Introduction

Mallet finger is a common injury often resulting from sports or household accidents. It involves injury to the extensor mechanism at the distal interphalangeal (DIP) joint located at the tip of the finger just before the fingernail starts. The injury is usually caused by a forceful impact applied along the length of the finger, causing a drooped fingertip and loss of active extension.¹ Imagine catching a ball and suddenly noticing that the tip of your finger won’t straighten anymore, but instead hangs down, painful and bent. Injuries are typically classified as either tendinous (soft tissue) or bony avulsion, where the extensor tendon pulls off a piece of bone.^2,3 While continuous extension splinting remains the standard treatment for most cases, the role of surgery, especially for injuries involving large bone fragments, remains debated. Studies show comparable outcomes between non-surgical and surgical treatments, with surgery showing improved radiographic alignment but not necessarily better function.^4,5 Therefore, there is insufficient evidence to support routine surgical treatment for closed mallet injuries. This review focuses on identifying clear indications for surgical intervention in mallet finger injuries involving large bony avulsion.

Understanding mallet finger

Anatomy and mechanism

The terminal extensor tendon straightens the fingertip and attaches forearm muscles to the dorsal base of the distal phalanx (back of the last bone in the finger). Muscle contractions pull on the tendon, causing straightening of the finger. Forceful trauma can injure the tendon or pull a bone fragment at its attachment site and even pull it forward (volar subluxation).⁶ Smaller fragments typically preserve joint alignment, while larger ones can destabilize the DIP joint.³

Types of Mallet Finger Injuries

Doyle classified mallet injuries into four types:

• Type I: Closed tendon rupture, with or without small fracture
• Type II: Open injury with tendon damage from skin laceration
• Type III: Open injury with deep skin abrasion and tendon loss
• Type IV: Bony mallet fractures:
  • Transphyseal (in children)
  • Fragment with 20–50% articular involvement
  • Fragment with >50% articular involvement⁷

Large Bony Avulsion

Definition and radiographic criteria 

The standard threshold for a large bone fragment involves 30-50% of the joint surface or an uneven step or gap >2 mm. X-rays are vital to assess fragment size, joint congruity, and volar subluxation, which affects stability.⁸

Clinical implications

Not all large fragments are unstable. A fragment involving more than 30% of the joint surface may remain well-aligned if there is no displacement or subluxation. Surgical consideration depends not just on size but also on joint displacement, incongruity (degree of articular involvement), and stability. These features correlate with a higher risk of complications such as stiffness, pain, or arthritis, if untreated.⁸

Standard treatment for mallet finger

Non-surgical management

For most acute cases, with or without fractures, full-time splinting of the DIP joint in full extension for 6-8 weeks while the bone heals is standard. Night splinting continues for an additional 4-6 weeks. Functional outcomes are typically excellent, with minor extensor lag (droop) of about 5-10°, which rarely affects daily function.⁹

Limitations of Splinting

The biggest challenge is maintaining uninterrupted splinting, any bending can restart the healing. Side effects include skin irritation, stiffness, and frustration but are usually manageable. Studies consistently show no clear advantage of routine surgery over splinting for closed mallet injuries without instability.^2,4

Core Indications for Surgical Repair:

Volar Subluxation of the distal phalanx

When fragments slide out of place, the DIP joint loses alignment and becomes unstable. A splint cannot hold fragments in the right position, so surgery is required to restore joint alignment and accurate healing.⁸ 

Large Bony Avulsion with joint incongruity

Fragments involving 30-50% of the joint surface, particularly with >2 mm displacement or a visible step-off, often require surgical reduction to prevent future joint dysfunction such as long-term stiffness or arthritis.^4,8

Open injuries

Open mallet injuries, like Doyle type II or III, have increased infection risks. Surgical irrigation, debridement and repair of the tendon and/or bone minimize complications and support recovery.³

Irreducible or blocked reduction

Occasionally, bone or soft tissue blocks prevent closed reduction. Surgical intervention is needed to remove the blockage and restore joint anatomy.¹⁰

Failure of non-surgical care

Recurrent symptoms, such as pain, droop, or instability, after a full splinting period may warrant delayed surgical correction.⁴

Chronic mallet with swan-neck deformity

Untreated or misaligned mallet injuries may lead to swan-neck deformity. When the imbalance is due to a malunited fracture, surgical reconstruction or delayed ORIF is considered.¹¹

Patient Factors

Patient factors, such as handedness, occupation, sport, and the ability to adhere to splinting, also influence surgical decision-making.^2,10 

Surgical options

Percutaneous extension-block pinning

Also known as the Ishiguro technique. This uses two thin K-wires - one to lever the fragment into place, then another across the DIP joint to hold the reduction.¹² This method is most commonly used for unstable bony mallet fractures. This procedure has a good union and low re-operation rates.¹²

Trans-DIP K-wire Immobilization

A single K-wire maintains DIP alignment post-reduction. This method is used in stable or minimally displaced fractures.¹³

Open Reduction Internal Fixation (ORIF)

This is reserved for injuries that are irreducible, malrotated, or comminuted. It offers direct visualisation of the injury but can increase soft-tissue damage.¹⁴ Variant techniques such as hook plates, tension bands, and suture-anchors can restore the joint surface directly and are used for complex injuries.¹⁵ 

Risks and complications

Surgical risks include pin-tract infections, nail deformities, skin necrosis, hardware failure, stiffness, and the need for secondary procedures. To minimise complications, surgeons use careful pin placement and protect the nail matrix. Immobilization continues until healing, after which pins are removed and early monitored rehabilitation begins.

Decision-making process

Doctors follow an evidence-based approach when making decisions on a treatment plan. They consider a myriad of information, such as radiographic assessments and clinical assessments, asking questions like: Is the joint aligned? Is the fragment small or large? Is there a step or gap? Does the fingertip stay straight with splinting, or does it slip? Can the patient reliably adhere to wearing a splint? Do they use their hands for sports or heavy work? Contemporary hand surgery reviews and emergency care summaries indicate that the main triggers for surgical intervention are >⅓ articular involvement and/or volar subluxation². However, doctors also consider the operative vs. non-operative outcomes, complications, and delayed presentations or splinting failures.^3,4,10

Why not operate on all large Bony Avulsions?

Both treatments usually give good results. Even large but stable fractures can heal well with splinting.^3,4 Surgery is best reserved for unstable, misaligned, or symptomatic cases. Studies show that while surgery may yield better radiographic outcomes, function is often comparable to splinting.¹⁶ Moreover, surgery carries risks, making it unnecessary in many well-aligned fractures. Shared decision-making is essential, especially for athletes or manual workers who may prefer surgery for faster recovery or splint intolerance.³ 

Recovery and life after treatment

• After Splinting: Continuous splinting for 6-8 weeks, followed by an additional couple of weeks only at night. Most people regain full use of their hand; a slight droop may remain, but it is usually not bothersome
• After Surgery: Pins or screws will hold the bone while it heals and are removed after 4-8 weeks. Early rehabilitation is essential for regaining motion. Risks include stiffness, sensitivity to scars, or changes to the nails
• Long-Term Outlook: Most patients return to their normal lives, work, and sports activities. Chronic pain or arthritis is uncommon if appropriately treated. Patience and following instructions (splinting or post-surgery care) are key^3,4,10

Practical guide for patients

• Get an X-ray
• If the fingertip bone has slipped out of place, surgery is needed
• If the fragment is large and the DIP joint is uneven, it is likely to require surgery
• If the fragment is large but the DIP joint is straight, try splinting
• If splinting fails or the wound remains open, surgery is indicated

Summary

Most mallet fingers can be managed successfully with splinting, especially when the joint is stable and there is no subluxation. Stable large bony mallets without significant displacement can often be treated non-operatively, as splinting is safe, effective, and usually leads to good recovery. Surgery is generally reserved for unstable or uneven fractures, volar subluxation, cases with 30–50% articular involvement with incongruity or >2 mm displacement, open or irreducible injuries, failed splinting, or symptomatic chronic deformity. While surgical repair can improve joint congruity, functional outcomes are often similar to non-operative care in stable cases. Therefore, the decision should be made collaboratively between patient and doctor, weighing radiographic stability, patient needs, and the potential risks of surgery.