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Management of Special Populations > Pathologic Gait & Orthotic Management: Ankle Foot Orthoses > Flashcards

Pathologic Gait & Orthotic Management: Ankle Foot Orthoses Flashcards

1
Q

What are the 4 basic functions of normal gait

A
  • Weight bearing stability
  • Stance limb progression
  • Shock absorption
  • Energy conservation
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2
Q

What happens to alignment when the knee is slightly flexed

A
  • Body weight vector falls slightly behind knee, anterior to hip, & through the ankle
  • Now requiring active contraction of hip extensors, knee extensors, & ankle plantar flexers to stay upright
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3
Q

Describe normal gait according to Elaine Owen

A
  • The shank is not vertical at midstance
  • There is no place in the gait cycle when both the shank & thigh are vertical
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4
Q

Describe causes of the shank being vertical to the ankle during midstance

A
  • 10-12º inclined position of the shank places the knee joint center over the center of the foot during mid-stance
  • Creates a stable distal support mechanism
  • Angular velocity of the thigh increases at the time that the angular velocity of the shank decreases
  • Stability in stance is one of the 5 attributes of normal walking & is vital in MST
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5
Q

What dictates proximal segment kinematics & GRF (ground reaction force) alignment

A
  • Shank kinematics
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6
Q

What are the different rockers during stance

A
  • Heel: initial contact and loading response
  • Ankle: mid stance
  • Forefoot: terminal stance
  • Toe: terminal stance
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7
Q

What are the critical events during stance

A
  • Loading: heel rocker forward progression of body onto foot, shock absorption
  • Single limb stance: tibial stability, ankle rocker, progression of passenger unit in front of foot over stable tibia
  • Critical players in stance: tibia & ankle
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8
Q

What are the critical tasks during stance at the ankle

A
  • Stance: to provide a stable tibia over which the passenger unit can progress
  • Muscle activity: 2 groups of muscles act at the ankle during stance -> pretibials during loading & plantar flexors during SLS
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9
Q

What are the critical tasks during stance at the knee

A
  • Stance: secondary shock absorber during loading as we transfer weight onto the stance limb
  • Muscle activity: after initial activity during loading, quads are quiet during stance
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10
Q

What are the critical tasks during stance at the hip

A
  • During loading: provide stability for the passenger until body vector aligns for stability (mid stance)
  • Muscle activity: hip extensors active during loading; after loading (given proper alignment), hip extensors are quiet, hip ABD active
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11
Q

What are the critical events of the swing phases

A
  • Initial swing: knee flexion to clear a slightly PF foot with thigh flexion to advance limb forward
  • Mid swing: hip flexion continues, with knee starting to extend
  • Terminal swing: knee extension creates step length & prepares limb for heel contact
  • Knee & hip are main players
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12
Q

Common characteristics of hemiplegic gait

A
  • Poor control of flexor muscles during swing
  • Spasticity of extensor muscles
  • Equinovarus deformity
  • Abnormal initial contact onto lateral edge of foot/forefoot
  • Stiff knee that hyperextends
  • Contralateral step meets the position of the paralyzed limb instead of advancing normally
  • Absent rhythmic reciprocal swing of arm with stance phase
  • Pt may drag toe of the affected leg during swing or adopt abnormal movements to clear limb
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13
Q

Characteristics of a slow extender walker

A
  • AKA circumduction
  • ~11% normal walking speed
  • Quads too weak to support the knee during stance
  • Glute Max retracts femur into knee hyperextension for stance limb support
  • Ankle OF spasticity
  • Hip hike & circumduction occur for foot clearance
  • Usually require an assistive device (AD)
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14
Q

Characteristics of a moderate walker

A
  • ~21% normal walking speed
  • Weakness of PF
  • Weakness in hip extensors (glute max) & knee extensors (quads)
  • Greater knee flexion in mid stance
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15
Q

What are we trying to improve in post-stroke gait

A
  • Biomechanics: consider long term viability of gait pattern (risk of overuse injury)
  • Energetics (efficiency vs energy cost)
  • Endurance
  • Speed
  • Independence
  • Safety
  • Level of Physical Activity
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16
Q

What are the main functions of an AFO for foot drop

A
  • Provide moderate resistance during loading response to prevent foot drop: AFOs assist eccentric contraction of the DF during loading response
  • Allow free dF in stance
  • Provide large resistance in swing to inhibit foot drop
  • Assist push-off function by providing PF moment
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17
Q

What are the Rancho ROADMAP pre-requisites for AFOs

A
  • Sufficient ROM in LE joints to align segments
  • Ability (including cognition) & desire to meet ambulation goals
  • Adequate cardiovascular endurance & adequate UE & LE strength for the intended activity
  • Sufficient strength to advance the limb
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18
Q

What are the effects of AFOs on motion control

A
  • Foot relative to tibia
  • Tibia relative to foot
  • Ankle joint: achieved by stopping, assisting, or resisting various ankle joint motions
  • Subtalar joint
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19
Q

What motions does an AFO influence

A
  • Knee & hip joints
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20
Q

What AFOs have a fixed ankle position

A
  • Rigid polypropelyne AFO
  • Metal AFO with double adjustable ankle joint (DAAJ) & poly footplate, locked
  • Metal AFO with DAAJ, locked
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21
Q

Describe a double action ankle joint

A
  • Anterior compartment: a pin is utilized to control tibial advancement (DF stop0 in stance for a knee extension moment at heel off
  • Posterior compartment: either a spring or pin is effective to aid in foot clearance during swing; pin limits PF (stop) and spring limits PF through a DF assist
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22
Q

Describe the mechanics of a solid ankle AFO (SAFO)

A
  • PF stop ad DF stop
  • Influences knee stability
  • Triplanar control is based on trim lines (if plastic)
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23
Q

Indications for a SAFO

A
  • Weakness of dorsiflexors and plantarflexors
  • Quadriceps weakness
  • Excessive ankle/foot pronation
  • Helps restore normal stance phase shank and knee kinematics
24
Q

Contraindications for a SAFO

A
  • Isolated swing phase deficits without stance phase deficits
  • Isolated dorsiflexor weakness
  • If there is sufficient plantarflexor length AND strength to allow free dorsiflexion and still achieve maximum knee extension at mid-stance and a stiff ankle in late stance
25
Q

How will a SAFO impact progression through stance phase of gait

A
  • Biomechanically interferes with transitions through all 3 rockers of gait in stance phase bc of the fixed ankle position inherent in the design
  • Prevents controlled lowering of the foot that usually occurs in the ankle/1st rocker
26
Q

What AFOs have a dorsiflexion stop

A
  • Polyarticulating AFO with DF stop
  • Metal AFO with DAAJ & poly footplate, DF stop
  • Metal AFO with DAAJ, DF stop
27
Q

Describe a DF stop/free PF

A
  • Use of an articulating (joint) & a “stop” to permit only one of the sagittal plane motions
  • Facilitates knee extension & stiff ankle in late stance
28
Q

Indications for a limited motion articulated ankle DF stop/free pf

A
  • Weakness of the PF
  • Weakness of the quads
29
Q

Contraindications for a limited motion articulated ankle DF stop/free pf

A
  • DF weakness
  • Knee hyperextension
30
Q

Which rocker of gait would be most affected by an AFO with DF stop

A
  • 3rd rocker
31
Q

How could the AFO/footwear combination be modified to help normalize 3rd rocker?

A
  • Rocker sole
  • Rounded toe rocker vs point loading toe rocker
32
Q

What AFOs have a dorsiflexion assist (primarily for swing limb clearance)

A
  • Leaf spring AFO
  • Polyarticulating AFO with DF assist
  • Metal AFO with DAAJ & poly footplate, DF assist
  • Metal AFO with DAAJ, DF assist (spring in posterior channel)
33
Q

Describe the mechanics of a DF assist AFO

A
  • Assists with toe clearance during swing
  • Allows for controlled foot flat from initial contact to loading response
34
Q

What are the indications and contraindications of a DF assist AFO

A
  • Indications: DF weakness
  • Contraindications: abnormal shank & knee kinematics; moderate to severe tone/spasticity
35
Q

Describe the mechanics of a posterior leaf spring DF assist AFO

A
  • Least bulky
  • Provides some dF assist but limits PF
36
Q

Indications & contraindications for a posterior leaf spring DF assist AFO

A
  • Indications: DF weakness with minimal need to control stance phase kinematics; Primarily facilitate swing limb clearance
  • Contraindications: need to control stance kinematics, medial/lateral ankle instability, knee instability, & moderate to severe tone/spasticity
37
Q

What AFOs have a plantar flexion stop (helps with swing limb clearance & decreasing knee hyperextension in early stance)

A
  • Polyarticulating AFO with PF stop
  • Metal AFO with DAAJ & poly footplate, Pf stop
  • Metal AFO with DAAJ, PF stop
38
Q

Describe the mechanics of a PF stop AFO

A
  • Usually a limited. motion articulated ankle joint allowing ankle DF
  • Facilitates knee flexion in early stance
39
Q

Indications for a PF stop AFO

A
  • DF weakness
  • Knee hyperextension in early stance (reclined shank)
40
Q

Contraindications for a PF stop AFO

A
  • Weak quads
  • Gastroc spasticity
  • Insufficient PF length & strength to allow free DF and achieve maximum knee extension at mid stance & stiff ankle in late stance
41
Q

Is there anything that we could do to modify the AFO footwear combination to restore 1st rocker with a PF stop

A
  • Cushion heel
  • Rocker heel
42
Q

Describe the mechanics of a ground reaction AFO (GRAFO)

A
  • Rigid section over anterior proximal tibia provides an external extension moment at the knee
  • Provides additional knee stability in late stance phase
  • Often an attempt to avoid going towards long leg bracing
43
Q

Indications for a GRAFO

A
  • DF weakness
  • PF weakness
  • Quad weakness
44
Q

Contraindications for a GRAFO

A
  • If “less” control will suffice
  • Knee hyperextension
  • For prefabricated designs: any frontal/transverse plane ankle instability and/or if ankle angle other than 90º is required
45
Q

What happens if your AFO is too stiff

A
  • AFO will resist ankle PF at initial contact phase of gait & cause abrupt forward rotation of the tibia at initial contact causing the knee to be pushed forward, thereby increasing knee flexion at early stance & inducing gait instability
46
Q

What happens if your AFO is less stiff

A
  • PF resistive moment will not be sufficient to prevent the foot slapping of keep clearance during swing
47
Q

CPG for use of AFO and FES post stroke

A
  • An AFO customized to the individual is BEST
  • An AFO may be better for slower walkers, FES for faster walkers
  • More meaningful improvements observed when AFO/FES combined with skilled PT
  • Consistent reassessments needed to meet changing needs
  • AFO provision early in recovery enhances participation & leads to faster progress towards goals
  • Wearing an AFO does NOT hinder muscle activation
  • FES can improve muscle activation through a therapeutic effect
  • No evidence that AFO or FES can decrease PF spasticity
  • AFO that allows PF motion may lead to greater effects on gait speed
48
Q

What should you consider when thinking about using an AFO on a patient

A
  • Applying an AFO to someone who is dragging their foot will not necessarily improve limb clearance
  • The primary benefit of the foot being at neutral is positioning the foot for heel contact in loading
49
Q

Common deviations that go together during single limb stance (SLS)

A
  • Excessive DF: increased knee flexion & hip flexion
  • Excessive PF: knee hyperextension or extension thrust, forward lean at trunk, & backward rotation of pelvis
50
Q

What is the mostly likely cause of excessive ankle DF in stance

A
  • Weakness of plantar flexors not quads
  • Most noticeable deviation to naked eye is walking in knee flexion
51
Q

What is the solution to excessive ankle DF in stance

A
  • AFO with a DF stop will prevent tibia from collapsing into DF, hence controlling the tibia & the alignment further up the chain
  • The more you PF the AFO the more it will straighten the knee
52
Q

Potential causes of extension thrust or hyperextension in loading response

A
  • Forefoot contact (PF tone or contracture)
  • Weak quads
  • Quad tone
  • Absent/impaired proprioception at knee 7 ankle
  • Intentional to maintain limb stability
53
Q

Potential causes of extension thrust or hyperextension in single limb support (SLS)

A
  • Excessive PF: either due to lack of adequate DF ROM or PF tone
  • Intentional to maintain limb stability in the absence of quads (polio)
54
Q

What is the solution to excessive ankle PF in stance

A
  • Dorsiflexing an AFO you can cause a plantar flexion stop, slowing the extensor thrust
  • Can only be achieved with a PF stop AFO, either rigid or open DF
55
Q

Possible causes of a step to gait (decreased stance limb stability) and solution

A
  • cause: short step is due to the stance instability on the opposite side or not enough DF ROM
  • Solution: AFO with either DF stop or locked ankle (fix the stance instability then step length increases)
56
Q

Possible causes of increased double limb support time

A
  • Patient has extremely shortened swing
  • Instability on one or both sides
  • Not enough DF ROM & instability to progress HAT (head, arms, & trunk) over the foot
57
Q

Solution for increased double limb support time

A
  • Provide tibial stability with DF stop
  • DF/PF stop rigid AFO
  • Compensate for lack of DF ROM

Management of Special Populations (13 decks)

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