What is Extensor Tendon Injury in the hand?
Tendons are responsible for connecting muscles to bone. The extensor tendons are located on the back of the hand and fingers. They let you open your hand and straighten your fingers.
Extensor tendon injury is a cut or tear to one of these tendons. When they are damaged, you can lose the ability to extend your hand and/or finger(s).
Extensor tendon injuries are more frequent than flexor tendon injuries and are very common (61%) as they are not protected as well as the flexor tendons due to their superficial location and lack of overlying subcutaneous tissue. Extensor tendon injuries can cause serious functional impairment.
To repair extensor tendons the surgeon needs the same skills as flexor tendon repair and is not a simple challenge, which is common misconception. Lacerations of the extensor tendon system can occur at any site. Extensors are particularly difficult for surgeons because of their reduced size compared with the flexors and their lack of collagen-bundle linkage, which reduces the grip strength available for the suture material.
Anatomy of Extensor Muscles of the hand.
Muscles and Tendons
The muscles of the hand are divided into intrinsic and extrinsic groups. The intrinsic muscles are located within the hand itself, whereas the extrinsic muscles are located proximally in the forearm and insert to the hand skeleton by long tendons.
The extensor muscles are all extrinsic, except for the interosseous-lumbrical complex, which is involved in interphalangeal joint extension. All of the extrinsic extensor muscles are innervated by the radial nerve. This group of muscles consists of 3 wrist extensors and a larger group of thumb and digit extensors.
The extensor carpi radialis brevis (ECRB) is the main extensor of the wrist, along with the extensor carpi radialis longus (ECRL) and extensor carpi ulnaris (ECU), which also deviate the wrist radially and ulnarly, respectively. The ECRB inserts at the base of the third metacarpal, while the ECRL and ECU insert at the base of the second and fifth metacarpal, respectively.
The extensor digitorum communis, extensor indicis proprius, and extensor digiti minimi extend the digits. They insert to the base of the middle phalanges as central slips and to the base of the distal phalanges as lateral bands. The abductor pollicis longus, extensor pollicis brevis, and extensor pollicis longus extend the thumb. They insert at the base of the thumb metacarpal, proximal phalanx, and distal phalanx, respectively.
The extensor retinaculum prevents bowstringing of tendons at the wrist level and separates the tendons into 6 compartments. The extensor digitorum communis is a series of tendons to each digit with a common muscle belly and with intertendinous bridges between them. The index and small finger each have independent extension function through the extensor indicis proprius and extensor digiti minimi.
The extrinsic flexors consist of 3 wrist flexors and a larger group of thumb and digit flexors. They are innervated by the median nerve, except for the flexor carpi ulnaris (FCU) and the flexor digitorum profundus to the small and ring finger, which are innervated by the ulnar nerve.
The flexor carpi radialis is the main flexor of the wrist, along with the flexor carpi ulnaris and the palmaris longus, which is absent in 15% of the population. They insert at the base of the third metacarpal, the base of the fifth metacarpal, and the palmar fascia, respectively. The FCU is primarily an ulnar deviator. The 8 digital flexors are divided in superficial and deep groups. Along with the flexor pollicis longus, which inserts at the thumb distal phalanx, they pass through the carpal tunnel to provide flexion at the interphalangeal joints.
At the palm, the flexor digitorum superficialis tendon lies volar to the profundus tendon. It then splits at the level of the proximal phalanx and reunites dorsal to the profundus tendon to insert in the middle phalanx. The flexor digitorum profundus perforates the superficialis tendon to insert at the distal phalanx. The relationship of flexor tendons to the wrist joint, metacarpophalangeal joint, and interphalangeal joint is maintained by a retinacular or pulley system that prevents the bowstringing effect.
The intrinsic muscles are situated totally within the hand. They are divided into 4 groups: the thenar, hypothenar, lumbrical, and interossei muscles.
The thenar group consists of the abductor pollicis brevis, flexor pollicis brevis, opponens pollicis, and adductor pollicis muscles. All are innervated by the median nerve, except for the adductor pollicis and deep head of the flexor pollicis brevis, which are innervated by the ulnar nerve. They originate from the flexor retinaculum and carpal bones and insert at the thumb’s proximal phalanx.
The hypothenar group consists of the palmaris brevis, abductor digiti minimi, flexor digiti minimi, and opponens digiti minimi. They are all innervated by the ulnar nerve. This group of muscles originates at the flexor retinaculum and carpal bones and inserts at the base of the proximal phalanx of the small finger.
The lumbrical muscles contribute to the flexion of the metacarpophalangeal joints and to the extension of the interphalangeal joints. They originate from the flexor digitorum profundus tendons at the palm and insert on the radial aspect of the extensor tendons at the digits. The index and long finger lumbricals are innervated by the median nerve, and the small and ring finger lumbricals are innervated by the ulnar nerve.
The interossei group consists of 3 volar and 4 dorsal muscles, which are all innervated by the ulnar nerve. They originate at the metacarpals and form the lateral bands with the lumbricals. The dorsal interossei abduct the fingers, whereas the volar interossei adduct the fingers to the hand axis.
The wrist joint is a complex, multiarticulated joint that allows wide range of motion in flexion, extension, circumduction, radial deviation, and ulnar deviation. The distal radioulnar joint allows pronation and supination of the hand as the radius rotates around the ulna. The radiocarpal joint includes the proximal carpal bones and the distal radius. The proximal row of carpals articulates with the radius and ulna to provide extension, flexion, ulnar deviation, and radial deviation. This joint is supported by an extrinsic set of strong palmar ligaments that arise from the radius and ulna. Dorsally, it is supported by the dorsal intercarpal ligament between the scaphoid and triquetrum and by the dorsal radiocarpal ligament.
At the intercarpal joints, motion between carpal bones is very restricted. These joints are supported by strong intrinsic ligaments. The 2 most important ones are the scapholunate ligament and the lunotriquetral ligament. Disruption of either one can result in wrist instability.
The 3 Gilula lines have been described to represent the smooth contour of a greater arc formed by the proximal carpal bones and a lesser arc formed by the distal carpal bones in normal anatomy. All 4 distal carpal bones articulate with the metacarpals at the carpometacarpal (CMC) joints. The second and third CMC joints form a fixed unit, while the first CMC forms the most mobile joint.
At the metacarpophalangeal joints, lateral motion is limited by the collateral ligaments, which are actually lateral oblique in position, rather than true lateral.
This arrangement and the shape of the metacarpal head allow the ligaments to be tight when the joint is flexed and loose when extended (ie, cam effect). The volar plate is part of the joint capsule that attaches only to the proximal phalanx, allowing hyperextension. The volar plate is the site of insertion for the intermetacarpal ligaments. These ligaments restrict the separation of the metacarpal heads.
At the interphalangeal joints, extension is limited by the volar plate, which attaches to the phalanges at each side of the joint. Radial and ulnar motion is restricted by collateral ligaments, which remain tight through their whole range of motion. Knowledge of these configurations is of great importance when splinting a hand in order to avoid joint contractures.
Extensor tendon injuries may be caused by:
• A cut or laceration to back of hand or fingers
• Broken bones
• A crush injury
• An open wound or cut
• Jamming a finger
• Nerve compression
Factors that may increase your chance of an extensor tendon injury include:
• Participating in certain sports
• Constant text messaging on mobile phones
Symptoms may include:
• Inability to open hand or fingers
• Numbness or weakness
• Cut to back of the hand or fingers
• Jammed finger
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. 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.
You will be asked about your symptoms and medical history. A physical exam will be done. During the exam, you will be asked to bend and straighten your fingers. Your doctor will also check your fingers for sensation, blood flow, and strength. You may be referred to a hand surgeon or an orthopedist—doctor who specializes in bones.
Taking a detailed history is important and knowing the mechanism of injury, position the finger was in during the injury, age, occupation and handiness as in other hand injury to plan treatment and management of extensor tendon injuries. The mechanism of injury is important for several reasons.
Most lacerations of the dorsal aspect of the hand and fingers can be considered ‘clean’ but any contamination would need debridement, which needs to be discovered during the history. It is unusual for patients to always admit to being in fights, however knowing whether it is a human bite is necessary. Whether the patient thinks there may be a foreign body is also necessary as these foreign bodies may then be missed.
Physical examination needs to include systemic and in depth examination of both hands. The site of the laceration and the inability to extend a joint distal to it indicates that the extensor tendon may have been at least partially divided. If the extensor tendon is completely severed the finger may be resting in flexion. When testing function of the extensor muscle of the hand, extension must be against resistance as you will not pick up a partial laceration.
Extension of the hand digits is performed by several muscles with their bodies in the forearm that continue to the dorsal aspect of the wrist and insert onto the digits. Extensor digiti minimi is responsible for extension of the fifth digit. It can be tested by asking the patient to lie their hand flat on a surface and hyperextend the fifth digit. The extensor digitorum tendons extend digits two through five.
The hand can be laid flat again on a surface and the tendon of each finger tested by having the patient hyperextend the digits against resistance. Extension of the second finger is also performed by extensor indicis, which can be tested in a similar fashion to extensor digiti minimi. Extension of the first digit is controlled by two muscles, extensor pollicis longus and brevis.
The path of these two tendons defines the “anatomical snuffbox” which contains the radial artery and the scaphoid bone of the wrist. Extension of the thumb at the interphalangeal joint and the metacarpophalangeal joint can be tested separately against resistance.Sensation using two-point discrimination or the surgeon’s choice should be carried out to determine the radial nerve injury particularly if extensor tendon injury is suspected.
However median and ulnar nerve should be tested also. Radiographs are needed to assess any associated fracture as they will need to be fixed before tendon and nerve injuries d
uring surgery. A human bite can cause metacarpal fractures. Glass and other foreign objects can also be picked up on x-ray.
Full extension of the digits at the individual small joint of the hand can be possible even after laceration. The extrinsic and intrinsic components of the extensor system can act solely independently. The distal IP joint finger extension can still be possible with complete severance of the main extrinsic extensor tendon at or proximal to the metacarphalageal joints.
Furthermore oblique retinacular ligaments can results in weak distal extension through the tenodesis effect but this can fatigue and the extension lad can become obvious. The extensor mechanism characteristically fails at the insertion of the central slip and the terminal tendon producing characteristic deformities including boutonniere and mallet. It must be remembers that mallet deformity does not always happen acutely making injuries to the central slip more difficult to identify.
In addition mallet fingers can be complicated by extensor lag at the distal IPJ (DIPJ) but also the development of a ‘swan neck’ deformity as excess tension builds at the central slip insertion into the base of the middle phalanx.
Images may be taken of your hand. This can be done with digital x-ray or magnetic resonance imaging. High-resolution sonography allows identification of difficult to diagnose partial and complete extensor tendon injuries and also facilitates the earlier detection and differentiation of extensor tendon injuries.
Talk with your doctor about the best plan for you. Depending on the type of injury, you may require surgery. Surgery may be scheduled right away or within several days.
Treatment options include the following:
Depending on the type of injury, you may receive antibiotics to prevent infection. Steroid injection to help you relief pain may be given for a short time and also other non-steroidal anti-inflammatory drugs may be administered.
Some extensor tendon injuries are treated with a hand splint. Splints are worn until healing has occurred. This is usually several weeks to several months depending on if static splint or functional splints are recommended for your injury.
Indication for Surgery
Tendons that are cut or ruptured require surgery. The hand surgeon may sew the tendon back together. A pin may need to be inserted through the bone to form a type of inside splint.
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.
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. If the repair is likely to be complicated by injury to additional structures, an operating room is the best setting for the repair.
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.
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 infections.
Our physical therapist or occupational therapist will work with you for several weeks to regain your strength and range of motion. Right after surgery, movement will be limited. This will allow your hand to heal.
The ultimate aim of any rehabilitation is to obtain healing with minimal gapping and prevent adhesions. Static mobilisation was the traditional method of postoperative rehabilitation but complications including tendon rupture, adhesion formation requiring tenolysis, extension lad, loss of flexion and decreased grip strength have all been documented.
Early mobilisation has been introduced for flexor tendon injuries because it decreases adhesions and subsequent contractures. Furthermore mobilisation has shown to enhance DNA synthesis at the repair site, improve tensile strength and increase vascularity.
It has now shown to be more useful in certain areas for extensor injuries as well. Mowlavi et al., studied early controlled mobilisation versus static splinting. Functional outcomes at 4, 6 and 8 weeks were improved after dynamic compared to static splinting. The authors recommended that dynamic splinting should be available for those who are motivated to return early to functional capacity.
Bulstrode et al., similarly found that ROM for the early mobilisation group at 6 weeks postoperatively was greater than static mobilisation but disappeared at 12 weeks. Grip strength was also assessed at 12 weeks postoperatively. The difference in grip strength was significantly greater in the early-mobilised group and to uninjured hand compared to the immobilised and uninjured hand.
Our highly specialized hand therapy programs for early mobilisation rehabilitation programs can be in two categories
(1) Early active mobilisation and
(2) Early controlled mobilization using a dynamic splint.
Early controlled motion with a dynamic extensor splint has been found to decrease adhesions and subsequent contractures taking into cognizance duration, splinting technique and frequency and force intensity of exercises used for rehabilitation, further illustrating that further studies are needed.
The patient needs to be very cooperative and the hand therapist needs to monitor carefully in postoperative rehabilitations. Therefore a team approach needs to be made with rehabilitation tailored to the individual adjusting management as they go along.
Short-Term Goals :
1. Management of acute pain with a combination of heat therapy, electrotherapy, and massage therapy
2. Passive Mobilizations of the DIP, PIP, MCP and wrist joints with consistent and sustained stretch where needed. To be repeated severally at home.
3. Differential tendon gliding facilitation to the 1st,2nd, 3rd, 4th, and 5th digits.
4. Muscle and Tendon facilitation to assist tendon gliding
5. Electrical Muscle stimulation to the extensors and flexors muscles
6. Splinting programs consisting of night splint and day functional splints
7. Sensory re-education to the 1st, 2nd, 3rd, 4th and 5th digits.
Long-Term Goals :
Healing time for tendon repair will usually take between 8-12 weeks but restorations of function and ability to assume full activity, load and stress can take up to 6 months to 12 months. A daily and consistent hand therapy may help to shorten the recovery time to 3 to 4 months.
Long-term goals will be to:
1. Reduce the tendon adhesion at the DIP, PIP and MCP of the 1st, 2nd, 4th and 5th digits and the wrist joint
2. Reduce the swelling at the digits, the dorsal and volar surface of the left hand and the wrist joint
3. Achieve full degrees flexion at the DIP, PIP joints of the 2nd, 3rd, 5th digits
4. Achieve full degrees flexion at the MCP joints of the 2nd 3rd and 5th digits
5. Increase gross muscle power of the 1st, 2nd, 3rd, 4th and 5th digits
6. Increase gross muscle power of the 1st, 2nd, 3rd, 4th and 5th digits in extension
7. Re- educate in manipulation and gripping of large objects.
You can always consult us to access our highly specialized Hand Therapy Rehabilitation programs that customized to individuals. Why don’t you make that call today?
#ImageCredit : Medscape
#AnatomyIllustration : Medscape