Inter- and Intrarater Reliability of the Acromioclavicular Joint Injury Classification on Anteroposterior...

Prior research has shown that Acromioclavicular (AC) joint injuries represent a significant portion of shoulder trauma encountered in emergency departments, often resulting from direct falls onto the lateral aspect of the shoulder. Clinicians frequently utilize standardized radiographic systems to categorize these ligamentous disruptions and guide subsequent management decisions, ranging from conservative rehabilitation to surgical reconstruction. Existing literature regarding the consistency of these diagnostic frameworks often relies on restricted or highly selective patient cohorts, which may not accurately reflect the variety of injuries seen in general practice. Such limitations hinder the generalizability of findings to broader, heterogeneous urban populations requiring acute orthopedic care across diverse clinical settings. Accurate classification remains essential for distinguishing between stable and unstable injuries that necessitate surgical intervention to restore joint stability and function. The lack of large-scale, prospective reliability data for the Rockwood system on standard radiographs creates uncertainty in diagnostic confidence for many practitioners. This absence of evidence motivated the current investigation into how consistently medical professionals apply established grading criteria in a real-world clinical setting.

This investigation evaluates the interrater and intrarater reliability of the Rockwood classification system for Acromioclavicular (AC) joint injuries using standard Anteroposterior (AP) radiographs. Researchers focused on a large, consecutive cohort of 268 patients presenting to an urban orthopedic emergency department with suspected shoulder trauma over a one-year period. The study seeks to determine if clinical experience or medical specialty influences the consistency of radiographic interpretation among orthopedic consultants, residents, and radiologists. By analyzing a diverse group of raters, the work clarifies the reproducibility of diagnostic assessments in high-volume trauma environments like Oslo University Hospital. Investigators specifically targeted the reliability of nonweightbearing imaging protocols for identifying various injury grades without the need for additional stress views. This approach addresses the need for robust validation of common diagnostic tools in everyday clinical practice to ensure patient safety and effective treatment planning. The project aims to establish a benchmark for diagnostic agreement that can inform future clinical guidelines and educational training for musculoskeletal specialists.

The research team prospectively registered 287 consecutive Acromioclavicular (AC) joint injuries from a total pool of 2650 shoulder trauma cases at Oslo University Hospital. Final analysis included 268 patients who underwent two standardized nonweightbearing Anteroposterior (AP) radiographs with the X-ray beam tilted 15 degrees in cephalic and caudal directions. Six independent observers, comprising two orthopedic consultants, two orthopedic residents, and two musculoskeletal radiology consultants, performed the radiographic assessments. These evaluators classified the injuries according to the Rockwood system during two distinct sessions separated by a minimum interval of six weeks. All raters remained blinded to their previous scores and the assessments of their colleagues to ensure objective data collection and minimize bias. Statistical analysis utilized Cohen kappa (k) values to quantify both the agreement between different observers and the consistency of individual raters over time. The study stratified raters based on their specific medical specialty and years of clinical experience to identify potential variations in diagnostic accuracy.

Radiographic evaluation of the cohort demonstrated substantial interrater reliability for the Rockwood classification across all participating medical specialties and experience levels. Interrater agreement improved between the first and second rounds, rising from 92% (k = 0.66) to 94% (k = 0.73) for the entire group of six raters. Musculoskeletal radiology consultants achieved the highest initial interrater consistency with a kappa value of 0.70, while orthopedic residents showed the greatest improvement in round two. Intrarater reliability remained high across all groups, with individual kappa values ranging from 0.66 to 0.84, indicating strong internal consistency over time. One radiology consultant reached an almost perfect level of internal consistency with a kappa of 0.84, significantly outperforming several orthopedic counterparts. However, the raters exhibited low majority agreement when identifying Rockwood type II injuries, with no cases achieving consensus among five or six observers. These findings indicate that while overall reliability is strong, specific injury grades present persistent diagnostic challenges that may require more nuanced assessment.

Nonweightbearing unilateral Anteroposterior (AP) radiographs provide a reliable foundation for classifying Acromioclavicular (AC) joint injuries using the Rockwood framework in an urban population. The substantial levels of agreement observed among consultants and residents suggest that this diagnostic approach is robust across different levels of clinical experience. Practitioners should remain aware of the inherent difficulty in consistently identifying type II injuries, which may require additional imaging or clinical correlation to avoid misdiagnosis. The observed improvement in reliability during the second round of assessments suggests that familiarity with the classification criteria enhances diagnostic precision among all medical specialties. These results support the continued use of standardized AP views in urban emergency settings for initial injury grading without the necessity of weightbearing stress radiographs. Future efforts might focus on refining the criteria for intermediate injury types to further reduce interobserver variability and improve clinical outcomes. This study reinforces the utility of the Rockwood system as a stable tool for orthopedic trauma assessment in high-volume medical centers.