A 37-year-old male patient who is a construction worker presents after suffering a thumb injury during a fall 1 week ago. He has pain and bruising on the ulnar side of the thumb metacarpophalangeal (MCP) joint. There is greater than 40° of valgus laxity, both in extension and 30° of MCP joint flexion. There is no appreciable endpoint during stress testing. Plain radiographs show no fracture. Which of the following is the most appropriate next step in management?

• Repair of the thumb ulnar collateral ligament
• Thumb spica cast with repeat examination in 2 weeks
• Closed reduction and transarticular pinning of the thumb MCP joint
• Reconstruction of the thumb ulnar collateral ligament with a tendon graft