Biomechanische Aspekte der Rotatorenmanschettennaht: Einfluss von Nahtmaterial, Knotentechnik und Nahttechnik auf die Primärstabilität

Abstract

BackgroundThe treatment of Rotator cuff (RC) tears has made significant chances in the last decades. Due to arthroscopic procedures new material and technologies have been developed. Up to now, attention was focused mainly on the development of material with higher mechanical strength, stronger suture material, or improving of suturing and knotting. The present study focusses on all different aspects together which influence the biomechanical stability of rotator cuff tear reconstructions. Materials and MethodsDiverse kinds of suture anchors (different designs and materials) and transosseous sutures were tested biomechanically in human humeral specimen. Arthroscopic sliding and nonsliding-nodes were tested with conventional (Ethibond and PDS) and new UHMWPE sutures for biomechanical features. Additionally we tested three arthroscopic suture techniques (single-, matress-, arthroscopic Mason Allen- stitch) with above mentioned materials in human RC tendons. All tests were performed under cyclic loading on the Zwick universal Testing machine. The maximum failure rate, the clinical failure rate at 3 mm irreversible expension and the failure mechanism were evaluated. ResultsBetween the different suture anchors were found significantly differences only in healthy human humeral specimen. In osteoporotic bone all different suture anchors were comparable with failure values less than 200N. Subcortical fixed suture anchors tend to have a higher stability than in cancellous bone fixed suture anchors. Transosseos sutures showed no benefits in osteoporotic bone. With up to 300N the UHMWPE sutures had a significantly higher strength than Ethibond / PDS sutures. Though, depending on the node type, even UHMWPE sutures showed a relevant elongation at values between 100-200N. The lowest biomechanical strength showed the tendon-suture construct. Even though the Mason Allen stitch with UHMWPE sutures showed the highest stability (>200N) clinical failure appeared at about 100N. The weakest link in the failure of RC repair seems to be the suture-tendon interface. Even when using UHMWPE sutures and a biomechanical stable suture technique clinical failure was observed at approx. 100N. ConclusionsThese results suggest that the development of suture anchors with rising diameter seems to be irrelevant. Rather, the technical development should focus on small anchors with a subcortical fixation and therefore better biomechanical stability. Especially in revision cases this seems to be relevant. Post-operative treatment should be moderate because clinical failure can appear from only 100N of load. Level of evidenceLevel IV.