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

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

Double stance occurs in initial and terminal 10% of stance, thus middle 40% of stance is single limb support 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

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

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 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 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

Muscle activity in gait cycle* Pre-tibial muscles eccentrically slow plantarflexion after heel strike, some action in stance for sub-talar influence and some activity in swing for toe clearance. Gastroc/soleus with peak in push off for CG propulsion but also eccentrically controls shank progression over ankle. Quads peak after heal strike to absorb knee flexion. RF active in late stance with flexed hip and knee to reduce heel rise. Quads also active in early swing to keep lower leg swinging on femur. Hamstrings with 2 peaks around heel strike. Firstin terminal swing to slow forward swing with hip extension and knee flexion action in open chain role. Second is closed chain role with foot contact to extend knee and hip for stability. Variable late peak helps with extension in push off. Muscle activity in gait cycle*

Glut medius and minimus give abduction support in initial contact& early stance to reduce pelvic tilt. Adductors peak at initial contact, possibly from hamstring portion of adductor magnus slowing hip flexion & possibly to help with femur internal rotation in closed chain role. Second adductor peak at end of stance may help accelerate the limb forward into swing with muscles aiding hip flexion. Glut max absorbs heel strike shock eccentrically, keeps hip and knee extended. Second peak with push off may help hip and knee extension to propel body on fully extended stance leg. Show gluts as knee extensor in closed chain model Spine erector mass active on heel strike each side to prevent trunk flexion over pelvis and provide medial/lateral stability. Muscle activity*

Energy costs and gait* Lowest = normal +/- 1 SD Forearm crutch use next = amputee with suction socket prosthetic next = amputee with pylon next = forearm crutch use 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* May see hip OA patients lean over stance leg to reduce glut medius contraction, shoulder dip. May see external rotation of affected leg due to hip effusion. 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 Keeps line of force behind knee when compensate for gastroc/soleus weakness. 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 HKAFO’s AFO’s Reciprocating Gait Orthosis Functional Electrical Stimulation (FES) AFO’s Double metal upright Plastic Molded off shelf VAPC KAFO’s Many designs for band configurations Metal vs. plastic

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* Heel cutting or cushioned heel wedge moves point of ground reaction force contact forward and brings force line closer to knee axis of rotation. 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 5o 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 Medial/lateral laxity 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

Considerable forces are measured with variable strap configurations which can cause tissue damage in insensate skin. Cyclic ambulation reduces this effect, but must avoid bony prominences and use adequate straps to distribute forces. Shear forces at knee also vary with strap design.

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

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