An in-depth examination of strength in subjects with self-reported chronic ankle instability and mechanical laxity
Date
2016
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Publisher
University of Delaware
Abstract
Context: Lateral ankle sprains commonly occur within the athletic population. However, athletes who sustain one ankle sprain have a higher risk of recurrent episodes that frequently lead to chronic ankle instability (CAI). CAI is a multifactorial diagnosis that includes mechanical and functional instability components. Mechanical instability generally includes ligamentous laxity, whereas functional instability includes neuromuscular aspects and strength. However, the impact of laxity and CAI on ankle strength remains un. Objective: To compare ankle strength (PF, DF, INV and EV) measurements in athletes who have mechanical laxity and who present with reported chronic ankle instability after a history of unilateral ankle sprains. Design: Retrospective study. Participants: 165 participants including 97 males and 68 females (height = 178.01cm, weight = 78.7 kg, age = 18.5 years). Interventions: An injury history questionnaire and Cumberland Ankle Instability Tool (CAIT) were administered to determine the number of previous ankle sprains and the presence of self-reported CAI. Laxity of the ankle joint was determined using a portable ankle arthrometer measuring anterior displacement in millimeters and inversion rotation in degrees. Strength was measured using a Kin Com isokinetic dynamometer and peak torque for the four different ankle motions were recorded. Main Outcome Measures: The independent variable was group status as determined by either (1) ankle instability (CAIT scores) and (2) ankle laxity (arthrometry measurement). The dependent variables are peak torque strength measures, concentric (CON) and eccentric (ECC) in two velocities (30°/sec & 120 °/sec), in all ankle motions. Results: 24 subjects (14.54%) had both anterior and INV/EV laxity and 74 of the 165 participants (44.84%) had self-reported CAI in their injured ankle. The laxity group presented with less PF CON strength at 30°/sec (t=-2.567, p=.011) and EV CON strength at 120 °/sec (t=-2.137, p=.034) than those who did not have laxity. A trend toward significance was seen for ECC (t=-1.905, p=.059) and CON PF at 120 °/sec (t=-1.852, p=.066). No significance was found between those with or without CAI and their strength measurements. Conclusion: Plantar flexion and eversion strength was significantly less in those without laxity compared to their contralateral, uninjured ankle, exhibiting a need for specific rehabilitation of the specific muscle groups. Even though no significant differences were found with CAI, significance was found with gender and right versus left ankle, exposing that our understanding of CAI as a diagnosis and its relationship with strength is not fully understood.