Mallet Finger: Causes, Symptoms, Diagnosis, and Treatment

What is Mallet Finger?

Mallet finger, also known as baseball finger or dropped finger, is a common injury characterized by the inability to straighten the tip of the finger due to damage to the extensor tendon that straightens the outermost joint.

Anatomy of the Finger & The Injury

The human finger is a marvel of biomechanical engineering, allowing for a vast range of precise movements. Central to its function are a complex network of bones, ligaments, and tendons. Specifically, the extensor tendons run along the back of the hand and fingers, connecting muscles in the forearm to the finger bones. These tendons are crucial for extending or straightening the fingers.

Mallet finger occurs when the extensor tendon that attaches to the distal phalanx (the outermost bone of the finger) is damaged. This damage typically happens at the distal interphalangeal (DIP) joint, the last joint closest to the fingertip. The injury can manifest in a few ways:

• Tendon Rupture: The tendon itself can tear or rupture, detaching from its insertion point on the bone.
• Avulsion Fracture: The tendon can pull off a small piece of bone where it attaches, known as an avulsion fracture. This is a common and often more severe form of mallet finger.

When this tendon is disrupted, the affected finger segment loses its active ability to extend, causing the fingertip to droop or bend downwards.

Causes of Mallet Finger

Mallet finger typically results from a sudden, forceful impact to the extended fingertip. This impact causes the fingertip to be aggressively bent downwards, overwhelming the extensor tendon's ability to resist.

Common scenarios include:

• Sports Injuries: Often seen in sports like basketball, volleyball, baseball, or football, where a ball directly strikes an outstretched finger. This is why it's sometimes called "baseball finger."
• Everyday Accidents: Simple incidents like tucking in a bedsheet, catching a fall, or even forcefully putting on socks can cause the injury if the fingertip is caught and bent.
• Work-Related Incidents: Certain occupations involving manual labor or repetitive hand movements may increase risk, though direct impact is usually the cause.

The injury can occur with minimal force if the finger is in a vulnerable position.

Signs and Symptoms

Recognizing the signs of mallet finger is crucial for prompt treatment. Key indicators include:

• Drooping Fingertip: The most defining symptom is the inability to actively straighten the tip of the affected finger, which remains in a bent or flexed position at the DIP joint.
• Pain and Swelling: Immediately following the injury, there is usually localized pain, tenderness, and swelling around the DIP joint.
• Bruising: Discoloration or bruising may develop around the injured area.
• Nail Bed Injury: In some cases, especially with avulsion fractures, there might be associated damage to the nail bed.
• Lack of Active Extension: While the finger can often be passively straightened with the other hand, it will immediately drop back down once released.

Symptoms may not always be severe, and some individuals might initially dismiss the injury, which can complicate treatment later.

Diagnosis

A proper diagnosis of mallet finger typically involves a combination of clinical examination and imaging:

• Clinical Examination: A healthcare professional will visually inspect the finger and assess its range of motion. They will test the ability to actively extend the DIP joint and compare it to passive extension. Tenderness and swelling at the DIP joint are also evaluated.
• X-rays: X-rays are crucial for confirming the diagnosis and, more importantly, for ruling out an avulsion fracture. An X-ray can show if a piece of bone has been pulled away by the tendon, which can influence treatment decisions. It also helps to assess for any joint subluxation or other bone injuries.

Treatment Options

Treatment for mallet finger aims to restore the extensor tendon's function and prevent long-term deformity. The approach depends on the severity of the injury, particularly whether an avulsion fracture is present and its size.

Conservative Management (Non-Surgical)

The vast majority of mallet finger injuries are treated non-surgically, especially if there is no significant avulsion fracture or if the fracture fragment is small and well-aligned.

• Continuous Splinting: This is the cornerstone of non-surgical treatment. The injured finger's DIP joint is immobilized in a straight (extended) position using a custom or pre-fabricated splint. The goal is to keep the tendon ends approximated, allowing them to heal without tension.
• Splinting Duration: The splint must be worn continuously for 6 to 8 weeks, even during sleep and bathing. Any flexion of the DIP joint during this period can disrupt the healing process and prolong recovery.
• Skin Care: Regular cleaning of the finger and splint is important to prevent skin irritation. The splint should only be removed carefully for cleaning, ensuring the DIP joint remains extended.
• Gradual Weaning: After the initial healing period, the splint is gradually weaned off, typically over another 2-4 weeks, allowing for controlled, gentle range of motion exercises.

Surgical Intervention

Surgery is less common and typically reserved for specific situations:

• Large Avulsion Fractures: If a large piece of bone is pulled off, causing joint instability or subluxation (misalignment of the joint).
• Joint Subluxation: When the DIP joint is significantly displaced.
• Chronic Cases: If conservative treatment has failed, or if the injury is very old (several months) and has resulted in a fixed deformity.
• Open Injuries: If the injury involves a laceration that exposes the tendon or bone.

Surgical procedures may involve using pins, screws, or sutures to reattach the tendon or bone fragment, or to stabilize the joint.

Rehabilitation and Recovery

Regardless of the treatment method, rehabilitation is critical for optimal recovery and regaining full finger function.

• Physical Therapy: A hand therapist or physical therapist plays a vital role. After the initial immobilization period, they will guide you through a structured exercise program to:
  • Restore Range of Motion: Gradually increase the active and passive movement of the DIP joint.
  • Strengthen Muscles: Improve the strength of the intrinsic hand muscles and finger extensors.
  • Improve Dexterity: Re-establish fine motor skills and coordination.
• Adherence to Protocols: Strict adherence to the splinting schedule and rehabilitation exercises is paramount. Prematurely stopping splinting or aggressive exercises can lead to re-injury or a persistent "mallet deformity."
• Potential Complications: If left untreated or improperly managed, mallet finger can lead to a permanent drooping deformity, chronic pain, stiffness, and difficulty with activities requiring fine motor control.

Prevention

While not all mallet finger injuries are preventable, certain measures can reduce the risk:

• Protective Gear: Athletes participating in sports with a high risk of finger impact (e.g., basketball, volleyball) may consider using protective taping or finger guards, though these do not guarantee full protection.
• Awareness: Being mindful of hand placement during activities that could lead to a sudden impact on the fingertips.
• Proper Technique: In sports, learning proper catching and handling techniques can minimize awkward finger positions.

Understanding the anatomy, causes, and treatment of mallet finger empowers individuals to seek timely care and follow rehabilitation protocols, leading to the best possible outcome for this common, yet often debilitating, finger injury.