2017 ISAKOS Biennial Congress ePoster #2039

 

Does Anterior Shoulder Dislocation Occur In External Rotation And Abduction?

Alberto E. Martinez, MD, Bogota COLOMBIA
Juan Borda Sanchez, Bogota COLOMBIA
Giusseppe Alajmo, MD, Bogota COLOMBIA

Medsport Colombia, Bogota, COLOMBIA

FDA Status Not Applicable

Summary

Anterior shoulder dislocation does not occur in abduction and external rotation.

Abstract

Background

Traditionally, combined maximal external rotation and abduction has been described as the position in which the shoulder dislocates in patients with anterior instability. But under anesthesia physical examination has shown anterior translation in other ranges of motion.

Materials And Methods

We studied 38 patients with isolated anterior shoulder instability by physical evaluation under anesthesia before arthroscopic Bankart surgery. Patients were examined by the senior author (AMT) evaluating anterior humeral head translation in two previously established positions. First, 90 degrees abduction and 90 degrees external rotation and the second neutral rotation, 40 degrees abduction and 60 degrees flexion. Anterior translation was measured with the Hawkins scale.

Results

In the first position no patient presented anterior translation of the humeral head on physical exam, but conversely in the second position 34 patients (89.4%) had grade II anterior translation and 4 patients (10.4%) grade III.

Discussion

Patients under general anesthesia with muscle relaxation are subjected to only passive restraints that control joint stability. Therefore under these circumstances, our confirmed anterior instability group of patients, should easily be dislocated in the position in which anterior dislocation occurs while awake. Our study shows that no patient presented anterior translation in the classically described position of combined abduction and external rotation. All patients presented some grade of instability in the middle range of motion.

Conclusions

Based on our findings, anterior dislocation of the shoulder cannot occur in maximal abduction and external rotation. We believe there is a need for further biomechanical studies to improve understanding of anterior shoulder instability.