An investigation of consistency between posterior condylar axis +3 degree external rotation line and clinical transepicondylar axis line techniques in primary total knee arthroplasty

Objectives: this study aims to investigate discrepancy between posterior condylar axis (pca)+3 degree external rotation (er) line and clinical transepicondylar axis (ctea) line and consistency between the both techniques in primary total knee arthroplasty. patients and methods: thirty-six knees [bilateral knees were operated simultaneously in 12 patients (50%)] in 24 patients [3 men (12.5%),21 women (87.5%); average age 67 (59-80 age)] were included in the study. during surgery,pca+3° er line and ctea line were drawn on the distal femoral cutting surface by electrocautery pencil following distal femoral cut. the both lines on distal femur were recorded by digital camera and relationship between lines was ascertained in reference to pca+3° er line [parallel,internal rotation (ir),er]. statistical analysis was performed by the mcnamara chi square test and kappa (k) value. results: assessment of the images revealed that ctea line in comparison to pca+3° er line was parallel in 22 knees (61.2%),but not parallel in 14 knees (38.8%) [ir in 10 knees (71.5%),er in 4 knees (28.5%)]. there was a significant difference (mcnamara chi square=12.7±1; p<0.001) and poor consistency (k=0.00055) between both lines and techniques,respectively. conclusion: for determination of femoral component rotation in surgery setting,different results between ctea and pca+3° er techniques possibly may due to disadvantages of techniques and anatomic variation of distal femur. thus,using both techniques to check each other's results seems unsafe.