Extensor Tendon Lacerations 

Updated: Jun 26, 2018
Author: Ginard I Henry, MD; Chief Editor: Joseph A Molnar, MD, PhD, FACS 

Overview

Background

Extensor tendon lacerations of the hand and fingers are quite common constellations of injuries. Most of these acute injuries to the hand present in the emergency department and are frequently treated there.[1] This fact gives a false sense of security, and the complexities of certain extensor tendon injuries are often incorrectly assessed. An extensor tendon laceration should receive the same diligence as a flexor tendon laceration. More often than not, such injuries should be treated in the operative suite. The soft tissue elements of the dorsal hand and digits are thin in comparison to the flexor side; therefore, dorsal hand and finger injuries are frequently associated with extensor tendon damage. Extensor tendon injuries are also commonly associated with deep structure damage, such as bone, joint, and ligamentous support; up to two thirds of all extensor tendon lacerations have concomitant injuries.[2, 3, 4]

Extensor tendon injuries can be grouped into 2 large categories: 1) acute simple laceration and 2) complex extensor tendon laceration with associated features. Although the diagnosis and treatment of simple lacerations are usually straightforward, certain aspects critical to ensure the optimum outcome are discussed further below. A complex laceration includes associated injuries of surrounding structures or dysfunction that arises from the disruption of the tendon or surrounding structures (eg, mallet finger, boutonniere deformity, sagittal band disorder).[5] This article reviews the current understanding of diagnosis and treatment of the complete range of extensor tendon laceration issues.

History Of The Procedure

The history of tendon reconstruction can be traced back to the times of Hippocrates and Galen. Interestingly, Galen (131-201 AD), in his Ars Parva, stated that tendons were composed of both ligaments and nerves. He warned, therefore, that placing sutures in tendons would lead to pain, twitching, and eventual convulsions. This erroneous concept was not refuted until 1682, when Meekren observed that tendons are insensitive and described the successful repair of incompletely severed tendons. Modern tendon repair surgery was promoted by Kirchmayr, who, in 1917, published a method of "locking" suture in tendon repair, variants of which are still in use today.[6]

Anatomical and functional understanding of the extensor system was advanced significantly by Albinus, who first illustrated the basic structure in extensor tendon anatomy in 1734. Further progress of extensor tendon dynamics and balance forces concepts were made by Fowler in 1942. Landsmeer also contributed to the understanding of the extensor system's dynamic interplay with the oblique retinacular ligament in 1949.[2] See Relevant Anatomy for a detailed discussion of anatomy.

Presentation

Extensor tendon laceration can result from various injuries. The most common mechanisms are sharp object direct laceration, crush injury, avulsions, burns, animal or human bites, and deep abrasions. A study by Naito et al found that 88% of patients with a distal radius fracture with a dorsal roof fragment had an extensor pollicis longus (EPL) tendon injury, with 36% of the study’s patients having a laceration.[7]

Extensor lacerations are accompanied by various degrees of skin injury, ranging from minimal (as in puncture wounds) to large avulsions, which can cause significant loss of domain of both elements.

Because of the superficial location of the extensor tendons in the wrist and hand, the laceration often easily directly observed on physical examination with manipulation of the overlying skin. The underlying joint is passively flexed and extended for full visualization of the injury area.

The most common condition wherein the tendon laceration is present outside the area of the skin laceration is the fight bite. In this situation, the metacarpophalangeal joint is flexed and makes contact with an opponent's teeth (see image below). The resultant extensor tendon laceration is located proximal to skin laceration when the hand is in resting position with the MP joints extended, which is the normal position of the hand, especially when being medically examined. In the acute setting, most extensor tendon lacerations exhibit some loss of extensor function, whether it is a decrease in active extension range of motion, decrease in extension strength, or complete loss of extension of affected joints.

Fight bite. Fight bite.

In the most straightforward case, the patient presents with one or more digits that stay more flexed than the others when the patient attempts to extend all fingers. This indicates a complete laceration of the extensor tendon on the affected digits. However, if all the extensors in the hand are completely lacerated, then the fingers stay flexed at rest or at attempt to straighten. Also, the position of the fingers does not change regardless of the position of the wrist; this indicates loss of the normal tenodesis effect.

In less straightforward cases, a tendon laceration can be present on examination, but the degree of laceration or surrounding anatomy can hide an extension deficit. Up to 80% of the extensor tendon may be lacerated without loss of function, but the chance of delayed rupture is increased when the laceration includes more than 40% of the tendon. Therefore, the dorsal hand and wrist wound must be explored well when any suspicion of tendon injury exists.

At the wrist, 3 dedicated wrist extensors (ECRL, ECRB, ECU) and the finger extensors aid in wrist extension. Therefore, a single wrist extensor laceration can be missed on an initial function examination; thus, careful direct examination must be performed. Finger extension tendon laceration also can be masked. The index and small fingers have 2 extensor tendons apiece (EDC-II and EIP for the index finger; EDC V and EDM for the small finger), and masking could be present if only one is lacerated. Also, extensor tendon laceration of the dorsal palm occurring proximal to juncturae tendineae may also mask extensor dysfunction. Juncturae tendineae are intertendinous fascia connections that attach diagonally between the tendons of the EDC.

Extensor system of the hand. Note the juncturae te Extensor system of the hand. Note the juncturae tendineae that interconnect the extensor digitorum communis (EDC) tendons.

The purpose of the juncturae is to coordinate the extensor motion of the digits. The interconnection of the juncturae allows continue extension of the affected digit if an extensor tendon laceration occurs proximal to the junctura. Understanding this anatomical subtlety avoids missing the diagnosis of an extensor tendon laceration.

Debris is often present in these wounds, and particles need to be completely cleared for adequate healing, for prevention of infection, and to attain an unobstructed view of injured area. For open dirty wounds of the hand and wrist, after the full sensory examination is complete, local blockage of the extensor area should be performed. This allows adequate cleansing of the wounds without pain or muscle dysfunction, since the extensor muscle bellies and innervations lie much more proximal. After a thorough wound debridement, the direct extensor tendon examination and muscle function testing should be performed.

Indications

As with most normal structures, significant disruption should be repaired when possible. Most lacerations of the extensor system should be repaired. However, certain lesser degree lacerations can do well without repair. A laceration of the extensor over the proximal phalanx involving 40% of tendon, in which the patient can extend the finger against resistance, do well with or without repair.[8] Small partial extensor lacerations can sometimes demonstrate triggering but do not exhibit the delayed rupture exhibited by lacerations of >40% of the extensor tendon. The general principles and timing of management for extensor tendon injuries are similar to those for flexor tendon injuries. In combined repairs, flexor tendon rehabilitation must take priority.

Associated fractures are common with extensor injuries in the digits. In closed injury over the dorsum of the proximal interphalangeal (PIP) joint, suspect extensor tendon injury. Because of the superficial nature of the extensor tendons and the lack of significant delicate and critical adjacent structures (as opposed to the presence of the neurovascular bundle in a flexor tendon injury) these repairs can be performed immediately in the emergency department, urgent care, or office setting, given the proper lighting and instruments.[1, 9] (For a detailed description of extensor tendon repair in an emergency department or office setting, see Medscape Reference article Extensor Tendon Repair.) If the repair is likely to be complicated by injury to additional structures, an operating room is the best setting for the repair.[9]

When deciding when and where to perform an extensor repair, one of the first questions to address is infection risk due to contamination of the wound. An extensor tendon laceration wound that is not infected or severely contaminated can be repaired immediately. Extensor tendon laceration wounds with significant debris contamination or high risk of future infection (eg, fight bites) must be taken to the operating room for a thorough debridement and washout before repair. The nature of this type of contamination requires optimal lighting, instruments, and surgical support uniquely found in the operating suite. At the completion of the debridement, the clinical decision must be made whether to directly repair the extensor tendon or delay the repair for a course of antibiotics and observation to avoid wound infection.

A study by Al-Qattan indicated that partial extensor tendon lacerations greater than half the width of the tendon can be conservatively treated by immediate nonresistive active mobilization (4 wks), followed by resistive exercises, without the employment of splints or sutures. Specifically, this applied to lacerations in zones II, IV, and VI-VIII of the fingers and II, IV, and V of the thumb. The study included 39 patients, all of whom achieved full range of motion without extension lags by 8- to 9-month follow-up.[10]

Relevant Anatomy

As with all disorders of the hand, diagnosis and correct therapy application hinges on a thorough understanding of the relevant anatomy.[11, 12] The upper extremity contains 12 extensor tendons. These tendons comprise an extensor system that dorsally maneuvers the wrist, thumb, and all fingers. Extensor tendons also participate in the radial and ulnar deviation of the wrist and contribute to the supination and pronation of the wrist and thumb. The primary origin site is the lateral epicondyle of the humerus and proximal forearm.

As the extensor tendons travel from proximal to distal, they form an arrangement that can be described as a deep group and a superficial group. The superficial group consists of extensor carpi radialis longus (ECRL) and extensor carpi radialis brevis (ECRB), the extensor digitorum communis (EDC), the extensor digiti minimi (EDM [otherwise known as extensor digiti quinti (EDC)]), and the extensor carpi ulnaris (ECU). The deep group comprises the abductor pollicis longus (APL), the extensor pollicis longus (EPL), the extensor pollicis brevis (EPB), and the extensor indicis proprius (EIP). Also coursing along with the tendons in the deep compartment is the deep branch of the radial nerve, which is otherwise referred to as the posterior interosseous nerve (PIN). It provides innervation to all the aforementioned extensor tendons. See the table below for a complete extensor tendon list.

Table. Extensor Tendons of the Hand (Open Table in a new window)

Abbreviation

Full Name

Insertion

Function

Origin

Ext. Compartment

APL

Abductor pollicis longus

Base on thumb metacarpal

Abduction of thumb

Proximal radius and ulna, interosseous ligament

I

EPB

Extensor pollicis brevis

Base of thumb proximal phalanx

Extension of thumb proximal phalanx

Proximal radius and interosseous ligament

I

ECRL

ECRB

Extensor carpi radialis longus/brevis

Base of metacarpal II

Base of metacarpal III

Extends and abducts hand

Lateral epicondyle

II

EPL

Extensor pollicis longus

Distal phalanx of thumb

Extends thumb IP joint

Proximal ulna

III

EDC

(4 tendons: II - V)

Extensor digitorum communis

Proximal and mid. phalanges of digits II-V

Extends digits II - V

Lateral epicondyle

IV

EIP

Extensor indicis proprius

Extensor hood of digit II

Extends digit II

Proximal ulna and interosseous membrane

IV

EDM (EDC)

Extensor digitorum minimi (quinti)

Proximal phalanx, digit V

Extends digit V

Lateral epicondyle

V

ECU

Extensor carpi ulnaris

Base of metacarpal V

Extends and abducts hand

Lateral epicondyle and proximal ulna

VI

 

As the extensor tendons cross the wrist, they course under the extensor retinaculum. The extensor retinaculum prevents the tendons from dorsal displacement caused by natural tendency to develop a straight line from tendon origin to insertion, known as bowstringing, and is divided into the tendons in 6 extensor compartments by vertical septae. See the image below.

The extensor tendons of the wrist and hand are div The extensor tendons of the wrist and hand are divided into 6 compartments at the dorsal wrist, each containing specific tendons.

The first extensor compartment contains the EPB and the APL. The second compartment contains the radial wrist extensors, the ECRL and ECRB. The third compartment is occupied by the EPL. The EPL is notable for the diagonal course that it takes after it deviates around the dorsal radius bony protrusion called the Lister tubercle. The EIP and the 4 EDC tendons make up the fourth compartment. The fifth compartment holds the EDM tendon, and the sixth compartment holds the ECU.

The tendons travel distally past the extensor retinaculum to their insertion sites. The ERCL inserts on the dorsal base of the index metacarpal. The ECRB inserts on the dorsal base of the long finger metacarpal, as it is the most central extensor tendon. This fact is important to note when tendons are selected for tendon transfer. The ERCB should not be used for a transfer donor tendon, if possible, because the resultant wrist extension will deviate to the radial or ulnar side because of the laterality of the remaining tendons.

All the extensor tendons to the hand are extrinsic, that is, no tendons that extend the digits originate in the hand. As the digital extensors travel over the hand, dorsum extensor juncturae tendineae are formed to cause interconnections between tendons. These interconnections are important to understand when evaluating extensor injuries. Juncturae tendineae can cause a misdiagnosis of an extensor tendon laceration because they can aid continual extension of a digit whose tendon was cut proximal to the juncturae. See the image below.

Extensor system of the hand. Note the juncturae te Extensor system of the hand. Note the juncturae tendineae that interconnect the extensor digitorum communis (EDC) tendons.

Several unique aspects of the extensor tendon system are important to note. Unlike the flexor tendons, extensor tendons do not have flexor sheaths except for at the wrist, as tendons pass below the extensor retinaculum. The EDM tendon is usually split into 2 separate slips as it crosses over the wrist and travels to the metacarpophalangeal (MP) joint. The fifth dorsal compartment, in which the EDM travels, is located just dorsal to the distal radioulnar joint.[13] The EDC tendon to the small finger is estimated to be absent in 54% of the population.[14]

Extensor apparatus of the fingers

The extensor apparatus of the fingers is called an apparatus or system because of the complex interplay between the multiple extensor tendons, the intrinsic muscle system, and the many interconnecting ligaments between the tendons and the volar plates. The extensor apparatus of the digits begins just proximal to the MP joints. See the image below.

Depiction of sagittal bands, lateral bands, and th Depiction of sagittal bands, lateral bands, and the relationship of the ligamentous structures.

As the extensor tendons travel over the MP, a dorsal sling of transverse fibers is present. The sling attaches to the extensor tendon dorsally and passes palmarward on each side of the MP joint to attach to the volar plate and the transverse metacarpal ligament. This dorsal sling is called the sagittal band. These transverse fibers are layered in a crisscross pattern that changes its arrangement as the finger flexes and extends.[13]

MP joint extension is accomplished by the contraction of the finger extensor tendons and its attachment to the proximal phalanx via sagittal band fibers. The sagittal band acts both as a static tether to prevent radial or ulnar displacement of the extensor tendon and as a dynamic tether that allows proximal and distal gliding of the extensors tendons during flexion and extension. Complete laceration of the sagittal bands on either side can cause instability in the extensor tendon position as it travels across the MP joint. Laceration to the radial side of the sagittal band causes far more instability than injury ulnar side.[15] Complete laceration of one side of the sagittal band causes a subluxation of the extensor tendon to the opposite side of the laceration when the MP joint is flexed. When the MP joint is extended and tension is removed from the EDC, the tendon snaps back into the central position.

The extensor apparatus becomes a complex interplay of intrinsic muscle contribution as it travels from the MP joint distally. Three intrinsic sets of muscles (volar interossei, dorsal interossei, and lumbricals) contribute dynamic function to the extensor system through the lateral slips. See the image below.

Both the intrinsic muscle and the extensor digitor Both the intrinsic muscle and the extensor digitorum communis (EDC) tendon dynamically contribute to the extensor system of the digits.

The tendons of the interossei muscles split in two; the superficial slip inserts on the proximal phalanx (causing MP flexion), and the deep tendon becomes part of the lateral slip. Interossei muscles contribute to the lateral slip on both sides of the finger while the lumbrical tendons only join the lateral slip on the radial side.

In discussion the extensor mechanism, some confusion often arises in the terminology of lateral slips and lateral bands. The lateral slip is the tendon by which the intrinsic muscle contributes (as just previously discussed) to the extensor mechanism. The lateral band is the extrinsic contribution (EDC tendon) to the extensor mechanism. The lateral slip and lateral band join together distal to the central slip insertion to make up a conjoined lateral band. The lateral slip gives tendon attachments to the central slip and terminal tendon to help extend the proximal interphalangeal (PIP) and distal interphalangeal (DIP) joints. Likewise, the EDC tendon provides the major portion of the central slip. It splits into 2 tendinous branches on either side of the central slip, which join with the lateral slip to make the conjoined lateral band. Finally, both sides merge to form the terminal tendon, which inserts on the dorsal aspect of the distal phalanx and extends the DIP.

Between, around, and over this extensor system array are ligaments and fascial constructs (also called the reticular system), which aid the function and interplay of the extensor tendons. See the image below.

Extensor retinacular system. Extensor retinacular system.

The principal components of the retinacular system are the transverse and oblique ligaments (eg, Landsmeer ligament). The transverse fibers originate from the flexor sheath and proximal phalanx on the volar aspect, pass through a window in the Cleland ligament, and insert into the lateral bands and triangular ligament dorsal to the axis of proximal interphalangeal joint rotation. The deeper and more tendinous oblique retinacular ligament arises from the volar proximal interphalangeal joint capsule and proximal two thirds of the middle phalanx and inserts distally into the conjoined tendon (conjoined lateral band).

Distal to the proximal interphalangeal joint, the lateral bands first are separated by a triangular ligament and then fuse to form a conjoined tendon, which inserts into the base of the distal phalanx. The extensor hood is free to slide proximally with MP extension and distally with MP flexion. With the hood in the distal position, the interossei contribute to MP flexion through their vertical fibers, with little effect on the interphalangeal joints. With the hood in the proximal position and the MP joints fixed in extension, the interossei, through the oblique fibers of the lateral bands, are able to extend the interphalangeal joints.

Conversely, the lumbrical muscles are effective IP extensors irrespective of the degree of MP flexion. Similar to the interossei, they provide flexion of the MP joint via their vertical fibers. The lateral bands normally lie dorsal to the axis of motion of the extended PIP joint and shift volarward with PIP flexion. The triangular ligament prevents the lateral bands from shifting volar to the axis of motion to become flexors of the PIP joint. The primary function of the EDC is MP function, but with full MP extension or MP extension blocked, the EDC can extend the IP joints. The EPL traverses the third dorsal compartment of the wrist. It adducts and supinates the first ray and extends the MP and IP joints.

The extensor pollicis brevis and abductor pollicis longus are important stabilizers of the first metacarpal base. The extensor pollicis brevis extends the carpometacarpal and MP joints, inserting into the base of the proximal phalanx. It occasionally inserts into the distal phalanx, as well. The anatomy of the thumb MP joint resembles the PIP joint anatomy of the digits. The adductor and abductor pollicis longus tendons contribute to a dorsal expansion, which has transverse fibers acting like the retinacular system to stabilize the tendons of extensor pollicis brevis and extensor pollicis longus. The intrinsics are able to extend (but not hyperextend) the IP joint through fibrous interconnections in the dorsal expansion.

 

Workup

Diagnostic Procedures

Bedside ultrasonography is more sensitive and specific than physical examination for detecting tendon lacerations. In one study, sensitivity, specificity, and accuracy of US were 100%, 95%, and 97%, respectively. A cadaveric study by Defzuli et al indicated that dynamic US has a sensitivity and specificity of 100% in detecting lacerations of the extensor tendons of the fingers and thumb, along with a positive predictive value of 1.0, and that static US has a sensitivity, specificity, and accuracy of 85%, 89%, and 88%, respectively.[16]

Bedside ultrasonography in the emergency department takes less time to perform than traditional wound exploration techniques or MRI.[17]

A 3-view x-ray of the hand, wrist, or forearm must be performed on all but the most benign extensor tendon laceration injuries to rule out foreign bodies or bony injury. Also, in all blunt trauma cases, radiographs are used to evaluate for possible fractures or dislocations.

For diagnosis of partial tears, which are especially common in rheumatoid patients, ultrasonography and MRI have been investigated but demonstrate a low sensitivity of 0.33 and 0.27, respectively.[18]

 

Treatment

Surgical Therapy

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.

Regions of the dorsum of the hand have been divide Regions of the dorsum of the hand have been divided up into extensor zones to further describe the location of an extensor tendon laceration. Defining a laceration per zone area enables better communication and relates to the complexity of the needed repair.

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.[19]

Injuries at Specific levels

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.

  • 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.

  • 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.[20] 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.[21] See the image below.

Boutonniere deformity. Boutonniere deformity.

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.[22] 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).[23, 24]

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 tendineae 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.[23]

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.[25] 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.[26]

Surgical Technique

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.

Primary closure of thumb extensor tendon laceratio Primary closure of thumb extensor tendon laceration with the figure-of-8 technique.

Alternatively, a modified simple core suture such as the Kirchmayr suture technique can be used to repair thinner region extensor tendons.[27] See the image below.

Kirchmayr tendon laceration repair suture techniqu Kirchmayr tendon laceration repair suture technique.

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.

Four common core and epitenon tendon repair suture Four common core and epitenon tendon repair suture techniques.

Studies have shown that biomechanical properties (2-mm gapping and maximal load) have the best results with the modified Becker technique.[28] However, all techniques in a 2005 study had sufficient strength to maintain integrity through forces normally incurred in early active mobilization therapy protocols.[28]

One caveat with all suture techniques is that application and tendon end revision can sometimes result in tendon shortening.[29] 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.

Preoperative Details

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.

Postoperative Details

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.

Follow-up

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.[30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40] 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[32, 38, 41] to immediate controlled active motion[34, 42] to dynamic active motion protocols.[43] 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[34] ) 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.[30, 33, 44, 45]

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.[46]

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.

Complications

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.

Swan-neck deformity. Swan-neck deformity.

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.

Boutonniere deformity. Boutonniere deformity.

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.