PMC8316600_01
Adduction and flexion deformities on both thumbs.
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F1
Physical examination revealed adduction and flexion deformity of both thumbs (Figure 1).
Metacaropophalangeal joint instability on stress test. (A) Right thumb. (B) Left thumb. A markedly unstable metacarpophalangeal joint was noted in left thumb.
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F2
While a mild laxity of the ulnar collateral ligament was noted in the right thumb, a marked MPJ instability was noted in the left thumb (Figure 2). Stress radiography to determine instability revealed that the left thumb showed >60  of instability compared with the right side (Figure 2).
Flexor pollucis longus lengthening.
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F3
A longitudinal incision was created over the FCR tendon proximal to the wrist crease to expose the musculotendinous junction of the FPL, and L-shaped lengthening was performed (Figure 3).
Clinical photographs of both thumb at 2 years post-treatment. (A,B) Left thumb showing opposition with ring finger. (C) Right thumb showing widened narrow web space.
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F4
The thumb's opposition with other fingers was the ring finger with the left thumb and the little finger with the right thumb (Figure 4).