Thumb CMC (carpometacarpal) joint fusion is an operation to permanently stiffen the joint at the base of the thumb by fusing the metacarpal to the trapezium. It provides a strong, pain-free thumb but sacrifices some motion.
An incision is made over the base of the thumb. The cartilage is removed from the CMC joint. The bones are positioned in a functional pinch position and fixed with screws, a plate, or wires. Bone graft may be used. The operation takes one to one and a half hours.
CMC fusion is typically recommended for younger, high-demand patients with CMC arthritis who need a strong, stable thumb for heavy manual work, or for post-traumatic arthritis. Trapeziectomy is more commonly chosen for older patients.
Thumb splinting, corticosteroid injection, activity modification. Trapeziectomy (with or without ligament reconstruction) is the main surgical alternative.
X-rays. Assessment of the neighbouring joints (STT joint must be healthy for fusion to work).
Strong, pain-free thumb for heavy grip and pinch. Grip strength is well preserved. Better for high-demand activities than trapeziectomy.
Reduced range of motion at the base of the thumb.
Placing the hand flat becomes difficult.
Failure to fuse. Risk approximately 5-10%.
Increased stress on neighbouring joints.
Sensory branches to the thumb.
Wound infection.
Screw prominence or loosening.
Regional or general anaesthesia.
Thumb cast for six to eight weeks. Hand therapy for grip strengthening. Full recovery three to six months.
X-rays at six weeks and three months.
Fusion provides a stronger thumb better suited for heavy manual work. Trapeziectomy preserves more motion but may have less pinch strength initially. The choice depends on your age, activity demands, and personal preference.