Malpositioning of patient-specific instruments within the possible degrees of freedom in high-tibial osteotomy has no considerable influence on mechanical leg axis correction.

Purpose: Patient-specific instruments (PSIs) are helpful tools in high tibial osteotomy (HTO) in patients with symptomatic varus malalignment of the mechanical leg axis. However, the precision of HTO can decrease with malpositioned PSI. This study investigates the influence of malpositioned PSI on axis correction, osteotomy, and implant placement.