gms | German Medical Science

Objectives: Locking of metacarpophalangeal (MCP) joint is commonly found in extension position of the thumb or mild flexion position of the index/middle finger. We experienced a rare case of vertical locking of the little finger in a young woman and performed manual reduction without anesthesia.

Method: A 16-year-old woman was injured her left little finger by iron dumbbell during muscle training. The MCP joint of the left little finger was locked with approximately 90 degrees-flexion position and could not be extended actively or passively. X-ray revealed that the MCP joint was over-flexed. Therefore, we diagnosed with vertical locking of the MCP joint of the left little finger, trying a manual reduction without anesthesia. Reduction was easily obtained by traction and extension of the MCP joint, and range of motion became normal both passively and actively. After the reduction, no splint was applied.

Results: Currently, six months after the injury, the patient complains of no pain or functional restriction even in sports activities.

Conclusion: Vertical locking of the MCP joint is uncommon. Other (not vertical) locking of the MCP joint, including extension position and moderate flexion position, is more common, and more difficult to be reduced. We believe that the vertical locking is easily reduced with gentle traction and extension of the MCP joint. This characteristic is completely different from other locking of the MCP joint. Therefore, anesthesia is unnecessary for the reduction. The cause of the locking is controversial; however, we support the theory that an abnormal volar projection on the metacarpal head accounted for the way in which the proximal phalanx palmar to it locked. If our theory is correct, splint is unnecessary because damage is little around the MCP joint. It is important to distinguish vertical locking from other locking before manual reduction. This can lead to simple and non-invasive treatment (gentle manual reduction without anesthesia).