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Abstract
The extension type locked metacarpophalangeal joint of the little finger is an extremely rare condition characterized by loss of flexion with little or no loss of extension. The most common cause for locking is entrapment of a strap of the ruptured palmar plate. We treated a locked metacarpophalangeal joint of the little finger due to a hyperextension injury. The mechanism of locking was a torn part of the palmar ligament that forcefully rides across the prominence of the radial condyle of the metacarpal bone together with the accessory collateral ligament. These dislocated parts of the ligament formed a constricting bundle that prevented closed reduction. Locking was released successfully by an open reduction using the dorsal approach of the metacarpophalangeal joint without complication.
Figures and Tables
Figure 1
Photograph of the patient shows flexion limitation of metacarpophalangeal joint motion (A) without limitation of extension (B).
Figure 2
Plain radiograph (A) and computed tomography (B) show a bony protrusion at the radiopalmar aspect of the radial condyle of the 5th metacarpal head (arrows).
Figure 3
T1-weighted coronal (A), T1-weighted axial (B) and T2-weighted sagittal magnetic resonance images (C) show a torn volar plate (arrows) constricting the radial condyle of the metacarpal bone. (D) A T2-weighted sagittal magnetic resonance image shows no protrusion of the volar plate in the joint.
Figure 4
Full range of motion at the metacarpophalangeal joint is observed three months after surgery. Extension (A) and flexion (B) of the metacarpophalangeal joint of the little finger.
Figure 5
The mechanism of locking. (A) Forced hyperextension of the metacarpophalangeal joint and the volar plate was ruptured at its proximal attachment. (B) Dorsal dislocation of the radial proximal palmar ligament (arrow). The ruptured radial proximal palmar ligament rode across the volar prominence of the radial condyle. (C, D) The dorsal dislocated volar plate (lines) rode across the volar prominence of the radial condyle (asterisks) with formation of a constricting bundle that prevented closed reduction.
References
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