Design Strategies of a Personalized Surgical Instrument to Adjust the Distraction Angle and Posterior Slope for Open Wedge High Tibia Osteotomy Surgery

Abstract

Abstract The precise creation and control of osteotomy and distraction have been a problem in opening wedge high tibial osteotomy (OWHTO). This study aimed to investigate the impact of the cutting edge of a personalized surgical instrument (PSI) to control the distraction angle, tibial slope, and tibial twist of the distracted tibiae. This study correlated the PSI design with the results of biomechanical tests on wedge inclination (WI), saw progression (SP), and distraction site (DS) of the proximal tibiae, which were systematically varied and three-dimensionally (3D) printed as the specimens. The lateral hinge 3D orientation was determined by the WI and SP. Different DSs deviate from the hinged motion of the distracted tibiae to some extent. The coronal angle, which is the major OWHTO target, is more sensitive to the SP and DS. However, the concurrence of the sagittal and horizontal angles induces undesirable effects on knee biomechanics and potentially risks the lateral hinge. The cutting edge is a key design that serves as the cutting and sawing guide to control the initial cut on the medial tibia (i.e., WI) and the sawing path near the lateral cortex (i.e., SP). Intraoperative planning of manipulating the SP is the most effective method for adjusting the sagittal rotation. A higher WI angle is a determinant factor of the horizontal rotation that must be cautiously mitigated to reduce the risk of lateral hinge cracking and to adjust the patellofemoral contact.