L2: AFOs Flashcards
When we refer to “Traditional” orthotic
Whats that mean
Metal bars and leather
Old School!!!!!
Orthotics always go one joint above what you want to control
******
Rockers:
3
- Heel
- Ankle
- Toe (Forefoot)
Rockers:
Heel
- IC→Foot flat
- DEceleration of foot→floor
- Wt Acceptance
Rockers:
Ankle
- MSt as tibia advances over fixed foot
- Triceps surae eccentrically controls speed of tibia (decelerates)
Rockers:
Toe (Forefoot)
- Tst→ Push-off
- BW rolls over MTP jts
AFO Terminology
NOTE: trimlines, straps, footplates
AFOs
Goals and Gait Prereqs:
-
Goal:
- Safe, energy efficient gait
-
Gait Prereqs:
- Stability in stance
- Swing phase prepositioning
- Clearance in swing
- Adequate (symmetrical) step length
- Energy conservation
Note about step length involved vs uninvolved
Involved LE will CAUSE shorter step length on contralateral side (good side)
AFOs
Stability in Stance
- AFO controls instability by optimally aligning ankle
- application and loc of forces in M/L or A/P directions
- Ideal for pes equinus or ankle vaRus deforms
AFOs
Stability in Stance
Fulcrum vs Counter Forces
- Fulcrum→ Anterior ankle
- Counter forces→ Plantar surf foot and posterior proximal calf
AFO
Clearance in Swing
- Keeps foot neutral==incd qual of swing due to:
- Dec DF strength
- poor timing
- abnorm EXT synergy
AFO
Swing Phase Repositioning
- Maintains ankle in neutral DF and ev/inv to prep for wt acceptance
AFO
Adequate Step Length
- Maints stability of talocrurcal joint in TSt and PSw→ allows CONTRALAT. LIMB to maint. proper step length
- effective propulsion of limb in Sw when needed
AFO
Energy Conservation
*CRITICAL in neuro pop.
- Critical neuro pop→ return to IND community amb.
- Controls ankle and knee jts during St and Sw===Less energy cost
- *Less compensatory mechs==Less energy !!!
PF + DF associations
Excess PF== Knee EXT (PE class**)
Excess DF== Knee FLEX (buckling)
AFO
*rigid solid ankle AFO that fixes ankle in DF prevents
Knee HyperEXT
AFO-Force Systems
What all AFO’s do inherently
- Notice where Fc is and what is being controlled!!!
- Fp= proximal force
- Fd= distal force
AFO force system
PF control
NOTE: Fprimary
AFO controlling excessive PROnation
notice Medial flange
MOST AFOs are ________
Custom Molded (MAFOs)
MAFOs
Custom Molded
- Intimate fit, light, distributes forces effectively, fits most shoes, modified for relief,
- Does NOT accommodate for fluctuating edema ***
AFO Types: 2
Classified by function
-
Static Ankle Foot Orthosis
- MAX control
-
Dynamic Ankle Foot Orthosis
- Incs DOF→ someone w/ better control
Static AFO’s
4:
- Solid Ankle
- Anterior Floor Reaction
- set in PF→ knee hyperEXT bias
- Patella Tendon Bearing
- Supramalleolar (SMO)
- high top→ PEDS
Dynamic AFOs (DAFO)
4:
- Posterior Leaf Spring (PLS) (Thermoplastic)
- Conventional DF assist
- Articulating thermoplastic
- Hybrid (metal-plastic)
AFOs ex’s
see pics
Static AFO’s (max control)
Primary function
- maint. ankle/foot in a fixed pos. @ TCJ, STJ, forefoot
-
Effectively:
- assist w/ Sw clearance
- preposition foot for IC
- EXT stability for knee & ankle t/o stance
Static AFO
Solid (non-articulated) ankle AFO
Drawbacks and what to do about it
- Drawback→ all rockers compromised
-
AFO fabrication→ Shoe mods:
- Inc cushion heel→ compensates for heel rocker
- Rocker bottom (entire sole)→ comps for 2nd/3rd rockers=== smooth forward translation t/o Stance
Solid Ankle AFO:
Indications
- Those who need total immob. of ankle/foot complex
-
Controls:
- Inv/Ev
- foot drop (but not all need MAFO)
- Ext tone/synergies→ Mod Ashworth know it!!
- Knee hyperFLEX (biases to PF)/knee hyperEXT (biases to DF) → you know WHY!!
Solid Ankle AFO
Thermoplastic piece
- Thermoplastic piece encompasses most of lower leg
- Trimlines→ anterior to malleoli
Solid Ankle AFO
To control for abnorm toe grasp (CP, spastic CVAs):
LONGER toe/footplate
Tone inhibiting bar
Static AFOs w/ articulation have ability to max. control:
4 things:
- Ankle DF/PF
- Inv/Ev
- Knee hyperEXT
- Knee buckling (hyperFLEX)
Static AFOs w/ articulation have ability to max. control:
Ankle DF/PF
HOW?
- A/P force coupling→ 3pt system
- Length of foot plate
- Thickness of foot plate
Static AFO’s w/ articulation have ability to max. control:
Inv/Ev
HOW?
- Med→Lat force coupling
- Ankle/foot trimlines**
Static AFOs w/ articulation have ability to max. control:
Knee hyperEXT
HOW?
Ankle/foot set in slight DF
bc DF associated w/ FLEXION**
Static AFOs w/ articulation have ability to max. control
Knee Buckling (hyperFLEX)
HOW?
Ankle/foot set in slight PF
bc PF assoc’d w/ EXTENSION***
Static AFO:
Anterior Floor Reaction
*protects against buckling
- Harnesses GR moment/force (GRF) and converts into sagittal plane stability for the knee jt during stance
-
*Set in slight PF to create EXT moment @ knee
- → Bias towards keeping knee in EXT→ controls knee buckling/flex
Anterior Floor Reaction
More on PF role and setting:
- Amt of PF, rigidity, length of toe plate== degree of knee control
- PF-knee EXT force couple
- padded anterior shell @ prox anterior tibia→ absorbs EXT moment
Anterior Floor Reaction
What is actually happening when set in neutral or slight PF
- Tibia restrained from advancing over fixed foot→ 2nd rocker
- GRF anterior to knee earlier in St==more knee EXT force
- Length+stiffness of toe plate INCs==3rd rocker limtd → biases knee into EXT
Anterior Floor Reaction + Ground Reaction Moments
Anterior Floor Reaction AFO
Biomechanically, what does it do?
Indicated for based off of that?
Enables pt w/ little quad function to be stable t/o stance phase
-
Indications:
- Weak quads→ remember quads have to counter knee flexion moment****
- Crouched gait→ bc will lessen demand on quads by moving GRF anterior to knee sooner
Anterior Floor Reaction AFO
Based off what you know biomechanically….
NOT indicated for:
-
Not indicated:
- Uncontrolled genu recurvatum
- bc already hyperEXTd
- Structural knee instab. (ligs)
- Knee flex contracture >10*
- AFR AFO will still control DF and knee flex, but will not create true EXT moment
- Uncontrolled genu recurvatum
Anterior Floor Reaction AFO stops/limits…
DF
*bc remember DF assoc’d w/ knee flex which could = buckling!!!
AFR AFO depicted in picture form…
see pics read description!!!!
The AFO w/ the “Knee pad” looking thing
Patella Tendon Bearing “PTB” AFO
PTB AFO
Primary goal:
- Reduce axial loading to the knee, foot, ankle
PTB AFO
HOW does the PTB AFO reduce axial loading to knee, foot, ankle?
- Set in slight knee flex (10*)
- BW loaded onto anterior shell + patella tendon
- ==> DECd loads on tib, fib and bones of foot***
- BW loaded onto anterior shell + patella tendon
PTB AFO
EXCELLENT OPTION for…
- anyone who reqs reduced WB thru foot:
- CMT ankles
- Neuropathic ulcers on plantar surface
- slowly healing fx’s of foot
PTB AFO pics
see pics
Supramalleolar Orthotic (SMO)
Biomechanical function:
- Incs control of STJ valGus and vaRus by lengthening proximal lever arm upward
- Think “high-top sneaker”
SMO
Based off biomechanic function….
Indications:
- CP after corrective sx→ tendon lengthening
- Chronic INV instab.→ STJ trauma
- Periph neuropathy
- MM disease
- Pts w/ adequate knee strength/control
- ***SMO won’t correct knee!!!!
Static AFOs prevent DF/PF ankle mvmts necessary to perform functional activities efficiently
see pics and notice compensations
see pics
Posterior Leaf Spring (PLS)→ Dynamic AFO
*2 things to remember:
- Narrow trimline
- MORE intrinsic mobility of foot
Posterior Leaf Spring PLS→ Dynamic AFO
ALL Dynamic AFOs allow this:
Sagittal plane motions @ ankle***
PLS Distinction from all dynamic AFOs
- Trim lines well behind med/lat malleoli==> more flexibility
- *Thickness of thermoplastic==> determines flexibility
PLS and the Rocker Systems
1st→3rd
-
1st Rocker
- PLS provides controlled lowering of foot toward ground
-
2nd Rocker
- Flexibility of PLS allows enough DF for tibial advance. over foot in MSt
-
3rd Rocker (PSw) and Sw
- PLS hold ankle @ 90* (neutral)→ assists w/ clearance + pos’ing for next heel strike
PLS trades _____ for _______
PLS trades stability for mobility
Drawbacks of PLS
- DECd mediolateral control
- DECd knee control
- not structured to control knee
- NOT effective w/ mod-severe spasticity
- they’ll burst right thru it
PLS trades stability for mobility
Spiral AFOs
*Semirigid plastic
- During stance→ Uncurls (widens) as limb accepts wt
- MSt→ ankle comes to neutral→ returns to orig. shape
- MSt-TSt→ sprial compresses (like coiled spring)→ aids in push-off as ankle DFs
- Swing→ spiral returns to orig shape to hold foot in neutral
Only difference bw Spiral AFO vs. HemiSpiral AFO
Hemi employs same mechanics w/ slightly greater control of Pes Varus (supination)***
Hemi-Spiral AFOs
- Same mechanics as spiral BUT→ slightly greater control of pes varus (supination)
- No fasteners, light wt.
- Intimate fit→ NOT for edetamous limbs
-
Mod control of foot and ankle
- trimline ht and thickness thermoplastic
Spiral and hemi-spiral AFOs
Ex’s
Conventional AFO→ Dynamic AFO
aka
Metal uprights w/ leather
Conventional AFO→ Dynamic AFO
Ankle control
- Ankle control w/ stops and assists
- Biochannel adjustable ankle lock (BiCAAL) vs single channel joint
-
Ankle stops named for motion they RESTRICT**
- DF stop or PF stop
-
Most common→ 0* PF stop (stops unwanted PF)
- useful to clear foot during Sw
Conventional AFO
More on Ankle Stops
What stop would be useful for controlling knee buckling (excess. flexion) from LR→MSt?
DF Stop
*Bc excess DF assoc’d w/ excess Knee Flexion (buckling)
Conventional AFO (double upright AFO) w/ Jt Controls
Bichannel (2 channels) adjustable ankle lock (BiCAAL)
Conventional AFO
DF Assist
- MOST Common→ Spring mech. incorp’d into mech. ankle jt to assist DF***
- Mech. that produces force to aid in desired jt motion
- Compressed during late stance and recoils during Swing
- To ADD/DEC DF assist:
- tighten/loosen screw adding tension to spring***
Conventional AFO-DF Assist
-
Approp for→ gross DF strength defs
- peroneal N. palsy, CMT
- DF assist/PLS not ideal→ those w/ hypERtonicity and neuromotor equinovaRus
- >>> option for fluctuating edema
-
Drawbacks→
- incd wt.
- dec surf area
- min→none M/L stability
Conventional AFO w/ Calcaneal VaRus/ValGus Control Strap
- Named for where the wider, non-buckle side of strap is (see pics)
- LATERAL strap→ CORRECTS calcaneal vaRus (subtalar INversion)
- MEDIAL strap→ CORRECTS calcaneal vaLGus (subtalar EVersion)
Conventional AFO w/ calcaneal varus/valgus control strap
*named for side where BIG lg surface area part of strap is!!! see pic for example slide 50
LATERAL STRAP
- L→M force
- Corrects calcaneal vaRus or subtalar INversion
Conventional AFO w/ calcaneal varus/valgus control strap
*named for side where BIG lg surface area part of strap is!!! see pic for example
MEDIAL STRAP
- M→L force
- Corrects calcaneal valGus or subtalar EVersion
Articulating (hinged) Thermoplastic AFO
*NOTE: person must have how much active DF to be able to use?
5* active DF
Articulating (hinged) thermoplastic AFO
- bw foot/calf
- 5* active DF needed***
- Effective how?→ adding PF stop mechanism (usually @ 90*)
One of the Goals w/ Orthotics
Wear least amt of extrinsic stuff while controlling as much as we can****
Articulating Thermoplastic AFO
Benefits of the hinge mech.
- Easy progress thru 1st/2nd rockers
- Controls knee hyperEXT in MSt
- INC mobility
- Energy efficient
Articulated thermoplastic AFOs
Ex’s
A&B→ True single-axis joints
C→ Allows mvmt into DF/PF w/out an actual articulation
Articulated (hinged) thermoplastic AFO
Can have a DF/PF stop T/F?
TRUE!!!!
Hybrid (Plastic→Metal) AFO
Defined:
- Adjustable ankle-locking jt.
- NOT METAL uprights→ thermoplastic instead
Hybrid Plastic-Metal
If you WANT MOTION→
- Coil spring placed in channel + screw tightened d
Hybrid Plastic-Metal
If motion needs to be BLOCKED→
- Solid steel pins inserted instead of spring to stop motion beyond particular point
- NOTE: Can stop PF and allow PF as neuromotor control dictates***
Hybrid Plastic-Metal
- Versatile/adjustable→ easy to work with
-
Indications→
- those who have rapid changes in functional status
Static>>>>Dynamic AFOs
see pics
AFO and shoes
AFO use and benefit interrelated w/ cond/type of shoe***
- INC ½ to 1 shoe size
- Heel hts→ dramatically alter biomechanics or orthotic
-
More stable, solid AFO==> SOFTER heel reqd
- Ex. rocker bottom (bc rockers lost w/ these)
- *PLS loses effectiveness in loafer/slippers
Ex’s AFO
Conventional, MAFO, Articulating
see pics
Take Home Messages
AFO’s
- Must be comfortable
- Must look good
- Thermoplastic==MOST COMMON
- AFO should provide support for stability in stance AND clearance in Swing WITHOUT COMPROMISING rocker systems