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Optimising Orthotic Effectiveness in Ambulant Cerebral Palsy

Original Editor - Ewa Jaraczewska based on the course by Donna Fisher
Top Contributors - Ewa Jaraczewska, Jess Bell and Tarina van der Stockt

Introduction

Ankle-foot orthoses (AFOs) provide external mechanical support at the foot and ankle. They can be beneficial for children with cerebral palsy, helping to maintain range of motion and optimise foot and ankle position.[1] With advances in technology and fabrication methods, the range of AFOs is increasing.[2] There is, however, little evidence to support one AFO design over another, so orthotists tend to choose designs based on their experience, availability, and funding options.[3] [4] This article provides an overview of how orthotists design, fit and troubleshoot custom-made AFOs for ambulant children with cerebral palsy.

To better understand these concepts, you might find it useful to recap the different levels of functioning for ambulant children with cerebral palsy: Gross Motor Function Classification System - Expanded and Revised (GMFCS-ER).

Design Options

Material

The material chosen for an AFO determines its physical characteristics, including its elasticity, resilience, flexibility, durability, hardness, density, and temperature response. There are three categories of materials used in AFOs:[1]

  • accommodative: provide comfort, support and protection; they are placed between the patient and the orthosis
  • shock-absorbing: provide cushioning without warping; often laminated to other materials
  • loading: provide the structure to the orthosis; used to withstand loads and for corrective measures

Currently, the most commonly used materials in AFOs are thermoplastic and thermosetting polymers, metals, leather, fabrics, foamed plastics, and polymer-based composites.[1] Thermoplastic materials are often used when making AFOs for children with cerebral palsy because they are lightweight, durable and have greater aesthetic appeal.[1]

Trimlines

The trimline is the border or shape of the orthosis. The desired function of the AFO determines the choice of trimline, with differences in trimline for rigid, flexible or jointed AFOs.[5][6] In general, the more anterior the trimline, the stiffer the AFO.[5]

Pads

AFO pads are made from foam or other soft, cushioned materials. They provide support for the foot and ankle, reduce pressure, and improve comfort. Pads allow increased forces, providing softer areas for bony prominences.[3]

Straps

AFO straps reduce friction and hold the foot in place. However, straps can make it tricky to fit an AFO into a shoe.[3]

Posting

Posting is adding heel or sole wedges to an AFO. Posting aims to promote an improved gait pattern, balance, and foot/ ankle position.[3]

Decision Tree

AFOs will only benefit a child if they are worn, and they should be prescribed for a specific issue or issues - e.g. to control plantar flexion.[7]

An orthotist will go through the following steps before deciding on an AFO:[3]

  • Step 1: decide if a custom-made or an off-the-shelf orthosis should be used based on the assessment
  • Step 2: cast/measure the AFO
  • Step 3: establish the optimum position of the AFO shell
  • Step 4: decide which forces are needed to maintain the position of the foot/ankle within the AFO
  • Step 5: determine which external forces may influence the hip and the knee

Off-the-shelf AFOs

There is a limited number of off-the-shelf (OTS) orthoses available for the paediatric population. OTS orthoses have benefits and drawbacks. They are generally thinner, more flexible, and lightweight,[3] and are designed for a typically developing foot or simple clinical conditions.[1] While OTS orthoses can be modified and customised for a patient to achieve the best functional outcome, they don't always fit the patient's ankle and foot structure.[1]

OTS orthoses are typically measured from the patient's shoe size, rather than their individual foot or ankle measurements. They are also often made from materials such as carbon fibre or plastic. It can be quite useful to use an off-the-shelf AFO in adolescent individuals with cerebral palsy after a custom AFO has done its job during the growing years.[1]

Designing Custom AFOs

The majority of AFOs for children with cerebral palsy before they reach adolescence are custom-made.[3]

Designing and manufacturing custom AFOs involves several key steps. The process begins with assessing the optimum position for the AFO, taking into account the individual needs and requirements of the patient. Following this assessment, a plaster cast is taken after the assessment is completed, providing a detailed impression of the child's foot. From this cast, a positive model of the child's foot is created.[3]

During the manufacturing process, a rectification process may occur where the orthotist removes some material from the cast to apply specific forces and build up other areas, such as around bony prominences. This is followed by draping with the desired material or colour of choice. AFOs are usually manufactured through thermoplastic vacuum forming, which allows for precise shaping and customisation of the AFO. [3]

Fitting AFOs

When fitting AFOs for ambulant children with cerebral palsy, the orthotist considers a number of factors.

The first is the location of the forces applied. Most AFOs utilise a three-point pressure system, which involves a main force and counterforces, and trimlines are an important factor when considering these forces. Pressure is also a consideration; pressure equals force over area, so the larger the surface area, the lower the pressure.[3]

Another consideration is the child's and/or caregivers' ability to don (put on) and doff (take off) the orthosis. It is important to teach the child or caregiver how to correctly don and doff the orthosis, and the closing mechanism can vary depending on the child's dexterity.[3]

Comfort and wearability are also important, particularly when compliance is reported to be low.[8] The child must find the AFO comfortable to put on and wear, and proper air circulation for comfort should be guaranteed. It is necessary to check for any skin redness during fitting; common areas of pressure include the malleoli and heel area.[3]

The appearance (aesthetics) of the AFO should be considered as well. Children often like to choose the colour, pattern, etc of their AFO. Finally, shoe fitting is important, as footwear is an integral part of the AFO, and children should be able to choose their shoes if possible.[3]

Troubleshooting

To ensure a good fit, there are several areas that need to be carefully checked. One potential issue is too much space within the AFO. This can lead to friction and rubbing between the foot and the device, causing skin breakdown and blisters. Excess space can also make it difficult to fit shoes properly, particularly if there is too much room at the forefoot and toes of the AFO.[3]

The trimlines of the AFO are also important. If trimlines are too short, the foot may push into a valgus position and splay over the edge of the device, rendering it ineffective in correcting the distal forefoot. Conversely, if the trimlines are too long, they can cause strap bridging, which means the foot is more likely to pull out of the AFO and, as a result, will lose the corrected position.[3]

It is essential to ensure that the AFO is donned correctly. If it is applied in a non-corrected position, this can lead to increased pressure on certain areas of the foot.[3] Brace fitting should also be checked with both the knee flexed and extended, as these positions can affect the fit and effectiveness of the AFO.[3]

Resources

References

  1. ↑ 1.0 1.1 1.2 1.3 1.4 1.5 1.6 Nouri A, Wang L, Li Y, Wen C. Materials and Manufacturing for Ankle–Foot Orthoses: A Review. Advanced Engineering Materials 2023; 25(20):2300238.
  2. ↑ Pangestu PA, Harito C, Sitepu E, Herawan SG, Abrori SA, Tobing CCL. 3D-printed ankle foot orthosis (AFO) with optimized material and design for children with cerebral palsy. Designs. 2026; 10(1):1.
  3. ↑ 3.00 3.01 3.02 3.03 3.04 3.05 3.06 3.07 3.08 3.09 3.10 3.11 3.12 3.13 3.14 3.15 3.16 Fisher D. Optimising Orthotic Effectiveness in Ambulant Cerebral Palsy Course. Plus, 2024.
  4. ↑ Eddison N, Mulholland M, Chockalingam N. Do research papers provide enough information on design and material used in ankle foot orthoses for children with cerebral palsy? A systematic review. J Child Orthop. 2017 Aug 1;11(4):263-271.
  5. ↑ 5.0 5.1 Anbuvalanraj A, Karuppudaiyan S, Roy S. Effects of trimline cut in ankle foot orthosis: An experimental and finite element analysis. J Orthop. 2024 May 11;56:63-69.
  6. ↑ Choo YJ, Chang MC. Commonly used types and recent development of ankle-foot orthosis: A narrative review. Healthcare (Basel). 2021 Aug 13;9(8):1046.
  7. ↑ Hudson D, Michalowski H, Miller F. Lower Extremity Orthoses for Children and Youth with Cerebral Palsy. Cerebral Palsy. 2020:2999-3021.
  8. ↑ Oestreich C, Böhm H, Hösl M, Döderlein L, Lewens D, Dussa CU, Oberhoffer-Fritz R. Orthotic bracing to treat equinus in children with spastic cerebral palsy: Recorded compliance and impact of wearing time. Gait Posture. 2025 May;118:75-84.
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