Ankle & foot splints or orthoses (AFOs)
Ankle and foot orthoses (AFOs), or splints, are external devices fitted to the body, which are used to:
- Improve or prevent a physical deformity
- Stabilise a joint or joints
- Reduce pain
- Improve mobility or performance
- Reduce the risk of tripping over
- Reduce the risk of injury
AFOs have been used for many years to help manage the gait (walking pattern) of children with hemiplegia. They are used to reduce unwanted and uncontrolled movements associated with muscle imbalances, weakness or increased tone (tightness) in the lower leg and the foot and ankle.
Walking and posture problems in children with hemiplegia
Abnormal movement in children with hemiplegia often means a tip-toe walking pattern (equinus or plantarflexed gait) with the added complication of the ankle becoming twisted outwards (varus ankle) or collapsing inwards (valgus ankle).
Ankle dorsiflexion is the movement of the foot at the ankle joint in an upward direction. Dorsiflexion allows the foot to move in various ways without overstressing other joints. Hemiplegia can affect the ankle's ability to dorsiflex (resulting in an equinus foot posture), and this impedes walking. Without dorsiflexion, gait tends to be jerky and stick-like, as it is difficult for the body and leg to pass over the affected foot and ankle. As a result the energy needed to walk increases. The ankle dorsiflexes in many other daily activities, such as standing from sitting, sitting from standing, crouching, going up and down stairs, walking up hill and walking backwards.
The adoption of a toe-walking gait leads to secondary problems:
- The knee joint tends to snap backwards further than it would normally (hyperextension or back kneeing).
- Hyperextension of the knee in turn has a harmful effect on hip position, pelvic stability and symmetry. This can affect the child's balance and general posture.
- The arm on the affected side will also react as the child fights to maintain his/ her balance when walking.
Toe-walking gait not only affects a child's posture, but also increases the potential risk of the development of contractures (shortening) of tendons and muscles, leading to permanent stiffening of the ankle and knee in later life.
How can ankle and foot orthoses help?
One way to help prevent this type of walking is to fit a below-knee ankle/foot orthosis (AFO), which can help control any abnormal movement of the foot and ankle during walking, play or rest.
A well-made and close fitting AFO will help stabilise the foot and ankle to bring about ankle stability and improve balance, posture and confidence. An AFO can help lift the foot, preventing tripping over, reducing accidents and making walking easier and less tiring. Controlling the foot and ankle will also influence hip and knee position in a positive manner and in turn lead to potential improvements in the child's gait, balance and posture.
The foot plate of the AFO can be flat or contoured depending on your child's requirements. Insoles can be incorporated into the AFO to help maintain a good foot posture. Modifications can also be made to the outside of the AFO, or even your child's footwear after fitting, in order to 'fine tune' the AFO. Small, post-supply adjustments can also increase the effectiveness of the AFO. This is most commonly carried out to adjust heel height, which changes the angle of the lower leg in relation to the ground when walking (tibial shaft angle).
An AFO should be able to fit into the child's own footwear (not always problem-free but usually possible), which means they will be more willing to wear it. Sometimes wider or larger shoes are necessary to accommodate an AFO.
An AFO should never be uncomfortable for a child to wear, and they should be able to wear it happily for most of their active day. Sometimes AFOs can rub on pressure points and create 'sore spots', so it's important to monitor your child's foot, especially the heel and ankle.
Do all children with hemiplegia need an AFO?
Not all children need an AFO. But those who do not have the problems of a toe walking gait may still have general weakness or some instability of the ankle joint complex. This can lead to balance problems, such as walking with legs wide apart and a general loss of confidence.
The ankle may tend to collapse into a varus or valgus position. When the back foot is held in a valgus position (collapsing inwards), the arch of the foot tends to flatten along with it (overpronation). A varus back foot position (twisting outwards) tends to create a high arched foot (supination).
In cases like this, the fitting of foot orthoses can be helpful in reducing unwanted foot and ankle positions and consequently improving balance and posture.
Types of AFO
Solid Ankle AFO
AFOs can be made with a solid ankle complex, which holds the foot and ankle at a set angle, usually around 90 degrees if the child can get to this position easily (neutral plantargrade position). This prevents the foot and ankle from being pushed down (plantarflexion) and prevents the development of a toe-walking gait as well as sideways movements of the ankle (valgus and varus movements).
Solid AFOs can be used very effectively in providing stability and encouraging a good base of support in young children with hemiplegia. You may find that when your child starts to pull to stand and move around furniture, a fixed AFO is a good option to provide support and give them confidence.
Solid AFOs are also used where an existing contracture (muscle or tendon shortening) already exists and the child has no ankle movement.
While the use of a solid ankle AFO can be helpful in certain circumstances, it is not just incorrect movement that is restricted. The ability to dorsiflex (see the above section on walking and posture problems) is lost too, and for some children this won't be suitable.
Articulated or hinged AFO
The hinged AFO is in many ways very similar to the fixed ankle type. During the manufacture of the hinged AFO, a simple mechanical joint is fitted at the level of the ankle joint and incorporated into the moulding. A backstop is fitted behind the ankle to prevent plantarflexion (toe walking).
A hinged AFO allows the ankle to dorsiflex while limiting plantarflexion past an agreed angle (commonly but not always around 90 degrees). The child can bend his or her foot upwards but not downwards. Because of this, a hinged AFO can provide a more natural, fluent gait, allowing the foot and ankle to dorsiflex during daily activities such as standing from sitting, sitting from standing, crouching, going up and down stairs, walking up hill and walking backwards.
A hinged AFO provides the same medial (inside) and lateral (outside) stability for the ankle as a solid ankle AFO and so prevents valgus or varus positioning. However, hinged AFOs are wider at the ankles and this can create more problems when it comes to fitting them into regular footwear.
Footwear and adaptations
Measures that can help reduce ankle and foot instability range from simple supportive footwear to footwear with adaptations and complex multi-material biomechanical and functional foot orthoses.
Footwear alone has little effect on severe foot instability, but it can be useful for improving stability in an unstable ankle when a child starts to walk. The special footwear has a wide, flat, good-gripping sole with increased stiffening around the ankle, and this can help give a child a greater sense of balance. But be aware that the foot itself may still roll around inside the boot unseen, and therefore it's essential to fit this type of footwear carefully.
Adaptations to footwear, such as wedges to the inside (medial) or outside (lateral) of the boot, can help increase control over unstable ankles. Foot orthoses can be incorporated into footwear to improve foot stability. These usually come in the form of insoles with arch support and heel cups, which are extended up around the heel but finish below the ankle.
Both these types of foot orthoses may have special wedging (posting) fitted, either to the outside (extrinsic) or built into the orthoses (intrinsic). The posting or wedging is fitted to produce a correcting force on the heel when the child is weight-bearing or walking. These foot orthoses are usually constructed of lightweight thermoplastics and made from a cast of the child's foot held in a corrected position.
SMOs and DAFOs
Unlike more traditional rigid orthoses, Supramalleolar Orthoses (SMOs - orthoses that finish just above the ankle) or Dynamic Ankle Foot Orthoses (DAFOs - a brand name) are thin and flexible. They come in a variety of designs and can be very useful in improving medial and lateral stability around the ankle.
SMOs and DAFOS promote good weight bearing, and this in turn can lead to reduced toe walking and a reduction in muscle tightness. However, they offer less control over increased high tone (muscle tightness), excessive dorsiflexion or plantarflexion. They are therefore not effective for correcting a medium to severe toe-walking gait pattern. They are not able to hold the foot up as well as an AFO when stepping forwards, and so tripping may still be an issue.
SMOs and DAFOs stabilise the position of the foot when a child is standing and taking weight through their foot in walking. This must be taken into consideration when the child is assessed. They are often used when a child is developing skills and their gait is developing, so their need for an orthosis gradually decreases. SMOs and DAFOs can be an interim option when little children are still crawling and pulling to stand, as they are less restrictive but still offer some support.
There are a number of alternative treatments available from the NHS or via private health professionals. These include compression garments (elasticated material orthoses or splints).
Although some people use these orthoses for their foot/leg, they are more often used for arm/hand. At the moment there is no conclusive medical evidence of the benefits of these garments in children with hemiplegia, but there are families who've said they have worked for their children. They may be useful for children who have a type of muscle stiffness called dystonia, where the muscles pull in more than one direction, making rigid splints very painful.
However they are not the answer for all children with hemiplegia, and you should take care, with advice from professionals closely involved in your child's care, with this treatment.
Whatever type of orthosis is recommended or fitted, they share many common design points and all aim to provide some or all of the elements below:
- Heel foot stability (close moulding around heel).
- Mid-forefoot stability (medial & lateral extensions, good arch support).
- Control of unwanted exaggerated and abnormal movements.
- Reduction of the effects of increased tone (spasticity).
- Promotion of a stable base.
- Encouragement of good standing position with equal weight bearing on both feet.
- Toe and metatarsal support (tone management).
- To prevent scrunching the toes.
- Contoured sole plates to assist in foot stabilisation (tone reduction).
- Construction from semi flexible or rigid materials (polypropylene, polythene etc).
Getting an AFO
Orthoses are not a stand-alone solution to balance, posture and gait difficulties caused by hemiplegia. They are commonly used with other interventions as part of a child's overall management programme. It is also true that no two children are the same, and what works for one might not work for another.
The goal of splints is to provide the least amount of restriction as possible while still encouraging and promoting a child's own abilities and long-term development. It is important that a full assessment is carried out in a relaxed environment to ensure that the correct orthotic prescription is made. A quick 10-15 minute consultation in a busy clinic to take a decision on orthotic provision and design will most probably not lead to the best outcome.
When choosing the best splint to supply, the orthoptist and therapist should consider what developmental level your child is at, what they do all day and how the splint will be worn and how easy it is to get on and off. Older children might not want to use a splint because of how it looks. You should consider this carefully and discuss this with them so that they agree any treatment before it is supplied.
You should be given information about when to wear the splint, how to look after it and what to do if there are problems. Once fitted with an orthosis, your child will need to have regular reviews to ensure that they continue to be effective they develop and grow. Similarly, when they grow out of their orthosis, always ask yourself the question: is my child still getting some benefit from this type of orthosis? A full assessment must be carried out again to review the type of orthotic management they need.