Mallet finger is a common injury where a forceful impact, often from a ball, causes the fingertip to suddenly bend, resulting in a characteristic droop. This occurs because the extensor tendon, which straightens the end joint of the finger, is either torn or pulled away from the bone. The resulting inability to actively extend the fingertip, known as an extension lag, requires intervention to prevent long-term deformity. Most mallet finger injuries are successfully treated without surgery, but clarifying the specific circumstances that require an operation is important for proper management.
Identifying Mallet Finger
The injury occurs at the distal interphalangeal joint (DIP joint), the joint closest to the fingernail. The terminal extensor tendon attaches to the dorsal aspect of the distal phalanx (fingertip bone) and allows for active straightening. When the finger is suddenly forced into flexion while the tendon is contracted, the tendon can rupture or avulse a fragment of bone from the phalanx.
Diagnosis is confirmed through a physical examination revealing the inability to actively straighten the DIP joint, even though it can be passively straightened. Imaging, specifically a lateral X-ray, is then used to determine the exact nature of the injury, distinguishing between a pure soft-tissue tendon tear and a bony avulsion fracture, which influences treatment.
Non-Surgical Treatment: The Standard Approach
Non-operative management is the established first-line treatment for almost all mallet finger injuries that do not involve significant joint instability or large bone fragments. This conservative approach focuses on complete, continuous immobilization of the injured DIP joint in full extension or slight hyperextension. The goal is to keep the ends of the torn tendon or the fracture fragment close together, allowing them to heal without tension.
A custom-fitted splint, such as a stack splint, is worn full-time for six to eight weeks. Soft-tissue injuries commonly require eight weeks of splinting, while bony mallet injuries may require six weeks until the fracture is healed. Strict adherence to the splinting schedule is paramount, as accidental flexion can disrupt the delicate healing process and restart the treatment timeline. The splint is designed to allow the middle finger joint (proximal interphalangeal joint) to remain free, preventing stiffness in the rest of the finger.
Conditions that Require Surgical Intervention
Surgery is reserved for a minority of mallet finger cases where the injury is complex, unstable, or has failed conservative treatment. The presence of a bony avulsion fracture is the most common factor shifting management toward surgery. If the fracture fragment involves more than 30% to 50% of the joint surface, or if it is significantly displaced, surgery may be necessary to restore the joint’s smooth surface.
A primary indication for surgery is volar subluxation, where the distal phalanx bone slides forward toward the palm, compromising joint alignment and stability. This instability suggests the extensor mechanism cannot hold the joint in place, increasing the risk of long-term arthritis and poor function. Surgical procedures often involve closed reduction with percutaneous pinning, where small metal pins are inserted through the skin to hold the bone fragment and joint in the correct position until healing occurs.
Other circumstances include open injuries, where the skin is broken over the tendon tear, or chronic mallet fingers. An injury is considered chronic if four weeks or more have passed since the initial trauma, and conservative splinting has failed or was started too late. In these chronic cases, surgical reconstruction may be performed to address the resultant extensor lag, particularly if the droop is severe or if a secondary swan-neck deformity has begun to develop.
Post-Treatment Care and Rehabilitation
Once the initial period of immobilization is complete, whether through splinting or surgical pinning, the focus shifts to restoring motion and strength. The finger is often stiff after continuous splinting, and rehabilitation is necessary to regain a functional range of motion. The initial goal is to gently start active range-of-motion exercises, carefully reintroducing controlled bending of the DIP joint.
Physical therapy, often guided by a certified hand therapist, includes exercises to improve both flexion and extension while protecting the newly healed tendon. These exercises must be progressed gradually to avoid re-injury. Full recovery, including the resolution of stiffness and the return to most daily activities, can take several months following the removal of the splint or pins.