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[Research on the reliability of the Akagi line as a reference axis to guide for rotational alignment of the proximal tibial component in total knee arthroplasty].

OBJECTIVE
To study on the reliability of the Akagi line as a reference axis to guide for rotational alignment of the proximal tibial component in total knee arthroplasty (TKA) the rotational alignment reference bony landmarks of the proximal tibial component on magnetic resonance image (MRI) were measured.


METHODS
From January 2010 to December 2013, 80 normal knees of Chinese volunteers including 35 males and 45 females with an average age of (35.4±6.1) years were reviewed. The images of the knees were obtained by MRI. The surgical epicondylar axis (STEA) was identified in the femoral transverse sections and then was projected to the side of tibia, forming the SETA'. A line connecting the medial border of the patellar tendon and the middle of the posterior cruciate ligament insertion (Akagi line) and its vertical line (AK), as well as a line connecting the medial 1/3 of the patellar tendon and the middle of the posterior cruciate ligament insertion and its vertical line (AP), were identified in the tibial transverse sections. The angles were measured between the AK, AP and STEA'.


RESULTS
The angle between AK and STEA' was (0.59±2.07)°, and there was no significant difference between the two lines (t=-2.54, P=0.13). The mean angle between AP and STEA' was (3.21±2.04)°, and there was a significant difference between the two lines (t=14.05, P<0.05). There was a significant difference between the AK and AP (t=-11.68, P<0.05).


CONCLUSION
The reliability of the Akagi line as a reference axis to guide for rotational alignment of the proximal tibial component in TKA is good.