Background: Proximal interphalangeal joint (PIPJ) arthroplasty in border digits is controversial because of unprotected external loading forces and limited canal sizes in the small finger. The use of neither a semiconstrained, surface replacement proximal arthroplasty (SRA) nor a lateral approach that preserves the external collateral ligament has been well described. Methods: Eight women (mean age, 66 years) underwent SRA of 5 index and 4 small digits for osteoarthritis. Active range of motion, deformity, and grip and pinch strengths were measured, and patients completed a visual analog pain scale, QuickDASH, and satisfaction survey. Radiographs were assessed for implant loosening or subsidence. Results: Mean follow-up was 29 months. Mean pain score decreased from 8.0 to 0.8. Mean coronal deformity decreased from 22° ulnar deviation to 6°. Average PIPJ arc of motion improved from 51° to 56°. No lateral instability was observed. Final lateral pinch averaged 4.4 kg in affected vs 4.0 kg in opposite hand. Average final grip strength was 19 kg in affected vs 16 kg in opposite hand. Postoperative QuickDASH averaged 24; postoperative satisfaction score averaged 3.7 (5-point Likert scale). Radiographic analysis showed no implant subsidence or radiolucent lines. Conclusions: PIPJ SRA appears to be a reasonable option in border digits, as is a lateral approach on the inside border of the affected digit. Pain relief and lateral stability are predictable, and motion improves slightly. If a longitudinal incision is made, placement slightly dorsal to the midaxial line away from the digital nerve may help to avoid a tender scar.
