Mallet Finger

By admin On Feb 8, 2024

Ovid: 5-Minute Orthopaedic Consult

Editors: Frassica, Frank J.; Sponseller, Paul D.; Wilckens, John H.

Title: 5-Minute Orthopaedic Consult, 2nd Edition

> Table of Contents > Mallet Finger

Mallet Finger

Dawn M. LaPorte MD

Basics

Description

Mallet finger is a loss of continuity of
the conjoined lateral bands at the DIP joint of the finger that results
in a characteristic flexion deformity of the distal joint.
Mallet finger deformity resulting from
the fracture of a child’s distal phalanx usually is a transepiphyseal
fracture of the phalanx.
Classification (1) is used as an aid in establishing an appropriate treatment plan.
- Type I (most common): Closed or blunt trauma with loss of tendon continuity with or without a small avulsion fracture
- Type II: Laceration at or proximal to the DIP joint with loss of tendon continuity
- Type III: Deep abrasion with loss of skin, subcutaneous cover, and tendon substance
- Type IV:
  - a: Transepiphyseal plate fracture in children
  - b: Hyperflexion injury with fracture of the articular surface of 20–50%
  - c: Hyperextension injury with fracture of
    the articular surface usually >50% and with early or late volar
    subluxation of the distal phalanx
Synonyms: Drop finger; Baseball finger

General Prevention

No effective means of prevention are known.
Early detection is associated with a better prognosis.

Epidemiology

Males are affected more often than females, but the numbers vary with the population studied.

Incidence

This injury may occur at any age.
The highest incidence in males occurs in
adolescence and young adulthood (range, 11–40 years), whereas that in
females occurs in middle age (range, 41–60 years) (2).
Incidence increases progressively from the radial to ulnar side of the hand.

Etiology

Mallet finger can occur secondary to a variety of sports, occupational, or home activities.
Open injuries may be caused by sharp or crush-type lacerations, but closed injuries are more common.
The usual mechanism of injury is sudden,
acute, forceful flexion of the extended digit, which results in rupture
of the extensor tendon or avulsion of the tendon with or without a
small fragment of bone from its dorsal insertion.
Forced hyperextension of the distal joint
may result in a fracture at the dorsal base of the distal phalanx
involving 1/3 or more of the phalanx.
- Although a mallet deformity is associated
  with this injury, the lesion should be considered a fracture with a
  secondary mallet finger deformity.
The microvascular anatomy of the distal
digital extensor tendon reveals an area of deficient blood supply in
the region of insertion over the DIP; this vascularity may have
implications in the cause of mallet finger.

Diagnosis

Signs and Symptoms

The DIP joint of the involved finger is
held in flexion, and active extension is lost; full passive extension
usually is present.
Hyperextension of the PIP joint also may be observed.

Physical Exam

Document the integrity of the skin and nail bed.
Note active and passive extension (and flexion if not acute).
Observe the status of the proximal joints.
Diagnosis is based on physical examination with radiographs to assess for fracture.

Tests

Lab

No laboratory tests aid in this diagnosis.

Imaging

AP and lateral radiographs of the involved finger are
mandatory to assess for fracture, because a fracture influences
classification and treatment options.

Pathological Findings

Normal anatomy:
- The lateral bands of the extensor tendon
  from each side of the digit merge and join to form a single tendon on
  the proximal portion of the middle phalanx.
- This tendon continues distally to form a wide unit for insertion into the dorsal base of the distal phalanx.
Loss of continuity of the conjoined
lateral bands at the distal joint of the finger results in a
characteristic flexion deformity of the distal joint.
A study of the microvascular anatomy of
the distal digital extension tendon noted an area of deficient blood
supply here and suggested that this zone of avascularity could have
implications in the cause and treatment of mallet finger (3).

Differential Diagnosis

Fracture of the dorsal base of the distal phalanx with secondary mallet finger deformity
Transepiphyseal plate fracture of the distal phalanx
Flexion contracture/osteoarthritis

Treatment

General Measures

Initial intervention is a minimum of 6 weeks of continuous DIP joint immobilization.
Partial recurrence of the extension lag
is common, and a subsequent regimen of at least 2–3 weeks of night
splinting of the DIP joint in extension is mandatory.
Careful follow-up is required and, if
recurrent extension lag is severe, a second course of full-time
splinting for 8 weeks may be considered.
Surgical treatment frequently is recommended for type IV injuries (4), but splinting often is adequate treatment.
Management of chronic mallet deformities seen late includes arthrodesis or secondary extension tendon reconstruction.
- Mallet deformities not seen until 2–3 months after injury have been improved with prolonged splinting of the distal joint.
- If the patient has severe symptoms, surgical options should be considered.
Medical treatment depends on classification.
Type I:
- A dorsal or volar prefabricated splint (e.g., the stack splint)
- If treated early, excellent to good results in nearly 80% (2,5,6)
- For patients with delayed treatment or incorrect splint use, fair to poor results (7)
- Length of treatment:
  - Continuous maintenance of the extended
    position of the DIP joint must be achieved for a minimum of 6 weeks for
    the splint to be effective.
  - Some clinicians recommend 8 weeks of splinting, followed by 2 weeks of night splinting.
- Direct repair is to be avoided because the extensor tendon at this level is extremely thin and has a poor blood supply.
- Nonoperative treatment yields a more satisfactory result than surgical repair.
- A transarticular Kirschner wire may be placed in patients who cannot wear a splint for 6 weeks.

P.247

Types II and III:
- Repair with a simple figure-8 or roll-type suture, which reapproximates the skin and tendon simultaneously.
- Apply a small dressing, incorporating a splint, which maintains the distal joint in full extension.
- Remove the suture in 10–12 days.
- Maintain the distal joint in the extended
  position by a stack or aluminum foam splint (as for type I injuries)
  for a minimum of 6 weeks, followed by protective ROM.
- Reapply the splint if any extension loss is noted after its removal.
- Type III mallet deformities with loss of
  tendon substance and soft-tissue coverage require reconstructive
  surgery to provide skin coverage, with late reconstruction by free
  tendon graft to restore tendon continuity or with arthrodesis of the
  joint.
- Mallet finger resulting from a distal phalanx fracture in a child usually is a transepiphyseal fracture of the phalanx.
  - Closed reduction of the fracture usually results in correction of the deformity.
  - Continuous external splinting of the
    distal joint in full extension for 3–4 weeks results in fracture union
    and deformity correction.
Type IV:
- In an adult, type IV injuries are associated with major fracture fragments.
- This type of fracture with an associated mallet finger deformity is a relatively uncommon injury.
- Treatment:
  - Operative treatment has been recommended for fracture fragments >1/3 of the articular surface.
  - An accurate reduction is advocated to prevent joint deformity with secondary arthritis and stiffness.
  - However, excellent results have been
    reported with splinting alone, and nonoperative treatment avoids any
    surgery-related complications.
  - Indications for surgery are controversial and may depend on the amount of volar subluxation of the distal phalanx.
- After 6–10 weeks of continuous splinting, the patient may begin guarded flexion exercises; splinting is continued at night.

Special Therapy

Physical Therapy

Occupational therapy may benefit the patient who has a
difficult time regaining flexion after the splinting is completed or
the surgical Kirschner wire is removed.

Surgery

Indicated for open injuries, for a closed
injury in a person who would be unable to work with a splint, and for a
large dorsal fragment with volar subluxation of the distal phalanx.
Reduce the joint, manipulate the fracture
fragment into place, and pass a Kirschner wire longitudinally across
the joint to hold it in full extension.
Options for chronic mallet finger include
plication or reefing of the scarred tendon, arthrodesis,
tenodermodesis, spiral oblique retinacular ligament reconstruction, and
even DIP disarticulation.

Follow-up

Prognosis

Poor prognostic factors include:
- Age >60 years
- Delay in treatment >4 weeks
- Initial active extension lag
- >4 weeks of immobilization without substantial improvement
- Short, stubby fingers

Complications

Skin problems (e.g., dorsal maceration, skin ulceration, tape allergy):
- Dorsal ulceration and maceration with the
  use of dorsal aluminum foam splints: Place tubular gauze or moleskin
  beneath the splint.
- Full-thickness skin necrosis over the DIP
  joint after dorsal splint immobilization in hyperextension: Splint the
  distal joint with minimal hyperextension; do not exceed the amount of
  hyperextension that produces blanching.
Transverse nail grooves
Pain from the splint
Patients treated surgically for mallet
finger have a >50% complication rate, including permanent nail
deformities, joint incongruities, infection, pin or pullout wire
failure, radial or ulnar prominence, and deviation of the DIP joint.
Loss of surgical reduction, requiring additional surgery

Patient Monitoring

Because of the high complication rate (up to 45%; mostly transient skin problems) reported with splinting (7),
most patients require 2 visits during the 1st week of treatment, and
weekly visits thereafter to monitor their progress and check their skin.
After 6–10 weeks, the splint is removed, the finger is inspected, and night splinting is begun.
Careful follow-up is required to monitor for recurrence and to individualize treatment.

References

1. Doyle
JR. Extensor tendons–acute injuries. In: Green DP, Hotchkiss RN,
Pederson WC, eds. Green’s Operative Hand Surgery, 4th ed. New York:
Churchill Livingstone, 1999:1950–1987.

2. Abouna
JM, Brown H. The treatment of mallet finger. The results in a series of
148 consecutive cases and a review of the literature. Br J Surg 1968;55:653–667.

3. Warren RA, Kay NRM, Norris SH. The microvascular anatomy of the distal digital extensor tendon. J Hand Surg 1988;13B:161–163.

4. Baratz
ME, Schmidt CC, Hughes TB. Extensor tendon injuries. In: Green DP,
Hotchkiss RN, Pederson WC, et al., eds. Green’s Operative Hand Surgery,
5th ed. Philadelphia: Elsevier Churchill Livingstone, 2005:187–217.

5. Crawford GP. The molded polythene splint for mallet finger deformities. J Hand Surg 1984;9A: 231–237.

6. Garberman SF, Diao E, Peimer CA. Mallet finger: results of early versus delayed closed treatment. J Hand Surg 1994;19A:850–852.

7. Doyle
JR. Extensor tendon injuries. In: Manske PR, ed. Hand Surgery Update.
Rosemont, IL: American Society for Surgery of the Hand, 1994:149–159.

Miscellaneous

Codes

ICD9-CM

736.1 Mallet finger

Patient Teaching

For the splint to be effective, patients should
understand the importance of the continuous maintenance of the extended
position of the DIP joint for a minimum of 6 weeks.

FAQ

Q: Is treatment of an open mallet injury different from that of closed injury?

A:
Yes. Open mallet injuries are repaired using suture, with or without
pinning the DIP joint in extension for 6 weeks. The preferred treatment
for closed mallet injury is DIP extension splinting worn full-time for
6 weeks and then converted to nighttime wear.

Q: How is a mallet thumb managed?

A:
Mallet thumb injuries are treated the same as mallet fingers: Closed
injuries are splinted and open injuries are managed with direct repair.