Native rotational knee kinematics is restored after lateral UKA but not after medial UKA
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The aim of this study was to compare the intraoperative kinematics of medial and lateral unicompartmental knee arthroplasty (UKA) with those of the native knee using a navigation system.
Six fresh-frozen cadaveric knees were included in the study. Medial UKA was performed in all right knees and lateral UKA was performed in all left knees. All UKA procedures were performed with a computerised navigation system. The tibial internal rotation angle and coronal alignment of the mechanical axis during passive knee flexion were assessed as rotational and varus/valgus kinematics before and after surgery using the navigation system.
The rotation angles of the tibia in the early flexion phase of medial UKA were significantly larger than those of native knees (p = 0.008 at minimum knee flexion, p = 0.008 at 0° knee flexion). The rotational kinematics of lateral UKA was similar to those of the native knees throughout knee flexion. There were no significant differences in varus/valgus kinematics between native and UKA knees.
The rotational kinematics of the native knee was not restored after medial UKA but was preserved after lateral UKA. There were no significant differences in the varus/valgus kinematics after either medial or lateral UKA when compared with those of the native knees. Thus, the geometry of the medial tibial articular surface is a determinant of the ability to restore the rotational kinematics of the native knee. Surgeons and implant designers should be aware that the anatomical medial articular geometry is an important factor in restoration of the native knee kinematics after knee arthroplasty.
KeywordsNavigation system Partial knee arthroplasty Unicompartmental knee arthroplasty Intraoperative kinematics Cadaveric study
Total knee arthroplasty
KW carried out the kinematic measurements, performed the statistical analysis, and drafted the manuscript. DH participated in the design of the study and performed the UKA surgery. TT and AN assisted with the UKA surgery. IT and YT helped to coordinate the study. TG and KS helped to draft the manuscript. All authors read and approved the final version of the manuscript.
Compliance with ethical standards
Conflict of interest
The authors declare that they have no competing interests.
All performed procedures were approved by the institutional review board of Tokushima University Hospital (the ID number of approval was 2068-1) and done in accordance with the 1964 Declaration of Helsinki and its later amendments for comparable ethical standards.
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