Muscle loaded stability reflects ligament-based stability in TKA: a cadaveric study

Area of Science:

• Orthopedic Surgery
• Biomechanics
• Biomedical Engineering

Background:

• Total knee arthroplasty (TKA) aims to restore knee function and stability.
• Understanding the influence of muscle load on knee biomechanics post-TKA is crucial for optimizing patient outcomes.
• Cadaveric studies provide a controlled environment to investigate joint mechanics.

Purpose of the Study:

• To evaluate the impact of muscle load on knee kinematics and stability following TKA.
• To assess the effect of TKA surgery itself on knee kinematics and stability.
• To correlate passive knee stability with active, muscle-loaded stability.

Main Methods:

• Utilized fourteen fresh frozen cadaveric knee specimens.
• Tested knees under passive and active conditions, with and without external varus/valgus and rotational torques.
• Performed testing before and after TKA using validated in-house setups.

Main Results:

• Muscle force increased valgus (0.98°) and femoral internal rotation (4.64°).
• TKA surgery altered neutral kinematics, increasing varus (1.25°) and femoral external rotation (5.22°).
• Muscle load and TKA significantly reduced all laxities; passive laxity predicted active laxity for both rotational and varus/valgus stability.

Conclusions:

• Muscle load is a critical factor influencing knee stability after TKA.
• Functional stability post-TKA is strongly linked to passive, ligamentous stability.
• Intraoperative assessment of passive laxity is vital as it predicts functional stability, emphasizing the need for focused rehabilitation to prevent muscle atrophy.