Suture retrievers and suture shuttles are indispensable instruments for arthroscopic suture stitching, and various instrument designs are available, including straight and different degrees of angulation in any direction for optimal handling of each specific task. Although the utility of these tools is indisputable, surgeries can require that large numbers of stitches be pierced through small areas of tendon, making smooth stitching itself difficult. In such cases, there is concern regarding possible tendon damage. Many different suturing techniques are available for tendon repair. Rawson et al. described factors affecting repair success and highlight evolution and improvements in techniques and also how suture repairs might contribute to their own trauma .
Based on our clinical experience and impressions, we hypothesized that needle-shaped suture shuttles would require lower forces to pierce tendons and cause less tendon damage than suture retrievers. We were able to confirm this hypothesis in part. Combining all suture retrievers and shuttles, we found that lower forces were required to pierce a tendon when using a suture shuttle instead of a suture retriever. Unexpectedly, the overall lowest penetration forces were achieved using straight suture retrievers, though it must be noted that no truly straight suture shuttle was available. Among the angled instruments, however, suture shuttles required less penetration force and produced smaller tendon defects than retrievers. In addition, these angled suture shuttles showed the smallest lesion size (3 mm2), even smaller than the lesions from straight suture retrievers (5.1 mm2). Surprisingly, the instrument diameter does not seem to alter the required force.
To our knowledge, this is the first study systematically analyzing this topic. Chokshi et al. used different arthroscopic devices for suture passing and repair of the rotator cuff and tested these repairs to failure . They conclude that larger holes created in the rotator cuff may compromise the integrity of the repair . In 2003, Cummins and Murrell reported that the weak point of reconstruction is the tendon-suture interface rather than sutures, knots, or anchors in open rotator cuff repairs . It has been shown experimentally that the highest pull out strength for sutures from the rotator cuff lies medial to the rotator cable , even though the tissue may also fail at that location, referred to as “medial cuff failure” [4, 5]. Explanatory factors such as potential overtensioning, and the effect of the braided suture materials on their passage through the rotator cuff, as well as holes created for reconstruction have been considered . The last factor is our main interest in this study as often the tendon is pierced repeatedly until the ideal position for the suture is found. Intrasubstance tendon failures following successful suturing may be due to the considerably large holes created during stitching that contribute to weakening and tearing of the tendon. We are not aware of any in vivo studies that evaluate lesions made intraoperatively during repair using suture Retrievers and/or shuttles and the effect on the healing outcome of the repaired tendon.
We are aware of several limitations to this study: The number of suture retrievers and suture shuttles on the market is large and, unfortunately, not all manufacturers who were invited to provide instruments for testing participated. Furthermore, we addressed only instruments designed for either shuttling or retrieving of sutures. Other instruments, which allow for grasping tissue and needle passing the free end of the suture in one step, were not included. In addition, this biomechanical setup can, in the best case, only approximate the forces that occur intraoperatively during arthroscopic surgery, as soft-tissue tension, bony landmarks, and tissue behavior can only be partially reproduced in the laboratory setting. While the use of wax plates has the advantage of being highly standardized, it does not allow us to differentiate between cutting and merely displacing the pierced tissue, which may be mechanically important and will be addressed in future experiments. The displacement of the material also explains the larger diameter of the perforation marks in comparison to the size of the holes in the sieve while still avoiding contact. Nevertheless, this displacement also occurs in vivo as the instruments are applied.
Even though on average suture shuttles appeared to be more reliable for penetrating a tendon, it should be noted that retrievers can potentially reduce the number of operative steps, as they can also be used to manipulate sutures, are mechanically robust, can grasp and unload sutures inside the joint, and are equally useful for braided or monofilamentous suture materials. However, these advantages must be weighed against their potentially damaging effect on the tendon tissue, an effect that may be even larger when the tendon is not pierced perpendicularly to the tendon surface. More complex loading geometries will be considered and addressed in future biomechanical trials.