Thumb CMC Joint Surgery: Procedure, Types, and Recovery

How is CMC surgery done?

CMC (carpometacarpal) surgery, most commonly performed for advanced thumb base arthritis, typically involves removing the arthritic trapezium bone and reconstructing the joint with a patient's own tendon to restore stability and function.

Understanding the CMC Joint and Thumb Arthritis

The carpometacarpal (CMC) joint of the thumb, also known as the basal joint, is a critical saddle-shaped joint formed by the trapezium bone in the wrist and the first metacarpal bone of the thumb. Its unique structure allows for a wide range of motion, including opposition (touching the thumb to other fingers), which is essential for gripping, pinching, and fine motor skills. Over time, particularly with repetitive use or injury, the cartilage cushioning this joint can wear down, leading to osteoarthritis. This condition, known as CMC joint arthritis, causes pain, stiffness, weakness, and can severely impair hand function.

When is CMC Surgery Recommended?

Surgery for CMC joint arthritis is generally considered when conservative treatments have failed to provide adequate relief. Non-surgical options typically include:

• Rest and activity modification
• Splinting or bracing
• Anti-inflammatory medications (NSAIDs)
• Corticosteroid injections
• Occupational or physical therapy

If pain persists, daily activities remain significantly limited, and imaging (X-rays) confirms advanced cartilage degeneration, surgical intervention may be the most effective long-term solution.

Types of CMC Surgery

Several surgical techniques exist for treating CMC joint arthritis, each with specific indications:

• Trapeziectomy: This is the most common procedure, involving the complete removal of the trapezium bone. Removing the arthritic bone eliminates the bone-on-bone friction that causes pain.
• Ligament Reconstruction Tendon Interposition (LRTI) Arthroplasty: Often performed in conjunction with a trapeziectomy, this procedure involves removing the trapezium and then using a portion of a local tendon (commonly the flexor carpi radialis or FCR tendon) to create a "spacer" in the void left by the removed bone. This tendon is often woven to reconstruct the joint's ligaments, providing stability and preventing the metacarpal from collapsing into the wrist.
• Joint Fusion (Arthrodesis): This involves permanently fusing the first metacarpal to the trapezium bone, eliminating movement at the joint but also pain. It's typically reserved for younger, highly active individuals who require strong pinch and grip strength and are willing to sacrifice some range of motion.
• Joint Replacement (Arthroplasty): Similar to hip or knee replacement, this involves replacing the damaged joint surfaces with artificial implants. While offering good pain relief and motion, these implants may have a shorter lifespan than other options and are less commonly performed for the CMC joint compared to LRTI.

For the purpose of this article, we will focus on the Ligament Reconstruction Tendon Interposition (LRTI) Arthroplasty with Trapeziectomy, as it is the most frequently performed and well-established procedure for advanced CMC arthritis.

Preparing for CMC Surgery

Before surgery, patients undergo a thorough medical evaluation, including a physical examination, review of medical history, and imaging studies. The surgeon will discuss the procedure, potential risks, and expected outcomes. Patients may be advised to:

• Stop certain medications (e.g., blood thinners)
• Avoid food and drink for a specified period before surgery
• Arrange for transportation home and assistance during the initial recovery phase

The Surgical Procedure (LRTI with Trapeziectomy)

CMC surgery is typically performed on an outpatient basis, meaning the patient can go home the same day. The procedure generally takes 1-2 hours.

• Anesthesia: The surgery is usually performed under regional anesthesia (e.g., an arm block), which numbs the arm and hand, often combined with sedation to keep the patient comfortable. General anesthesia may also be an option.
• Incision: The surgeon makes an incision on the back or side of the wrist at the base of the thumb. The exact location and size of the incision depend on the surgeon's preference and the specific technique.
• Trapeziectomy: The first crucial step is to carefully remove the entire trapezium bone. This eliminates the source of the arthritic pain and creates a space between the first metacarpal and the scaphoid bone.
• Tendon Harvest and Preparation: A small portion of a healthy, expendable tendon, most commonly the flexor carpi radialis (FCR) tendon located on the wrist, is harvested. This tendon is then prepared, often by splitting it lengthwise or shaping it, to create a suitable graft for reconstruction.
• Tendon Interposition and Ligament Reconstruction:
  • One end of the harvested tendon is anchored to the base of the first metacarpal.
  • The tendon is then passed through a drill hole in the metacarpal, creating a loop that helps stabilize the joint.
  • The remaining portion of the tendon is then either coiled or folded into the space where the trapezium once was. This acts as a soft tissue "spacer" or cushion, preventing the metacarpal from rubbing directly against the scaphoid.
  • The tendon may also be used to reconstruct the weakened or torn ligaments around the CMC joint, further enhancing stability.
• Closure: Once the reconstruction is complete, the surgical site is irrigated, and the incision is closed with sutures.
• Dressing and Splinting: A sterile dressing is applied, and the hand and wrist are immobilized in a bulky soft dressing or a cast/splint. This protects the healing tissues and maintains the thumb in an abducted (away from the palm) position to prevent the metacarpal from collapsing into the trapeziectomy space.

Post-Operative Care and Rehabilitation

Recovery is a crucial phase following CMC surgery.

• Initial Immobilization: The hand will remain in a cast or splint for approximately 4-6 weeks to allow the tendon graft and surrounding tissues to heal.
• Pain Management: Pain medication will be prescribed to manage post-operative discomfort.
• Hand Therapy: After the initial immobilization period, physical or occupational therapy is vital. A hand therapist will guide the patient through a progressive exercise program to:
  • Restore range of motion
  • Improve strength
  • Reduce swelling
  • Regain functional use of the hand and thumb
• Activity Restrictions: Patients will need to avoid heavy lifting, gripping, and pinching for several months to protect the healing joint.

Potential Risks and Complications

While CMC surgery is generally safe, as with any surgical procedure, there are potential risks, including:

• Infection
• Bleeding
• Nerve damage (leading to numbness or weakness)
• Stiffness or persistent pain
• Failure of the tendon graft
• Complex regional pain syndrome (CRPS)
• Scarring

The surgeon will discuss these risks in detail during the pre-operative consultation.

Recovery Timeline and Outcomes

Full recovery from CMC surgery can take several months, often 3-6 months, with continued improvement possible for up to a year. Most patients experience significant pain relief and improved hand function, allowing them to return to daily activities and hobbies. The primary goal of the surgery is to alleviate pain and restore functional use of the thumb, and for the vast majority of patients, these goals are successfully met.

Conclusion

CMC surgery, particularly the LRTI with trapeziectomy, is a well-established and effective treatment for advanced thumb base arthritis. By understanding the intricate anatomy of the CMC joint and the meticulous steps involved in the surgical procedure, patients can approach their treatment plan with greater confidence and engage proactively in their rehabilitation journey for optimal outcomes.