Standard image-free navigation systems have proven to improve the accuracy of components placement and reduce the proportion of outliers for lower limb mechanical axis in total knee arthroplasty (TKA). However, their disadvantages include a longer duration of surgery and pin-tract related complications. More recently, pinless navigation has been developed to address these shortcomings. This study aims to investigate the effectiveness of a new pinless navigation system (Zimmer® iAssist™ Knee) in TKA. Power analysis was performed. To detect a significant difference in the proportion of outliers for lower limb mechanical axis at a power of 0.80, a sample size of 50 patients would be required. Between May 2013 and April 2014, 50 patients diagnosed with osteoarthritis of the knee were divided into two surgical technique arms: 1) iAssist™; 2) conventional TKA. One Adult Reconstruction surgeon performed all the surgeries. The patients were prospectively followed up and postoperative long leg radiographs were taken at one month post-surgery. Two reviewers blinded to the surgical method performed the measurements on radiographic films. Five radiographic measurements were measured: 1) Hip-Knee-Ankle Angle (HKA); 2) Coronal Femoral-Component Angle (CFA); 3) Coronal Tibia-Component Angle (CTA); 4) Sagittal Femoral-Component Angle (SFA); and 5) Sagittal Tibia-Component Angle (STA), The Mann-Whitney U test was used to compare the two groups for quantitative variables while the Fisher's exact test was used for categorical variables.Introduction
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