First-in-human prospective pilot study of a bipolar dual-center total wrist arthroplasty: early mechanical stability and clinical outcomes.

PURPOSE: Total wrist arthroplasty (TWA) is limited by implant loosening, instability, and non-physiological load transfer, partly because most contemporary implants rely on a single center of rotation and do not preserve native wrist kinematics. This first-in-human pilot study evaluated the feasibility, early mechanical stability, and clinical outcomes of a novel bipolar dual-center TWA system designed to preserve radiocarpal and midcarpal motion.

METHODS

This prospective single-center pilot case series included five consecutive patients with end-stage wrist arthritis treated with a bipolar dual-center TWA implant using cement fixation, as per the device's intended use. The outcome measures included pain assessed using the pain subscale of the Patient-Rated Wrist Evaluation (PRWE) questionnaire (normalized to a 0-10 scale), total PRWE score, DASH score, range of motion, grip strength, radiographic implant stability, complications, and reoperation. Clinical outcomes were assessed at the most recent follow-up visit.

RESULTS

The mean follow-up was 19.2 months (range, 12-24 months), with 24-month data available for three patients. Implant survivorship was 100%, with no loosening, migration, dislocation, or implant revision observed on radiographs. One patient experienced a traumatic postoperative fall without loss of implant fixation. The mean PRWE-derived pain score improved from 9.0 to 3.0, and the mean PRWE total improved from 84.6 to 23.2 at the final follow-up. The mean DASH score improved from 79.0 to 29.5, with substantial inter-patient variability (final range, 0-91.7). All five patients met the predefined responder criterion of ΔPRWE ≥ 20 combined with radiographic stability. Three patients with positive preoperative signs of carpal tunnel syndrome subsequently underwent carpal tunnel release 4-8 months postoperatively, with symptomatic improvement in all patients. One intraoperative carpal fracture was managed without component revision surgery. The mean wrist flexion improved from 13° to 37°, and extension improved from 11° to 32°.

CONCLUSIONS

This first-in-human pilot study demonstrated the technical feasibility and early mechanical stability of the bipolar dual-center TWA concept. All patients met the predefined wrist-specific responder criteria with stable mechanical implant fixation. These findings support further investigation of the dual-center concept in larger studies with longer follow-up periods.