Current concepts and a glimpse into the future of partial knee replacement around the knee
Background: Unicompartmental knee arthroplasty (UKA) is an established intervention for end-stage single-compartment osteoarthritis, offering advantages over total knee arthroplasty (TKA) including bone stock preservation, maintenance of native kinematics, and accelerated recovery. Despite these benefits, UKA is associated with higher revision rates in registry data, frequently attributed to component malpositioning and limb alignment errors.
Objective: This review evaluates the current clinical status of medial, lateral, and patellofemoral arthroplasty, examining the evolution of implant designs, modularity in multi-compartmental disease, and the role of robotic-assisted technology in improving surgical precision.
Key Points: Medial UKA utilizes either fixed or mobile-bearing designs; both demonstrate approximately 90% survivorship at 15 years, though mobile bearings carry a specific risk of insert dislocation. Lateral UKA, while technically demanding due to unique compartment kinematics, achieves comparable long-term outcomes when utilizing fixed-bearing implants. Patellofemoral arthroplasty (PFA) has transitioned from first-generation inlay designs to third-generation onlay components, which optimize patellar tracking and reduce instability. For bicompartmental disease, modular unlinked arthroplasty allows independent component alignment tailored to patient anatomy, yielding superior results compared to monolithic designs. Robotic-assisted systems—classified as active or semi-active—utilize 3D modeling and real-time feedback to enhance bone resection accuracy and soft tissue balancing. While these technologies improve component positioning and reduce iatrogenic soft tissue trauma, middle- to long-term functional outcomes remain comparable to conventional manual techniques.
Conclusion: Partial knee arthroplasty provides a bone-conserving alternative to TKA for isolated or bicompartmental disease. The integration of advanced onlay PFA designs and robotic-assisted precision addresses historical alignment challenges, potentially enhancing long-term implant survivorship and clinical efficacy.
