The Linear Coronal Knee Offset (LCKO)-Preliminary Study of New Method of Measuring Knee Varus/Valgus Malalignment

Introduction  Considerable attention is focused on preoperative templating of radiological images in patients undergoing total knee arthroplasty to obtain optimal alignment and outcome. Several radiological measurements have been described. Purpose  In this study, we illustrate a new linear measurement: The linear coronal knee offset (LCKO) that can be used to analyze the coronal configuration on long leg alignment radiographs commonly undertaken during preoperative templating. Methods  A retrospective search was performed of our Picture Archiving and Communication System and Radiology Information System to identify 100 lower limbs anteroposterior, weight bearing, long leg alignment view radiographs of patients referred to knee clinics over 1 year with knee pain. Demographic details, clinical indication, standard radiological measurement of the anatomical tibiofemoral angle, and the LCKO were measured and data were analyzed using Student's t -test. In addition, intraclass correlation coefficient was used to analyze for intraclass reliability. Results  The average age of patients was 36.3 years (range: 12-80 years) with a male predominance. The LCKO was statistically significant between the three cohorts of patients. The mean LCKO in normal cohorts was 0.24 cm, varus was -0.6 cm, and valgus was 1.72cm. There was good inter and interobserver reliability (Kappa of 0.8 and 0.8, respectively). Conclusion  The novel LCKO measurement provides a simpler method in assessing coronal lower limb malalignment and can easily identify a normal, varus, or valgus knee deformity.