Extrinsic Muscle Forces Affect Ankle Loading Before and After Total Ankle Arthroplasty

Area of Science:

• Biomechanics
• Orthopedics
• Biomedical Engineering

Background:

• Joint loading is crucial for ankle osteoarthritis and total ankle arthroplasty (TAA) outcomes.
• Muscle forces, beyond body weight, significantly influence intra-articular ankle joint loading.
• Limited research exists on individual muscle contributions to ankle pressure distribution.

Purpose of the Study:

• Quantify the effect of individual muscle action on peak intra-articular pressure magnitude.
• Identify the location of the center of pressure in weight-bearing native and TAA ankles.
• Assess pressure distribution changes before and after TAA implantation.

Main Methods:

• Utilized 10 cadaveric feet to measure peak pressure and center of pressure.
• Applied force alterations to four key muscle groups: peronei, tibialis anterior, tibialis posterior, and triceps surae.
• Employed pressure-sensitive arrays and linear mixed-effects models to analyze data pre- and post-TAA prosthesis implantation.

Main Results:

• Mean peak pressures were 2 MPa (native) and 6.2 MPa (TAA).
• Triceps surae action significantly increased peak pressure in both native (p=0.001) and TAA (p=0.001) ankles.
• Muscle forces generally shifted the center of pressure posteriorly and laterally in both joint types.

Conclusions:

• Muscle force production demonstrably alters pressure distribution in native and TAA ankles.
• Findings support the role of muscle forces in joint loading, informing potential muscle training strategies.
• Results can guide the design of improved prosthetic components and inform physical therapy for osteoarthritis and TAA patients.