Dynamic postural control but not mechanical stability differs among those with and without chronic ankle instability

Abstract

The purpose of this investigation was to compare dynamic postural control and mechanical ankle stability among patients with and without chronic ankle instability (CAI) and controls. Seventy-two subjects were divided equally into three groups: uninjured controls, people with previous ankle injury but without CAI, and people with CAI. Subjects completed a single-leg hop-stabilization task, and then had an anterior drawer test and lateral ankle radiograph performed bilaterally. The dynamic postural stability index was calculated from the ground reaction forces of the single-leg hop-stabilization task. Ankle joint stiffness (N/m) was measured with an instrumented arthrometer during the anterior drawer test, and fibula position was assessed from the radiographic image. Patients with previous ankle injuries but without CAI demonstrated higher frontal plane dynamic postural stability scores than both the uninjured control and CAI groups (P<0.01). Patients with and without CAI had significantly higher sagittal plane dynamic postural stability scores (P<0.01) and increased ankle joint stiffness (P=0.045) relative to the control group. The increased frontal plane dynamic postural control may represent a component of a coping mechanism that limits recurrent sprains and the development of CAI. Mechanical stability alterations are speculated to result from the initial ankle trauma.

Discriminating Between Copers and People With Chronic Ankle Instability

“…The data originally were collected to study group differences between uninjured controls, copers, and people with CAI, so most group means and standard deviations used in this investigation have been published. 4,8,14 …”

“…Participants were recruited from the student population at a large public university, and their ages ranged from 18 to 30 years. 4,8,14 They participated in aerobic recreational activity at least 3 times each week for a total of 90 minutes and had a history of at least 1 unilateral lateral ankle sprain that necessitated immobilization or no weight bearing for at least 3 days.…”

“…4,8,14 The primary author (E.A.W.) screened and grouped all participants and conducted data analysis.…”

“…2,3 Some people who have histories of lateral ankle sprain return to high-level activities (ie, jumping, pivoting) without recurrent injury or loss of function through an unidentified mechanism that allows them to function as if uninjured. [4][5][6][7][8] These people are called copers. Understanding the differences between copers and people with CAI will help elucidate the underlying cause of CAI.…”

“…Understanding the differences between copers and people with CAI will help elucidate the underlying cause of CAI. To date, researchers have not identified differences in functional performance scores (eg, hop tests), 4 the number of trials failed while completing a hop test protocol, 4 ankle joint stiffness, 8 fibula position (ie, positional fault), 8 and several kinematic outcomes during various dynamic tasks between copers and people with CAI. 5 However, differences in perceptual (eg, self-assessed questionnaires), 4 mechanical (eg, ligament laxity), 6 and sensorimotor (eg, balance and kinematic) 5,7,8 outcomes have been identified between copers and people with CAI.…”