Finger osteochondroma presenting as non-traumatic mallet finger in pediatric: A case report

A terminal extensor tendon disruption, with or without bony avulsion, may lead to a mallet deformity. In most cases, trauma precedes deformity. Non-traumatic causes are less probable. Several reports showed non-traumatic causes include villonodular tumors or chronic inflammation/infection. Conversely, osteochondroma, a benign tumor, typically develops from the growth plate of the long bones during the first two decades of life.

We describe an unusual case of osteochondroma and mallet deformity in a child's finger. The child was only 4 years old at the time of the first presentation, and there was no clear injury before the symptom. The parent reported that the left little finger was crooked. Over the past year, the painless deformity has gradually progressed. At the physical examination, a palpated bony mass was found proximal to the angulated DIP joint. A radiograph was inconclusive and suggested an old fracture of the middle phalanx. Intraoperatively, a sessile-type exostosis at the epi-metaphysis of the middle phalanx pushed the intact terminal extensor ulnarwards.

After removing the exostosis, the biopsy confirmed the presence of osteochondroma. We reconstruct the terminal extensor tendon and skin. During the 2-year follow-up, there was no evidence of infection, deformity relapse, or tumor recurrence.

Our goal is to raise awareness of osteochondroma, an extremely rare cause of a non-traumatic mallet finger in a very young child. Surgical resection remains the mainstay treatment for the tumor, with additional soft tissue reconstruction to overcome the secondary deformity.