Bicruciate-retaining total knee arthroplasty reproduces in vivo kinematics of normal knees to a lower extent than unicompartmental knee arthroplasty.
PURPOSE
This study aimed to clarify the natural knee kinematics provided by bicruciate-retaining total knee arthroplasty (BCR-TKA) compared with those of unicompartmental knee arthroplasty (UKA) and normal knees.


METHODS
Volunteers and patients who had undergone UKA and BCR-TKA with anatomical articular surface performed squatting motion under fluoroscopy. To estimate the knee's spatial position and orientation, a two-dimensional/three-dimensional registration technique was used. The rotation angle and anteroposterior translation of the medial and lateral sides of the femur relative to the tibia in each flexion angle were directly evaluated using the same local coordinate system and their differences amongst the three groups were analysed using two-way analysis of variance and Bonferroni post hoc pairwise comparison.


RESULTS
From 0° to 10° of flexion, the femoral external rotation angle of BCR-TKA knees was significantly greater than that of normal and UKA knees and the medial side of BCR-TKA knees was significantly more anteriorly located than that of normal and UKA knees. From 40° to 50° of flexion, the medial side of UKA knees was significantly more posteriorly located than that of normal and BCR-TKA knees. From 30° to 120° of flexion, the lateral side of BCR-TKA knees was significantly more anteriorly located than that of normal and UKA knees.


CONCLUSION
The in vivo kinematics of BCR-TKA knees reproduces those of normal knees to a lower extent than those of UKA knees. Thus, BCR-TKA with anatomical articular surface reproduces in vivo kinematics of normal knees to a lower extent than UKA.


LEVEL OF EVIDENCE
III.
['Kono|Kenichi|K|', 'Inui|Hiroshi|H|http://orcid.org/0000-0002-3605-2238', 'Tomita|Tetsuya|T|', 'Yamazaki|Takaharu|T|', 'Taketomi|Shuji|S|', 'Tanaka|Sakae|S|']
D000328:Adult D000368:Aged D019645:Arthroplasty, Replacement, Knee D001696:Biomechanical Phenomena D016022:Case-Control Studies D005260:Female D005471:Fluoroscopy D006801:Humans D007091:Image Processing, Computer-Assisted D007719:Knee Joint D008297:Male D016059:Range of Motion, Articular D012399:Rotation
Bicruciate-retaining total knee arthroplasty Kinematics Unicompartmental knee arthroplasty Squatting