External rotational alignment of tibial component correlates with two years clinical outcomes in guided motion total knee arthroplasty: a retrospective cross-sectional study

Background Proper rotational alignment of the femoral and tibial component is critical for a successful total knee arthroplasty (TKA). However, there are no study that focused on the influence of external rotation of the tibial component have on patient reports outcomes in a guided motion TKA. This study aimed to assess the association between tibial rotational alignment and patient reported outcomes in patients with neutral alignment in all the other planes. Methods The current study was a retrospective cross-sectional study performed at a regional institutional hospital. Patients who underwent primary TKA for knee osteoarthritis with no postoperative coronal malalignment and malrotation of the femoral component were included in the study. Rotational alignment of the tibial component was evaluated using a computed tomography and its relationship between postoperative 2011 Knee Society Score was evaluated by Pearson or Spearman correlation analysis. Results The study included 24 patients, 7 of whom underwent bilateral TKA with a guided motion cruciate substituting implant. Tibial component was 6.2 ± 5.9 degrees externally rotated postoperatively. Externally rotated tibial component resulted with higher scores in walking and standing (one year, two years), and with smaller flexion angle (six months, two years) and lower satisfaction score (two years). Conclusions Tibial rotational alignment influences two years clinical outcomes in total knee arthroplasty. Excessive external rotation should be avoided in a guided motion prosthesis and in future study, threshold of rotational alignment of the tibial component should be clarified.