Orthopaedic Surgery - Extensor Tendon Laceration

Basics

Extensor tendon lacerations are relatively common because the extensor tendons lie superficially along the dorsum of the hand and wrist, making them vulnerable to direct injury.

Disruption of an extensor tendon often produces an immediate change in the resting posture of the involved finger or hand.

Functional Consequences

The specific deformity depends on the level of injury.

A distal injury near the distal interphalangeal (DIP) joint may produce a mallet-type posture, while an injury involving the extensor mechanism over the proximal interphalangeal (PIP) joint may lead to a boutonniere pattern.

Extensor tendon injuries may impair active extension of the fingers, thumb, or wrist.

Typical Patient Population

These injuries occur most commonly in young adults.

Males are affected more frequently than females.

Classification

Extensor tendon lacerations are generally classified as partial or complete, based on the amount of tendon disruption identified during examination or wound exploration.

Timing of Repair

Many complete extensor tendon lacerations require operative repair.

Repair may be performed in the emergency department or operating room depending on the level and complexity of injury.

Because the extensor mechanism has relatively limited retraction and is not constrained within a pulley system like the flexor tendons, repair can often still be performed successfully within approximately 2 weeks of injury.

Epidemiology

Extensor tendon lacerations are less common overall than flexor tendon injuries.

Etiology

The usual mechanism is a sharp laceration over the dorsal hand, finger, or wrist.

The superficial position of the extensor tendons makes them particularly susceptible to knives, glass, machinery, and other penetrating injuries.

Fight-Bite Injury

A laceration over the dorsal metacarpophalangeal joint may result from striking another person’s teeth.

This so-called fight bite is particularly important because the tendon, joint capsule, and MCP joint may be contaminated with oral flora.

Associated Conditions

Extensor tendon injuries may occur together with open fractures, open joints, retained foreign bodies, or traumatic arthrotomy.

These associated injuries may substantially alter management.

Diagnosis

Signs and Symptoms

A dorsal laceration may reveal the tendon ends directly within the wound, sometimes with only minimal exploration.

A change in finger posture or loss of active extension should raise immediate concern for tendon disruption.

Loss of Active Extension

The patient may be unable to actively extend one or more joints distal to the level of injury.

The pattern of weakness helps localize the injured tendon segment.

Mallet Deformity

An injury involving the terminal extensor tendon at the DIP joint causes inability to actively extend the distal phalanx.

The fingertip therefore rests in flexion, producing a mallet deformity.

Boutonniere Deformity

Disruption of the central slip over the PIP joint may eventually produce a boutonniere deformity, characterized by PIP flexion with DIP extension or hyperextension.

This deformity may not always be immediately apparent after injury.

Independent Extensor Tendons

The index and small fingers possess additional independent extensor tendons.

A partial injury may therefore produce only subtle loss of extension strength or range of motion rather than complete inability to extend.

Physical Examination

General Examination

All fingers should be examined individually for active extension.

The wrist should also be assessed for range of motion and extension strength.

Neurologic Examination

A complete neurologic examination should be performed before administration of local anesthetic.

This helps document any associated nerve injury.

Local Anesthetic Block

After the neurologic examination, a local field block can be useful to reduce pain and allow a more reliable assessment of active tendon function.

Pain alone can otherwise limit motion and mimic tendon disruption.

Extrinsic Extensor Testing

One useful method is to place the patient’s palm flat on a table and ask the patient to lift each finger individually away from the surface.

Failure to elevate a specific digit suggests loss of its extrinsic extensor function.

Wound Exploration

The wound should be carefully inspected for partial or complete tendon disruption.

Exploration should also assess for contamination, foreign material, joint penetration, and associated fracture.

Laboratory Tests

Routine laboratory studies are not required for diagnosis.

If operative management is planned, standard preoperative testing may be obtained according to the patient’s age, comorbidities, and anesthetic requirements.

Imaging

Plain Radiographs

AP and lateral radiographs should be obtained when there is concern for an associated fracture, dislocation, or retained foreign body.

Radiographs are particularly important in high-energy trauma or fight-bite injuries.

Differential Diagnosis

Extensor Avulsion Injury

An avulsion injury of the extensor mechanism may cause the same functional deficit as a tendon laceration.

For example, a bony avulsion at the DIP joint can produce a mallet deformity without a sharp tendon transection.

Fracture

A fracture involving the dorsal aspect of the phalanx or metacarpal can also impair active extension and should be excluded radiographically.

Treatment

General Principles

Treatment priorities include wound care, prevention of infection, restoration of tendon continuity when necessary, and protection of the repair during healing.

Management depends on the location, depth, contamination, and completeness of the tendon injury.

Tetanus Prophylaxis

Tetanus immunization status should be reviewed.

A booster or tetanus toxoid should be administered when indicated.

Antibiotics

Antibiotics may be required for contaminated wounds, open fractures, open joints, or bite injuries.

The choice of antibiotic should reflect the likely organisms and mechanism of injury.

Fight-bite wounds require coverage for human oral flora rather than routine skin flora alone.

Irrigation and Debridement

Contaminated wounds should undergo thorough irrigation and debridement.

Devitalized tissue and foreign material should be removed.

Temporary Skin Closure

The skin may be temporarily closed when appropriate until definitive tendon repair is performed.

Grossly contaminated wounds may require delayed closure.

Splinting

The injured hand or finger is generally splinted in extension or a protected position to reduce tendon separation and prevent further injury.

Specialist Referral

Orthopaedic or hand-surgery consultation is appropriate for complete tendon lacerations, complex wounds, associated fracture or joint injury, and uncertain tendon function.

Physical Therapy and Hand Therapy

Rehabilitation depends on the anatomic zone of injury, tendon involved, repair technique, and associated injuries.

The goal is to protect tendon healing while minimizing stiffness, adhesions, and loss of function.

Early Motion

When the repair is sufficiently strong, carefully controlled passive and active motion may be introduced early.

Modern rehabilitation protocols attempt to balance tendon protection with prevention of adhesions.

Surgery

Tendon Repair

For a complete laceration requiring repair, the tendon ends are identified, mobilized, approximated, and sutured.

Nonabsorbable sutures such as 4-0 polypropylene or braided polyester have traditionally been used, with the exact repair technique depending on tendon level and thickness.

Suture Technique

Mattress-type or other core suture configurations may be used to obtain secure approximation of the tendon ends.

The repair should restore appropriate tendon length and alignment without excessive tension.

Proximal Injuries

Lacerations at the level of the wrist or more proximally are usually repaired in the operating room because multiple tendons may be involved and exposure is more extensive.

Comparison With Flexor Tendon Repair

Extensor tendon repair is generally less technically demanding than flexor tendon repair at the same level.

Extensor tendons are not surrounded by a tight pulley system, and postoperative gliding stresses are often lower.

Delayed Repair

Because of this anatomy, definitive repair can sometimes be delayed for up to approximately 2 weeks without a substantial adverse effect on outcome, provided the wound and tendon remain suitable for reconstruction.

Postoperative Splinting

Protective splinting is required after repair while the tendon heals.

The exact splint position and duration depend on the zone of injury and rehabilitation protocol.

Follow-Up

Prognosis

The prognosis is generally good after complete and appropriately performed repair, particularly when the injury is isolated and rehabilitation is well supervised.

Factors Affecting Outcome

Outcome is influenced by the level of injury, wound contamination, associated fracture or joint injury, adequacy of repair, scar formation, and adherence to postoperative therapy.

Complications

Infection

Infection can occur, especially in contaminated wounds, open joints, and bite injuries.

Fight-bite injuries are particularly high risk.

Open Joint Injury

A laceration that penetrates the joint can lead to septic arthritis if not recognized and treated appropriately.

Repair Failure

The tendon repair may rupture if it is overloaded before adequate healing occurs.

Scarring

Scar formation may limit tendon glide and contribute to stiffness or cosmetic changes.

Adhesions

Adhesions between the repaired tendon and surrounding tissue may restrict excursion and reduce active extension.

Loss of Function

Persistent extension lag, stiffness, weakness, or deformity may remain if healing is incomplete or rehabilitation is inadequate.

Patient Monitoring

Follow-up should assess wound healing, infection, tendon integrity, active extension, passive motion, scar formation, and adherence to splinting and therapy.

Serial examination is important to detect early repair failure, progressive stiffness, or adhesions so that rehabilitation can be adjusted promptly.