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Orthoses for neurological ankles
  1. Stephen Kirker
  1. Rehab Medicine Department, Cambridge University Hospitals NHS Foundation Trust, Cambridge, UK
  1. Correspondence to Dr Stephen Kirker, Rehab Medicine Department, Cambridge University Hospitals NHS Foundation Trust, Cambridge, UK; stephen.kirker{at}addenbrookes.nhs.uk

Abstract

Patients with weakness or abnormal posture of their lower leg may benefit greatly from appropriate orthoses. This paper describes the sorts of problems that can be helped in neurological practice and the range of devices commonly used, and also highlights some of the factors influencing selection. With greater understanding of their use, clinicians will feel more confident about referring patients for early orthotic assessment.

  • cerebral palsy
  • electrical stimulation
  • gait
  • stroke
  • rehabilitation

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Introduction

An orthosis is a device that supports residual function, whereas a prosthesis replaces that function. Splints and prostheses have been used for thousands of years, for example, on an Egyptian mummy’s foot from 2700 BC. Orthoses are now named according to the joints they work on: I will confine myself to ankle foot orthoses in neurological practice, and not consider diabetic complications, sports injuries and orthopaedic patients.

Orthoses can help many patients with poor control of the lower limb: there is often a biomechanical solution to a biomechanical problem, which can improve safety in standing and walking, while physiotherapy concentrates on motor learning. There has been concern that using an ankle foot orthosis (AFO) early after a stroke may impair recovery of normal muscle control; however, there is now good evidence that this is not the case1 2 and early referral to orthotics service of patients who had a stroke with mobility problems is recommended.3 4

Foot drop in swing phase (while the foot is not in contact with the ground) is the most obvious indication for an ankle orthosis, but some patients may benefit more from improved stability during stance phase (while the foot is touching the ground, during part of which, it is taking all the body weight) by a ‘well-tuned’ AFO. This involves supporting the ankle and hence the knee at the best compromise of angles to stabilise the knee during mid stance phase, while permitting knee flexion at the beginning of swing phase.

Evidence to guide clinical practice

When considering orthotic options, the first question is whether there is need for compensation or control during stance phase of gait. These functions usually require a bespoke moulded AFO. Only when there is no need for this, can one supply a simple stock device to support foot drop in swing phase.(table 1)

Table 1

The main types of impairment seen in neurological orthotic practice are listed in approximate order of severity, noting problems in swing phase, stance phase and commonly used orthotic prescriptions

Published evidence emphasises the importance of optimising the alignment of AFO and footwear5 6 and the stiffness of the AFO for individual patients.7 Once this has been achieved, the available options may not permit a realistic comparison in a trial, or the patients become so highly selected that the results do not inform clinical practice.8 9 The great majority of trials recruit ambulant patients who had a stroke with weak dorsiflexors, relatively normal range of movement, and little or no spasticity. The other group that has been extensively studied is children with cerebral palsy, commonly with crouch gait.10 Systematic reviews11–20 conclude that AFOs work better than nothing, even many years after stroke, and there are similar results with AFO and functional electrical stimulation.

The specific neuropathology causing the biomechanical problem rarely affects the orthotic prescription, other than when the pathology anticipates rapid deterioration. Then, prompt supply of a device that is 80% of ideal is better than a 3-month delay in supply of a device that would have been 90% of ideal when prescribed, but which no longer works as the patient has changed so much in the interim.

Swing phase

Weak dorsiflexors causing foot drop in the swing phase of gait may be supported by simple elastic foot lifters, stock plastic or carbon fibre AFO of low stiffness, bespoke silicone or Lycra, or functional electrical stimulation. The major factor influencing selection is patient preference among devices that their National Health Service will offer, or what they are prepared to buy privately. Appearance is the most common concern,21 22 but also important is restriction of movement that prevents them standing from sitting or getting up if they fall, comfort, feeling too hot, ease of donning and selection of footwear.

Functional electrical stimulation may be preferred over a rigid device because it is lighter, cooler, and does not take up much space in shoes11; however, it is not commissioned in all services, so patients may have to travel to supraregional clinics to try this. Functional electrical stimulation does not work with peripheral nerve, muscle or tendon lesions, or with high muscle tone in plantar flexors or inverters. It does not compensate for contractures and does not enhance stability in the stance phase of gait, and requires more competence from the patient to use it than a mechanical device. Hence, only a small proportion of patients with poor ankle control use it.

Stance phase

When an orthosis aims to compensate for loss of normal passive range of movement, to resist higher muscle tone or to control ankle and knee movement during the stance phase of gait, a bespoke moulded AFO is usually made. When higher forces are necessary to control the ankle and knee posture in stance, these must be applied over as wide an area as possible. Hence, moulded AFOs are designed to fit closely all around the sole, heel, sides of the foot and ankle, sides and back of lower leg.

When the size of the lower leg fluctuates due to oedema or joint swelling, a close fitting moulded AFO should not be used because it cannot expand or contract to accommodate change in size. If oedema can be controlled with a compression stocking or diuretic medication, a moulded AFO may fit more of the time, but an external caliper, made for a single pair of shoes, is often the only option.

When to refer to an orthotics service

It is safe for patients to buy or physiotherapists to supply devices to support foot drop during swing phase, as comfort and appearance are the main factors influencing patient satisfaction. However, AFOs to control the limb in stance phase require assessment and prescription by an orthotist due to the much higher forces involved and potential for making the situation worse, with skin breakdown, less stable gait, loss of confidence and musculoskeletal pain.

Referral for orthotic assessment is often late,23 for instance after waiting to see how much improvement occurs with time and physiotherapy. Orthoses may improve the effectiveness of early rehabilitation, for instance by allowing safe weight bearing through a weak limb for transferring with a Rotastand, and reducing the risk of injury during gait training. With greater understanding of their use, clinicians should feel more confident about referring patients for early orthotic assessment.

Figure 1

Darco wedge shoe. Therapeutic trial before modifying patient's own footwear. Moves fulcrum of initial contact from behind to under ankle joint. Reduces load on tibialis anterior at initial contact.

Figure 2

Rocker sole. Moves fulcrum of initial contact from behind to under ankle joint. Also facilitates rollover when ankle is fused.

Figure 3

Plastic posterior leaf spring ankle foot orthosis. Cheap so likely to be kept in physiotherapy or orthotics stock for same day supply. Modest stiffness limits effect in stance. Safe for patients to buy from internet. Assumes ankle rests in neutral position.

Figure 4

Thin carbon fibre ankle foot orthosis (AFO). Assumes ankle rests in neutral position. Thin lamination, so mild support of dorsiflexion in swing. Stiffer than a plastic posterior leaf spring AFO, so a little more effect in stance.

Figure 5

Elastic foot lifter. Only helps in swing phase. Safe for patients to buy from internet. Works best with lace up shoes. Orthotix.co.uk.

Figure 6

Home made elastic foot lifter. Puppy collar and bungy cord.

Figure 7

Bespoke silicone ankle foot orthoses. Most often bought privately for aesthetic reasons. Dorset Orthopaedic Co Ltd.

Figure 8

Stiff carbon fibre ankle foot orthosis. Assumes ankle rests in neutral position. Thick lamination, much stiffer, so strong resistance to plantarflexion can overcome modest spasticity pulling into plantarflexion and inversion. Strong resistance to dorsiflexion allows ground reaction force to support knee extension in stance and may give some spring at toe-off.

Figure 9

Custom moulded knee ankle foot orthosis. Moulded AFOs must be close fitting and cannot be used if oedema causes change in limb volume. This one also has a thigh corset; hence, it is a knee-ankle-foot orthosis. (KAFO) May allow use of several different pairs of shoes, unlike the caliper figure 13, made for the same patient to accommodate swelling.

Figure 10

Custom moulded ankle foot orthosis. Big heel build up to accommodate fixed ankle plantarflexion.

Figure 11

Pressure relieving ankle foot orthosis. Prevents any pressure on back of heel to prevent or relieve pressure sore. Maintains existing ankle range and can be bent to accommodate fixed plantarflexion.

Figure 12

Caliper. External caliper and bespoke footwear for the same patient as figure 10, usable when leg swelling prevents use of close fitting moulded device.

Figure 13

Turbomed ankle foot orthosis. Worn outside shoe, said to facilitate sports and high activity. TurboMed Orthotics.com.

Figure 14

Contracture-correcting ankle-foot orthosis. Strong springs in joints beside ankle give powerful dorsiflexion force, but accommodates to voluntary or involuntary plantarflexion, unlike a rigid plaster cast.

Figure 15

Bespoke dynamic lycra ‘lift up sock’. May improve ankle control if proprioception is facilitated by compression, otherwise only helps in swing phase. DM Orthotics.com.

Key points

  • Orthoses can help get people back on their feet early after new impairment.

  • Early use of orthoses does not impair subsequent recovery of weak muscles.

  • Consider referral to orthotics whenever referring to physiotherapy.

  • Modern devices offer better aesthetics and function than old fashioned calipers.

Further reading

  • Folmar E, Jennings H, Lusardi M. Principles of Lower Extremity Orthoses. In Chui K, Jorge M, Yen S-C and Lusardi M. (eds) Orthotics and Prosthetics in Rehabilitation. St Louis. Elsevier. 2020. 220–258

  • Best Practice Statement. 2009 https://www.healthcareimprovementscotland.org/previous_resources/best_practice_statement/ankle-foot_orthoses_stroke.aspx. Accessed date 31 Dec 2021

  • Daryabor A, Arazpour M, Aminian G. Effect of different designs of ankle-foot orthoses on gait in patients with stroke: A systematic review. Gait Posture. 2018 May;62:268–279. doi: 10.1016/j.gaitpost.2018.03.026. Epub 2018 Mar 16. PMID: 29587246.

  • Prenton S, Hollands KL, Kenney LP. Functional electrical stimulation versus ankle foot orthoses for foot-drop: A meta-analysis of orthotic effects. J Rehabil Med. 2016 Oct 5;48(8):646–656. doi: 10.2340/16501977-2136. PMID: 27563700.

Ethics statements

Patient consent for publication

Ethics approval

This study does not involve human participants.

References

Footnotes

  • Contributors SK wrote this paper and took most of the photographs.

  • Funding The authors have not declared a specific grant for this research from any funding agency in the public, commercial or not-for-profit sectors.

  • Competing interests None declared.

  • Provenance and peer review Commissioned; externally peer reviewed by Eleanor Marsh, Cardiff, UK.

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  • Editors’ commentary
    Phil E M Smith Geraint N Fuller

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