Quantitative MRI Assessment of the Infraspinatus and Teres Minor in Massive Rotator Cuff Tear and Its Significance in Clinical Outcome After Rotator Cuff Repair.

Abstract

BACKGROUND\nTeres minor (TM) muscle hypertrophy in large-to-massive rotator cuff tears (RCT) has been considered a compensatory change to atrophy of the infraspinatus (ISP). However, few reports have assessed its relation to the prognosis after rotator cuff repair.\n\n\nMETHODS\nA total of 139 patients who underwent arthroscopic repair of large-to-massive RCT involving the ISP between January 2013 and December 2015 were retrospectively investigated. Occupational ratios of the ISP (OR_ISP) and TM (OR_TM) were measured by sagittal magnetic resonance imaging (MRI). Rotator cuff healing was evaluated by MRI one year postoperatively, and functional outcomes using the simple shoulder test (SST) and Constant score and ER power by isokinetic muscle performance test (IMPT) were measured.\n\n\nRESULTS\nA total of 116 patients completed the MRI and IMPT at one year postoperatively, and functional scores were measured at least two years postoperatively. Of these, the repaired tendon had not healed in 34 patients (29%). There was a highly negative correlation between OR_ISP and OR_TM both pre-and postoperatively (Pearson correlation = -0.52, -0.54, respectively). Preoperative OR_ISP was significantly higher in the healed than in the healing failure group (0.47 ± 0.10 vs. 0.41 ± 0.12, p = 0.02); however, postoperative OR_ISP, and pre-and postoperative OR_TM were not. The preoperative OR_ISP cut-off value for healing was 0.46. For functional outcomes, only postoperative OR_ISP showed a statistical correlation with SST, Constant score (p = 0.04, 0.03, respectively), and ER power (p = 0.02).\n\n\nCONCLUSION\nTM muscle hypertrophy in large-to-massive RCT appears to be a compensatory change in the progression of atrophy of the ISP muscle and was not a significant indicator of either better healing of the repaired rotator cuff tendon or better function. Only preoperative OR_ISP was an independent prognostic factor affecting rotator cuff healing after repair of large-to-massive RCT.