The locking finger is the common lesion especially on the thumb due to stenosing tenosynovitis of the flexor tendon, known as the trigger finger, however, it is rare that locking metacarpophalangeal joint of index finger from traumatic origin.
A case of locking index finger at the metacarpophalangeal joint caused from torn radial collateral ligament and capsule, which was pinched in between the metacarpal head and base of the proximal phalanx in the joint. Joint was locked´ in 30 degree flexion and 20 degree adduction and unable to, straighten his finger. Closed reduction under general anesthesia failed and resesction of the torn radial collateral lig and result gave full restoration of finger functions.
Main pathologic factor of the locking finger is the torn soft tissue interposing in the joint at dorsoradial side and the extensor aponeurosis formed by the fibers of interossei and lumbrical over the joint plays important role -to maintain the soft tissue in the joint, checking it on each flexion of the joint.
The transverse fibers of aponeurotic sleeve shift from the dorsum of the joint at metacarpal head down to open gap between the metacarpal head and base of proximal phalanx with maximum pressure down to the gap where interposed edge of torn soft tissue locate and assure´ the interposition.
Only the answer to reduce this kind of locking of the finger is the operative repair of torn lig and capsqle or resection of those.
Previously reported cases of locking finger has been reviewed and they are classified as two major groups. One is the soft tissue interposition in the joint per se at the dorsum and another causing volar accessory plate limit its normal .range of motion to stretch from various factors.
All of these cases had good result of recovery after operative correction of pathological factors but unsatisfactory result caused from the cases who had conservative measure for treatment, remaining about ten degree limitation of extension of the finger permanently.
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