Mallet finger is the term applied to extensor avulsion fractures or distal extensor tendon ruptures. Either one results in an inability to extend the DIP joint.
Mallet finger injuries
- Named for the resulting flexion deformity of the fingertip, which resembles a mallet or hammer.
- Caused by the disruption of the extensor mechanism of the phalanx at the level of the distal interphalangeal joint usually due to a forced flexion at the distal interphalangeal joint.
- Results in the inability to extend the distal phalanx.
- Cause a mallet fracture when the extensor tendon also causes an avulsion of the distal phalanx.
Mallet finger injuries are best managed by a multidisciplinary team because the ideal treatment is not known.
- Conservative treatment with splints is widely used for mild injuries (outcomes are unpredictable).
- Surgery is often done (results are not optimal).
Clinically Relevant Anatomy
The extensor tendons straighten the fingers and thumb through a very complex arrangement. The extensor apparatus is a plexus of tendons with an aponeurotic sheet. 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.
In Mallet finger the distal extensor tendon is ruptured. The rupture occurs when the distal phalanx of a finger is forced into flexion while being actively extended e.g. hit by a ball being caught.
- The extrinsic extensor tendon originates in the forearm and runs over the metacarpophalangeal joint, having an indirect attachment to the proximal phalanx, and finally, attaches to the distal phalanx. These tendons are responsible for extension of the digits.
- A mallet finger injury occurs when the extensor tendon is disrupted. A mallet fracture occurs when the tendon injury causes an avulsion fracture of the distal phalanx.
- Current evidence supports nonoperative interventions, but injuries need to be addressed in a timely manner in order to avoid poor outcomes.
Mallet finger injuries usually occur: 
- In the workplace or during sports-related activities.
- Frequently seen in young to middle-aged men and occasionally in older women as well.
- There is a predisposition to these injuries during participation in ball sports, as the ball hits the fingertip of an extended finger. This compels the distal interphalangeal joint into a forced flexion position and thereby causes an extensor tendon disruption.
- Most often involve; long finger; ring finger or the little finger of the dominant hand.
- An inciting incident will be reported if a traumatic cause.
- Initially, the finger is painful and swollen around the DIP joint.
- When the actual tendon is ruptured, the condition can be relatively painless. If a piece of the bone is pulled off, it is normally a bit more swollen and sore.
- The end of the finger is bent and cannot be straightened voluntarily. The DIP joint can be straightened easily with help from the other hand.
- Usually the diagnosis of mallet finger is clearly evident from the physical exam.
- An X-ray may be taken - may will show if the injury is an avulsion fracture or a tendon rupture and/or if there is a fractured bone.
Physical Therapy Treatment
In general a splint will be worn full time for 6–8 weeks. Then exercises can commence to gradually increase the movement in the tip of the finger. At this time gradually reduce the time client is wearing splint. It usually takes around 3–4 weeks to regain maximal movement and strength of the finger post immobilisation.
Non Surgical 
May have continuous splinting for approximately six weeks followed by six weeks of nighttime splinting.
- Usually this will result in satisfactory healing and allow the finger to extend.
- The key is continuous splinting for the first six weeks.
- If the splint is removed and the finger is allowed to bend, the process is disrupted and must start all over again.
- The splint must remain on at all times, even in the shower.
- The splint should holds the DIP joint in full extension and allows the ends of the tendon to move as close together as possible. As healing occurs, scar formation repairs the tendon.
- When the tendon is strong enough to hold the fingertip straight, a schedule to gradually wean out of the splint safely is instituted. If client resumes playing sport with your splint on, you need to educate to strap it on firmly with sports tape to make sure it doesn't fly off.
Splinting - many splints that have been designed to make it easier to wear at all times. In some extreme cases where the patient has to use the hands to continue working (eg a surgeon), a metal pin can be placed inside the bone across the DIP joint to act as an internal splint allowing the patient to continue to use the hand. The pin is removed at six weeks.
- In chronic mallet finger cases splinting may still work. In this case, splint the finger for about eight to 12 weeks to see if the drooping lessens to a tolerable amount before considering surgery.
- Skin problems with prolonged splint usage include skin breakdown monitor and possibly recommend new or different splint.
- Nearby joints may be stiff after keeping the finger splinted for this length of time. Design a program of exercises to assist in finger range of motion and to reduce joint stiffness.
This useful video shows how to tape a mallet finger after splint removal (less than 2 minutes)
- Surgery to repair a mallet finger is required when the bone fragment is large, when the fingertip has moved position a little or when the cause is a laceration.
- Rehabilitation after surgery for mallet finger focuses mainly on keeping the other joints mobile and preventing stiffness from disuse.
Either of these complications can occur following either nonsurgical or surgical management of mallet fractures.
- Residual extensor lag (noted on physical exam)
- Swan neck deformities (due to a disruption of the volar plate caused by the disrupted extensor tendon, resulting in the distal interphalangeal joint becoming abnormally flexed and the proximal interphalangeal joint remaining in a hyperextended position).
- Yee J, Waseem M. Mallet Finger Injuries. InStatPearls [Internet] 2019 May 5. StatPearls Publishing. Available from: https://www.ncbi.nlm.nih.gov/books/NBK459373/ (last accessed 7.12.2019)
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- Ramponi, Denise R et al Advanced emergency Nursing July/September 2019 - Volume 41 - Issue 3 - p 198–203 AVAILABLE FROM: https://journals.lww.com/aenjournal/Abstract/2019/07000/Mallet_Finger.3.aspx (last accessed 8.12.2019)
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- Performance Health Academy Network Spinting:Mallet Available from:https://www.youtube.com/watch?v=-PI53P9qD6I (last accessed 5.4.2020)