Design
• Minimally constrained prosthesis where the polyethylene can rotate on the tibial baseplate
• PCL is removed at time of surgery
Indications
• Young, active patients (relative indication)
• Varus deformity < 10 degrees – valgus deformity < 15 degrees
Advantages
• Theoretically reduces polyethylene wear
• Increased contact area reduces pressures placed on polyethylene (pressure=force/area)
Disadvantages
• Bearing spin-out
• Mechanism
• Occurs as a result of a loose flexion gap
• Tibia rotates behind femur
• Treatment
• Initial
• Closed reduction
• Final
• Revision to address loose flexion gap