The adductor tubercle: an important landmark to determine the joint line level in revision total knee arthroplasty

Purpose The restoration of the physiological femoro-tibial joint line (JL) is important to obtain a good outcome in revision total knee arthroplasty (RTKA). However, its assessment is challenging. The ratio of the distance between the adductor tubercle (AT) JL (ATJL) and the trans-epicondylar femoral width (FW) was proposed as a reliable method. The purpose of this study was to check whether this ratio is a reliable tool to restore the prosthetic JL height in challenging prosthetic revision cases. Methods Twenty-one patients (mean age 65.8 years) were recruited. During surgery, FW was measured and ATJL distance was calculated using 0.53 (SD 0.03) as the ratio. After implant positioning, the obtained ATJL line was measured to verify the accuracy of the surgical procedure. Thirteen patients presented a healthy contralateral knee: a comparative radiograph examination was performed to verify the appropriateness of the restored JL height. Results The intra-operatively calculated ATJL was not significantly different with respect to the measured ATJL obtained after prosthetic component implantation. The comparative analysis between the restored JL and the JL of the contralateral not operated knee was also not statistically significant, thus confirming the appropriateness of the restored JL height. Conclusions This study shows that the method which uses an AT to JL distance/FW ratio to determine the JL level, previously applied in primary TKA, is valid when using intra-operatively acquired measurements in RTKA. This is clinically relevant since it represents a reliable tool which helps surgeons to restore the JL level in challenging prosthetic revision cases.