Pinless-Navigated Versus Conventional Total Knee Arthroplasty

Overview

The success of total knee arthroplasty depends on a number of factors including pre-operative range of movement, obesity, medical comorbidities, prosthesis design, preparation and implantation of the prosthesis, soft tissue balancing, as well as implants alignment. Optimal placement of the implants within 3° of the mechanical axis of the lower limb has been proven to reduce wear and early implant failure. Compared to conventional techniques, computer-Aided Navigation total knee arthroplasty has been widely used in the last decade and have been proven to improve the accuracy of prosthesis placement and lower limb alignment by reducing the number of outliers with more than 3° deviation from the mechanical axis. However, its use also involves a steep learning curve, high initial capital cost and longer duration of surgery. Traditional computer-navigated TKA using optical tracking systems also requires fixation of the femoral and tibial reference arrays to bone using anchoring pins. Complications reported with the use of these pins include either femoral or tibial fracture, pin site pain, pin site infection and osteomyelitis. The investigators study aims to investigate the accuracy of a new pinless navigation system for TKA that will avoid these complications.

The duration of surgery and length of hospital stay were recorded for all patients. Three radiographic measurements were recorded on the coronal films: 1) Hip-Knee-Ankle Angle (HKA), the angle formed by the mechanical axis of the femur (line between the centre of the femoral head and the centre of the knee) and the mechanical axis of the tibia (line between the centre of the talus and the centre of the knee); 2) Coronal Femoral-Component Angle (CFA), the angle formed by the femoral component and the mechanical axis of the femur; 3) Coronal Tibia-Component Angle (CTA), the angle formed by the tibia base plate and the mechanical axis of the tibia. The post-operative radiographic measurements were compared with the intra-operative readings from the pinless navigation system. The accepted values used in our study for normal alignment were: 1) 0° ± 3° varus/valgus for HKA; 2) perpendicular (± 3°) to the mechanical axis of the femur; 3) perpendicular (± 3°) to the mechanical axis of the tibia.