Metacarpophalangeal Joint Dislocation Clinical Presentation

Updated: May 24, 2017
  • Author: Matthew Gammons, MD; Chief Editor: Craig C Young, MD  more...
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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 dislocation [8] 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.

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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 thumb  [9]

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.

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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.

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