An Accurate Method For Locating The Joint Line During Revision Total Knee Arthroplasty

Background:The systems for precisely locating the joint line during revision total knee arthroplasty are still controversial and they should be better evaluated in the Chinese population.Methods:451 standard anteroposterior knee radiographs from 451(283 males and 168females,the average age of 33.26 years,range 20-50 years)healthy Chinese people were included to measure the femoral width(FW)and the distances from the adductor tubercle(AT),the medial epicondyle(ME),the lateral epicondyle(LE),and the fibular head(FH)to the joint line(JL).Correlation between femoral width and distances from landmarks to the joint line was evaluated using Pearson correlation coefficient.And the ratios of ATJL,MEJL,LEJL,FHJL to FW were calculated.Results:The average FW was89.4±8.8 mm.The average distances from the adductor tubercle(AT),the medial epicondyle(ME),the lateral epicondyle(LE),the fibular head(FH)to the joint line(JL)were 49.4±5.0 mm,28.3±3.1 mm,26.9±2.9 mm,20.0±4.0 mm, respectively.An excellent linear correlation was found between femoral width and the distance from adductor tubercle to the joint line(R=0.836,R~2=0.698),it was more reliable than the lateral epicondyle(R=0.686,R~2=0.471)and the medial epicondyle(R=0.672,R~2=0.452).The average ratios of ATJL/FW,LEJL/FW,MEJL/FW were 0.553,0.302,and 0.317,respectively.Conclusion:The adductor tubercle can be used as a reliable landmark to locate the joint line precisely by the formula(ATJL=0.548×FW in males;ATJL=0.562×FW in females)in the Chinese population.The lateral and medial epicondyle can be the second choices.In this study,X-ray was used for the first time to analyze a large number of data of the Chinese population,and a more accurate ratio was obtained,which can be used to locate the joint line during the operation of the Chinese population.