Smart Implants for Orthopedic Applications

Abstract

Smart orthopaedic implants integrating embedded sensors, wireless telemetry, and bioresponsive surface coatings represent the next generation of musculoskeletal devices, enabling real-time monitoring of implant loading, osseointegration, and infection status. This study developed and evaluated three smart implant prototypes for total knee arthroplasty (TKA): (i) a strain gauge-instrumented tibial tray with Bluetooth Low Energy (BLE) telemetry for continuous load monitoring; (ii) an impedance-sensing implant surface for real-time osseointegration tracking; and (iii) a pH/temperature-responsive antimicrobial coating (gentamicin-loaded mesoporous silica nanoparticles, MSN-Gent) releasing antibiotic in response to infection-associated microenvironmental changes. In vitro biomechanical testing demonstrated strain gauge accuracy within 2.4% of reference load cell measurements across 0-3,000 N physiological loading range. The impedance sensor detected simulated osseointegration (hydroxyapatite mineral deposition) with sensitivity of 4.8 Ohm/µm coating thickness. MSN-Gent coating achieved 14-day sustained gentamicin release (cumulative 84.2 +- 6.4 µg/cm2) with pH-triggered burst release (4.2-fold at pH 5.0 vs pH 7.4) and 99.8% S. aureus biofilm inhibition. In a 12-week ovine TKA model (n = 8/group), instrumented implants transmitted continuous load data wirelessly with 98.4% data integrity, and MSN-Gent-coated implants showed zero infection versus 25% infection rate in uncoated controls. These results establish the feasibility of multi-functional smart orthopaedic implants combining sensing, telemetry, and bioresponsive drug delivery for personalised post-operative monitoring.