- 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:
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Gliding characteristics and gap formation for locking and grasping tendon repairs: a biomechanical study in a human cadaver model.
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Adhesion formation after flexor tendon repair: a histologic and biomechanical comparison of 2- and 4-strand repairs in a chicken model.
-
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
Haralambos T. et al (JHS-Am May 2000 Volume 25 Number 3) 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 the presence of a gap of 3 mm or greater in a repaired tendon indicates that the tendon may have been loaded
past its ultimate 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
- hence a tendon with a 3-mm gap is at increased risk of complete rupture compared with a tendon with a gap less than 1 mm;
- ref:
The resistance of a 4 and 8 strand technique to gap formation during tensile testing: an study of repaired flexor tendons after 10 days of in vivo healing.
-
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;
-
dorsal or volar suture placement:
- some authors argue that core sutures should grasp the volar half of the tendon inorder to minimize interruption of tendon blood flow (see
blood supply);
- as noted by Soejima et al (JHS Vol 24 Jul 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 vs palmar placement of core suture for flexor tendon repairs. J of Hand Surg. Vol 20-A. 1995. p 801-807;
-
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,
inaddition to the running epitenon stitch;
- in the report by
HT Dinopoulos et al 2000, the authors note 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 the 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 MI Boyer 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;"
- ref:
Intrasynovial Flexor Tendon Repair. An Experimental Study Comparing Low and High Levels of in Vivo
Force During Rehabilitation in Canines. Martin I. Boyer, MD. JBJS (Am) 83:891-899 (2001)
Biomechanical and clinical evaluation of the epitenon-first technique of flexor tendon repair.
Flexor tendon repair using a "six strand" method of repair and early active mobilisation..
Effect of suture knot location on tensile strength after flexor tendon repair.
Year Book: Double Loop Locking Suture: A Technique of Tendon Repair for Early Active Mobilization. Part I: Evolution of Technique and Experimental Study.
Lee-H. J Hand Surg. 1990. 15-A. pp 945-952.
Year Book: Double Loop Locking Suture: A Technique of Tendon Repair for Early Active Mobilization. Part II: Clinical Experience.
Lee-H. J Hand Surg. 10. 15-A. pp 953-958.
Two, Four, and Six Strand Zone II Flexor Tendon Repairs: An in situ Biomechanical comparison using Cadaver Model.
RT Thurman MD. J. Hand Surg. 1998. Vol 23-A. No 2. March. p 261.
Use of the Taguchi method for biomechanical comparison of flexor tendon repair techniques to allow immediate active flexion; A new method of analyis and optimization of technique to improve the quality of the repair.
G. Singer MD et al. JBJS Vol 80-A. No 10. Oct 1998. p 1498.
Effect of peripheral suture depth on strength of tendon repairs. Diao, E. et al. J. Hand Surg. Vol 21-A. 1996. p 234-239.
Biomechanical analysis of four strand extensor tendon repair techniques. RF Howard et al. J. Hand Surg. Vol 22-A. 1997. p 838-842.
A randomized biomechanical study of zone II human flexor tendon repairs analyzed in an in vitro model. J. Hand Surg. Vol 23-A. 1998. p 1046-1051.
Effect of the cross sectional area of locking loops in flexor tendon repair. H. Hatanaka and PR Manske. J. Hand Surgery. Vol 24-A. No 4. July 1999.
The effects of multiple-strand suture methods on the strength and excursion of repaired intrasynovial flexor tendons: a biomechanical study in dogs.
Winters SC, Gelberman RH, Woo SL-Y, Chan SS, Grewal R, Seiler JG III. J Hand Surg 1998;23A:97-104.
Biomechanical properties of four circumferential flexor tendon suture techniques
Core Suture Purchase Affects Strength of Tendon Repairs.
Influence of Core Suture Purchase Length on Strength of Four-Strand Tendon Repairs.
