Lower limb orthotics

Jeff Ericksen, MDVCU/MCV Dept. of PM&R

Goals

Gait reviewKey muscles, joint mechanics

Common conditions for orthoticsLower limb orthotic approachExamples

Normal gait = progression of passenger unit through space with stability and minimal energy output.*

Keep center of gravity in tightest spiralMost efficient CG path = line, only with

wheels Perry, J Atlas of Orthotics

InitialContact

LoadingResponse

MidStance

TerminalStance

Pre-Swing

InitialSwing

Mid-Swing

TerminalSwing

Weight Acceptance Single Limb Support Limb Advancement

Stance Phase Swing Phase

Terminology

Gait Cycle: Sequence of events from initial contact of one extremity to the subsequent initial contact on the same side

Gait terminology

Stride length: Distance from initial contact of one extremity to the subsequent initial contact on the same side (x= 1.41 m)

Step length: Distance from initial contact of one extremity to the initial contact on the opposite side (x= 0.7 m)

Terminology

Cadence: The step rate per minute (x= 113 steps per min)

Velocity: The speed at which one walks

(x= 82 m/min)

Normal Gait

Classic Gait Terms:1) Heel Strike2) Foot Flat3) Midstance4) Heel Off5) Toe Off6) Initial Swing/ Midswing/ Terminal Swing

Gait Events

Phases: 1) Stance Phase: 60% 2) Swing Phase: 40%Periods: 1) Weight Acceptance 2) Single Limb Support 3) Limb Advancement

Gait Events (Perry)

1. Initial Contact2. Loading Response3. Mid Stance4. Terminal Stance5. Pre-Swing6. Initial Swing7. Mid Swing8. Terminal Swing

Progression

Mostly from forward fall of body mass as it progresses in front of loaded foot, ankle moves into DF with rapid acceleration as heel rises

Swing limb generates second progressional force as stance limb goes into single support phase, must occur to prepare for forward fall

Energy consumption

Acceleration & deceleration needsSwinging mass of leg must be

decelerated by eccentric contraction of extensors and counterforce (acceleration) of body

Forward falling body must be decelerated by shock absorption at initial contact = heel strike

Eccentric energy consumption is high

Pretibial and quadriceps contraction at initial contact with eccentric control of tibial shank in loading phase on stance leg.

Results in 8:5 ratio for energy in deceleration or control activity vs. propulsion activity

Determinants of gait

Foot, ankle, knee and pelvis contributions to smoothing center of gravity motion to preserve energyInman APMR 67

Determinants

1) Pelvic Rotation2) Pelvic Tilt3) Lateral pelvic motion4) Knee flexion in midstance5) Knee motion throughout gait

cycle6) Foot and ankle motion

Determinants Pelvic rotation 4

degrees saves 6/16 vertical drop

Pelvic tilt 5 degrees, saves 3/16 vertical excursion

Knee flexion 15 degrees lowers CG 7/16total savings = 1 inch

per leg

Foot & ankle motionSmooths out abrupt

changes in accel/decel & direction of body motion Knee contributes also

Converts CG curve into smooth sine wave < 2 inch amplitude

CG horizontal translation reduced by leg alignmentreduces side to side

sway for stability by > 4 inches

Muscle activity in gait cycle*

Muscle activity*

Energy costs and gait*

Forearm crutch use

Normal subjects

Joint stability in gait

Determined by relationship between muscle support, capsule & ligamentous support, articular relationships and lines of force

Gait deviations

Structural bony issuesJoint/soft tissue changesNeuromuscular functional changes

Leg length difference < 1.5 in, see long side shoulder

elevation with dipping on short leg sideCompensation with dropping pelvis on

short sideExaggerated hip, knee, ankle flexion on

long side > 1.5 in, different compensation

such as vaulting on short leg, trunk lean to short side, circumduct long leg

ROM loss or ankylosis will show proximal

compensation with or without velocity changes.

Other orthopedic problems affect gait*

Foot equinus gives steppage gait to clear the relatively longer leg

Calcaneal deformity changes push off and initial contact

Gait changes from orthopedic issues

Joint instability gives unstable motion and fear, reduced stance phase

Pain reduces stance typicallySpine pain may reduce gait speed to

reduce impact

Hemiplegia gaits

Extensor synergy allows ambulationHip & knee extension, hip IR, foot &

toe PF and foot inversionDifficulty in loading phase or

clearing the “longer” plegic limb gives step-to gait.

Hemiplegia

1) Asymmetric Gait2) Step length shortened on the plegic side3) Decreased knee and hip flexion on swing phase4) Shortened stance phase5) Upper extremity held in flexion and adduction

Lower motor neuron gaitsHip extensor weakness gait

Trunk & pelvis posterior after heel strike

Glut medius limppelvis drops if uncompensatedtrunk shift if compensated

Hip flexor weaknessLeg swung by trunk rotation pulling

leg on hip ligaments

Lower motor neuron gaitsQuadricep weakness: forcible

extension using hip flexors, heavy heel strike and forward lean over heel to keep force anterior to knee joint.

Gastroc/soleus weakness: poor control of loading phase DF >> compensation is delay with resulting knee bending moment and more quad extensor needs. Reduced forward progression of limb with push off into swing*

Lower motor neuron gaits

Dorsiflexor weakness gives steppage gaitFoot slap in fast walk with mild

weakness and if some strength, may be noticable with fatigue as eccentric TA activity fails

Forefoot = initial contact point if no strength for DF present

LE Orthotics

WeaknessSkeletal & joint insufficiency

Leg joint alignment orthoses

Use with & without weight bearing features

Most common in knee support for RA induced ligamentous loss

Form fitting shells better than bands

Alignment of knee joint is keyTypically use single axis knee joints for

these orthoses

LE weakness orthoses

AFO’sDouble metal

uprightPlastic

Molded off shelf

VAPC

KAFO’s Many designs for

band configurations

Metal vs. plastic

HKAFO’sReciprocating

Gait OrthosisFunctional

Electrical Stimulation (FES)

AFO’s

Most common orthoticStabilizes ankle in stanceHelps clear toe in swingGives some push off in late stance

to save energyRemember effects on knee!!

AFO’s

Double metal upright allows for anterior and posterior stops and spring assist for DF & PF force generation.Hinged molded AFO can be similar

Mediolateral stability is good but can be enhanced with T-straps

Knee effects of PF stops

PF stop helps weak DF & swing clearance but stops PF of foot at heel strike, force line behind knee destabilizes.Minimal PF stop or just spring assist

to pick toe up in swing should be used for flaccid paralysis and only few degrees of DF position for PF stop in spastic paralysis.

Posterior PF stop should allow adequate toe

clearance in swing but not excessive DF to increase knee bending moment at

heel strike.

Contact & loading phase knee effects of AFO’s

Heel adjustments can help knee*

Effects of DF stopsAnterior DF stop (plus sole plate in shoe)

enables push off and propulsion of limb and pelvisNormal forces if DF stop in 5o PFUse for PF weakness, restores step length on

opposite side and knee moments normalize.Spring doesn’t helpToo much PF angle gives genu recurvatumStabilizes knee with absent gastroc/soleus

eccentric knee extension help in stance

Push off knee effects of AFO’s

Single upright orthoses

Reduces interference with contralateral orthoses or medial malleolus

Not useful for mediolateral stability problems

Plastic AFO’s

Similar biomechanical analysisTrim lines of posterior vertical

component influence ankle rigidity

Plastic AFO components

Plastic AFO considerationsLight weightVariable shoes can effect

performanceSkin irritation very real risk

Contraindicated in diabetic neuropathy or poorly compliant patient with skin checks

Minimal help for PF weakness, mostly for DF weakness

Can help with arch support

VAPC dorsiflexion assist orthosis

Knee orthoses

Commonly used for genu recurvatumSwedish knee cage3 way knee stabilizer

Medial/lateral laxityJoint system with thigh & calf cuffs

Axial derotation bracesAxial rotation control plus angular

control in sagittal and frontal planes

Knee extension control

Knee locks

KAFO’s used in SCI, conus or cauda equina injuries

T10 is often cutoff level, use swing to gait with locked knees, considerable energy expenditure

Knee stability added when AFO not able to control

kneeContinue to utilize rigid foot plate

and DF stop to help push off and PF stop to clear toe in swing

Knee stability via 3 force application

Anterior force to stop knee buckling

2 posterior counterforces at thigh & 1 at calf

Shoe level counterforce keeps lower leg from posterior motion in closed chain loading

HKAFO’s

Rarely used, indicated for hip extensor weakness

Pelvic band often necessary for stabilization and suspension

Hip orthotics for dislocation risks

AdultsPediatrics

Scottish RitePavlik Harness

Reciprocation Gait Orthosis

Releasable hip joint & knee joint for sitting

Cable coupling of hip flexion to contralateral hip extension

Questions