Patient-specific Instruments in Total Knee Arthroplasty

Abstract

Most orthopedic surgeons use conventional instruments to achieve accurate bone cuts in total knee arthroplasty. An intramedullary alignment rod is usually used to place the cutting jig at a valgus correction angle so that the distal femoral cut is made perpendicular to the mechanical axis of the femur. Over the tibial side, many surgeons use an extramedullary alignment guide to place the cutting jig perpendicular to the tibial mechanical axis; some surgeons prefer to use an intramedullary guide. The criticism is that outliers are not uncommon with conventional instruments, even in experienced hands. If the mechanical lower limb alignment within 3° valgus and 3° varus from neutral was considered as normal, 20–33% of total knee arthroplasty would be outside of this range with conventional instruments [1–4]. Factors such as the bowing of the femur and tibia could affect the accuracy of the bone cuts in both the coronal and sagittal planes [5,6].