Analysis of shoulder abduction by dynamic shoulder radiograph following suprascapular nerve repair in brachial plexus injury.

BACKGROUND: Suprascapular nerve repair is a widely-prioritized procedure for shoulder reconstruction following brachial plexus injury. Although this procedure only reconstructs glenohumeral joint motion, the standard clinical assessment of shoulder function also includes the scapulothoracic joint contribution. The purpose of this preliminary study was to develop an objective method to accurately analyze shoulder abduction following suprascapular nerve repair in brachial plexus injury patients. METHODS: We introduced an objective method to accurately analyze independent shoulder abduction performed by supraspinatus muscle with the help of dynamic shoulder radiography. Antero-posterior radiographs of both shoulders in adduction and maximal active abduction were obtained. Five parameters were measured. They included global abduction, abduction in glenohumeral, scapulothoracic and clavicular joints along with lateral flexion of thoracic spine. Data were analyzed to distinguish glenohumeral joint contribution from that of scapulothoracic motion. The detailed biomechanics of glenohumeral motion were also analyzed in relation to scapulothoracic motion to separately define the contribution of each in global shoulder abduction. RESULTS: The test-retest, intra-examiner and inter-examiner reliabilities of the measurements were assessed. Intra-class correlation coefficient, Bland-Altman plots and repeatability coefficients showed excellent reliability for each parameter. The range of glenohumeral abduction showed high correlation to subtraction of the range of scapulothoracic from the range of global abduction. However, not all negative ranges of glenohumeral abduction meant non-recovery after nerve repair, because scapulothoracic motion contributed in parallel but not uniformly to global shoulder motion. CONCLUSION: The conventional measurement of shoulder global abduction with goniometer is not an appropriate method to analyze the results of suprascapular nerve repair in brachial plexus palsy patients. We recommend examination of glenohumeral and scapulothoracic motions separately with dynamic shoulder radiographic analysis. With scapulothoracic contribution to the global shoulder motion, the glenohumeral motion can be wrongly assessed.