Purpose & Goal of Orthotics
- Purpose: control abnormal comensatory movements for the foot by bringing the foot to the floor (surface)
- Goal: create a biomechanical balanced kinetic chain by controlling/reducing pathologic motion in the foot and leg by maintaining the foot in or close to subtalar neutral position
Subtalar joint flexibility & stability during gait
Initial contact
* subtalar shock absorber
* pronation subtalar: rotation of the tibia in absorb contact-flexible
* loose subtalar joint–> rotates the tibia and affects knee joint
Midstance
* loading response moves into full pronation
* should be supinated for gastroc to push off
Terminal Stance
* moves into supination and becomes ridgid
* subtaler joint requires flexibility for uneven surfaces/gait/balance
In close chain: over pronation may create kinetic problems like…
- anterior pelvic tilt
- internal rotation femur
- valgus knee
- medial rotation of fibula and tibia
- medial rotation talus
- adduction and plantarflex talus
- calcaneal eversio
In close chain with supination may cause kinetic problems like…
- PPT
- femur ER
- knee varus
- lateral rotation of tibia and fibula
- abdction and dorsiflex talus
- calcaneal inversion
Knee adduction moment (KAM)
- biomechanical variable associate with knee osteoarthritis with KAM.
- During walking the leg produced an adduction moment that places the knee into varus.
- During walking, 60-70% of WB forces passes thru this compartment
- KAM produces to increase in GRF
- The wider the angle, the more compressive forces in the medial knee
- Knee varus increases KAM
Types of foot othoses
- heel cup
- heel lift
- wedge
- cushion
- Othotics are LE supportive apparel that provide soft tissue protection, bone/joint stability & control of body segment motion
- orthotics play an important role in the nonoperatuve treatment of foot and ankle pathology
- The type needs to be specific for the underlying bony or ligamentous pathology in order to provide appropriate functional support
Overall function
Stabalization
* static: rigid device, supports body segment in fixed postion
* dynamic: mobile device, permits body segment motion
* combination
Principles
* patient-related (easy don on and off)
* soft tissue: not break skin down
* at risk diagnosis (diabetics, neuropathy
* tolerant to compression and shear forces
* functional level of pt.
Types of foot orthosis (inserts and instability)
Inside shoe or inserts
* modify heel, midfoot or forefoot
* padding for pain (metatarsalgiam plantarfasciiti)
* heel lift for leg length
* wedge for supination/pronation
Instability
* heel cup for calcaneus
* longitudinal arch support
* UCBL
Orthotics for KAM
The scientific research to date very clearly demonstrates that appropriately designed valgus-wedged insoles and/or orthoses (for varus knee) can be very effective at reducing the external knee adduction moment, reducing the medial comparement loading forces and thus reducing the medial knee pain in pts. with mild to moderate medial knee compartment knee OA
UCBL
- best use is for significant pronation (navicular bone is dropping, mid foot collapse, calcaneus everted)–prevents knee osteoarthritis
- navicular drop test (>10mm is a positive test)
- for significant calcaneal eversion & midfoot support
UCBL
* rearfoot: controls the calcaneal alignment
* trim lines: higher the trim lines better control of the calcaneus.
Steps to assess the need of ankle orthotic
1. gait deviation
A. Swing phase: drop foot
AFO: consider leaf spring versus dorsiflexion assist
B. Stance Phase
* Ankle instability
solid AFO
hinged AFO
* Ankle plantarflexion
solid AFO with strap support
* knee hyperextension
setting ankle joint at neutral or a bit of dorsiflexion
2. protection from injury
* decubitus ulcer
* joint protection from instability
AFO
- Adaptations of the trimline for more or less control
- need a lot of support- many trimlines up the leg and straps
- Widely prescribed:
weakness
stroke
CP
head injury
peripheral neuropathy
alignment
SCI
progressive disease
Every orthosis…
- uses force principles to the limb to accomplish the goals of its design
- an orthosis is most comfortable and effectuve when
1. pressure=force/area
2. control direction of primary force and direction of counterforces
Leaf spring AFO: drop foot
- mass produced orthotic
- dynamic thermoplastic AFO
- shallow trim lines for less support & control, no straos to control brace fit
- suppory the weight of the foot during swing phase as a mens of enhancing swing limb clearance (not for stability)
- Assist with controlled lowering of foot during LR in stance as part of 1st heel rocker (so foot doesnt drop into PF)
- peripheral nerve injury: foot drop
Solid AFO
- resist plantarflexion during swing phase
- larger trim lines allow fot more control of tibia
- support of calcaneus
- wider control of foot plate: prevents excessive eversion and inversion
Static AFO
- rigid AFO to hold ankle and foot in as close to neutral position
- medial and lateral corrugations to provide additional strength when hypertonicity or excessive weight creates loading forces that require a stronger orthosis
Solid AFO disadvantage*
- interferes w/transitions through all 3 rockers of gait in stance phase
- prevents controlled lowering of foot in LR
- especially if set to a few degrees of DF to minimize risk of knee hyperext in early stance
- Anterior stapping with fixed ankle postion prevent forward progression of tibia over WB foot during 2nd ankle rocker in midstance
