A Novel Concept and 3D Coupler for Robotic Correction of Spinal Deformities: In Vitro Experimental Testing

BACKGROUND: Current techniques for surgical correction of spinal deformities impart realigning the deviated vertebrae along a rigid rod. Solid rods are a major restricting factor to vertebral manipulation, leading to incomplete, imprecise, and less predictable 3-dimensional (3D) correction. Additionally, forceful manual nonquantifiable maneuvers may result in potential implant failures and increased incidence of complications. We are introducing a machine-operated device for digitized segmental 6 degrees of freedom (6 DOF) correction of individual vertebral deviations. METHODS: We manufactured a 3D coupler incorporating multiple self-locking uniaxial joints. The device's precision was tested by comparing targeted vs delivered motions. For functionality testing, we used computed tomography-based 3D-printed vertebral models to verify the device's ability to manipulate the vertebra in each direction of motion. RESULTS: In all tested motions, the coupler accurately and repeatedly delivered the predicted targeted motions. The device could mobilize 2 vertebral models relative to each other in 4 out of 6 DOF. CONCLUSIONS: The novel 3D coupler can deliver machine-driven, precise, and predictable multiplanar motion; it could manipulate the vertebral model in rotation and translation. CLINICAL RELEVANCE: The novel device addresses a crucial unmet need in spinal surgery by offering digital precision, true 6 DOF correction, and supporting robotic execution of surgical actions.