The footprint of the anterior horn of medial meniscus: A novel and reliable landmark for the tibial vertical cut in Oxford mobile-bearing medial unicompartmental knee arthroplasty

Background: Tibial vertical cut is crucial for rotational position and bony coverage in Oxford mobile-bearing medial unicompartmental knee arthroplasty (UKA). This study aimed to determine whether the footprint of the anterior horn of medial meniscus (FAM) is a reliable landmark for tibial vertical cut.

Methods: The FAM and the line through FAM and the edge of anterior cruciate ligament insertion (FAMA line) were identified by dissection five knee joint specimens. The angle between FAMA line and standard Akagi's line was measured. From 2022 to 2023, 64 patients (74 knees) diagnosed as anteromedial osteoarthritis were included to undergo primary Oxford medial UKA by two surgeons (Group 1 and 2), using FAMA line as a landmark for tibial vertical cut. The anteroposterior (AP) length, mediolateral (ML) length of tibial cut and tibial prothesis were measured by vernier caliper. ML/AP ratio was also calculated, and data were compared intragroup and intergroup. Mediolateral position and external rotation of tibial components were assessed postoperatively.

Results: FAMA line was parallel to standard Akagi's line. No significant differences were found in AP and ML lengths between tibial cut and tibial component (AP different value = 0.007 ± 0.154 cm, P = 0.674, ML different value = 0.020 ± 0.195 cm, P = 0.155). The ML/AP ratio was similar between the two groups (P = 0.141, 0.646, 0.255, 0.607, 0.384, size AA ∼ D). No significant difference was found in mediolateral position (0.87 ± 0.03 vs. 0.86 ± 0.03, P = 0.156) and external rotation (6.88 ± 2.08 vs. 6.68 ± 2.22, P = 0.746) of the tibial component between the two groups.

Conclusion: The FAM is a reliable landmark for tibial vertical cut in Oxford UKA.