John S. Taras and Daniel J. Lee
DEFINITION
Traumatic injury to the extensor tendons of the hand and forearm results in the disruption of tendon substance, causing a loss of active wrist or digital extension.
Primary repair of the extensor tendon usually can be performed within 7 days after appropriate irrigation and débridement of wounds and stabilization of any fractures.5
Late reconstruction of extensor tendon injuries presents an operative challenge and often requires the use of tendon transfer and grafting techniques.
ANATOMY
The extensor mechanism of the hand and wrist is a complex system involving balanced interplay between extrinsic and intrinsic components (FIG 1).
The extrinsic extensor tendons are divided into superficial and deep groups in the forearm:
Superficial: extensor carpi radialis longus and brevis (ECRL and ECRB), extensor digitorum communis (EDC), extensor digiti minimi (EDM), extensor carpi ulnaris (ECU), and anconeus
Deep: abductor pollicis longus (APL), extensor pollicis brevis and longus (EPB and EPL), extensor indicis proprius (EIP), and supinator
Wrist extension is provided by the ECRB, ECRL, and ECU.
Finger and thumb extension is provided by the APL, EPB, EPL, EDC, EIP, and EDM.
The radial nerve innervates all extensor muscles of the hand, except the intrinsics, which are innervated by the median and ulnar nerves. The radial nerve’s deep motor branch becomes the posterior interosseous nerve (PIN).
FIG 1 • Tendons on the dorsum of the hand, extensor retinaculum.
There are six fibro-osseous dorsal compartments at the level of the wrist covered by the extensor retinaculum. The contents of each compartment are as follows:
I: APL, EPB
II: ECRL, ECRB
III: EPL
IV: EDC, EIP
V: EDM
VI: ECU
The intrinsic system of the hand consists of the seven interosseous muscles (three palmar and four dorsal) and four lumbrical muscles.
The intrinsic muscles pass volar to the axis of the metacarpophalangeal (MP) joints and dorsal to the interphalangeal (IP) joints; thus, the intrinsic system will flex the MP joints and extend the IP joints.
On the dorsum on the hand, the fibrous bands of the juncturae tendinum connect the extensor digitorum tendons of the long, ring, and small fingers.
This interconnection is what allows grouped extension of the fingers.
The EIP and EDM are ulnar to their respective EDC tendons and function as independent extensors of the index and small fingers.
Over the MP joints, tendons are held in a central position by the sagittal bands, which envelop the MP joint and attach to the volar plate.
The dorsal extensor apparatus is formed distal to the MP joint from contributions of both extrinsic and intrinsic tendons.
The central slip, the continuation of the extrinsic extensor tendon, inserts into the dorsal base of the middle phalanx.
The lateral bands are formed from the intrinsic muscles on either side of the finger and send fibers to the middle phalanx as well as contributions to the central slip.
The lateral bands combine dorsally over the middle phalanx to form the terminal extensor tendon, which inserts on the dorsal base of the distal phalanx.
The transverse and oblique retinacular ligaments stabilize the tendons of the dorsal apparatus.
Traumatic injuries to the extensor tendons can be described in terms of nine anatomic zones (Table 1).3
Traumatic injuries to the extensor tendon of the thumb have a separate numbering system and are divided into five anatomic zones (Table 2).
Even-numbered zones overlie bones and odd-numbered zones overlie joints.
Vascular supply5
Forearm: nutrition via small arterial branches from the surrounding fascia
Wrist: derived from mesotenon; nutrition via diffusion
Hand: derived from paratenon; nutrition via perfusion
PATHOGENESIS
Extensor tendons are susceptible to traumatic injury because of their relatively superficial location and thin tendon substance.
Acute repair within 7 days is recommended, but direct repair of acute injuries is occasionally impractical in cases with extensive soft tissue damage or segmental tendon loss.
In these cases, skeletal stabilization is obtained first (FIG 2), followed by soft tissue coverage, and finally late reconstruction of the disrupted extensor mechanism.
Also, late presentation of traumatic disruptions of an extensor tendon makes direct repair difficult because of tendon retraction and subsequent extrinsic tightness.
Traumatic injury to the extensor tendons can also occur after upper extremity fractures.
Acute rupture of the EPL tendon has been associated with displaced distal radius fractures.
Delayed EPL rupture has been associated with minimally displaced distal radius fractures. These attritional ruptures are generally attributed to compromise of the tendon’s vascular supply by soft tissue damage and hemorrhage after fracture with an intact third extensor compartment.4
Delayed extensor tendon ruptures of the EPL, EDC, and EIP have been reported as a complication after volar and dorsal plate fixation of distal radius fractures.2
FIG 2 • Preoperative picture of a patient with severe soft tissue loss, including extensor muscle, after a motorcycle accident, which required extensor tendon reconstruction.
NATURAL HISTORY
Without treatment, complete extensor tendon disruptions will result in a persistent loss of active extension or incomplete extension of the wrist or digits (or loss of active abduction and extension of the thumb, depending on which tendon or tendons are involved).
A late tendon imbalance resulting from pull of the flexor tendons against a disrupted or weakened extensor mechanism with or without fixed joint contracture may develop if reconstruction is not performed.
PATIENT HISTORY AND PHYSICAL FINDINGS
The patient most commonly has a history of penetrating or blunt trauma to the dorsal forearm or hand with resultant loss of active extension of the wrist, fingers, or thumb (FIG 3). Loss of soft tissue may be associated with the original injury.
In cases of attritional rupture of the EPL tendon, the patient may have a recent or remote history of a distal radius fracture, usually only minimally displaced.
Physical examination methods include the following:
MP extension. Incomplete MP extension indicates extensor tendon disruption in zones proximal to the MP. If the other fingers are not kept flexed, the patient may be able to fully extend the affected finger in the presence of a completely lacerated tendon.
EPL test. An EPL rupture manifests as a loss of extension of the thumb IP and MP joints.
Tenodesis test. A loss of extensor tendon continuity will result in loss of the tenodesis effect. Wrist flexion will have no effect on finger extension.
A complete evaluation of the elbow, forearm, wrist, or hand begins with a thorough inspection of all open wounds and an assessment of the extent of soft tissue compromise.
Local or regional anesthesia can assist with patient comfort during the examination.
A comprehensive neurovascular examination must be performed before using any anesthetic. Special attention is directed to the status of the radial nerve, specifically the PIN.
Compromise in PIN function may result from compression neuropathy, direct injury, or underlying elbow pathology.
If there is a suspicion of joint violation, then injection of sterile saline with or without methylene blue into the joint can verify whether the joint capsule has been disrupted.
IMAGING AND OTHER DIAGNOSTIC STUDIES
AP, lateral, and oblique plain radiographs of the affected area (elbow, forearm, wrist, or hand) are obtained to rule out the presence of a foreign body, underlying fracture, or bony deformity or pathology.
In cases of late presentation of suspected extensor tendon rupture, MRI is occasionally useful to confirm the diagnosis and identify the location of the retracted tendon ends.
DIFFERENTIAL DIAGNOSIS
Radial nerve or PIN palsy
Flexor tendon injury
Intrinsic tightness
Tendon adhesions
Tendon subluxation (MP joint level)
Joint contracture, subluxation, or deformity
Soft tissue contracture
NONOPERATIVE MANAGEMENT
Conservative treatment of injuries proximal to the metacarpals usually is not possible because of tendon retraction and muscle contracture and will result in persistent loss of extension of the wrist or digits.4
Chronic extensor mechanism disorders distal to the metacarpals without fixed deformity will respond to splinting and intensive therapy. Such conservative management may result in an acceptable functional outcome for select patients.
SURGICAL MANAGEMENT
Most extensor tendon lacerations are amenable to direct primary repair if treated relatively early.
Indications for reconstruction of extensor tendon injuries include loss of extension of the wrist, fingers, or thumb resulting in a functional deficit.
When delay or loss of tendon substance precludes a direct repair, tendon grafting or transfer may restore function successfully.
Preoperative Planning
The patient must be provided with a realistic assessment of the potential gains from surgery as well as details of the treatment plan.
Any fixed joint contractures should be identified and treated with therapy and splinting before extensor tendon reconstruction to optimize outcomes.
In cases of severe soft tissue loss, coverage must be obtained before proceeding with extensor system reconstruction.
This may include free or island muscle, fascial, or skin flaps in addition to fullor split-thickness skin grafts.
Positioning
The patient is positioned supine with a hand table attached to the operative side.
A tourniquet is usually used to operate in a bloodless field
Approach
The approach depends on the tendon transfer or grafting technique required and is detailed in the Techniques section.
FIG 3 • Segmental loss of extensor and flexor tendons from a shotgun blast.
TECHNIQUES
END AND SIDE WEAVE JUNCTURES
Tendon transfer or graft junctures are often best secured using an end weave technique (TECH FIG 1).
The Pulvertaft method is a common weave used.
A pointed tendon-grasping and -passing instrument is invaluable and allows one tendon to be brought through the substance of the other tendon with minimal trauma.
The tendon weave is performed at right angles. For example, the first entry is horizontal, the next vertical, and then the third horizontal. At least three weaves are needed.
TECH FIG 1 • End weave technique. The smaller tendon is passed through and sutured.
EIP TO EPL TRANSFER
The distal EIP tendon is identified through a 1-cm incision over the index finger MP joint. The EIP is ulnar to the EDC II.
A second incision is made just distal to the extensor retinaculum at roughly the radiocarpal joint level, and the EIP tendon is identified in the radial aspect of the fourth extensor compartment.
The EIP is readily identified by its distal muscle belly.
The EIP tendon is separated from the EDC II and transected through the incision over the MP joint.
The tendon is then brought through to the proximal incision.
A third incision is centered over the scaphotrapezial trapezoid joint and the distal stump of the disrupted EPL tendon is identified (TECH FIG 2A).
A subcutaneous tunnel is created to connect the incision at the wrist and the incision near the base of the thumb.
The EIP tendon is passed through the tunnel and attached to the distal stump of EPL using an end weave technique (TECH FIG 2B).
Tension should be set so that when the wrist is extended, the thumb IP joint flexes, allowing the tip of the thumb to touch the tip of the index finger. The thumb IP joint should fully extend when the wrist is flexed (TECH FIG 2C).
The thumb is immobilized with the wrist extended about 20 degrees and the thumb IP joint at 0 degrees for 4 weeks.
TECH FIG 2 • Extensor indicis proprius (EIP) to extensor pollicis longus (EPL) transfer. A. After the EIP tendon is identified, it is brought through the proximal incision. The distal stump of the EPL tendon is identified as well. B. The EIP tendon is passed through and is woven into the EPL tendon. C. After proper tensioning, the thumb should extend as the wrist flexes.
END-TO-SIDE SUTURING FOR EDC DISRUPTIONS
A longitudinal incision is made on the dorsum of the hand over the appropriate area.
The disrupted tendon end is identified and isolated.
An end-to-side repair is performed to the adjacent intact tendon.
Tension must be set so that the fingers are in extension when the wrist is flexed and the MP joints are flexed 20 to 30 degrees when the wrist is extended about 20 degrees. The normal flexion cascade must be re-established.
EIP TO EDC (FOURTH/FIFTH) TRANSFER
The EIP tendon is isolated and freed in a manner similar to that described for the EIP-to-EPL transfer.
An incision is made dorsally on the hand, over the disrupted extensor tendons of the ring and small fingers.
The EIP is mobilized and inserted into the distal stump of the disrupted tendon of the small finger.
If disrupted, the extensor digiti quinti (EDQ) is sewn side to side to the transfer.
The distal stump of the ring finger is attached to the adjacent intact common extensor tendon of the long finger. If the EDC to the long finger is also ruptured, it is sewn to the intact EDC to the index while the EDC to the ring is sewn to the EIP transfer (TECH FIG 3).
TECH FIG 3 • Extensor indicis proprius (EIP) to extensor digitorum communis IV/V tendon transfer.
FLEXOR CARPI ULNARIS TO EDC TRANSFER
A longitudinal incision is made over the flexor carpi ulnaris (FCU) in the distal forearm.
The FCU tendon is transected just proximal to the pisiform and is freed up proximally.
A second oblique incision is made 5 cm below the medial epicondyle in the proximal forearm.
The FCU fascial attachments are incised to free up the entire muscle belly.
A third incision begins on the dorsal-ulnar mid-forearm and angles distally toward the tubercle of Lister to expose the disrupted EDC tendons.
A tendon passer or Kelly clamp is passed subcutaneously around the ulnar border of the forearm to pull the FCU tendon into the dorsal wound.
Muscle may be excised from the FCU to reduce bulk.
The FCU tendon is woven through the EDC tendons at a 45-degree angle just proximal to the dorsal retinaculum.
The FCU is secured under maximum tension, with the wrist and MP joints in neutral.
FLEXOR CARPI RADIALIS TO EDC TRANSFER
A longitudinal incision is made over the flexor carpi radialis (FCR) in the distal forearm.
The FCR tendon is identified and transected near its insertion.
The tendon is freed up proximally to allow additional excursion.
A second longitudinal incision is made on the dorsal forearm, extending from the mid-forearm to just distal to the dorsal retinaculum.
The FCR is then passed subcutaneously around the radial border of forearm and delivered into the dorsal wound.
The FCR tendon is then inserted into the EDC tendons and positioned superficial to the retinaculum.
The transfer is secured with the FCR under maximum tension and wrist and MP joints in neutral (TECH FIG 4).
TECH FIG 4 • A–F. Flexor carpi radialis (FCR) and palmaris longus (PL) transfer for loss of thumb and digital extension. A. FCR and PL transected. B. FCR woven into extensor digitorum communis (EDC) II, III, IV, and V. (continued)
TECH FIG 4 • (continued) C–F. Patient demonstrating restored digital and hand extension.
Pronator Teres to ECRB Transfer
An incision is made over the volar-radial aspect of the mid-forearm.
The pronator teres (PT) tendon is identified and followed to its insertion into the radius.
A strip of periosteum is kept intact when freeing up the insertion to ensure sufficient length of the transferred tendon.
The PT muscle is freed up proximally to improve excursion.
The PT muscle and tendon is then passed subcutaneously around the radial border of the forearm.
The tendon is inserted into the ECRB just distal to the musculotendinous junction through a second incision if needed (TECH FIG 5).
The transfer is secured with PT in maximum tension and the wrist in 45 degrees of extension.
Flexor Digitorum Superficialis Transfer for Multiple Extensor Disruption
A transverse incision is made in the distal palm to expose the long and ring superficialis tendons.
The flexor digitorum superficialis (FDS) tendons to III and IV in the distal palm are divided proximal to the chiasma.
TECH FIG 6 • A. Flexor digitorum superficialis (FDS) III and IV transferred to reconstruct segmental injuries of extensor digitorum communis (EDC) II, III, IV, and V. B. FDS III and IV to EDC II–V tendon transfers. The FDS is transferred through a rent created in the interosseous membrane.
TECH FIG 5 • FCR to EDC and pronator teres to extensor carpi radialis brevis tendon transfer.
A longitudinal incision is made on the volar-radial midforearm and the interosseous membrane is exposed.
The two tendons are then delivered into the proximal wound.
Two openings are excised from the interosseous membrane, large enough to pass the muscle bellies through to minimize adhesions.
A J-shaped incision is made on the dorsum of the distal forearm and the tendons are passed through the interosseous membrane.
The FDS III is routed radially, and the FDS IV is routed ulnarly to the profundus muscle mass.
The FDS III is interwoven into the tendons of the EIP and EDC II and III (TECH FIG 6).
The FDS IV is interwoven into EDC IV and V.
Tension is set with the FDS under maximum tension, the wrist in 20 degrees of extension, and the fingers and thumb held in a fist.
STAGED RECONSTRUCTION WITH SILICONE RODS
In patients with loss of soft tissue over the dorsum of the hand and forearm, appropriate soft tissue coverage is obtained first.
At the time of coverage, the proposed path of the tendon transfer or graft is preserved with the use of a silicone tendon rod.
Once maturation of soft tissue has occurred, the appropriate tendon transfer or graft may be performed 2 to 3 months after silicone rod placement (TECH FIG 7).
TECH FIG 7 • A. Silastic spacer (tendon rod) used to create adhesion-free bed. B. Silastic spacer replaced by tendon graft after soft tissue healing and remodeling.
POSTOPERATIVE CARE
Initial splinting should immobilize the wrist in about 30 degrees of extension, the MP joints in about 15 degrees of flexion, and the IP joints in full extension.
If transferred tendons originate proximal to the elbow, the elbow should be immobilized in 90 degrees of flexion with appropriate forearm rotation.
The thumb IP and MP joints should be immobilized in full extension.
After 4 weeks, active range of motion is started under the supervision of a certified hand therapist and with a protective splint. Active-assisted and passive range of motion follows 2 weeks later.
OUTCOMES
Staged extensor tendon reconstruction using a silicone implant followed by tendon grafting for restoration of PIP joint extension was reported to have good results in six fingers with severe dorsal soft tissue injuries, improving hand function in all cases.1
COMPLICATIONS
Extrinsic tightness
Intrinsic tightness
Rupture
Donor deficits
Joint stiffness
REFERENCES
1. Adams BD. Staged extensor tendon reconstruction in the finger. J Hand Surg Am 1997;22:833–837.
2. Al-Rachid M, Theivendran K, Craigen MAC. Delayed ruptures of the extensor tendon secondary to the use of volar locking compression played for distal radius fractures. J Bone Joint Surg Br 2006;88B: 1610–1612.
3. Baratz ME, Schmidt CC, Hughes TB. Extensor tendon injuries. In: Green DP, Hotchkiss RN, Pederson WC, eds. Green’s Operative Hand Surgery, 5th ed. Philadelphia: Elsevier Churchill Livingstone, 2005:187–217.
4. Burton RI, Melchior JA. Extensor tendons—late reconstruction. In: Green DP, Hotchkiss RN, Pederson WC, eds. Green’s Operative Hand Surgery, 4th ed. New York: Churchill Livingstone, 1999:1988–2021.
5. Newport ML. Extensor tendon injuries in the hand. J Acad Orthop Surg 1997;5:59–66.