Department of Biomedical Engineering, University of Melbourne, Parkville, Victoria, Australia.
Department of Orthopaedic Surgery, Epworth Healthcare, Richmond, Victoria, Australia.
J Orthop Res. 2019 Sep;37(9):1988-2003. doi: 10.1002/jor.24335. Epub 2019 Jun 18.
Changes in joint architecture and muscle loading resulting from total shoulder arthroplasty (TSA) and reverse total shoulder arthroplasty (RSA) are known to influence joint stability and prosthesis survivorship. This study aimed to measure changes in muscle moment arms, muscle lines of action, as well as muscle and joint loading following TSA and RSA using a metal-backed uncemented modular shoulder prosthesis. Eight cadaveric upper extremities were assessed using a customized testing rig. Abduction, flexion, and axial rotation muscle moment arms were quantified using the tendon-excursion method, and muscle line-of-force directions evaluated radiographically pre-operatively, and after TSA and revision RSA. Specimen-specific musculoskeletal models were used to estimate muscle and joint loading pre- and post-operatively. TSA lateralized the glenohumeral joint center by 4.3 ± 3.2 mm, resulting in small but significant increases in middle deltoid force (2.0%BW) and joint compression during flexion (2.1%BW) (p < 0.05). Revision RSA significantly increased the moment arms of the major abductors, flexors, adductors, and extensors, and reduced their peak forces (p < 0.05). The superior inclination of the deltoid significantly increased while the inferior inclination of the rotator cuff muscles decreased (p < 0.05). TSA using an uncemented metal-backed modular shoulder prosthesis effectively restores native joint function; however, lateralization of the glenoid component should be minimized intra-operatively to mitigate increased glenohumeral joint loading and polyethylene liner contact stresses. Revision RSA reduces muscle forces required during shoulder function but produces greater superior joint shear force and less joint compression. The findings may help to guide component selection and placement to mitigate joint instability after arthroplasty. © 2019 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 37:1988-2003, 2019.
全肩关节置换术（TSA）和反式全肩关节置换术（RSA）引起的关节结构和肌肉负荷的变化已知会影响关节稳定性和假体存活率。本研究旨在使用金属背衬非骨水泥模块化肩关节假体测量 TSA 和 RSA 后肌肉力臂、肌肉作用线以及肌肉和关节负荷的变化。使用定制的测试装置评估了 8 个尸体上肢。使用肌腱伸长度法定量测量外展、屈曲和轴向旋转肌肉力臂，并在术前、TSA 后和 RSA 后进行 X 线评估肌肉力线方向。使用特定于标本的肌肉骨骼模型估计术前和术后的肌肉和关节负荷。TSA 使盂肱关节中心向外侧移位 4.3±3.2mm，导致三角肌中部力（2.0%BW）和屈曲时关节压缩力（2.1%BW）有小但显著的增加（p<0.05）。RSA 显著增加了主要外展肌、屈肌、内收肌和伸肌的力臂，并降低了它们的峰值力（p<0.05）。三角肌的优势倾斜明显增加，而肩袖肌肉的劣势倾斜减小（p<0.05）。使用非骨水泥金属背衬模块化肩关节假体的 TSA 有效地恢复了关节的正常功能；然而，术中应尽量减少肩胛盂组件的侧方移位，以减轻盂肱关节的负荷增加和聚乙烯衬垫接触应力。RSA 降低了肩部功能所需的肌肉力，但产生了更大的关节上剪切力和更小的关节压缩力。这些发现可能有助于指导假体置换后关节稳定性的组件选择和放置。© 2019 骨科研究协会。由 Wiley Periodicals, Inc. 出版。J Orthop Res 37:1988-2003, 2019.
