The Effects of Tibial Tray Rotation and Posterior Slope on Knee Kinematics Following Total Knee Replacement
Author(s)
Karim, Amer
Type
Thesis
Abstract
Aims
To determine the effects of tibial component rotation and posterior slope on
kinematics following Scorpio CR navigated TKR in cadaver specimens.
Methods & Results
Knee kinematics were monitored using a validated IR Navigation System. Ten
normal comparable cadaver specimens were mounted in a custom rig allowing
assessment of kinematics under various loading conditions. The specimens then
underwent Navigated TKR. The surgery was performed as per normal operating
surgical protocols by an expert knee surgeon. However an augmented tibial
component was implanted allowing the researchers to precisely modify its rotation
and posterior slope. A pneumatic cylinder attached to the quadriceps tendon was
then used to repetitively flex and extend the knee with a variety of applied loads.
Kinematics were different after TKR. Increasing posterior slope resulted in increasing
posterior position of the femur, particularly at maximum flexion. Posterior slope also
resulted in a deviation of the neutral path of motion and alteration of the normal
envelope of laxity. Tibial component malrotations over 5 degrees resulted in
deviations of the neutral path of motion without affecting the envelope of laxity.
Combined malrotations over 10 degrees with posterior slopes over 6 degrees
resulted in prosthetic subluxation under certain loading conditions.
Discussion
Knee kinematics are different after TKR. Increasing internal and external malrotation
as well as the addition of posterior slope resulted in deviations of TKR kinematics
through alteration of the neutral path of movement and or the envelope of laxity.
Combined misalignments of slope and rotation resulted in the greatest deviations
from normal kinematics, and in some cases, prosthetic subluxation. Incompatibilities
of alignment may result in increased ligament tension and component articulation
dysfunction that may contribute to premature wear and loosening. Surgeons should
be aware of this when considering the addition of posterior slope or assessing tibial
component positioning in TKR.
To determine the effects of tibial component rotation and posterior slope on
kinematics following Scorpio CR navigated TKR in cadaver specimens.
Methods & Results
Knee kinematics were monitored using a validated IR Navigation System. Ten
normal comparable cadaver specimens were mounted in a custom rig allowing
assessment of kinematics under various loading conditions. The specimens then
underwent Navigated TKR. The surgery was performed as per normal operating
surgical protocols by an expert knee surgeon. However an augmented tibial
component was implanted allowing the researchers to precisely modify its rotation
and posterior slope. A pneumatic cylinder attached to the quadriceps tendon was
then used to repetitively flex and extend the knee with a variety of applied loads.
Kinematics were different after TKR. Increasing posterior slope resulted in increasing
posterior position of the femur, particularly at maximum flexion. Posterior slope also
resulted in a deviation of the neutral path of motion and alteration of the normal
envelope of laxity. Tibial component malrotations over 5 degrees resulted in
deviations of the neutral path of motion without affecting the envelope of laxity.
Combined malrotations over 10 degrees with posterior slopes over 6 degrees
resulted in prosthetic subluxation under certain loading conditions.
Discussion
Knee kinematics are different after TKR. Increasing internal and external malrotation
as well as the addition of posterior slope resulted in deviations of TKR kinematics
through alteration of the neutral path of movement and or the envelope of laxity.
Combined misalignments of slope and rotation resulted in the greatest deviations
from normal kinematics, and in some cases, prosthetic subluxation. Incompatibilities
of alignment may result in increased ligament tension and component articulation
dysfunction that may contribute to premature wear and loosening. Surgeons should
be aware of this when considering the addition of posterior slope or assessing tibial
component positioning in TKR.
Date Issued
2010-05
Date Awarded
2012-03
Copyright Statement
Attribution NoDerivatives 4.0 International Licence (CC BY-ND)
Advisor
Amis, Andrew
Bull, Anthony
Sponsor
Stryker (Europe) Foundation
Publisher Department
Mechanical Engineering
Publisher Institution
Imperial College London
Qualification Level
Doctoral
Qualification Name
Doctor of Medicine (Research) MD (Res)