Dr. Kevin Yip

Dr Kevin Yip
Orthopaedic Surgeon
MBBS(UK), FRCS(EDIN), FAM(SING), FHKCOS(ORTHO)

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Mallet Finger

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 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).
  • 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.
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, 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%
    • For patients with delayed treatment or incorrect splint use, fair to poor results
    • 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.
  • 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, 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.
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.

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