Interpositional arthroplasty is by many considered to be the current gold standard for the treatment of thumb carpometacarpal arthritis. The results are generally good, but the rehabilitation time can be long and failures are difficult to treat. Total joint replacements now exist with modern uncemented designs that can be an alternative treatment. Short term studies show that thumb function often is better and rehabilitation time shorter, however there is uncertainty with regards to the longevity of the implants. Currently no prospective randomized trials have compared these two treatment options. Our hypothesis is that the total joint replacement will give the same results or better when compared to the interpositional arthroplasty.

Eligible: patients >18 years with pain and dysfunction from the first cmc joint. Clinical and radiological arthritis.

Exclusion: degenerative changes in the STT joint (all patients are assessed by CT), other injuries in the hand/thumb, pregnancy

Outcome measures: quick-Dash, Nelson hospital score, range of motion, grip strength

Complications are registered.

The patients are observed for two years and the investigators aim to include a total of 40 patients.

Inclusion Criteria:

• CMC 1 arthritis
• Pain and dysfunction
• Adult patients
• General good health

Exclusion Criteria:

• Pregnancy
• STT arthritis (CT scan preoperatively for all patients)
• Other injuries in thumb/hand