Finger pulp-inspired flexible pressure sensor array for gap balance monitoring during total knee arthroplasty

Total knee arthroplasty (TKA) is one of the most effective treatments for end-stage knee osteoarthritis (∼1 million annual surgeries globally), where the biomechanical stability of the implanted prosthesis is crucial for lower limb mechanical axis alignment and postoperative normal gait. Most surgical failures and revisions are caused by intraoperative soft tissue imbalance. It heavily relies on surgeons' experience. Here, we present a wireless digital system featuring an ultrathin finger pulp-inspired flexible pressure sensor array, enabling balance monitoring in the clearance between the tibial component and polyethylene spacer, providing a specification-independent option. It addresses the inherent trade-off between body mass-level measurement range and minute force change detection during balancing. The bio-inspired sensor features fingerprint/mechanoreceptor-shaped trans-scale microstructures, achieving high linear sensitivity (0.016 N^-1/0.002 N^-1), wide range (0-150 N per sensor and >440 N total), and fast response/recovery time (50/75 ms), with stability (>1000 cycles). Prosthetic bone validation demonstrates bilateral real-time quantitative force visualization across flexion angles (0°, 45°, 90°). Cadaveric validation with authentic bone mass and intraoperative force variations confirms clinical effectiveness and compatibility.