Using Balance Tests to Discriminate Between Participants With a Recent Index Lateral Ankle Sprain and Healthy Control Participants: A Cross-Sectional Study

Context: The first step to identifying factors that increase the risk of recurrent ankle sprains is to identify impairments after a first sprain and compare performance with individuals who have never sustained a sprain. Few researchers have restricted recruitment to a homogeneous group of patients with first sprains, thereby introducing the potential for confounding. Objective: To identify impairments that differ in participants with a recent index lateral ankle sprain versus participants with no history of ankle sprain. Design: Cross-sectional study. Patients or Other Participants: We recruited a sample of convenience from May 2010 to April 2013 that included 70 volunteers (age = 27.4 +/- 8.3 years, height = 168.7 +/- 9.5 cm, mass = 65.0 +/- 12.5 kg) serving as controls and 30 volunteers (age = 31.1 +/- 13.3 years, height = 168.3 +/- 9.1 cm, mass = 67.3 +/- 13.7 kg) with index ankle sprains. Main Outcome Measure(s): We collected demographic and physical performance variables, including ankle-joint range of motion, balance (time to balance after perturbation, Star Excursion Balance Test, foot lifts during single-legged stance, demi-pointe balance test), proprioception, motor planning, inversion-eversion peak power, and timed stair tests. Discrim-inant analysis was conducted to determine the relationship between explanatory variables and sprain status. Sequential discriminant analysis was performed to identify the most relevant variables that explained the greatest variance. Results: The average time since the sprain was 3.5 +/- 1.5 months. The model, including all variables, correctly predicted a sprain status of 77% (n = 23) of the sprain group and 80% (n = 56) of the control group and explained 40% of the variance between groups (chi(2)(27) = 42.16, P =.03). Backward stepwise discriminant analysis revealed associations between sprain status and only 2 tests: Star Excursion Balance Test in the anterior direction and foot lifts during single-legged stance (chi(2)(27) = 15.2, P = .001). These 2 tests explained 15% of the between-groups variance and correctly predicted group membership of 63% (n = 19) of the sprain group and 69% (n = 48) of the control group. Conclusions: Balance impairments were associated with a recent first ankle sprain, but proprioception, motor control, power, and function were not.