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Tensioning of the Superior Capsule Reconstruction Graft Improves Shoulder Function Biomechanically


Felix Dyrna, MD
GERMANY

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Tensioning of the Superior Capsule Reconstruction Graft Improves Shoulder Function Biomechanically

Felix Dyrna, MD, GERMANY Knut Beitzel, Prof. Dr., GERMANY Florian B. Imhoff, MD, Priv.-Doz., SWITZERLAND Bastian Scheiderer, MD, GERMANY Andreas B. Imhoff, MD, Prof. Emeritus, GERMANY Augustus D. Mazzocca, MS, MD, UNITED STATES

University of Connecticut Health Center, Farmigton, CT, UNITED STATES

2019 Congress   Paper Abstract   2019 Congress   Not yet rated

 

Anatomic Location

Shoulder Glenohumeral

Anatomic Structure

Muscle Tendon

Diagnosis / Condition

Osteoarthritis Impingement Tears

Sports Medicine

Biomechanics

Treatment / Technique

Implant Repair / Reconstruction

Tendon

Supraespinoatus Tendon Injury

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Summary: The superior capsule reconstruction shows significant better results when the graft is fixed under tension compared to a non-tensioned graft simulating a spacer.

Purpose

Biomechanically it has been shown that the superior capsule represents an important static stabilizer against superior head migration in the glenohumeral joint and its reconstruction improves humeral head centration. A remaining open question is the amount of graft tension needed for the superior capsule reconstruction (SCR) to perform best. Purpose of the study therefore was to investigate how does graft tension influence shoulder function on a dynamic abduction motion. It was hypothesized that proper graft tension is needed and would ensure a better performance biomechanically than a non-tensioned graft interposition.

Methods

Ten fresh-frozen cadaveric shoulders were utilized. The anterior, middle, and posterior deltoid tendons and rotator cuff tendons were attached to individual shoulder simulator actuators. Deltoid pulleys were spread over the lateral edge of the acromion according to the native force vectors. Cuff pulleys were loaded in the direction of the musculotendinous unit. Optical tracking tripods on the lateral distal humerus (moving) and the lateral acromion (fixed) tracked 3D motion during dynamic testing. Mean values for maximum glenohumeral abduction and deltoid forces were recorded among 4 conditions: (1) intact shoulder, (2) simulated irreparable supraspinatus (SSP) tear, (3) superior capsule reconstruction using a commercially available 3-mm thick acellular dermal allograft put into place without further tensioning it (0-5N graft tension) simulating a spacer, and (4) superior capsule reconstruction using the same graft but pre-tensioning and fixing it with 30-35(N).

Results

Intact shoulders required 193.2 N¬ ± 45.1 total deltoid force to achieve 79.8° ± 5.8 maximum glenohumeral abduction. Compared to native shoulders, abduction decreased following SSP tears (27.5%, to an average of 54.3° ± 13.7 p=0.04), cuff, while total deltoid forces increased by (23.4%, to an average of 252.1 N ± 68.3 p=0.04). The non-tensioned SCR did not improve shoulder function (abd. 54.1° ± 16.1) or acquired deltoid force (277.8 N ± 39.8) compared to the SSP tear status. However, a tensioned SCR reconstruction improved shoulder function reaching an average abduction angle of 65.1° ± 12.5. Therefore, displaying a significant improvement compared to the SSP tear (p=0.04) but still remain reduced compared to the native state (p=0.01), without reducing combined deltoid force 282.3N ± 47.9).

Conclusion

The superior capsule reconstruction shows significant better results when the graft is fixed under tension compared to a non-tensioned graft simulating a spacer. Therefore, correct graft measurement and adequate tension, at least 30 N, are important aspect for the surgical procedure.