Achilles tendon moment arm changes with total ankle arthroplasty

Area of Science:

• Orthopedics
• Biomechanics
• Surgical Innovation

Background:

• Total ankle arthroplasty (TAA) primarily focuses on pain and function, with limited research on its biomechanical effects.
• The Achilles tendon moment arm is crucial for ankle function and may be altered by TAA.
• Understanding these biomechanical changes is essential for optimizing TAA outcomes.

Purpose of the Study:

• To investigate the impact of TAA on the Achilles tendon moment arm using multiple assessment methods.
• To determine if TAA significantly alters the plantarflexion moment arm of the Achilles tendon.
• To explore the relationship between pre- and post-operative moment arm values and the influence of talar dome position.

Main Methods:

• Prospective study involving ten patients undergoing TAA.
• Measurement of Achilles tendon moment arm using ultrasound and 3D motion capture pre- and post-surgery.
• Analysis of standing sagittal-plane radiographs to assess anterior-posterior distance between the calcaneus and talar dome center.

Main Results:

• Significant absolute changes in the 3D Achilles tendon moment arm were observed post-TAA (9.6 mm via ultrasound).
• Radiographic measurements showed significant changes (4.6% of calcaneus length) but lacked pre- and post-operative correlation.
• Postoperative 3D moment arm was only partially explained by preoperative values (r² = 0.460) and influenced by talar dome position (r² = 0.497).

Conclusions:

• TAA leads to significant, though not always predictable, alterations in the Achilles tendon moment arm.
• Changes in the moment arm are partially attributable to shifts in the talar dome's position after TAA.
• Further research is needed to fully elucidate the biomechanical consequences of TAA on ankle joint mechanics and long-term function.