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Clinical Predictors of C5 Root Viability in Pan-brachial Plexus Injuries
Kitty Wu, MD, FRCSC1; Derek B. Asserson, MD2; Michelle Kircher, PNR1; Allen T Bishop, MD3; Robert J. Spinner, MD4; Alexander Y Shin, MD3
1Mayo Clinic, Rochester, MN; 2California Northstate University, Elk Grove, CA; 3Microvascular Research Laboratory, Mayo Clinic, Rochester, MN; 4Department of Physical Medicine and Rehabilitation, Mayo Clinic, Rochester, MN

Introduction: The ability to pre-operatively distinguish between pre-ganglionic and post-ganglionic injury patterns is crucial to determining the optimal reconstructive strategy in pan-brachial plexus injuries. We hypothesized that preserved rhomboid and serratus function on clinical examination, Tinelís test, and absence of a pseudomeningocele on CT myelogram would be predictive of a viable C5 nerve root. Materials & Methods: All patients with pan-brachial plexus injuries from a single institution between 2000 and 2018 were retrospectively reviewed. Patient demographic information, injury severity score, clinical examination (rhomboid MRC strength, serratus MRC strength, Hornerís syndrome, Tinelís test), diagnostic imaging (hemidiaphragmatic elevation on chest x-ray, CT myelogram), and EDX were recorded. Results were compared to intraoperative findings and nerve monitoring at the time of surgical exploration to determine C5 root viability and suitability for grafting. Fisherís exact test and Kruskal-Wallis rank sum test were used to identify significant factors for regression analysis. A binomial least absolute shrinkage and selection operator (LASSO) regression model was then used to identify predictors of a viable C5 nerve root. Predictive performance was assessed using area under the curve (AUC) under the receiver operating characteristic curve. Results: A total of 362 patients (mean age 31.5 years; 53 females, 309 males; mean ISS 17.2) were included. 29.6% of patients had a viable C5 nerve root. CT myelogram showing intact C5 roots (Odds ratio [OR] 1.8) and C6 roots (OR 1.1) and Tinelís test (OR 1.2) were predictive of anatomically viable C5 roots suitable for use in reconstruction. Conversely, cervical paraspinal fibrillation on EMG (OR 0.8) and hemidiaphragmatic elevation (OR 0.9) were predictive of C5 root avulsions. Rhomboid and serratus MRC strength, Hornerís syndrome, rhomboid fibrillations on EDX were not correlated with either injury pattern. The LASSO model had moderate discriminative power (AUC 0.69). Conclusions: Clinical exam findings of a Tinelís test, CT myelogram showing intact C5 and C6 roots were predictive of anatomically viable C5 roots while hemidiaphragmatic elevation and paraspinal fibrillations on EMG were predictive of root avulsions.


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