Background:Nonoperative management of posterior shoulder instability is common. However, limited data are available to assess the pathomorphologic factors associated with its failure.Purpose/Hypothesis:The purpose of this study was 2-fold: (1) to determine glenohumeral pathomorphologic features predictive of nonoperative management failure of posterior instability; and (2) to determine the relationship between nonoperative management failure and posterior glenoid bone loss (pGBL) progression. It was hypothesized that greater posterior acromial height (PAH) would adversely affect nonoperative survivorship and that shoulders treated nonoperatively would have pGBL progression compared with those undergoing surgical stabilization.Study Design:Case-control study; Level of evidence, 3.Methods:This was a retrospective review of a consecutive series of patients with isolated posterior shoulder instability, defined as isolated posterior labral tear on magnetic resonance imaging (MRI) with corresponding physical examination findings, who underwent nonoperative management for 6 months and had no previous related surgical history. The primary outcome of interest was the failure of nonoperative management, defined as the inability to return to full military duty or requiring surgical intervention. The morphologic features assessed for association with nonoperative management failure included pGBL, glenoid version, acromial morphology, and posterior humeral head subluxation. We secondarily sought to determine the progression of pGBL on serial MRI scans. Cox proportional hazard analysis was used to evaluate risk factors for failure.Results:In this study, 42 of 90 (46.7%) patients had failed nonoperative management and went on to receive an arthroscopic stabilization procedure. The group with failed treatment demonstrated a greater humeral head subluxation ratio than those with successful nonoperative management (0.65 ± 0.2 vs 0.62 ± 0.2; P = .038). Cox proportional hazard analysis identified pGBL, greater PAH, less posterior acromial coverage, and posterior humeral subluxation as significant risk factors for failure. Of those with failed nonoperative management, 17 had repeat MRI scans at a mean of 488.2 ± 87 days after index MRI for comparison, demonstrating a statistically significant progression of pGBL (index MRI, 2.68% ± 1.71%) versus after nonoperative treatment failure (6.54% ± 1.59%; P = .003).Conclusion:Failure occurred 47% of the time in patients who underwent nonoperative management for isolated posterior glenohumeral instability for a minimum of 6 months, and it was associated with a greater posterior humeral head subluxation, less posterior acromial coverage, greater PAH, and greater amounts of glenoid retroversion on index MRI. Additionally, those who had repeat MRI approximately 1 year after the index MRI demonstrated greater pGBL compared with the index MRI.

中文翻译：

---

现役军人孤立性后盂肱关节不稳定的非手术治疗：盂状骨和肩峰形态的影响


背景： 肩后部不稳定的非手术治疗很常见。然而，可用于评估与其失败相关的病理形态学因素的数据有限。目的/假设： 本研究的目的有两个： （1） 确定预测后部不稳定非手术管理失败的盂肱关节病理形态学特征;（2） 确定非手术管理失败与后关节盂骨丢失 （pGBL） 进展之间的关系。据推测，较大的肩峰后高 （PAH） 会对非手术生存率产生不利影响，并且与接受手术稳定的肩部相比，非手术治疗的肩部会出现 pGBL 进展。研究设计： 病例对照研究;证据水平， 3.方法： 这是对连续系列孤立性后肩关节不稳定患者的回顾性评价，定义为磁共振成像 （MRI） 上孤立性后盂唇撕裂，有相应的体格检查结果，这些患者接受了 6 个月的非手术治疗，既往无相关手术史。感兴趣的主要结局是非手术治疗失败，定义为无法完全恢复军事职责或需要手术干预。评估与非手术治疗失败相关的形态学特征包括 pGBL 、 关节盂倒转、肩峰形态和肱骨后头半脱位。我们次要试图确定连续 MRI 扫描中 pGBL 的进展。采用 Cox 比例风险分析评估失败的危险因素。结果： 在本研究中，90 例患者中有 42 例 （46.7%） 非手术管理失败，并继续接受关节镜稳定手术。 治疗失败的组表现出比非手术治疗成功的组更大的肱骨头半脱位比 （0.65 ± 0.2 vs 0.62 ± 0.2;P = .038）。Cox 比例风险分析确定 pGBL 、 PAH 较大、肩峰后部覆盖较少和肱骨后部半脱位是失败的重要危险因素。在非手术治疗失败的患者中，17 例在指数 MRI 后平均 488.2 ± 87 天重复 MRI 扫描以进行比较，显示 pGBL 进展（指数 MRI，2.68% ± 1.71%）与非手术治疗失败后 （6.54% ± 1.59%） 相比具有统计学意义的进展;P = .003）。结论： 在接受孤立性后盂肱关节不稳定非手术治疗至少 6 个月的患者中，失败率为 47%，并且与肱骨后头半脱位较大、肩峰后部覆盖较少、PAH 较大和指数 MRI 上关节盂逆移量较大相关。此外，与指数 MRI 相比，在指数 MRI 后约 1 年重复 MRI 的患者表现出更高的 pGBL。