A mallet finger is a common injury where the tip of a finger is bent down and cannot be straightened on its own. This condition occurs when the force of an impact, often from catching a ball or a simple everyday mishap, damages the mechanism responsible for straightening the end joint. The resulting droop, or flexion deformity, is the hallmark sign of this injury. The question of whether this injury can heal without intervention is frequent, and the answer lies in understanding the specific anatomy involved.
Understanding the Injury Mechanism
Mallet finger occurs due to a disruption of the extensor tendon at the distal interphalangeal (DIP) joint, the joint closest to the fingertip. This thin tendon runs along the back of the finger and is responsible for pulling the fingertip straight. The injury is typically caused by a sudden, forceful bending of the extended fingertip, which tears the tendon where it attaches to the distal phalanx, the end bone of the finger.
In many cases, the tendon simply ruptures, resulting in a soft tissue mallet finger. Sometimes, the force pulls a small fragment of bone away from the distal phalanx along with the tendon attachment, creating an avulsion fracture. This is termed a bony mallet finger and alters the treatment approach. Regardless of the type, the primary result is the loss of active extension, causing the fingertip to rest in a bent position.
Why Immobilization is Required for Healing
A mallet finger generally cannot heal on its own because the severed or stretched ends of the tendon cannot easily reattach without external support. The powerful flexor tendons on the palm side of the finger exert an unopposed pull. This pull keeps the end of the finger bent and prevents the extensor tendon from slackening enough to bridge the gap. This continuous tension constantly pulls the healing tendon fibers apart, leading to a permanent droop if left untreated.
The standard non-surgical treatment is continuous splinting. Splinting mechanically holds the DIP joint in a straight or slightly hyperextended position. This immobilization brings the torn ends of the tendon or the bone fragment into close proximity, allowing natural healing to repair the tissue. The splint must be worn full-time for an extended period, typically six to eight weeks, to ensure the tendon fibers scar down securely.
The success of splinting depends entirely on strict adherence to the protocol, meaning the splint must be worn 24 hours a day. Removing the splint or allowing the fingertip to droop even once disrupts the delicate repair process, forcing the patient to restart the entire six to eight-week cycle. Soft tissue injuries often require eight weeks, while bony mallet injuries may sometimes heal in six weeks due to the stabilization provided by the bone fragment.
When Surgical Intervention is Necessary
Most mallet finger injuries are successfully managed with non-surgical splinting, but surgery is reserved for specific, complicated cases. One primary indication for surgery is a large avulsion fracture, particularly if the bone fragment involves more than 30% to 50% of the joint surface. A large fragment can cause the joint to become unstable or misaligned, which splinting alone cannot correct.
Another necessity for surgical repair is joint subluxation, where the distal phalanx shifts out of its proper position, often toward the palm side of the hand. When the joint is displaced and cannot be realigned through splinting, surgery is required to stabilize the joint. The procedure aims to realign the bone fragment or joint using wires or small pins to hold the structures in place while they heal, essentially acting as an internal splint.
Surgery may also be considered for chronic mallet injuries that have been neglected or treated incorrectly for several months, resulting in a persistent deformity. In these long-standing cases, the tendon may have scarred in a lengthened position, making non-surgical repair unlikely to succeed. Surgical intervention aims to restore the correct length and tension to the extensor mechanism.
Avoiding Long-Term Complications
The most significant consequence of delayed or inadequate treatment is a permanent “extensor lag,” which is a persistent inability to fully straighten the fingertip. While a minor residual droop is common even after successful treatment, a significant lag can impair the hand’s function and dexterity. This persistent flexion deformity is often accompanied by joint stiffness and can lead to long-term pain.
The imbalance of forces across the finger joint can result in the development of a secondary deformity called a Swan-Neck Deformity. This condition occurs when the middle joint of the finger hyperextends backward to compensate for the drooping fingertip. This compensatory mechanism can severely affect the finger’s overall function and appearance.
Prompt medical evaluation and the initiation of continuous splinting are the best defenses against these long-term issues. Untreated injuries, especially those involving a bone fragment, also increase the risk of degenerative changes and osteoarthritis in the DIP joint over time. Seeking care immediately ensures the best chance for a full functional recovery and prevents a simple tendon injury from becoming a complicated, permanent hand problem.