2019 ISAKOS Biennial Congress Paper #153
Tensioning of the Superior Capsule Reconstruction Graft Improves Shoulder Function Biomechanically
Felix Dyrna, MD, Münster GERMANY
Knut Beitzel, Prof. Dr., Cologne GERMANY
Florian B. Imhoff, MD, Priv.-Doz., Zurich SWITZERLAND
Bastian Scheiderer, MD, Munich, Bavaria GERMANY
Andreas B. Imhoff, MD, Prof. Emeritus, Sauerlach / Munich, Bavaria GERMANY
Augustus D. Mazzocca, MS, MD, Waltham, MA UNITED STATES
University of Connecticut Health Center, Farmigton, CT, UNITED STATES
FDA Status Not Applicable
The superior capsule reconstruction shows significant better results when the graft is fixed under tension compared to a non-tensioned graft simulating a spacer.
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.
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).
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).
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.