Orthotic Design for Foot Pathologies

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

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 – Congenital 12% pop., pain, redness, PTTD
3. Vertical talus – Congenital, may have other conditions, rocker bottom foot
4. Freibergs Disease – Forefoot pain, stiffness, 2nd MPT, rare
5. Cavus foot – High arch, CTEV

The Child’s Foot – flexible pes planus

o Flexible Pes Planus – Jacks Test, arch recreates

Off the Shelf (OTS) Insoles

oGenerally std neutral position

oStd arch support

oDifferent densities

oLow profile

oShock absorption

oMinimal correction

oNo accommodation of deformity

oGood starting point

Adult Non-pathological Foot – Common Problems

o Adult Acquired Flat Foot (AAFF)- most common caused by

o PTTD - 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.

• 5 stages

o 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.

PTTD

• Posterior Tibial Tendon Dysfunction

I. Acute

II. Flexible (FFO)

III. Fixed –Arizona

IV. Chronic –AFO

V. Chronic – surgery

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

PTTD I & II

• 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.

• Difficulty performing a single heel raise. Heel remains in everted position

PTTD Orthotic Prescription

• Goal - reduce the excessive pronatory forces acting across the subtalar joint (STJ) axis.

• Design - The orthoses must control pronation with significant surface area contacting the foot. The modifications should increase supinatory torque across the STJ axis.

• Polypropylene Shell - semirigid

• Deep Heel Cup

• The deep heel cup increases surface area medial to the STJ axis applying a supinatory torque

• Medial Heel Skive – 4mm or 6mm

• The medial heel skive increases force medial to the STJ axis to reduce excessive STJ pronation and heel eversion.

Measurement of FFO

• Cast, foam box, scan to capture shape of foot

• Modify intrinsically in w/shop or lab

• Extrinsically posting/adaptions can be added

• Often off site manufacture

• Low profile- full, 3⁄4, court, sports

• Limited shock absorption or accommodation

Design/Prescription of FFO

o Based on Exam/assessment

o Main issue- part of gait cycle, ie MS or push off

o Determine what mechanism for problem

o Pes planus, arch support

o STJt rotation, wedging

o Problems higher up, compensation

o Weakness/tightness, hips, knees

Principle of orthotic design

o Position of heel/forefoot and STJt rotation

o Medially rotated STJt

o Increased pronation moment/ decreased supination moment

o Rebalance by moving GRF medial, increasing supination moment, reducing medial rotn

o Laterally rotated STJt

o Increased supination moment, decreased pronation moment

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

Adult Non-pathological Foot – General foot problems

1. Plantarfascitis – inflammation of plantar fascia
   1. o Windlass test +/-, common symptoms, pain , am, n/splints
2. o Hallux rigidus/limitus – Flexibility of 1 st MTP
   1. o Test, to ax limitus or rigidus, try to encourage flexion by inc p/f 1st ray
3. o Metatarsalgia – Prominent bony structures, pain
4. o Mortons Neuroma – Mulder’s test
5. o Heel spurs – Specific heel pain, treat with off load device
6. o Claw/ hammer toes Fixed/mobile, pain, callousing,shoes
7. o Arthritis- shock absorption, support off load

Functional Foot Orthosis (FFO)

o Heel Skives- intrinsic (on model)

o Medial (Kirby)- shifts force applied laterally, supinates/inverts –

o PTTD, Plantarfacsitis

o Lateral shifts force applied to heel medially and pronates/everts

o Inversion of the positive cast increases arch height under the base of the first metatarsal resulting in plantarflexion of the first metatarsal -

FnHlimitus

Functional Foot Orthosis (FFO)

o Arch Fill – can increase or decrease arch support, be careful.

o 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

Functional Foot Orthosis (FFO)

o Mortons extension ( not to be confused with Mortons neuroma)

o 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

o Reverse- extra added under 2-5 to allow plantarflexion of 1st ray-

FnHR, allows p/flexion of 1st ray and increases flexion MTP, windlass.

Non-pathological Foot - Injury /Trauma

o Shin splints – Med. Tibial Stress Syndrome

o Overuse injury, Tib post./Tib ant-

o Support, reduce overuse by balance, shock absopt and rest

o Inversion injury/Lat ankle sprain-

o Ant/post TaloFibL, CalcFibL- lateral wedge, increase pronation to stabilise.

o Eversion – Deltoid, less common

o Lisfranc Injury/Trauma

o Achilles Tendon injuries- relieve with heel post, stretch

Pathological Foot

• Neurological/Motor

• Sensory

• Neuropathy

Pathological Foot – Associated Conditions

o Neurological

o CP

o Stroke

o MS

• Motor

o Ataxia

o Dystonia

Pathological Foot

o Sensory/ Neuropathy

o Diabetes

o HSMN- CMT

o Downs

o ASD

TCI’s - Measurement

o Custom made – usually E.V.A. – High, Medium & Low Density

o Cast, foam box, scan

o Workshop manufactured or Lab

o Intrinsic modification/ extrinsic posting

o Can be bulky

o Support, correct, Accommodate

o Shock absorbing

Total Contact Insoles (TCI)

o Design from Examination as per FFO

o Support- through shape and density of materials

o Accommodation - fixed deformities, ground to meet feet or feet to ground, blocks test, easier due to construction than with FFO

o Shock absorption – better than FFO due to materials.

o EVA (Ethyl Vinyl Acetate)

The Diabetic Foot

• Sensory

• Neuropathic issues

• Pressure areas

• PTTD

• Charcot foot

• At Risk

Diabetic Treatment

Off -Loading Diabetic Ulcers

Charcot Foot

Orthotic Insoles

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Diabetic Spec – Toe fillers amputation

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

o Rocker Bottom Foot- accommodate, support.

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

o Escape Valgus – Accommodate for tight TA

Escape Valgus

oCompensatory movement- heel pulls into valgus/eversion

oOver pronates mid foot

oDriven by tight TA

oCan alter foot structure

oCan result in long term issues

Cavus/Varus Deformity

o 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.

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

o Tight plantar fascia

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

o Plantar-flexed first ray

o 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