Modified Kessler-Tajima Suture Technique for Flexor Tendon Repair

INTRODUCTION TO FLEXOR TENDON REPAIR

The primary goal of flexor tendon repair is to restore the structural integrity of the severed tendon while maintaining a smooth gliding surface to prevent adhesion formation. The evolution of core suture techniques has been driven by the need to balance tensile strength—sufficient to withstand early active motion (EAM) protocols—with minimal disruption to tendon vascularity and gliding mechanics.

The Modified Kessler-Tajima Suture, popularized and refined by Strickland in 1983, represents a critical advancement in operative hand surgery. By amalgamating the grasping characteristics of the traditional Kessler technique with the parallel strand and buried-knot principles of the Tajima technique, this modification offers superior biomechanical stability. A defining advantage of this technique is the use of separate suture strands for each tendon stump. This allows the surgeon to utilize the free ends of the suture as traction sutures, facilitating the atraumatic passage of the swollen tendon ends through the tight fibro-osseous flexor sheath prior to tying the final knot.

SURGICAL ANATOMY AND BIOMECHANICS

A profound understanding of flexor tendon anatomy and the biomechanical principles of suture repair is mandatory for the operating surgeon.

Flexor Tendon Vascularity

Flexor tendons receive their blood supply through two primary mechanisms:
1. Intrinsic Vascularity: Supplied via the longitudinal vessels entering through the vincula (vincula brevia and vincula longa) on the dorsal aspect of the tendon.
2. Extrinsic Nutrition: Synovial diffusion within the flexor sheath, which is critical in Zone II ("No Man's Land").

Surgical Warning: The core suture must be strictly maintained within the volar third of the tendon. Placing sutures dorsally risks strangulating the intrinsic longitudinal blood supply derived from the vincular system, potentially leading to focal tendon necrosis, impaired intrinsic healing, and catastrophic secondary rupture.

Biomechanics of the Modified Kessler-Tajima

The strength of a flexor tendon repair is proportional to the number of core suture strands crossing the repair site, the caliber of the suture, and the locking mechanism of the loops.
* Locking vs. Grasping: The Modified Kessler-Tajima utilizes a locked configuration. When tension is applied, the locked loop tightens around the tendon fascicles, significantly increasing the resistance to gap formation compared to simple grasping loops.
* Gap Resistance: Gap formation greater than 2 to 3 mm at the repair site is the precursor to repair failure. It disrupts the healing callus, increases gliding resistance, and precipitates rupture. The locked loops of this technique, combined with a robust epitendinous repair, maximize gap resistance.
* Buried Knots: By tying the knots within the tendon interface (between the cut ends), the external surface of the tendon remains smooth. This minimizes friction against the annular pulleys (specifically A2 and A4) and reduces the stimulus for extrinsic adhesion formation.

INDICATIONS AND PREOPERATIVE PLANNING

Indications

• Acute lacerations of the flexor digitorum profundus (FDP) and flexor digitorum superficialis (FDS), particularly in Zones I, II, and III.
• Delayed primary repairs (within 10 to 14 days post-injury) before irreversible myostatic contracture occurs.
• Tendon lacerations requiring passage through intact pulley systems, where the traction suture technique is highly advantageous.

Preoperative Preparation

• Anesthesia: Regional anesthesia (axillary or supraclavicular brachial plexus block) is preferred. Wide-awake local anesthesia no tourniquet (WALANT) is increasingly utilized, allowing intraoperative active movement testing to assess repair integrity and gap formation.
• Tourniquet: If WALANT is not used, a well-padded pneumatic arm tourniquet is applied and inflated to 250 mm Hg (or 100 mm Hg above systolic pressure).
• Instrumentation: Basic hand tray, fine skin hooks, Ragnell retractors, tenotomy scissors, and a pediatric feeding tube or specialized tendon retriever.
• Suture Selection:
  • Core Suture: 3-0 or 4-0 braided synthetic (e.g., Ticron, FiberWire, or Supramid) or monofilament (e.g., Prolene) on a non-cutting, taper-point needle.
  • Epitendinous Suture: 5-0 or 6-0 monofilament nylon or Prolene on a fine taper needle.

SURGICAL TECHNIQUE: STEP-BY-STEP EXECUTION

The following details the precise execution of the Modified Kessler-Tajima technique, expanding upon Strickland’s 1983 principles.

1. Exposure and Tendon Retrieval

• Extend the traumatic laceration using a Bruner (zigzag) or mid-lateral incision to provide adequate exposure of the flexor sheath.
• Open the flexor sheath via a cruciate or L-shaped incision, meticulously preserving the critical A2 and A4 pulleys to prevent postoperative bowstringing.
• Retrieve the proximal tendon stump. If it has retracted into the palm, use a flexible catheter or tendon retriever. Pass the catheter from distal to proximal through the intact pulleys, suture the tendon to the catheter, and gently pull it distally.
• Secure the proximal tendon temporarily with a transversely placed 25-gauge hypodermic needle through the tendon and adjacent cruciform pulley or sheath to relieve tension during the repair.

2. Core Suture Placement (The Modified Kessler-Tajima)

The hallmark of this technique is the use of separate sutures for each tendon end, allowing the strands to act as traction devices.

• Initial Introduction: Use separate sutures introduced into each tendon end. Begin with the proximal stump.
• Volar Placement: Introduce the needle into the cut surface of the tendon. It is imperative to stay along the volar third of the tendon to protect the dorsal blood supply. Advance the needle longitudinally and exit the volar surface 5 to 10 mm from the cut edge. Note: A 10 mm purchase is biomechanically optimal for preventing suture pull-out.
• First Locking Loop: Grasp approximately 25% of the diameter of the tendon with the transverse passage of the needle. To create the lock, pass the needle superficial to the longitudinal strand before pulling it through. Lock the suture on the side of the tendon with a secure knot.
• Transverse Passage: Pass the suture transversely behind this locked knot, across the dorsal aspect of the volar third of the tendon, and exit onto the opposite lateral tendon surface.
• Second Locking Loop: Lock the suture again on this side, ensuring the loop grasps another 25% of the tendon diameter.
• Return to Cut Surface: Pass the suture into the tendon behind the second knot, directing it longitudinally to exit on the cut surface, directly opposite the initial entry point.
• Repeat on Distal Stump: Using a separate piece of suture, repeat this exact process on the opposite side of the cut tendon (the distal stump). Ensure the suture repair is maintained strictly on the volar third of the cut surface, locking the suture with each exit.

Clinical Pearl: At this stage, you have two free suture ends exiting the cut surface of the proximal stump, and two free ends exiting the cut surface of the distal stump. If the proximal stump needs to be threaded through the A2 or A4 pulley, these strong core sutures can be used to pull the tendon through the sheath atraumatically, avoiding crushing forceps injuries to the epitenon.

3. Approximating and Tying the Core Suture

• Once both tendon ends are appropriately routed through the pulley system and meet without excessive tension, pair the corresponding suture strands from the proximal and distal stumps.
• Tie the knots securely. Because the sutures exit the cut surfaces, the knots will be inherently tied within the tendon interface (buried knots).
• Ensure the tendon ends are snugly approximated without bunching or buckling. A slight bunching may occur but should be minimized to prevent catching on the pulleys.

4. The Epitendinous Repair

The core suture provides the primary tensile strength, but the epitendinous repair is critical for smoothing the repair site and adding significant biomechanical stability.

• Complete the repair with a circumferential running 5-0 or 6-0 nylon or Prolene suture.
• Purchase approximately 1 to 2 mm of the epitenon on each side of the laceration.
• The goal is to invert the tendon ends slightly, burying any exposed collagen fibrils. This smooths the surface, drastically reducing gliding resistance and minimizing the risk of extrinsic adhesions.
• Biomechanical Note: A well-executed epitendinous suture increases the overall strength of the repair by 10% to 50% and is highly effective at preventing gap formation during early active motion.

Pitfall: Do not take excessively deep bites with the epitendinous suture. Deep bites can tether the core suture, cause bunching of the tendon, and increase the cross-sectional area of the repair, leading to triggering or impingement within the flexor sheath.

POSTOPERATIVE REHABILITATION PROTOCOLS

The success of a Modified Kessler-Tajima repair relies heavily on the postoperative rehabilitation protocol. The locked, 2-strand core combined with an epitendinous repair is generally strong enough to withstand Early Active Motion (EAM), provided the patient is compliant.

Phase I: Acute Phase (Weeks 0–4)

• Immobilization: The hand is placed in a dorsal blocking splint (DBS). The wrist is positioned at 20° to 30° of flexion, metacarpophalangeal (MCP) joints at 50° to 70° of flexion, and interphalangeal (IP) joints in full extension.
• Motion Protocols:
  • Modified Duran Protocol: Passive flexion and active extension within the constraints of the DBS.
  • Early Active Motion (EAM): If the repair is deemed robust (e.g., WALANT confirmed), place-and-hold exercises or true active flexion to half-fist may be initiated under strict hand therapist supervision to promote intrinsic healing and tendon gliding.

Phase II: Intermediate Phase (Weeks 4–6)

• The dorsal blocking splint is gradually discontinued or modified to a neutral wrist position.
• Active composite fist exercises are initiated.
• Tendon gliding exercises (hook fist, straight fist, composite fist) are emphasized to achieve differential glide between the FDS and FDP.

Phase III: Strengthening Phase (Weeks 6–12)

• Discontinue all splinting by week 6.
• Begin progressive resistance exercises (e.g., putty, hand grippers).
• Return to heavy manual labor or contact sports is typically restricted until 10 to 12 weeks postoperatively, as the tendon continues to remodel and gain ultimate tensile strength.

COMPLICATIONS AND MANAGEMENT

Even with meticulous surgical technique, flexor tendon repairs are fraught with potential complications.

1. Tendon Rupture

Rupture typically occurs between days 7 and 21, during the inflammatory and early fibroblastic phases of healing when the tendon is at its weakest. It is usually the result of patient non-compliance, accidental loading, or gap formation leading to repair failure.
* Management: Requires prompt surgical re-exploration. If identified within a few days, a primary re-repair may be attempted. Delayed presentations may necessitate a two-stage tendon reconstruction using a silicone Hunter rod.

2. Adhesion Formation

The most common complication, resulting in a discrepancy between passive and active range of motion.
* Prevention: Meticulous handling of the tendon (no-touch technique), preservation of the flexor sheath, a smooth epitendinous repair, and strict adherence to EAM protocols.
* Management: Intensive hand therapy. If conservative measures fail after 3 to 6 months of plateaued progress, a surgical tenolysis may be indicated.

3. Bowstringing

Occurs due to the failure or iatrogenic destruction of the critical A2 or A4 pulleys. This results in a loss of mechanical advantage, decreased active flexion, and a visible volar displacement of the tendon during flexion.
* Management: Requires surgical pulley reconstruction using extensor retinaculum or free tendon grafts (e.g., palmaris longus).

CONCLUSION

The Modified Kessler-Tajima suture remains a foundational technique in the armamentarium of the hand surgeon. By utilizing separate strands for traction, locking the core loops to prevent pull-out, burying the knots to reduce friction, and supplementing the construct with a meticulous epitendinous repair, surgeons can achieve a biomechanically robust repair. This construct reliably withstands the rigors of early active motion protocols, ultimately optimizing functional outcomes and minimizing the dual threats of rupture and adhesion formation.