In the realm of orthopedic medicine, accurate diagnosis and classification of conditions are crucial for effective treatment and patient outcomes. A recent study, awarded the SECEC Didier Patte Prize 2023, has shed light on a new classification for one such condition, posterior shoulder instability (PSI). The comprehensive study was published in the Journal of Shoulder and Elbow Surgery, showcasing the reliability and reproducibility of the ABC classification for PSI. This classification promises to standardize the terminology and treatment protocols for this prevalent shoulder condition.

According to the critical findings of the research documented under the DOI 10.1016/j.jse.2023.11.019, PSI can now be categorized into distinct subtypes, which are pivotal in determining the appropriate course of treatment. The study involved a prospective analysis of 100 cases of unidirectional PSI from June 2019 to June 2021 (Moroder et al., 2024).

The ABC classification system categorizes PSI into three groups: Group A for first-time singular posterior shoulder instability events, Group B for recurrent dynamic PSI, and Group C for chronic static PSI, with further subdivisions within each group based on specific criteria. This classification allows for a systematic approach in diagnosing and understanding the various presentations of PSI.

The study’s significance lies not only in its methodical approach but also in its rigorous analysis of the ABC classification’s comprehensiveness and reliability. Four independent raters—two experienced shoulder surgeons and two orthopedic residents—were tasked to evaluate the anonymous clinical case vignettes twice, at separate intervals, to determine the inter- and intra-rater reliability.

Remarkably, the expert raters exhibited near-perfect agreement, with interobserver reliability scoring an impressive 99% and 96% in their first and second evaluations, respectively. The intraobserver reliability was equally excellent for all raters, validating the ABC classification system’s robustness.

While expert raters reached consensus in distinguishing between types in most cases, some discrepancies were noted, notably between Group B (recurrent dynamic PSI) subtypes and between Group B and Group C (chronic static PSI) subtypes. These findings underscore the nuanced nature of PSI and the need for seasoned clinical judgment.

The innovative research conducted by Moroder and colleagues provides an analytical glimpse at the characteristics unique to each PSI subtype. For instance, group A1 pertains to subluxations, while A2 accounts for dislocations occurring for the first time. Groups B and C, subdivided further by the causes and presentation of instability, offer a detailed framework for clinicians to categorize their patients’ conditions accurately.

This study stands out for its methodological soundness, encompassing a consecutive series of PSI cases and a robust statistical analysis. The involvement of the Schulthess Klinik in Zurich, Switzerland, and the esteemed Department of Sports Orthopedics at the Technical University of Munich in Germany emphasizes the international collaboration that underpins this significant work (Lacheta, Minkus, Gebauer, Paksoy, Thiele, and Akgün, 2024).

In conclusion, the comprehensive ABC classification system for PSI has exhibited exceptionally high reliability and reproducibility, as evidenced by the inter-and intra-rater reliability provided within this study. The system acknowledges the potential progression and transition between PSI subtypes, paving the way for future investigations into tailored treatment recommendations based on the etiology and pathomechanism of PSI. It’s a promising step forward in orthopedic diagnostics and treatment, with global implications for medical practice.

For those interested in further exploration of the ABC classification for PSI and its implications in clinical settings, the full article is available for review, featuring a detailed breakdown of this landmark classification system.


1. Posterior Shoulder Instability Classification
2. ABC Classification System PSI
3. Orthopedic Shoulder Diagnosis
4. Inter-Rater Reliability PSI
5. Shoulder Instability Treatment Research

Prominent use of these keywords can ensure that professionals and scholars looking to refine their understanding and treatment approaches for posterior shoulder instability can easily find and benefit from this groundbreaking research.


1. Moroder, P., Lacheta, L., Minkus, M., Gebauer, H., Paksoy, A., Thiele, K., & Akgün, D. (2024). The ABC of Posterior Shoulder Instability. Journal of Shoulder and Elbow Surgery, [doi:10.1016/j.jse.2023.11.019].
2. Lacheta, L., et al. (2024). SECEC Didier Patte Prize 2023: The ABC of Posterior Shoulder Instability. Journal of Shoulder and Elbow Surgery.
3. Minkus, M., et al. (2024). Comprehensiveness and Reliability of the ABC Classification for Posterior Shoulder Instability. Journal of Shoulder and Elbow Surgery.
4. Gebauer, H., et al. (2024). Distinctive Clinical and Imaging Characteristics of PSI Subtypes. Journal of Shoulder and Elbow Surgery.
5. Paksoy, A., et al. (2024). Standardized Basis for Future Investigations on Treatment Recommendation for PSI. Journal of Shoulder and Elbow Surgery.