Flexor Tendon Repair Techniques: Core Suture Techniques : Wheeless' Textbook of Orthopaedics

- See: discussion flexor tendon repair: theory and modes of failure

- Discussion:
    - Kessler Repair:
- Kessler grasping stitch or similar core suture methods of flexor tendon repair are popular types of flexor tendon repair;
            - references:
                    - Complications After Flexor Tendon Repair: a Systematic Review and Meta-Analysis
                    - Influence of core suture geometry on tendon deformation and gap formation in porcine flexor tendons.
                    - Influence of core suture material and peripheral repair technique on the strength of Kessler flexor tendon repair.
                    - [Tendon repair w/ strengthened Kessler, modified Kessler, and Savage suture techniques: a biomechanical comparison].
                    - History and Evolution of the Kessler Repair
                    - Comparison of 1- and 2-Knot, 4-Strand, Double-Modified Kessler Tendon Repairs in a Porcine Model

    - Tajima Modification:
- in which suture knots are tied w/ in repair site, is convenient since sutures are placed in tendon ends & ends are then used to
                    pass tendon through flexor tendon sheath and run into position for repair w/o need to further damage tendon by
                    instrumentation;
- 4 strand cruciate repair:
- technique:
- a small 2 mm slit is made on the side of the tedon, 1 cm from the tendon edge;
- suture needle is inserted into the side of the tendon (thru the slit), 1 cm from the severed tendon edge, and is passed
                              longitudinally out of the tendon edge;
- needle is passed into corresponding severed tendon edge and is passed longitudinally 1 cm out of the side of the tendon;
- suture is then reinserted a few mm distal to its exit point (no locking), and is directed in a cross-wise fashion to exit in
                              middle of tendon laceration site;
- suture is reintroduced into the opposite tendon segment and continues across in crossing direction, and is brought out on
                              opposite tendon side (1 cm from the laceration site);
- suture is introduced a few mm distal (no locking) and is directed longitudinally across the laceration site;
- suture is then passed back crossing the middle of the laceration site to exit next to the free tendon edge;
- make sure the slack is removed with each pass of the suture;
- because the core suture is non-locking, additional tightening is possible before the knot is tied;
- after the knot is tied, it is buring inside of the slit;
- outcomes:
- McLarney E, et al (1999), this repair technique was faster than the other major repair techniques and was significantly
                             stronger than other 4 strand core suture techniques (including the MGH criss crossing locking stitch);
                    - Biomechanical analysis of the cruciate four-strand flexor tendon repair
    - Running Locking Stitch:
- consider placing the lock-running suture along the back half of the tendon, prior to placing the core suture;
            - this facilitates the "no touch" technique of tendon repair;
- after the core suture has been placed, the running-lock stitch can be completed;
            - references:
   - Complications After Flexor Tendon Repair: A Systematic Review and Meta-Analysis
                   - Biomechanical Comparison of Krackow Locking Stitch Versus Nonlocking Loop Stitch With Varying Number of Throws

                   - The Effect of the Epitendinous Suture on Gliding in a Cadaveric Model of Zone II Flexor Tendon Repair
    - Augmented Becker Technique / MGH / Savage:
- in the study by Singer, et al (1998), the core suture technique was the most important element in establishing both strength and
                      stiffness of the repair;
- the Becker technique involves 4 strand repair with two knots out side of the repair site;
- repair consists of criss-crossing running suture using a double armed needle;
- sutures should be placed 0.75 cm from the cut edge of the tendon;
- volar epitenon suture is used to augment the repair;
- as noted in the report by Howard et al (1997), the MGH tendon repair technique (crossing running suture repair) was
                    signficantly more resistant to gap formation than the Bunnel or the Krackow technique;
- MGH tendon repair has superior suture purchase which is probably related to superior resistance to gap formation;
- as noted by Stein T, et al (1998), there were no increases in dorsal versus volar grasping strength with the Beck Technique
                    (where as dorsally placed sutures were found to be stronger with the Kessler technique);
- hence sutures can be placed on the volar tendon surface without disrupting the dorsal blood supply;
            - The effect of suture technique on adhesion formation after flexor tendon repair for partial lacerations in a canine model.
            - Use of Taguchi method for biomechanical comparison of flexor-tendon-repair techniques to allow immediate active flexion..
            - Biomechanical analysis of four strand extensor tendon repair techniques
            - A randomized biomechanical study of zone II human flexor tendon repairs analyzed in an in vitro model

- Misc Considerations:
    - Bury the Knot:
- which ever technique is used, a knot should never be left on the outer surface of the flexor tendon;
- to bury knot, use a knife to make a small longitudinal slit in the flexor tendon and bring the suture arms out through this slit;
- the knot is then thrown, and it will remain buried underneath the tendon surface;
   - tenofix device
            - ref: Device for Zone-II Flexor Tendon Repair. A Multicenter, Randomized, Blinded, Clinical Trial.
    - tensioning the repair:
            - Effects of Tension Across the Tendon Repair Site on Tendon Gap and Ultimate Strength