IS Case 553: Thumb dislocation
Imaging Sciences URMC 2010
Publication Date: 2010-09-25
Findings
Three views of the right thumb showed dorsal dislocation of the first metacarpophalangeal (MCP) joint.
Diagnosis
Discussion
Dislocation of the thumb at the metacarpophalangeal joint can either be volar or dorsal. Dorsal dislocations are much more common than volar dislocations. Dorsal dislocations are usually caused due to fall on an outstretch hand or axial injury to the tip of the thumb causing the thumb to be hyperextended at the MCP joint. Volar dislocations are usually due to rupture of the collateral ligaments (proper collateral ligament or accessory collateral ligament) .
Radiographic findings can be helpful to determine if an MCP dislocation of the thumb can be reduced externally or if it would need surgery. Palmar dimpling or abnormal skin crease at the site of dislocation suggest an irreducible dislocation. If the sesamoids are seen between the metacarpal head and the proximal phalanx, it suggests a volar plate rupture and is not reducible externally. A widened joint space would indicate soft tissue interposition and a possible non-reducible dislocation.
Dorsal dislocations are easy to reduce compared to volar dislocations. A closed reduction is initially attempted on all MCP joint dislocations. After closed reduction, the stability of the ligaments is checked and if the MCP joint is stable, the thumb is placed in a cast in 20 degrees flexion and immobilized for about 10 days. Surgery is considered if closed reduction is not successful or if the MCP joint is unstable after reduction.
References
- Laub DE Jr, Priano SV. Hand, thumb fractures and dislocations. Emedicine, Sep 7, 2010. http://emedicine.medscape.com/article/1287814-overview.
- Dinh P, Franklin A, Hutchinson B, Schnall SB, Fassola I. Metacarpophalangeal joint dislocation. J Am Acad Orthop Surg. 2009 May;17(5):318-24.
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