Mallet Finger Caused by a Villonodular Synovitis: A Case Report and Literature Review

Introduction: Mallet finger is a frequent lesion. It represents 2% of sports emergencies and is the most common closed tendon injury seen in contact sports or in work environment. It occurs always after a traumatic etiology. Our case is atypical and exceptional, because it is caused by a villonodular synovitis, condition which has been never reported in the literature. Case Report: A 35-year-old woman presented for a mallet finger deformity of the second right finger. When questioned, the patient did not recall any trauma; she reported that the deformation had developed gradually over a period of more than 20 days preceding the definitive deformation of the finger into a classic mallet finger. She reported experiencing mild pain before the deformation, with burning sensations at the third finger phalanx. On palpation, we noted the presence of nodules at the level of the distal interphalangeal joint and on the dorsal face of the second phalanx of the concerned finger. The X-ray examination showed the classic mallet finger deformity, with no bone associated lesion. The diagnosis of pigmented villonodular synovitis (PVNS) was suspected intraoperatively by the presence of hemosiderin into the tendon sheath and distal articulation. The excision of the mass with tenosynovectomy and reinsertion of the tendon was the essential elements of the treatment. Conclusion:A mallet finger caused by a villonodular tumor is an exceptional condition with local aggressivity and uncertain prognosis. A meticulous surgical procedure could achieve an excellent result. Complete tenosynovectomy, tumor surgical resection, and tendon reinsertion were the mainstay of treatment for a long-lasting excellent result. Keywords: Non-traumatic mallet finger, villonodular tumor of extensor tendon sheat, pigmented villonodular tenosynovitis, extensor tendon injury, finger deformity.