Comparison of three different postoperative treatment options after interposition arthroplasty of the thumb, an observational study.

Background: In rhizarthrosis the saddle joint of the thumb is affected. Occupational therapy after interposition arthroplasty is of particular importance and a key factor for a successful outcome. Orthosis use and/or the timeline of using the orthosis is still under debate.

Research questions: In patients with rhizarthrosis after interposition arthroplasty, what is the effect of an orthotic thumb device compared with no orthotic thumb device during accompanying occupational therapy? In patients with rhizarthrosis after interposition arthroplasty, what is the effect of a long orthotic thumb device compared with a short orthotic thumb device during accompanying occupational therapy?

Methods: Forty-two patients with confirmed symptomatic rhizarthrosis after interposition arthroplasty by Weilby and 2 weeks cast fixation were randomly assigned to one of the following study arms: Group I: long orthotic thumb device, Group II: short orthotic thumb device, Group III without orthotic thumb device for 4 weeks, accompanied by 12 weeks postoperative occupational therapy. After 6 and 12 weeks, VAS-Pain-Score, Quick-DASH, pinch-and grip-strength, and ROM were evaluated.

Results: All groups improved in their hand functions 12 weeks after surgery. The VAS-pain-score improved by 5 points. The Quick-DASH score halved for patients with short or no orthotic thumb device. Patients with the short orthotic thumb device showed the highest rate of improvement (pain, QuickDASH, mobility of the carpometacarpal joint in abduction, interphalangeal joint mobility, and thumb function) 12 weeks after surgery, followed by the non-orthotic thumb device-group. Non-orthotic thumb device patients did not show higher pain levels. Patients of the long orthotic thumb device-group showed more impairment of their function (pain, grip- and pinch strength compared to the other groups, 12 weeks after surgery).

Conclusion: After interposition arthroplasty of the thumb followed by two weeks cast fixation, a thermoplastic short orthotic thumb device should be used. The short orthotic thumb device only restricts motion of the operated first carpometacarpal joint, leaving all other joints of the thumb moveable for 4 weeks. This recommendation is based on the results obtained 12 weeks after surgery.

Trial registration: Not applicable because this is the publication following a thesis in Austria. At the time of the start of the study, there was no need for registration for such studies in Austria.