In vitro kinematic analysis of a new patient-matched polycarbonate urethane radiocarpal interposition arthroplasty

Current salvage procedures for patients with post-traumatic wrist osteoarthritis include excision of bone or tissue and/or fusion of wrist bones, making all surgical salvage procedures irreversible. Some of these salvage procedures decrease wrist mobility. A novel patient-matched polyurethane carbonate (PCU) radiocarpal interposition arthroplasty has recently been proposed as a reversible, motion-preserving solution. This experimental study evaluates the effect of the PCU radiocarpal implant on wrist range of motion (ROM) and carpal kinematics. Additionally, implant displacement is assessed during functional ROM. The passive wrist ROM of three cadaveric arms was measured in a wrist motion simulator before and after implantation of the PCU radiocarpal implant by applying a 1 Nm Torque. Three-dimensional fluoroscopy scans of the wrist were acquired in 15° steps during flexion-extension (F/E = 60°/60°) to assess carpal bone and implant kinematics. The mean differences in carpal kinematics between native and implantation conditions were calculated per cadaveric wrist and averaged across all three specimens. The mean wrist ROM did not demonstrate clinically relevant differences between the native and implantation conditions, except for a reduction of 10.3° in extension. Variations in carpal rotations and translations over the F/E curve were smaller than 2.5° and 2.2 mm and were therefore considered negligible. The PCU radiocarpal implants' rotations and translations were maximally 6.3° and 1.1 mm during F/E. Given these results, the PCU radiocarpal interposition arthroplasty may be a promising option for patients with post-traumatic radiocarpal arthritis, offering a balance between maintaining mobility and providing pain relief through a minimally invasive and reversible procedure.