Tendon Repair Techniques : Wheeless' Textbook of Orthopaedics

- Discussion:
- core suture techniques;
- strength of flexor tendon repair is proportional to the number of sutures crossing the repair;
- note that a average force of 20 N required for active digital flexion in humans and most tendon repair techniques need initial
           strength of more than 40 N;
- modes of failure:
- gliding resistance:
- references:
- Gliding and gap formation for locking and grasping tendon repairs: a biomechanical study in a human cadaver model.
- Adhesions after flexor tendon repair: a histologic and biomechanical comparison of 2-4-strand repairs in a chickens
- ultimate tensile strength: (see ultimate tensile strength)
- gap formation:
- is a leading cause of adhesions in immobilized tendon repairs, and therefore suture technique is critical for optimal healing;
- in the report by Dinopoulos HT, et al (2000) the authors noted that a 8-strand repair since repetitive loading in vivo may
                            lead to gap formation at lower force levels than those measured during load-to-failure testing;
                  - if the gap size exceeds a critical size (1-3 mm for the conditions of our study) then the initial advantages of the 8-strand
                            repair are lost and its mechanical performance is not significantly better than that of the 4-strand repair;
                  - second implication is that presence of a gap of 3 mm or greater in a repaired tendon indicates that tendon may havebeen
                            loaded past its failure point and can now only sustain a fraction of the force level it could sustain before gapping;
                  - magnitude of force sustained with a 3-mm gap was only 30 to 40 N for the 2 repair techniques investigated
                  - tendon with a 3-mm gap is at increased risk of complete rupture compared with a tendon with a gap less than 1 mm;
- references:
                         - The resistance of a four- and eight-strand suture technique to gap formation during tensile testing: an experimental study of repaired canine flexor tendons after 10 days of in vivo healing.
                         - The Effect of Suture Preloading on the Force to Failure and Gap Formation After Flexor Tendon Repair
    - types of suture:
- traditionally, we have used braided synthetic polyester material (Ethibond), usually of a 3-0 or 4-0 caliber;
- as noted by Singer MD, et al. (1998), 3-0 Mersilene suture or prolene suture may be suture of choice;
- authors note that braided suture may generate more friction and may deform the tendon more than monofilament suture;
            - PDS may cause excessive inflammation;
                   - Taguchi method for biomechanical comparison of flexor-tendon-repair techniques to allow immediate active flexion.
                   - Effect of absorbable polydioxanone flexor tendon repair and restricted active mobilization in a canine model
                   - Aggressive mobilization following zone II flexor tendon repair using a two-strand heavy-gauge locking loop technique
                   - A Evaluation of Zone II Flexor Tendon Repair Using a Knotless Barbed Suture Versus a Traditional Braided Suture
    - dorsal or volar suture placement:
- ? whether core sutures should grasp the volar half of the tendon in order to minimize interruption of tendon blood
                      flow (see blood supply);
- as noted by Soejima, et al (1999), there was superior pull out strength when core sutures were placed in the dorsal half of the
                      tendon (over 50% difference);
- ref: Comparative mechanical analysis of dorsal versus palmar placement of core suture for flexor tendon repairs.
    - number of sutures crossing the repair site:
- classic core suture techniques including the Kessler and the Tajima had only 2 suture arms spanning the repair site;
- recently it has become clear that the strength of the repair is most related to the number of suture arms crossing the repair;
- disadvantages of multistrand repairs:
- complexity of these repairs which can lead to uneven tendon repair.
- increased work of flexion due to operative manipulation and bulk at the repair site;
- to minimize the risk of tendon re-rupture at the repair site, the surgeon should attempt to place 4-6 sutures across the repair
                     site, in addition to the running epitenon stitch;
- Dinopoulos HT, et al (2000): that there is high incidence of gap formation at the repair site following tendon repair;
- they studied the resistance of a 4- and an 8-strand suture technique to gap formation during tensile testing'
- 22 canine flexor tendons were transected, repaired, and tested to failure after 10 days of in vivo healing;
- they found that 8-strand repairs sustained 80% higher force at a gap of 1 mm than the 4-strand repairs (average force, 70
                                vs 39 N), but the force sustained at a gap of 3 mm did not differ between groups (35 N for both groups);
- they conclude that the 8-strand repair is significantly more resistant to initial gapping during ex vivo tensile testing than
                                4-strand repair but that the two repairs are equally susceptible to rupture if a gap of 3 mm or greater forms;
            - in report by Boyer MI et al, the authors found that "suture repair technique had a highly significant effect on tensile properties,
   with tendons in 8-strand group having increased ultimate force (p < 0.001) and rigidity (p = 0.009) and decreased strain
                         at 20 N (p < 0.001) compared w/ tendons in the four-strand group"
- refs
                          Intrasynovial flexor tendon repair. study comparing low and high levels of in vivo force during rehab in canines.
                          The resistance of a four- and eight-strand suture technique to gap formation during tensile testing: an experimental study of repaired canine flexor tendons after 10 days of in vivo healing.