Comparative study between the pinless navigation and the articular surface mounted (ASM) navigation in total knee arthroplasty: Radiographic results and early clinical outcomes

Abstract

Introduction: There were reports showed pinless navigation and articular surface mounted navigation in total knee arthroplasty (TKA) produces better results in term of radiographic outcomes when compared to conventional techniques. However, there was no comparative study between these two systems. Objective: To compare the radiographic results and early clinical outcomes between two systems. Methods: We collect data from all patients underwent TKA using either system from 1 January 2014 to 30 September 2014. We excluded the patient whom underwent navigation on tibia or femur only; the patients with pre-op deviation of mechanical axis more than 15 degrees, and the patients with extra-articular deformity. Radiographic outcomes included pre and post-operative alignment, and post-operative prosthesis alignment in coronal and sagittal plane. Clinical outcomes included demographic data, knee score and functional score, tourniquet time, blood loss, and complications. Results: 83 patients were included (43 pinless group, 40 ASM group). There was no statistical significant difference in the mean of age, BMI, pre-operative deformity, and pre-operative knee score, functional score, blood loss, and post-operative knee score and functional score. However in term of radiographic results, the mean post-operative correction of mechanical axis of pinless navigation was varus 1.1+/-2.16 degree while mean of ASM navigation was varus 0.01+/-1.88 degree. The difference was statistically significant with p-value less than 0.05. Percentage of radiographic outlier of pinless group was 13.95% while ASM group was 2.5%. Conclusion: The ASM navigation showed better result in term of post-operative correction of mechanical axis, which due to the ability to verify bone resection after the bone was resected. This feature could be beneficial in future development of this simple CAS system.