Biomechanical study of rigid ankle-foot orthoses in the treatment of stroke patients

Error on title page, date of award is 2021.Rigid Ankle-Foot Orthoses (AFOs) are commonly prescribed for stroke patients who exhibit equinovarus deformity as an orthotic intervention. The main purpose of prescribing a rigid AFO is to provide appropriate control of unwanted ankle and foot motions in any plane. To achieve the optimal effects of the AFO, appropriate stiffness and alignment optimisation (tuning) should be considered. The AFO provides moments (referred to as the orthotic moments) to control ankle motion. Orthotic moments are different from the moments generated by ground reaction forces, the later are known as total ankle moments. Reviewing the literature showed limited research in this area. The aims of this study are to investigate the biomechanical effects of using rigid AFO (before and after tuning) and to investigate the orthotic moment during walking in stroke patients. Gait data were collected from six stroke participants (2 females, 4 males) and six healthy participants (3 females, 3 males) using a Motekforce Link dual belt instrumented treadmill and a Vicon 3-dimensional motion analysis system. Each participant was fitted with a custom made rigid AFO instrumented using four strain gauges. Walking at a self-selected speed was investigated while wearing: (1) Standard shoes only (2) Rigid AFO with standard shoes (3) Rigid Tuned-AFO with standard shoes. Lower limb temporal-spatial, kinetic and kinematic parameters, and electromyographic activity (Delsys TrignoTM) of the knee muscles were compared among the test conditions. The orthotic moments were also quantified using the strain gauges data combined with gait analysis. Repeated measures ANOVA and Friedman’s ANOVA were used for statistical analysis. The rigid AFO showed immediate improvement in the temporal-spatial parameters and the kinematics and the kinetics of post stroke gait. Greater improvement in knee kinematics and kinetics was achieved when tuning the rigid AFO. The rigid AFO (before and after tuning) increased quadriceps muscle activity and reduced hamstring muscle activity compared to walking with standard shoes only. Tuning a rigid AFO further increased quadriceps muscle activity and reduced hamstring muscle activity compared to AFO before tuning. Strain gauges data combined with gait analysis can be used in evaluating the orthotic moment around the ankle in sagittal and frontal planes. Tuning a rigid AFO had no clear changes in the orthotic moment, and it did not alter the anatomical moments at the ankle joint in sagittal and at the subtalar joint in frontal plane.Rigid Ankle-Foot Orthoses (AFOs) are commonly prescribed for stroke patients who exhibit equinovarus deformity as an orthotic intervention. The main purpose of prescribing a rigid AFO is to provide appropriate control of unwanted ankle and foot motions in any plane. To achieve the optimal effects of the AFO, appropriate stiffness and alignment optimisation (tuning) should be considered. The AFO provides moments (referred to as the orthotic moments) to control ankle motion. Orthotic moments are different from the moments generated by ground reaction forces, the later are known as total ankle moments. Reviewing the literature showed limited research in this area. The aims of this study are to investigate the biomechanical effects of using rigid AFO (before and after tuning) and to investigate the orthotic moment during walking in stroke patients. Gait data were collected from six stroke participants (2 females, 4 males) and six healthy participants (3 females, 3 males) using a Motekforce Link dual belt instrumented treadmill and a Vicon 3-dimensional motion analysis system. Each participant was fitted with a custom made rigid AFO instrumented using four strain gauges. Walking at a self-selected speed was investigated while wearing: (1) Standard shoes only (2) Rigid AFO with standard shoes (3) Rigid Tuned-AFO with standard shoes. Lower limb temporal-spatial, kinetic and kinematic parameters, and electromyographic activity (Delsys TrignoTM) of the knee muscles were compared among the test conditions. The orthotic moments were also quantified using the strain gauges data combined with gait analysis. Repeated measures ANOVA and Friedman’s ANOVA were used for statistical analysis. The rigid AFO showed immediate improvement in the temporal-spatial parameters and the kinematics and the kinetics of post stroke gait. Greater improvement in knee kinematics and kinetics was achieved when tuning the rigid AFO. The rigid AFO (before and after tuning) increased quadriceps muscle activity and reduced hamstring muscle activity compared to walking with standard shoes only. Tuning a rigid AFO further increased quadriceps muscle activity and reduced hamstring muscle activity compared to AFO before tuning. Strain gauges data combined with gait analysis can be used in evaluating the orthotic moment around the ankle in sagittal and frontal planes. Tuning a rigid AFO had no clear changes in the orthotic moment, and it did not alter the anatomical moments at the ankle joint in sagittal and at the subtalar joint in frontal plane