A surgical method for tibia osteotomy includes attaching a patient-specific alignment guide to a corresponding surface of a tibia of a patient for whom the alignment guide is customized during a pre-operative planning stage and making a partial bone cut in the tibia through a planar slot of the alignment guide. The planar slot is oriented at a patient-specific angle relative to an anatomic axis of the patient and the angle is customized during the pre-operative planning stage. The method includes opening the bone cut to form an opening wedge, and inserting a patient-specific implantable wedge into the opening wedge.