Restoration of constitutional alignment in TKA leads to more physiological strains in the collateral ligaments.
OBJECTIVE
Currently, controversy exists whether restoration of neutral mechanical alignment should be attempted in all patients undergoing TKA. Our hypothesis was that restoration of constitutional rather than neutral mechanical alignment may in theory lead to a more physiological strain pattern in the collateral ligaments; therefore, it could potentially be beneficial to patients. Thus, the aim of this study was to measure collateral ligament strains during three motor tasks in the native knee and compare them with the strains noted after TKA in different post-operative alignment conditions.


METHODS
Six cadaver specimens (approval number ML4190 from the Research Ethics Committee of University of Leuven, Belgium) were examined using a validated knee kinematics rig under physiological loading conditions. The effect of coronal malalignment was evaluated by using custom-made tibial implant inserts that induced different alignment conditions. The study of six specimens allows us to show that a difference in the mean strains in MCL and LCL of 3.6 and 5.8 %, respectively, was statistically significant with a probability (power) of 0.8.


RESULTS
The results indicated that after TKA insertion, the strains in the collateral ligaments closely resembled the pre-operative pattern of the native knee specimens when constitutional alignment was restored. Restoration to neutral mechanical alignment was associated with greater collateral strain deviations from the native knee.


CONCLUSIONS
Based upon this study, it was concluded that restoration of constitutional alignment within a "safe zone" of ±2° during TKA leads to more physiological peri-articular soft tissue strains during loaded as well as unloaded motor tasks.
Department of Orthopedic Surgery and Traumatology, University Hospital Pellenberg, Katholieke Universiteit Leuven, 3012, Pellenberg, Belgium. hendrik.delport@ortho-expert.be.|Faculty of Engineering Science, Biomechanics Section, KU Leuven, Louvain, Belgium. hendrik.delport@ortho-expert.be.
Hendrik
H
Delport
European Centre for Knee Research, Smith & Nephew, Louvain, Belgium.|Faculty of Engineering Science, Biomechanics Section, KU Leuven, Louvain, Belgium.
Luc
L
Labey
European Centre for Knee Research, Smith & Nephew, Louvain, Belgium.|BEAMS Department, École Polytechnique de Bruxelles, Université Libre de Bruxelles, Brussels, Belgium.
Bernardo
B
Innocenti
European Centre for Knee Research, Smith & Nephew, Louvain, Belgium.
Ronny
R
De Corte
Faculty of Engineering Science, Biomechanics Section, KU Leuven, Louvain, Belgium.
Jos
J
Vander Sloten
Department of Orthopedic Surgery and Traumatology, University Hospital Pellenberg, Katholieke Universiteit Leuven, 3012, Pellenberg, Belgium.
Johan
J
Bellemans
D000368:Aged; D000369:Aged, 80 and over; D019645:Arthroplasty, Replacement, Knee / Q000379:methods*; D001696:Biomechanical Phenomena / Q000502:physiology; D002102:Cadaver; D017885:Collateral Ligaments / Q000503:physiopathology*; D005260:Female; D006801:Humans; D008297:Male; D013180:Sprains and Strains / Q000503:physiopathology*; D016474:Weight-Bearing / Q000502:physiology