Metacarpophalangeal Joint Dislocation 

Updated: May 24, 2017
Author: Matthew Gammons, MD; Chief Editor: Craig C Young, MD 

Overview

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]

MCP joint dislocation is seen in the image below.

Metacarpophalangeal joint dislocation of the small Metacarpophalangeal joint dislocation of the small finger. Posteroanterior radiograph demonstrates loss of joint space.

For patient education resources, see the Bone, Joint, and Muscle Center and Breaks, Fractures, and Dislocations Center, as well as Finger Dislocation, Broken Finger, and Sprains and Strains.

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.

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.

 

Presentation

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.

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.

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.

 

DDx

 

Workup

Laboratory Studies

Laboratory studies generally are not indicated in the diagnosis of metacarpophalangeal (MCP) joint injuries.

Imaging Studies

Static x-ray films (see the images below)

Metacarpophalangeal joint dislocation of the small Metacarpophalangeal joint dislocation of the small finger. Posteroanterior radiograph demonstrates loss of joint space.
Metacarpophalangeal joint dislocation of the small Metacarpophalangeal joint dislocation of the small finger. Oblique radiograph best demonstrates dorsal dislocation of proximal phalanx.
Metacarpophalangeal joint dislocation of the small Metacarpophalangeal joint dislocation of the small finger. Dorsally dislocated proximal phalanx is obscured by other digits. Note that the small finger metacarpal sits palmar to the other metacarpals.

Obtain anteroposterior, lateral, and oblique radiographic views. Brewerton views (MCP joint flexed 65°, with the dorsum of the proximal phalanx flat against the radiograph cassette and the beam angled 15° ulnar to radial) profile the collateral recesses and are helpful for collateral ligament avulsion fractures.

Obtain a lateral view of the injured digit, not a lateral view of the hand.

Prereduction and postreduction x-ray films are necessary to demonstrate associated fractures and joint congruency.

An incongruent joint can be caused by interposed soft-tissue or gross instability.

Joint subluxation after reduction is associated with interposed soft-tissue or severe capsular injury.

Procedures

Closed reduction of hyperextension – Simple dorsal dislocation

Use local anesthetic or intravenous sedation.

Apply pressure over the dorsal proximal phalanx, gently pushing in a palmar and distal direction, while simultaneously placing the metacarpophalangeal joint dislocation (MCP) joint into flexion.

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Flexing the wrist initially may aid reduction by relaxing the flexor tendons.

Never use longitudinal traction because this may entrap the metacarpal head in already tightened soft tissues or pull the volar plate into the joint, converting a simple dislocation into a complex dislocation.

Postreduction x-ray films confirm satisfactory reduction.

Maintain reduction in dorsal splint with the MCP joint flexed 30º.

Closed reduction of the thumb MCP joint – Dorsal dislocation

Closed reduction may be performed with local anesthesia, intravenous sedation, or regional block.

Apply a distal and volarly directed force to the dorsal base of the proximal phalanx, followed by placement of the MCP joint in mid flexion.

Postreduction x-ray films confirm satisfactory reduction.

Closed reduction of the thumb MCP joint – Volar dislocation

Most dorsal dislocations require open reduction owing to the presence of interposed structures: dorsal capsule, volar plate, extensor pollicis longus (EPL), extensor pollicis brevis (EPB).

Consider attempts at closed reduction if sesamoids are not interposed on radiographs or any of the following physical examination findings are present[10] :

  • No palpable EPL on initial examination

  • Radial or ulnar displacement of the EPL or EPB

  • Paradoxical MCP joint flexion and interphalangeal joint extension with attempted MCP extension

Use local anesthesia, intravenous sedation, or regional block.

Apply a dorsally directed force to the volar base of the proximal phalanx with hyperflexion at the MCP joint, followed by placement of the MCP joint in extension.

Postreduction x-ray films confirm satisfactory reduction.

Closed reduction of the locked thumb MCP joint

Occasionally, instillation of local anesthetic directly into the joint distends the capsule enough to allow gentle correction of the hyperextension deformity.

This should then be immobilized in approximately 20° of MCP joint flexion.

 

Treatment

Acute Phase

Rehabilitation Program

Occupational Therapy

Finger metacarpophalangeal (MCP) joint collateral ligament sprains should not be overtreated. First-degree sprains may require a brief period of protection, usually consisting of buddy taping for 2-3 weeks. Second-degree sprains are immobilized in mid flexion for 3 weeks.

Finger MCP joint hyperextension injuries may be treated by gently flexing the proximal phalanx and immobilizing the MCP joint in 30° of flexion for 2-3 weeks. A dorsal extension-block splint protects the healing volar plate while allowing active flexion of the finger. Early protected motion minimizes postinjury stiffness.

Thumb MCP joint hyperextension injuries ("locked MCP joint") are immobilized in 20° MCP joint flexion for 3 weeks.

After closed reduction, a dorsal extension-block splint, including the wrist, is used for at least 3 weeks in MCP joint dorsal dislocations. Active motion within the splint is started during the first week. Following closed reduction, the thumb is immobilized in a forearm-based thumb spica splint or cast with the MCP joint in extension for 4-6 weeks in thumb MCP joint volar dislocations.

Thumb radial collateral ligament injuries may be treated in a forearm-based or hand-based thumb spica cast for 4 weeks.

Surgical Intervention

After open reduction surgical repair, postoperative immobilization and therapy are similar to those that are recommended after closed reduction. In finger MCP joint collateral ligament injuries, surgical repair is indicated for gross instability (third-degree sprain) or a significantly displaced or rotated avulsion fracture.

MCP joint complex dorsal dislocations require open reduction in the operating room. This reduction may be accomplished with a palmar or dorsal approach. A dorsal longitudinal incision affords easy visualization of the interposed volar plate and avoids the digital neurovascular bundles that are more susceptible to injury with the palmar approach.

Volar MCP joint dislocations are extremely rare. The volar plate or dorsal capsule may be interposed into the joint, which usually requires open surgical reduction. Immobilization for 3-4 weeks in extension is recommended after successful reduction.

In thumb MCP joint dorsal dislocations, open reduction through a dorsal approach is indicated for failed closed reduction.[11] A dorsal approach is also used for failed closed management of a locked thumb MCP joint injury. In thumb MCP joint volar dislocations, surgical repair should be considered for chronic dislocations or when postreduction radiographs demonstrate persistent volar subluxation of the MCP joint. In thumb radial collateral ligament injuries, significant laxity (>30°) or volar subluxation is an indication for surgical repair.

A review of 21 patients with metacarpophalangeal dislocations reported that operative time was longer for the patients using the volar approach when compared to the dorsal approach and that 42% of the patients who underwent the volar approach required a second dorsal approach.[12]

Consultations

Immediate consultation with an orthopedic or hand surgeon is indicated for open or irreducible dislocations or when neurovascular compromise of the digit is present. After successful closed reduction, follow-up within 1 week should be arranged with an orthopedic or hand surgeon.

Recovery Phase

Rehabilitation Program

Occupational Therapy

After the appropriate immobilization period, progressive hand therapy is initiated.

  • Finger MCP joint collateral ligament: Second- and third-degree sprains are protected with buddy taping for an additional 3 weeks.

  • Finger MCP joint hyperextension injuries: The injured digit is buddy taped to an uninjured finger for an additional 2-3 weeks.

  • MCP joint dislocations: Progressive motion and gradual weaning from the splint are performed over 3 weeks.

  • Thumb radial collateral ligament: Protected motion in flexion/extension and gradual weaning from the splint are performed over 2 weeks.

Surgical Intervention

Significant collateral ligament laxity that interferes with hand function may require surgical reconstruction after an appropriate time period for normal healing has lapsed. Excessive joint contractures unresponsive to occupational therapy may require surgical release.

 

Medication

Medication Summary

The goals of pharmacotherapy are to reduce morbidity and prevent complications.

Anesthetics

Class Summary

Local anesthetic may be injected directly into the MCP joint when performing stress testing or closed reduction.

Lidocaine HCL1% (Xylocaine, Dilocaine, Anestacon)

Blocks both the initiation and conduction of nerve impulses by decreasing the neuronal membrane's permeability to sodium ions, causing a blockade of conduction.

 

Follow-up

Return to Play

As with most injuries return to play in patients with metacarpophalangeal (MCP) joint dislocation will vary somewhat by the injury and desired activity. Some athletes will be able to return immediately as long as the injury can be adequately protected in a splint or cast. After the acute MCP joint injury has healed (usually 3-6 wks), the injured finger can be buddy taped for 1-3 weeks for additional protection and comfort. Some MCP joint injuries may require up to 3 months for full return to sporting activity if they cannot be protected or if the desired sport requires full use of the injured finger.

Complications

Soreness and swelling may persist for many months after the capsule and ligaments have healed. Inadequate immobilization or early return to high-stress activities may result in ligamentous laxity or recurrent instability. Excessive immobilization or severe soft-tissue damage may lead to some joint stiffness, which is common after many of these injuries. Posttraumatic arthritis may occur after multiple closed reductions or unrecognized (chronic) dislocations. Digital nerve injury may occur during the volar surgical approach to the MCP joint.

Prevention

Although no studies exist with regard to efficacy, most practitioners recommend appropriate buddy taping of the injured finger to an uninjured digit during forceful activities, especially contact sports to help prevent reinjury.

Prognosis

The prognosis is good for MCP joint injuries that are recognized early and treated appropriately.

Patient Education

The patient needs to be educated regarding his or her particular injury and the methods of proper treatment to ensure adequate healing. Joint protection is a key concept for the patient to understand. Once healing has taken place through immobilization, the patient should be instructed in a progressive range-of-motion program to regain mobility of the injured joint(s).