Abstract
Total knee replacement designs claim characteristic kinematic performance that is rarely assessed in patients. In the present study, in vivo kinematics of a new prosthesis design was measured during activities of daily living. This design is posterior stabilized for which spine-cam interaction coordinates free axial rotation throughout the flexion-extension arc by means of a single radius of curvature for the femoral condyles in the sagittal and frontal planes. Fifteen knees were implanted with this prosthesis, and 3D video-fluoroscopic analysis was performed at 6-month follow-up for three motor tasks. The average range of flexion was 70.1° (range: 60.1-80.2°) during stair-climbing, 74.7° (64.6-84.8°) during chair-rising, and 64.1° (52.9-74.3°) during step-up. The corresponding average rotation on the tibial base-plate of the lines between the medial and lateral contact points was 9.4° (4.0-22.4°), 11.4° (4.6-22.7°), and 11.3° (5.1-18.0°), respectively. The pivot point for these lines was found mostly in the central area of the base-plate. Nearly physiological range of axial rotation can be achieved at the replaced knee during activities of daily living.
Highlights
Total knee arthroplasty (TKA) continues to be an efficient surgical treatment, as evidenced by its excellent survivorship and long-term results.[1]
This assessment was performed by assessing replaced knee kinematics during activities of daily living by means of video-fluoroscopy, analyzing rotations and relevant pivot of the contactlines during motion
We hypothesized that in a knee replaced with this design, a physiological range of axial rotation can be achieved during activities of daily living
Summary
Total knee arthroplasty (TKA) continues to be an efficient surgical treatment, as evidenced by its excellent survivorship and long-term results.[1]. In vivo gait analysis studies, based on kinematics, kinetics, and electromyography of the lower limbs, showed that overall function cannot be fully restored in fixed bearing TKA.[17] Fluoroscopy-based analyses[4,5,18,19,20,21,22,23,24] revealed that the non-physiological kinematics patterns at the replaced joint in activities of daily living are accounted for by paradoxical anterior translation and reverse or insufficient rotation of the tibio-femoral contact-line during flexion, i.e., lateral pivoting This rotation is usually calculated on the tibial base-plate, for the line joining the projection points of the two medial and lateral prosthetic femoral condyles at minimum distances from the base-plate.[25] Bi-directional rotation of this contact-line is usually interpreted as internal/external (or axial) rotation, and the bi-dimensional location of the single point at minimum distance from all these lines over the entire flexion arc as the 2D pivot point. We hypothesized that in a knee replaced with this design, a physiological range of axial rotation can be achieved during activities of daily living
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