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Background: Lines of action of the superior, middle, and inferior infraspinatus muscle fibers work together to produce moment arms that change throughout abduction in an intact shoulder, after a supraspinatus tear, and after superior capsular reconstruction (SCR) and reverse total shoulder arthroplasty (rTSA). Purpose: To use moment arm values to indicate the efficacy of SCR and rTSA to restore infraspinatus function during shoulder abduction. Study Design: Descriptive laboratory study. Methods: A total of 5 human cadaveric shoulders placed in a testing apparatus were each actively abducted (0°-90°) under the following 4 conditions: intact, complete supraspinatus tear, SCR, and rTSA. The 3-dimensional coordinates of points were tracked along the origin and insertion of the superior, middle, and inferior infraspinatus fibers during abduction. Moment arm values were calculated using the origin-insertion method to determine abduction contribution of infraspinatus fiber sections. Analysis of variance and post hoc Tukey testing were used to compare differences in moment arms between the 4 conditions and between fiber sections. Results: In the intact condition, the superior infraspinatus fibers had an abduction moment that decreased with elevation until shifting to adduction. Conversely, the middle and inferior fibers had an adduction moment that turned to abduction (mean moment arm values from 0° to 90°: inferior, from -5.9 to 19.4 mm; middle, from -4.7 to 15.9 mm; superior, from 5.6 to -5.1 mm; P < .05). After a supraspinatus tear, superior fibers lacked any torque, and inferior and middle fibers lost adduction potential (inferior, from 4.8 to 14.0 mm; middle, from -0.2 to 9.6 mm; superior, from 1.0 to 0.7 mm; P < .05). SCR restored the initial superior fiber abduction moment (5.6 mm at 0°; P < .05); middle and inferior fibers had some restoration but were weaker than intact fibers. Loss of abduction moment in all fibers was seen with rTSA (inferior, from -9.6 to -1.6 mm; middle, from -10.5 to -3.6 mm; superior, from -1.7 to -4.6 mm; P < .05). Conclusion: Infraspinatus fiber groups had different and inverse moment arms during scapular plane elevation. SCR most closely resembled the intact shoulder, whereas rTSA transformed the infraspinatus into an adductor. Clinical Relevance: These results support the efficacy of SCR at restoring biomechanical muscle function and suggest that the changes in moment arms for each fiber group be considered when choosing treatment modalities and rehabilitation protocols after rotator cuff tear.

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BACKGROUND AND HYPOTHESIS: Rotator cuff tears have a wide variability in presentation, with some causing pain and reduced function but others remaining completely asymptomatic. Sleep disturbances are a primary driver for patients with rotator cuff tears to see a physician, and one of the main goals of rotator cuff repair (RCR) surgery is to restore normal sleep patterns in these patients. The primary purpose of this study aimed to determine the percentage of patients undergoing RCR who report preoperative sleep disturbances. Second, this study sought to identify at what postoperative follow-up intervals patients stopped reporting sleep disturbances and how the percentages change over time. It was hypothesized that the majority of patients undergoing arthroscopic RCR would report preoperative and initial postoperative sleep disturbances and that 75% of patients would report resolution of sleep disturbances by 1 year postoperatively. METHODS: A total of 326 patients undergoing primary arthroscopic RCR were prospectively enrolled in this study. Validated patient-reported outcome measures were obtained preoperatively and postoperatively, including the visual analog pain scale score, American Shoulder and Elbow Surgeons score, Single Assessment Numeric Evaluation score, Simple Shoulder Test (SST) score, and Veterans RAND 12-Item Health Survey physical and mental component scores. RESULTS: According to question 2 of the SST, 291 patients (89%) reported preoperative sleep disturbances. Within the cohort of patients who reported resolution of sleep disturbances, 46% reported resolution by 3 months postoperatively; an additional 31%, by 6 months; a further 14%, by 12 months; and the final 8%, by 24 months. Age ≥ 65 years was significantly associated with increased reporting of resolution compared with age < 65 years. All patient-reported outcome measures, including the visual analog pain scale score, American Shoulder and Elbow Surgeons score, Single Assessment Numeric Evaluation score, SST score, and Veterans RAND 12-Item Health Survey (physical component) score, showed statistically significant improvements after surgery. CONCLUSIONS: Eighty-nine percent of patients reported preoperative sleep disturbances. Seventy-seven percent of patients reported resolution of sleep disturbances by 6 months postoperatively, and 81% of patients reported resolution of sleep disturbances by 2 years postoperatively.

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PURPOSE: The rotator cuff (RC) muscles contribute to dynamic stability and rotational actions of the glenohumeral joint. Moment arm can be used to demonstrate the potential work a muscle contributes to a musculoskeletal joint rotation. This study aimed to understand the moment arm contributions of the RC muscles and explore changes following a complete supraspinatus tear treated with either superior capsular reconstruction (SCR) or reverse total shoulder arthroplasty (rTSA). METHODS: Five fresh-frozen cadaveric specimens were prepared and mounted in an apparatus where each intact RC muscle was held in tension with a line of action toward its origin on the scapula. Mean moment arms for each muscle were determined experimentally based on Optotrak data collected during cadaveric shoulder arm abduction. RESULTS: Using ANOVA testing, our analysis demonstrated significant differences (p < 0.001) in infraspinatus and teres minor moment arms after rTSA compared to the intact shoulder model. After SCR, significant differences (p < 0.001) were seen in teres minor, with these differences being statistically similar to the changes seen in teres minor after rTSA. Subscapularis showed no significant difference in moment arm values between the models (p = 0.148). CONCLUSION: Our results illustrate that mean moment arms were preserved in the RC muscles after complete supraspinatus tear. This study also shows evidence that subscapularis function may be maintained after SCR or rTSA. After SCR, infraspinatus may maintain similar abduction ability compared to the anatomical shoulder, while teres minor ability may increase. Infraspinatus may have decreased abduction ability after rTSA while teres minor may have increased ability.

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BACKGROUND: Patients undergoing total joint arthroplasty (TJA) have an increased likelihood of having an abnormal coagulation profile compared with the general population. Coagulation abnormalities are often screened for before surgery and considered during perioperative planning. This study assesses a preoperative abnormal coagulation profile as a risk factor for postoperative complications after total hip arthroplasty (THA), revision THA (rTHA), total knee arthroplasty (TKA), and revision TKA (rTKA) and then examines specific coagulopathies to determine their influence on complication rates. METHODS: Patients who underwent THA, rTHA, TKA, or rTKA from 2011 to 2017 were identified in the American College of Surgeons National Surgical Quality Improvement Program database and then assessed for preoperative abnormal coagulation profiles. Various postoperative complications were analyzed for each cohort, and two separate multivariate regression analyses were used to assess the relationship between abnormal coagulation and postoperative complications. RESULTS: 403,566 THA, rTHA, TKA, or rTKA cases were identified, and 40,466 (10.0%) of patients were found to have an abnormal coagulation profile. Patients with preoperative coagulation abnormalities had higher likelihoods of postoperative complications after primary TJA than in revision TJA. An international normalized ratio>1.2 was associated with the most types of postoperative complications, followed by a bleeding disorder diagnosis. A partial thromboplastin time>35 seconds was associated with only one type of postoperative complication, while a platelet count <150,000 per µL was associated with postoperative complications only after TKA. CONCLUSION: TJA in patients with abnormal coagulation profiles may result in adverse outcomes. These patients may benefit from preoperative intervention. Prophylactic care needs to be personalized to the specific coagulation abnormalities present.

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