Thumb Extensor Tendon Laceration Repair

This case consists of repairing an extensor tendon laceration of a thumb. Extensor tendon lacerations are one of the most common soft tissue injuries of the hand. Surgical repair of the tendon was offered, and the operation was performed using wide-awake local anesthesia no tourniquet (WALANT) technique. Intraoperatively, a complete laceration of the extensor tendon was confirmed repaired using a modified Kessler technique and reinforced with an epitendinous repair. Before closure, the patient tested competency of the repair with confirmation of restoration with the active extension to ensure proper function. The patient was placed in a reverse thumb spica splint following wound closure. Postoperatively, the patient was immobilized in full thumb extension for approximately two weeks and then converted to a removable splint and prescribed supervised hand therapy for a total recovery of 8–12 weeks.

Extensor tendon; laceration; tendon repair; walant.

Extensor tendon lacerations are relatively common injuries to the hand. In the United States, they are estimated to cause over 25% of all soft tissue injuries.⁴ Without intervention, these injuries can lead to impairment of hand function.² Patients are often men with laboring occupations.³ The dominant hand of patients is more commonly injured, with the thumb being the most likely digit, followed by the index and middle fingers, while the small finger is the least affected.^2, 19 

Anatomically, extensor tendons are divided into six compartments at the wrist level, typically numbered from radial to ulnar as follows.³ The memo code is: 2 2 1 5 1 1.

• Compartment 1 has two tendons: the abductor pollicis longus (APL) and extensor pollicis brevis (EPB) tendons.
• Compartment 2 has two tendons: the extensor carpi radialis longus (ECRL) and extensor carpi radialis brevis (ECRB) tendons.
• Compartment 3 has one tendon: the extensor pollicis longus (EPL) tendon.
• Compartment 4 has five tendons: four tendons of the extensor digitorum communis (EDC) and one tendon of extensor indicis proprius (EIP).
• Compartment 5 has one tendon: the extensor digiti minimi (EDM) tendon.
• Compartment 6 has one tendon: the extensor carpi ulnaris (ECU) tendon.
• Fibro-osseous sheaths separate these compartments with the extensor retinaculum over the top of the compartments to prevent bowstringing of the tendons. 

Kleinert and Verdan's system classifies the extensor tendons into eight zones.⁷ The odd zones cover the joints, and the even zones are between the joints. The tendon excursion and thickness increase from distal to proximal, requiring stronger repair. Moreover, more distal tendon injury results in inferior outcomes than more proximal injuries. Zone I refers to the area over the DIP joint leading to mallet finger deformity; zone II encompasses the middle phalanx; zone III refers to the site over the PIP joint leading to boutonniere deformity; zone IV is over the proximal phalanx; zone V refers to the site over the MP joint and is mainly injured with clenched fist bite; zone VI encompasses the metacarpal; zone VII is over the wrist joint; and zone VIII involves the extensor tendons between the musculotendinous junction and the wrist joint.⁷ 

The patient presented in this case incurred a complete zone IV extensor tendon laceration over the dorsal thumb with inability to actively extend the thumb, which necessitated exploration and surgical repair. The injury occurred within one week before surgery.

Any open wound to the dorsal hand should prompt evaluation for an extensor tendon injury. The laceration site over the dorsum of the hand with altered cascade of the resting posture of the hand as well as inability to actively extend a joint distal to a laceration indicates potential damage to an extensor tendon. It is also essential to perform an exam against resistance as partial lacerations can still extend without resistance but are painful or weak with resistance. These tendons are commonly examined by having the patient place their hand flat on a surface and being told to extend each digit.² Occasionally, full extension of a finger can still occur even with an extensor tendon laceration as some joints have multiple extensors (as seen with the EDM and EIP). Additionally, if the laceration is proximal to the junctura tendinea, which are interconnections of the extensor tendons in zone VI, the patient may still be able to extend the finger even if the extensor tendon proximally is lacerated.

Radiographs can be taken to identify potential fractures or foreign bodies.⁵ Advanced imaging is generally not required. In equivocal cases where the diagnosis is uncertain, then advanced imaging with an ultrasound or MRI can be considered.

From a surgical perspective, Miller’s criteria are typically used to evaluate the extent of injuries. These criteria state that surgery is indicated if:⁴

• More than 25% of the tendon has been cut
• The patient is unable to extend the digit.
• There is associated contamination requiring a formal washout and debridement.
• The joint is unstable.
• The patient can comply with the postoperative protocol.

As discussed above, extensor tendon injuries are commonly grouped into eight zones, with each having a different recommendation for treatment. Type II mallet injury, an open laceration in zone I, requires surgical intervention, while closed mallet injuries can usually be treated nonoperatively.

Zone II injuries are often due to lacerations or crush injuries. Treatment options are based on the presence of extensor lag. Without extensor lag, splinting can be recommended; however, extensor lag is an indication for surgical intervention.²

Zone III injuries can lead to boutonniere deformities. The lateral bands can maintain active extension, so the deformity may not present until 10–14 days after the injury.⁸ Closed injuries can be treated with splinting. Surgery is recommended with open lacerations, displaced avulsion fractures of the central slip insertion, and failed non-operative management.² 

Complete lacerations should be treated surgically in Zone IV followed by 4–6 weeks of volar splinting to allow passive extension.

Zone V injuries are unique in that they are typically open and are commonly seen as fist bite trauma. The primary treatment recommendations include irrigation and debridement (if a human bite). The tendon is repaired if the wound is clean; otherwise, the wound is left open for delayed repair.² 

Stronger sutures are required in zone VI-VIII lacerations because of larger tendon diameter and greater excursion and tension. To avoid overstretching the repair, it is recommended to splint all fingers even if only one tendon is repaired.¹⁰ Results of surgical repair in these zones are generally better than the more distal zones. Repair is followed by immobilization of the wrist in 30 degrees of extension for 4–6 weeks, followed by another 4–6 weeks of therapy. 

Thumb extensor injuries are common; however, due to the width of the MCP joint, complete lacerations of all components, including EPL and EPB, are rare.¹² EPB repair does not have clear recommendations as an intact EPL can still extend the MCP joint. When the EPL is lacerated, surgical repair is indicated. Open injuries typically consist of primary repair followed by 4–6 weeks of splinting the thumb in extension, followed by another 4–6 weeks of therapy. A primary repair as described here can readily be performed within 2–4 weeks of the injury.

Tetanus prophylaxis and antibiotics should be considered based on the recommendations for tetanus and the cleanliness of the open wound. It is recommended to repair these injuries within two weeks to achieve better results.² 

The procedure in our patient was done using wide-awake local anesthesia no tourniquet (WALANT) technique. This WALANT technique is safer and less expensive, but more importantly, allows us to test our repair while still in the operating room. 

As with any lacerations, the following reconstructive principles should always be followed: restoring vascular supply, stabilizing the wound bed, and reestablishing skeletal stability.⁶ It is also vital to have early movement of the joints. This has been shown to decrease adhesions and contractures.¹³ Passive range of motion (ROM) in the splint is usually started early after surgery, active assisted exercise in the splint after two weeks, and active ROM out of the splint can be allowed after 4–6 weeks.¹³

Superior outcomes are expected in the more proximal zones. Time to repair is another determining factor for better results. When repair is done within five days of the injury, patients gain 98% of their original ROM, while repairs done after five days have a 90% chance of gaining full ROM.¹⁵ The distal zones are more prone to stiffness, adhesions, rerupture, or extensor lag.

Complications consist of tendon rerupture, decrease in ROM, adhesions, extension lag, loss of flexion, and finger deformities.² Swan neck and boutonniere deformities might also occur in zone I-II and zone III injuries, respectively. Adhesions can be potentially reduced by early mobilization of the joints when possible.¹⁶

Children under six years of age usually heal more rapidly and regain full ROM even with prolonged immobilization. They also have lower complication rates than adult populations.¹

We demonstrated a successful repair of a complete extensor tendon laceration in zone III of the thumb. The degree of injury can be challenging to determine preoperatively as some joints have multiple tendons working together to extend a digit. However, a thorough physical exam is essential. The time from injury to repair is important for better outcomes. However, tendon retraction is much less than that seen with flexor tendons allowing for delayed direct repair. Laceration over the thumb MCP can involve EPL, EPB, or both. Various extensor repair techniques include modified Kessler, modified Brunelli, four-strand cruciate, and mattress sutures. Our preferred repair consists of a core 4-0 suture using locked modified Kessler to avoid bunching the repair. It is then reinforced with 1–3 cross-stitch sutures (figure-of-eight) based on the surgeon’s preference. Care is taken to avoid capturing surrounding tissue with the repair, including: capsular tissue, periosteum, or subcutaneous tissue, to allow for optimal tendon excursion.

Extensor tendon repair surgery can be performed under any type of anesthesia, but repair using local anesthesia is recommended, often now referred to as WALANT technique. It allows the surgeon to test the repair, assess and adjust repair tension, confirm adequate tendon excursion, and observe joint motion intraoperatively. Moreover, the repair strength can be tested to communicate better with the physical therapist regarding the permitted ROM, and the patient can witness their repair to deliver confidence in their postoperative recovery and therapy. The WALANT technique continues to gain popularity because of its safety profile, decreased expense, and intraoperative advantages listed above. 

Our patient had an uncomplicated repair and demonstrated full thumb extension and tendon excursion before wound closure. The patient was placed in a reverse thumb spica splint on the volar thumb to immobilize the IP, MCP, and CMC joints in extension and counteract active flexion. 

Early mobilization is widely accepted after tendon repair to avoid adhesions; however, we tend to move slower with extensor tendons. The patient is placed in the reverse thumb spica splint for 2–4 weeks to avoid tension on the repair, followed by a removable splint and hand therapy for 6–8 weeks. Alternatively, dynamic splinting in MCP lacerations can be started after three days to allow MP joint flexion to about 30 degrees, keeping the wrist in 45 degrees of extension.²⁰ About 3–5-mm extensor tendon glide by a controlled arc of motion limits adhesion formation. It is shown that 60 degrees of thumb IP motion creates a 5-mm tendon glide at Lister’s tubercle. Overall recovery may take 8–12 weeks, which should be discussed with patients to set goals and expectations.

Nothing to disclose.

The patient referred to in this video article has given their informed consent to be filmed and is aware that information and images will be published online.