Purpose: The purpose of the present study was to determine whether the axes aligned with the sulcus between the tibial spines and the middle of the posterior cruciate ligament at the knee and with the tibialis anterior tendon at the ankle provide a neutral rotational and coronal alignment of the tibial component in total knee arthroplasty (TKA).
Methods: In a cohort of 45 TKA patients, CT scans were taken to quantify coronal and rotational positioning of the components. All patients received a posterior stabilised total knee replacement with a fixed insert (PFC Sigma; DePuy Orthopaedics, Inc; Warsaw, IN, USA). The tibial guide was aligned with the sulcus between the tibial spines and the middle of the posterior cruciate ligament at the knee and with the tibialis anterior tendon at the ankle.
Results: The average post-operative coronal mechanical alignment was 1° varus (range 4.5° varus-1.5° valgus; SD ±1.51). The average post-operative rotational deviation from the transepicondylar axes (TEA) was 0.78° of internal rotation (1.50° of internal rotation - 3.5° of external rotation) for the tibial component. The whole-extremity mechanical axis deviation was outside the tolerance range of 3° in 4 patients (8.9 %). Deviation of the tibial component rotational position relative to the TEA was 3° or less in 94.5 % of the patients.
Conclusions: When the tibial component is aligned using the axis drawn from the centre of the PCL to the sulcus between the tibial spines on the proximal tibia and to the tibialis anterior tendon at the ankle, good alignment will be achieved in both the coronal and axial planes.
Level of evidence: IV.