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Background: Isotonic exercise is commonly adopted for shoulder rehabilitation, but the efficacy of isokinetic exercise for rehabilitation has not been evaluated. Purpose: To evaluate the efficacy of isotonic and isokinetic external shoulder rotation exercises. Study Design: Controlled laboratory study. Methods: Using surface electromyography (EMG) and the Biodex system, we investigated the EMG amplitude of the infraspinatus (IS), total work (tWK), and EMG(IS)/tWK ratio and examined the relative IS and posterior deltoid (PD) contributions to all exercises. A total of 24 healthy participants without musculoskeletal injuries were included. Participants performed isotonic external shoulder rotation at 10%, 20%, 30%, 40%, and 50% of the maximum voluntary isometric contraction (MVIC) as well as isokinetic external shoulder rotation at angular velocities of 60, 120, 180, 240, and 300 deg/s. Levels of intensity were classified from 1 to 5: level 1 corresponded to 10% of the MVIC and a 300-deg/s angular velocity; level 2 corresponded to 20% MVIC and 240 deg/s; level 3 corresponded to 30% MVIC and 180 deg/s; level 4 corresponded to 40% MVIC and 120 deg/s; and level 5 corresponded to 50% MVIC and 60 deg/s. Normalized IS and tWK amplitudes were calculated for each exercise. Results: During isotonic exercise, the EMG(IS)/tWK ratio significantly decreased from level 5 to 3, 2, and 1; from level 4 to 2 and 1; and from level 3 to 1. During isokinetic exercise, the EMG(IS)/tWK ratio at level 3 was greater than that at all other levels except level 1. Statistical differences were found between isotonic and isokinetic modes at levels 1, 2, and 3. The IS/PD activation ratios were not significantly different between exercise modes at any level. Conclusion: Isokinetic resistance may provide more effective stimulation of the IS muscle compared with isotonic resistance. Clinical Relevance: Isokinetic exercise needs to be considered as a method of rehabilitation that effectively increases infraspinatus muscle activity.

Background:Previous studies on massive rotator cuff tears have not addressed the outcomes of tears extending to the subscapularis tendon.Hypothesis:The retear rate in patients with a massive posterosuperior rotator cuff tear combined with a subscapularis tear is higher than that in patients with a massive posterosuperior rotator cuff tear with an intact subscapularis tendon.Study Design:Cohort study; Level of evidence, 3.Methods:Data were collected and analyzed from 92 consecutive patients who underwent arthroscopic repair of a massive posterosuperior rotator cuff tear. Patients were divided into 3 groups according to the status of the subscapularis tendon: intact subscapularis tendon (I-massive tear; n = 42), tear involving half or less than half of the subscapularis tendon (S-massive tear; n = 22), and tear involving more than half of the subscapularis tendon (L-massive tear; n = 28). The integrity of the rotator cuff was determined by ultrasonography at 4.5 and 12 months or later after surgery. Clinical evaluations were performed using the visual analog scale (VAS) pain score, the American Shoulder and Elbow Surgeons (ASES) score, the Constant score, and active shoulder range of motion. Data were collected on the day before surgery and at final follow-up (at least 24 months postoperatively).Results:A total of 25 retears (27%) were identified based on an ultrasonographic evaluation. Although statistical significance was not found, there was a trend toward a higher retear rate in patients with an L-massive tear (43%) compared with those with an S-massive tear (18%; P = .050) or I-massive tear (21%; P = .059) at final follow-up. The subclassification of retears according to the involved tendons revealed that subsequent retears of the subscapularis tendon were noted only in patients with an L-massive tear. In patients with an L-massive tear, postoperative data comparison between patients with intact subscapularis tendons and those with failed subscapularis tendons revealed that a significant difference was noted in the VAS (1.1 vs 3.8, respectively) and ASES (90.6 vs 58.5, respectively) scores. The improvement in clinical scores after repair was statistically significant in all groups but not different between the groups.Conclusion:The arthroscopic repair of massive tears results in substantial improvements in shoulder function, regardless of the presence of combined subscapularis tears. However, this study showed a trend toward a high failure rate for the repair of massive posterosuperior rotator cuff tears extending over half of the subscapularis tendon. Therefore, other treatment options should also be considered for this type of rotator cuff tear.