Effect of surface replacing arthroplasty of the proximal interphalangeal joint using the CapFlex-PIP implant on distal interphalangeal and metacarpophalangeal joint range of motion — preliminary outcomes

Background The CapFlex-PIP prosthesis (KLS Martin Group, Tuttlingen, Germany) shows favorable results in the medium term for surface-replacing arthroplasty of the proximal interphalangeal joint (PIP). At our department, we have been using this implant since 2019 with a dorsal approach to the PIP joint with a central tendon split. During the regular follow-up visits, we have noticed a reduction in the range of motion at the non-operated distal interphalangeal joints (DIP) during the postoperative course. We therefore wanted to evaluate the results of this group of patients with a focus on postoperative DIP active range of motion and total active motion (TAM). Methods From 2019 to 2020, a total of 29 consecutive CapFlex-PIP prostheses were performed using the mentioned surgical approach. Range of motions and the TAM were registered preoperatively, at 3, and 6 months postoperatively. Results No improvement in PIP range of motion was noted (mean 52.4° vs. 60.9° 6 months postoperatively, p = 0.06). But we noted a reduction in DIP range of motion (mean 39.3° vs. 24.9° 6 months postoperatively, p