Background:The critical shoulder angle (CSA) has become an important topic of study in patients with rotator cuff tears (RCTs). However, there are conflicting data on whether the CSA can differentiate between patients with normal shoulder pathology and full-thickness RCTs on shoulder radiographs.Purpose/Hypothesis:The purpose of this study was to define the relationship between full-thickness RCTs and the CSA. It was hypothesized that patients with full-thickness RCTs would have an increased CSA compared with matched controls.Study Design:Cross-sectional study; Level of evidence, 3.Methods:This retrospective case-control study identified patients with magnetic resonance imaging scans showing full-thickness RCTs between 2009 and 2019. A 1 to 1 propensity score match was performed to identify a control group with normal rotator cuffs while controlling for baseline participant characteristics—including age, sex, body mass index, and tobacco use. A total cohort of 532 was identified, with 266 cases and 266 controls. Two independent observers measured CSAs on true anteroposterior shoulder radiographs.Results:There was no difference in baseline participant characteristics between the RCT and the non-RCT groups ( P > .05). The mean CSA for the entire cohort was 33.6°± 4.2°. The CSA did not significantly vary by sex ( P = .088) or tobacco usage ( P = .16). The mean CSA for the RCT case group, 36.2°± 3.3°, was significantly different from the mean CSA for the control group, 30.9°± 3.3° ( P < .0001). The receiver operating characteristic curve analysis produced an area under the curve of 0.88 ( P < .0001). At CSAs ≥35°, there was a 67.7% sensitivity and 89.4% specificity for having a full-thickness RCT. Last, each degree of increase in the CSA increased the risk of having an associated RCT by 1.7 times (OR, 1.7 [95% CI, 1.551-1.852]; P < .0001).Conclusion:Patients with RCTs had significantly higher CSAs compared with matched controls. Increased CSA was an independent risk factor for RCTs, with an odds ratio of 1.7 per degree. The CSA is an accurate test (area under the curve, 0.88) with good sensitivity (67.7%) and specificity (89.4%) at values ≥35°. The CSA is a simple, reproducible measurement that can assist in clinical decision-making regarding full-thickness RCTs.

中文翻译：

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临界肩角作为全层肩袖撕裂的高度特异性预测因子：病例对照研究


背景： 临界肩角 （CSA） 已成为肩袖撕裂 （RCTs） 患者的重要研究课题。然而，关于 CSA 是否可以区分肩部病变正常的患者和肩部 X 线片上的全层 RCT 患者，存在相互矛盾的数据。目的/假设： 本研究的目的是确定全层 RCT 与 CSA 之间的关系。据推测，与匹配的对照组相比，全层 RCT 患者的 CSA 会增加。研究设计： 横断面研究;证据水平， 3.方法： 这项回顾性病例对照研究确定了 2009 和 2019年磁共振成像扫描显示全层 RCT 的患者。进行 1 比 1 倾向评分匹配，以确定肩袖正常的对照组，同时控制基线参与者特征——包括年龄、性别、体重指数和烟草使用。共确定了 532 个队列，其中 266 例和 266 例对照。两名独立观察者在真正的肩部前后位 X 光片上测量 CSA。结果： RCT 组和非 RCT 组基线参与者特征无差异 （ P > .05）。整个队列的平均 CSA 为 33.6°± 4.2°。CSA 因性别 （P = .088） 或烟草使用 （P = .16） 没有显著差异。RCT 病例组的平均 CSA 为 36.2°± 3.3°，与对照组的平均 CSA 为 30.9°± 3.3° 差异显著 （P < .0001）。受试者工作特征曲线分析得出曲线下面积为 0.88 （P < .0001）。在 CSAs ≥35° 时，进行全层 RCT 的敏感性为 67.7%，特异性为 89.4%。 最后，CSA 每增加一个程度，发生相关 RCT 的风险就会增加 1.7 倍 （OR，1.7 [95% CI，1.551-1.852];P < .0001）.结论： 与匹配的对照组相比，RCTs 患者的 CSAs 显著升高。CSA 升高是 RCT 的独立危险因素，比值比为每度 1.7。CSA 是一种准确的测试 （曲线下面积，0.88），在 ≥35° 的值下具有良好的敏感性 （67.7%） 和特异性 （89.4%）。CSA 是一种简单、可重复的测量方法，可协助临床做出有关全层 RCT 的决策。