Background: Superior capsular reconstruction (SCR) has been gaining popularity as a treatment for irreparable rotator cuff tears (RCTs), especially in younger patients. This biomechanical study aimed to investigate how SCR affects functional abduction force, humeral head migration, and passive range of motion following an irreparable RCT. We hypothesized that SCR will restore these parameters to nearly intact shoulder levels. Methods: Six fresh-frozen cadaveric shoulders were evaluated using a custom biomechanical testing apparatus. Each shoulder was taken through 3 conditions: (1) intact (control); (2) irreparable, complete supraspinatus (SS) tear; and (3) SCR. Functional abduction force, superior humeral head migration, and passive range of motion, including axial shoulder rotation, were measured in static condition at 0 , 30 , and 60 of glenohumeral abduction. Data were analyzed using the paired Student t test or Wilcoxon signed rank test, depending on the results of normality testing. Results: The irreparable SS tear resulted in significantly lower functional abduction force at 30 of abduction (P ¼ .01) and a trend toward a decrease (P ¼ .17) at 60 compared with the intact configuration. SCR shoulders produced greater functional force at 0 compared with the tear configuration (P ¼ .046). Humeral head migration was significantly increased by 4.4 and 3.0 mm at 0 and 30 of abduction, respectively, when comparing the intact vs. SS tear configurations (P ¼ .001). SCR decreased superior migration down to levels of intact shoulders at 0 and 30 of abduction (P ¼ .008 and P ¼ .013, respectively) and was not significantly different from the intact configuration at any angle. SCR decreased passive shoulder extension compared with the tear configuration and increased abduction compared with the intact configuration (P ¼ .007 and P ¼ .03, respectively). The overall arc of axial rotation was not significantly different between SCR and the intact configuration at any angle. Conclusions: In the setting of an irreparable SS tear, SCR restores key biomechanical parameters of the shoulder to intact levels. SCR should be considered for qualifying patients with irreparable RCTs.
Background: Newborn infants are highly vulnerable to oxidative stress. Following birth asphyxia, oxidative injury due to ischemia–reperfusion can result in significant brain and heart damage, leading to death or long-term disability. Study Question: The study objective was to evaluate the effectiveness of antioxidant gamma-l-glutamyl-l-cysteine (γGlu-Cys) in inhibiting oxidative injury to cultured embryonic cardiomyocytes (H9c2 cells). Study Design: Control and γGlu-Cys–treated (0.5 mM) H9c2 cells were incubated under 6-hour ischemic conditions followed by 2-hour simulated reperfusion. Measures and Outcomes: To quantify oxidative stress-induced apoptosis sustained by cardiomyocytes, lactate dehydrogenase (LDH) release and the presence of cytosolic cytochrome c were measured, as well as the number of secondary lysosomes visualized under electron microscopy. Results: Compared to controls, H9c2 cells coincubated with γGlu-Cys during ischemia–reperfusion exhibited a significant reduction in both LDH release into the incubation medium [23.88 ± 4.08 (SE) vs. 9.95 ± 1.86% of total; P = 0.02] and the number of secondary lysosomes [0.070 ± 0.009 (SD) vs. 0.043 ± 0.004 per μm2; P = 0.01]. Inhibition of LDH release with γGlu-Cys was the same (P = 0.67) as that of a caspase inhibitor. The significant increase in cytosolic cytochrome c (P = 0.01) after ischemia–reperfusion simulation further supports γGlu-Cys's role in apoptosis prevention. Conclusions: It is concluded that the glutathione precursor γGlu-Cys protects cultured embryonic cardiomyocytes from apoptosis-associated oxidative injury.
Background: Degenerative and traumatic changes to the rotator cuff can result in massive and irreparable rotator cuff tears (RCTs). Purpose/Hypothesis: The study objective was to conduct a biomechanical comparison between a small, incomplete RCT and a large, complete RCT. We hypothesized that the incomplete supraspinatus (SS) tear would lead to an incremental loss of abduction force and preserve vertical position of the humeral head, while a complete SS tear would cause superior humeral migration, decrease functional deltoid abduction force, and increase passive range of motion (ROM). Study Design: Controlled laboratory study. Methods: Six cadaveric shoulders were evaluated using a custom testing apparatus. Each shoulder was subjected to 3 conditions: (1) intact/control, (2) 50%, full-thickness, incomplete SS tear, and (3) 100%, complete SS tear. Deltoid abduction force, superior humeral head migration, and passive ROM were measured in static conditions at 0°, 30°, and 60° of glenohumeral abduction, respectively. Results: The intact SS resulted in a mean deltoid abduction force of 2.5, 3.3, and 3.8 N at 0°, 30°, and 60° of abduction, respectively. Compared with the intact shoulder, there was no significant difference in mean abduction force seen in the incomplete tear, while the force was significantly decreased by 52% at 30° of abduction in the complete tear ( P = .009). Compared with the incomplete tear, there were significant decreases in abduction force seen in the complete tear, by 33% and 48% (0.9 N and 1.1 N) at 0° and 30° of abduction, respectively ( P = .04 and .004). The intact configuration experienced a mean superior humeral head migration of 1.5, 1.4, and 1.1 mm at 0°, 30°, and 60° of abduction, respectively. The complete tear resulted in a superior migration of 3.0 and 4.4 mm greater than the intact configuration at 0° and 30° of abduction, respectively ( P = .001). There was a 5° and 10° increase in abduction ROM with 50% and 100% tears, respectively ( P = .003 and .03). Conclusion: An incomplete SS tear does not significantly alter the biomechanics of the shoulder, while a large, complete SS tear leads to a significant superior humeral migration, a decreased deltoid abduction force, and a mild increase in passive ROM. Clinical Relevance: Our findings demonstrate the effects of large SS tears on key biomechanical parameters, as they progress from partial tears.
Background: Previous studies have aimed to biomechanically improve the transosseous tunnel technique of rotator cuff repair. However, no previous work has addressed tunnel inclination at the time of surgery as an influence on the strength of the repair construct. Hypothesis: We hypothesized that the tunnel angle and entry point would influence the biomechanical strength of the transosseous tunnel in rotator cuff repair. Additionally, we investigated how tunnel length and bone quality affect the strength of the repair construct. Study Design: Controlled laboratory study. Methods: Mechanical testing was performed on 10 cadaveric humeri. Variations in the bone tunnel angle were imposed in the supraspinatus footprint to create lateral tunnels with inclinations of 30°, 45°, and 90° relative to the longitudinal axis of the humeral shaft. A closed loop of suture was passed through the bone tunnel, and cyclic loading was applied until failure of the construct. Load to failure and distance between entry points were the dependent variables. Analysis of variance, post hoc paired t tests, and the Bonferroni correction were used to analyze the relationship between the tunnel angle and failure load. The Pearson correlation coefficient was then used to evaluate the correlation of the distance between entry points to the ultimate failure load, and t tests were used to compare failure loads between healthy and osteoporotic bone. Results: Tunnels drilled perpendicularly to the longitudinal axis (90°) achieved the highest mean failure load (167.51 ± 48.35 N). However, there were no significant differences in the failure load among the 3 tested inclinations. Tunnels drilled perpendicularly to the longitudinal axis (90°) measured 13.86 ± 1.35 mm between entry points and were significantly longer ( P = .03) than the tunnels drilled at 30° and 45°. We found no correlation of the distance between entry points and the ultimate failure load. Within the scope of this study, we could not identify a significant effect of bone quality on failure load. Conclusion: The tunnel angle does not influence the strength of the bone-suture interface in the transosseous rotator cuff repair construct. Clinical Relevance: The transosseous technique has gained popularity in recent years, given its arthroscopic use. These findings suggest that surgeons should not focus on the tunnel angle as they seek to maximize repair strength.
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