Posterior cruciate function following total knee arthroplasty. A biomechanical study

Area of Science:

• Orthopedic Surgery
• Biomedical Engineering
• Biomechanics

Background:

• The posterior cruciate ligament (PCL) plays a crucial role in knee joint stability and function.
• Total knee arthroplasty (TKA) aims to restore knee function, but PCL biomechanics after surgery remain a concern.

Purpose of the Study:

• To quantify PCL strain during simulated stair ascent/descent in cadaveric knees before and after TKA.
• To evaluate the impact of different TKA designs (cruciate-retaining, -excising, -substituting) on PCL function, femoral rollback, and extensor efficiency.

Main Methods:

• Eight fresh cadaveric knees were tested using a simulated stair climbing protocol.
• Strain gauges, load cells, electrogoniometers, and displacement transducers measured PCL strain, forces, and kinematics.
• Testing included native knees, anterior cruciate ligament (ACL) cut, and post-TKA states with various prostheses.

Main Results:

• Cruciate-retaining TKAs restored normal PCL strain in only 37% of trials.
• Femoral rollback decreased significantly with all TKA types (36-70%), impacting extensor efficiency (15-19% loss).
• PCL strain was sensitive to tibial insert thickness, and achieving normal PCL loading with varus/valgus stability was challenging.

Conclusions:

• Current TKA designs struggle to consistently replicate normal PCL function and biomechanics.
• Restoring native PCL strain and kinematics remains a significant challenge in total knee replacement surgery.
• Tibial insert thickness is a critical factor influencing PCL strain and overall knee joint stability post-TKA.