Rhizarthrosis (thumb base arthritis)
What is rhizarthrosis ?
Rhizarthrosis is osteoarthritis of the trapeziometacarpal joint, the joint at the base of the thumb, between the trapezium bone of the wrist and the first metacarpal. It is the most common arthritic condition of the hand.
It causes pain with pinching and gripping, progressive weakness and, in advanced cases, a characteristic Z-shaped deformity of the thumb. It predominantly affects women over the age of 50 but can occur earlier, particularly following a previous thumb injury.
When is surgery needed ?
Conservative treatment is always offered first:
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a rest splint worn at night or during painful episodes
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analgesics and anti-inflammatory medication
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corticosteroid injections, which can provide lasting relief
Surgery is considered when these measures no longer provide adequate pain relief, or when functional impairment, difficulty opening jars, holding a pen, pinching, significantly affects daily life.
How is the procedure performed ?
The procedure is performed under regional anaesthesia on a day-case basis.
The surgical technique depends on the radiological findings and the condition of the trapezium:
Trapeziometacarpal joint replacement is preferred when the trapezium is sufficiently preserved and the scaphotrapezial joint is not affected. The worn joint surface is replaced with a prosthesis while the trapezium is kept in place, allowing faster recovery.
Trapeziectomy with ligament reconstruction is preferred when the trapezium is significantly worn or the scaphotrapezial joint is also arthritic. The trapezium is removed and thumb stability is reconstructed using the abductor pollicis longus tendon, which fills the space left by the removed bone.
What is the recovery ?
A resin splint immobilising the thumb is worn for three weeks after surgery.
Wound care is carried out during this period.
Physiotherapy is then prescribed to progressively restore thumb mobility and strength. Full recovery takes three to six months depending on the technique used. Pain related to arthritis resolves in the vast majority of cases.
What are the risks ?
Risks of rhizarthrosis surgery include:
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injury to the superficial branch of the radial nerve, potentially causing pain or numbness over the back of the thumb
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wound infection
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residual thumb stiffness, improved with physiotherapy
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for joint replacement: loosening or dislocation of the implant requiring revision surgery
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for trapeziectomy: progressive thumb subsidence, usually without significant functional consequence