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Trigger finger is uncommon among children and often caused by various lesions. We report a 5-year old girl who presented with chronic painless triggering of the right ring finger and normal X-ray. She underwent exploration of the finger flexor tendons and release of the A1 pulley. Lack of obvious pathology dictated further wound exploration which revealed a hidden osteochondroma of the proximal phalanx. We believe that adequate surgical wound exposure is necessary if no obvious cause of triggering could be seen in order to rule out an atypical osteochondroma even in the presence of normal X-rays.
Trigger finger is uncommon among children and much less common than congenital trigger thumb. It is estimated that the incidence of congenital trigger digits is 2.2% of all upper limb anomalies.
of all trigger digits in children congenital trigger fingers accounted for 14%, whereas trigger thumbs accounted for 86%. Congenital trigger thumb is believed to be caused by nodular thickening of the flexor tendon termed Notta's nodule.
Recherches sur affection particuliere des gaines tendineuses de la main, caracterisee par le developpement d'une nodosite sur le trajet des tendons flechisseurs des doigts et par l'empechement de leurs mouvements.
Such a nodule is usually not encountered in congenital trigger finger. A more proximal decussation of the flexor digitorum superficialis tendon, and ‘rosary bead-like’ thickening of the flexor tendons have been described as some of the causes of trigger finger in children.
We report a case of childhood trigger finger caused by proximal phalangeal osteochondroma.
1. Case report
A 5-year old girl presented with a 9-month history of painless triggering and locking of the right ring finger (Fig. 1) . The triggering increased in frequency and the patient had multiple episodes of recurrent locking of the finger in flexion at the metacarpophalangeal joint. The parents gave a possible remote history of trauma to the hand at the age of one year for which she had no treatment. Examination revealed a palpable ill-defined thickening of the flexor sheath and A3 pulley. The patient demonstrated triggering and finger locking in flexion. There was mild joint stiffness with normal neurovascular examination. X-rays of the hand showed no bony abnormality. Based on the history the patient was provisionally diagnosed with a possible closed flexor digitorum superficialis tendon slip rupture. She underwent exploration of the ring finger flexor tendons through a zigzag Brunner incision centered over the metacarpophalangeal joint. The A1 pulley was released. The flexor digitorum superficialis tendon was found to have edematous, mildly, thickened tenosynovium without tendon slip injury. Limited tenosynovectomy was done and the A3 pulley was also released. Lack of obvious pathology dictated further exploration of the wound which revealed a hidden cartilaginous mass close to A3 pulley measuring 1×1 cm and raised by 0.5 cm above the palmar surface of the proximal phalanx (Fig. 2) . The cartilaginous lesion was excised along with a segment of the periosteoum and cortical bone (Fig. 3) . Histopathological examination revealed mature lobulated cartilaginous tissue with overlaying fibrous cap and scant bony spicules within the mass which was consistent with osseous osteochondroma (Fig. 4) . Two months after surgery the patient was asymptomatic and the wound healed uneventfully. She had full range of motion of the ring finger and no further episode of triggering or locking occurred.
Figure 1A 5-year old girl has triggering and locking of the right ring finger.
Figure 4Mature benign cartilaginous tissue that was located within overlaying fibrous cap and has bony islands within the mass consistent with osseous osteochondroma.
reported tenosynovial osteochondroma of the tendon sheath presenting as a non-traumatic acute case of locked trigger finger. X-ray showed increased radiodensity in the soft tissue adjacent to the proximal phalanx. Minsinger et al
reported tenosynovial osteochondroma of the extensor tendon that appeared on the initial X-rays as a soft tissue ectopic mineralization in the dorsum of the wrist joint. Our case did not affect the flexor tenosynovium but originated from the bone. Yomamoto et al
reported a case of solitary phalangeal osteochondroma presenting as a small mass of the ring finger that was diagnosed on X-ray. The lesion was eccentrically located in the metaphysis of the proximal phalanx. Turret exostosis of the metacarpal neck was masked by the metacarpal head and could not be detected on repeat X-ray
but bone scan showed increased uptake. In our patient plain X-rays did not show any bony abnormality despite the presence of the lesion in the proximal phalanx. The osteochondromatous lesion was atypical because it was invisible on X-ray. In contrast to the typical cortical lesions or tenosynovial osteochondromas which are easier to diagnose on X-rays. Bizarre parosteal osteochondromatous proliferations of bone known as Nora's lesion
should be considered in the differential diagnosis. This lesion is visible on X-ray and has typical radiological features as a clearly pedunculated mass arising directly from cortical bone by a pedicle without medullary cavity involvement.
Our case illustrates a novel cause of trigger finger in contrast to other causes of trigger finger in children and congenital trigger thumb. Adequate surgical exposure should be used if no obvious cause of triggering is seen in order to rule out the presence of an atypical osteochondroma especially in the presence of normal X-rays.
Acknowledgements
We thank Dr J. Schnabel, MD (Pathologist) for his help in preparing the slides.
Recherches sur affection particuliere des gaines tendineuses de la main, caracterisee par le developpement d'une nodosite sur le trajet des tendons flechisseurs des doigts et par l'empechement de leurs mouvements.
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