NI FEATURE: THE EDITORIAL DEBATE III-- PROS AND CONS
|Year : 2019 | Volume
| Issue : 7 | Page : 27--28
Restoring movements at the shoulder joint in pan-brachial plexus injuries: Focusing on the complex kinesiology
Manish Singh Sharma
Department of Neurosurgery, Mayo Clinic Health System, Mankato, Minnesota, USA
Dr. Manish Singh Sharma
Department of Neurosurgery, Mayo Clinic Health System, Mankato, Minnesota 56001
|How to cite this article:|
Sharma MS. Restoring movements at the shoulder joint in pan-brachial plexus injuries: Focusing on the complex kinesiology.Neurol India 2019;67:27-28
|How to cite this URL:|
Sharma MS. Restoring movements at the shoulder joint in pan-brachial plexus injuries: Focusing on the complex kinesiology. Neurol India [serial online] 2019 [cited 2020 Aug 13 ];67:27-28
Available from: http://www.neurologyindia.com/text.asp?2019/67/7/27/250711
The authors in their paper “Functional outcome of spinal accessory nerve transfer to the suprascapular nerve to restore shoulder function: results in upper and complete traumatic brachial plexus palsy in adults,” present data that indicates no statistical difference in outcome as regards to shoulder abduction between patients in these two cohorts. External rotation was superior in the former cohort.
These results correlate with those in available literature. The 35% failure rate of abduction in patients with an upper trunk injury may be surprising to current nerve surgeons and may be attributable to techniques and learning curves, as cases in this series date back to the year 2004. Bertelli et al., found that the failure rate was 25% in cases in whom surgery had been performed from 2002 to 2004. This improved to 5% when an oblique incision was used that extended from the point at which the plexus crossed the clavicle to the anterior border of the trapezius muscle. Detaching the trapezius from the clavicle helped to expose the suprascapular nerve at the suprascapular fossa- an approach that has been advocated by other groups. Regardless, the harsh reality is that external rotation does not keep pace with abduction regardless of electromyogram (EMG) evidence of re-innervation. It may be argued that the former may be functionally more important as it enables the limb to move away from the torso to help with basic functions such as eating. The conclusion of the current paper is supported by data from the Mayo Clinic group where they found that the only predictor of improvement in external rotation was an isolated upper trunk injury. Improved external rotation was evident in 76%, 37% and 26% of upper trunk, C5-C6-C7 and panplexus injuries, respectively (P  This difference stands despite the fact that a 35 degree range of external rotation was considered useful whereas the current paper raises the bar to 55 degrees.
It would have been interesting to note the reasons why patients with isolated upper trunk injuries only underwent a spinal accessory nerve transfer to the suprascapular nerve without concurrent axillary nerve neurotization. I suspect there may be a historical skew at play here. Donors for the axillary nerve are typically plentiful and can include the triceps branch of the radial, the medial pectoral, the motor intercostal, the thoracodorsal and the contralateral C7 nerves.
From a theoretical point of view, it remains interesting that a range of motion of greater than 30 degrees is considered useful, not only in this paper but also in literature. Classical anatomical texts state that the supraspinatus muscle initiates the first 15-30 degrees of shoulder abduction. Beyond this, the deltoid abducts from 30-90 degrees, after which the trapezius and serratus anterior hyper-abduct the shoulder by acting as a mechanical couple on the scapula against the chest wall. Shoulder kinesiology may be far more complex. A recent meta-analysis of muscle moment arms across the glenohumeral joint indicated that the subscapularis was an adductor in the coronal plane and an abductor in the scapular plane.
EMG studies of these muscles as well as a careful analysis of trick compensatory movements at last clinical follow up could provide clearer data in future studies to determine whether or not possible spontaneous regeneration of multiple innervating components of the brachial plexus with resulting poly-muscle recovery may be contributing to some of these clinical outcomes.
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