On-line version ISSN 2309-8309
SA orthop. j. vol.8 n.3 Pretoria Jan. 2009
J de BeerI; MG Pritchard II; CP RobertsII; DF du ToitIII
IMMed (Orthop); Orthopaedic Surgeon. Cape Shoulder Institute, Panorama, South Africa
IIFRCS (Tr & Orth); Shoulder Fellow. Cape Shoulder Institute, Panorama, South Africa
IIIDepartment of Anatomy and Histology, University of Stellenbosch, South Africa
The measurement of external rotation of the shoulder is commonly performed in two ways: with the arm adducted or with the arm abducted to 90°. This measurement forms an important part of the assessment of shoulder function.
It has been shown that the observer reliability of external rotation measurement is poor.1-4 Following the observation that the range of external rotation of the shoulder with the arm adducted altered depending on the exact position of the arm in the sagittal plane, we conducted a study to quantify the effect of a small increment of forward flexion (15°) on the range of external rotation.
External rotation of the shoulder was measured in 40 asymptomatic shoulders and 20 'frozen' shoulders with the arm in a vertical position and in 15° of forward flexion. The range of external rotation decreased significantly in forward flexion in both groups. External rotation decreased by an average of 16.9° in the asymptomatic group and 13.5° in the frozen shoulder group.
This study has shown that the sagittal position of the arm has an effect on the range of external rotation of the adducted shoulder. This may account for some of the observer variation in its measurement and affect the scores of certain outcome measures.
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Dr J de Beer
Cape Shoulder Institute
PO Box 15741
Tel: +27 21 911-1017; Fax: + 27 21 911-1019
The content of this article is the sole work of the author. No benefits of any form have been derived from any commercial party related directly or indirectly to the subject of this article.