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DISLOCATION, FINGER METACARPOPHALANGEAL (MP) JOINT

Introduction

Metacarpophalangeal (MP) joint dislocations are rare, mainly owing to the strong connective tissue support around the joints and their basal location in the hand.1 The typical mechanism of injury is a fall on the outstretched hand (FOOSH) that causes forcible hyperextension of the MP joint, but a combination of translational and hyperflexion forces may also contribute.2 The index finger is the most frequently involved of the non-thumb digits, followed by the little finger, while MP dislocations in the long and ring fingers are extremely rare.1,3 Most MP dislocations are simple, meaning there is no soft tissue within the joint and the injury can usually be reduced by closed reduction, while complex dislocations occur far less frequently but require surgical intervention in most cases.3
 

Definitions

  • A MP joint dislocation occurs when the articular surface of the base of the proximal phalanx is displaced off the articular surface of the head of the metacarpal.

Hand Surgery Resource’s Dislocation Description and Characterization Acronym

D O C S

D – Direction of displacement

O – Open vs closed dislocation

C – Complex vs simple

S – Stability post reduction

D – Direction of displacement

  • The primary description and characterization of MP joint dislocations are done by noting the direction of the displacement of the proximal phalanx relative to the head of the metacarpal. 
  • The three possible directions of displacement are dorsal, lateral, and volar.4 
    • Dorsal MP dislocations are the most common.
    • Dorsal dislocations are further divided into two subtypes: 
      • The hyperextension subtype, where the volar base of the proximal phalanx catches on the dorsal edge of the metacarpal condyles in an extended position.
      • The bayonet subtype, where the base of the proximal phalanx is displaced on top of the neck of the metacarpal in a position parallel to the longitudinal axis of the metacarpal neck.
    • Volar dislocations can occur through either a hyperflexion or hyperextension injury.3
  • The degree of displacement of the proximal phalanx further characterizes MP dislocations. 
  • In a true complete dislocation, the articular surface of the proximal phalanx is no longer in contact with the articular cartilage of the metacarpal head. If there is partial contact of the cartilaginous surfaces, then this is not a true dislocation but rather a joint subluxation.4

O – Open vs closed

  • The majority of MP dislocations are closed; the skin is intact, and there is no route for bacteria to contaminate the joint space.
  • Open MP joint dislocations are extremely rare and have been found to only account for 8% of these injuries, but when present, urgent irrigation, debridement, open reduction, and ligament repair are required.5
    • As with closed MP dislocations, the usual mechanism of injury with open dislocations is hyperextension caused by a FOOSH, with the primary difference being the amount of force applied to the MP joint.1

C – Complex vs simple

  • Most MP joint dislocations are simple, meaning that reduction is easily achieved under digital anesthetic block and is not blocked by soft tissue being interposed in the joint between the proximal phalanx and metacarpal joint surfaces.3
  • Complex MP joint dislocations are rare but do occur, and most are dorsal dislocations.
    • In dorsal complex dislocations, the mechanism of injury is forceful hyperextension that leads to the volar plate being drawn dorsally between the proximal phalanx base and metacarpal head, thus becoming interposed dorsally in the joint.3,6
    • In volar complex dislocations, the dorsal capsule, distal insertion of the volar plate and/or collateral ligament can be avulsed and entrapped within the MP joint.3

S – Stability

  • A stable MP joint dislocation can be reduced and then put through an active range of motion (ROM) test under a local anesthetic block without redislocating.
  • Furthermore, a stable MP joint dislocation is stable to stress testing of the collateral ligaments in the radial/ulnar plane after reduction.

MP dislocation with special and complex features other than fractures

Anchor

Complex (irreducible) MP dislocation

  • Complex MP joint dislocations are very rare.
  • The mechanism of injury involves forced MP joint hyperextension and torsional stresses that draw the volar plate into the MP joint.3
  • The majority of these injuries are dorsal MP dislocations, while volar dislocations are even more rare.
    • Complex dorsal MP dislocations most commonly occur in the index and little fingers because they lack the stabilizing deep transverse metacarpal ligament.7
  • Complex volar MP dislocations frequently result from a proximal translational force acting on the proximal phalanx while the MP joint is in hyperflexion.7
    • In addition to the dorsal capsule possibly being interposed in the joint, the distal insertion of the volar plate and/or collateral ligament can also be avulsed and entrapped within the MP joint.3
  • Physical characteristics of a complex MP dislocation include a palpable metacarpal head, slight hyperextension of the proximal phalanx base, dimpling of the volar skin near the dislocated joint, and slight ulnar deviation of the affected digit.6

Imaging

  • X-ray
    • A true lateral view is most useful for visualizing these injuries.
    • A widened joint space and presence of a sesamoid bone within this space may be indications of a complex MP dislocation.6
  • MRI

Treatment

  • Early diagnosis of complex MP joint dislocations is very important.
  • Ideally, this is followed by open reduction and surgical anatomic repair of the collateral and tendon injuries.7
  • Postoperatively, early motion with dynamic extension splint helps improve the post-injury function.

Complications

  • Stiffness
  • MP joint pain
  • Persistent deformity
  • Impaired ROM
  • Digital nerve damage
  • Osteoarthritis

Outcome

  • Early diagnosis, surgical repair, and therapy will usually give a positive functional outcome, but some limited ROM is to be expected.

Related anatomy3

  • Extensor tendon – central slip and lateral bands
  • Flexor tendons
  • Dorsal capsule
  • Proper collateral ligament
  • Accessory collateral ligament
  • Volar plate
  • Neurovascular bundle
  • Transverse metacarpal ligament
  • Abductor digiti minimi 
  • Natatory ligament
  • Osteology of the head of the middle phalanx and base of the distal phalanx

Overall Incidence

  • Traumatic dislocations of the MP joint are believed to be rare injuries and are less common than proximal interphalangeal (PIP) and distal interphalangeal (DIP) dislocations; however, some experts suspect that many cases are not reported and that the true incidence is actually higher.3
  • The index finger is the most frequently involved non-thumb digit, followed by the little finger. MP dislocations in the long and ring fingers are extremely rare.8,9
  • Complex MP joint dislocations are very uncommon.

Related Injuries/Conditions

  • Fractures of the proximal phalanx
  • Fractures of the metacarpal
  • Collateral ligament injuries
  • Volar plate injuries
  • Central slip ruptures

Work-up Options

  • Delayed and missed diagnoses are common in MP dislocations due to their low incidence and a lack of obvious radiographic signs, so clinical suspicion must be high.10
  • X-ray
    • The oblique view appears to be most helpful for diagnosing MP dislocations. On lateral and anteroposterior views, there may be an overlap of the adjacent joints or metacarpal head and proximal phalanx base, respectively.2
    • Complex dislocations usually present with a widened joint space indicative of an interposed volar plate within the MP joint.3
  • MRI
ICD-10 Codes

  • DISLOCATION, FINGER METACARPOPHALANGEAL (MP) JOINT

    Diagnostic Guide Name

    DISLOCATION, FINGER METACARPOPHALANGEAL (MP) JOINT

    ICD 10 Diagnosis, Single Code, Left Code, Right Code and Bilateral Code

    DIAGNOSISSINGLE CODE ONLYLEFTRIGHTBILATERAL (If Available)
    DISLOCATION FINGER: MCP Joint    
    - INDEX S63.261_S63.260_ 
    - MIDDLE S63.263_S63.262_ 
    - RING S63.265_S63.264_ 
    - LITTLE S63.267_S63.266_ 

    Instructions (ICD 10 CM 2020, U.S. Version)

    THE APPROPRIATE SEVENTH CHARACTER IS TO BE ADDED TO EACH CODE FROM CATEGORY S63, S64, S65 AND S69
    A - Initial Encounter
    D - Subsequent Routine Healing
    S - Sequela

    ICD-10 Reference

    Reproduced from the International statistical classification of diseases and related health problems, 10th revision, Fifth edition, 2016. Geneva, World Health Organization, 2016 https://apps.who.int/iris/handle/10665/246208

Clinical Presentation Photos and Related Diagrams
MP Joint Stability Evaluation
  • Testing index MP joint ulnar collateral ligament (UCL) after reduction of dislocation. Force being applied in the direction of the arrow.
    Testing index MP joint ulnar collateral ligament (UCL) after reduction of dislocation. Force being applied in the direction of the arrow.
  • Testing index MP joint radial collateral ligament (RCL) after reduction of dislocation. Force being applied in the direction of the arrow.
    Testing index MP joint radial collateral ligament (RCL) after reduction of dislocation. Force being applied in the direction of the arrow.
Pathoanatomy Photos and Related Diagrams
Complex Finger MP Dislocations
  • Palmar view of complex dorsal MP dislocation
    Palmar view of complex dorsal MP dislocation
  • Dorsal view of complex dorsal MP dislocation
    Dorsal view of complex dorsal MP dislocation
Symptoms
History of trauma
Finger pain and swelling localized at the MP joint
Finger deformity at the MP joint
Typical History

The typical patient is a 32-year-old left-handed woman who experienced a FOOSH injury while jogging. The woman had been running on an unfamiliar trail at dusk when she failed to notice a large root protruding onto her path. She tripped on the root and landed on her outstretched hands, which hyperextended the MP joints of both hands and dislocated the MP joint of her left index finger. Immediately after the injury she noticed pain and swelling centralized around this joint and a slight deformity of the index finger.

Positive Tests, Exams or Signs
Work-up Options
Images (X-Ray, MRI, etc.)
X-ray MP Dislocations
  • Index MP dorsal dislocation. With this bayonet position there is a possibility that the volar plate is dorsally displaced or in the joint and will block a closed reduction, i.e. a complex dislocation.
    Index MP dorsal dislocation. With this bayonet position there is a possibility that the volar plate is dorsally displaced or in the joint and will block a closed reduction, i.e. a complex dislocation.
Treatment Options
Treatment Goals
  • Reduce the dislocation
  • Analyze the MP joint’s stability
  • Rehabilitate the injured finger to regain ROM and normal finger and hand function
Conservative
  • The majority of simple MP joint dislocations can be effectively treated with early closed reduction under local anesthesia. The anesthesia allows a gentle reduction with minimal pain and should be applied with a finger or wrist block.2,3,5
    • For dorsal dislocations, the reduction maneuver consists of flexing the wrist and placing gradual pressure distally and volarly over the proximal phalanx base.3,6
    • For volar dislocations, the reduction maneuver is similar except that the MP joint is flexed, and gentle pressure is applied to the volar surface of the proximal phalanx as it is brought into extension.3
  • Simple distraction as a reduction maneuver for MP joint dislocations is usually unsuccessful and can inadvertently convert a simple dislocation into a complex one.3
  • After reduction, performing an active ROM test and stress testing of the collateral ligaments is very important. This should be done before splinting. If the patient can actively extend and flex the finger almost normally without the finger redislocating, and if the collateral ligaments are stable to stress testing, then splinting the finger in mild flexion for comfort is indicated.2
  • This static splinting can be discontinued quickly (7-10 days) and a buddy tape splint used. Buddy taping the injured finger to an adjacent finger allows early active ROM exercising which should provide the best opportunity for obtaining normal ROM and finger function.2
Operative
  • MP joint dislocations without fractures rarely need operative treatment.
  • Operative treatment is indicated when closed reduction fails and for open MP joint dislocations, complex (irreducible) dislocations, and lateral dislocations in young individuals with a completely torn collateral ligament that is unstable.2,5
  • Surgical treatment options include closed reduction and percutaneous pinning (CRPP) and open reduction and internal fixation (ORIF). 
  • At surgery, if the dorsal capsule or volar plate are interposed in the MP joint, they should be extracted and the collateral ligaments should be repaired if they are torn.11

 

  • ORIF: whether a dorsal or volar approach should be used is still a matter of debate.
    • The dorsal approach enables access to the dorsal capsule, the osteochondral injury on the metacarpal head, and the volar plate with an extremely low risk for neurovascular injury.3,7 If a volar plate rupture is also detected, it can be repaired through a separate volar incision.7
    • The volar approach involves a higher risk of digital nerve injury, but careful dissection allows for excellent visualization of the structures.3
      • The radial neurovascular bundle is invariably tented over the metacarpal head and lies immediately beneath the skin. Similarly, the ulnar neurovascular bundle is displaced in dislocations of the small MP joint. It can be easily damated if the incision is not made with great care.
      • Failure to recognize the very superficial position of the neurovascular bundle tender over the metacarpal head may lead to its division during surgical exposure of the joint.
    • A combined dorsal and volar approach may also be necessary for patients who present late (>3 weeks after injury).3
Hand Therapy

Post-treatment Management

  • Many patients with closed MP joint dislocations that are reduced early can potentially exercise their finger on their own.
  • However, patients with marked swelling and pain will need hand therapy to help reduce swelling and improve ROM and strength.
  • Surgically repaired complex MP dislocations, repaired collateral ligaments, and unstable MP dislocations will definitely need hand therapy, custom splinting, and dynamic extension splints.

−     After surgery, immobilization—usually with dorsal block splinting—should be maintained for ~2 weeks. After splint removal, occupational therapy consisting of passive and active ROM exercises should be initiated.1,5

Complications
  • Stiffness
    • The most common complication in MP joint dislocations, which may be due to soft-tissue trauma or prolonged immobilization.3
  • Pain
  • Residual deformity
  • Weak grip
  • Neurovascular bundle damage
  • Impaired ROM
  • Joint contracture
Outcomes
  • Simple MP joint dislocations that are treated early typically have an excellent outcome.2,11
  • However, all patients with MP joint dislocations should be warned that the MP joint on the injured side will likely remain slightly larger than the opposite MP joint because the stretched collateral ligaments are likely to heal with a little extra bulk (collagen).
  • Delaying surgical intervention for >3 months after injury has been associated with poorer outcomes.11
Video
MP Joint Stability Evaluation
Key Educational Points
  • Simple closed MP joint dislocations can be mobilized early and should get a good outcome with minimal loss of ROM and residual deformity.
  • Unstable MP joint dislocations require prolonged extension block splinting with continuous monitoring by hand therapy for splint adjustment, etc.
  • Open and complex MP joint dislocations require urgent surgical treatment.
  • The total ROM of the MP joint is greater than that of the PIP and DIP joints.3
References

New and Cited Articles

  1. Barrera-Ochoa, S, Nunez, JH and Mir, X. Isolated open metacarpophalangeal dislocation of the little finger. Hand Surg Rehabil 2018. [Epub] PMID: 30174199
  2. Ramzi, Z, Chafik, R, Madhar, M, et al. Volar metacarpophalangeal joint dislocation: A case report. Hand Surg Rehabil 2018. [Epub] PMID: 29853350
  3. Dinh, P, Franklin, A, Hutchinson, B, et al. Metacarpophalangeal joint dislocation. J Am Acad Orthop Surg 2009;17(5):318-24. PMID: 19411643
  4. Merrell G, Slade J.F. Dislocations and ligament injuries in the digits. In: Wolfe, SW, Hotchkiss RN, Pederson WC, Kozin SH (eds): Green’s Operative Hand Surgery.  Philadelphia 2011: Elsevier Churchill Livingstone, pp. 291-332.
  5. Diaz Abele, J, Thibaudeau, S and Luc, M. Open metacarpophalangeal dislocations: literature review and case report. Hand (N Y) 2015;10(2):333-7. PMID: 26034455
  6. Stiles, BM, Drake, DB, Gear, AJ, et al. Metacarpophalangeal joint dislocation: indications for open surgical reduction.J Emerg Med 1997;15(5):669-71. PMID: 9348056
  7. Basar, H, Inanmaz, ME, Kose, KC, et al. Isolated dorsal approach for the treatment of neglected volar metacarpophalangeal joint dislocations. World J Orthop 2014;5(1):62-6. PMID: 24649416
  8. Patterson, RW, Maschke, SD, Evans, PJ, et al. Dorsal approach for open reduction of complex metacarpophalangeal joint dislocations. Orthopedics 2008;31(11):1099.PMID: 19226090
  9. Murali, M, Abdul Khader, F, Sunderajan, T, et al. A rare case of closed isolated dislocation of the third metacarpophalangeal joint of the hand. J Clin Orthop Trauma 2013;4(4):199-203.PMID: 26403883
  10. Vandeweyer, E, Zygas, P and Libotte, M. Palmar metacarpophalangeal joint dislocation. J Hand Surg Br 1998;23(4):546-7. PMID: 9726568
  11. Murase, T, Moritomo, H and Yoshikawa, H. Palmar dislocation of the metacarpophalangeal joint of the finger. J Hand Surg Br 2004;29(1):90-3. PMID: 14734082

Reviews

  1. Diaz Abele, J, Thibaudeau, S and Luc, M. Open metacarpophalangeal dislocations: literature review and case report. Hand (N Y) 2015;10(2):333-7. PMID: 26034455
  2. Dinh, P, Franklin, A, Hutchinson, B, et al. Metacarpophalangeal joint dislocation. J Am Acad Orthop Surg 2009;17(5):318-24. PMID: 19411643

Classics

  1. Miller PR, Evans BW, Glazer DA. Locked dislocation of the metacarpophalangeal joint of the index finger. JAMA1968;203(4):300-1. PMID: 569410
  2. von Raffler W. Irreducible dislocation of the metacarpophalangeal joint of the finger. Clin Orthop Relat Res1964;35:171-3. PMID: 5889166
  3. Wolfe, S. W., Hotchkiss, R. N., & Green, D. P. (2011). Greens operative hand surgery(6th ed., Vol. 1). Elsevier Churchill Livingstone.
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