Extensor Tendon Repair 

The extensor tendons of the hand are in a relatively superficial position; consequently, 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] whereas others should be repaired by a hand surgeon at a later time in an operating room (OR).

The dorsum of the hand, wrist, and forearm are divided into nine anatomic zones to facilitate classification and treatment of extensor tendon injuries. Odd numbers are used for regions overlying articular structures, with even numbers being assigned to the regions between joints, as follows (see the image below)[2, 3, 4] :

• 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 (distal forearm)
• Zone 9 (proximal forearm)

Treatment of extensor tendon injuries may require operative intervention, depending on the complexity of the injury and the zone of the hand involved.[5, 6] For treatment of injuries to specific zones of the hand, see Technique. The goal of repair is to restore tendon continuity and function, with a secondary goal of allowing early motion of the injured digit. Optimal preparation and technique are critical for minimizing adhesions and scar tissue formation and ensuring the best possible outcome.

Extensor tendon injuries are often more difficult to treat than flexor tendon injuries, owing to several issues specific to extensor tendons. The extensor mechanisms of the hand are in a superficial position, not enclosed in tendon sheaths (as flexor tendons are), and often have limited retraction after injury.

Extensor tendons also tend to be thinner and flatter than flexor tendons are, as well as being in very close proximity to bony structures. This leaves them highly susceptible to adhesions and shortening, which can severely impair function and range of motion.

With injuries that are proximal to the anatomic juncturae tendinum, extensor function may still be preserved distally. Additionally, up to 90% of an extensor tendon can be lacerated and still retain preserved function to gravity, necessitating careful physical examination and wound exploration.[7, 4, 8]

Extensor tendon injuries may be iatrogenic as well, occurring either as a consequence of surgical error or as a complication of a previous procedure or medication (eg, a fluoroquinolone). Extensor tendon ruptures following plating of wrist and hand fractures are well documented, including ruptures that have been reported after intramedullary nailing of pediatric forearm fractures.[9, 10]

Indications for extensor tendon repair include the following:

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

Repair can be accomplished immediately in the ED or after a delay of up to 7 days following the injury.[11] Simple lacerations can be repaired in the ED. If repair is delayed or postponement is necessitated by contamination or complexity, then irrigate and debride the wound, approximating the skin loosely with interrupted sutures, and place the hand in a volar resting extension splint.[12]  Ideally, lesions proximal to zone 6 should be treated in an OR; such injuries tend to require significant exposure of the tissues for appropriate reapproximation of the tendon.[4]

Extensor tendon repair should not be attempted in the ED or acute care setting in any of the following circumstances:

• Unavailability of an appropriately skilled physician
• Contaminated injuries, particularly open zone 1, 3, or 5 "fight bite" injuries
• Presence of associated bony fractures, open joint space, or significant overlying skin loss (which requires an orthopedist or hand surgeon for repair)
• Injuries proximal to zone 6 - Caution is required with these injuries, owing to the frequent necessity of significant surgical exposure to achieve adequate repair

In these cases, the repair should be performed by an experienced hand surgeon, preferably in the OR.

Anatomy

Several anatomic structures contribute to the extensor mechanism, including the extrinsic muscles of the forearm, intrinsic muscles such as the interosseous and lumbricals, and fibrous structures.

The extrinsic tendons pass through the extensor retinaculum on the dorsum of the wrist. This structure is divided into six compartments, each of which has tendons that pass through.

The third compartment is of particular importance in injury patterns. Injuries to the distal radius can result in rupture of the extensor pollicis longus (EPL), which passes through this compartment. Of significance, the sixth compartment contains the extensor carpi ulnaris (ECU), which serves as a major stabilizer for the distal radioulnar joint (DRUJ) as well as extends the wrist.[4, 7]  Also significant anatomically is the presence of the extensor indicis proprius (EIP) and the extensor digiti minimi or quinti (EDM or EDQ), which extend the index and small fingers, respectively.

The extensor apparatus of the triphalangeal digits has three separate insertion sites and is formed through a complex interplay among the extrinsic extensors, the intrinsic extensors, and the digital ligaments. Proximally, it is attached at the level of the metacarpal heads by a sagittal band, which centers the tendon and prevents hyperextension. The most important insertion site is the insertion of the central slip at the base of the middle phalanx to extend the PIP joint. There is a third insertion point distally to extend the DIP joint, comprising the conjoined lateral bands.

It is important to be aware of the insertion sites of the extensor tendons during repair. (See the image below.)

For more information about the relevant anatomy, see Hand Anatomy and Wrist Joint Anatomy.

Many emergency departments (EDs) and acute care facilites use prepackaged laceration kits. These may contain much (though typically not all) of the equipment needed for the repair of extensor tendons.  Additionally, at some facilities, sterile instrumentation may have to be requested from the operating room (OR).

Equipment used for anesthesia includes the following:

• Povidone-iodine solution (see the image below)
• Syringe, 10 mL
• Needle, 25 or 27 gauge
• Local anesthetic solution

Equipment used for wound irrigation and preparation includes the following:

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

Equipment used for tendon and skin repair includes the following:

• Sterile gloves
• Sterile drapes
• Gauze pads, 4 × 4
• Needle holder
• Skin hooks (2)
• Retractors
• Sharp and blunt-nosed scissors
• Small hemostats, several
• Single-toothed forceps
• Nonabsorbable, synthetic, and braided suture (3-0, 4-0, or 5-0) - Typical examples of appropriate brands of suture material are TiCron and Ethibond
• Nylon suture (4-0 or 5-0) for skin repair - Silk suture (which has high tissue reactivity) and chromic suture (which dissolves before the tendon heals adequately) should be avoided; the exception is in young children and infants, in whom the use of chromic suture for skin closure is acceptable, given their healing rates and their poor psychological reaction to suture removal in the clinic

Equipment used for wound care and splinting includes the following (see the image below):

• Topical antibiotic ointment
• Gauze pads
• Elastic gauze bandage or tape
• Splint material (fiberglass, plaster, or aluminum foam)
• Shears

Anesthesia

Adequate anesthesia is required for thorough wound exploration and tendon manipulation. Local digital or field blocks are typically adequate for this purpose in the acute care setting.

Lidocaine 1% or 2% or bupivacaine 0.25% or 0.5% without epinephrine (see Local Anesthetic Agents, Infiltrative Administration) is preferred. Some hand surgeons are becoming increasingly comfortable with using manufacturer-prepared local anesthetics with epinephrine (in a 1:100,000 ratio).[13, 14]  However, unless the physician is comfortable and experienced with their use, these preparations should be avoided out of concern for the possibility of causing ischemic injury to a digit whose blood supply may already be compromised by an acute injury. Epinephrine should not be used in the setting of tobacco use or peripheral vascular disease.

Local or digital nerve block is warranted for finger injuries (see Hand, Anesthesia: Blocks). Field or regional nerve block should be used for hand injuries (see Local Anesthesia and Regional Nerve Block Anesthesia).

For operative surgical repairs, wide-awake surgery is well accepted. In this approach, patients are not sedated, analgesia is with lidocaine-epinephrine (local only), and a tourniquet is only occasionally used as needed. The acronym WALANT (Wide Awake Local Anesthetic and No Tourniquet) is often used for this technique. A prime benefit of WALANT is that the patient is able to move his or her fingers during the operative repair, which enables intraoperative verification of the adequacy of the repair.[13, 14, 15]

The patient should be placed supine on a procedure table or a gurney with an attached armboard. It is important to make sure that the patient is in a comfortable position so as to limit movement during the procedure. The patient’s hand should be level with his or her body or heart.

A thorough history should be obtained and a complete physical examination performed. The patient history should include the following:

• Mechanism of injury
• Position of the digit during injury
• Handedness
• Occupation

It is also important to determine cleanliness of the wound. Physical examination of extensor tendon injuries should always include strength/function against resistance, two-point discrimination, and adequate wound exploration and exposure. Testing of radial nerve function in particular, but also median and ulnar nerve function, is imperative during physical examination to determine the extent of injury.

Important aspects of treatment include the following:

• 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 ^[16]
• 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 (though it is acceptable to approximate the skin edges loosely with suture)
• Refer all patients to an orthopedic or hand surgeon as well as to a certified hand therapist for appropriate rehabilitation following repair
• Encourage early mobilization, which is associated with improved outcomes ^[17]

Initial measures

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 (see Patient Preparation).

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 middle to upper arm, and inflate it 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.

If a blood pressure cuff is being used, wrap the cuff with rolled gauze once it is inflated. 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 be left in place for longer than 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.

Handling of tendons

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

The size and thickness of extensor tendons vary greatly from the proximal zones to the more distal zones. Proximally, tendons are thick and round; distally, they become thinner and flatter. Suturing techniques should be tailored to the location of the lesion (see below).[4]

Suture techniques

Appropriate suture techniques include the modified Kessler stitch and the modified Bunnell stitch (see the image below).

Modified Kessler stitch

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 reenter 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 ipsilaterally. Once this is complete, the two free ends of the suture are on the same side of the tendon. Apply delicate tension to the sutures, and gently approximate the two tendon ends. Tie the suture ends with a square knot that remains buried between the tendon ends.

Modified Bunnell stitch

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 reenter 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. Reenter 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 ipsilaterally. Once this is complete, the two free ends of the suture are on the same side of the tendon. Apply delicate tension to the sutures and gently approximate the two tendon ends. Tie the suture ends with a square knot that remains buried between the tendon ends.

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 the skin edges. Place the last suture to anchor to the knot. (See the image below.)

For more information on suturing, see Suturing Techniques.

Splinting techniques

Splinting techniques vary according to the zone of injury.[4, 18, 19, 20]

Dorsal splint for zone 1 injury (mallet finger splint)

Measure and cut an aluminum, foam-backed splint so that the splint sits just distal to the proximal interphalangeal (PIP) joint and ends at the distal tip of the nail. Place the splint on the finger, keeping the distal interphalangeal (DIP) joint in slight hyperextension. Avoid excessive 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. (See the images below.)

Dorsal splint for zone 3 injury (boutonnière splint)

Measure and cut an aluminum, foam-backed splint so that the splint lies just distal to the metacarpophalangeal (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. (See the images below.)

The specific approach to extensor tendon repair depends on the location and nature of the injury (see the image below).

Zone 1

Injury in zone 1 (DIP joint) often results in mallet finger deformity. It can be open but is more likely caused by forceful flexion of the DIP joint in an extended digit. This causes rupture of the tendon or avulsion from its insertion on the distal phalanx. If this is left untreated, the patient can develop retraction of the central band, resulting in swan-neck deformity.[7, 8]

Open injury is treated as follows:

• Dermatotenodesis
• Mallet finger splint/Kirschner wire (K-wire) fixation (see the video below)

A retrospective cohort analysis by Simonian et al assessed the benefit of adding K-wire fixation to suture repair and splinting as compared with suturing and splinting alone in 50 patients with open Zone 1 extensor tendon injuries.[21] The outcomes measured were final range of motion (ROM) and lag. Although the two groups did not differ significantly with regard to ROM and mean duration of splinting, an increased incidence of lag was associated with the K-wire group.

Closed injury is treated as follows:

• Conservative management/splinting recommended
• Immobilization of the DIP joint in slight hyperextension with sparing of the PIP joint for at least 6 weeks without removal of the splint
• Surgical treatment for closed injuries is indicated or considered if avulsed fracture fragment is greater than one third of the joint surface ^[4]
• Type 1 (no avulsion) and type 2 (small avulsion with laceration at or proximal to the DIP with loss of tendon continuity) - Mallet finger splint
• Type 3 (intra-articular avulsion fracture with dorsal displacement, loss of skin/subcutaneous cover/tendon substance) - Orthopedic or hand surgeon performs operative repair

Zone 2

Injury in zone 2 (middle phalanx) is often sustained with direct sharp laceration/crush injuries. Less than 50% laceration of the tendon is considered stable, and no intervention is recommended.

Laceration of more than 50% of the tendon should be repaired with a figure-eight suture or a suture of similar tensile strength; some authors advocate use of a Silfverskiöld cross-stitch for zone 2 repairs (see below). A paramount concern should be to avoid shortening of the tendon in zone 2, which can result in altered flexion at the DIP joint. Some authors advocate the use of a running interlocking horizontal mattress suture for distal injuries in zones 2-5.[22, 23]

Open injury is treated as follows:

• Dermatotenodesis
• Mallet finger splint/K-wire fixation (see the video below)

Closed injury is treated as follows:

• Type 1 (no avulsion) and type 2 (small avulsion) - Mallet finger splint
• Type 3 (intra-articular avulsion fracture with dorsal displacement) - Orthopedic or hand surgeon performs operative repair

Zone 3

Injury in zone 3 (PIP joint) results in boutonnière deformity, typically 10-14 days after the initial injury, secondary to disruption of the central slip at the PIP joint.[18]  The central tendon is most commonly injured.[12]  Treatment is as follows:

• Open injury - Orthopedic or hand surgeon performs operative repair
• Closed injury - Dorsal boutonnière splint or referral to a hand surgeon for operative repair

Feuvrier et al described four extensor tendon central slip defects treated in an emergency setting with the Oberlin bypass procedure, which uses a free tendon graft intercalated between the extensor indicis proprius (EIP) and the base of the middle phalanx.[24]  At 9 months, functional outcomes were comparable (average mobility, 0-13-72°). The two patients who were working at the time of injury were able to return to work in month 3. At final follow-up (>5 years), average active mobility was 0-5-76.5°.

Zone 4

Because the extensor tendon becomes broader over the proximal phalanx, partial lacerations are often observed, and zone 4 (proximal phalanx) injuries are commonly associated with fractures of the proximal phalanx. Therefore, always test the tendon against resistance during examination.

Open injury is treated as follows:

• Modified Kessler or modified Bunnell using 5-0 nonabsorbable suture
• Splint/K-wire fixation
• Volar splint for 6 weeks in extension

Zone 5

Closed ruptures (both traumatic and spontaneous) of the sagittal bands are often seen in patients with rheumatoid arthritis. Open "fight bite" injury often is a partial laceration that includes the central extensor tendon and sagittal bands. These tendon lacerations can be easily missed because the remaining intact tendon can often maintain extensor function. Furthermore, the lacerated tendon retracts with extension of the digit from its injured flexed position, thus masking or hiding the injured tendon from visualization through the laceration. Complete lacerations are unusual, owing to the breadth of the extensor apparatus here.

Open injury in zone 5 (MCP joint) is treated as follows:

• 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 injury is treated as follows:

• Splint the MCP joint in neutral position (vs operative repair)

Early active mobilization programs (eg, relative motion extension [RME] orthosis and controlled active motion [CAM]) are commonly used after zones 5 and 6 extensor tendon repairs.[25]

Zone 6

Zone 6 (dorsum of the hand) is the most superficial region of the hand. Injury is associated with a good prognosis for repair, owing to the broad structure of the tendon, its extrasynovial nature, and the lack of association with joint spaces. Treatment involves the following:

• Modified Bunnell using 4-0 nonabsorbable suture or a 3-0 core stitch with an epitendinous running suture
• Volar splint

Zone 7

Zone 7 (wrist) is an uncommon site, and injury in this zone is often associated with open lacerations or closed ruptures and distal radius fractures (the extensor pollicis longus [EPL] tendon in particular). It often involves the extensor retinaculum and is at risk for the development of adhesions after repair.[12]  Typically, an orthopedist or hand surgeon performs operative repair.

Zones 8 and 9

Injuries in zones 8 and 9 (dorsal and proximal forearm) are often associated with musculotendinous junctions and muscle bellies. Multiple figure-eight sutures or sutures of similar tensile strength are used to repair muscle bellies. An orthopedist or hand surgeon performs operative repair. Static immobilization of the wrist in 30-45° of extension is maintained for at least 4-5 weeks postoperatively.

General complications include infection, tendon rupture, and adhesions.

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 ^[26]
• Decreased wrist mobility
• Retraction from the initial site of injury

Zone 6 complications include retraction from the initial site of injury (less likely than in 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 (EDC).

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 splinting.[11, 27]