External rotation in the glenohumeral joint during elevation of the arm

Objective. To describe patterns of external rotation during humeral elevation, and to compare motion patterns. Design. Patterns of external rotation during forward flexion, scapular abduction and abduction in the frontal plane are described with P-spline curves with an ≈95% confidence interval. Background. External rotation of the humerus is an essential part of humeral elevation. Standard clinical assessment of external rotation provides insufficient information to describe external rotation patterns which may be essential for insight in shoulder disorders. Methods. The dominant and non-dominant arms of thirty subjects are measured, using a three-dimensional electromagnetic movement recording system. Results. Overall group patterns demonstrate that humeral elevation in all planes is accompanied by about 55° of external rotation, and each elevation plane has its own typical pattern. The dominant and non-dominant sides are comparable and can be combined. Conclusions. There are specific external rotation patterns for each elevation plane. Curves representing the ≈95% confidence intervals make comparison between groups possible. This method can therefore possibly be used to study the external rotation patterns in groups with certain shoulder disorders to evaluate the results of before and after treatment.