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Metacarpophalangeal Joint Dislocation
Article Last Updated: Aug 7, 2008
AUTHOR AND EDITOR INFORMATION
Section 1 of 12  
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 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
Editors: Anthony J Saglimbeni, MD, Staff Physician, Family Practice Residency, Medical Director, Center for Sports Medicine, O'Connor Hospital; Private Practice; Francisco Talavera, PharmD, PhD, Senior Pharmacy Editor, eMedicine; 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; 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; 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
Author and Editor Disclosure
Synonyms and related 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
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.
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Resource Center Exercise and Sports Medicine
Resource Center Joint Disorders
Specialty Site Orthopaedics
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.
Contusions
Gamekeeper's Thumb
Jammed Finger
Phalangeal Fractures
Skier's Thumb
Lab Studies
- Laboratory studies generally are not indicated in the diagnosis of metacarpophalangeal (MCP) joint injuries.
Related Medscape topic:
Specialty Site Pathology & Lab Medicine
Imaging Studies
- Static x-ray films
- 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.
- Stress x-ray films
- Stress views should not be performed in skeletally immature patients in whom growth plate injury is more likely.
- Obtain stress x-ray films only after static x-ray films so that a nondisplaced avulsion fracture is not converted into a displaced fracture.
- Joint position during stress views is controversial, and some advocate full extension while others recommend flexion, wherein the ligament normally is taut.
- Thumb MCP joint laxity greater than 30-35° is usually associated with complete collateral ligament rupture.
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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.
- 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
- Use local anesthesia, intravenous sedation, or regional block.
- Apply a dorsally directed force to the volar base of the proximal phalanx, 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.
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Anesthesia, Regional, Digital Block
Local Anesthetic Agents, Infiltrative Administration
Toxicity, Local Anesthetics
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Specialty Site Surgery
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.10 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.
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.
The goals of pharmacotherapy are to reduce morbidity and prevent complications.
Drug Category: Anesthetics
Local anesthetic may be injected directly into the MCP joint when performing stress testing or closed reduction.
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Local Anesthesia and Regional Nerve Block Anesthesia
Toxicity, Local Anesthetics
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Specialty Site Surgery
| Drug Name | Lidocaine HCL1% (Xylocaine, Dilocaine, Anestacon) |
|---|
| Description | Blocks both the initiation and conduction of nerve impulses by decreasing the neuronal membrane's permeability to sodium ions, causing a blockade of conduction. |
|---|
| Adult Dose | 1 mL SC or intra-articularly
Maximum: 4.5 mg/kg SC; not to exceed 300 mg |
|---|
| Pediatric Dose | <3 years: 3 mg/kg SC maximum; not to exceed 75-100 mg
0.5-1 mL SC or intra-articularly
>3 years: Administer as in adults |
|---|
| Contraindications | Documented hypersensitivity to amide-type local anesthetics; avoid in Adams-Stokes syndrome and Wolff-Parkinson-White syndrome; avoid in severe sinoatrial (SA), atrioventricular (AV), or intraventricular block, if an artificial pacemaker is not in place |
|---|
| Interactions | None reported for intra-articular administration |
|---|
| Pregnancy | B - Fetal risk not confirmed in studies in humans but has been shown in some studies in animals
|
|---|
| Precautions | Use the solution without preservatives; caution in patients with heart failure, hepatic disease, hypoxia, hypovolemia or shock, respiratory-depression, and bradycardia; may increase the risk of CNS and cardiac side effects in elderly patients; high plasma concentrations can cause seizures, heart block, and AV-conduction abnormalities |
|---|
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.
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Specialty Site Orthopaedics
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.
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).
Medical/Legal Pitfalls
- Any patient with a history of a closed-hand injury should obtain x-ray films, so that the treating physician does not overlook joint subluxation or a subtle fracture. X-ray films should include both the proximal and distal joints neighboring the area of suspected injury.
- Before stressing an injured joint, static x-ray films should be obtained, so that a nondisplaced avulsion fracture is not converted into a displaced fracture.
- The neurovascular status should be documented before performing a reduction or using a local anesthetic.
- Longitudinal traction or hyperextension should never be applied to simple metacarpophalangeal (MCP) joint dislocations. This may entrap the metacarpal head in already tightened soft tissues, or it may pull the volar plate into the joint, converting a simple dislocation into a complex dislocation.
Related Medscape topic:
Resource Center Joint Disorders
Resource Center Medical Malpractice and Legal Issues
Specialty Site Neurology & Neurosurgery
Specialty Site Orthopaedics
Special Concerns
- Pediatric population
- Skeletally immature children are more likely to sustain growth plate injuries than ligament or volar plate ruptures.
- Injured joints should not be stress tested (clinically or radiographically) for fear of displacing a physeal injury.
- Parents should be advised that premature closure of the physis may occasionally occur after these injuries.
Related Medscape topics:
Resource Center Exercise and Sports Medicine
Specialty Site Pediatrics
The authors and editors of eMedicine gratefully acknowledge the contributions of previous author, David R Steinberg, MD, to the development and writing of this article.
| Media file 1:
Metacarpophalangeal joint dislocation of the small finger. Posteroanterior radiograph demonstrates loss of joint space. |
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Media type: X-RAY
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| Media file 2:
Metacarpophalangeal joint dislocation of the small finger. Oblique radiograph best demonstrates dorsal dislocation of proximal phalanx. |
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Media type: X-RAY
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| Media file 3:
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. |
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Media type: X-RAY
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Metacarpophalangeal Joint Dislocation excerpt Article Last Updated: Aug 7, 2008
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