Biomechanical evaluation of a novel fiberglass reinforced polyamide custom ankle-foot orthosis: gait analysis and energy assessment in a population of mild foot-drop patients

Ankle foot orthoses (AFOs) are medical devices used to stabilize the ankle following traumatic injuries, or lesion to the central or peripheral nervous systems leading to foot-drop. This represents the inability to lift the foot during the swing phase of walking, due to neuro-muscular impairments of the ankle dorsiflexor muscles. Mild foot-drop patients may need a comfortable AFO that provides support to the ankle and that can bend seamlessly with the physiological ankle motion in common daily motor tasks. While off-the-shelf AFOs are cost-effective solutions, they may not fully comply with the foot and leg shape and the patient-specific functional requirements. Over the last 20 years, advancements in additive manufacturing technologies have allowed to manufacture custom orthotic devices that better fit the affected anatomical segment. This thesis aimed at evaluating the functional and biomechanical outcome of a novel fiberglass-reinforced polyamide passive-dynamic custom AFO, manufactured via Selective Laser Sintering, in a population of foot-drop patients (n = 10; age = 64.9 ± 11.4 years, BMI = 26.2 ± 2.1 kg/m2). The energy absorbed and released by the custom AFO during the stance phase of walking has been estimated from its experimentally-measured stiffness and motion tracked via a 8-camera motion analysis system. The functional evaluation was assessed via gait analysis in the three conditions: shod (no-AFO), wearing an off-the-shelf AFO (a Codivilla spring) and wearing the custom AFO. Kinematics and kinetics of the hip, knee and ankle joints were estimated via skin-markers attached to relevant bony landmarks according to the IOR-gait kinematic protocol. Both AFOs resulted in decreased sagittal-plane range of motion of the ankle in the swing phase of gait, as well as in reduced plantarflexion angle. Spatiotemporal parameters analysis showed a significant increased stance time (63.7 ± 1.5 vs 63.7 ± 2.1 vs 61.0 ± 2.7 [% stride time]), normalized speed of walking (52.3 ± 12.9 vs 51.8 ± 14.1 vs 49.3 ± 13.9 [% height/s]) and normalized stride length (64.7 ± 11.0 vs 64.2 ± 11.6 vs 63.3 ± 11.3 [% height]) for the custom AFO with respect to the off-the-shelf one and to the shod condition. The energetic evaluation highlighted that the custom AFO releases part of the stored energy at foot-off thus contributing to the propulsive phase. Moreover, patients perceived the custom AFO more comfortable than the Codivilla spring (VAS score: 8.6 ± 1.2 vs 5.3 ± 1.3). This study provides evidence for the beneficial functional outcomes of AFO personalization, especially for mild foot-drop patients not satisfied with standard orthotics.Ankle foot orthoses (AFOs) are medical devices used to stabilize the ankle following traumatic injuries, or lesion to the central or peripheral nervous systems leading to foot-drop. This represents the inability to lift the foot during the swing phase of walking, due to neuro-muscular impairments of the ankle dorsiflexor muscles. Mild foot-drop patients may need a comfortable AFO that provides support to the ankle and that can bend seamlessly with the physiological ankle motion in common daily motor tasks. While off-the-shelf AFOs are cost-effective solutions, they may not fully comply with the foot and leg shape and the patient-specific functional requirements. Over the last 20 years, advancements in additive manufacturing technologies have allowed to manufacture custom orthotic devices that better fit the affected anatomical segment. This thesis aimed at evaluating the functional and biomechanical outcome of a novel fiberglass-reinforced polyamide passive-dynamic custom AFO, manufactured via Selective Laser Sintering, in a population of foot-drop patients (n = 10; age = 64.9 ± 11.4 years, BMI = 26.2 ± 2.1 kg/m2). The energy absorbed and released by the custom AFO during the stance phase of walking has been estimated from its experimentally-measured stiffness and motion tracked via a 8-camera motion analysis system. The functional evaluation was assessed via gait analysis in the three conditions: shod (no-AFO), wearing an off-the-shelf AFO (a Codivilla spring) and wearing the custom AFO. Kinematics and kinetics of the hip, knee and ankle joints were estimated via skin-markers attached to relevant bony landmarks according to the IOR-gait kinematic protocol. Both AFOs resulted in decreased sagittal-plane range of motion of the ankle in the swing phase of gait, as well as in reduced plantarflexion angle. Spatiotemporal parameters analysis showed a significant increased stance time (63.7 ± 1.5 vs 63.7 ± 2.1 vs 61.0 ± 2.7 [% stride time]), normalized speed of walking (52.3 ± 12.9 vs 51.8 ± 14.1 vs 49.3 ± 13.9 [% height/s]) and normalized stride length (64.7 ± 11.0 vs 64.2 ± 11.6 vs 63.3 ± 11.3 [% height]) for the custom AFO with respect to the off-the-shelf one and to the shod condition. The energetic evaluation highlighted that the custom AFO releases part of the stored energy at foot-off thus contributing to the propulsive phase. Moreover, patients perceived the custom AFO more comfortable than the Codivilla spring (VAS score: 8.6 ± 1.2 vs 5.3 ± 1.3). This study provides evidence for the beneficial functional outcomes of AFO personalization, especially for mild foot-drop patients not satisfied with standard orthotics

Biomechanical risk factors and reduced bone health in lower limb amputees

Bone constantly adapts to its surroundings through the formation and resorption of material, controlled by bone modelling and remodelling. Strains produced by mechanical loading are one factor that drive these processes and thus determine bone health. Lower limb amputees (LLA) adopt an asymmetrical movement pattern to compensate for the loss of a limb, resulting in a change in mechanical loading and subsequently a degradation in bone health. The aetiology of the majority of amputations is vascular diseases, which affect bone health. Therefore, it is not clear whether the asymmetrical loading, or comorbidities cause the degradation in bone health in LLA. Finite element models (FEM) are used to generate strain plots and predict the bone's response to mechanical loading. To understand the relationship between the degradation in bone health and asymmetrical loads in LLAs the asymmetrical loads can be applied to a healthy bone using FEMs, or simulated within a healthy population using restrictive devices. Therefore, the overall aim was to investigate the relationship between asymmetrical loading, as observed in LLA’s, and bone health, through the use of semi-subject specific FEMs and restrictive lower limb devices. Study one established a novel image processing method to convert peripheral quantative computed tomography (pQCT) scan images into binary and segment the tibia. The outer perimeter of the tibia was identified and sectioned to produce landmarks. The outer geometry landmarks were used to morph a base FEM, constructed from open source scan images to create semi-subject tibia FEM. Study two applied subject-specific joint reaction and muscle forces to the semi-subject tibia FEM. The strain plots output from Study two were validated against longitudinal geometrical changes from Study three. Study three, used 3D motion capture, pQCT and dual energy x-ray absorptiometry (DXA) to investigate gait and tibial geometry within a lower limb amputee and able-bodied population across twelve months. The coefficient of variation (CV) for able bodied subjects was less than 10% for ground reaction force (GRF) in level walking and less than 4% for bone total area. Study four, used a rigid foot orthosis and a trans-femoral prosthesis, to restrict able-bodied gait. Results showed participants walked significantly slower (p<0.01) in the restricted conditions, with a longer non-restricted step length (p<0.001). The loading rate and maximum GRF were higher in the non-restricted limb (p<0.05). Larger knee adductor moments were shown in the un-restricted leg in the trans-tibial condition (p<0.05). This thesis presents a novel method of constructing semi-subject specific FEMs from pQCT scans. This can be used to further investigate the link between asymmetrical loading and bone health in LLA's and other populations with asymmetrical gait. The use of restrictive devices allow investigation into LLA's specifically, without the interference of prosthetic variability, or comorbidities

Tibiofemoral contact areas and contact forces in healthy and osteoarthritic subjects

Knee osteoarthritis (OA) is a common type of musculoskeletal disability, particularly among the elderly population. Excessive contact forces on the joint, or on specific parts of it (e.g. medial compartment), or shifting the contact forces to the regions that are not adapted to loading are the mechanical factors which can trigger OA. Therefore, it is crucial to understand the differences of these mechanical parameters in OA subjects with respect to the healthy ones. The aim of this study was to the compare the tibiofemoral contact point locations and the contact forces in OA and healthy subjects and examine if the contact point locations influence the contact force sharing in both groups. The tibiofemoral contact point locations in 10 healthy and 9 osteoarthritic (OA) subjects during a weight-bearing squat was measured using stand-alone biplane X-ray images. A manual multiple view 3D reconstruction/registration method was used to reconstruct the bones in different squat postures from the biplane radiographs and a weighted center of bone-to-bone proximity was applied to estimate the contact point locations. Results showed that the contact point locations of the OA subjects on the medial and lateral compartments were shifted medially compared to the healthy group. In both groups, contact points showed a posterior excursion on the medial compartment and posterior and lateral excursions on the lateral compartment, where the excursion on the lateral compartment was smaller in OA subjects. To estimate the tibiofemoral contact forces, a custom musculoskeletal model of the lower limb with the integration of personalized contact points was provided to estimate contact forces at subject-specific contact points during gait. The tibiofemoral joint model was reformulated so that the constraints of the joint were formed by the superimposition of the personalized tibial and femoral contact points. The suggested constraints are adaptable to the contact points derived from the classical joint models or those experimentally measured from the 3D imaging techniques. The estimated contact forces estimated using the personalized contact points were compared to those estimated from the classical knee joint models in 10 healthy subjects. Results showed that the impact of personalization of contact points on the contact forces is very variable among the subjects and the shifts of the contact points alone cannot predict the distribution of contact forces in the medial and lateral compartments. To evaluate the contribution of contact point locations to the contact force distribution the musculoskeletal model of the lower limb with the personalized contact point trajectories were used to estimate the medial and lateral contact forces of 10 healthy and 12 OA subjects. The contact forces in healthy subjects were slightly higher compared to the OA subjects. However, no statistically significant difference was noted in the peaks of medial, lateral or total contact forces. The regression analysis results showed that the knee adduction moment and knee flexion moment were the main contributors to the medial-to-total contact force ratio (MR) in both groups. From the components of the contact point location, the medial contact point location in medial/lateral direction had a significant contribution to the MR in OA subjects. This study showed that the mechanism of load distribution was different in OA joints where contrary to the healthy ones the contact point location was a significant contributor to MR. In addition, the knee flexion moment had a higher contribution to MR than the knee adduction moment whereas in healthy subjects the knee adduction moment was the most significant contributor to the MR

Musculoskeletal modelling to analyse and treat anterior cruciate ligament deficiency

Anterior cruciate ligament (ACL) deficiency results in knee instability that includes an increase in internal tibial rotation and anterior tibial translation (ATT) as ACL is the primary restraint to anterior shear and internal rotation. Clinically, ACL deficient (ACLD) patients undergo surgery or/and rehabilitation programmes depending on their ability to cope or otherwise. However, the ACL reconstructed (ACLR) knees may still have residual instability in ATT and tibial internal rotation. Functional electrical stimulation (FES) has been used in conventional physiotherapy for ACL deficiency, including strengthening the muscles around the knee. The rehabilitation treatment focuses on strengthening the quadriceps muscle because it gets weakened after ACL injury or ACL reconstruction. However, stimulating the hamstrings, especially the biceps femoris long head (BFLH) with its insertion on the fibular head is a candidate to reduce the knee instability of ACLD and ACLR by applying a posterior pull and external rotation to the tibia. This thesis proposes that knee instability in ACLD subjects can be reduced by stimulating the BFLH muscle with FES. Here, a musculoskeletal modelling approach was used to simulate the function of FES. A new optimisation method was developed which allowed the inclusion of FES. There are three main studies present in this thesis. First, a pilot study was conducted in which healthy control subjects walked with and without FES of BFLH. It was found that selective activation of the BFLH can reduce the anterior tibial shear and tibial internal rotation torque at the knee in healthy subjects. Second, a validation study for the algorithm used in the musculoskeletal model was conducted in which the effect of FES stimulation of the BFLH on gluteus maximus activations was tested using electromyography (EMG). This study concluded that there were statistical correlations between peak and impulse of gluteus maximus activation between FES activation level and muscle activity of gluteus maximus as quantified by both EMG and the musculoskeletal model. In the final study, the validated model was used to compare the internal rotation torque, anterior shear force, speed and gluteus medius and gluteus maximus muscle activation between control, ACLD and ACLR groups during stance phase with and without FES stimulated on BFLH. This study found that the activation of BFLH with FES during stance phase was able to reduce the knee instability of the patient groups and triggered the compensatory mechanism for each patient group to react differently. Therefore, besides quadriceps, the rehabilitation treatment should focus on appropriate timed activation of the BFLH to improve the quality of life of patients.Open Acces

Musculoskeletal Models in a Clinical Perspective

This book includes a selection of papers showing the potential of the dynamic modelling approach to treat problems related to the musculoskeletal system. The state-of-the-art is presented in a review article and in a perspective paper, and several examples of application in different clinical problems are provided

Prescription of Ankle-Foot Orthoses for Children with Cerebral Palsy

Purpose: Ankle foot orthoses (AFOs) are frequently prescribed to address gait impairments for children with cerebral palsy (CP). Successful treatment with AFOs depends on optimal prescription, matching the design of the brace to the individual child’s physical impairments; however, research evidence does not exist to help health care professionals decide on the best AFO design to meet each child’s needs. Therefore, this thesis explored current AFO prescription practices, and aimed to improve evidence to assist clinicians in making prescription decisions for children with CP. Methods and Results: To examine the experiences and perspectives of clinicians on AFO prescription for children with CP, we conducted focus groups and semi-structured interviews with 32 clinicians who were involved with AFO prescription for children with CP in five Canadian rehabilitation facilities. Using Interpretive Description as a framework for analysis, we identified three categories from the data: 1) What is made, 2) How it is used, and 3) Factors that support or challenge outcomes. Throughout the interviews, the theme of prescription as a collaborative, iterative, and individualized process emerged. To explore evaluation and clinical decision-making practices of physical therapists for AFO prescription and follow-up, we invited Canadian physical therapists (PTs) working with children who have CP to complete an online survey. Sixty completed responses were received. Three researchers conducted a conventional content analysis to examine the open-ended responses, and descriptive statistics were used to summarize the closed-ended responses. Three themes were identified: 1) Focus on impairment level measures, 2) Inconsistent practices between PTs, and 3) Lack of confidence/knowledge about casting positions and AFO types. To investigate the effects of individualizing the angle of the ankle in the AFO on walking mechanics and function, gait biomechanics were studied in ten children with CP. Fifteen typically-developing children provided normative data. Using three-dimensional gait analysis, kinematics and kinetics were compared between the child’s usual AFO(s) and AFOs that were fabricated with an ankle angle that was individualized for each child. Net responses to the individualized ankle angle were positive for 60% of limbs, negative for 40%. The greatest benefits were observed at the knee, suggesting that this may be a beneficial approach to orthotic intervention for some children with CP. Conclusions: There is limited understanding of how AFOs are prescribed for children with CP in Canada. This thesis highlights the importance of multidisciplinary collaboration, objective evaluation, and individualized clinical problem-solving to facilitate the evolution of the AFO prescription from a medical directive to an orthotic device that optimally benefits the child. This is the first step toward the development of guidelines to help clinicians improve AFO prescription for children with CP

The kinematic effects of three quarter and full length foot orthoses on anterior knee pain sufferers when walking and descending stairs

Background: Patellofemoral pain is a common disorder whose aetiology is complex often being described as multifactorial, increased load of the patellofemoral joint is often attributed to foot function. Foot orthoses are commonly prescribed for this condition; however the mechanisms by which they work are poorly understood. Previous studies using single segment foot models have hypothesised that it may be control of the midfoot which hold the key to understanding orthotic control. Over the last decade biomechanical analyses has advanced so it has become possible to divide the foot into segments, however no previous studies have investigated the use of orthoses on different segments of the foot when shod. The overall aim of this study was to investigate the differences seen in the kinematics and kinetics of the lower limb between a patellofemoral pain group and a group of normals when using a standardised orthosis prescription during walking and descending a step. Method: Initially fifteen healthy subjects had foot orthoses moulded to their feet, they were asked to walk at a self-selected pace and complete a 20cm step down; comparisons were made between sandals and shoes, plus two different orthoses. Kinematic and kinetic data were recorded using 10 Oqus cameras and 4 AMTI force platforms. The shoe data from the 15 healthy subjects was re-analysed and used as a control group to compare against 15 subjects diagnosed with patellofemoral pain. The foot was modelled using the calibrated anatomical systems technique (CAST) fixing the marker set directly on the feet and shoes of normal subjects which permitted comparisons of excursions between the shoes and sandals and the effects of the orthoses. Results 1: Similar changes in the pattern of movement were seen between the shoe and the sandals conditions with and without the orthoses; the shoes reduced the excursions recorded except the transverse plane of the rearfoot. At the knee maximum extension was increased and maximum flexion at toe off was reduced by the orthoses. Initial Conclusions: Expectedly the shoes reduced the range of motion over the sandal condition in most planes; however the similar effects seen with the orthoses in both types of footwear suggesting it was acceptable to use shoes in the later study. Results 2: Significant differences were seen between the healthy subjects and the patellofemoral pain subjects at the foot and the knee. Both orthoses produced statistically significant results at the foot. In addition there was a significant reduction in the knee coronal plane moment range during the forward continuum phase of step down; this was attributed to a change in the ground reaction force as there were no changes reported in the kinematics of the knee. Conclusions: The method of placement of the markers was able to detect small changes within the foot segments. This study identified potentially important differences between the patellofemoral pain subjects and the normals in both the knee and foot segments. However due to the lack of pain during the walking and step down trials it could not be determined if the changes were due to pain avoidance mechanisms or if they were causative factors. Many of the changes produced by the orthoses tended to be local to the foot, except for the knee coronal plane moment range during the forward continuum phase of step down. To the authors knowledge this work is unique in its investigation of the motion of foot segments while shod and confirmed the clinically held belief it is essential to consider footwear when prescribing orthoses to patients. The use of foot mechanics could be of interest to further research and may help to define sub-populations within this condition