Abstract
BACKGROUND
UKA is functionally superior to TKA, with kinematics similar to native knees, nevertheless, UKA implants are used in less than 10% of cases. While advantages of UKA are recognized, ACL-deficiency is generally considered a contraindication. The hypothesis of this study was that fix bearing UKA in ACL-deficient knees, with appropriate adaptation of implant placement, would result in similar kinematic trends to conventional UKA with an intact ACL.
METHODS
Ten conventional UKA patients were compared to eight patients with the same implant but a deficient ACL. A 50% tibial slope reduction was applied to compensate for instability resulting from the deficient ACL. Knee kinematics were evaluated using a moving fluoroscope allowing to track the knee joint during deep knee bend, level walking, ramp descent and stair descent. The results were further compared to six TKA patients.
RESULTS
During standing, a posterior shift of the femur was observed for the ACL-deficient UKA patients compared to conventional UKA patients. This posterior shift was also present during the first 25% of deep knee bend. Most parameters revealed no difference in range of motion across all activities between the two UKA groups. This is in contrast to TKA patients showing different motion trends and decreased range of motion.
CONCLUSIONS
Despite the posterior femoral shift due to ACL-deficiency, both UKA groups showed similar kinematic trends, indicating that posterior tibial slope reduction can partially compensate for ACL function. This confirmed our hypothesis that fix bearing UKA can be a viable treatment option for selected ACL-deficient patients.
