Hammer finger is the term for an extensor avulsion fracture or rupture of the distal extensor tendon. Either can result in an inability to extend the distal interphalangeal (DIP) joint.
Mallet finger injuries are:
- Named for the curved deformity of the fingertip that resembles a mallet or hammer
- Caused by disruption of the phalanx extensor mechanism at the level of the distal interphalangeal joint. They are usually due to forced flexion of the distal interphalangeal joints
- resulting in inability to extend the distal phalanx
- A hammer fracture occurs when the extensor tendon also causes the distal phalanx to be avulsed 
Mallet finger injuries are best managed by a multidisciplinary team because the ideal treatment is not yet known.
- Conservative treatment with splinting is widely used for minor injuries (unpredictable outcome)
- Frequent surgery (suboptimal results)
Clinically Relevant Anatomy
The extensor tendons straighten the fingers and thumb through a very complex arrangement. The extensor apparatus is a tendon plexus with aponeurotic sheets. The extensor tendons are located in the back area of the hand and fingers. The function of these tendons is to extend the wrist and finger
In mallet finger injuries, the distal extensor tendons are ruptured. Fracture occurs when the distal phalanx of the finger is forced to bend during active extension, such as in ball games if a ball hits the tip of the outstretched finger.
- The extensor tendons originate in the forearm and cross the metacarpophalangeal joints, attaching indirectly to the proximal phalanx and finally to the distal phalanx. These tendons are responsible for the extension of the fingers
- A mallet finger injury occurs when the extensor tendon ruptures. A hammer fracture occurs when a tendon injury results in an avulsion fracture of the distal phalanx 
- Current evidence supports nonsurgical intervention, but prompt injury management is required to avoid adverse outcomes 
Distal extensor tendon injuries such as hammer finger injuries are common. Distal extensor tendon injuries accounted for 5.6% of hand and wrist injuries.  Hammer finger injury:
- Usually occurs in the workplace or during sports-related activities 
- It is common in young and middle-aged men, and occasionally in older women. The average age of male mallet finger injuries is 34 years. The average age of women is 41 years. 
- It is more common in ball games, as the ball hits the fingertip of the outstretched finger. This forces the distal interphalangeal joint into a forced flexed position, which results in rupture of the extensor tendon
- Distal extensor tendon injuries can also occur with lesser impacts of the injury – such as in older adults with fingers entrapped while performing activities of daily living, such as pulling up a sock or tucking in a sheet 
- The most commonly affected fingers are the long or middle and ring fingers of the dominant hand 
- A trigger event will be reported if it causes distress.
- Initially the wrist is painful and swollen at the DIP joint.
- If the actual nerve ruptures the condition can be relatively painless. Resection of a portion of the bone usually causes slight swelling and pain.
- The ends of the fingers are bent and cannot be stretched voluntarily. The DIP joint can be corrected easily with help from the other side.
- Swan Neck Deformity
- Boutonniere Deformity
- The diagnosis of mallet finger is usually clear on the physical examination
- An X-ray may be taken – the injury may be confirmed as an avulsion fracture or tendon rupture and/or broken bone.
High quality evidence ( a systematic review ) was conducted in 2018 to evaluate treatment interventions for mallet finger. It concluded that both surgical and non-surgical interventions produce excellent results and that the choice of intervention should be individualized patient.
Physical Therapy Treatment
Usually a splint will be worn full-time for 6–8 weeks. Exercises can then be started to gradually increase the motion of the fingertips. This time slowly decreases the amount of time the client spends wearing the bandage. It usually takes about 3–4 weeks to regain maximum motion and strength of the sleeve after exposure.
Non- Surgical 
He may remain cast for about six weeks followed by six weeks of casting at night.
- This will usually result in satisfactory healing and enlargement of the elbow.
- Patient education is essential for the patient to understand the importance of maintaining DIP joint extension.
- The key is to remain laced for the first six weeks
- If the strings are removed and the fingers are allowed to bend, the process breaks down and must be started again
- The leash should remain active at all times even in the bathroom
- The strap should hold the DIP joint in full extension and keep the muscle ends as close to each other as possible. As healing progresses, scar formation repairs the tissue
- When the muscles are strong enough to hold the fingertips directly, a plan is put in place to safely wean the breast slowly from the mesh. When the client resumes sports with your splint on you should teach that you wrap it tightly with sports tape to ensure it does not dislodge
There are many types of straps that are designed to be easy to wear all the time. In some severe cases where the patient must use his hands to continue working (e.g., a surgeon), a metal pin can be inserted into the bone past the DIP joint has acted as an internal root. This empowers patients continue to use their hands. The pin is removed in six weeks.
- In chronic mallet finger cases, braces may still work. In this case, insert the sleeve for approximately eight to 12 weeks to see if the recession decreases to a tolerable level before considering surgery.
- Skin problems associated with long-term dressings include breakouts. It is important to monitor this and you may recommend a different or different device
- The adjacent joint may become stiff when the injured elbow is flexed for this length of time. Develop an exercise program to help move the wrist and reduce joint stiffness
The following video shows how to tape on a mallet sleeve after removing threads.
- Surgical repair of mallet claws should be performed when the bone fragment is large when the fingertip is slightly dislocated or when the cause is dislocation.
- Rehabilitation after mallet finger surgery focuses on maintaining range of motion in other joints and preventing stiffness from disuse
Lin et al. (2018)  reported that the mean DIP joint extensor lag was 5.7° and 7.6° after surgical treatment after conservative management. It is important to incorporate this into patient education, as this will help ensure that patients have realistic expectations for treatment outcomes. 
Any of these complications may occur after nonsurgical or surgical treatment of a hammer fracture:
- Residual extensor hysteresis (noted on physical exam)
- Swan neck deformity (rupture of the volar plate due to rupture of the extensor tendons, resulting in abnormal flexion of the distal interphalangeal (DIP) joint, with the proximal interphalangeal joint remaining in a hyperextended position)
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- Performance Health Academy Network Spinting:Mallet Available from:https://www.youtube.com/watch?v=-PI53P9qD6I (last accessed 5.4.2020)
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