Mallet Fracture: A Small Injury with the Risk of Major Deformity, Timely Treatment is Crucial

Understanding Mallet Fractures

A mallet fracture, an avulsion fracture occurring on the posterior aspect of the distal phalanx (the last bone) of a finger, may appear as a minor injury on the surface. However, if not treated properly and in a timely manner, it can result in severe and permanent deformity of the finger.

This injury not only involves a small piece of bone breaking off but also affects the ability to actively extend the distal interphalangeal (DIP) joint, which is crucial for normal daily activities. Such an injury typically occurs when the tip of an already straightened finger is suddenly and forcefully bent.

Common causes of mallet fractures include impact from a ball hitting the fingertip during sports, falls, or crushing injuries from an object. Immediately after the injury, the fingertip may appear to droop downwards, and the affected individual is unable to straighten it using their own strength, although it might be passively straightened (by manual manipulation) initially.

Diagnosis and Assessment

X-rays play a vital role in diagnosing mallet fractures. Through X-rays, doctors perform a detailed assessment of the size of the fractured posterior bone fragment, the degree of displacement, the overall structural integrity of the DIP joint, and specifically, any volar subluxation (forward slippage) of the distal phalanx.

If the fractured bone fragment is small, shows minimal displacement, and the DIP joint structure is normal, the fracture is generally considered stable. Conversely, if the fractured fragment is large, causing volar subluxation or instability in the DIP joint, the injury is categorized as more severe, and surgical stabilization may be considered.

Conservative Treatment: The Importance of Splinting

For stable mallet fractures, the primary treatment is continuous splinting of the DIP joint in an extended (straight) position. This treatment typically involves keeping the DIP joint fully straight for approximately 6 to 8 weeks.

After this period, depending on the fracture's condition, splinting may continue for some additional time, either at night or for protective purposes. Splinting can be achieved using a stack splint, custom-made thermoplastic splint, or other suitable devices. It is extremely important to ensure that the proximal interphalangeal (PIP) joint (the middle joint of the finger) remains free and maintains its mobility during this treatment period.

The most critical factor for successful treatment is that the DIP joint is not repeatedly bent during the initial period. If the DIP joint bends repeatedly, the extensor mechanism (fibers connecting muscles to bone) can lengthen, negatively impacting the healing process and hindering bone union.

When Surgical Intervention is Necessary

It is important to note that not every case of mallet fracture requires surgery. The decision for surgery is primarily made when there is volar subluxation of the distal phalanx, the articular (joint-related) bone fragment is large and displaced, the DIP joint is unstable or displaced from its normal position, the injury is an open fracture, or instability persists despite appropriate conservative treatment.

If necessary, surgical techniques such as extension-block K-wires, percutaneous pinning, small screws, or ORIF (Open Reduction and Internal Fixation) can be employed. The main goal of surgery is to restore the normal structure of the DIP joint, maintain the fractured fragment in its correct position, and secure the functional movement of the finger.

However, it is also a fact that surgery carries potential complications such as infection, nail deformity, joint stiffness, problems related to implanted hardware, and injury to the skin or extensor mechanism. Therefore, for cases where the DIP joint is stable and in place, proper splinting is preferred.

Long-Term Consequences of Delayed Treatment

If a mallet fracture is treated late or improperly, the terminal extensor mechanism may heal in its lengthened position. This results in the development of a DIP extension lag (inability to straighten the DIP joint), which can lead to the fingertip remaining permanently bent.

In the long term, this imbalance can cause hyperextension of the PIP joint, known as 'swan-neck deformity'. Such a deformity not only weakens the finger's grip but also causes significant impairment in everyday fine motor movements.

Management of Chronic Deformities

When deformity due to mallet fracture becomes chronic, its management depends on several factors, including the flexibility of the deformity, the current condition of the DIP joint, the presence of arthritis in the joint, the functional distress experienced by the patient, and the patient's own expectations.

If the deformity is still flexible, re-application of extension splinting and hand therapy (massage and exercises for the hand) can be beneficial. In cases of permanent deformity, surgical procedures such as reconstruction of the terminal extensor mechanism or tendon shortening may be considered.

If there is severe painful arthritis in the DIP joint or significant permanent deformity, permanently fusing the DIP joint (arthrodesis) may be an option for some selected patients.

Special Consideration in Children

Particular caution is necessary when treating mallet fractures in children. An injury to the physeal (growth plate) of the distal phalanx along with a nail-bed injury is termed a 'Seymour fracture'. Mistaking this for a common adult mallet fracture can be a serious error, as the risk of complications such as infection, osteomyelitis (bone infection), growth disturbances, nail deformities, and malunion is significantly higher in children.

Conclusion

The decision for treatment in mallet fractures should not be based solely on the size of the fractured bone fragment but should also consider the stability and the overall structural integrity of the DIP joint. Continuous extension splinting is an effective treatment modality for stable injuries, while surgical stabilization should be seriously considered for cases with subluxation or instability.

Receiving timely and correct treatment plays a crucial role in preventing permanent deformities and functional problems in the future.