背景:反向全肩关节成形术(RTSA)改变了盂肱关节周围肌肉的作用线。这些变化的影响已经很好地表征了三角肌,但是关于腕臂(CBR)和肱二头肌短头(SHB)的生物力学变化的信息有限。在这项生物力学研究中,我们使用肩部的计算模型调查了由于RTSA引起的CBR和SHB的力矩臂的变化。
方法:纽卡斯尔肩膀模型,预先验证的上肢肌肉骨骼模型,用于这项研究。纽卡斯尔肩模型通过从15个未患病肩的三维重建中获得的骨骼几何形状进行了修改,构成本地肩群。DeltaXTEND假体,卵球直径为38毫米,聚乙烯厚度为6毫米,几乎植入了所有的模型,创建RTSA组。使用肌腱偏移法测量力矩臂,肌肉长度计算为肌肉起点和插入点之间的距离。这些值是在0°-150°外展期间测量的,前屈,肩胛骨平面高程,和-90°至60°的外部旋转-在外展20°和90°时手臂的内部旋转。使用一维统计参数作图(spm1D)分析天然组和RTSA组之间的统计比较。
结果:前屈力矩臂在RTSA组之间显示出最大的增加(CBR,25.3±4.7mm;SHB,24.7±4.5mm)和天然组(CBR,9.6±5.2mm;SHB,10.2±5.2mm)。RTSA组中CBR和SHB的最大值分别为15%和7%,分别。RTSA组的两条肌肉都有较大的外展力矩臂(CBR,20.9±4.3mm;SHB,21.9±4.3mm)与天然组(CBR,19.6±6.6mm;SHB,20.0±5.7mm)。在RTSA组中,绑架力矩臂发生在较低的外展角度(CBR,50°;SHB,45°)比天然组(CBR,90°;SHB,85°)。在RTSA组中,两个肌肉都有抬高力矩臂,直到肩胛骨平面抬高运动25°,而在本地组中,肌肉只有沮丧的时刻的手臂。两种肌肉都具有较小的旋转力矩臂,在不同的运动范围内,RTSA和天然肩部之间存在显着差异。
结论:在RTSA肩部观察到CBR和SHB的抬高力矩臂显著增加;这些增加在外展和向前抬高运动期间最为明显。RTSA还增加了这些肌肉的长度。
BACKGROUND: Reverse total shoulder arthroplasty (RTSA) alters the line of action of muscles around the glenohumeral joint. The effects of these changes have been well characterized for the deltoid, but there is limited information regarding the biomechanical changes to the
coracobrachialis (CBR) and short head of biceps (SHB). In this biomechanical study, we investigated the changes to the moment arms of the CBR and SHB due to RTSA using a computational model of the shoulder.
METHODS: The Newcastle Shoulder Model, a pre-validated upper-extremity musculoskeletal model, was used for this study. The Newcastle Shoulder Model was modified with bone geometries obtained from 3-dimensional reconstructions of 15 nondiseased shoulders, constituting the native shoulder group. The Delta XTEND prosthesis, with a glenosphere diameter of 38 mm and polyethylene thickness of 6 mm, was virtually implanted in all the models, creating the RTSA group. Moment arms were measured using the tendon excursion method, and muscle length was calculated as the distance between the muscle\'s origin and insertion points. These values were measured during 0°-150° of abduction, forward flexion, scapular-plane elevation, and -90° to 60° of external rotation-internal rotation with the arm at 20° and 90° of abduction. Statistical comparisons between the native and RTSA groups were analyzed using 1-dimensional statistical parametric mapping (spm1D).
RESULTS: Forward flexion moment arms showed the greatest increase between the RTSA group (CBR, 25.3 ± 4.7 mm; SHB, 24.7 ± 4.5 mm) and native group (CBR, 9.6 ± 5.2 mm; SHB, 10.2 ± 5.2 mm). The CBR and SHB were longer in the RTSA group by maximum values of 15% and 7%, respectively. Both muscles had larger abduction moment arms in the RTSA group (CBR, 20.9 ± 4.3 mm; SHB, 21.9 ± 4.3 mm) compared with the native group (CBR, 19.6 ± 6.6 mm; SHB, 20.0 ± 5.7 mm). Abduction moment arms occurred at lower abduction angles in the RTSA group (CBR, 50°; SHB, 45°) than in the native group (CBR, 90°; SHB, 85°). In the RTSA group, both muscles had elevation moment arms until 25° of scapular-plane elevation motion, whereas in the native group, the muscles only had depression moment arms. Both muscles had small rotational moment arms that were significantly different between RTSA and native shoulders during different ranges of motion.
CONCLUSIONS: Significant increases in elevation moment arms for the CBR and SHB were observed in RTSA shoulders; these increases were most pronounced during abduction and forward elevation motions. RTSA also increased the lengths of these muscles.