Magnetic resonance markers of supraspinatus muscle microvascular function and energetics following a rotator cuff tear.

Rotator cuff tears (RCT) cause pain and disability in adults. Histological studies indicate that the degenerative process following a rotator cuff tear may disrupt the vascularity and energetics of the shoulder muscles. Magnetic resonance imaging (MRI) postcontractile blood oxygen level-dependent (BOLD) response and 31phosphorus magnetic resonance spectroscopy (31P-MRS) offer methods to noninvasively assess muscle microvascular function and energetic status in vivo. This study aimed to evaluate the postcontractile BOLD response and 31P-MRS as potential markers of microvascular function and energetic status of the supraspinatus muscle in individuals with chronic full-thickness supraspinatus tendon tears and healthy individuals without a tear. Using a 3-T MR Phillips system, all participants performed five 2-s maximal isometric shoulder abductions to obtain a postcontractile BOLD response using a custom MR-compatible dynamometer. Dixon fat/water imaging was used to quantify muscle fat fraction. A surface 31P-MRS coil acquired spectra concentrations of high-energy phosphates, and intracellular pH from the supraspinatus and surrounding muscles. Results revealed a lower peak BOLD response (P < 0.01) and longer time-to-peak (P = 0.02) in RCT, indicating impaired microvascular function. Analysis of 31P-MRS spectra showed elevated unlocalized Pi/PCr (P = 0.04) and phosphodiester (P < 0.01) concentrations in RCT, consistent with muscle damage. No differences in muscle PCr (P = 0.30) or pH (P = 0.50) were observed. Overall, these findings support that the postcontractile BOLD response and 31P-MRS may be valuable markers to assess shoulder muscle health status and evaluate therapeutic interventions aimed at improving clinical outcomes following a rotator cuff tear.NEW & NOTEWORTHY This study utilized magnetic resonance to examine the postcontractile blood oxygen level-dependent (BOLD) response and 31phosphorus magnetic resonance spectroscopy (31P-MRS) in individuals with chronic, full-thickness supraspinatus tendon tears and individuals without a tear. Our findings indicate an impaired microvascular function and an altered energetic status in those with rotator cuff tears. Postcontractile BOLD response and 31P-MRS may be valuable markers to assess shoulder muscle health and healing potential following a rotator cuff tear.