Does a Critical Rotator Cuff Tear Stage Exist? A Biomechanical Study of Rotator Cuff Tear Progression in Human Cadaver Shoulders
ABSTRACT It is unknown at which stage of rotator cuff tear the biomechanical environment is altered. The purpose of this study was to determine if a critical rotator cuff tear stage exists that alters glenohumeral joint biomechanics throughout the rotational range of shoulder motion, and to evaluate the biomechanical effect of parascapular muscle-loading.
Eight cadaver shoulders were used with a custom testing system. Four progressive rotator cuff tear stages were investigated on the basis of footprint anatomy. Three muscle-loading conditions were examined: rotator cuff only; rotator cuff with deltoid muscle; and rotator cuff, deltoid, pectoralis major, and latissimus dorsi muscles. Testing was performed in the scapular plane with 0°, 30°, and 60° of shoulder abduction. The maximum internal and external rotations were measured with 3.4 Nm of torque. The position of the humeral head apex with respect to the glenoid was calculated with use of a MicroScribe 3DLX digitizing system throughout the rotational range of motion. The abduction capability was determined as the abduction angle achieved with increasing deltoid load.
Tear of the entire supraspinatus tendon significantly increased maximum external rotation and significantly decreased abduction capability with higher deltoid loads (p < 0.05). Tear of the entire supraspinatus tendon and half of the infraspinatus tendon significantly shifted the humeral head apex posteriorly at the midrange of rotation and superiorly at maximum internal rotation (p < 0.05). Loading the pectoralis major and latissimus dorsi muscles decreased the amount of humeral head elevation due to deltoid loading.
Tear of the entire supraspinatus tendon was the critical stage for increasing rotational range of shoulder motion and for decreased abduction capability. Further tear progression to the infraspinatus muscle was the critical stage for significant changes in humeral head kinematics. The pectoralis major and latissimus dorsi muscles played an important role in stabilizing the humeral head as the rotator cuff tear progressed.
Article: Management of Rotator Cuff Tears.[Show abstract] [Hide abstract]
ABSTRACT: Every year approximately 18 million Americans report shoulder pain, a large percentage of which are a result of rotator cuff disease. Rotator cuff tear progression can be difficult to predict. Factors associated with tear enlargement include increasing symptoms, advanced age, involvement of 2 or more tendons, and rotator cable lesion. Nonsurgical treatment can be effective for patients with full-thickness tears. When conservative treatment fails, surgical repair provides a reliable treatment alternative. Recurrent tears after surgery can compromise outcomes, particularly for younger patients with physically demanding occupations. Revision surgery provides satisfactory results for those with symptomatic re-tears. If the tear is deemed irreparable, addressing concomitant biceps pathology or performing partial repairs can reliably improve pain and potentially reverse pseudoparalysis. The reverse shoulder arthroplasty has limited indications in the setting of rotator cuff tears and should be reserved for patients with painful pseudoparalysis and associated arthropathy. Copyright © 2014 American Society for Surgery of the Hand. Published by Elsevier Inc. All rights reserved.The Journal Of Hand Surgery 12/2014; DOI:10.1016/j.jhsa.2014.06.122 · 1.66 Impact Factor
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ABSTRACT: The morphology of the supraspinatus tendon may affect tear propagation. It was hypothesized that tears located in the anterior third of the supraspinatus tendon would propagate more readily and would require lower loads to reach critical amounts of tear propagation than those located in the middle third of the supraspinatus tendon. Twenty-three fresh-frozen human cadaveric shoulders were tested under increasing levels of cyclic loading. Tears were created in the anterior third (Group A, n = 10) or the middle third (Group M, n = 13) of the supraspinatus tendon. The maximum load at which a critical tear retraction was reached and the tear area for the final loading set were compared between groups. A correlation analysis was also performed for age compared with maximum load. No significant differences were found between the anterior-third tear group (Group A) and the middle-third tear group (Group M) in maximum load (p = 0.09) or tear area (p = 0.6). However, Group A first reached a 100% increase in tear size at a significantly lower load than Group M (p = 0.03). Strong negative correlations were detected between age and maximum load in Group A (τ = -0.82) and Group M (r = -0.63). Other factors being equal, tears in the anterior supraspinatus tendon may propagate more readily than tears in the tendon's middle part. Age may be a factor for tear propagation. Older patients and patients with tears in the anterior supraspinatus should be followed especially carefully. Copyright © 2015 by The Journal of Bone and Joint Surgery, Incorporated.The Journal of Bone and Joint Surgery 02/2015; 97(4):273-8. DOI:10.2106/JBJS.N.00062 · 4.31 Impact Factor
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ABSTRACT: The purpose of this study was to characterize the biomechanical effects of the lower trapezius transfer and to compare it with the latissimus dorsi transfer in a cadaveric model of a massive posterosuperior rotator cuff tear. Eight cadaveric shoulders were tested at 0°, 30°, and 60° of shoulder abduction. Range of motion, humeral rotational position due to muscle loading, joint reaction forces, and kinematics were measured. All specimens were tested in 4 conditions: intact, massive posterosuperior cuff tear, lower trapezius transfer, and latissimus dorsi transfer. A repeated-measures analysis of variance was used for statistical analysis. Internal rotation due to muscle loading increased with massive cuff tear compared with the intact condition (P < .05). The latissimus transfer corrected this change at 0° abduction, whereas the trapezius transfer corrected this at all abduction angles. The massive cuff tear decreased glenohumeral joint compression forces at all abduction angles; these forces were restored by the lower trapezius transfer (P < .05). At maximum humeral internal rotation and 0° of abduction, the humeral head apex shifted superiorly and laterally with massive cuff tear (P < .05); this shift was more closely restored to intact values by the trapezius transfer compared with the latissimus transfer (P < .05). The lower trapezius transfer is superior to the latissimus transfer at restoring native glenohumeral kinematics and joint reaction forces in our cadaveric model. It may be a promising treatment option for patients with a massive irreparable rotator cuff tear. Copyright © 2015 Journal of Shoulder and Elbow Surgery Board of Trustees. Published by Elsevier Inc. All rights reserved.Journal of shoulder and elbow surgery / American Shoulder and Elbow Surgeons ... [et al.] 04/2015; DOI:10.1016/j.jse.2015.02.008 · 2.37 Impact Factor