Abstract：
BACKGROUND: The ABC classification has recently been proposed as a comprehensive classification system for posterior shoulder instability (PSI). The purpose of this study was to analyze the comprehensiveness as well as inter-rater and intrarater reliability of the ABC classification.
METHODS: All consecutive patients presenting with unidirectional PSI from June 2019 to June 2021 were included in a prospective study. No patients were excluded, leaving a consecutive series of 100 cases of PSI in 91 patients. All recorded clinical and imaging data were used to create anonymized clinical case vignettes, which were evaluated twice according to the ABC classification at the end of the recruitment period in random sequential order by 4 independent raters (2 experienced shoulder surgeons and 2 orthopedic residents) to analyze the comprehensiveness as well as inter-rater and intrarater reliability of the ABC classification for PSI and to describe differences in characteristics among subtypes. Group A was defined as a first-time singular PSI event <3 months in the past regardless of etiology and is further subdivided into type 1 and type 2 depending on the occurrence of a subluxation (A1) or dislocation (A2). Group B comprises recurrent dynamic PSI regardless of time since onset and is further subdivided by the cause of instability into functional (B1) and structural (B2) dynamic PSI. Group C includes chronic static PSI with posterior humeral decentering that can be either constitutional (C1) or acquired (C2).
RESULTS: None of the cases was deemed unsuitable to be classified based on the proposed system by the observers. After consensus agreement between the 2 expert raters, 16 cases were attributed to group A (8 type A1 and 8 type A2); 64, to group B (33 type B1 and 31 type B2); and 20, to group C (11 type C1 and 9 type C2). The expert raters agreed on the classification subtypes in 99% and 96% of the cases during the first rating and second rating, respectively (intraclass correlation coefficients [ICCs], 0.998 and 0.99, respectively). The intraobserver reliability was excellent for both raters. The beginners reached the same conclusion as the consensus agreement in 94% of the cases (ICC, 0.99) and 89% of the cases (ICC, 0.97) during the first round and 94% each (ICC, 0.97) during the second round. The intraobserver reliability was excellent for both beginners. Overall, discrepancies between raters were found between groups B1 and B2 (n = 14), groups B2 and C2 (n = 4), groups B1 and C1 (n = 1), and groups A1 and B2 (n = 1). In general, each subtype showed distinctive clinical and imaging characteristics that facilitated the diagnosis.
CONCLUSIONS: The presented ABC classification for PSI is a comprehensive classification with a high reliability and reproducibility. However, a gradual transition and potential progression between the subtypes of PSI must be considered. The reliable distinction between different subtypes of PSI based on etiology and pathomechanism provides a standardized basis for future investigations on treatment recommendations.
METHODS: All consecutive patients presenting with unidirectional PSI from June 2019 to June 2021 were included in a prospective study. No patients were excluded, leaving a consecutive series of 100 cases of PSI in 91 patients. All recorded clinical and imaging data were used to create anonymized clinical case vignettes, which were evaluated twice according to the ABC classification at the end of the recruitment period in random sequential order by 4 independent raters (2 experienced shoulder surgeons and 2 orthopedic residents) to analyze the comprehensiveness as well as inter-rater and intrarater reliability of the ABC classification for PSI and to describe differences in characteristics among subtypes. Group A was defined as a first-time singular PSI event <3 months in the past regardless of etiology and is further subdivided into type 1 and type 2 depending on the occurrence of a subluxation (A1) or dislocation (A2). Group B comprises recurrent dynamic PSI regardless of time since onset and is further subdivided by the cause of instability into functional (B1) and structural (B2) dynamic PSI. Group C includes chronic static PSI with posterior humeral decentering that can be either constitutional (C1) or acquired (C2).
RESULTS: None of the cases was deemed unsuitable to be classified based on the proposed system by the observers. After consensus agreement between the 2 expert raters, 16 cases were attributed to group A (8 type A1 and 8 type A2); 64, to group B (33 type B1 and 31 type B2); and 20, to group C (11 type C1 and 9 type C2). The expert raters agreed on the classification subtypes in 99% and 96% of the cases during the first rating and second rating, respectively (intraclass correlation coefficients [ICCs], 0.998 and 0.99, respectively). The intraobserver reliability was excellent for both raters. The beginners reached the same conclusion as the consensus agreement in 94% of the cases (ICC, 0.99) and 89% of the cases (ICC, 0.97) during the first round and 94% each (ICC, 0.97) during the second round. The intraobserver reliability was excellent for both beginners. Overall, discrepancies between raters were found between groups B1 and B2 (n = 14), groups B2 and C2 (n = 4), groups B1 and C1 (n = 1), and groups A1 and B2 (n = 1). In general, each subtype showed distinctive clinical and imaging characteristics that facilitated the diagnosis.
CONCLUSIONS: The presented ABC classification for PSI is a comprehensive classification with a high reliability and reproducibility. However, a gradual transition and potential progression between the subtypes of PSI must be considered. The reliable distinction between different subtypes of PSI based on etiology and pathomechanism provides a standardized basis for future investigations on treatment recommendations.
摘要：
背景：最近提出了ABC分类作为后肩关节不稳定（PSI）的综合分类系统。这项研究的目的是分析ABC分类的全面性以及评估者之间和内部的可靠性。
方法：在一项前瞻性研究中，纳入了2019年6月至2021年6月出现单向PSI的所有连续患者。没有患者被排除在外，在91例患者中连续留下100例病例。所有记录的临床和影像学数据用于创建匿名的临床病例插图，在招募期结束时，由四个独立的评估者按随机顺序进行了两次ABC分类评估，2名经验丰富的肩关节外科医师和2名骨科住院医师,目的是分析后肩关节不稳定ABC分类的全面性以及评估者间和评估者间的可靠性,并描述不同亚型特征的差异。A组定义为过去少于3个月的首次单发后肩不稳定事件，无论病因如何，并根据半脱位（A1）或脱位（A2）的发生进一步细分为1型和2型。B组包括复发的动态PSI,而不考虑自发作以来的时间,并且通过功能(B1)和结构(B2)动态PSI中的不稳定性的原因进一步细分。C组包括慢性静态PSI，肱骨后偏心可以是结构性的（C1）或获得性的（C2）。
结果：根据观察者提出的系统，没有一个案例被认为不适合分类。在两位专家达成共识后，将16个案例归入A组（A1：8，A2：8），64至B组（B1:33，B2:31），和20至C组(C1:11,C2:9)。在第一和第二评级期间，专家评估者在99％和96％的病例中同意分类亚型（ICC：0.998和ICC：0.99）。两个评估者的观察者内部可靠性都很好。在第一轮中，初学者在94％（ICC：0.99）和89％的案例（ICC：0.97）中达成了与共识一致的结论，在第二轮中，每个案例均为94％（ICC：0.97）。两个初学者的观察者内部可靠性都很好。总的来说,在B1组和B2组之间发现评分者之间存在差异(n=14)，B2和C2（n=4），B1和C1（n=1），以及A1和B2（n=1）。总的来说,每种亚型均显示独特的临床和影像学特征,有助于诊断.
结论：所提出的PSIABC分类是一种综合性分类，具有较高的可靠性和可重复性。然而,必须考虑PSI亚型之间的逐渐过渡和潜在进展.基于病因和病理机制的PSI不同亚型之间的可靠区别为未来的治疗建议研究提供了标准化的基础。
方法：在一项前瞻性研究中，纳入了2019年6月至2021年6月出现单向PSI的所有连续患者。没有患者被排除在外，在91例患者中连续留下100例病例。所有记录的临床和影像学数据用于创建匿名的临床病例插图，在招募期结束时，由四个独立的评估者按随机顺序进行了两次ABC分类评估，2名经验丰富的肩关节外科医师和2名骨科住院医师,目的是分析后肩关节不稳定ABC分类的全面性以及评估者间和评估者间的可靠性,并描述不同亚型特征的差异。A组定义为过去少于3个月的首次单发后肩不稳定事件，无论病因如何，并根据半脱位（A1）或脱位（A2）的发生进一步细分为1型和2型。B组包括复发的动态PSI,而不考虑自发作以来的时间,并且通过功能(B1)和结构(B2)动态PSI中的不稳定性的原因进一步细分。C组包括慢性静态PSI，肱骨后偏心可以是结构性的（C1）或获得性的（C2）。
结果：根据观察者提出的系统，没有一个案例被认为不适合分类。在两位专家达成共识后，将16个案例归入A组（A1：8，A2：8），64至B组（B1:33，B2:31），和20至C组(C1:11,C2:9)。在第一和第二评级期间，专家评估者在99％和96％的病例中同意分类亚型（ICC：0.998和ICC：0.99）。两个评估者的观察者内部可靠性都很好。在第一轮中，初学者在94％（ICC：0.99）和89％的案例（ICC：0.97）中达成了与共识一致的结论，在第二轮中，每个案例均为94％（ICC：0.97）。两个初学者的观察者内部可靠性都很好。总的来说,在B1组和B2组之间发现评分者之间存在差异(n=14)，B2和C2（n=4），B1和C1（n=1），以及A1和B2（n=1）。总的来说,每种亚型均显示独特的临床和影像学特征,有助于诊断.
结论：所提出的PSIABC分类是一种综合性分类，具有较高的可靠性和可重复性。然而,必须考虑PSI亚型之间的逐渐过渡和潜在进展.基于病因和病理机制的PSI不同亚型之间的可靠区别为未来的治疗建议研究提供了标准化的基础。
