterally or posteriorly. The subscapularis rotational moment arm was increased with a posterior offset, whereas infraspinatus and teres minor rotational moment arms were increased with an anterior offset. Very little change was observed for the deltoid elevating moment arm or for its muscle length.
Positioning the humeral tray with posterior offset offers a biomechanical advantage for patients needing RTSA by decreasing superior impingement and increasing the internal rotational moment arm of the subscapularis, without creating inferior impingement.
近期的肩部假体引入了一种通用肱骨干组件平台的概念，该平台具有用于反向全肩关节置换术（RTSA）的覆盖式肱骨托盘。尚无研究报道肱骨托盘的定位如何影响RTSA的生物力学。
使用纽卡斯尔肩部模型研究在Biomet全肩关节系统（Biomet，美国印第安纳州华沙）RTSA中肱骨托盘定位的生物力学效应。测试了五种肱骨托盘配置位置：无偏移，以及在前、后、内侧和外侧位置有5毫米偏移。在肘部位于身体一侧（内收）和肩部外展90°时，评估外展、肩胛平面抬高、前屈以及外旋/内旋时的上、下撞击情况。计算三角肌、冈下肌、小圆肌和肩胛下肌的肌肉长度和力臂（抬高和旋转）。
下撞击不受肱骨托盘位置的影响。当托盘置于外侧或后侧时，在肩部外展、肩胛平面抬高和旋转过程中，上撞击较少。肩胛下肌的旋转力臂在有后偏移时增加，而冈下肌和小圆肌的旋转力臂在有前偏移时增加。三角肌的抬高力臂及其肌肉长度变化很小。
对于需要RTSA的患者，将肱骨托盘置于后偏移位置可提供生物力学优势，即减少上撞击并增加肩胛下肌的内旋力臂，而不会产生下撞击。
