Quadriceps function after TKA--an in vitro study in a knee kinematic simulator

Area of Science:

• Biomechanics
• Orthopedic Surgery
• Musculoskeletal Research

Background:

• Total knee arthroplasty (TKA) is a common procedure for knee osteoarthritis.
• Understanding the forces on the quadriceps muscle post-TKA is crucial for rehabilitation.
• The extensor mechanism's function after TKA can be affected by prosthesis design.

Purpose of the Study:

• To quantify the quadriceps force required for knee extension during isokinetic cycles.
• To compare pre-operative and post-operative quadriceps forces following TKA.
• To investigate the influence of different TKA prostheses on quadriceps force.

Main Methods:

• In vitro study using a kinematic knee simulating machine with human knee specimens (n=8).
• Simulated isokinetic knee extension with a constant extension moment (31 Nm) applied via a hydraulic cylinder to the quadriceps tendon.
• Measured quadriceps forces before and after implantation of two different knee prostheses (Interax and LCS).

Main Results:

• Peak quadriceps forces reached up to 1238.9 N.
• The Interax prosthesis with patellar resurfacing led to a significant increase in quadriceps force (13.9%, P=0.003).
• The LCS prosthesis also showed a significant increase in quadriceps force (6.6%, P=0.007).

Conclusions:

• Total knee arthroplasty significantly alters the quadriceps force required for knee extension.
• Prosthesis type and patellar resurfacing influence the magnitude of this force increase.
• Findings help clarify postoperative challenges related to the knee's extensor mechanism after TKA.