Are undesirable contact kinematics minimized after kinematically aligned total knee arthroplasty? An intersurgeon analysis of consecutive patients.
OBJECTIVE
Tibiofemoral contact kinematics or knee implant motions have a direct influence on patient function and implant longevity and should be evaluated for any new alignment technique such as kinematically aligned total knee arthroplasty (TKA). Edge loading of the tibial liner and external rotation (reverse of normal) and adduction of the tibial component on the femoral component are undesirable contact kinematics that should be minimized. Accordingly, this study determined whether the overall prevalence of undesirable contact kinematics during standing, mid kneeling near 90 degrees and full kneeling with kinematically aligned TKA are minimal and not different between groups of consecutive patients treated by different surgeons.


METHODS
Three surgeons were asked to perform cemented, kinematically aligned TKA with patient-specific guides in a consecutive series of patients with their preferred cruciate-retaining (CR) implant. In vivo tibiofemoral contact positions were obtained using a 3- to 2-dimensional image registration technique in 69 subjects (Vanguard CR-TKA N = 22, and Triathlon CR-TKA N = 47).


RESULTS
Anterior or posterior edge loading of the tibial liner was not observed. The overall prevalence of external rotation of the tibial component on the femoral component of 6 % was low and not different between surgeons (n.s.). The overall prevalence of adduction of the tibial component on the femoral component of 4 % was low and not different between surgeons (n.s.).


CONCLUSIONS
Kinematically aligned TKA minimized the undesirable contact kinematics of edge loading of the tibial liner, and external rotation and adduction of the tibial component on the femoral component during standing and kneeling, which suggests an optimistic prognosis for durable long-term function.


METHODS
III.
Department of Mechanical Engineering, University of California, Davis, Davis, CA, USA.
Stephen M
SM
Howell
Esther E
EE
Hodapp
Joseph V
JV
Vernace
Maury L
ML
Hull
Thomas D
TD
Meade
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D019645:Arthroplasty, Replacement, Knee / Q000295:instrumentation / Q000379:methods*; D001696:Biomechanical Phenomena; D017760:Bone Malalignment / Q000209:etiology / Q000517:prevention & control*; D005260:Female; D005500:Follow-Up Studies; D006305:Health Status Indicators; D006801:Humans; D021621:Imaging, Three-Dimensional; D007719:Knee Joint / Q000503:physiopathology* / Q000601:surgery; D007720:Knee Prosthesis; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D008953:Models, Anatomic; D020370:Osteoarthritis, Knee / Q000503:physiopathology / Q000601:surgery*; D011183:Postoperative Complications / Q000517:prevention & control*; D011300:Preoperative Care / Q000379:methods*; D020127:Recovery of Function; D012399:Rotation; D025321:Surgery, Computer-Assisted / Q000295:instrumentation / Q000379:methods*; D016896:Treatment Outcome