Increased force and contact area in the lateral compartment may predispose to arthritis progression after balanced unicompartmental knee arthroplasty: A cadaveric comparison.

Abstract

Unicompartmental knee arthroplasty (UKA) offers advantages such as faster recovery and improved function compared to total knee arthroplasty. This study evaluates the biomechanical differences in contact pressure, force, and area between conventional and robotic-assisted UKA techniques. Sixteen fresh-frozen cadaveric lower limb specimens underwent UKA, with eight using standardized cutting jigs (conventional UKA) and eight using CORI robotic-assisted technology. FlexiForce (Tekscan) sensors measured contact pressure, force, and area in the medial (replaced) and lateral (native) compartments during controlled knee extension from 90° flexion to 0°. Biomechanical parameters were statistically compared. Medial contact pressure increased significantly from 251.73 KPa at 90° to 1863.83 KPa at 0° (p < 0.05), while lateral pressures remained lower, ranging from 319.83 KPa to 733.94 KPa (p < 0.05). The lateral compartment exhibited consistently higher contact areas, increasing from 81.46 mm2 at 90° to 134.38 mm2 at 0°, compared to the medial compartment's 43.91 mm2 to 44.65 mm2 (p < 0.05). Force values were also higher in the lateral compartment across all angles, peaking at 97.84 N compared to 83.01 N medially at 0° (p < 0.05). No significant differences were observed between conventional and robotic-assisted techniques (p > 0.05). Both UKA techniques demonstrated comparable biomechanical outcomes. Achieving soft tissue balance remains critical for reducing medial compartment pressure and optimizing load distribution. The lateral compartment exhibits higher forces and contact areas compared to the medial compartment, potentially accelerating the development of arthritis in the lateral side after UKA due to load imbalance.