Published: 19-08-2010, 12:06

Trigger thumb

Stenosing tenosynovitis of the thumb, more commonly known as “trigger thumb,” is one of the more common congenital abnormalities of the hand. It is rarely recognized in the first six months of life since children generally maintain their hand in a fist-clenched position, and because they are not as yet using their hand for two-handed activities. As the child begins to reach, grasp, and grip objects, it becomes apparent that the thumb does not fully extend at the interphalangeal joint. The deformity may manifest itself in periodic episodes of flexion deformity of the interphalangeal joint with occasional episodes of popping, clicking or full straightening of the finger.More commonly it is recognized when the thumb is persistently held in a position of interphalangeal joint flexion (Figure 3.27).
Trigger thumb

Figure 3.27. The clinical deformity and patho-anatomy of the trigger thumb.

The parents relate that the thumb does not fully straighten, and that the child has some difficulty in grasping. On examination, a palpable nodule is readily discerned at the metacarpophalangeal joint level, at or near the proximal metacarpophalangeal thumb crease. There is inability to extend the interphalangeal joint of the thumb. The palpable nodule is actually a thickened prominence arising from the flexor tendon to the thumb. As this nodule enlarges in size, it no longer is capable of passing through the flexor pulley, and complete extension of the thumb is impaired. Prior to the nodule reaching such size it may periodically pass through the tunnel, producing the characteristic “triggering” noticed by many parents. Although stretching exercises and occasionally cortisone injections have been tried, the vast majority of children will require surgical release of the flexor pulley. Surgical treatment has routinely resulted in complete correction in well over 95 percent of the cases.
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