Evaluation of the Circles Measurement and the ABC Classification of Acromioclavicular Joint Injuries.

Murphy, Richard J; Moor, Beat Kaspar; Lesniewski, Piotr J; Hayoz, Annabel; Alcantara, Wolfan; Zumstein, Matthias A. (2021). Evaluation of the Circles Measurement and the ABC Classification of Acromioclavicular Joint Injuries. The American journal of sports medicine, 49(6), pp. 1619-1625. Sage 10.1177/03635465211003300

Preview

Text 03635465211003300.pdf - Published Version Available under License Publisher holds Copyright. Copyright: The Author(s) Download (1MB) | Preview

BACKGROUND

Acromioclavicular joint (ACJ) injuries are common. Despite this, it remains unclear how best to assess, classify, and manage these cases. A simple, reliable, valid, and accurate radiographic parameter to measure ACJ displacement would allow improved consistency of diagnosis and subsequent treatment pathways.

PURPOSE

To evaluate "the circles measurement" and associated "ABC classification" as a tool for assessing ACJ displacement and injury classification.

STUDY DESIGN

Descriptive laboratory study.

METHODS

The circles measurement is taken from a lateral Alexander radiograph of the shoulder. The measurement is the center-to-center distance between 2 circles drawn to define the lateral extent of the clavicle and the anteromedial extent of the acromion; it is independent of the displacement plane, judging total ACJ displacement in any direction rather than trying to quantify vertical and/or horizontal displacement. When utilized clinically, the circles measurement is a single measurement calculated as the difference between values recorded for the injured and uninjured sides. Validation of the circles measurement was performed using lateral Alexander radiographs (including ±20° projection error in all planes) and computed tomography of standardized ACJ injury simulations. We assessed inter- and intrarater reliability, convergent validity, and discriminant validity of the circles measurement and subsequently generated a classification of ACJ injury based on displacement.

RESULTS

Reliability and validity of the circles measurement was excellent throughout. Interrater reliability (ICC [intraclass correlation coefficient] [2,1], 95% CI; n = 78; 4 observers) was 0.976 (0.964-0.985). Intrarater reliability (ICC [2,1]; 95% CI; n = 78; 2 measures) was 0.998 (0.996-0.998). Convergent validity (Pearson correlation coefficient, r) was 0.970 for ideal radiographs and 0.889 with ±20° projection error in all planes. Discriminant validity, with 1-way analysis of variance, showed a P value of <.0001 and effect size (η2) of 0.960, with the ability to distinguish between the previously defined stable (Rockwood IIIA) and unstable (Rockwood IIIB) injuries. The results permitted objective, statistically sound parameters for the proposed ABC classification system.

CONCLUSION

The circles measurement is a simple, reliable, valid, accurate, and resilient parameter for assessing ACJ displacement and can be used in conjunction with the proposed ABC classification to define ACJ injuries more accurately and objectively than previously described.

CLINICAL RELEVANCE

This novel parameter has the potential to standardize the initial assessment and possibly the subsequent clinical management of ACJ injuries, in addition to providing a standardized measure for future research.

Interest & Impact

Downloads

615 since deposited on 15 Nov 2021
327 in the past 12 months

Citations

5 Citations in Web of Science ®
6 Citations in Scopus

Search

in Google Scholar™

Services

Actions (login required)

Edit item

Actions (login required)

Edit item