Lower limb orthotics

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

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

3. 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

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

7. 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)

8. Terminology • Cadence: The step rate per minute (x= 113 steps per min) • Velocity: The speed at which one walks (x= 82 m/min)

9. 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

10. Gait Events • Phases: 1) Stance Phase: 60% 2) Swing Phase: 40% • Periods: 1) Weight Acceptance 2) Single Limb Support 3) Limb Advancement

11. Gait Events (Perry) • Initial Contact • Loading Response • Mid Stance • Terminal Stance • Pre-Swing • Initial Swing • Mid Swing • Terminal Swing

15. 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

18. 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

19. 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

20. Determinants of gait • Foot, ankle, knee and pelvis contributions to smoothing center of gravity motion to preserve energy • Inman APMR 67

21. 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

22. 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 Determinants

25. Muscle activity in gait cycle*

26. Muscle activity*

27. Energy costs and gait* Forearm crutch use Normal subjects

28. Joint stability in gait • Determined by relationship between muscle support, capsule & ligamentous support, articular relationships and lines of force

34. Gait deviations • Structural bony issues • Joint/soft tissue changes • Neuromuscular functional changes

35. 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

36. ROM loss or ankylosis will show proximal compensation with or without velocity changes.

37. Other orthopedic problems affect gait* • Foot equinus gives steppage gait to clear the relatively longer leg • Calcaneal deformity changes push off and initial contact

38. 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

39. 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.

40. 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

41. 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

42. 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*

43. 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

46. LE Orthotics • Weakness • Skeletal & joint insufficiency

47. 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

49. 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) LE weakness orthoses

50. 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!!