Double Opposing Locking Loop Tendon Repair: A New Take on An Old Technique

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INTRODUCTION In the quest for the perfect tendon repair, dozens if not hundreds of flexor tendon repairs have been published since the first primary repair was described by Bunnell in 1918.1 Adding the variability of suture material and postoperative protocols has made it even more difficult to identify a clear superior method. In this search, repairs have been evaluated through various testing protocols with outcomes of interest including maximum strength, 2 mm gap strength, and glide resistance. As a result, certain tendon repair techniques have become mainstream and widely accepted internationally, such as the modified Kessler. Not all techniques have gained this level of popularity. First described in 1990 in a 2-part article by Dr Lee, the Double Loop Locking Suture technique was designed as a stronger alternative to the Kessler technique.2 Dr Lee demonstrated both in the experimental and clinical setting encouraging data supporting the superiority of this technique.3 Biomechanical investigation has demonstrated the tensile strength of the Double Loop Locking Suture method is significantly higher than the modified Kessler despite both being 4-strand repairs, although it did not surpass the strength of the modified Pennington.4 Furthermore, a case series demonstrated successful early mobilization of tendons repaired with the double loop locking suture repair.5 At the Buncke Clinic, we have used a slight modification of this technique almost exclusively for the past 3 decades with good results. We call it the double opposing locking loop, or DOLL suture. As compared with the original, our modification simplifies the execution of the locked suture. Dr Lee had described taking a full-thickness bite of the tendon transversely and returning the suture by means of 2 small bites before passing through the loop and locking it. We opted to reduce this to 2 full-thickness tendon bites with slightly divergent axes before passing the suture through the loop. The difference can be appreciated in (Fig. 1).FIGURE 1: Diagram of the modified double opposing locking loop flexor tendon repair we utilize (top) as compared with the original technique described by Dr Lee (bottom).Here, we demonstrate this technique using a cadaveric specimen of the upper extremity. Our study was evaluated by our Institutional Review Board and determined to fall outside the scope of human research, therefore not requiring review. Technique The patient is placed supine with the upper extremity in supination on a hand table. A tourniquet is used to maintain a blood-free field. Exposure will usually depend on the mechanism of injury and the location of the skin laceration with respect to the tendon laceration. Often, the skin laceration will need to be extended to ensure proper access to the tendon laceration. In such cases, a Bruner incision can provide good access while reducing the risk of joint contracture. Exposure of the tendon is done is standard manner; the tendon sheath is exposed whereas the adipocutaneous flaps are retracted, taking care not to injure the neurovascular bundles. The proximal and distal ends of the tendons are carefully retrieved using a tendon retriever or fine mosquito hemostat, and temporarily transfixed with a 25G needle to allow for repair. In cases where the tendon ends have retracted beyond reach, they can be accessed through a separate more proximal incision just proximal to the A1 pulley or incisions in between annular pulleys. This allows placement of the sutures in the tendon ends and subsequent delivery of the sutures and tendons through the tendon sheath to the tenorrhaphy site. Passing a red rubber catheter through the tendon sheath and suctioning the suture ends through its lumen can aid with this atraumatic delivery. In cases where the tendon ends are frayed it may be necessary to resect some of the injured tendon to facilitate even tendon ends that can be well-approximated. Care must be taken to avoid over-resection, as excessive shortening can result in an abnormal finger cascade and/or quadriga effect. The DOLL repair uses 4 separate looped sutures. We commonly use 4-0 looped Supramid (S. Jackson, Inc.). The first pass is taken perpendicular to the axis of the tendon at minimum 5 mm from the end of the tendon, but more commonly 7 to 8 mm from the tendon end. Taking the pass more distant than 8 mm will result in excessive shortening of the tendon upon repair and should be avoided. The return pass is also taken perpendicular to the axis of the tendon, but slightly divergent on cross-section than the first pass. This ensures that some tendon fibers are captured between these 2 passes, ensuring a strong lock (Fig. 2A). The needle is threaded through the loop and cinched tight (Fig. 2B–D). The suture is then passed through the core of the tendon (Fig. 2E,F). A second suture is used in a similar manner, but with the needle entering from the side opposite to the first suture (Fig. 3A–C). This will result in 4 core strands. The process is repeated in the corresponding tendon end. One operator throws the first part of a surgeon’s knot and keeps the tendon ends in close apposition whereas the other operator completes their knots (Fig. 3D). The assistant then completes their knots (Fig. 3E). The tenorrhaphy site initially looks a little bunched, but this will settle under normal tension of the flexors (Fig. 3F). See Supplemental Video 1, Supplemental Digital Content 1, https://links.lww.com/TIO/A85 for a demonstration of the technique. Skin closure is done in the usual manner with 4-0 Nylon. We typically opt for non-resorbable sutures as we use an early active motion protocol and the non-resorbable sutures tend to be sturdier under the circumstances.FIGURE 2: Locking of the first suture using a 4-0 Supramid, dyed green for photographic visibility. A, Suture is passed from one side of the tendon to the other and then back to the original side (B) needle passing through the looped end of suture (C) final loop locking loop configuration before tightening (D) tightening of the suture with assistance of forceps (E) passing through the core of the tendon (F) completion of first suture.FIGURE 3: Locking of the second suture using a 4-0 Supramid, dyed red for photographic visibility. A, loop is initially passed through staring on the opposite side from the first suture and then back and then back to the original side, like the first suture (green) (B) locking of the suture (C) both proximal sutures passed through the tendon core. D, Although assistant holds the tendon well-approximated, surgeon creates 1 surgeon’s knot followed by 5 throws on the contralateral side (green). E, the process is repeated with the other 2 core sutures (red) (G) the resulting 4-strand repair (F) suture is trimmed with a 2 mm tail.Initially, the hand should be splinted with the MCPs in a flexed position to reduce the tension on the repair. We generally begin early mobilization under the careful supervision of our certified hand therapists at approximately day 5 postoperatively. The added strength of the DOLL repair allows for early mobilization protocols. Expected Outcomes The DOLL repair provides several advantages, which we hypothesize lead to its increased strength as compared with other commonly used repairs. Two-stranded Kessler repairs continue to be frequently used; however, multi-stranded techniques have been shown to add additional strength to repairs. Furthermore, although additional core suture material in the form of added strands increases bulk, it does not have a detrimental effect on gliding or adhesion formation.1 Therefore, the use of a multi-strand technique, such as the 4-stranded DOLL is preferable. The locking nature of the sutures prevents suture pull-out and minimizes gap formation. By using separate sutures in the proximal and distal tendon stumps, these sutures can be placed in advance during replantation part preparation and similarly wound exploration, tying

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