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
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.
Clinical Relevance: The results of this in vitro biomechanical
cadaver study suggest that the unicompartmental design has the potential to
restore (or preserve) normal kinematic function better than tricompartmental
implants. Restoration of normal knee function may benefit patient
rehabilitation, extensor function, implant survival, and wear.