Posterolateral ankle ligament injuries affect ankle stability: a finite element study.

Area of Science:

• Biomechanics
• Orthopedics
• Sports Medicine

Background:

• Posterolateral ankle instability is observed in patients despite normal anterior drawer tests and intact anterior talofibular ligament (ATFL).
• Stress radiography reveals increased posterior tibiotalar joint space, indicating ligamentous laxity.
• Surgical findings confirm intact ATFL with laxity in posterolateral ligaments.

Purpose of the Study:

• To elucidate the mechanism of posterolateral ankle instability.
• To quantify the contribution of specific posterolateral ligaments to ankle stability.

Main Methods:

• A finite element model of the ankle was developed.
• Simulations involved sequentially cutting posterolateral ligaments (PTFL, CFL, PITFL).
• Ankle motion, including tibia rotation under load across five forefoot positions, was analyzed.

Main Results:

• Tibia external rotation correlated with negative difference values, while internal rotation showed positive results.
• Cutting the PTFL with CFL or PITFL resulted in 2-3 mm talar displacement.
• Combined PTFL and CFL transection led to 2.21-2.76 mm talar displacement.
• PITFL transection increased talar displacement by 2-5 mm.

Conclusions:

• Posterior talofibular ligament (PTFL) and calcaneofibular ligament (CFL) are critical for ankle stability.
• Severe injury to CFL and PTFL compromises posterolateral ankle stability.
• The PITFL is essential for subtalar joint stability.