Introduction

Your fingers can flex or extend due to specific cords known as tendons that connect or insert at the points where bones meet, which are referred to as joints. The movement of these tendons results in movements at the joints. Their names are derived from their position; for example, the tendons located on the back or dorsum of the hand are known as extensor tendons, whereas those on the palm leading to the fingers are termed flexor tendons. Injury to the extensor tendon that connects to the joint close to the fingernail, called the distal interphalangeal joint or, in short, DIP joint, leads to a mallet finger. It is caused when a sudden force bends the finger at the DIP joint, potentially tearing it off alone or with a fracture of the bone occurring at the joint.^1,2 

It is commonly observed in sports injuries, such as those in baseball. It also results from sudden falls, cuts with sharp objects, road traffic accidents, accidents at home or assaults causing an open wound at the site. It is commonly known as a jammed finger.² 

Although it can be a minor injury, treatment can affect quality of life. Untreated mallet finger can cause problems in joint movement due to imbalanced extensor forces. Lengthening the tendon affects extension, while shortening restricts DIP joint movement. Improper care may lead to ongoing pain, deformity, and swan neck deformity.²

This article aims to discuss surgical and non-surgical treatment of mallet finger injuries and compare their outcomes.

Extensor tendons

The fingers of the hand contain three short bones known as phalanges, while the thumb consists of two bones. They are called the proximal phalanx, middle phalanx, and distal phalanx, lined up from the palm to the fingertip for each finger. The point where these bones connect is referred to as a joint. The joint closest to the palm is referred to as the proximal interphalangeal joint, whereas the one nearer to the fingertip is known as the distal interphalangeal joint (DIP). The extensor tendons are essential for the backward bending or extension of the fingers. It is common in males, especially the young or middle-aged. The middle finger is the most commonly affected. ²

How to get mallet finger

Abrupt forced bending or flexion of a straight fingertip or hyperextension causes this tendon to be disrupted. It can result from injuries of various degrees, ranging from minor to major. It leads to an extensor lag when moving the digit, and if it remains untreated, a swan neck deformity (SND) of the finger or osteoarthritis (OA) of the DIP joint may develop. An examination of the finger for a mallet finger diagnosis reveals that the distal phalanx is BENT at about 45 degrees, and the person cannot extend the DIP joint. ^3,4

Classification of mallet finger injuries

A mallet finger injury can be classified into different types of injuries.^2,5

Closed injury vs open injury

• Closed: there is no open wound at the site of impact
• Open: this is accompanied by a cut or loss of skin at the site. It is caused by a deep cut at the site or an open wound, which also affects the tendon, tearing it off with or without the bone

Tendinous mallet versus bony mallet injury

• Tendinous mallet: only the tendon is torn
• Bony mallet: there is a fracture of the distal phalanx in addition to the tendon injury

Acute or chronic

• Acute mallet injury: an individual seeks care within 4 weeks of injury 
• Chronic mallet injury: treatment is sought after 4 weeks of injury

Treatment of mallet finger

Non-surgical treatment

Nonoperative treatment is recommended as the primary option for nearly all mallet finger injuries. It is now regarded as the standard procedure for injuries that do not involve fractures, lack volar subluxation of the distal phalanx, or affect less than one-third of the articular surface

The treatment involves using splints to keep the DIP joint in hyperextension for 6 weeks, followed by 2-6 weeks of nighttime splints or during intense activities. The joint must remain hyperextended, even when cleaning fingers.

The splints available come in different types, and the results of their application are similar: 

• Thermoplastic splints that can be tailored to the specific finger or created
• 3D printed splints
• Aluminium foam splints
• Metal splints
• Plastic splints

Although the splints are mostly applied over the palmar surface, they can be applied to any surface of the finger so long as the DIP joint is hyperextended. Compliance is important because, if the finger is flexed during treatment, the treatment time will need to be restarted, prolonging the treatment time.^4,6,7,8,9

Complications related to the use of splints include poor compliance, maceration of the skin, pain, and allergy to the splint.²

Surgical treatment

For mallet finger related to a distal phalanx fracture, surgery is advised when the fracture affects over 30% of the articular surface. Surgical management options consist of closed reduction with percutaneous pinning or open reduction with fixation. Closed reduction can be accomplished by utilising an extension block K-wire to reposition the fracture fragment and secure the extensor tendon. 

On the other hand, open reduction methods for mallet injuries linked to distal phalanx fractures have been implemented with comparable effectiveness. The application of the open technique provides improved access to the fracture location, allowing direct visualisation of the fracture fragments and facilitating easier reduction and fixation. While open repair methods are said to yield positive outcomes, they carry a greater risk of complications than closed repair methods.

In patients who do not improve despite all these surgical options, fusion of the affected joint or arthrodesis in a slightly bent or flexion position will reduce pain, improve cosmesis and function.^12,3,11

Outcomes of non-surgical treatment

Functional recovery

• Good outcomes in most patients with compliant splint use¹³
• It is cheap and convenient 
• Minor extension lag may remain, but often without symptoms

Complications

• Skin irritation or skin breakdown from splint use
• Stiffness, poor compliance leading to recurrence
• Nail deformity 
• Long duration of treatment, including loss of work hours
• Longer duration to return to work¹⁴

Outcomes of surgical treatment

Functional recovery

• Can restore alignment and stability in complex cases
• Similar range of motion to non-surgical in many studies

Complications

• Higher risk of infection, hardware irritation, nail deformity, implant failure, implant removal, joint pain
• Possible stiffness or tendon adhesion
• Rupture of the tendon

Comparison of surgical vs. non-surgical outcomes

Effectiveness

Comparable functional outcomes of non-surgical and surgical treatment are seen in most cases.¹⁴

Risk profile

• Non-surgical: lower risk, fewer complications
• Surgical: higher complication rate, but needed in complex cases^15,16

Recovery time and cost

• Non-surgical treatment: often, cheaper, longer splinting and duration of treatment require compliance to achieve success
• Surgical treatment: higher cost, potentially faster in complex injuries, shorter recovery time, and more accurate^15,16

Summary

Mallet finger injuries are common, arising from either minor injuries or major accidents. A majority of mallet injuries are treated non-surgically with good outcomes, especially in compliant patients. Surgery is indicated in open injuries, significant joint displacement, and when surgical means are not successful. Most studies show comparable outcomes when either method is used. Treatment should be individualised based on the type of injury, compliance, patients’ occupation, and needs.