Differences between mechanically stable and unstable chronic ankle instability subgroups when examined by arthrometer...

Area of Science:

• Orthopedics
• Biomechanics
• Sports Medicine

Background:

• Chronic ankle instability diagnosis remains debated, particularly regarding mechanical factors.
• Objective measurement of mechanical ankle instability is crucial for effective treatment.
• Previous studies lack consensus on the role of mechanical deficits in functional outcomes.

Purpose of the Study:

• To analyze the known-group and diagnostic validity of an ankle arthrometer for measuring mechanical ankle instability.
• To evaluate the relationship between mechanical ankle laxity and functional limitations in chronic ankle instability.

Main Methods:

• 41 functionally unstable ankles were assessed using manual stress testing and an ankle arthrometer.
• Ankle stiffness (40-60 N) was calculated from load-displacement curves.
• Known-group validity, diagnostic validity (2x2 contingency table), and correlation with the Foot and Ankle Ability Measure (FAAM-G) were determined.

Main Results:

• Mechanically unstable ankles exhibited significantly lower stiffness values (p<0.001).
• The ankle arthrometer showed high diagnostic validity (85% accuracy, 81% sensitivity, 93% specificity) with a 5.1 N/mm cut-off.
• A weak correlation was found between arthrometer stiffness and FAAM-G scores (r=0.286-0.316, p=0.04-0.07).

Conclusions:

• The ankle arthrometer is a valid and reliable tool for objectively diagnosing mechanical ankle instability.
• A direct correlation between mechanical ankle laxity and functional deficits was not clearly established in this cohort.
• Further research is needed to fully elucidate the complex interplay between mechanical and functional aspects of chronic ankle instability.