Metacarpophalangeal Joint Dislocation
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.
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.
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.  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.
Glickel SZ, Barron OA, Eaton RG. Dislocations and ligament injuries in the digits. Green DP, Hotchkiss RN, Pederson WC, eds. Green’s Operative Hand Surgery. 4th ed. New York, NY: Churchill Livingstone; 1999. 772-807.
Neviaser RJ. Dislocations and ligamentous injuries of the digits. Chapman MW, ed. Operative Orthopaedics. 2nd ed. Philadelphia, Pa: Lippincott Williams & Wilkins; 1993. 1237-50.
Lourie GM, Gaston RG, Freeland AE. Collateral ligament injuries of the metacarpophalangeal joints of the fingers. Hand Clin. 2006 Aug. 22(3):357-64, viii. [Medline].
Zemel NP. Metacarpophalangeal joint injuries in fingers. Hand Clin. 1992 Nov. 8(4):745-54. [Medline].
Melone CP Jr, Beldner S, Basuk RS. Thumb collateral ligament injuries. An anatomic basis for treatment. Hand Clin. 2000 Aug. 16(3):345-57. [Medline].
Posner MA, Retaillaud JL. Metacarpophalangeal joint injuries of the thumb. Hand Clin. 1992 Nov. 8(4):713-32. [Medline].
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].
Inoue G, Miura T. Locked metacarpo-phalangeal joint of the thumb. J Hand Surg [Br]. 1988 Nov. 13(4):469-73. [Medline].
Beck JD, Klena JC. Closed reduction and treatment of 2 volar thumb metacarpophalangeal dislocations: report of 2 cases. J Hand Surg Am. 2011 Apr. 36(4):665-9. [Medline].
Vadala CJ, Ward CM. Dorsal Approach Decreases Operative Time for Complex Metacarpophalangeal Dislocations. J Hand Surg Am. 2016 Sep. 41 (9):e259-62. [Medline].
Dinh P, Franklin A, Hutchinson B, Schnall SB, Fassola I. Metacarpophalangeal joint dislocation. J Am Acad Orthop Surg. 2009 May. 17(5):318-24. [Medline].
Maheshwari R, Sharma H, Duncan RD. Metacarpophalangeal joint dislocation of the thumb in children. J Bone Joint Surg Br. 2007 Feb. 89(2):227-9. [Medline].
Marcotte AL, Trzeciak MA. Nonoperative treatment for a double dislocation of the thumb metacarpal: a case report. Arch Orthop Trauma Surg. 2008 Mar. 128(3):281-4. [Medline].
Orozco JR, Rayan GM. Complex dorsal metacarpophalangeal joint dislocation caused by interosseous tendon entrapment: case report. J Hand Surg [Am]. 2008 Apr. 33(4):555-7. [Medline].
Peterson JJ, Bancroft LW. Injuries of the fingers and thumb in the athlete. Clin Sports Med. 2006 Jul. 25(3):527-42, vii-viii. [Medline].
Khursheed O, Haq A, Rashid S, Manzoor N, Shiekh S, Mushtaq M. Clinical Outcome of Metacarpophalangeal Joint Dislocation of the Thumb in Children: Case Series of 10 Patients. J Hand Microsurg. 2016 Apr. 8 (1):13-6. [Medline].
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, American Society of Mechanical Engineers
Disclosure: Received income in an amount equal to or greater than $250 from: Up to Date.
Francisco Talavera, PharmD, PhD Adjunct Assistant Professor, University of Nebraska Medical Center College of Pharmacy; Editor-in-Chief, Medscape Drug Reference
Disclosure: Received salary from Medscape for employment. for: Medscape.
Russell D White, MD Clinical Professor of Medicine, Clinical Professor of Orthopedic Surgery, Department of Community and Family Medicine, University of Missouri-Kansas City School of Medicine, Truman Medical Center-Lakewood
Russell D White, MD is a member of the following medical societies: Alpha Omega Alpha, American Academy of Family Physicians, American Association of Clinical Endocrinologists, American College of Sports Medicine, American Diabetes Association, American Medical Society for Sports Medicine
Disclosure: Nothing to disclose.
Craig C Young, MD Professor, Departments of Orthopedic Surgery and Community and Family Medicine, Medical Director of Sports Medicine, 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
Disclosure: Nothing to disclose.
Anthony J Saglimbeni, MD President, South Bay Sports and Preventive Medicine Associates; Private Practice; Team Internist, San Francisco Giants; Team Internist, West Valley College; Team Physician, Bellarmine College Prep; Team Physician, Presentation High School; Team Physician, Santa Clara University; Consultant, University of San Francisco, Academy of Art University, Skyline College, Foothill College, De Anza College
Anthony J Saglimbeni, MD is a member of the following medical societies: California Medical Association, Santa Clara County Medical Association, Monterey County Medical Society
Disclosure: Received ownership interest from South Bay Sports and Preventive Medicine Associates, Inc for board membership.
The authors and editors of Medscape Reference gratefully acknowledge the contributions of previous author, David R Steinberg, MD, to the development and writing of this article.
Metacarpophalangeal Joint Dislocation
Research & References of Metacarpophalangeal Joint Dislocation|A&C Accounting And Tax Services