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External rotation in the glenohumeral joint during elevation of the arm
M Stokdijk1, P H C Eilers, J Nagels
1Department of Orthopaedics, Orthopaedic Laboratory, B0-Q-56, Leiden University Medical Center, P.O. Box 9600, 2300 RC, Leiden, The Netherlands. mariellestokdijk@hotmail.com
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 approximately 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 degrees 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 approximately 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.
Relevance:
The method presented in this paper can be used to study external rotation patterns in healthy shoulders and in shoulders with a specific disorders to gain more insight, to define functional treatment, and to evaluate the results of treatment.