Extensor Tendon Lacerations Treatment & Management

Once the decision for surgical intervention has been made, the general principles of definitive wound debridement, early tendon repair, and early range of motion hand therapy guide the treatment plan for all extensor tendon injuries. As in all hand surgery, meticulous handling of the tissues and thorough knowledge of the relevant anatomy is vital. In an extensor injury of any area, all the pertinent structures must be carefully dissected and examined. However, because scar formation occurs at every along the entire plane of dissection, judicious restraint must be used in determining the extent of dissection.

Analogous to flexor tendon injuries, the extensor tendon lacerations have been categorized to various zones defined by anatomical boundaries. See the image below.

Up to the forearm, the odd-numbered zones all refer to dorsal surfaces of joints (I – distal interphalangeal [DIP]; III – proximal interphalangeal [PIP]; V – metacarpophalangeal [MP]; VII – carpometacarpal [CMC] and radiocarpal [RC] joints). The even numbers are simply the intervening dorsal regions. In the forearm, the zone IX refers to the proximal half of the forearm. The thumb has its own unique zone definition because it has fewer joints than the fingers, but the same concept applies. Using the "T" modifier, the odd-numbered zones (TI – IP joint, TIII - MP joint, TV - CMC and RC joints) all refer to extensor injuries in the dorsal surfaces of the joints; the intervening areas are again labeled the even zones.

In a study of extensor tendon ruptures in wrists affected by rheumatoid arthritis, Sakuma et al concluded that the number of ruptured tendons and the age of the patient are independently associated with the results of surgical repair (ie, active motion of the tendons following reconstruction). The authors also found evidence that the number of ruptured tendons correlates with surgical delay. In the study, 66 wrists underwent tendon reconstruction along with wrist arthroplasty or arthrodesis, with the affected fingers assessed for active range of motion at 12-week follow-up. ^[21]

Distal interphalangeal joint (zone I)

Complete division of the terminal conjoined tendon beyond the insertion of the oblique retinacular ligaments results in the mallet finger deformity. With time, an associated proximal interphalangeal volar plate relaxation with resultant swan neck deformity often occurs (this mimics the swan neck deformity observed with volar plate rupture). As a general principle, any tendon imbalance tends to result in the opposite deformity in the uninvolved joint. This typically is observed in rheumatoid deformity. ^{[22, 23]}

Open injury

These injuries are invariably intra-articular. Lavage and debridement of the joint, tendon repair, skin closure, and K-wire fixation are the principles of management. A degree of hyperextension is desirable, but skin blanching should be avoided.

Remove the wire after 4 weeks and replace it with a mallet finger splint for 2 weeks. Introduce active flexion during the eighth week.

Closed injury

This type of injury should be treated closed, with the single exception of those with an associated fracture involving a large intra-articular fragment (>30% of the articular surface). Accurate reduction of these large fragments is necessary. A pullout wire tied around a button on the volar pulp and a longitudinal C wire are used (or just the latter, if the fixation is stable). In cases involving smaller fragments, percutaneous transarticular wire fixation avoids the need for open operation, maintains the reduction, and fixes the joint in extension.

In the routine closed injury without bony involvement, use a mallet finger splint, aiming for slight hyperextension. Take particular care to ensure that the dorsal skin is not blanched or jeopardized by local pressure from the splint. Splintage alone produces the best results in closed injures, but it requires absolute patient compliance. The splint should be worn for 6 weeks. Introduce active extension after 8 weeks. If extensor lag is present after this time, reintroduce the splint.

A study by Nagura et al indicated that in patients with an acute closed tendinous mallet injury involving the distal interphalangeal (DIP) joint, oblique K-wire fixation of the joint may offer an advantage over splinting. The investigators found that mean extension lag of the DIP joint was significantly better in the patients who underwent surgery than in those who were treated with splinting (2.1° vs 13.8°, respectively). ^[24]

Established mallet finger deformity

Unopposed flexion of the DIP joint results in stretching of the scar. Early scarring contracts; thus, a trial of splintage may be warranted in the first few months after injury. ^[25] Surgical correction by excision of the redundant scar and prolonged splintage is best for patients with established deformity. Those who don’t respond to this treatment are best treated by DIP arthrodesis in 100º of flexion.

Associated swan neck deformity

This is consequent to the combination of volar plate laxity at the proximal interphalangeal joint and imbalance of the extensor mechanism. It is best corrected by addressing the distal interphalangeal deformity. Alternately, a sliding tenotomy of the central tendon can be performed, taking great care not to produce a boutonnière deformity.

Splinting techniques

Splinting must be applied constantly for a good result to be achieved. PIP joint motion should not be restricted. K-wire fixation causes little articular damage. Use a mallet finger splint for closed injuries.

Middle phalangeal level (zone II)

No clinical deformity is present, since the oblique retinacular ligaments are preserved. Division of the conjoined tendon distal to the insertion of Landsmeer ligaments results in a mallet finger deformity. Repair and immobilize open injuries as for a mallet finger deformity, with the exception that 4 weeks of immobilization is sufficient.

Proximal interphalangeal joint level (zone III)

Disruption of the central slip results in the boutonnière (ie, buttonhole) deformity. ^[26] See the image below.

The head of the middle phalanx herniates through the extensor expansion. As the triangular ligament ruptures, the lateral bands displace volarly. Compensatory distal interphalangeal hyperflexion may be present. Closed injuries easily are missed, but the Carducci test is invaluable: with the wrist and MP joints in partial flexion, test the power of PIP extension. An extensor lag >15° is diagnostic (flexion to diminish the contribution of the lateral bands to PIP extension).

• Open injury: Treat any laceration over the PIP joint as a central slip rupture until proven otherwise. These are best repaired with the PIP joint fixed in full extension. In contaminated wounds, repair is best delayed.

• Closed injury: Treat all closed injuries apart from those involving a large intra-articular bony fragment by splintage. Initial splintage is static or by K wire in uncooperative patients. Dislocation of the PIP joint usually is associated with disruption of the central slip. A bony fragment may be visible on radiographs and is an indication for operative intervention. However, patients usually present not with a boutonnière deformity but rather with diffuse swelling and limited range of motion due to periarticular soft tissue injury.

• Established boutonnière deformity: Patients who present with an established deformity are divided into 2 groups: those with mobile injuries and those with fixed injuries. In the latter group, establishing a full passive range of motion prior to the repair is essential. ^[27] This may require surgical release of the contracted volar structures and passive stretching, or it may require merely the latter. However, obtaining a good result from surgery is difficult. Surgical options include the following:

  • Eaton and Littler technique - Incomplete transection of the lateral bands, allowing them to retract proximally and leaving the oblique retinacular ligament intact

  • Matev technique - One lateral band transferred to the base of the middle phalanx

  • Elliot technique - Anatomic repair of triangular ligament after reduction of the lateral band subluxation; shortening of the central slip by excision of elongated scar

  • Hayward technique

  • The joint is fixed in all options by a transarticular wire. Retain the wire for 6 weeks, followed by external splintage for a variable period according to the extensor delay. External splintage usually requires a dynamic splint (eg, Capener splint, Joint jack, COSCO splint). Splintage is indicated for established deformities, as a preliminary trial in older patients, and following C wire removal in open injuries and after secondary repair.

  • The Fowler procedure involves the section of the conjoined tendon over the proximal section of the middle phalanx, with preservation of the oblique retinacular ligament. This is an option for symptomatic splinting failures (ie, those that fail to regain passive range of motion). Release of the oblique retinacular ligaments may be necessary if the DIP joint cannot be flexed passively following repair, which is often more disfiguring than the boutonnière deformity. Alternately, operative failures can be addressed by arthrodesis, as necessary. The position of arthrodesis follows the normal digital cascade (30-90°). In patients with rheumatoid arthritis, an interpositional arthroplasty is best.

• Swan neck deformity: The Littler oblique retinacular ligament technique for swan neck deformity relocates the one lateral band volarly and inserts it into the volar aspect of the middle phalanx. This functions to tighten as the PIP joint extends. Variations on the original Littler technique include the use of the palmaris longus in the "spiral oblique retinacular ligament" technique. The Littler flexor digitorum superficialis tenodesis routes the free proximal end of the flexor digitorum superficialis tendon through the volar aspect of the middle phalanx.

Proximal phalanx level (zone IV)

The injury may involve the central tendon, the lateral bands, or both. Unilateral division of a lateral band usually does not manifest as a deformity. Division of the central tendon manifests as a boutonnière deformity, but this is a rare occurrence. Division at this level usually involves an open wound. Treatment is by direct repair and K-wire immobilization.

Metacarpophalangeal joint level (zone V)

The division of the extensor hood overlying the MP joint results in an extensor lag. Active extension of the proximal phalanx against resistance is diminished. In the index or little fingers, this may not be evident if the proper tendon is intact (extensor digiti quinti, extensor indicis proprius). ^{[28, 29]}

The most common injury at this level is the fight bite due to human tooth injury. In these contaminated injuries, primary repair is contraindicated. Once the acute infection has been treated, the swelling has lessened, and the passive range of motion has been restored, repair can be undertaken. Splint the MP joints in a full extension splint for 3 weeks. Of importance, the PIP and DIP joints should remain free. Use a dynamic extension splint following removal of the full extension splint until no extensor lag remains.

Metacarpal level (level VI)

The liberal juncturae tendinae tend to mask the underlying deformity. Repair all divided structures. A horizontal mattress suture is often better for these flat structures. If the tendon repair is likely to encounter the extensor retinaculum, dividing the latter is best. Splintage and immobilization are the same as for the MP joint level (zone V) above. ^[28]

Division at the wrist joint (zone VII)

The extensor retinaculum is divided and repaired by Z lengthening. The tendons at this and more proximal levels resemble flexor tendons (ie, round) and should be sutured as such, using a core suturing technique.

Thumb

Division of the extensor pollicis longus at the IP joint level results in a mallet deformity, while division at the metacarpal level only results in the inability to hyperextend the thumb. ^[30] In the examination for extensor pollicis longus transection, passively extending the MP joint is important to neutralize the intrinsic action on the IP joint. Also check for retropulsion of the thumb.

Division of the extensor pollicis brevis results in minimal deformity, or it may resemble a boutonnière deformity. In the latter, the action of extensor pollicis longus draws the IP joint into hyperextension, thus completing the deformity. The volar migration of the extensor pollicis longus tendon below the axis of rotation further compounds this deformity. In repairs to the extensor pollicis longus, supinating and adducting the first ray is important to take tension off the anastomosis. Transfix the involved joint with a K wire. Secondary repair is usually not possible after 4 weeks because of proximal retraction of the extensor pollicis longus. An extensor indicis proprius transfer is a better option. ^[31]

In most people, the extensor tendons are much thinner and of smaller caliber than the flexor tendons. The decrease in caliber becomes more prominent on the more distal end of the tendon. The thinner regions of the tendon may not support the 2-component (core suture and epitenon suture) technique typically applied in a flexor tendon repair. For the thinner regions of extensor tendons, the figure-of-8 suture technique is one of the most common applications. See the image below.

Alternatively, a modified simple core suture such as the Kirchmayr suture technique can be used to repair thinner region extensor tendons. ^[32] See the image below.

Extensor tendon lacerations in zone IV and proximally can usually tolerate a modified 2-component suture technique. Several different techniques exist. Four of the more common repair techniques are the modified Kessler, figure-of-8, modified Becker, and 6-stranded double-loop. See the image below.

Studies have shown that biomechanical properties (2-mm gapping and maximal load) have the best results with the modified Becker technique. ^[33] However, all techniques in a 2005 study had sufficient strength to maintain integrity through forces normally incurred in early active mobilization therapy protocols. ^[33]

One caveat with all suture techniques is that application and tendon end revision can sometimes result in tendon shortening. ^[34] Tendon shortening of more than 4 mm can cause imbalance of extensor-flexor tendon forces across the fingers. Tendon shortening can lead to loss of range of motion and grip strength. Care should be maintained at all steps of the repair to maintain maximum tendon length while ensuring a viable, well-adherent approximation.

If the repair of an extensor tendon laceration is to be delayed (up to 14 days from injury), then the skin wound can be provisionally closed with nonabsorbable sutures and the wrist and hand placed in a splint. A volar plaster or fiberglass splint can be fashioned to prevent flexion of the affected areas. The splint should usually be fabricated starting in the forearm and extending distal to the level of injury. The wrist is maintained in 40-45° extension and the affected digits (MP and IP joints) in no more than 15° flexion. The hand is maintained immobilized with constant hand elevation until definitive surgical treatment.

Postoperatively, the affected arm should be placed immediately in a forearm-based volar splint that extends from the forearm to at least one joint distal to the region of the repair. The wrist should be placed in 40-45° extension to off-load tension on the repair. The MP and IP joints may be placed in slight (10-20°) flexion for stabilization and comfort.

Patients are instructed to maintain elevation until upper extremity swelling is resolved. Most extensor laceration repairs are outpatient procedures, and incisional healing should be evaluated within one week. In most cases, postoperative antibiotics are not indicated.

Postoperative rehabilitation is discussed below. Typically, if static rehabilitation therapy is chosen, nonabsorbable sutures may be removed in 2 weeks. If early mobilization therapy is instituted, then nonabsorbable sutures are removed in 3 weeks.

As with all hand surgery rehabilitation, range of motion (ROM) activity should be commenced as soon as possible without compromising the results of surgical therapy. The preferred rehabilitation after extensor tendon laceration repair (postoperative immobilization vs early ROM activity) is under debate, especially in the case of complicated injuries. ^{[35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45]} Although medical centers differ on the benefits and effectiveness of early ROM, almost all agree that the long-term (>6 mo) outcomes of both forms of rehabilitation are functionally equal.

Not all early activity programs are the same. They range in their level of activity from dynamic splinting ^{[37, 43, 46]} to immediate controlled active motion ^{[39, 47]} to dynamic active motion protocols. ^[48] The essential elements of these therapies include a certified hand therapist managing hand therapy exercise that is started within the first 3-10 days post-operatively. Patients are actively moving the repaired finger in a controlled fashion, primarily limited by the therapist, a dynamic splint (eg, Merritt dynamic splint ^[39] ) that allows for controlled movement, or both. These studies demonstrate early (4-6 wk) improved active and passive ROM; grip strength; and patient satisfaction as compared to static splinting. On the other hand, static splinting has demonstrated less repair site stretching per postoperative time point and better therapy adherence for patients with complex social circumstances and issues with noncompliance. ^{[35, 38, 49, 50]}

A literature review by Collocott et al suggested that after extensor tendon repair in zone V or VI, relative motion extension splinting protocols for early mobilization encourage faster function recovery than do controlled active motion protocols. ^[51]

The least controversial consensus of the extensor tendon laceration repair debate can be summarized thusly:

• For noncomplicated injuries (eg, single finger laceration, no associated injuries, noncrush lacerations) in zone V and distally, an early active ROM protocol (of any variety) is beneficial to early patient outcome.

• For multifinger, complicated injuries (eg, crush injuries with associated damaged structures) in regions proximal to zone V and in patients with compliance or extenuating social issues, immobilization for 3-4 weeks, followed by a progressive ROM exercise protocol, is preferred.

Joint stiffness and tendon adhesions are common complications of even excellent repairs of extensor tendon lacerations. The longer the immobilization period lasts, the higher the chance of joint capsule fibrosis and of forming volar plate adhesions (check-rein ligaments). These issues are mainly treated with hand therapy for stretching out the scarring. Tendon adhesions are always a risk of tendon repair, especially at the site of the repair. Extensor tendons have fewer challenges with this complication than flexor tendons because only one major extensor tendon group is present (vs 2 flexor groups) and because the fibrous-osseous tunnel created by the pulley system does not exist in the extensor system. Most postoperative tendon adhesions can be addressed with therapy; occasionally, tenolysis (surgical clearing of surrounding tendon scar) has to be performed to regain function.

Misdiagnosis or failure to repair significant partial lacerations (>30% of tendon) can result in extension triggering. The partially torn surface can get transitionally caught on nearby structures such as other tendon slips, extensor aponeurosis or the extensor retinaculum. With forced flexion or extension most patients can clear temporary impediment to extensor tendon gliding. However, symptoms worsen over time, and surgical revision of the partial laceration surface is required.

Delayed rupture or failure of tendon repair is a relatively uncommon occurrence. Usually, the cause is a technical error or an underestimation of the repair effectiveness or related injuries that leads to an inappropriate level of early postoperative activity. When tendon repair rupture is diagnosed, early return for revision repair is essential. Tendon grafts maybe required for revision. The patient must informed of the decreased overall function expected in a revision repair and the increased likelihood of further necessary surgery (eg, tenolysis).

Untreated extensor tendon lacerations in certain regions lead to imbalance of forces at the proximal interphalangeal (PIP) joint and cause significant deformities that impact the function of the affected finger and entire hand. A complete laceration at the terminal tendon overlying the distal interphalangeal (DIP) joint causes a lack of extension of the distal phalanx. This chronically flexed position of the DIP joint is called a mallet finger deformity.

A chronic mallet finger that persists over time can lead to further deformity at the PIP joint. The PIP volar plate becomes lax as the individual repeatedly hyperextends the PIP joint in order to compensate for the DIP chronic flexion when attempting to grasp large objects. Over time, a malpositioning of the lateral bands and fixed imbalance of the dynamic and static forces around the PIP joint result in a new deformity, called the swan-neck deformity, that presents with flexion of the DIP joint and hyperextension of the PIP joint. Treatment for this deformity is mostly surgical and should be avoided by proper treatment of the mallet finger before it progresses. See the image below.

Complete central slip lacerations can also result in imbalance at the PIP joint if left untreated. Without extension forces over the PIP joint, it becomes chronically flexed, and the lateral bands slip volar to the central axis of the PIP. This causes a chronic flexion of the PIP joint and extension of the DIP joint as the lateral bands tighten in the malposition. This condition is called a boutonniere deformity and can be effectively treated with therapy if caught in the early stages. See the image below.

As with all surgical procedures, infection and wound dehiscence are possible complications. The risk of infection is increased in a contaminated wound (eg, fight bite) that is not properly cleaned before tendon repair.