Stance phase - heel rocker
- begins at initial contact and ends at foot flat
- occurs during loading response when ankle PF and knee extensors are working eccentrically
Stance phase - ankle rocker
- tibia advances over ankle-foot complex during midstance
- ankle PF are working eccentrically to control tibial progression
Lack of ankle DF leads to
-either a shorter step or turning the foot out so we don’t have to step over it
Stance phase - forefoot (toe) rocker
-begins as the heel rises off the ground until push-off
AFOs and “rockers”
-AFOs change the rockers altering gait
6 purposes of an AFO
- prevent foot drop
- provide pre-positioning in swing phase
- provide M/L control in stance
- prevent excessive pronation/supination
- decrease knee flexion in stance
- prevent knee hyperextension in stance
DF stop
- rod in anterior chamber
- assists weak ankle PF (limits tibial progression during midstance and may help control knee in sagittal plane when there are weak quads)
- restraint of tibial progression places vertical ground reaction force anterior to the knee - produces external knee extension moment
DF assist
- spring in posterior chamber
- serves to bring ankle joint through DF during swing phase
- allows PF range of motion at loading response, which decreases knee flexion moment, which may de-stabilize the knee
- the spring loads during plantarflexion and then releases energy to assist with DF
PF stop
- rod in posterior chamber
- assists with clearing toes during swing phase due to inadequate ankle DF strength
- limits ankle PF range
- may affect heel rocker because you need PF to complete
Tibia-to-floor angle - tibia placed into DF
Tibia-to-floor angle- PF
-tibia placed into slight PF will create a knee extensor moment during loading response and provide stability to the knee joint by placing the ground reaction force anterior to the knee
3 point force systems
- control 2 articulating skeletal segments
- corrective force is located on the convex side of the joint of interest
- 2 counteractive forces are positioned on the opposite side above and below the joint
- increases the distance of the counteractive forces increases their lever arm making them more effective
Review…
diagrams with arrows from the orthotics design and prescription handout
Overview of posterior leaf spring AFO
- designed for foot drop without medial/lateral instability OR excessive tone
- allows some weight bearing DF which “loads” the “spring”
- allows for PF because of the tapering
Pros of posterior leaf spring AFO
- flexible
- doesn’t affect heel rocker (let’s you PF)
- provides an ankle rocker (allows push-off)
- holds in neutral when off ground
- very minimal bracing
Cons of posterior leaf spring AFO
- need ankle stability to use
- not for severe tone
- doesn’t control or grade PF at heel strike
To use posterior leaf spring with tone
-have a metatarsal bar or inhibiting footplate added (aggravated in midstance - ankle rocker)
Solid ankle AFO overview
- trim line prevents all motions at the ankle
- increased stability prevents knee collapse (either hyperflexion or hyperextension)
Pros of solid ankle AFO
- lightweight
- customized fit
- good support
- adjustable
- even skin contact
- helps knee instability
- decreases tone - maintains stretch
- blocks PF
- prevents foot drop
- provides M/L stability
Cons of solid ankle AFO
- not going to help ROM
- so much stability
- muscles not taxed
- fixed volume
- requires roomy shoe
- must be monitored for changes in patient limb size
Modifications that can be made to a solid ankle AFO
- added heel rocker
- put in more or less PF/DF depending on pt
- shave or add padding when increased pressure
Dual channel ankle joint (articulating AFO) - posterior chamber with spring
- allows for controlled DF during loading response (compression of spring)
- recoil of spring when foot is unloaded assists DF during initial swing
Articulating AFO - posterior chamber with pin
-limits PF ROM - PF stop
Articulating AFO - anterior chamber with spring
- allows for control DF during midstance (ankle rocker)
- assists ankle PF during push off
