Rigid Ankle-Foot Research Articles

Development of Center of Pressure Guided Wearable Haptic Feedback System to Improve Propulsion With Rigid Ankle Foot Orthosis: A Proof-of-Concept Study in Healthy Individuals

Development of Center of Pressure Guided Wearable Haptic Feedback System to Improve Propulsion With Rigid Ankle Foot Orthosis: A Proof-of-Concept Study in Healthy Individuals

A quantitative analysis of optimum design for rigid ankle foot orthoses: The effect of thickness and reinforcement design on stiffness.

An ankle foot orthosis (AFO) which is prescribed to be rigid should only deform a small amount to achieve its clinical goals. Material thickness and the design of reinforcing features can significantly affect AFO rigidity, but their selection remains based on anecdotal evidence. To quantify the effect of these parameters on AFO stiffness and to set the basis for quantitative guidelines for the design optimisation of rigid AFOs. Experimental and computational study. A polypropylene AFO was produced according to UK standard practice and its stiffness was experimentally measured for 30Nm of dorsiflexion. Its geometry and mechanical characteristics were utilised to create a finite element (FE) model of a typical AFO prescribed to be rigid. Following validation, the model was used to quantify the effect of material thickness and reinforcement design (i.e., reinforcement placement, length) on stiffness. A final set of AFO samples was produced to experimentally confirm key findings. For a specific AFO geometry and loading magnitude, there is a thickness threshold below which the AFO cannot effectively resist flexion and buckles. FE modelling showed that stiffness is maximised when reinforcements are placed at the anterior-most position possible. This key finding was also experimentally confirmed. The stiffness of an AFO reinforced according to standard practice with lateral and medial ribbing was 4.4 ± 0.1 Nm/degree. Instructing the orthotic technician to move the ribbings anteriorly increased stiffness by 22%. Further stiffening is achieved by ensuring the reinforcements extend from the footplate to at least two-thirds of the AFO's total height.

Rigid Ankle Foot Orthosis Deteriorates Mediolateral Balance Control and Vertical Braking during Gait Initiation.

Rigid ankle-foot orthoses (AFO) are commonly used for impeding foot drop during the swing phase of gait. They also reduce pain and improve gait kinematics in patients with weakness or loss of integrity of ankle-foot complex structures due to various pathological conditions. However, this comes at the price of constraining ankle joint mobility, which might affect propulsive force generation and balance control. The present study examined the effects of wearing an AFO on biomechanical variables and electromyographic activity of tibialis anterior (TA) and soleus muscles during gait initiation (GI). Nineteen healthy adults participated in the study. They initiated gait at a self-paced speed with no ankle constraint as well as wearing an AFO on the stance leg, or bilaterally. Constraining the stance leg ankle decreased TA activity ipsilaterally during the anticipatory postural adjustment (APA) of GI, and ipsilateral soleus activity during step execution. In the sagittal plane, the decrease in the stance leg TA activity reduced the backward displacement of the center of pressure (CoP) resulting in a reduction of the forward velocity of the center of mass (CoM) measured at foot contact (FC). In the frontal plane, wearing the AFO reduced the displacement of the CoP in the direction of the swing leg during the APA phase. The mediolateral velocity of the CoM increased during single-stance prompting a larger step width to recover balance. During step execution, the CoM vertical downward velocity is normally reduced in order to lessen the impact of the swing leg with the floor and facilitates the rise of the CoM that occurs during the subsequent double-support phase. The reduction in stance leg soleus activity caused by constraining the ankle weakened the vertical braking of the CoM during step execution. This caused the absolute instantaneous vertical velocity of the CoM at FC to be greater in the constrained conditions with respect to the control condition. From a rehabilitation perspective, passively- or actively-powered assistive AFOs could correct for the reduction in muscle activity and enhance balance control during GI of patients.

The Shank-to-Vertical-Angle as a parameter to evaluate tuning of Ankle-Foot Orthoses

The effectiveness of an Ankle-Foot Orthosis footwear combination (AFO-FC) may be partly dependent on the alignment of the ground reaction force with respect to lower limb joint rotation centers, reflected by joint angles and moments. Adjusting (i.e. tuning) the AFO-FC's properties could affect this alignment, which may be guided by monitoring the Shank-to-Vertical-Angle. This study aimed to investigate whether the Shank-to-Vertical-Angle during walking responds to variations in heel height and footplate stiffness, and if this would reflect changes in joint angles and net moments in healthy adults. Ten subjects walked on an instrumented treadmill and performed six trials while walking with bilateral rigid Ankle-Foot Orthoses. The AFO-FC heel height was increased, aiming to impose a Shank-to-Vertical-Angle of 5°, 11° and 20°, and combined with a flexible or stiff footplate. For each trial, the Shank-to-Vertical-Angle, joint flexion–extension angles and net joint moments of the right leg at midstance were averaged over 25 gait cycles. The Shank-to-Vertical-Angle significantly increased with increasing heel height (p<0.001), resulting in an increase in knee flexion angle and internal knee extensor moment (p<0.001). The stiff footplate reduced the effect of heel height on the internal knee extensor moment (p=0.030), while the internal ankle plantar flexion moment increased (p=0.035). Effects of heel height and footplate stiffness on the hip joint were limited. Our results support the potential to use the Shank-to-Vertical-Angle as a parameter to evaluate AFO-FC tuning, as it is responsive to changes in heel height and reflects concomitant changes in the lower limb angles and moments.

Optimising the effects of rigid ankle foot orthoses on the gait of children with cerebral palsy (CP) – an exploratory trial

Purpose: This exploratory trial investigated the effects of rigid ankle foot orthoses (AFO) with an optimally cast Angle of the Ankle in the AFO (AAAFO) on the gait of children with Cerebral Palsy (CP), and whether tuning of the AFO – Footwear Combination (AFO-FC) further affected gait. Methods: Eight children with CP underwent gait analysis and tuning of their AFO-FCs using a 3-D motion analysis system. Comparisons were carried out for selected gait parameters between three conditions – barefoot, non-tuned AFO-FC and tuned AFO-FC. Results: In comparison to barefoot gait, walking with a non-tuned AFO-FC produced significant (p < 0.05) improvements in several key gait parameters. Compared to the non-tuned AFO-FC, on average a tuned AFO-FC produced a significant reduction in peak knee extension and knee ROM during gait. However, when examined as case studies, it was observed that the type of gait pattern demonstrated while wearing a non-tuned AFO-FC affected the outcomes of tuning. Conclusions: The findings of the current study indicate the potential benefits of using rigid AFO-FC with optimal AAAFO and tuning of AFO-FCs. This study emphasises the need for categorising children with CP based on their gait patterns when investigating the effects of interventions such as AFOs.Implications for RehabilitationRigid ankle foot orthoses (AFO) cast at an optimal angle to accommodate the length of gastrocnemius muscle may positively influence walking in children with Cerebral Palsy (CP).Tuning of the AFO-Footwear Combination (AFO-FC) has potential benefits to the walking of children with CP, depending on their gait abnormalities.When investigating the effects of interventions such as AFOs, it is important to categorise children with CP based on their gait abnormalities.

A case of PKAN treated with botulinum toxin A

A 26-year-old girl had typical clinical presentation of pantothenate kinase associated neurodegeneration (PKAN) and autosomal recessive transmission was evaluated. She had marked contractions of the lower facial muscles and severe contraction of calf muscles, with both feet in a crooked position, more evident on the left side. Since infancy, she walked abnormally and was unstable when standing, due to rapidly progressive hypertonia of lower limbs. She could walk only with double support and using a rigid ankle–foot orthesis in both legs to correct for internal foot rotation. Walking barefoot was impossible. Hyperactivity of the medial calf muscles (tibialis posterior and medial gastrocnemius) was evident upon inspection and EMG recording. In order to reduce the abnormal foot posture and prevent falls, we injected both legs with botulinum toxin A: 200 Dysport ® U in the motor points of the tibialis posterior muscle and 200 Dysport ® U in the medial part of gastrocnemius muscle. She continued to follow a thorough daily rehabilitation to improve balance and postural stability. We observed a gradual reduction of hypertonus and correction of internal foot rotation. The patient gradually achieved stability while standing and could walk independently without orthesis. Her social life improved markedly.

The Effects of Hinged and Rigid Ankle-Foot Orthoses on the Sit-to-Stand Maneuver

The Effects of Hinged and Rigid Ankle-Foot Orthoses on the Sit-to-Stand Maneuver

The Effects of Hinged and Rigid Ankle-Foot Orthoses on the Sit-to-Stand Maneuver

The Effects of Hinged and Rigid Ankle-Foot Orthoses on the Sit-to-Stand Maneuver