Anatomical evaluation of the femoral attachment of the posterior oblique ligament.

INTRODUCTION Tibiofemoral joint instability reduces patient satisfaction after total knee arthroplasty (TKA). However, surgeons sometimes encounter excessive medial joint laxity without medial over-release on the tibial side. It was hypothesized that over-resection of the posteromedial femoral condyle can injure the medial stabilizers, especially the posterior oblique ligament (POL) at its femoral attachments. MATERIALS AND METHODS Thirteen fixed cadaveric knees were exposed, and 3 anatomical points were identified: the posterior edge and midpoint of the POL femoral attachment, and the posterior edge of the superficial medial collateral ligament (sMCL) femoral attachment. The distance from the surface of the posteromedial femoral condyle to each point was measured. Correlations between each point and the anterior-posterior or medial-lateral dimensions of the distal femur were also calculated. RESULTS The average distances to the posterior edge and midpoint of the POL femoral attachment and the posterior edge of the sMCL femoral attachment were 13.7 mm (9.0-18.4), 17.9 mm (11.5-22.6), and 22.7 mm (14.7-29.4), respectively. There were moderate correlations between the distance to each point and the anterior-posterior or medial-lateral dimensions of the distal femur. CONCLUSIONS The minimal distance from the surface of the posteromedial condyle to the POL posterior edge was 9.0 mm. Over-resection of the posteromedial femoral condyle, even with a general TKA femoral component, might injure the POL at its femoral attachments, especially in patients with small distal femurs, while the sMCL is rarely damaged. LEVEL OF EVIDENCE Level IV.