What is rhizarthrosis, or osteoarthritis of the base of the thumb?

It is osteoarthritic damage between the trapezium bone and the first metacarpal. It presents as a painful thumb, disabling and deformed.

Rhizarthrosis is often due to late, poorly managed treatment of injuries to the trapeziometacarpal joint or to repeated trauma to the base of the thumb.

It can be triggered by the late after-effects of a violent injury from sport or from an everyday accident.

These include fractures of the base of the first metacarpal (extra-articular fracture, Rolando fracture, Bennett fracture-dislocation), sometimes with dislocations and ligament injuries, or thumb sprains.

Treatment is either:

• medical, with anti-inflammatory drugs and night-time wear of a thumb brace — a resting splint in abduction — immobilising the thumb in the less advanced forms of rhizarthrosis (the brace is recommended at night, and during the day in case of acute pain).
• surgical, mostly for advanced forms of the osteoarthritis; the method used is trapeziectomy (the trapezium bone is removed to deal with the arthritic area between it and the first metacarpal).

Trapeziectomy requires the thumb to be immobilised for about a month, followed by rehabilitation lasting up to 5 or 6 months, with good functional results.
A prosthesis has a faster recovery. Rehabilitation starts at about one week and lasts around two months. However, like any prosthesis, it must be treated with care so that it does not wear out too quickly.