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Download Gait and orthotics - VCU Physical Medicine & Rehabilitation
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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 Weight Acceptance Mid Stance Terminal Stance PreSwing Single Limb Support Stance Phase Initial Swing MidSwing Terminal Swing Limb Advancement 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 Gait Events (Perry) 1. 2. 3. 4. 5. 6. 7. 8. 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 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 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
