eMedicine Specialties > Sports Medicine > Wrist and Hand

Metacarpophalangeal Joint Dislocation

Author: Matthew Gammons, MD, Assistant Clinical Professor, Department of Family and Community Medicine, Medical College of Wisconsin; Medical Director, Castleton State College; Consulting Staff, Vermont Orthopaedic Clinic and Killington Medical Clinic
Contributor Information and Disclosures

Updated: Aug 7, 2008

Introduction

Background

Sprains and dislocations of the metacarpophalangeal (MCP) joint of the finger are relatively rare due to the protected position of this joint in the hand.1,2,3,4 Injuries to the MCP joint of the thumb are more common, although these usually consist of collateral ligament injuries rather than dorsal or palmar dislocations.5,6

For excellent patient education resources, visit eMedicine's Bone, Joint, and Muscle Center and Breaks, Fractures, and Dislocations Center. Also, see eMedicine's patient education articles, Finger Dislocation, Broken Finger, and Sprains and Strains.

Related eMedicine topics:
Joint Reduction, Finger Dislocation
Joint Reduction, Thumb Dislocation
Phalangeal Fractures

Related Medscape topics:
Resource Center Joint Disorders
Specialty Site Orthopaedics

Functional Anatomy

The bony anatomy of the finger MCP joint provides greater laxity in extension, with the shallow articular surface of the proximal phalanx resting on the spherical metacarpal head. The metacarpal head is wider in palmar orientation, which leads to increasing bony stability as the joint approaches maximal flexion. Soft-tissue constraints, including the volar plate, accessory and true collateral ligaments, dorsal capsule, extensor tendon and sagittal band, and intrinsic tendons provide additional stability to the MCP joint. This results in an arc of motion from 30º of hyperextension to 120º of flexion, 30-40º of mediolateral laxity, and a small degree of rotational laxity.

The volar plate is a fibrocartilaginous structure firmly attached to the base of the proximal phalanx. Its origin, just proximal to the metacarpal head, is thin and diaphanous; this allows hyperextension of the MCP joint, but it is also the part of the joint most susceptible to injury during dislocations. The deep transverse metacarpal ligaments further stabilize the volar plates of the neighboring MCP joint.

The collateral ligaments originate from mediolateral depressions in the metacarpal head and travel in a distal-palmar direction to insert onto the base of the proximal phalanx. The elliptical shape of the metacarpal head causes these ligaments to loosen in extension and tighten in flexion. The accessory collateral ligament spans from the true collateral ligament to the volar plate, providing additional joint stability in extension. The central extensor tendon and sagittal band augment the thin dorsal capsule. The tendons of the palmar and dorsal interossei add a small degree of dynamic stability.

The MCP joint of the thumb is a condyloid (hinged) joint, with a quadrilateral rather than spherical metacarpal head. The capsule and ligaments of this joint are similar to those of the finger MCP joint. Additionally, the volar plate of the thumb MPJ usually contains 2 sesamoids that articulate with the metacarpal head. The insertion of the thenar muscles into the sesamoids contributes to joint stability. These bony and ligamentous constraints allow less motion than in the MCP joint of the fingers, especially in lateral motion and rotation; abduction and adduction average 10º and a slight amount of pronation occurs during flexion.

Related eMedicine topic:
Hand, Anatomy

Sport-Specific Biomechanics

Dorsal MCP joint dislocations have been described as simple or complex. Simple dislocations are those in which no soft tissue is interposed in the joint. These are usually reduced easily with an appropriate closed technique. In a classic article published in 1957, Kaplan elegantly described the anatomic features of the complex MCP joint dislocation.7 A metacarpal head displaced in palmar orientation sits between the lumbrical muscle radially and the flexor tendons ulnarly. The volar plate, still firmly attached to the base of the proximal phalanx, is displaced into the MCP joint. Longitudinal traction only further tightens these already taut soft tissues, trapping the metacarpal head. Complex dislocations usually require open reduction.

Related Medscape topics:
Resource Center Exercise and Sports Medicine
Resource Center Joint Disorders
Specialty Site Orthopaedics

Clinical

History

  • Finger metacarpophalangeal joint dislocation (MCP) joint
    • The border digits (index and small) are more susceptible to injury, particularly in extension when either finger is less protected by neighboring digits and the collateral ligaments are lax.
    • Sudden forces that push the finger into ulnar deviation or hyperextension may lead to collateral ligament sprain, a torn volar plate, or frank dislocation of the MCP joint.
    • Sudden deviation or twisting of the finger may cause collateral ligament injury. The 3 ulnar digits are affected more commonly than the index finger.
  • Thumb MCP joint
    • Similar to the MCP joint of the fingers, dorsal dislocations of the thumb MCP joint are more common than volar dislocations.
    • Some patients present with a history of a probable dislocation that was reduced at the time of injury. A number of case reports have described 2 level dislocations of the thumb in higher-energy trauma: simultaneous interphalangeal and MCP joint dislocation8 or MCP joint dislocation in association with dislocation or fracture -dislocation of the carpometacarpal joint (Bennett fracture).
    • Sprains or ruptures of the collateral ligaments of the thumb involve the radial structures 25-40% of the time; most injuries to the thumb affect the ulnar collateral ligament. A sudden adduction force on the MCP joint after a direct fall onto the thumb or palm leads to a partial or complete rupture of the radial collateral ligament.
    • For information on the ulnar collateral ligament, see Gamekeeper's Thumb and Skier's Thumb.

Physical

  • Finger MCP joint hyperextension injury
    • A mild hyperextension force may cause stretching or a complete tear of the proximal membranous origin of the volar plate.
    • The MCP joint may be resting in 60º of hyperextension.
    • The patient demonstrates tenderness over the volar MCP joint with direct pressure or passive extension of the finger.
    • The examiner must avoid applying traction or a hyperextension force that could convert the hyperextension into a dislocation.
  • Finger MCP joint dorsal dislocation
    • The proximal phalanx sits dorsally over the metacarpal head. The MCP joint may be slightly hyperextended, and the interphalangeal joints are flexed slightly.
    • The prominent metacarpal head can be palpated in the palm. The adjacent skin may be puckered.
  • Finger MCP joint collateral ligament injury: The general classification of these injuries is as follows:
    • A first-degree sprain has minimal ligament injury and manifests as tenderness with no laxity.
    • A second-degree sprain has a partial tear and manifests as tenderness with mild laxity.
    • A third-degree sprain has complete ligament rupture and manifests as tenderness, swelling, and gross instability.
  • Thumb MCP joint dislocation
    • Similar to the MCP joint of the fingers, dorsal dislocations of the thumb MCP joint are more common than volar dislocations.
    • The proximal phalanx rests dorsal to the metacarpal interphalangeal joint in mild flexion.
    • The metacarpal head is palpable in the palm.
  • Thumb MCP joint radial collateral ligament
    • Tenderness and swelling over the radial and dorsoradial aspect of the joint is present, as the dorsal capsule is often involved in this injury complex.
    • Progressive laxity leads to an ulnar-deviated thumb position.
    • Decreased pinch strength is present, even with mild ligament injury.
  • Locked MCP joint of the thumb9
    • Less frequently, a hyperextension force to the thumb may cause the thumb to lock in that position, without actually dislocating the joint.
    • The torn volar plate and accessory collateral ligament may become entrapped on a prominence of the radial condyle of the metacarpal head.

Causes

MCP joint dislocations are usually caused by forced hyperextension of the digit. Radial collateral ligament injuries occur during forced ulnar deviation of a flexed MCP joint.

More on Metacarpophalangeal Joint Dislocation

Overview: Metacarpophalangeal Joint Dislocation
Differential Diagnoses & Workup: Metacarpophalangeal Joint Dislocation
Treatment & Medication: Metacarpophalangeal Joint Dislocation
Follow-up: Metacarpophalangeal Joint Dislocation
Multimedia: Metacarpophalangeal Joint Dislocation
References
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References

  1. Glickel SZ, Barron OA, Eaton RG. Dislocations and ligament injuries in the digits. In: Green DP, Hotchkiss RN, Pederson WC, eds. Green's Operative Hand Surgery. 4th ed. New York, NY: Churchill Livingstone; 1999:772-807.

  2. Neviaser RJ. Dislocations and ligamentous injuries of the digits. In: Chapman MW, ed. Operative Orthopaedics. 2nd ed. Philadelphia, Pa: Lippincott Williams & Wilkins; 1993:1237-50.

  3. Lourie GM, Gaston RG, Freeland AE. Collateral ligament injuries of the metacarpophalangeal joints of the fingers. Hand Clin. Aug 2006;22(3):357-64, viii. [Medline].

  4. Zemel NP. Metacarpophalangeal joint injuries in fingers. Hand Clin. Nov 1992;8(4):745-54. [Medline].

  5. Melone CP Jr, Beldner S, Basuk RS. Thumb collateral ligament injuries. An anatomic basis for treatment. Hand Clin. Aug 2000;16(3):345-57. [Medline].

  6. Posner MA, Retaillaud JL. Metacarpophalangeal joint injuries of the thumb. Hand Clin. Nov 1992;8(4):713-32. [Medline].

  7. Kaplan EB. Dorsal dislocation of the metacarpophalangeal joint of the index finger. J Bone Joint Surg Am. Oct 1957;39-A(5):1081-6. [Medline]. [Full Text].

  8. Tabib W, Sayegh S. Simultaneous dislocation of the metacarpophalangeal and interphalangeal joints of the thumb. Scand J Plast Reconstr Surg Hand Surg. 2002;36(6):376-8. [Medline].

  9. Inoue G, Miura T. Locked metacarpo-phalangeal joint of the thumb. J Hand Surg [Br]. Nov 1988;13(4):469-73. [Medline].

  10. Ip KC, Wong LY, Yu SJ. Dorsal dislocation of the metacarpophalangeal joint of the thumb: a case report. J Orthop Surg (Hong Kong). Apr 2008;16(1):124-6. [Medline]. [Full Text].

  11. Maheshwari R, Sharma H, Duncan RD. Metacarpophalangeal joint dislocation of the thumb in children. J Bone Joint Surg Br. Feb 2007;89(2):227-9. [Medline].

  12. Marcotte AL, Trzeciak MA. Nonoperative treatment for a double dislocation of the thumb metacarpal: a case report. Arch Orthop Trauma Surg. Mar 2008;128(3):281-4. [Medline].

  13. Orozco JR, Rayan GM. Complex dorsal metacarpophalangeal joint dislocation caused by interosseous tendon entrapment: case report. J Hand Surg [Am]. Apr 2008;33(4):555-7. [Medline].

  14. Peterson JJ, Bancroft LW. Injuries of the fingers and thumb in the athlete. Clin Sports Med. Jul 2006;25(3):527-42, vii-viii. [Medline].

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Further Reading

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Keywords

metacarpophalangeal joint dislocation, finger dislocation, finger joint, finger joint dislocation, finger sprain, thumb dislocation, thumb sprain, dislocated thumb, dislocated finger, sprained finger, sprained thumb, jammed finger, MCP sprain, MCP dislocation, MCP joint dislocation, MCP joint sprain, MPJ sprain, MPJ dislocation

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Contributor Information and Disclosures

Author

Matthew Gammons, MD, Assistant Clinical Professor, Department of Family and Community Medicine, Medical College of Wisconsin; Medical Director, Castleton State College; Consulting Staff, Vermont Orthopaedic Clinic and Killington Medical Clinic
Matthew Gammons, 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 American Society of Mechanical Engineers
Disclosure: Nothing to disclose.

Medical Editor

Anthony J Saglimbeni, MD, Staff Physician, Family Practice Residency, Medical Director, Center for Sports Medicine, O'Connor Hospital; Private Practice
Disclosure: Nothing to disclose.

Pharmacy Editor

Francisco Talavera, PharmD, PhD, Senior Pharmacy Editor, eMedicine
Disclosure: Nothing to disclose.

Managing Editor

Russell D White, MD, Professor of Medicine, Department of Community and Family Medicine, University of Missouri-Kansas City School of Medicine, Truman Medical Center Lakewood
Disclosure: Nothing to disclose.

CME Editor

Jon B Whitehurst, MD, Clinical Instructor of Surgery, University of Illinois College of Medicine; Partner and Executive Board Member, Rockford Orthopedic Associates; Orthopedic Chairman, Rockford Memorial Hospital
Jon B Whitehurst, MD is a member of the following medical societies: American Academy of Orthopaedic Surgeons, American Orthopaedic Society for Sports Medicine, and Arthroscopy Association of North America
Disclosure: Nothing to disclose.

Chief Editor

Craig C Young, MD, Professor, Departments of Orthopedic Surgery and Community and Family Medicine, Medical Director of Sports Medicine, Sports Medicine Fellowship Director, 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, Phi Beta Kappa, and Wilderness Medical Society
Disclosure: Nothing to disclose.

 
 
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