Abstract
Background
Rotational alignment is important for the long-term success and good functional outcome of total knee arthroplasty (TKA). While the surgical transepicondylar axis (sTEA) is the generally accepted landmark on the distal femur, a precise and easily identifiable anatomical landmark on the tibia has yet to be established. Our aim was to compare five axes on the proximal tibia in normal and osteoarthritic (OA) knees to determine the best landmark for determining rotational alignment during TKA.
Methods
One hundred twenty patients with OA knees and 30 without knee OA were recruited for the study. Computed tomography (CT) images were obtained and converted through multiplanar reconstruction so the angles between the sTEA and the axes of the proximal tibia could be measured. Five AP axes were chosen: the line connecting the center of the posterior cruciate ligament(PCL) and the medial border of the patellar tendon at the cutting level of the tibia (PCL-PT), the line from the PCL to the medial border of the tibial tuberosity (PCL-TT1), the line from the PCL to the border of the medial third of the tibia (PCL-TT2), the line from the PCL to the apex of the tibia (PCL-TT3), and the AP axis of the tibial prosthesis along with the anterior cortex of the proximal tibia (anterior tibial curved cortex, ATCC).
Results
In OA knees, the mean angles were less than those in normal knees for all 5 axes tested. In normal knees, the angle of the ATCC axis had the smallest mean value (1.6° ± 2.8°) and the narrowest range. In OA knees, the angle of the PCL-TT1 axis had the smallest mean value (0.3° ± 5.5°); however, the standard deviation (SD) and range were wider than that of the angle of the ATCC axis. The mean angle of the ATCC axis was larger (0.8° ± 2.7°) than the angle of the PCL-TT1 axis, but the difference was not statistically significant (P =0.461). The angle of the ATCC axis had the smallest SD and the narrowest range.
Conclusion
In OA knees, the AP axis of the proximal tibia showed greater internal rotation compared with normal knees. In our study, the ATCC was found to be the most reliable and useful anatomical landmark for tibial rotational alignment in TKA.
