Fleet Cole T, Carroll Patrick, Johnson James A, Athwal George S
Roth | McFarlane Hand and Upper Limb Centre, St Joseph's Health Care, London, Ontario, Canada; Department of Mechanical and Materials Engineering, Western University, London, Ontario, Canada.
Department of Surgery, University of Toronto, Toronto, Ontario, Canada; St. Joseph's Health Center | Unity Health Toronto, Toronto, Ontario, Canada.
J Shoulder Elbow Surg. 2025 Feb 13. doi: 10.1016/j.jse.2024.12.049.
The constraint of the polyethylene liner in reverse total shoulder arthroplasty (rTSA) can affect glenohumeral joint stability. However, its influence on glenohumeral range of motion (ROM) remains unclear. Therefore, it was the objective of this study to determine the effect of sequentially increasing polyethylene liner constraint on impingement-free ROM following rTSA. Additionally, these sequentially increasing constraint designs were evaluated with various humeral neck-shaft angles (NSAs), glenosphere diameters, and a new variable termed the polyethylene rim width.
Twenty upper extremity cadavers were computed tomography scanned and manually segmented to developed 3-dimensional models of the scapula and humerus. Each model was then virtually implanted with a generic rTSA implant. Nine different polyethylene constraint ratios (defined as the ratio between the polyethylene depth and polyethylene radius; with values ranging from 0.35-0.75 in 0.05 increments) were assessed, along with 3 NSAs (135°, 145°, and 155°), 3 glenosphere diameters (36, 39, and 42 mm), and 4 polyethylene rim widths (1, 2, 3, and 4 mm). This resulted in 108 different polyethylene designs and 324 different rTSA designs. All virtually implanted bone models were imported as rigid bodies into a custom motion software, in which 6 standard motions (abduction, adduction, forward elevation, extension, internal rotation, and external rotation) were conducted, followed by the assessment of global circumduction ROM. Impingement during each motion was automatically detected. The maximum impingement-free ROM for each implant configuration and motion pathway were then quantified and statistically assessed.
Polyethylene constraint, polyethylene rim width, NSA, and glenosphere diameter were all found to significantly affect impingement-free ROM for all motions simulated (P < .001). Increases in polyethylene constraint and rim width were found to significantly reduce impingement-free ROM (P < .001). A 135° NSA with a 42mm glenosphere combination were found to maximize ROM during extension, adduction, internal rotation, external rotation, and global circumduction motion, while a 155° NSA with a 36-mm glenosphere combination resulted in optimized abduction and forward elevation ROM.
Increases in polyethylene constraint were found to significantly reduce impingement-free ROM for all motions evaluated. However, polyethylene constraint had the greatest impact on glenohumeral extension, adduction, internal rotation, external rotation, and global circumduction. Polyethylene rim width was also found to significantly affect impingement-free ROM for all motions. Further study is needed to determine the optimal value of polyethylene liner constraint in rTSA because of its impact on rTSA biomechanics, joint stability, and ROM.
在反式全肩关节置换术（rTSA）中，聚乙烯衬垫的约束作用会影响盂肱关节的稳定性。然而，其对盂肱关节活动范围（ROM）的影响尚不清楚。因此，本研究的目的是确定在rTSA后，依次增加聚乙烯衬垫约束对无撞击ROM的影响。此外，还对这些依次增加的约束设计在不同肱骨干颈干角（NSA）、球盂假体直径以及一个新变量——聚乙烯边缘宽度下进行了评估。
对20具上肢尸体进行计算机断层扫描，并手动分割以建立肩胛骨和肱骨的三维模型。然后将每个模型虚拟植入一个通用的rTSA假体。评估了9种不同的聚乙烯约束比（定义为聚乙烯深度与聚乙烯半径之比；值范围为0.35 - 0.75，增量为0.05），以及3种NSA（135°、145°和155°）、3种球盂假体直径（36、39和42mm）和4种聚乙烯边缘宽度（1、2、3和4mm）。这产生了108种不同的聚乙烯设计和324种不同的rTSA设计。所有虚拟植入的骨骼模型作为刚体导入到定制的运动软件中，在该软件中进行6种标准运动（外展、内收、前屈、伸展、内旋和外旋），随后评估整体环转ROM。自动检测每个运动过程中的撞击情况。然后对每种植入物配置和运动路径的最大无撞击ROM进行量化并进行统计学评估。
发现聚乙烯约束、聚乙烯边缘宽度、NSA和球盂假体直径均对模拟的所有运动的无撞击ROM有显著影响（P <.001）。发现聚乙烯约束和边缘宽度的增加会显著降低无撞击ROM（P <.001）。发现在伸展、内收、内旋、外旋和整体环转运动中，135°NSA与42mm球盂假体的组合可使ROM最大化，而在155°NSA与36mm球盂假体的组合下，外展和前屈ROM得到优化。
发现聚乙烯约束的增加会显著降低评估的所有运动的无撞击ROM。然而，聚乙烯约束对盂肱关节伸展、内收、内旋、外旋和整体环转的影响最大。还发现聚乙烯边缘宽度对所有运动的无撞击ROM也有显著影响。由于聚乙烯衬垫约束对rTSA生物力学、关节稳定性和ROM有影响，因此需要进一步研究以确定rTSA中聚乙烯衬垫约束的值。
