Restoring the joint line (JL) is a key element of performing joint arthroplasty, which is a challenging proposition during revision surgeries. We investigated the accuracy of 2 different methods of identifying the JL using the adductor tubercle (AT) as the reference landmark.
Standardized protocols for measurements from 50 knee radiographs were established. Femoral width (FW) and the distance from the AT to the JL (ATJL) were measured on anteroposterior radiographs, and the femoral diameter (FD) was measured on true lateral views. The individual ratio of FW and FD to ATJL was calculated using linear regression analysis. Intraobserver and interobserver reliability was assessed. In order to test the accuracy of the ratio calculated, we also recorded the FW and ATJL of 20 additional knees by magnetic resonance images.
There are significant differences between genders with these parameters. A linear correlation was found between FW and ATJL (r2 = 0.7201), which was more reliable than the correlation between FD and ATJL (r2 = 0.3918). Interobserver repeatability was better for ATJL and FW than for FD. The mean ratio of ATJL/FW was 0.560 ± 0.03, and there was no statistical difference between men and women. After using this ratio formulas in those data measured from knee magnetic resonance imaging, all cases revealed reliability with 100% cases lying in a 4-mm error margin.
The AT can be used as a reliable landmark to determine the knee JL position, and the formulas for calculating the ATJL with FW can be applied, making intraoperative identification and judgment easier.