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Biomechanics assisted evaluation of ligament behaviour during functional movements - insights for ankle sprain prevention, treatment and rehabilitation

Book - Dissertation

Ankle sprain is one of the most common musculoskeletal injuries, often resulting in lateral ankle ligament tears or ruptures. Thirty to fifty percent of the patients develop chronic ankle instability (CAI) after a first ankle sprain, including persistent complaints of pain, swelling and/or the feeling of giving way in combination with recurrent sprains. CAI may be caused by mechanical (MAI) or functional ankle instability (FAI) or a combination of both. MAI is the result of factors altering the mechanics of one or more joints of the foot-ankle complex (e.g. ligament injury) and FAI is caused by insufficient proprioception, neuromuscular control, postural control or strength. The anterior drawer and talar tilt test are frequently used to evaluate MAI based on the amount of anterior displacement and lateral tilt of the talus. However, there is no method to analyse the isolated effect of ligament injuries on ankle and subtalar joint kinematics in vivo. For the evaluation of FAI, clinical studies often use the AOFAS questionnaire to evaluate pain, feeling of instability and hindfoot function during gait. In research applications, proprioception and muscle strength have been quantified using different methods. In addition, the effect of CAI on foot-ankle function has been analysed during different movements in terms of joint kinematics, joint kinetics and/or muscle activity using integrated 3D motion analysis. In contrast, studies on the lateral ligament behaviour, in terms of ligament strain or forces, are still limited to the evaluation of ligament strains during analytical ankle positions. As the lateral ligaments play a major role in ankle stability, there is a need to better document the role of the different ligaments on the control of foot-ankle kinematics and of the effect of ligament injuries on foot-ankle function in general during dynamic movements. Therefore, the aim of this thesis was to develop and evaluate in vivo methods to objectively evaluate the biomechanical consequences of mechanical and functional ankle instability and their effect on foot-ankle function during different movements representative for daily life and sport activities in healthy participants and in patients suffering from CAI. In order to achieve this overall goal, the work was divided in three main objectives: (1) In vitro evaluation of the dynamic role of the individual lateral ligaments in controlling foot-ankle kinematics during simulated gait (study 1), (2) method development for dynamic evaluation of the biomechanical consequences of mechanical and functional ankle instability in vivo (study 2, 3 and 4) and (3) in vivo evaluation of mechanical and functional ankle instability and their effect on dynamic ligament behaviour, musculoskeletal function and joint loading during dynamic movements in CAI patients (study 5). Firstly, the individual role of the lateral ligaments in controlling foot-ankle kinematics was evaluated during simulated gait in vitro (study 1). Kinematics of the ankle, subtalar, tibiocalcaneal, talonavicular and calcaneocuboid joint were compared between five different conditions measured in vitro during a simulation of the stance phase of gait, imposed by the gait-simulator: intact foot, isolated anterior talofibular ligament (ATFL) resection, combined ATFL and calcaneofibular ligament (CFL) resection, combined ATFL-CFL suture tape reconstruction and isolated ATFL suture tape reconstruction. The ligament resections mainly changed the kinematics in the hindfoot joints in all movement directions (inversion/eversion, internal/external rotation and plantar/dorsiflexion), but additional changes in kinematics in the midfoot joints were also observed. In general, the combined ATFL-CFL reconstruction restored motion in the hind- and midfoot joints (mainly in inversion/eversion) immediately after surgery more than the isolated ATFL reconstruction. Despite this positive effect, CFL reconstruction is not always considered, given its location underneath the peroneal tendons and close to the sural nerve. Overall, this study provided information on the unique contribution of the ATFL and CFL to hind- and midfoot kinematics control during simulated gait in vitro. Secondly, the use of 4D CT scanning in combination with a foot manipulator, to evaluate in vivo the isolated effect of lateral ligament injury on foot-ankle kinematics during simulated gait, was validated (study 2). Thereafter, the use of this method to detect clinically relevant changes in kinematics was evaluated in CAI patients. The participant's foot was attached to the foot bed of the foot manipulator and it imposed a combined inversion/eversion and plantar/dorsiflexion movement to the foot during which the foot-ankle kinematics were acquired using 4D CT scanning. First, a cadaveric experiment was performed to validate the sensitivity of hind- and midfoot joint kinematics to different loading magnitudes, showing that different loading magnitudes did not affect the dynamically induced kinematics. Then, the representativeness of the simulated stance phase to normal weight-bearing gait was validated by comparing the kinematics from the 4D CT measurement to the kinematics measured during in vivo weight-bearing walking with bone pins. These results confirmed that the foot manipulator allowed simulating a gait-like movement. Finally, changes in hind- and midfoot joint kinematics in CAI patients were documented, showing the isolated effect of ligament ruptures in vivo. An ATFL rupture resulted in higher ankle inversion and external rotation and subtalar internal rotation. In conclusion, this study resulted in a validated set-up to evaluate individual foot bone kinematics during simulated gait in vivo, which can be used to evaluate the unique contribution of ligaments to the control of foot-ankle kinematics in vivo. Thirdly, the performance of a new foot-ankle musculoskeletal model was evaluated taking advantage of the combination of musculoskeletal modelling and 3D motion capture as a window of opportunity to evaluate ligament behaviour during dynamic movements. More specific, the effect of integrating the lateral ankle ligaments and incorporating the subtalar degree of freedom, next to the ankle joint in a detailed foot-ankle musculoskeletal model on the calculated muscle force distribution, ankle joint loading and validity of the calculated muscle activity was evaluated (study 3). First, lateral ligament forces were calculated during the different movements and these were in line with ligament function reported in literature. In addition, increasing the degree of freedom and integrating the lateral ankle ligaments resulted in higher peak ankle joint contact force given a decreased contribution of the m. peroneus longus, m. soleus, m. gastrocnemius lateralis and m. gastrocnemius medialis, but increased contribution of the m. tibialis posterior, also in line with the lateral ankle ligament function. Finally, the validity of the calculated muscle activity was evaluated by comparing to measured muscle activity using electromyography, indicating small, but inconsistent differences (both improved and deteriorated estimations of lower leg muscle activity) with increasing musculoskeletal model complexity during most movements. Future studies can use the 2DOF MSM with ligaments to analyse lateral ligament behaviour in chronic ankle instability patients where a second degree of freedom is crucial to accurately assess calcaneofibular ligament strain consequent to ankle and subtalar joint movement. Fourthly, peak lateral ligament strain and a new ligament loading index were calculated during movements representative of daily life and sport activities (more specific: walking, running, single leg stance with and without visual feedback, stair descending and ascending, anterior and medio-lateral single leg hops, forward and sideward lunges and vertical drop jumps) in healthy volunteers (study 4) to explore to what extent the lateral ligaments were loaded during these movements. Peak lateral ligament strain and a ligament loading index were calculated using the musculoskeletal modelling workflow in combination with 3D motion capture data of the movements. The ligament loading index combines the strain magnitude and duration and magnitude of the combined ankle and subtalar joint moment in one metric to not only account for risky ankle joint position, but also for the external loading as literature showed an ankle sprain is often a result from the combination of both. All three ligaments had the highest ligament loading index during vertical drop jumps, medio-lateral single leg hops and running. Additionally, the ATFL loading was high during stair descending, the CFL loading during single leg stance without visual feedback and the PTFL loading during anterior single leg hops. Peak lateral ligament strains were the highest during vertical drop jumps, sideward lunges, stair descending and running. Based on these results, activities were classified according to the ligament loading index and peak strain, thereby providing objective data for ankle sprain prevention. Finally, MAI, FAI and the effect of CAI on foot-ankle function was evaluated in a cohort of CAI patients and compared to healthy volunteers (study 5) using the methods developed in study 2, 3 and 4. Ligament behaviour and ankle joint loading were evaluated during a variety of movements as biomarkers of ankle sprain risk and risk for ankle osteoarthritis development. The CAI patients showed lower ligament and ankle joint loading during explosive movements, mainly caused by the combination of lower ligament strains and lower ankle plantarflexion and subtalar inversion moments. No differences in ligament and ankle joint loading were observed for the other movements. Furthermore, no task dependent kinematic changes were found in the CAI patients during these explosive movements, but overall, they had higher trunk bending towards the injured leg, higher hip external rotation and higher hip abduction. In addition, a higher hip internal rotation moment and higher ankle plantarflexion moment were observed. Although some overall changes could be observed, also large differences between patients were found for MAI, FAI and foot-ankle function during the dynamic movements. Nevertheless, these interpatient differences resulted in lower ligament and ankle joint loading during explosive movements which reduces the risk for recurrent ankle sprains during these movements. Overall, this thesis contributed to an objective evaluation of the dynamic ligament behaviour in vivo during dynamic movements. The unique contribution of the lateral ligaments to the control of foot-ankle kinematics was evaluated in vitro and in vivo and the ligament behaviour and ankle joint loading was analysed during dynamic movements in vivo. To do so, two new set-ups were validated (4D CT scanning in combination with foot manipulator and the extended foot-ankle musculoskeletal model with lateral ligaments), to provide unique insights for the (pre- and post-operative) evaluation and treatment optimisation of hindfoot pathologies in vivo.
Publication year:2020