Can normal knee kinematics be restored with unicompartmental knee replacement?
BACKGROUND
Unicompartmental replacement can be an alternative to tibial osteotomy in younger, active patients with unicompartmental knee disease. In unicompartmental replacement, the other compartments and knee ligaments are largely untouched. Therefore, it was hypothesized that the knee kinematics after unicompartmental replacement may also be unchanged. To test this hypothesis, knee kinematics and quadriceps tension were recorded before and after replacement with a unicompartmental design and then with a tricompartmental design.


METHODS
Six human cadaver knees were tested before implantation, after implantation with a bicruciate-retaining unicompartmental knee prosthesis, and after implantation with a posterior cruciate-retaining tricompartmental knee prosthesis. The unicompartmental prosthesis was initially implanted, and it was then revised to a total condylar knee replacement. The knee kinematics were measured with use of an electromagnetic tracking device while the knee was put through dynamic simulated stair-climbing under peak flexion moments of approximately 40 N-m. Quadriceps tension was also measured for all three conditions.


RESULTS
No significant differences in tibial axial rotation were noted between the intact and unicompartmental conditions. However, tricompartmental replacement significantly affected tibial axial rotation (p = 0.001). Femoral rollback was not significantly affected by either unicompartmental or tricompartmental arthroplasty. Quadriceps tension was also similar among all three conditions.


CONCLUSIONS
In this in vitro cadaver study, the tricompartmental replacement significantly changed knee kinematics while the unicompartmental replacement preserved normal knee kinematics.
Patil
Shantanu
S
Orthopaedic Research Laboratories, Scripps Clinic Center for Orthopaedic Research and Education, 11025 North Torrey Pines Road, Suite 140, La Jolla, CA 92037, USA.
Colwell
Clifford W
CW
Ezzet
Kace A
KA
D'Lima
Darryl D
DD
D000368:Aged; D000369:Aged, 80 and over; D019645:Arthroplasty, Replacement, Knee; D001696:Biomechanical Phenomena; D002102:Cadaver; D003161:Compartment Syndromes / Q000601:surgery*; D005260:Female; D006801:Humans; D007719:Knee Joint / Q000503:physiopathology*; D007720:Knee Prosthesis; D007866:Leg / Q000503:physiopathology; D008297:Male; D018482:Muscle, Skeletal / Q000503:physiopathology; D011474:Prosthesis Design; D016059:Range of Motion, Articular / Q000502:physiology