Validation of an Imageless Optical Computer-assisted Navigation System for Total Knee Arthroplasty

Background: Restoration of the hip-knee-ankle (HKA) angle to within 3 of the neutral mechanical axis is considered a well-aligned total knee arthroplasty (TKA), with outliers associated with higher failure rates. Thus, efforts to improve intraoperative surgical accuracy are of strong clinical interest. This study evaluated the accuracy and safety of a novel, imageless, computer-assisted navigation system (CAS) for TKA.Methods: 112 consecutive patients who underwent primary TKA between January-December 2020 with 2 board-certified, high-volume orthopedic surgeons using the same imageless CAS were retrospectively reviewed. Patient age, BMI, sex, postoperative complications, and reoperations were collected. Two trained reviewers independently assessed tibial and femoral component mechanical alignment measurements in a standardized manner on postoperative full-leg AP and lateral radiographs. The primary outcome was mean absolute degrees of difference for each measurement compared to intraoperative CAS measurements. Outcomes were reported as means  standard deviation.Results: 38%(N=43/112) of patients were male. Mean age was 698 years and mean BMI was 31.15.9. 71%(N=79/112) of patients had a well-aligned TKA (HKA within 3).The mean absolute difference was 1.51.2 for femoral coronal alignment, 1.00.8 for tibial coronal alignment, 2.21.5 for femoral flexion, and 1.81.6 for tibial slope.Two patients(1.8%) underwent reoperation; specifically, 1 patient received a 1-stage revision for periprosthetic joint infection 5 months postoperatively and the other underwent lysis of adhesions 9 months postoperatively for arthrofibrosis.Conclusions: This novel imageless CAS provides accurate readings within 2 for tibial and femoral coronal and sagittal alignment, and patients have low complication rates at early follow-up.