Background Rotator cuff (RC) tears are associated with RC muscle atrophy and changes in composition that are crucial to the prognosis of RC repair. The aim of this study was to characterize muscle fiber composition in the supraspinatus (SS) muscle under tear conditions. Methods Muscle biopsies were obtained from 21 patients undergoing surgery for an RC tendon tear. Biopsies were obtained from the musculotendinous junction of the SS muscle, and control biopsies were harvested from the deltoid muscle (DT). Biopsies were immunohistochemically processed for detection of type 1 (slow type) and type 2 (fast type) fibers and analyzed using unbiased, stereological principles. We counted the total numbers of type 1 and 2 muscle fibers/mm 2 , and fiber diameter was used to estimate muscle fiber atrophy and hypertrophy. Results We found significantly more type 2 cells/mm 2 in the SS compared with the DT ( P < .01). In addition, we found a significantly higher fraction of type 1 fibers than type 2 fibers in the DT ( P < .01), whereas both fiber types were equally present in the SS. The diameters of SS cells were generally smaller than those of DT cells. Atrophy of especially SS type 2 fibers was also demonstrated. Fiber atrophy was more pronounced in men than women. Conclusion The changes in the composition of SS muscle cell types suggest a shift from type 1 to type 2 muscle fibers and atrophy of both type 1 and 2 fibers. This composition indicates loss of endurance and rapid fatigue of the SS muscle under RC tear conditions.
discussion. The content validity of the classification was assessed by comparing each subgroup classification with the intraoperative findings. The primary outcome measures were the range of movement and Mayo Elbow Performance Score (MEPS). Complications were collected as a secondary outcome. Ethical approval was obtained and data was obtained by retrospective case note review Results: Sixty patients were managed using the Wrightington classification. This comprised thirty two(53%) females and 28(47%) males with a mean age of 48 yrs (range 19-84). In order of observed frequency 20 cases (33%) were classified as type B+,18(30%) Type C,11(28%) Type B, and 7(12%) Type A. There were 3 Type D+ and 1 Type D. Fifty eight(96.7%) patients completed a minimum of 3 months follow up. Average follow up was 5.7 months (range 2-18).The average Mayo Elbow Performance Score (MEPS) at final follow up was 93(range 55-100) and the mean arc of movement was 15-131. Sub group analysis showed average MEPS of 91(65-100) in group A, 93(70-100) in group B, 92(55-100) in group B+,94 (65-100) in group C,100 in group D and 90(70-100) in group D+. The average arc of movement was 10-136 degrees in group A, 22-128 degrees in group B, 17-127 degrees in group B+, 12-134 degrees in group C, 0-130 degrees in group D and 18-131 degrees in group D+. Four patients underwent secondary surgery. One patient underwent arthrolysis with excellent outcomes, 1 patient underwent revision of radial head replacement due to over stuffing, 1 patient had non-union of radial head fixation and underwent excision surgery and 1 patient had CRPS and prominence of ulna plate and underwent removal of metal work. All 4 patients had improved outcomes with average MEPS score improvement from 65 to 94 and improved arc of motion.Conclusions: The Wrightington Classification system facilitates pattern recognition and provides an algorithm for management for these complex injuries. Our results suggest that predictably good outcomes can be achieved by application of surgical algorithms related to this classification.
Background: Rotator cuff (RC) tears are associated with RC muscle atrophy and changes in composition that are crucial to the prognosis of RC repair. The aim of this study was to characterize muscle fiber composition in the supraspinatus (SS) muscle under tear conditions. Methods: Muscle biopsies were obtained from 21 patients undergoing surgery for RC tendon tear. Biopsies were obtained from the musculotendinous junction of the SS muscle and control biopsies were harvested from the deltoid muscle (DT). Biopsies were immunohistochemically processed for detection of type 1 (slow type) and type 2 (fast type) fibers and analyzed using unbiased, stereological principles. We counted the total numbers of type 1 and 2 muscle fibers/mm 2 and fiber diameter was used to estimate muscle fiber atrophy and hypertrophy. Results: We found significantly more type 2 cells/mm 2 in the SS compared to the DT (p<0.01). In addition, we found a significantly higher fraction of type 1 fibers than type 2 fibers in the DT (p<0.01), whereas both fiber types were equally present in the SS. The diameters of SS cells were generally smaller than those of DT cells. Atrophy of especially SS type 2 fibers was also demonstrated. Fiber atrophy was more pronounced in men than women. Discussion: The changes in the composition of SS muscle cell types suggest a shift from type 1 to type 2 muscle fibers and atrophy of both type 1 and 2 fibers. This composition indicates loss of endurance and rapid fatigue of the SS muscle under RC tear conditions.
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