Background Osteoarthritis of the thumb carpometacarpal joint (CMC-1 OA) is increasingly common with age. Conservative treatment with anti-inflammatory medication, thumb spica splinting, and steroid injection is recommended for early-stage OA, but some patients will continue to have refractory symptoms and surgery may be considered. We found it interesting to study outcomes of surgical treatment of cases with mild radiographic changes and yet symptoms severe enough to indicate surgery. The specific research question is, if there is a limit of radiographic changes, below which a poor patient-reported outcome (PRO) can be expected.

Purpose In a retrospective cohort of patients with prospectively collected PROs, we intend to study the effect of the radiographic CMC-1 OA severity on the PRO improvement and satisfaction after interposition arthroplasty.

Patients and Methods Radiographs of 347 patients, who had CMC-1 surgery, were retrospectively analyzed. Each rater independently assessed all radiographs classifying each according to the Eaton classification. All patients had surgery with CMC-1 interposition arthroplasty using three well-known techniques that all include a complete trapeziectomy. Comparison between stage 1 and stage 2-4 was done using Chi-square test and t-test.

Results Patients with Eaton stage 1 had a mean improvement in Quick-DASH (QuickDisability of the Arm, Shoulder, and Hand questionnaire) scores of 14.6 points. Patients with Eaton stage 2 to 4 had a mean improvement of 25.3 points. The difference between these two groups was 10.6 points (p = 0 .009) . Only 52% of patients with Eaton stage 1 OA were satisfied. However, 76% of patients with Eaton stage 2 to 4 were satisfied (p = 0.008, chi-square between stage 1 and stage 2-4).

Conclusion Patients with Eaton stage 1 CMC-1 OA had poorer PROs, as compared with more advanced stages of OA, 6 months following surgical treatment with interposition arthroplasty. Based on our results, we advise against surgical treatment with interposition arthroplasty of the very mildest CMC-1 OA, regardless of the preoperative PROs.