Extensor Tendon Repair 

The extensor tendons of the hand are in a relatively superficial position; thus, they are highly susceptible to injury from lacerations, bites, burns, or blunt trauma. Extensor tendon injuries are commonly diagnosed in the emergency department (ED). Certain injuries can be repaired in the ED^[1] , others should be repaired by a hand surgeon.

The dorsum of the hand, wrist, and forearm are divided into 8 anatomic zones to facilitate classification and treatment of extensor tendon injuries.^{[2, 3]} See the image below.

• Zone 1 (distal interphalangeal [DIP] joint)
• Zone 2 (middle phalanx)
• Zone 3 (proximal interphalangeal [PIP] joint)
• Zone 4 (proximal phalanx)
• Zone 5 (metacarpophalangeal [MCP] joint)
• Zone 6 (dorsum of hand)
• Zone 7 (wrist)
• Zone 8 (dorsal forearm)

Extensor tendon injuries may require operative intervention, depending on the complexity of the injury and the zone of the hand involved.^[4] For treatment of injuries to specific zones of the hand, see the Technique section. The goal of repair is to restore tendon continuity and function. Optimal preparation and technique is critical to minimize adhesions and scar tissue formation and to ensure the best possible outcome.

Indications for extensor tendon repair include the following:

• Tendon laceration greater than 50%
• Tendon laceration less than 50% with significantly decreased strength compared with contralateral finger
• Tendon laceration associated with significant overlying skin loss, joint space penetration, or bony fracture

Repair can be accomplished immediately in the emergency department or after a delay of up to 7 days following the injury.^[5] If repair is delayed, irrigate and debride the wound, approximate the skin loosely with interrupted sutures, and place the hand in a volar splint.^[6]

Extensor tendon repair should not be attempted in the emergency department or acute care setting in any of the following circumstances. In these cases, the repair should be performed by an experienced hand surgeon, preferably in the operating room.

• Skilled physician unavailable
• Contaminated injury, particularly open zone 5 "fight bite" injury
• Presence of bony fracture, open joint space, or significant overlying skin loss (requires an orthopedist or hand surgeon for repair)

• Adequate anesthesia is required for thorough wound exploration and tendon manipulation.
• Use lidocaine 1% or bupivacaine 0.25% without epinephrine (see Local Anesthetic Agents, Infiltrative Administration).
• Use local or digital nerve block for finger injury (see Hand, Anesthesia: Blocks).
• Use field or regional nerve block for hand injury (see Local Anesthesia and Regional Nerve Block Anesthesia).

Anesthesia

• Povidone iodine solution (eg, Betadine)
• Syringe, 10 mL
• Needle, 25 or 27 gauge
• Local anesthetic solution

See the image below.

Wound irrigation and preparation

• Sterile normal saline (0.9% NaCl) solution, 500 mL
• Irrigation set
• Syringe, 60 mL
• Angiocatheter, 16 gauge
• Intravenous tubing
• Face shield
• Blood pressure cuff
• Bright overhead lighting

See the image below.

Tendon and skin repair

• Sterile gloves
• Sterile drapes
• Gauze pads, 4 X 4
• Needle holder
• Skin hooks, 2
• Retractors
• Sharp and blunt-nosed scissors
• Small hemostats, several
• Single-toothed forceps
• Nonabsorbable, synthetic, and braided suture (4-0, 5-0, and 6-0)
• Nylon suture (4-0 or 5-0) for skin repair (Avoid silk suture [high tissue reactivity] and chromic suture [dissolves before the tendon adequately heals])

Wound care and splint

• Topical antibiotic ointment
• Gauze pads
• Elastic gauze bandage or tape
• Splint material
• Shears to cut aluminum splint

See the image below.

• Place patient supine on a procedure table or a gurney with an attached armboard.
• Make sure the patient is in a comfortable position to limit movement during the procedure.
• Place the patient’s hand level with his or her body or heart.

Preparation

• Explain the procedure, risks, and benefits to the patient and obtain informed consent.
• Place the patient in the appropriate position with bright overhead lighting.
• Administer anesthesia as described above.
• To control blood flow, elevate the affected limb for approximately 1 minute to allow blood flow to drain by gravity.
• Place either a digital tourniquet or a blood pressure cuff on the mid to upper arm and inflate to 50-100 mm Hg above the systolic pressure.
• For comfort, several layers of cast padding may be applied under the tourniquet or blood pressure cuff.
• Once inflated, wrap the cuff with rolled gauze. Tape the gauze to prevent it from unraveling off the inflated cuff.
• Use a hemostat to clamp the cuff tubes to avoid a slow leak from the inflated cuff.
• A blood pressure cuff tourniquet is well tolerated for approximately 20 minutes and should never exceed 2 hours.
• Once blood flow is controlled, débride the wound and liberally irrigate with 500-1000 mL of normal saline.
• Once irrigation is complete, the wound is considered sterile.
• Apply sterile drapes to create a sterile field and prepare the necessary instruments and suture material at the bedside.

Management

• Always handle tendons delicately.
• Avoid crushing forces or excessive punctures with forceps and needles.
• Only use forceps on the exposed, cut end of the tendon whenever possible.
• Always consult an orthopedist or hand surgeon for complex injuries.

Patterns of injury

See the image below.

• Zone 1 (distal interphalangeal [DIP] joint) and zone 2 (middle phalanx)

  • Open
    • Dermatotenodesis
    • Mallet finger splint/Kirschner-wire (K-wire) fixation (See the video below.)
      Video clip of splint application.
  • Closed
    • Type 1 (no avulsion) and 2 (small avulsion) - Mallet finger splint
    • Type 3 (intra-articular avulsion fracture with dorsal displacement) - Orthopedic or hand surgeon performs operative repair
• Zone 3 (proximal interphalangeal [PIP] joint)

  • The central tendon is most commonly injured^[6]
  • Open - Orthopedic or hand surgeon performs operative repair
  • Closed - Dorsal boutonnière splint
• Zone 4 (proximal phalanx)

  • Open
    • Modified Kessler or modified Bunnell using 5-0 nonabsorbable suture
    • Splint/K-wire fixation
    • Volar splint for 3-6 weeks
• Zone 5 (metacarpophalangeal [MCP] joint)

  • Open "fight bite"
    • Radiograph the injury, explore and irrigate, administer antibiotics, cover wounds with bulky dressing, apply a volar splint
    • Orthopedist or hand surgeon performs delayed closure
  • Closed - Splint MCP joint in neutral position (vs operative repair)
• Zone 6 (dorsum of hand)

  • Most superficial region of hand
  • Modified Bunnell using 4-0 nonabsorbable suture
  • Volar splint
• Zone 7 (wrist) and zone 8 (dorsal forearm)

  • Uncommon
  • Often involves the extensor retinaculum and is at risk for developing adhesions after repair^[6]
  • An orthopedist or hand surgeon performs operative repair

Suture techniques

• Modified Kessler stitch (See the image below.)Suture techniques.

  • Place a single suture into the cut end core of the tendon, entering about one third of the diameter of the tendon. Weave the suture through the lateral tendon margin.
  • Wrap the suture around the tendon and re-enter on the dorsal radial side of the tendon perpendicularly and 1-2 mm closer to the tendon end.
  • Pull the suture through the tendon to exit on the ulnar side.
  • Wrap the suture along the tendon and enter the dorsal aspect of the ulnar half of the tendon.
  • Thread the needle through the length of the tendon and exit at the cut end of the tendon in alignment with the original insertion site.
  • Repeat the same stitch on the opposing cut half of the tendon, entering ipsilateral.
  • Once complete, the 2 free ends of the suture are on the same side of the tendon.
  • Apply delicate tension to the sutures and gently approximate the 2 tendon ends together.
  • Tie the suture ends with a square knot that remains buried between the tendon ends.
• Modified Bunnell stitch (See the image below.)Suture techniques.

  • Place a single suture into the cut end core of the tendon, entering about one third of the diameter of the tendon. Pass the needle diagonally through the tendon, exiting on the ulnar side.
  • Wrap the suture around the tendon and re-enter on the dorsal ulnar side of the tendon.
  • Pull the suture directly through the tendon to exit on the dorsal radial side of the tendon.
  • Re-enter the radial side of the tendon. Pass the needle diagonally through the tendon, crossing the initial stitch, to exit on the ulnar side of the tendon in alignment with the original insertion site.
  • Repeat the same stitch on the opposing cut half of the tendon, entering ipsilateral.
  • Once complete, the 2 free ends of the suture are on the same side of the tendon.
  • Apply delicate tension to the sutures and gently approximate the 2 tendon ends together.
  • Tie the suture ends with a square knot that remains buried between the tendon ends.
• Dermatotenodesis (See the image below.)Dermatotenodesis.

  • Place a single suture into the lateral distal end of the cut skin, and include a bite from the proximal skin wound.
  • Anchor the suture with a knot, leaving enough material to complete the stitch.
  • Enter the skin medial to the knot and pull the suture through 1 mm from the knot.
  • Place a stitch through the distal skin so that the needle passes through the dorsal side of the tendon.
  • Bring the needle through to exit the dorsal side of the proximal tendon, incorporating the dorsal skin.
  • Repeat the same stitch so that the needle exits the proximal half.
  • Place a single suture into the medial distal end of the cut skin, and include a bite from the proximal skin wound.
  • Pull the suture to approximate skin edges.
  • Place the last suture to anchor to the knot.
• For more information on suturing, see eMedicine Dermatology article Suturing Techniques.

Splinting techniques

• Dorsal splint for zone 1 injury (mallet finger splint) (See the images below.)Mallet finger splint. Mallet finger splint.

  • Measure and cut an aluminum, foam-backed splint so that the splint sits just distal to the PIP joint and ends at the distal tip of the nail.
  • Place the splint on the finger, keeping the DIP joint in slight hyperextension.
  • Avoid over-hyperextension at the DIP joint, which may cause skin sloughing.
  • Tape the splint to the finger.
  • The DIP is held in slight extension for no less than 6 weeks.
• Dorsal splint for zone 3 injury (boutonnière splint) (See the images below.)Boutonnière splint. Boutonnière splint.

  • Measure and cut an aluminum, foam-backed splint so that the splint lies just distal to the MCP joint and ends just proximal to the DIP joint.
  • Place the splint on the finger, keeping the MCP joint in full extension.
  • Tape the splint to the finger.

• Obtain a thorough history and perform a complete physical examination.
• Assume all dorsal wrist, hand, and digit lacerations have an underlying tendon injury until proven otherwise.
• Obtain a radiograph of the injury when a fracture or foreign body is suspected.
• Be familiar with the anatomy of the region.^[7]
• Provide a well-lit and optimally prepared surgical field.
• Handle all tissue delicately to avoid adhesion and scar tissue formation.
• Consult a specialist whenever possible.
• Consider prophylactic antibiotics.
• Never close a contaminated wound.
• All patients should be referred to a rehabilitation program following repair. Early mobilization is associated with improved outcomes.^[8]

• General complications include infection and tendon rupture.
• Zone 7 and 8 complications include the following:

  • Multiple tendon lacerations
  • Risk of adhesions following tendon repair that decrease wrist mobility and impair finger movement^[9]
  • Decreased wrist mobility
  • Retraction from the initial site of injury
• Zone 6 complications include retraction from the initial site of injury (less likely than zones 7 and 8) and excess shortening of the tendon following repair.
• Zone 5 complications include infection (injury often secondary to human bite) and subluxation of the extensor digitorum communis.
• Zone 4 complications include damage to the gliding layer located between the tendon and bone.
• Zone 3 complications include boutonnière deformity.
• Zone 1 and 2 complications include mallet deformity, swan-neck deformity, and skin ulceration secondary to splint.^{[5, 10]}