Will preoperative combined MRI and high-resolution ultrasonography redefine brachial plexus imaging? A comparative study of preoperative MRI versus combined MRI and high-resolution ultrasonography in assessing usable C5, C6 root-stumps for intra-plexal nerve grafting

Abstract

To compare the intraoperative findings with the preoperative imaging in detecting usable root stumps using magnetic resonance imaging (MRI) alone versus MRI combined with high-resolution ultrasonography (HRUS) in adults undergoing post-traumatic brachial plexus (BP) surgery. Further, when root stumps were present, the reliability of their measurements using both imaging methods was compared to their intraoperative length. A consecutive group of adults who were planned for post-traumatic BP surgery between July 2015 and April 2016 were evaluated prospectively. They underwent preoperative MRI and HRUS and the agreement (kappa value) between these imaging methods and their intraoperative findings in categorising roots were then compared. When stumps were present, the reliability of the extraforaminal measurements by each method were compared to their corresponding intraoperative stump length using intraclass correlation coefficients (ICC), and Bland-Altman plots. Of the initial 60 patients, 48 patients with 82 roots were included in the study. Greater agreement was observed between HRUS and intraoperative findings in categorising BP root stumps (kappa value 0.70, SE 0.07) versus MRI and intraoperative findings (kappa value 0.42, SE 0.07). Similarly, there was a higher correlation between HRUS and intraoperative findings (ICC: 0.94, p<0.001) than that of MRI and intraoperative findings (ICC: 0.53, p<0.001) regarding stump length measurements. Combining HRUS with MRI in the preoperative imaging of the adult BP injury can better predict the presence of usable nerve root stumps for intra-plexal nerve grafting. HRUS also gave reliable preoperative stump length measurements, and it was determined that a stump should be at least 1.3 cm to be deemed usable for nerve grafting.