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Mallet Finger

  • Author: Roy A Meals, MD; Chief Editor: Harris Gellman, MD  more...
 
Updated: Aug 19, 2015
 

Background

The term mallet finger has long been used to describe the deformity produced by disruption of the terminal extensor mechanism at the distal interphalangeal (DIP) joint.[1, 2, 3, 4] It is the most common closed tendon injury seen in athletes, though it is also common in nonathletes after "innocent" trauma. Mallet finger has also been referred to as drop, hammer, or baseball finger (though baseball accounts for only a small percentage of such injuries). (See Etiology and Epidemiology.)

The terminal portion of the extensor mechanism that crosses the DIP joint in the midline dorsally is responsible for active extension of the distal joint. A flexion force on the tip of the extended finger jolts the DIP joint into flexion. This may result in a stretching or tearing of the tendon substance or an avulsion of the tendon's insertion on the dorsal lip of the distal phalanx base. In either instance, active extension power of the DIP joint is lost, and the joint rests in an abnormally flexed position. (See Etiology and Presentation.)

Although athletes and coaches often believe mallet injuries to be minor, with many cases going untreated, all individuals with finger injuries, including suspected mallet finger, should have a systematic evaluation performed. Good results can usually be obtained with early treatment of such injuries, whereas a delay in or lack of treatment may produce permanent disability. (See Prognosis, Workup, and Treatment.)

Controversy exists as to whether the management of bony mallet injuries should be closed or open, especially when the dorsal avulsion fragment is large and the substance of the distal phalanx is subluxed anteriorly. The literature, however, supports the concept of nonoperative treatment even in these cases. (See Treatment.)

For patient education information, see the First Aid and Injuries Center, as well as Mallet Finger and Broken Finger.

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Anatomy

The terminal extensor tendon is a thin, flat structure measuring approximately 1 mm thick and 4-5 mm wide. This tendon occupies the sparse space between the bone and dorsal skin and inserts onto the dorsal lip of the distal phalanx, well proximal to the germinal nail matrix. At the DIP joint, the tendon's excursion is only several millimeters from full joint extension to 80° of flexion. As its name implies, the terminal extensor tendon is the terminal extension of the dorsal mechanism, which is a complex crossing of fibers at the proximal interphalangeal (PIP) and metacarpophalangeal (MCP) joints.

Powered by the lumbrical and interosseous muscles, the dorsal mechanism flexes the MCP joint and extends the PIP and DIP joints.

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Etiology

Any forced flexion of the finger while it is held in an extended position risks the integrity of the extensor mechanism at the DIP joint. The classic mechanism of injury is a finger held rigidly in extension or nearly full extension when the finger is struck on the tip by a softball, volleyball, or basketball. Other common mechanisms of injury include forcefully tucking in a bedspread or slipcover or pushing off a sock with extended fingers. A direct blow over the dorsum of the DIP joint may also produce mallet finger.

Mallet deformity can also be associated with a fracture of the dorsal articular surface of the distal phalanx. Radiographically, these bony avulsions can be characterized into three common patterns, as follows:

  • A tiny fleck of bone that involves less than 25% of the articular surface
  • A large bony fragment that involves 30% or more of the articular surface
  • An avulsion of any size that is associated with palmar subluxation of the distal phalanx

Generally, fleck fractures and nondisplaced avulsions that involve up to 40% of the joint surface are believed to be stable injuries.[2] Individuals with stable injuries are candidates for conservative treatment. (See the image below.)

Stable mallet fracture that involves 40% of the jo Stable mallet fracture that involves 40% of the joint surface.

From experimental studies, the rate of loading determines whether a tendon (or ligament) ruptures in midsubstance or is avulsed from its bony attachment. Rapid loading rates are more likely to cause a tear in the tendon itself, while lower loading rates are more likely to cause a bony avulsion. This is because the bone is relatively more viscoelastic than the tendon.

Swan-neck deformity

With a disruption of the dorsal mechanism at the DIP joint, the entire power of extension is directed to the PIP joint. Over time, and especially if the volar plate is lax, this concentrated extension force results in PIP joint hyperextension and a swan-neck deformity (ie, the DIP joint rests in an abnormally flexed position and the PIP joint rests in a hyperextended position). This deformity frequently causes a functional deficit.[5] Therefore, even if a mallet finger is not particularly symptomatic from a functional or cosmetic perspective, treatment of the mallet injury may preclude development of swan-neck deformity.

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Epidemiology

Several different athletic injuries can occur at the interphalangeal joints. The most common injury is a sprain of the PIP joint, the so-called jammed finger. Mallet fingers are less common than PIP joint sprains, but they are more common than PIP fractures or fracture dislocations and are also the most common closed tendon injury seen in athletes. (Similar injuries to the extensor mechanism at the interphalangeal joint of the thumb occur, albeit infrequently.) As previously stated, mallet finger is also a common trauma injury in nonathletes.

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Prognosis

An untreated mallet finger is rarely of functional consequence unless a secondary swan-neck deformity occurs. Even in those cases, patients rarely request surgical reconstruction, choosing instead to live with the injury. With this in mind, treatment of a mallet finger should not be worse than the disease. Although an untreated mallet finger may be of some cosmetic consequence, treatment that leaves a finger with improved appearance but diminished function is not ideal.

A functionally and cosmetically normal finger can be obtained with conservative treatment, as long as the patient understands the concept of nonstop extension splinting and is compliant with the care. It may take several months following completion of splinting for local swelling and erythema to subside, but thereafter, the finger’s appearance and mobility will be excellent.

Frequently, a faint residual extension lag is present, in the range of 5-10°, but is observable only on close scrutiny. Beware of the patient with naturally hyperextensible interphalangeal joints. Caution these patients at the outset that the best they can hope for is restoration of extension to neutral rather than the degree of active hyperextension observed in their adjacent digits. This loss of complete extension will present no functional difficulties and will be of trivial cosmetic consequence.

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Contributor Information and Disclosures
Author

Roy A Meals, MD Clinical Professor, Department of Orthopedic Surgery, University of California, Los Angeles, David Geffen School of Medicine

Roy A Meals, MD is a member of the following medical societies: American Society for Surgery of the Hand

Disclosure: Received royalty from George Tiemann Company for other.

Chief Editor

Harris Gellman, MD Consulting Surgeon, Broward Hand Center; Voluntary Clinical Professor of Orthopedic Surgery and Plastic Surgery, Departments of Orthopedic Surgery and Surgery, University of Miami, Leonard M Miller School of Medicine, Clinical Professor, Surgery, Nova Southeastern School of Medicine

Harris Gellman, MD is a member of the following medical societies: American Academy of Medical Acupuncture, American Academy of Orthopaedic Surgeons, American Orthopaedic Association, American Society for Surgery of the Hand, Arkansas Medical Society

Disclosure: Nothing to disclose.

Acknowledgements

Michael S Clarke, MD Clinical Associate Professor, Department of Orthopedic Surgery, University of Missouri-Columbia School of Medicine

Michael S Clarke, MD is a member of the following medical societies: American Academy of Orthopaedic Surgeons, American Academy of Pediatrics, American Association for Hand Surgery, American College of Surgeons, American Medical Association, Arthroscopy Association of North America, Clinical Orthopaedic Society, Mid-Central States Orthopaedic Society, and Missouri State Medical Association

Disclosure: Nothing to disclose.

Henry T Goitz, MD Academic Chair and Associate Director, Detroit Medical Center Sports Medicine Institute; Director, Education, Research, and Injury Prevention Center; Co-Director, Orthopaedic Sports Medicine Fellowship

Henry T Goitz, MD is a member of the following medical societies: American Academy of Orthopaedic Surgeons and American Orthopaedic Society for Sports Medicine

Disclosure: Nothing to disclose.

Thomas R Hunt III, MD Professor and Chairman, Joseph Barnhart Department of Orthopedic Surgery, Baylor College of Medicine

Thomas R Hunt III, MD is a member of the following medical societies: American Academy of Orthopaedic Surgeons, American Association for Hand Surgery, American Orthopaedic Association, American Orthopaedic Society for Sports Medicine, American Society for Surgery of the Hand, AO Foundation, Mid-America Orthopaedic Association, and Southern Orthopaedic Association

Disclosure: Tornier Royalty Independent contractor; Tornier Ownership interest None; Lippincott Royalty Independent contractor

Michael E Robinson, MD Consulting Staff, Department of Orthopedics, Division of Primary Care Sports Medicine, Permanente Medical Group and Kaiser Hospital

Michael E Robinson, MD is a member of the following medical societies: American Medical Society for Sports Medicine

Disclosure: Nothing to disclose.

Anthony J Saglimbeni, MD President, South Bay Sports and Preventive Medicine Associates; Private Practice; Team Internist, San Francisco Giants; Team Internist, West Valley College; Team Physician, Bellarmine College Prep; Team Physician, Presentation High School; Team Physician, Santa Clara University; Consultant, University of San Francisco, Academy of Art University, Skyline College, Foothill College, De Anza College

Anthony J Saglimbeni, MD, is a member of the following medical societies: California Medical Association and Santa Clara County Medical Association

Disclosure: South Bay Sports and Preventive Medicine Associates, Inc Ownership interest Other

Francisco Talavera, PharmD, PhD Adjunct Assistant Professor, University of Nebraska Medical Center College of Pharmacy; Editor-in-Chief, Medscape Drug Reference

Disclosure: Medscape Salary Employment

Craig C Young, MD Professor, Departments of Orthopedic Surgery and Community and Family Medicine, Medical Director of Sports Medicine, Director of Primary Care Sports Medicine Fellowship, Medical College of Wisconsin

Craig C Young, MD is a member of the following medical societies: American Academy of Family Physicians, American College of Sports Medicine, American Medical Society for Sports Medicine, and Phi Beta Kappa

Disclosure: Nothing to disclose.

References
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  8. Valdes K, Naughton N, Algar L. Conservative treatment of mallet finger: A systematic review. J Hand Ther. 2015 Jul-Sep. 28 (3):237-46. [Medline].

  9. Shimura H, Wakabayashi Y, Nimura A. A novel closed reduction with extension block and flexion block using Kirschner wires and microscrew fixation for mallet fractures. J Orthop Sci. 2014 Mar. 19(2):308-12. [Medline]. [Full Text].

  10. O'Brien LJ, Bailey MJ. Single blind, prospective, randomized controlled trial comparing dorsal aluminum and custom thermoplastic splints to stack splint for acute mallet finger. Arch Phys Med Rehabil. 2011 Feb. 92(2):191-8. [Medline].

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  16. Shin EK, Bae DS. Tenodermodesis for chronic mallet finger deformities in children. Tech Hand Up Extrem Surg. 2007 Dec. 11(4):262-5. [Medline].

  17. Teoh LC, Lee JY. Mallet fractures: a novel approach to internal fixation using a hook plate. J Hand Surg Eur Vol. 2007 Feb. 32(1):24-30. [Medline].

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  19. Georgescu AV, Capota IM, Matei IR. A new surgical treatment for mallet finger deformity: Deepithelialised pedicled skin flap technique. Injury. 2013 Jan 19. [Medline].

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  22. Witherow EJ, Peiris CL. Custom made finger orthoses have fewer skin complications when compared to prefabricated finger orthoses in management of mallet injury: A systematic review and meta-analysis. Arch Phys Med Rehabil. 2015 Jul 8. [Medline].

  23. Tocco S, Boccolari P, Landi A, Leonelli C, Mercanti C, Pogliacomi F, et al. Effectiveness of cast immobilization in comparison to the gold-standard self-removal orthotic intervention for closed mallet fingers: a randomized clinical trial. J Hand Ther. 2013 Jul-Sep. 26(3):191-200; quiz 201. [Medline].

 
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Despite active extension effort, the distal interphalangeal joint of the index finger rests in flexion, characteristic of a mallet finger.
Typical mallet finger deformity.
This radiograph depicts a large, dorsal-lip avulsion fracture from the distal phalanx, a bony mallet injury.
Mallet fracture with volar subluxation of the distal phalanx.
Stable mallet fracture that involves 40% of the joint surface.
Dorsal aluminum foam splint for the treatment of a mallet finger.
Stack splints are widely used for the treatment of mallet finger.
Molded plastic stack splint for the treatment of mallet finger.
A skin-tight plaster cast can effectively hold the distal interphalangeal joint extended and the proximal interphalangeal joint (PIP) flexed when a mallet deformity is accompanied by a hyperextensible PIP. Not immobilizing the PIP in partial flexion risks the development of a swan-neck deformity.
Pressure-sore formation can result from a splint that is applied too tightly, especially if the joint is maintained in a hyperextended position rather than a position of neutral extension.
This photo demonstrates a thermoplastic blank for a custom-molded mallet finger splint and an oblique view of the molded splint in place.
Dorsal view of the custom-molded thermoplastic splint in place.
Volar view of the thermoplastic splint in place.
Application of the thermoplastic splint.
 
 
 
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