Hand Extensor Tendon Lacerations are the most common injuries due to road traffic accidents, trauma, injury, gunshot wound, sports injury, athletic performance. If appropriate treatment is not done your hand may go to permanent damage may result in a lasting impairment of hand function.[rx] Due to their superficial location of the injury and being adjacent to the bones, extensor tendons in the hand are more prone or edge place to injury than the flexors function of the hand.[rx][rx]
Causes of Extensor Tendon Lacerations
The most common causes are following
- Extensor tendon lacerations are very common injuries among young manual workers due to road traffic accidents, trauma, injury, gunshot wound, sports injury, athletic performance[rx]
- Laceration caused by a sharp object is the most common mechanism followed by the saw, and blade injuries, both having a slightly different distribution anatomically.
- A saw is most commonly causing injury distal to the metacarpophalangeal joint (MCPJ) and be associated with fractures, while sharp object lacerations tend to be proximal to that.[rx]
- Accidental injuries in younger children are seen sometimes involving flexor and extensor compartment injuries, while much more rarely they can happen in neonates, or children as a result of iatrogenic injury during delivery – particularly during C-sections.[rx]
Diagnosis of Extensor Tendon Lacerations
History and Physical
An accurate assessment is essential as it has a direct impact on the livelihood and work of affected individuals.[rx] A detailed medical history is crucial and must include the mechanism of injury, time, the position of the hand and fingers at the time, age, occupation, and handedness, previous injury. Any abnormal human bite, depth was involved is vital as any contamination would need formal irrigation and debridement.[rx]
Both a systemic and an in-depth examination of both hands is critical, comparing like for like.[rx] Unless the injury is part of a larger trauma, and the patient needs to be treated according to the ATLS treatment system protocol, hand examination should start with an inspection. Any open wound to the back of the hand should raise suspicion of extensor tendon injury. The neurovascular system should always be tested and documented before any local anesthetic is given.[rx]
Once that is done, open injuries should be explored with care under local anesthetic and with appropriate magnification.[rx] Additional injuries with associate muscle must be sought.[rx] Any suspicious things of deep injury warrant a referral to the hand surgery team.[rx]
If the radial nerve innervates all extrinsic extensor tendons of the hand clinician should look out for radial nerve injury but not forget also to assess median and ulnar nerves.[rx] Extrinsic tendons can be divided into superficial and deep groups as shown below:[rx]
Superficial extrinsic extensors
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Extensor carpi radialis longus (ECRL)
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Extensor carpi radialis brevis (ECRB)
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Extensor digitorum communis, (EDC)
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Extensor digiti minimi (EDM)
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Extensor carpi ulnaris (ECU)
Deep extrinsic extensors
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Abductor pollicis longus (APL)
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Extensor pollicis longus (EPL)
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Extensor indicis proprius (EIP)
The above can be grossly tested manually even in the case where the patient is unable or unwilling to cooperate by checking for normal tenodesis and digital cascade.[rx]
At the level of the wrist, they are divided into six compartments numbered from radial to ulnar side.[rx] Fibroosseous sheaths separate them, and the extensor retinaculum acts as a roof over the muscle to prevent bowstringing. Within the compartments, the tendons are round, but they flatten the more distal position they run.[rx] Loss of normal digital system with extension lag of any single digit should prompt assessment of all six components of the extensor compartment:[rx]
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Compartment 1 – APL and extensor pollicis brevis (EPB)
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Compartment 2 – ECRL and ECRB
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Compartment 3 – EPL
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Compartment 4 – EDC and EIP
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Compartment 5 – EDM
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Compartment 6 – ECU
In addition to the above divisions, extensor tendons have been classified into a zone system by Kleinert and Verdana. They have described 8 zones relating to undergoes bones and joints. Doyle has later added on an additional 9 zone system in the musculotendinous junction in the forearm, which is about 4 cm proximal side to the wrist.[rx][rx] All can be seen in figure 2 which shows the odd number zones are over the joints broadly. Each zone differs in anatomy and properties of the extensor mechanism; therefore, all need to be assessed, and any treatment of a laceration will depend largely on its location.[rx]
Extension in each finger needs to be tested on a joint by a joint basis in isolation, looking at the active range of movement and movement against resistance. Some special considerations need to be taken depending on the zone affected by the injury as per their specialized anatomy and in cases where there is more than one tendon per digit (both EDM and EIP can be tested by extending the relevant finger with the hand flat on a surface). It is worth noting that the full extension of small joints is occasionally possible even after those tendons have been lacerated.[rx]
Evaluation
After the initial assessment is performed, further evaluation should take place that is radiographs must be taken to assess if there are any associated fractures of bone tissue. Glass and some other foreign bodies may also be discovered that way.[rx] Anteroposterior, true lateral, and oblique views x-ray should be taken of both the affected area and the neighboring joints.[rx]
Complex injuries such as those associated with significant tissue compromise (be that bone or soft tissue) may require reconstruction well beyond simple tendon repair. [rx]:
- 1) Restore reliable vascular supply
- 2) Stabilize the wound bed (debridement)
- 3) Reestablish skeletal stability.
Once the above is fulfilled, the tendons themselves may be examined for reconstruction as well as any potential requirement for graft coverage or fascial flaps may be considered.[rx]
Treatment of Extensor Tendon Lacerations
GENERAL PRINCIPLES
There is not a clear specific standard for the treatment of extensor tendon lacerations.[rx] The important thing the term ‘laceration injury’ can be used quite widely and can hide more complex injuries associated with the laceration itself.[rx] Tetanus prophylaxis should be considered, and antibiotics are commonly used medicine to heal soft tissue.[rx] Repair should take place soon after the laceration and certainly about two weeks from the injury (ideally within a week).[rx] [rx]
Tendon injury repair may include primary repair, secondary repair, immediate reconstruction with a tendon graft, staged tendon reconstruction, and tendon transfer. The greater the number of tissues involved in the injury, the more challenging it is to restore the hand function.[rx]
Preserving or restoring appropriate tendon length is crucial to the outcome of repair, as even seemingly minor changes in tension can have a detrimental effect on finger movement.[rx] Despite easy surgical access and the results being generally better than in flexor tendon injuries, it remains a challenge to maintain that correct length and normal function in extensors.[rx]
Miller’s criteria are used to evaluate extensor tendon injuries, and they have shown that laceration severity, the zone of injury, surgical technique used for repair, accompanying trauma to surrounding tissues, hand therapy, and patient compliance are all important to the outcome.[rx]
Surgery is indicated if[rx]:
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more than 25% of the tendon has been cut
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the patient is unable to extend the digit
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there is associated contamination requiring a formal washout and debridement
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the joint is unstable
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conservative approach trial has failed
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the patient can comply with the postoperative protocol.
The procedure can be performed under a local anesthetic or a nerve block, with the patient in a lye supine position and the arm at their side on an arm table. A pneumatic tourniquet is very useful to control bleeding intraoperative time. Because of varying morphology depending on the zone of injury, treatment is best treatment planned by anatomic classification.[rx]
Proximal zones (VI to IX) can take a 3-0 suture, but the size needs to be reduced the more distal the injury.[rx] The more distal repairs are less complicated in repair technique but are still more difficult to operate on because of their smaller size and lack of proper collagen bundle linkage. This means that there is little griping strength for the suture material. Equally, they are very flat distally to MCPJ, which means they cannot take a core suture and have the largest surface area between the defect and surrounding tissues making them more prone to adhesions.[rx][rx]
Contaminated wounds may need to be washed out of the hand and left to repair at a later date when the wound bed is clean. If the cut is clear and both ends are seen, they can be repaired in an emergency department. Alternatively, the skin may be loosely closed over the lacerated tendons area as a temporary measure if a surgical repair is required in theatre. Extensor tendon injuries should be managed in hand extension splinting to avoid exacerbating the injury and tendon end separation.[rx]
Partial injuries can be managed with wound care and splinting, but complete injuries require a primary repair treatment. If not immediately possible patients may be patient for delayed treatment, two-stage reconstruction, tendon transfer, or graft, but these may result in subpar outcomes often that is due to stiffness and reduced range of motion (ROM). This is seen in both adult and pediatric populations, and it is much more pronounced in the former.[rx]
If immobilization in children is difficult due to small digit size, a K wire fixation technique may be considered. Alternatively, an alumifoam splint also can be incorporated into the cast.[rx]
ZONE 1
Zone 1 lacerations are in distal to DIPJ and can be referred to as open mallet finger disease.[rx] They can be treated using the dermatotenodesis process – full-thickness single layer closure of the skin and the underlying tendon.[rx] If there is no underlying bony injury, these can be treated in the emergency as long as the wound and joint can be thoroughly irrigated.[rx] The patient must continue to move PIPJ to avoid stiffness in-home, and they must be warned that they may never regain a full DIPJ flexion as well as may have some extensor lag, even with a well-done repair.[rx]
ZONE 2
Zone two injuries are overlaying middle phalanx. Injuries of the tendon should be repaired.[rx] Injuries involving less than 50% of the tendon may be treated with 1 to 2 weeks of splinting provided there is no associated lag, and the DIPJ can be extended against hand resistance. Occasionally these are associated with soft tissue loss and need more complex reconstruction.[rx]. Just like in zone 1, the results can be poor in zone 2 – less normal movement is present there, and shortening can impact the rang of motion in the interphalangeal joints (IPJ).[rx]
ZONE 3
A zone three laceration is over the PIPJ and often boutonniere deformity. Absent or weak PIPJ extension finger is a positive finding. It can be either reconstructed directly, or a tendon flap can be raised from the proximal part of it.[rx] These injuries are often associated with traumatic arthrotomy of the PIPJ or bony injury, thoroughly explored and managed accordingly.[rx] If a primary repair cannot be achieved, a turndown technique system can be used, or the lateral bands can be sutured together to make up for the lack of central slip.[rx]
ZONE 4
The injuries are over the proximal phalanx, which usually involves the broad extensor mechanism.[rx] Because of this broadness, they are often partial injuries.[rx] Partial lacerations have been shown to have good results with splinting only for 3 to 4 weeks; however, complete lacerations require an operation.[rx] The methods used include modified Kessler, modified Bunnel, and modified Becker. Similar to zone 2 injuries, these can be associated with soft tissue injuries and defects, necessitating more complex methods.[rx]
ZONE 5
These are over the MCPJ and must be assumed to be human bites until proven. They ought to be repaired, and care must be taken to ensure sagittal bands are intact or repaired to ensure central tendon position and good clinical output. If there is a bite involved, the wound must be extended, washed out, left open, and the patient should be started on antibiotics treatment after the cultures have been sent off from the theatre.[rx] Traumatic arthrotomies surgery is common, and because these injuries often happen while the MCPJ is in a flexed position, the resulting injury can be more proximal than participated making the repair more difficult due to the proximal portion of the tendon retracting position.[rx] Postoperatively splinting is done with the wrist in 30-45 extension and MCPJ in 20 to 30 flexion. PIPJ and DIPJ are left free.[rx]
ZONE 6
This area covers the dorsum part of the hand over the metacarpals. There may not necessarily be a loss of finger extension at MCPJ in these injuries because of the presence of the junctures, even if the laceration may involve the whole tendon. This makes diagnosis more difficult to find if not explored.[rx]. Tendons are becoming larger here and may need a core suture as well as a peripheral repair.[rx] The methods that can be used include running-interlocking horizontal mattress, augmented Becker, Halsted, or Silfverskiold.[rx] More complex degloving injuries may require a grafting flap.[rx]
ZONE 7
These injuries happen below the extensor retinaculum, and it is unclear if releasing it to visualize the damage and repair it is necessary, and any other way to repair the damage.[rx] The repair of tendons here can increase the number of small results because of injury to the extensor compartments or a bowstring types effect if the retinaculum is not repaired properly.[rx] It may also result in adhesions, particularly if splinted statically.[rx] If repaired too tightly, it can also impair tendon gliding types movement. What follows from both is a loss of motion or range of motion. Additionally, repair itself may impact that, especially if too bulky and the retinaculum can also be lengthened using step-cut or Z-plasty to prevent that. Early mobilization should be measured, so repair must be strong enough to cope with it.[rx]
ZONE 8
This zone lies between the distal forearm part, and lacerations are likely to involve more than just one tendon, as well as muscle fiber and musculotendinous junction. Repair should start with the thumb joint strictly and wrist extensor and move from there.[rx] The repair is more likely to be difficult as the tissues are weak. The repair can be done by using eight sutures. Care should be taken to examine the posterior interosseous nerve junction(PIN) and protect it intraoperatively. Both wrist and elbow splinting may need to be considered to protect the repair postoperatively.[rx]
THUMB
Mallet is less likely here as the tendon is broader, but if it occurs, it should be repaired.[rx] It is often robust enough to take a dedicated tendon suture, but a dermatotenodesis system is also an option.[rx] EPB may be lacerated with no functional problem, and the need for its repair is debatable, but EPL affects both IPJ and MCPJ in the thumb and requires reconstruction if lacerated injury occurs.[rx] T4 and T5 zones may involve superficial radial nerve, and large branches may need repair (while smaller ones may need to be buried to avoid neuromas). Anything more proximal to this may be treated as zone 8 and 9 injuries.[rx]
Differential Diagnosis
The term laceration implies the mechanism of injury may present with a similar clinical picture of a deficit in the extensor mechanism function:
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Mallet finger (avulsion of the extensor tendon insertion from the distal phalanx, without the involvement of a bony fragment)
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Arthritis (chronic irritation to the tendon may result in damage to the extensor mechanism causing a classical deformity like a boutonniere, swan neck or a simple tendon rupture near the joint with affected)
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Trigger finger (will result in loss of passive extension as well as active movement)
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Posterior interosseous nerve (PIN) syndrome (patient will be unable to extend actively, but tenodesis will remain normal)
Treatment Planning
Given that there is more than one way to manage these types of injuries, care must be taken when planning your treatment and adjustments have to made depending on several factors including anatomical location, concomitant injuries, and patient compliance, for example in case of young children.[rx]
Complications
Complications include:
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tendon rupture[rx]
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reduction in both active and passive ROM[rx]
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adhesions[rx]
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extension lag (especially in MCPJ)[rx]
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loss of flexion and reduced ability to grip[rx]
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finger deformities[rx]
The adhesions are the most common of the above and can result in a loss of flexion.[rx][\rx] Loss of flexion is a larger problem than extensor lag, especially in zones 3 and 4, as it has a higher effect on grip.[rx] When adhesions happen, additional treatments are required, including intense hand therapy, and sometimes re-operation may be required (rates of tenolysis is anywhere between 0 and 17%).[rx] To compare repair rupture rates are estimated to be between 0 and 8%.[rx]
Extensor tendon laceration outcomes can be measured using Miller’s criteria which divide them in to excellent (extension lag, 0 flexion loss), good (less than 10 extension lag, less than 20 flexion loss), fair (11 to 45 extension lag, 21 to 45 flexion loss) and poor (greater than 45 extension lag, greater than 45 flexion loss). Notably, all of the above is measured purely on the extent of complications.[rx]
Postoperative and Rehabilitation Care
Postoperative rehabilitation minimizes tendon gapping while reducing the probabilities of adhesions at an equivalent time.[rx] Three main approaches are available when it involves postoperative care of extensor tendon lacerations – immobilization, early passive motion (EPM), and early active motion (EAM).[rx]
Traditionally extensor tendon lacerations are splinted statically for 4 to six weeks, which frequently resulted in a loss of flexion thanks to adhesion formation.[rx] Immobilization is most appropriate during a non-compliant patient but comes at the price of the very best complication rates.[rx] Only 64% of patients treated this manner had good to excellent results, and they have reported an above-average loss of flexion.[rx] this will be somewhat offset by reducing the length of the immobilization period.[rx] Children should be immobilized statically because it doesn’t believe in patient cooperation, and youngsters don’t suffer from adhesions, contractures, bowstringing, and tenodesis the maximum amount as adults do. Most of the pediatric complications reported postoperative relate to wreck at the repair site instead of immobility.[rx]
Studies of dynamic and static splinting have shown that the previous leads to much-improved outcomes within the context of extensor tendon injuries.[rx] However, some EPM splints are expensive and inconvenient to wear. They also require a motivated patient.[rx] Generally, EAM is inspired post-op at the present – this protocol seems to be less expensive and have a lower rate of complications than the opposite two protocols in extensor zones 3 to six .[rx]
There are now splinting methods that permit a degree of movement – only enough to stop stiffness, but not such a lot that it ruptures the repair. Relative motion splint (RM) may be a compact splint where the injured tendon is placed during a 15 to twenty degree less relative motion than adjacent tendons from a standard muscle. this suggests its particularly applicable in extensor tendons in zones IV to VII.[rx] Early protected motion causes a recovery in 90% of patients altogether thumb zones and finger ones 3 to 7, even in patients with suboptimal compliance.[rx]
