Summary

The ISAKOS subclassification of Rockwood type III AC joint dislocations in a stable type A and an unstable type B is not clinically relevant.

Abstract

Background

The treatment of Rockwood type III AC joint dislocations has been a subject of controversy for decades. To assess this problem ISAKOS upper extremity committee in 2014 suggested a subclassification of the injury in a stable type A recommended non-surgical treatment and an unstable type B recommended surgical treatment, defined by the presence of scapular dyskinesis and overriding of the clavicle to acromion on a modified lateral radiograph. The objective of the study was to investigate if this sub-classification is clinically relevant.

Methods

This was a prospective cohort study. Inclusion criteria were patients aged 18-60 with trauma to the shoulder with subsequent onset of pain within the past 7 days and a radiograph from the Emergency Room revealing >50% superior displacement of the clavicle to the acromion. All patients were treated non-surgically with 3 months of home-based training and with the option of delayed surgical intervention. Patients were assessed at baseline and at follow-ups 6 weeks, 3 months, 6 months and 1 year after the injury. At 6 weeks follow-up patients were were categorized as stable according to the ISAKOS classification if they presented with no scapular dyskinesis and no overriding of the clavicle to the acromion and unstable if they presented with any of the two. The primary outcome was the Western Ontario Shoulder Instability Index (WOSI) score (0-100%, 100% being the best). Between-group analyses were performed with students’ t-test for continuous and normally distributed data, Mann-Whitney U test for skewed data and the Fishers exact test for categorical data. ClinicalTrials registration NCT03727178. This publication concerns objective 1.

Results

Ninety-five patients, male:female ratio 9.6:1, were included. The Rockwood classification was not consistent over time and changed in 30/95 of cases between type III and V, why both type III and V were included. At the 6 weeks follow-up 20 patients were classified as stable and 68 were classified as unstable. There was a statistically significant but not clinically relevant difference in WOSI score between the two groups at 6 months (p=0.03), but not at 3 months and 1 year. No patients from the stable group were referred for surgery. From the unstable group, 9/68 (13%) had surgery at a mean of 189 SD 99 days after the injury. Patients presenting with scapular dyskinesis had worse WOSI scores at all time-points compared to those without scapular dyskinesis.

Conclusion

The ISAKOS subclassification of Rockwood type III in a stable type A and an unstable type B is not clinically applicable. The presence of scapular dyskinesis was associated with an inferior result.