Consistency Test Of Two Coronal Tibiofemoral Subluxation Measurement Methods

Objective:To compare the agreement of two methods for measuring coronal tibiofemoral subluxation(CTFS).To investigate the effect of valgus stress position and unicondylar replacement(UKA)on CTFS value.Methods:First,18 patients(30 knees: 8 women,10 men)who were hospitalized for knee osteoarthritis(KOA)and underwent UKA treatment from June 2018 to June 2020 were randomly selected.An orthopedic physician measured the CTFS value of the knee joint in the anterior and lateral position(weight-bearing position)using method a(the distal femur and the lateral border of the proximal tibia as reference markers)and method b(First,make the mechanical axis of the tibia,and make its parallel line through the vertex of the femoral intercondylar fossa.The distance between the two lines is the CTFS value)respectively,and repeated the measurement one week later.Another physician measured the CTFS value of the same sample.The intraclass correlation coefficient(ICC)of the two methods was compared.Continue to expand the sample size(100 knees)with the method with better consistency,measure CTFS values on valgus stress radiographs and UKA postoperative radiographs,and then analyze the effects of valgus stress and UKA surgery on CTFS.All patients were operated by the same surgeon and surgical team.Results:Method a had a higher ICC value,showing good test-retest and interobserver agreement(ICC=0.859,0.779).Comparing the CTFS values measured on imaging before and after UKA surgery,it was found that there was a significant difference(p<0.05).There was no significant difference between the CTFS values measured in the weight-bearing position and the valgus stress position(p>0.05).Conclusion:Using method a(ie,the distal femur and the lateral border of the proximal tibia as reference markers)is more reliable and reproducible,and is recommended for clinical assessment of coronal tibiofemoral subluxation.UKA surgery can significantly correct CTFS,but the effect of valgus stress position on CTFS is unclear and needs further study.