Background

Numerous studies have reported an association between rotator cuff injury and two-dimensional measures of scapular morphology. However, the mechanical underpinnings explaining how these shape features affect glenohumeral joint function and lead to injury are poorly understood. We hypothesized that three-dimensional features of scapular morphology differentiate asymptomatic shoulders from those with rotator cuff tears, and that these features would alter the mechanical advantage of the supraspinatus.

Methods

Twenty-four individuals with supraspinatus tears and twenty-seven age-matched controls were recruited. A statistical shape analysis identified scapular features distinguishing symptomatic patients from asymptomatic controls. We examined the effect of injury-associated morphology on mechanics by developing a morphable model driven by six degree-of-freedom biplanar videoradiography data. We used the model to simulate abduction for a range of shapes and computed the supraspinatus moment arm.

Findings

Rotator cuff injury was associated with a cranial orientation of the glenoid and scapular spine (P = .011, d = 0.75) and/or decreased subacromial space (P = .001, d = 0.94). The shape analysis also identified previously undocumented features associated with superior inclination and subacromial narrowing. In our computational model, warping the scapula from a cranial to a lateral orientation increased the supraspinatus moment arm at 20° of abduction and decreased the moment arm at 160° of abduction.

Interpretations

Three-dimensional analysis of scapular morphology indicates a stronger relationship between morphology and cuff tears than two-dimensional measures. Insight into how morphological features affect rotator cuff mechanics may improve patient-specific strategies for prevention and treatment of cuff tears.

中文翻译：

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三维肩cap骨形态与肩袖撕裂有关，并改变了棘上肌的外展力矩臂。

背景

许多研究报告了肩袖损伤与肩cap骨形态的二维测量之间的关联。但是，对于解释这些形状特征如何影响肱肱关节功能并导致受伤的机械基础知之甚少。我们假设，肩cap骨形态的三维特征将无症状的肩部与肩袖撕裂的肩部区别开来，并且这些特征将改变肩pin上的机械优势。

方法

招募了二十四名患有棘上泪的个体和二十七名年龄匹配的对照组。统计形状分析确定了肩cap骨特征，将有症状的患者与无症状的对照区分开。我们通过开发由六自由度双平面视频影像数据驱动的可变形模型，研究了损伤相关形态对力学的影响。我们使用该模型来模拟一系列形状的绑架，并计算了上棘力矩臂。

发现

肩袖损伤与盂盂和肩 cap骨的颅骨方向相关（P = .011，d = 0.75）和/或肩峰下间隙减小（P  = .001，d = 0.94）。形状分析还确定了先前未记录的与上倾和肩峰下狭窄相关的特征。在我们的计算模型中，使肩cap骨从颅骨向侧向弯曲，在外展20°时增加了棘上肌力矩臂，在外展160°时降低了力矩臂。

释义

肩cap骨形态的三维分析表明，与二维测量相比，形态学与袖口撕裂之间的关系更强。对形态特征如何影响肩袖力学的见解可以改善针对患者的预防和治疗袖带撕裂的策略。