Anterior tibial curved cortex is a reliable landmark for tibial rotational alignment in total knee arthroplasty

BACKGROUND Rotational alignment of the tibial component is important for long-term success of total knee arthroplasty (TKA). This study aimed to compare five axes in normal and osteoarthritic (OA) knees to determine a reliable landmark for tibial rotational alignment in TKA. METHODS One hundred twenty patients with OA knees and 40 with normal knees were included. The angle between a line perpendicular to the surgical transepicondylar axis and each of five axes were measured on preoperative computed tomography. The five axes were as follows: a line from the center of the posterior cruciate ligament (PCL) to the medial border of the patellar tendon (PCL-PT), medial border of the tibial tuberosity (PCL-TT1), medial one-third of the tibial tuberosity (PCL-TT2), and apex of the tibial tuberosity (PCL-TT3), as well as the anteroposterior axis of the tibial prosthesis along the anterior tibial curved cortex (ATCC). RESULTS For all five axes tested, the mean angles were smaller in OA knees than in normal knees. In normal knees, the angle of the ATCC axis had the smallest mean value and narrowest range (1.6° ± 2.8°; range, -1.7°-7.7°). In OA knees, the mean angle of the ATCC axis (0.8° ± 2.7°; range, -7.9°-9.2°) was larger than that of the PCL-TT1 axis (0.3° ± 5.5°; range, -19.7°-10.6°) (P = 0.461), while the angle of the ATCC axis had the smallest SD and narrowest range. CONCLUSION The ATCC was found to be the most reliable and useful anatomical landmark for tibial rotational alignment in TKA.