Assessing mechanical ankle instability via functional 3D stress-MRI - A pilot study.

Area of Science:

• Orthopedics
• Radiology
• Biomechanics

Background:

• Assessing mechanical deficits in chronic ankle instability (CAI) is challenging.
• Distinguishing functional ankle instability (FAI) from mechanical ankle instability (MAI) and evaluating surgical techniques requires better quantitative methods.
• A novel functional 3D stress ankle MRI approach is proposed to address these limitations.

Purpose of the Study:

• To evaluate the applicability of a novel functional 3D stress ankle MRI technique for assessing mechanical ankle instability.
• To quantitatively measure mechanical deficits in patients with MAI.
• To explore the potential clinical benefit of this new imaging modality.

Main Methods:

• A custom ankle arthrometer was used for precise foot positioning and axial loading (up to 500 N).
• A 3D MRI protocol assessed four parameters: 3D cartilage contact area (CCA) fibulotalar, tibiotalar horizontal and vertical, and intermalleolar distance.
• Measurements were taken under six conditions (neutral, plantarflexion-supination, dorsiflexion-pronation, with and without loading) in 10 individuals (7 MAI, 3 controls).

Main Results:

• The MAI group exhibited a significantly greater reduction in lateral osseous constraint during plantarflexion-supination compared to controls (CCA fibulotalar: 69% vs. 30%).
• Weight-bearing surface reduction in plantarflexion-supination was more pronounced in the MAI group (CCA tibiotalar horizontal: -49% vs. -28% in controls).
• The novel technique demonstrated differences between MAI patients and healthy controls.

Conclusions:

• The functional 3D stress ankle MRI is a valuable tool for assessing mechanical ankle instability.
• This technique offers potential clinical benefits for evaluating individual mechanical deficits in patients.
• Further research is necessary to establish the prognostic value of this novel imaging technique.