Orthotic Design for Foot Pathologies

Original Editor - Carin Hunter based on the course by Donna Fisher Top Contributors - Carin Hunter, Jess Bell, Kim Jackson, Stacy Schiurring, Tarina van der Stockt, Vidya Acharya and Lucinda hampton

Commonly Used Types of Orthotics

1. Ankle Foot Orthoses (AFO)

The AFO is the basic orthosis in CP and is a crucial piece of equipment for many children with spastic diplegia. The main function of the AFO is to maintain the foot in a plantigrade position. This provides a stable base of support that facilitates the function and also reduces tone in the stance phase of the gait. The AFO supports the foot and prevents foot drop during swing phase. When worn at night, a rigid AFO may prevent contracture. AFOs provide a more energy efficient gait. The brace should be simple, light but strong. It should be easy to use. Most importantly it should provide and increase functional independence.

For more information on this, please see Introduction to Ankle Foot Orthoses

2. Functional Foot Orthosis (FFO)

• Heel Skives- intrinsic (on model)
• Medial (Kirby)- shifts force applied laterally, supinates/inverts –
• PTTD, Plantarfacsitis
• Lateral shifts force applied to heel medially and pronates/everts
• Inversion of the positive cast increases arch height under the base of the first metatarsal resulting in plantarflexion of the first metatarsal -

3. Total Contact Insoles (TCI)

• Design from Examination as per FFO
• Support- through shape and density of materials
• Accommodation - fixed deformities, ground to meet feet or feet to ground, blocks test, easier due to construction than with FFO
• Shock absorption – better than FFO due to materials.
• EVA (Ethyl Vinyl Acetate)
• TCI’s - Measurement
  • Custom made – usually E.V.A. – High, Medium & Low Density
  • Cast, foam box, scan
  • Workshop manufactured or Lab
  • Intrinsic modification/ extrinsic posting
• Can be bulky
• Support, correct, Accommodate
• Shock absorbing

Non-pathological Foot

1. No underlying condition
2. Normal foot structure
3. Pain
4. Musculoskeletal issues
5. Trauma
6. Tendon dysfunction

Congenital Paediatric Problems

1. Flexible Pes Planus
2. Accessory Navicular
   1. Congenital 12% pop., pain, redness, PTTD
3. Vertical talus
   1. Congenital, may have other conditions, rocker bottom foot
4. Freiberg's Disease
   1. Forefoot pain, stiffness, 2nd MPT, rare
5. Cavus Foot
   1. High arch, CTEV

Flexible Pes Planus

Pes Planus in a toddler

Pes planus also known as flat foot is the loss of the medial longitudinal arch of the foot, heel valgus deformity, and medial talar prominence. In lay terms, it is a fallen arch of the foot that caused the whole foot to make contact with the surface the individual is standing on. The deformity is usually asymptomatic and resolves spontaneously in the first decade of life, or occasionally progresses into a painful rigid form which causes significant disability. All at birth has flat feet and noticeable foot arch are seen at around the age of 3years.

It is of two forms; flexible flat foot and rigid flat foot. When the arch of the foot is intact on heel elevation and non-bearing but disappears on full standing on the foot, it is termed flexible flat foot while rigid flat foot is when the arch is not present in both heel elevation and weight bearing.

Tests: Jacks Test, arch recreates

Treatment: Off the Shelf (OTS) Insoles

1. Generally standard neutral position
2. Standard arch support
3. Different densities
4. Low profile
5. Shock absorption
6. Minimal correction
7. No accommodation of deformity
8. Good starting point

Adult Non-pathological Foot – Common Problems

1. Adult Acquired Flat Foot (AAFF)- most common caused by Posterior Tibial Tendon Dysfunction
2. Posterior Tibial Tendon Dysfunction
3. Plantarfasciitis
   1. Inflammation of plantar fascia
   2. Windlass test +/-, common symptoms, pain , am, n/splints
4. Hallux rigidus/limitus
   1. Flexibility of 1 st MTP
   2. Test, to ax limitus or rigidus, try to encourage flexion by inc p/f 1st ray
5. Metatarsalgia
   1. Prominent bony structures, pain
6. Morton's Neuroma
   1. Mulder’s test
7. Heel spurs
   1. Specific heel pain, treat with off load device
8. Claw/ hammer toes
   1. Fixed/mobile
   2. pain
   3. callousing
   4. shoes
9. Arthritis
   1. shock absorption, support off load

Posterior Tibial Tendon Dysfunction

Occurs when the posterior tibial tendon becomes inflamed or torn. As a result, the tendon may not be able to provide stability and support for the arch of the foot, (PTTD) is characterized by degeneration of this tendon and is progressive if not treated. Can be associated with tear or stretching of spring ligament. The spring ligament functions as static restraint of the medial longitudinal arch, it supports the head of the talus from planter and medial subluxation against the body weight during standing. Can be ruptured or torn.

• Posterior tibial tendon dysfunction characteristically is a slow onset condition mainly affecting women older than 40 years of age.
• • Risk factors include obesity, hypertension, diabetes, steroid use and seronegative arthropathies.
• • Patients may complain of pain and swelling around the medial ankle, difficulty mobilizing or exacerbation of an existing limp.
• • Examination may show tenderness along the course of the tendon, A change in the shape of the foot. The heel is everted and the arch collapsed. Flexibility reduced

Test: “too many toes” when feet are viewed standing from behind. and Difficulty performing a single heel raise. Heel remains in everted position

• 5 stages

1. I. Acute
2. II. Flexible (FFO)
3. III. Fixed –Arizona
4. IV. Chronic –AFO
5. V. Chronic – surgery

Treatment: The treatment plan for posterior tibial tendon tears varies depending on the flexibility of the foot.

1. PTTD Orthotic Prescription
   1. Goal - reduce the excessive pronatory forces acting across the subtalar joint (STJ) axis.
   2. Design -
      1. The orthoses must control pronation with significant surface area contacting the foot. The modifications should increase supinatory torque across the STJ axis.
      2. Polypropylene Shell - semirigid
      3. Deep Heel Cup
      4. The deep heel cup increases surface area medial to the STJ axis applying a supinatory torque
      5. Medial Heel Skive – 4mm or 6mm
      6. The medial heel skive increases force medial to the STJ axis to reduce excessive STJ pronation and heel eversion.
   3. Measurement of FFO
      1. Cast, foam box, scan to capture shape of foot
      2. Modify intrinsically in w/shop or lab
      3. Extrinsically posting/adaptions can be added
      4. • Often off site manufacture
      5. • Low profile- full, 3⁄4, court, sports
      6. • Limited shock absorption or accommodation
   4. Design/Prescription of FFO
      1. o Based on Exam/assessment
   5. o Main issue- part of gait cycle, ie MS or push off
      1. o Determine what mechanism for problem
      2. o Pes planus, arch support
      3. o STJt rotation, wedging
      4. o Problems higher up, compensation
      5. o Weakness/tightness, hips, knees
   6. Principle of orthotic design
      1. o Position of heel/forefoot and STJt rotation
      2. o Medially rotated STJt
      3. o Increased pronation moment/ decreased supination moment
      4. o Rebalance by moving GRF medial, increasing supination moment, reducing medial rotn
      5. o Laterally rotated STJt
      6. o Increased supination moment, decreased pronation moment
      7. o Rebalance by moving GRF closer to STJt, to increase pronation moment of GRF

o Not this simple, look at tibia and knee hip alignment

FnHlimitus

1. Functional Foot Orthosis (FFO)
   1. Arch Fill – can increase or decrease arch support, be careful.
   2. 1st ray /1st met cut out- allows the 1st ray to plantarflex- key for normal gait, windlass. Not always necessary if corrected cast used- FnHl, Plantar flexed 1st ray
2. Functional Foot Orthosis (FFO)
   1. Mortons extension ( not to be confused with Mortons neuroma)
   2. Extra material added under 1st met heads only to increase plantar pressure and flex 1st met head, Can be Rigid or flexible useful in treating HR, to reduce painful mvt, protect stiff joint also shoe mod can help
3. Reverse- extra added under 2-5 to allow plantarflexion of 1st ray-
4. FnHR, allows p/flexion of 1st ray and increases flexion MTP, windlass.

Non-pathological Foot - Injury /Trauma

1. Shin splints – Med. Tibial Stress Syndrome
2. Overuse injury, Tib post./Tib ant-
   1. Support, reduce overuse by balance, shock absopt and rest
3. Inversion injury/Lat ankle sprain-
   1. Ant/post TaloFibL, CalcFibL- lateral wedge, increase pronation to stabilise.
   2. Eversion – Deltoid, less common
4. Lisfranc Injury/Trauma
5. Achilles Tendon injuries-
   1. relieve with heel post, stretch

Common Pathological Foot Conditions

1. Neurological

1. Cerebral Palsy

1. Stroke
2. Multiple Sclerosis

2. Motor

1. Ataxia
2. Dystonia
3. Pathological Foot

3. Sensory/ Neuropathy

1. Diabetes
   1. Sensory
   2. Neuropathic issues
   3. Pressure areas
   4. PTTD
   5. Off -Loading Diabetic Ulcers
   6. Toe fillers amputation
2. Charcot Marie Tooth
   1. Orthotic Insoles
3. Down Syndrome
4. Autism Spectrum Disorder

Pathological conditions- more complex as all joints/muscles affected

• Look at hip knee position

• Feet ankles will adapt to ground to support structures higher up and compensate for bony abnormalities

Pathological Foot- Valgus Deformities

Rocker Bottom Foot- accommodate, support.

Hyper-mobility- if OTS does not work for paediatric hypermobility

Escape Valgus – Accommodate for tight TA

Escape Valgus

Compensatory movement- heel pulls into valgus/eversion

Over pronates mid foot

Driven by tight TA

Can alter foot structure

Can result in long term issues

Cavus/Varus Deformity

Cavo Varus deformity can be the result of a plantar flexed first ray (forefoot-driven), a deformity of the hindfoot (hindfoot-driven), or a combination of both.

Weakness in tibialis anterior & peroneal brevis ( which dorsiflex and evert)

Tight plantar fascia

Over-active peroneus longus, pulls 1st ray into p/flexion

Plantar-flexed first ray

C.T.E.V./HMSN

Fore foot v Hind foot Deformity

In midstance, plantarflexion of the first ray leads to a compensatory varus heel, supination of STJt and reduced shock absorption.

During heel-off (terminal stance), the plantarflexed first ray causes a supination of the forefoot that increases the varus deformity of the hindfoot.

In hindfoot-driven cavo-varus deformity, the subtalar joint may compensate for varus deformities above the ankle joint.

Overload of the lateral soft tissue structures (eg, lateral ligament complex, peroneal tendons) and degenerative changes (eg, medial ankle osteoarthritis, midfoot arthritis) may occur over time.

Coleman Block Test

Lateral Forefoot Wedge

In summary

o Anatomy- complex mechanism to allow standing, balance,

walking, running, jumping, lifetime of external factors

o Assessment / history, passive, static, dynamic

o No one correct solution, watch, listen and learn

oPatient and clinical education

oOrthotics in combination with other MDT treatments

Physiopedia Pages to Further Your Knowledge

Orthotics in Cerebral Palsy

Biomechanics for Cerebral Palsy Orthotics