Thumb CMC Arthroplasty

Thumb arthritis
Reproduced with permission from OrthoInfo. © American Academy of Orthopaedic Surgeons.

Thumb CMC arthroplasty is a treatment option for thumb arthritis, a type of osteoarthritis found at the carpometacarpal (CMC) joint located at the base of the thumb. The CMC joint gives the thumb a wide range of motion – up, down, and across the palm, as well the ability to pinch.

A joint is comprised of two bones, each covered with cartilage (hard slippery tissue that serves as a shock absorber to allow smooth movements). With osteoarthritis, the cartilage breaks down, which releases substances in the joint that cause inflammation and pain.

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Surgical Treatment Option: Thumb CMC Arthroplasty

Thumb CMC arthroplasty involves removing the small wrist bone that is part of the CMC joint and replacing it with a wrist flexor tendon.

  • During the procedure, a small incision (approximately 1.5 inches) is made over the CMC joint, and the trapezium wrist bone is removed.
  • A small incision is then made in the forearm to release a wrist flexor tendon. First it is attached to the base of the thumb metacarpal bone with a bone anchor, and then the remainder of the tendon is rolled into a ball and placed into the void left by the trapezium. This creates a cushion between the remaining bones.
  • The incisions are closed with absorbable sutures, and the hand is covered by dressing and cast to immobilize the wrist and a portion of the thumb.

Thumb CMC arthroplasty is performed under general anesthesia with a “block.” An IV will be started in the non-operative arm to deliver medicine that puts you to sleep, so you will be unconscious and unable to feel anything during surgery. Before going to the operating room, a “block” (additional anesthesia) will be injected into the arm for additional numbing, primarily for post-operative pain control. The hand may remain somewhat numb for up to a day after surgery.

Preparing for Thumb CMC Arthroplasty

  • Avoid taking anti-inflammatories or blood thinning medications (such as aspirin) for at least five days before surgery. In most cases, you will be able to resume taking these medications after your procedure.
  • Do not eat after midnight the night before. If you are diabetic, we will make every attempt to schedule your procedure as the first case of the day. You will be allowed to slowly resume eating right after surgery.
  • Arrange for a friend or family member to be there after surgery to receive your discharge instructions and drive you home.

What to Expect After Thumb CMC Arthroplasty

Cast and splint: It is important to keep the cast dry and out of direct spray when showering. Two weeks after surgery, you will have your first post-operative visit. At this visit, your plaster cast will be removed, and you will go to physical therapy to be fitted for a custom splint, which you will wear for four weeks.

Exercises and therapy: You will be given instructions for gentle exercises to perform at home. Formal therapy will begin six weeks after surgery.

Driving restrictions: You should not drive while taking pain medications and should minimize driving while the initial splint is on.

Back-to-work restrictions: If your job does not require use of the hand that was operated on, you may return to work after a week or two. However, if your job requires use of that hand, you will likely not be able to work for at least six weeks after surgery.

Results: Though you will be able to start using your hand and thumb six weeks after surgery, it can take up to six months to one year for the thumb to feel normal, and strength will continue to improve over several years. Long-term studies do not show any functional deficits with using the forearm flexor tendon, as there are other tendons that do the same job.