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How to Fuse a Thumb?

Published in Thumb Surgery 4 mins read

Fusing a thumb, medically known as thumb arthrodesis, is a surgical procedure designed to permanently join bones in the thumb to eliminate pain and stabilize the joint. This precise operation creates a solid bone connection, often performed to alleviate severe discomfort caused by conditions like advanced arthritis or significant joint instability.

Understanding Thumb Arthrodesis

Thumb arthrodesis is a surgical intervention where two bones forming a joint are permanently joined together, essentially becoming one solid bone. This procedure is primarily performed to relieve pain, correct deformities, and improve stability, especially in the thumb's carpometacarpal (CMC) joint at the base, which is crucial for pinch and grasp. While it eliminates motion at the fused joint, it provides a stable, pain-free platform for hand function.

The Surgical Procedure: A Step-by-Step Overview

The process of fusing a thumb involves meticulous bone preparation and fixation to ensure proper healing and stability.

  1. Anesthesia and Incision: The procedure typically begins with general anesthesia or regional anesthesia (like a nerve block) to ensure patient comfort. The surgeon then makes an incision over the affected thumb joint, usually at the base of the thumb for CMC joint fusion.
  2. Joint Preparation: Once the joint is exposed, the remaining cartilage surfaces are carefully removed to expose the underlying raw bone. This step is critical as it encourages the bones to grow together.
  3. Bone Shaping and Socket Creation: As a key part of the fusion process, surgeons create a socket by hollowing out the thumb's metacarpal bone. This precise hollowing allows for a stable fit. Concurrently, the trapezium (the wrist bone that articulates with the thumb's metacarpal) is shaped into a cone that fits inside the socket. This cone-in-socket configuration provides a strong, interlocking fit for optimal bone fusion.
  4. Internal Fixation: To maintain this precise alignment and prevent any movement while the bones fuse, a metal pin holds bones together. This pin acts as an internal splint, ensuring the bones remain in the correct position during the healing period. Other fixation methods, such as screws or plates, may also be used depending on the specific joint and surgeon's preference.
  5. Closure: After successful fixation, the surgical site is irrigated, and the incision is carefully closed with sutures. A sterile dressing is applied, followed by a cast or splint to further immobilize the thumb.

Post-Operative Care and Recovery

Recovery from thumb fusion surgery requires patience and adherence to post-operative instructions to ensure successful bone healing.

  • Immobilization: The thumb will typically be immobilized in a cast or splint for several weeks (e.g., 6-12 weeks) to allow the bones to fuse properly.
  • Pain Management: Pain medication will be prescribed to manage discomfort in the initial recovery phase.
  • Physical Therapy: Once the cast is removed, physical therapy is often recommended to regain strength in the surrounding muscles and improve overall hand function. While the fused joint itself won't move, therapy helps optimize the function of the remaining thumb and hand joints.
  • Activity Restrictions: Heavy lifting and strenuous activities involving the hand will be restricted for several months.

Why Is Thumb Fusion Performed? (Indications)

Thumb arthrodesis is primarily considered when non-surgical treatments have failed to alleviate symptoms. Common indications include:

  • Severe Thumb Base Arthritis (CMC Joint Arthritis): This is the most frequent reason, especially when cartilage loss is extensive, causing chronic pain and weakness.
  • Chronic Joint Instability: If the thumb joint is persistently unstable due to ligament damage or other issues, fusion can provide lasting stability.
  • Deformity: To correct significant deformities of the thumb that impair function.
  • Failed Joint Replacement: In cases where a previous joint replacement in the thumb has failed.
  • Severe Trauma: Following severe injuries that have damaged the joint beyond repair.

Benefits and Considerations

Aspect Benefits of Thumb Arthrodesis Considerations/Drawbacks
Pain Relief Highly effective in eliminating severe, chronic joint pain. Permanent loss of motion at the fused joint.
Stability Provides a strong, stable, and durable thumb platform. May alter grip mechanics and precision pinch.
Function Improves overall hand strength and stability for pinch and grasp. Recovery period involves significant immobilization.
Longevity A permanent solution, avoiding future joint problems. Potential for non-union (bones don't fuse properly).

Who Is a Candidate for Thumb Fusion?

Candidates are typically individuals experiencing persistent, severe pain and functional limitations due to thumb joint damage, where conservative treatments (like anti-inflammatory medications, splinting, or injections) have not provided relief. A thorough evaluation by a hand surgeon is essential to determine if thumb fusion is the most appropriate treatment option.