Sesamoid arthritis mimicking trigger thumb

This article presents a case of undiagnosed sesamoid arthritis with coexisting trigger thumb. A 25-year-old woman presented with a 2-year history of metacarpophalangeal joint pain and triggering of the thumb. She was a right-handed bank employee and recalled a trivial thumb sprain. The pain improved slightly while on medication, but the triggering recurred 1 month after the steroid injection. Six months after the first visit, she underwent A1 pulley release surgery for the triggering without a more detailed evaluation such as radiographs or sonographs. Intraoperatively, no definite abnormalities in the fibrous flexor sheath or flexor tendon were observed. The triggering resolved, but the pain persisted. One month postoperatively, a repeat physical examination was performed, and the painful region was localized to the radial sesamoid area. Radiography was then performed, which showed joint space narrowing of the sesamoid metacarpal head and sclerotic changes and spur formation on the metacarpal head. An additional diagnosis of sesamoid arthritis of the thumb was made and the pain finally resolved as a result of the sesamoidectomy. Orthopedic surgeons often overlook pathologies around the metacarpophalangeal joint, especially those related to triggering. A high index of suspicion and clinical findings consistent with intermittent mechanical obstruction and tenderness in the palmar aspect of the metacarpophalangeal joint warrant inclusion of sesamoid arthritis as a differential diagnosis for metacarpophalangeal joint pathology. Detailed physical examinations should be performed and proper radiographs taken in all patients with tenderness in the metacarpophalangeal joint even if triggering of the thumb is present.