Lower limb orthotics  Jeff Ericksen, MD  VCU/MCV Dept. of PM&R

Goals  Gait review  Key muscles, joint mechanics  Common conditions for orthotics  Lower limb orthotic approach  Examples

Normal gait = progression of passenger unit through space with stability and minimal energy output.*  Keep center of gravity in tightest spiral  Most efficient CG path = line, only with wheels  Perry, J Atlas of Orthotics

Initial Contact Loading Response Mid Stance Terminal Stance Pre Swing Weight Acceptance Single Limb Support Initial Swing Mid Swing Terminal Swing 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 Strike 2) Foot Flat 3) Midstance 4) Heel Off 5) Toe Off 6) 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

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Gait Events (Perry) Initial Contact Loading Response Mid Stance Terminal Stance Pre-Swing Initial Swing Mid Swing 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 needs  Swinging 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 energy  Inman APMR 67

Determinants 1) Pelvic Rotation 2) Pelvic Tilt 3) Lateral pelvic motion 4) Knee flexion in midstance 5) Knee motion throughout gait cycle 6) 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 7/16  total savings = 1 inch per leg   Foot & ankle motion  Smooths 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 alignment  reduces 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 issues  Joint/soft tissue changes  Neuromuscular functional changes

Leg length difference  < 1.5 in, see long side shoulder elevation with dipping on short leg side  Compensation with dropping pelvis on short side  Exaggerated 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 typically  Spine pain may reduce gait speed to reduce impact

Hemiplegia gaits  Extensor synergy allows ambulation  Hip & knee extension, hip IR, foot & toe PF and foot inversion  Difficulty in loading phase or clearing the “longer” plegic limb gives step-to gait.

Hemiplegia 1) Asymmetric Gait 2) Step length shortened on the plegic side 3) Decreased knee and hip flexion on swing phase 4) Shortened stance phase 5) Upper extremity held in flexion and adduction

Lower motor neuron gaits  Hip extensor weakness gait  Trunk & pelvis posterior after heel strike  Glut medius limp  pelvis drops if uncompensated  trunk shift if compensated  Hip flexor weakness  Leg swung by trunk rotation pulling leg on hip ligaments

Lower motor neuron gaits  Quadricep 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 gait  Foot 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  Weakness  Skeletal & 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 key  Typically use single axis knee joints for these orthoses

LE weakness orthoses   AFO’s  Double metal upright  Plastic  Molded  off shelf  VAPC KAFO’s  Many designs for band configurations  Metal vs. plastic    HKAFO’s Reciprocating Gait Orthosis Functional Electrical Stimulation (FES)

AFO’s  Most common orthotic  Stabilizes ankle in stance  Helps clear toe in swing  Gives some push off in late stance to save energy  Remember 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 stops  Anterior DF stop (plus sole plate in shoe) enables push off and propulsion of limb and pelvis  Normal forces if DF stop in 5 o PF  Use for PF weakness, restores step length on opposite side and knee moments normalize.

 Spring doesn’t help  Too much PF angle gives genu recurvatum  Stabilizes 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 analysis  Trim lines of posterior vertical component influence ankle rigidity

Plastic AFO components

Plastic AFO considerations  Light weight  Variable shoes can effect performance  Skin 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 recurvatum  Swedish knee cage  3 way knee stabilizer  Medial/lateral laxity  Joint system with thigh & calf cuffs  Axial derotation braces  Axial 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 knee  Continue 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  Adults  Pediatrics  Scottish Rite  Pavlik Harness

Reciprocation Gait Orthosis  Releasable hip joint & knee joint for sitting  Cable coupling of hip flexion to contralateral hip extension

Questions