Mallet Finger Injury
What is a mallet finger injury?
A mallet finger is an injury to the terminal extensor tendon that straightens the end (distal interphalangeal or DIP) joint of the finger. When the tendon attachment is injured, the end joint of the finger droops.
Mallet finger injury may be caused by a tear (rupture) of the terminal extensor tendon or by the tendon being pulled away with a piece of the bone (avulsion).
What causes mallet finger injuries?
In older patients a mallet finger can occur from a very mild injury to the fingertip such as jamming the finger while making the bed. In older patients, a tendon rupture is more likely than a fracture.
In younger patients there is usually a fracture of the bone where the extensor tendon remains attached to bone and pulls away (avulses) part of the distal phalanx bone. The injury often occurs during ball sports when the ball hits the fingertip and suddenly forces the fingertip into a bent (flexed) position.
What are the signs & symptoms?
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The DIP joint of the finger is swollen.
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The fingertip will droop.
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It is not possible to straighten the finger without using the opposite hand.
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Younger patients will usually be aware of mild pain and recall an injury.
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Older patients may have no pain, minimal swelling and not notice that their finger has been injured until some time later when it starts to droop
How are mallet finger injuries diagnosed?
An x-ray should ALWAYS be performed to determine whether there is a fracture as this will guide treatment. Ultrasound is not required as a history and examination will clarify if there has been a tendon injury.
There are 3 main types of mallet finger injury:
1. Soft tissue mallet injury - tendon rupture, x-ray normal
2. Small avulsion fracture
3. Large avulsion fracture involving more than > 30%
Type 1 and 2 can be treated with splinting. Type 3 has a high risk of the joint being unstable and subluxing (partly dislocating) which will result in permanent deformity, a stiff joint and arthritis. Type 3 require surgery.
Which mallet finger injuries are treated non-operatively?
1. Soft tissue mallet injury
Soft tissue mallet injuries are tendon (soft tissue not bone) ruptures and take 8 weeks to heal.
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A custom-made splint with the joint in hyper-extension is applied. This brings the ends of the tendon as close together as possible.
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The splint must be worn continuously (24/7) for 8 weeks for the tendon to heal.
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The treatment should commence in the first week if possible - any form of temporary splinting should be applied and hand therapist contacted ASAP.
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Removal of the splint too early will result in stretching of the healing tendon and a permanent deformity of the finger.
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Nearly all activities of daily living can be performed with the splint, including contact sport.
2. Small avulsion fracture
Small bony (versus soft tissue) mallet injuries take 6 weeks to heal. Bone heals faster than tendon.
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A custom-made splint with the joint in neutral position is applied. Hyper-extension of the splint can lead to joint subluxation in some patients.
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The splint must be worn continuously (24/7) for 6weeks for the fracture to heal.
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The treatment should commence in the first week if possible - any form of temporary splinting should be applied and hand therapist contacted ASAP.
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Removal of the splint too early will result in failure of the fracture to heal in a good position and a permanent deformity of the finger.
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Nearly all activities of daily living can be performed with the splint, including contact sport.
Important
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Nearly all activities of daily living can be performed with the splint, including contact sport.
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The splint must be kept dry to avoid skin maceration and infection.
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The hand therapist will show you how to safely change your splint once a week to clean the skin without allowing the finger to bend.
Surgical Treatment
3. Large Avulsion Fractures involving >30% of the joint surface
If the fracture involves more than 1/3 of the joint lining, there is a high risk that the joint will sublux (partly dislocate) if only splinting is used. In this situation, surgery is indicated. The bone fragments are usually too small for screws.
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This is a day surgery procedure under general anaesthetic.
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The technique uses a temporary wire and a suture that wraps around the bone fragment and holds it in place.
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It is performed via a small “H”-shaped incision on the back of the finger.
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The joint is placed in its normal position and a wire is passed across the joint with x-ray guidance to prevent subluxation until the bone heals.
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A strong suture is passed around the bone fragment using long straight needles and tied over padding on the finger pulp to pull the bone with attached tendon back into position.
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A long-acting nerve block should keep the finger numb and painfree for 6-8 hours.
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A temporary half cast is applied and a sling and post-operative pain relief is prescribed.
Risks of Surgery
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Nailbed injury - extremely rare.
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Infection < 1%
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Accidental pin removal -best avoided by leaving all dressings to the hand therapist.
Recovery
The finger must be kept dry for 6 weeks.
No contact sport is allowed for 6 weeks, and a splint must be worn for contact sport until 10 weeks post op.
2 days The bandage is made smaller, and a light splint is applied.
2 weeks The stitches are removed.
4 weeks The padding on the finger pulp and the suture holding the fracture in place are removed. The splint will be remodelled to a lower profile.
6 weeks An x-ray is performed, and the wire removed (in office).
10 weeks Protect finger for at risk activities until 10 weeks post=op. Return to all normal activities.