Structural characteristics and functional consequences of lateral ankle sprains
Ankles injuries account for 8% of health care consultations and ankle sprainsconstitute about 85% of all ankle injuries. Lateral ankle sprain is a type of injury that affectsboth the general and the sporting population. Lateral ankle sprain has a high rate ofrecurrence which can often lead to individual developing chronic ankle instability. Thischronicity contributes to continue deficits of sensorimotor and constrained functioning)which could have a decrease effect on the health-related quality of life, the level of physicalactivity, and absence from training or competition for athletes, thus create a substantial globalhealthcare burden. With such negative consequences and related financial burden associatedwith LAS and CAI enhanced effort to understand structure and function differences betweenthose that develop CAI and those that do not following an initial acute LAS is needed. Understanding the relationships between the integrity of the ankle structures pre andpost sprain, and functional ability of the ankle is important to inform our understanding of thelong-term effects of sprains and consider better targeting of interventions. This thesis aims tostudy the structural characterisation and functional consequences of lateral ankle sprain.Three studies were undertaken. The first study used ultrasound to characterise and compare selected ankle structuresbetween healthy (n=48), coper (n=22) and chronic ankle instability (n=32) groups.Participants with prior injury had significantly longer anterior talofibular ligament when theligament was under tension (by 6% when compared CAI to healthy participants), and thickeranterior talofibular ligament and calcaneofibular ligament compared to healthy participants(by 54.21% and 8.3% respectively when compared CAI to healthy participants). These grossstructural differences are evidence of residual structural damage. However, they do notindicate whether the quality and nature of the ligament tissue is similarly affected. In study 2 image analysis techniques were used to provide a quantitative measure ofthe echogenicity of the anterior talofibular ligament by computer-aided greyscale analysis.Echogenicity was used as an indicator of ligament quality. The result showed that the echointensity of anterior taloibular ligament was lowest intensity in chronic ankle instability (40% and 18.8% lower than the intensity of healthy and coper respectively) followed by copersand healthy respectively. The echogenicity of the anterior talofibular ligament in copers wassignificantly different from chronic ankle instability and from healthy participants.Characterisation of these further structural changes reveals the extent of residual tissue damage. However, it does not provide any insight into any functional consequences of thesechanges. In a third study, the dynamic balance was evaluated in healthy (n=28), coper (n=18)and chronic ankle instability (n=22) ankles during the star excursion balance tests, usingforce plate and ankle kinematic analysis. This sought to investigate the functionalconsequences of the structural changes identified in studies 1 and 2. Participants with chronicankle instability demonstrated poorer dynamic balance and altered ankle kinematicscompared to healthy and coper participants, and copers also had altered kinematics. Therewas a significant negative relationship between the thickness of the ligament and the distanceachieved when reaching in the anterolateral direction of the balance test (r = -0.53,p<0.001and r = -0.40, p<0.001 respectively). Characterisation of normal and injuredligaments appears to differentiate post sprain functionally. Balance tests reveal functionalbalance deficits and altered kinematic strategies that relate to the lateral ankle structurespreviously injured. Lateral ankle sprain causes damage to lateral ankle ligaments and impaired sensorypathway to the CNS. Then the initial consequences lead to structural alteration (increased thelaxity of ATFL and increased the thickness of ATFL and CFL). Joint loading could be alteredand changes in normal movement patters occur as demonstrated in decrease reach distanceand alter the kinematics of the ankle joint in injured participants compared to healthyparticipants. This is the first study that combined both structural changes and functionalconsequences of lateral ankle sprain and investigate any relationship between them to providean overall understanding of how these two factors are related..
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