Zone III Small Finger Both Flexor Tendon Rupture after a Single Corticosteroid Injection: A Unique Case Report.

INTRODUCTION: Finger flexor tendon injuries commonly occur as a result of direct trauma. On rare occasions, spontaneous ruptures can occur. Many pathologic processes have been described in the literature contributing to spontaneous finger flexor tendon ruptures, with most leading to progressive weakening of the tendon until it ultimately fails. We present a unique case of a Zone III spontaneous combined flexor digitorum superficialis (FDS) and flexor digitorum profundus (FDP) rupture of the small finger in a 66-year-old female, 3 weeks after a corticosteroid injection for trigger finger. To the best of our knowledge, this is the only report of a small finger combined FDS/FDP rupture after a single corticosteroid injection.

CASE REPORT: A 66-year-old female presented with the inability to flex her right small finger for the past 4 days, after injuring it at the gym. She had previously received one corticosteroid injection into her small finger for the treatment of the trigger finger approximately 3 weeks prior. Magnetic resonance imaging revealed rupture of both finger flexors of the small finger at the level of the mid metacarpal shaft, with at least 1 cm of separation. Reconstruction of the small finger FDP was performed using the FDS as an intercalary graft without complication. At the 6-week follow-up visit, she was doing well, able to flex both her proximal and distal interphalangeal joints actively. She experienced some stiffness but had an almost complete range of motion. She was pleased with the results at that time.

CONCLUSION: This case demonstrates a unique complication of non-operative treatment of trigger finger. While it will ultimately not change our institution's treatment of trigger finger, it will lead to our team becoming more aware of the impact of corticosteroid injections and the need to inform patients to ease back into physical activity following injection.