UCSF

The Effects of Recurrent Lateral Ankle Sprains and Postural Control on Biomechanics during Functional Movement

Timothy J. Gilleran

Study Design: Cross ±sectional

Objectives: Study 1: identify relationships between physical and functional impairments and the dynamic postural stability index (DPSI) scores in participants with and without recurrent lateral ankle sprains (RLAS). Study 2: To examine whether participants with recurrent lateral ankle sprain and postural instability (RLAS±PI) are more likely than participants without RLAS±PI to have concurrent evidence of changes in joint biomechanics of the ankle, knee, hip, pelvis and trunk during jump landings.

Background: Recurrent lateral ankle sprains are common injuries which may lead to changes in postural control and joint biomechanics. The association between DPSI and clinical impairments is currently unknown. Establishing a relationship between a dynamic measure of postural stability and clinical impairments will assist clinicians in prioritizing their examination. The contributions of RLAS and postural instability to lower extremity and trunk biomechanics during functional movements are currently unclear. Understanding the biomechanics of functional movements in subjects with RLAS±PI will inform clinicians and researchers about selected postural control strategies.

Methods: In study 1, examinations of DPSI scores and clinical impairments were performed on 23 participants (5 male, 18 female, age: 26.8 ± 4.2) with RLAS and 14 participants without RLAS (8 male, 6 female, age: 27.1 ± 3.5). Jump landings were examined using data acquired by a force platform (1000 Hz). Associations of DPS and clinical measures were evaluated using bivariate correlations (p<0.05). Group mean differences of continuous clinical outcome measures were examined using MANCOVA; and categorical data were evaluated with chi square test (p<0.05). In study 2, the landing phase (initial contact to one second) of a jump onto a single limb was examined with a force platform (1000 Hz) and a 10 camera motion capture system (250 Hz) with a full body marker set. Participants included 9 with RLAS-PI (4 female, 5 male, age: 28.1 ± 4.0) and 12 controls (6 female, 5 male, age: 26.2 ± 2.7). Group mean differences in clinical measures, joint kinematics and kinetics were examined using independent t-tests (p<0.05).

Results: Study 1 identified weak and non-significant correlations between all DPSI scores and clinical tests. Significant group differences in questionnaires, joint stability measures and the Y Excursion Balance Test were identified, but no differences in strength, range of motion, side hop performance, and directional or composite stability indices were identified. Study 2 identified significant group differences in ankle, knee, hip, pelvis, and trunk biomechanics between RLAS±PI and control participants. Compared to controls, participants with RLAS±PI had a significant decrease in dorsiflexion excursion angles (p = 0.034), and increase in knee joint power (p = 0.039) and peak trunk flexion angles (p = 0.038).

Conclusion: The selected physical and functional impairment measures were not related to this measure of dynamic postural control. RLAS participants perceive significant deficits in their functional ankle stability and disability, but quantitative measures of their functional performance and dynamic postural control were unable to identify group differences. In study 2, the RLAS±PI group utilized different movement strategies to perform the jump landing task successfully. Reduced ankle joint excursions may reflect a "protective stiffening" strategy by the RLAS±PI group, but at a cost to an increasing the vertical rate of loading. As a result of this strategy, we observed proximal movement strategies with the use of increased hip and trunk movement to regain balance after the jump landing. Increases in rate of loading have been attributed to overuse injuries in running and jumping sports.

Key words: recurrent lateral ankle sprain, postural control, biomechanics