Extensor Tendon Injuries of the Hand


Definition/Description

Courtesy of Primal Pictures

An extensor tendon injury is a cut or tear to one of the extensor tendons. Due to this injury, there is an inability to fully and forcefully extend the wrist and/or fingers.

Clinically Relevant Anatomy

Extensor tendons of the hand lie very superficially and the soft tissue covering the tendons is very thin.[1] This makes these tendons susceptible to injuries such as lacerations or open injuries.[1] Another reason is the lack of subcutaneous tissue between the tendons and the overlying skin.[2]

Extensor Digitorum Communis (EDC)

  • Extensor digitorum muscle.png
    Main extensor tendon of the hand[3]
  • centrally placed in the posterior compartment of the forearm
  • Origin:
    • the lateral epicondyle of the humerus via the common extensor tendon, the covering fascia and the intermuscular septa at its sides. In the lower part of the forearm the muscle forms four tendons. These tendons pass deep to the extensor retinaculum. On the dorsum of the hand the tendons diverge towards the medial four digits
  • Insertion:
    • Each tendon helps to form an aponeurosis over the dorsum of the hand – the dorsal digital expansion or extensor hood. It has been suggested to think about the extensor hood as a "moveable triangular hood." The base lies proximally over the metacarpophalangeal joint. Then the sides of the hood wrap around the phalanx. At the proximal interphalangeal joint the hood is reinforced by the interosseus and lumbrical muscles. At the distal end of the proximal phalanx the extensor hood divides into three parts. The central part inserts onto the base of the middle phalanx on the dorsal aspect. The two collateral parts reunite to insert onto the dorsal aspect of the base of the distal phalanx.
  • Innervation:
    • Posterior interosseus branch of the radial nerve
  • Action:
    • The primary action is extension of the metacarpophalangeal joints.
    • It also helps to extend both interphalangeal joints.[3]

Extensor Pollicis Longus (EPL)

  • Extensor pollicis longus muscle.png
    Lies deep to the extensor digitorum in the posterior compartment of the forearm[3]
  • Origin:
    • Lateral part of the middle third of the posterior surface of the ulna and the adjacent interosseus membrane
  • Insertion:
    • At the dorsal surface of the base of the distal phalanx of the thumb
  • Innervation
    • Posterior interosseus branch of the radial nerve
  • Action:
    • Extends all of the joints of the thumb.
    • Also assists in extension and abduction of the wrist[3]

Tendon Zones

Kleur.png
Extensor tendons are located at the dorsal region of the hand and fingers. The function of these tendons is to extend the wrist and the fingers. According to Kleinert and Verdan (1983), there are eight anatomic zones in which the extensor mechanism of the fingers and wrist is divided.[4][5][6] Odd numbered zones refer to injuries over the joints and the even number zones refer to the segments between two joints.[1]
  • Zone I: DIP joint
  • Zone II: middle phalanx
  • Zone III: PIP joint
  • Zone IV: proximal phalanx
  • Zone V: MCP joint
  • Zone VI: metacarpals
  • Zone VII: wrist (carpus and extensor retinaculum)
  • Zone VIII: distal third of the forearm[6][7]

Epidemiology /Etiology

  • more than 50% of acute tendon trauma injuries are extensor tendon injuries[8]
  • reported incidence of 14 cases per 100 000 person-years[8]
  • extensor tendon injuries represent 16,9% of orthopaedic soft tissue injuries[9]
  • common injury in young manual workers[10]
  • mostly men in their 30's as they are the working age group[11]
  • dominant hand more likely to be injured
  • in the UK - these injuries represent up to 30% of all emergency department visits[12]
  • in the USA - estimated to comprise more than 25% of all soft tissue injuries[13]

Mechanism of injury

  • Open wounds[9]
    • Often open wound that needs urgent medical attention and patients present at the hospital
    • Direct lacerations by sharp objects, knifes or scissors
    • Saw injuries
    • Burns
    • Blunt trauma
    • Bites
    • Crush injuries
    • Avulsions
    • Deep abrasions
  • Closed rupture[9]
    • as a result of conditions that weaken the tendon structure such as Rheumatoid Arthritis
    • attrition by internal hardware used for bone fixation
    • under situations of extreme load[5]

Characteristics/Clinical Presentation

Dependent on the zone of injury, different characteristics are shown.

  • Zone I: Mallet finger
  • Zone II: no complete rupture of the tendon, but partially injured[5]
  • Zone III: Disruption of the central slip, also called a Boutonnière deformity or jammed finger. This is characterised by a flexed position of the PIP joint and an extension or hyperextension of the DIP joint[14]
  • Zone IV: injuries are frequently partial, with or without loss of extension at the PIP joint[7]
  • Zone V: fight bite injuries (open injuries) or non-fight bite injuries (for example: blunt trauma): a possible effect of such an injury is a rupture of the sagittal bands, attended with following extensor tendon subluxation[7]. This is presented as a difficulty to actively straighten the flexed MCP joint[5]
  • Zone VI: the MCP joint can still be extended via the juncturae tendinum
  • Zone VII: physical injury to the extensor retinaculum[7]

Differential Diagnosis

  • Mallet Finger[10]
    • refers to a drooping end-joint of a finger.
    • This happens when an extensor tendon has been cut or torn from the bone. It is common when a ball or other object strikes the tip of the finger or thumb and forcibly bends it.
  • Boutonnière Deformity[10]
    • Describes the bent-down (flexed) position of the middle joint of the finger. Boutonniere can happen from a cut or tear of the extensor tendon.
  • Cuts on the back of the hand
    • Can injure the extensor tendons. This can make it difficult to straighten your fingers
  • Trigger finger[10]
    • No passive movement possible
  • Posterior interosseus nerve (PIN) syndrome[10]
    • Patient unable to extend actively, but tenodesis remain normal

Diagnostic Procedures

  • Radiographs are recommended because associated injuries of surrounding structures are common. For example, it can be that a piece of bone is pulled off with the tendon[7]. X-rays may rule out or confirm associated bone injuries.[9]
  • Ultrasound - high resolution ultrasound is considered to be reliable and useful diagnostic tool in the detection of tendon injuries[15]
  • MRI has high diagnostic value to assess tendon injuries of the hand and may be helpful in the diagnosis of extensor tendon injuries[16]
  • Clinical tests[17]
    • Extensor Digitorum Communis (EDC):
      • hand in hook position, with PIP and DIP joints flexed, ask patient to actively extend the MCP joints
    • Extensor Pollicis Longus (EPL):
      • patient rests hand on the table and lift thumb of the table. If EPL laceration- significant smaller movement and won’t be able to extend their IP joint of the thumb

Outcome Measures

  • Disability of Arm, Shoulder, and Hand questionnaire (DASH)
  • Quick DASH –This outcome measure is a shortened version of the DASH and is used to determine the patient’s physical function and symptoms[18]
  • Gartland and Werley Score – This is one of the most widely used outcome measures used in the clinic to evaluate wrist and hand function.
  • Sollerman Hand Function Test(SHFT)[18]

Medical Management

Patients with an extensor tendon injury can be treated in two ways, surgically or conservatively (namely splinting). The choice of treatment depends on the degree of the injury. In general, open injuries and entire ruptures demand surgical treatment. Closed injuries and partial lacerated tendons require splinting,[19]

General Principles

Factors that should be considered when deciding the appropriate treatment include[10]:

  • the characteristics of the extensor tendon injury
  • mechanism of injury/trauma
  • injury site
  • involvement of soft tissue and/or nerve and vascular bundles
  • patient characteristics, such as age, work, comorbidities and functional requests

Surgery

  • Preferably same day surgery
  • The greater the number of tissues involved - the more challenging to restore hand function[20]
  • Primary repair
  • Tendon transfer (for example extensor indices transfer to EPL) is an option in cases where[17]:
    • There is a delay between the time of injury and time of surgery
    • The tendon is too frayed
    • The tendon is too short
  • Preserving and restoring appropriate tendon length is important to the outcome of the repair - even minor changes in tendon tension can have negative effects on finger movement[13]
  • Miller's criteria is used to evaluate extensor tendon injury. Factors that are all important to the outcome of the repair are[21]:
    • severity of laceration
    • injury zone
    • surgical technique used for repair
    • other trauma to surrounding tissues
    • hand therapy
    • patient compliance

Physiotherapy Management

The physiotherapist’s task is to improve the functionality of the hand, with the intention of achieving the pre-injury condition. This will be done by gradually enlarging the range of motion. For the best possible outcome, it is necessary adapting the rehabilitation program to the individual.[5]

Examination

Examination of extensor tendon injuries contains different points of interest. First, the wound characteristics should be evaluated such as size and location to give the physical therapist an idea of which structures may have been damaged. Next, the function of the fingers and wrist will be tested in three ways: passively, actively and then with resistance. It is important that each finger is tested separately because the juncturae tendinum between the communis tendons can mask a dysfunction. Furthermore, complete neurovascular examinations should be done.

Post-Surgical Physiotherapy Management

It is important to see patients as soon as one to five days postoperatively for the best possible outcome.[17]

Wound care and Scar Management

  • Provide wound care – keep the wound dry and clean and monitor the wound for signs of infection[17]
  • Commence scar management early to prevent adhesions[17]
    • Extensor tendons lie superficially and a scar on the dorsum of the hand may adhere quite quickly and this can restrict flexion range of motion in the fingers.
    • Massage the scar and aim to keep the skin on the dorsum of the hand as mobile as possible

Oedema control

  • Control swelling of the hand[22]
  • Patient should keep hand elevated to reduce and prevent swelling[22]
  • Performing the active range of motion exercises prescribed within the provided protocol will also control swelling[22]
  • Compression can be applied where needed to control swelling[17]

Orthosis

Examples of extensor tendon repair splints[23]

The therapist also provides the patient with the specified splint or orthosis as well as the exercises relative to the rehabilitation protocol provided by the surgeon or therapist[17]

Considerations in designing an appropriate orthosis include[24]:

  • joint position
  • external load
  • resistance to tendon glide, as determined by friction and adhesions

Patient Education

Patient education is an important part of the postoperative management of extensor tendon injuries. It is important for patients to know the following[17]:

  • To keep the wound dry and clean
  • To keep the splint in place 24/7
  • To perform their exercises with their splint on, unless the therapist advised them differently
  • If the splint is taken of the patient must keep their hand and forearm in the safe position to keep the tendons on no stretch. This position is the forearm in supination and the fingers relaxed. It is very important for patients to be aware of this and follow this recommendation as this will reduce the risk of tendon rupture or the extensor tendons EPL and EDC from overstretching, if they are ever out of the splint.

Rehabilitation Protocols

Extensor Digitorum Communis (EDC)

Merrit Protocol
  • Most popular protocol to treat zone V extensor tendon injuries[6]
  • Good outcomes achieved with this protocol and patients feel that they have some freedom as fingers are not immobilised[18]
  • Allows patients to use hand for very light functional activities throughout the course of rehabilitation
  • Only appropriate for use in extensor tendon injuries to the EDC in zones V to VII (from MCP joints to wrist) and only if patient has lacerated one to three tendons and had tendon repair.[25]
  • Due to the nature of the splint – this protocol cannot be used for more than three lacerated tendons[17]
  • Image of RME plus orthosis/ EAM approach[26]
    Splint:
    • Splint consists of two pieces:
      • The volar wrist splint – wrist in 20°-30° of extension[25]
      • Second component is a relative motion splint for the fingers – which positions the affected finger in slight MCP extension relative to the unaffected fingers. This allows the patient to flex the MCP joints and assists with tendon glide to prevent adhesions[25]
Merrit Protocol Exercises[17]
  • Hook fist
    All exercises are performed with the splint on
  • Composite flexion
    Exercises are done 5 times a day and 10 repetitions of each exercise
  • Exercises:
    • Active MCP flexion
    • Hook fist
    • Composite flexion
    • Active finger extension
  • The patient does these exercises with the wrist splint and the relative motion splint on
  • Patient continues with these exercises for the duration of splinting – usually about 6 weeks
  • It is also important to ensure that the PIP joint is maintaining full extension within the splint.
  • If a patient has an extension lag of the PIP joint – it might be useful to put the affected finger in a finger trough or finger extension splint at night
  • If more than one finger is involved and with a lag, a resting splint may be a good option for the patient to wear at night
  • The resting splint should keep the wrist in slight extension, MCP’s in 20 – 30 degrees of flexion and the PIP and DIP joints in neutral.
  • At four weeks post-operatively the wrist splint is taken of and ceased.
  • The relative motion finger component is continued until 6 weeks postoperatively
  • At 6 weeks postoperatively all splints are stopped
  • Patient is encouraged to use hand for light functional use and full range of motion
  • Passive stretching commences at 7 weeks postoperatively
  • Strengthening commences at around 8 weeks postoperatively
The videos below demonstrate examples of active MCP flexion and active finger extension. Keep in mind that these exercises are done in the splints for the first six weeks (4 weeks with volar wrist splint and thereafter with relative motion finger splint)
Norwich Protocol[17]
  • High reported usage of this protocol as well[6]
  • Often used in patients that are less reliable[29]
  • If patient has had two or more tendons repaired
  • Surgical repair not as strong as what it could be
  • Used in patients with tendon lacerations of zones V – VII
  • Patient is initially seen on days one to four postoperatively
  • Resting Hand Orthosis[30]
    Therapist fabricates a volar splint with:
    • the wrist in 45 degrees extension
    • MCP’s flexed to 50 degrees
    • IP joints extended
  • This is a tricky position to splint – but the IP joint extension is important to prevent any extension lags
  • Fabricate the splint with the patient’s forearm in supination – as this will allow the therapist to drape and mould the thermoplastic well over the hand to ensure a good wrist- extended position
Exercises in Norwich Protocol
  • Resting splint is worn 24/7[31]
  • Exercises are performed with the splint on
  • Exercise frequency: 10 repetitions of each exercise, 5 times a day.
  • Hook fist in splint[32]
    Exercises[31]
    • Combined IP and MCP joint extension of the splint
    • Hook fist with splint in place
  • Patient continues with these exercises for 6 weeks, until patient is weaned from the splint
  • If there is no evident extension lag after 6 weeks, the patient can stop wearing the splint at 6 weeks
  • Patient is encouraged to use the hand for unlimited use
  • Grip strengthening is commenced at 7 weeks
  • At 8 weeks postoperatively, full passive flexion stretches can be commenced if full finger flexion has not yet been regained
  • A dynamic flexion splint may be considered at 12 weeks if it required to regain flexion
  • Should there be an extension lag greater than 30 degrees – the patient needs to continue wearing the splint until 8 weeks postoperatively.[17]

Extensor Pollicis Longus

  • Volar thermoplastic splint for EPL tendon repair[33]
    Splint used[17]:
    • Volar Thermoplastic splint with the wrist in slight extension and thumb held in extension as well
    • Splint comes to below the MCP joints, just through the distal palmar crease of the hand and up to two thirds of the forearm
    • Splint also comes up to the tip of the thumb – because the EPL tendon inserts at the base of the distal phalanx and the distal phalanx should not be flexing freely
Exercises
  • Thumb extension with splint on[34]
    Early active range of motion exercises should be started from the first appointment[17]
  • Isolated IP and MCP joint flexion in splint[35]
    With the splint on – the patient performs active extension
  • With the splint on, but the thumb strap released, with the wrist in extension, isolated IP joint flexion can be performed, as well as isolated MCP joint flexion.
  • Only exercise that patient may perform with splint of is gradual opposition of the thumb, BUT these exercises must be performed with the forearm in supination
  • Gradual opposition of the thumb to each fingertip is performed, with progression to a different finger tip each week. Week 1 – oppose the thumb to index finger. Week 2 – oppose the thumb to the middle finger, Week 3 – oppose the thumb to the ring finger, etc. Until patient is able to flex the the thumb down to the proximal crease over the MCP joint of the little finger by week 6
  • Exercises remain the same until 6 weeks postoperatively
  • After 6 weeks the patient can be weaned out of the splint
  • Encourage patient to use hand for full range of motion and light functional activities
  • Strengthening exercises are commenced at 8 weeks postoperatively if surgeon gives clearance
  • Strengthening exercises include using Theraputty for finger extension exercises – make a little doughnut shape out of Theraputty, place around the fingers and then actively extend the fingers.
  • Another example is using the Theraputty for finger flexion exercises into a full fist – as patients often lost grip strength as a result of the period of immobilisation[17]

Red Flags in Extensor Tendon Injuries

Red flag photo.jpg
Red flags that therapists need to be aware of and look out for in patients with extensor tendon repairs in EDC zones V - VII and EPL zones II - VIII include[17]:
  1. Ruptures
    • This is always a concern with tendon repairs
    • If a patient has ruptured the EPL – unable to extend the IP joint
    • EDC rupture – unable to extend MCP joints when isolate
    • Look out for ruptures during the first 6 weeks postoperatively, but especially within the first 3 weeks postoperatively
  2. Extensor Lags
    • Extensor lags are often difficult to correct once it has developed, so it is key to identify a lag as soon as possible. In a patient with a lacerated ECD tendon and using the Merrit Protocol, who is unable to actively extend the affected finger at the PIP joint -  a volar extension splint at night or for resting is recommended.
    • If more than one finger is involved with an extensive lag at the PIP joint – a night resting splint should be considered.
  3. Infection
    • Look out for any redness, pain, oozing, odorous smells around the wound site.
    • Flag any signs of infection with the surgeon.

Key Messages to Remember

  1. Know your Anatomy
    • This will inform treatment approach and inform your clinical reasoning. Know which tendon was lacerated and in what zone as the treatment protocols for the various zones differ.
  2. Know the patient’s history
    • This will influence your treatment of the patient. Was the tendon cleanly cut? Was the surgery performed immediately or was there a delay? Is the patient reliable and can the therapist trust the patient to perform their exercises according to the protocol provided to them. Is the patient educated about the injury  and will the patient be compliant.
    • It is important to come up with an appropriate treatment protocol in conjunction with the surgeon to best treat the individual patient.
  3. Be confident in your splinting skills
    • Practice before you fabricate a splint for the first time, especially with the relative motion splint in the Merrit Protocol.
    • Be familiar with the degrees of the angles of the different joints that you need to place them in.
  4. Monitor patient progress
    • Monitor patient progress closely and check the tendon status and look out for extension lags
  5. Know your rehabilitation protocol
    • Be familiar with the selected protocol.
    • Educate your patient and be a good teacher.
    • Give them the confidence to manage their injury and a good outcome will be achieved.

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