Quadriceps force during knee extension in different replacement scenarios with a modular partial prosthesis

Area of Science:

• Orthopedic surgery
• Biomechanics
• Biomedical engineering

Background:

• Bi-cruciate retaining knee replacement preserves knee kinematics.
• Limited data exists on combined medial and patellofemoral arthroplasty's biomechanical effects.
• This study investigates quadriceps force changes with partial knee replacement systems.

Purpose of the Study:

• To evaluate the impact of different modular partial knee replacement scenarios on quadriceps force.
• To assess the biomechanical consequences of medial unicondylar and trochlear replacements.
• To compare isokinetic knee extension force requirements post-implantation.

Main Methods:

• Ten human knee specimens were tested in a kinematic knee simulator.
• Isokinetic extension cycles with a 31 Nm moment were simulated.
• Quadriceps extension force was measured before and after medial unicondylar and trochlear replacements.

Main Results:

• Quadriceps force curves exhibited sinusoidal characteristics.
• Medial replacement slightly increased maximum quadriceps force (1510 N vs. 1585 N).
• Subsequent trochlear replacement further increased force (1801 N), but mid-flexion (10-50°) showed no significant difference.

Conclusions:

• Bi-compartmental knee replacement necessitates increased maximum quadriceps force for extension.
• Near-physiological mid-flexion suggests potential stability advantages over total knee arthroplasty.
• Consideration of increased quadriceps force is crucial for bi-compartmental arthroplasty.