It’s Not the Knot
It’s Not the Knot
Abstract & Commentary
Synopsis: Arthroscopic rotator cuff repair with mattress sutures and standard bone anchors worked reasonably well with no added holding strength provided by using a modified Mason-Allen stitch. Concerns remain that holding strength would still be inferior to transosseous tunnels with a standard open technique.
Source: Schneeberger AG, et al. Mechanical strength of arthroscopic rotator cuff repair techniques. J Bone Joint Surg Am. 2002;84-A(12):2152-2160.
Rotator cuff repairs have traditionally been performed with open techniques using transosseous tunnels or suture anchors. A modified Mason-Allen suture has been shown to provide optimal holding ability through the cuff. Arthroscopic techniques are gaining popularity as instrumentation improves given the decreased morbidity and perioperative pain. Schneeberger and colleagues compared various anchors and suture techniques for arthroscopic cuff repair to see if there were any advantages in holding ability of the tendon.
Schneeberger et al used right and left matched human cadaveric shoulders to test 5 different bone anchors: the Revo screw (Linvatec, Largo, Fl), Mitek Rotator Cuff anchor (Mitek Products, Ethicon, Westwood, Mass), the 5.0-mm Statak anchor (Zimmer, Warsaw, Ind), the PANALOK RC absorbable anchor (Mitek), and the 5.0-mm Bio-Statak anchor (Zimmer). These were inserted using arthroscopic instruments and tested under cyclic loading to failure. In addition, 5 different types of arthroscopic suture passing instruments were tested for their ability to pass mattress sutures as well as a modified Mason-Allen stitch arthroscopically. These suture passers included the standard Caspari 4-mm slotted jaw suture punch (Linvotec), the mini-straight Caspari suture punch system (Arthrotek, Warsaw, Ind), the ArthroSew (Surgical Dynamics, Norwalk, Conn), the Acufex Suture Punch (Smith & Nephew, Andover, Mass), and the modification of the slotted jaw Caspari Suture Punch with a longer 8-mm needle. Lastly, the holding ability of the tendon was assessed after these various anchors were placed with mattress or Mason-Allen sutures.
There was no significant difference among any of the 5 anchors tested for pull-out strength under cyclic loading. A common finding was that the sutures tended to break for the metal anchors at the eyelet, which tended to have sharp edges. This was not a problem for the absorbable anchors, which tended to have smooth eyelets. The mode of failure was fairly evenly distributed between rupture of suture and anchor pull-out. There was a tendency for the PANALOK RC anchor to have slightly more displacement upon cyclic loading initially, which is in keeping with the different anchoring mechanism to tip and engage the undersurface of the cortical bone. None of the commercially available suture passing devices were suitable for placing a modified Mason-Allen stitch arthroscopically. The standard Caspari Punch needle was too short, and the ArthroSew and Acufex device had needles that were too short or too weak to pass through the tendon. The mini-straight Caspari Suture Punch did retrieve the suture effectively but always damaged it in the process. Only the modified Caspari Punch with an 8-mm long needle could successfully pass the suture through the tendon in a Mason-Allen configuration. More importantly, Schneeberger et al found that the mattress suture was actually better than the modified Mason-Allen suture in combination with an anchor. There was more displacement and a lower load to failure with the Mason-Allen sutures. They theorized that because the sutures with an anchor system are designed to slide until the knot is tight, this can be done less well with a locking stitch compared to a mattress stitch, which would share the tension equally as the knot is tensioned. Schneeberger et al conclude that the holding strength of all of these available anchors is satisfactory in conjunction with a standard mattress stitch.
Comment by David R. Diduch, MS, MD
Arthroscopic rotator cuff repair is coming. It is only a matter of time. I feel this is analogous to ACL reconstructions 10-15 years ago when it was rare for the general orthopaedic surgeon to attempt these until instrumentation advanced to the point where reproducibly good results could be achieved by people generally familiar with arthroscopy. Eventually, techniques and instrumentation will advance to the point that arthroscopic cuff repair is commonplace. However, it is not there yet. This paper highlights several major issues with the existing technology.
Firstly, all of the suture passing devices had major problems. They either could not pass the suture through the tissue, damaged it, could not retrieve it, or basically were too flimsy or too short. Only a custom modification of the Caspari Punch with a much longer needle worked. This is a very expensive device that requires quite a large cannular for passing. Newer suture passing devices are evolving, which will surely replace these first-generation devices in due time.
It was interesting to note that there were no major advantages among the anchors. Absorbable anchors cut the suture less frequently at the eyelets than metal anchors. It was a bit reassuring to find that the mattress sutures worked equally if not better than the Mason-Allen suture when placed arthroscopically. This is a relief because it is hard enough to pass a mattress suture arthroscopically, let alone trying to pass Mason-Allen sutures. In fact, a lot of arthroscopic repairs are done with just simple sutures for basic reasons of simplicity. It would be interesting for Schneeberger et al to have studied this in comparison. It would also have been interesting to study the new knotless cuff devices, as they indeed work with a different mechanism.
Schneeberger et al somewhat unfairly state in their conclusion that the arthroscopic techniques for holding ability at roughly 230N are inferior to open techniques with transosseous tunnels at greater than 300N. The modes of failure for each were suture breakage, and they’re comparing #3 sutures to #2 sutures and using historical data in the literature. A direct experimental comparison would be more worthwhile, as well as studying other issues such as micromotion of the tendon on the bony surface and, of course, clinical healing.
Dr. Diduch is Associate Professor, Department of Orthopaedic Surgery, University of Virginia School of Medicine, Charlottesville, VA.
Arthroscopic rotator cuff repair with mattress sutures and standard bone anchors worked reasonably well with no added holding strength provided by using a modified Mason-Allen stitch. Concerns remain that holding strength would still be inferior to transosseous tunnels with a standard open technique.Subscribe Now for Access
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