This is a relatively common form of osteoarthritis (basic joint wear and tear) affecting the joint that joins the thumb to the wrist bones. It is referred to as "first carpometacarpal (CMC) osteoarthritis."
Typically, this is caused by basic wear and tear over many years. In some cases, a previous traumatic event might make one more susceptible to the condition, such as a fracture extending into the joint.
In early stages of the arthritis, the best treatment will be simply modifying your activities or trying different instruments to perform certain tasks, such as using a thicker pen rather than a thin one. Later on, treatment will include splinting to try to help offload the joint. New drugs are being developed which, when injected into the joint, may relieve the associated pain but they are not currently available for this use in Canada.
If this isn't enough, surgery is the next choice.
Surgery for first CMC osteoarthritis involves either fusing the joint or removing one of the bones and recreating a support mechanism for the remaining bones. Fusion is good at removing pain and providing a very stable hand but it significantly reduces thumb mobility; this procedure is usually performed on people who place extremely heavy demands on their hands. The more common procedure is removing one of the small bones (the trapezium) and reconstructing the support for the thumb bone (metacarpal) using tendon from your wrist or local muscle slips from your hand. Your surgeon will discuss which option they think is best for you.
The recovery phase is very long following either surgery, with 3-9 weeks of casting or splinting required. Extensive hand therapy is also needed. Regaining strength and mobility may mean a total of 3-6 months in some cases before the hand is being used completely normally.
As with any surgical procedure, there is a risk of infection. Post-operative numbness can occur but is usually only for a short period of time. The surgery typically requires pins that will be removed later on. Overuse of the hand early on may cause the pins to bend or break, making them much harder to remove. Stiffness and swelling can persist for months in some cases while tenderness at the site of bone resection may take a few months to subside. Your surgeon will discuss other possible complications at the time of your consultation.