Courtesy: Mahdi Siala MD, Nice, France

Trapeziometacarpal (TMC) Dual Mobility Arthroplasty

Introduction

Trapeziometacarpal (TMC) arthroplasty has evolved significantly with the development of dual mobility prosthetic systems for thumb carpometacarpal (CMC) arthritis.

This approach aims to improve:

Stability
Range of motion
Recovery time
Functional outcomes

Modern dual mobility implants are inspired by hip arthroplasty concepts and are increasingly used in the treatment of thumb CMC osteoarthritis.

Functional Importance of the Thumb

The thumb is essential for:

Fine pinch
Precision grip
Power grip

The thumb CMC joint must provide both:

High mobility
High stability

This creates a unique biomechanical challenge.

Biomechanics of the First CMC Joint

Joint Characteristics

Although traditionally described as a saddle joint, the first CMC joint behaves functionally like a complex ball-and-socket articulation.

Movements

The joint allows:

Flexion and extension
Abduction and adduction
Axial rotation
Pronation and supination

Joint Forces

The TMC joint experiences very high loads during pinch activities.

Joint load may reach approximately 12 times the tip pinch force
Forces may approach 1200 N during strong pinch

Stability of the TMC Joint

Because bony congruence is limited, stability depends mainly on:

Ligaments
Joint capsule
Muscles

Important stabilizers include:

Anterior oblique ligament (AOL)
Dorsoradial ligament (DRL)

Ligament laxity is associated with development of CMC osteoarthritis.

CMC Osteoarthritis

Common Classification Systems

Eaton-Littler classification
Dell classification

Clinical Features

Patients commonly present with:

Thumb base pain
Reduced grip strength
Weak pinch
Loss of opposition
Reduced abduction
Loss of rotational movement

Goals of Surgical Treatment

An ideal procedure should:

Preserve thumb length
Maintain strength
Preserve mobility
Maintain fine motor and gross motor function
Provide stability without stiffness

No single surgical procedure perfectly fulfills all these goals.

Historical Evolution of Surgical Treatment

Traditional Procedures

Historically used procedures include:

Trapeziectomy
Ligament reconstruction and tendon interposition (LRTI)
Arthrodesis

Early Implant Arthroplasty

Early prosthetic designs introduced in the 1970s had high complication rates, including:

Dislocation
Implant loosening
Mechanical failure

Modern Developments

Advances include:

Modular implants
Improved biomaterials
Metal-polyethylene articulation
Dual mobility systems

Dual Mobility Concept

The dual mobility concept originated from hip arthroplasty.

It was adapted for thumb CMC arthroplasty around 2010.

Advantages of Dual Mobility

Potential benefits include:

Reduced dislocation risk
Improved stability
Better range of motion
Improved function

Advantages of TMC Dual Mobility Arthroplasty

Reported benefits include:

Restoration of thumb length
Correction of Z-deformity
Faster recovery compared with trapeziectomy
Improved key pinch strength
Low early revision rates
Multiple revision options if failure occurs

Some studies report key pinch strength exceeding the opposite side after recovery.

Disadvantages

Limitations include:

Technically demanding procedure
Steep learning curve
Higher implant cost
Limited long-term outcome data

Surgical Principles

Surgical Approach

The dorsal approach is most commonly used.

Important structure to protect:

Superficial radial nerve

Metacarpal Preparation

Proper exposure is essential.

Oversizing should be avoided because it may cause:

Stress shielding
Fracture risk
Poor implant seating

Trapezium Preparation

This is considered the most critical step.

Important goals include:

Preserving at least 6–8 mm of bone stock
Proper cup positioning
Stable fixation

Implant Positioning

The prosthetic cup should be:

Centered
Parallel to the articular surface

Fluoroscopy and trial reduction are recommended intraoperatively.

WALANT Technique

WALANT

Wide Awake Local Anesthesia No Tourniquet (WALANT) is increasingly used in hand surgery.

Advantages

Benefits include:

No tourniquet discomfort
Active intraoperative movement testing
Immediate assessment of function
Reduced cost

Clinical Outcomes

Reported short-term results include:

Approximately 94% return to work within 6 weeks
Implant survival rates around 96–97%
Patient satisfaction rates of approximately 90–95%

Complications

Common Complications

De Quervain’s tenosynovitis
Superficial radial nerve irritation
Trigger thumb

Less Common Complications

Cup loosening
Trapezium fracture
Infection

Revision Surgery Options

Revision options include:

Larger revision implant
Alternative implant system
Conversion to trapeziectomy
Suspension arthroplasty
Scaphometacarpal salvage procedures

Scaphotrapeziotrapezoid (STT) Arthritis

STT arthritis commonly coexists with thumb CMC arthritis.

In many patients:

Treating the CMC joint alone adequately relieves symptoms

Separate treatment for STT arthritis is often unnecessary.

Patient Selection

Indications

Symptomatic Stage II–IV CMC osteoarthritis
Failure of conservative treatment

Contraindications

Severe trapezium bone loss
Poor bone quality

Special Situations

Heavy Manual Workers

Traditionally treated with arthrodesis, but arthroplasty is increasingly considered.

Inflammatory Arthritis

Can be treated successfully if deformity is manageable.

Implant Trends

Common dual mobility systems include:

Touch
Maya
Moovis

There is an increasing trend toward dual mobility implants in thumb arthroplasty.

Material Considerations

Metal allergy, particularly nickel sensitivity, is uncommon but clinically relevant.

Some modern implants are now nickel-free.

Current Limitations and Evidence Gaps

Important limitations include:

Lack of long-term follow-up data
Variability in surgical technique
Differences in implant systems
Limited comparative trials

More standardized long-term studies are needed.

Conclusion

Dual mobility TMC arthroplasty represents a major advancement in the treatment of thumb CMC arthritis.

Potential advantages include:

Better function
Improved stability
Faster recovery
Lower early complication rates

However, limitations remain, including:

Technical difficulty
Learning curve
Need for long-term evidence

Dual mobility arthroplasty may increasingly become a first-line surgical option for selected patients with thumb CMC osteoarthritis

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