Basic Prosthetics I

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  • Topics will be broken down into five parts
    Part I Introduction
    Orthotic overview
    Terminology
    Brief History
    The Orthotist
    Part II Basic anatomy
    Osteology
    Myology
    The nervous system
    Part III Basic biomechanics
    Biomechanics of orthotics
    Normal gait versus pathological gait
    Part IV Pathology and orthotic solutions
    Part V Construction of orthotics
  • Was ist anders? Hier ein einfacher Vergleich des normalen Ganges in der Ebene zum Prothesengang in der Ebene.
    Keine vollständigkeit wird erwartet.
    IN jeder der folgenden Folien könnte auf die Physiotherapie hingewiesen werden, da sie die Hauptrolle im Wiedererlernen hat
  • Terminologie hilft der Kommunikation. Ein standard ist noch nicht einheitlich durchgesetzt.Wir sollten unseren beitrag dazu leisten uns auf diesem Niveau zu unterhalten. Das stärkt unser Selbstvertrauen und gibt uns ein ebenbürtiges Bild innerhalb des Reha teams.
  • Loading response is 12% of the entire gait cycle.
    Ankle , knee and hip are assisting to dampen the full intensity of rapid floor contact ( 60% in 0,02 seconds)
  • Let´s have a look at each of the involved joints in the lower limb how they manage to absorb the impact.
    In the unbalanced situation of terminal swing when the body weight is anterior to the supporting forefoot. The body is falling forward.
    While the forward foot is still 1cm off the ground positioned for stance. For a short period of time the body is in free fall.
    Ankle plantar flexion is the first immediate reaction to initial floor contact by the heel.
    Complete floor contact is reached at the 8% point of the gait cycle.
    Most of the 10°plantarflexion occurs as a free foot flat.The pretibial muscles restrain the motion until the forefoot touches the ground
  • The higher the impact the higher the forces.
    This mechanism is disrupted when joints, muscles or parts of the shock absorbing system are missing.
    Shock absorbing mechanisms gain importance the higher the amputation or the higher the impact.
    Shock absorbers can reduce early skin breakdown, prevent from back pain and therefore assist to accomplish a natural gait.
  • When load is taken on the toes the metatarsal joint bends up to 55° but stability is maintaint by the arch of the foot.A high percentage of load is taken by the forefoot in terminal stance
  • The toe supports the knee to stay stable until the body weight is taken over by the contralateral side.
  • Is the toe lever is missing the extension moment to the knee is absent earlier than normal.To compensate for this deficit the contralateral side has to support the body weight at an earlier moment.
    Amputees using a foot with a shortened keel will experience higher impact at heel strike on the sound limb.
    Time spent on the sound limb is also longer.
    That means especially dysvascular amputees can benefit from a full length toe lever in order to protect the sound limb against excessive forces on the remaining limb.
  • Between each phase of gait there is a rotational moment in each joint of the lower limb.
    If one of these joints is missing natural gait is disrupted.
    Rotational elements in a prosthetic leg can reduce shear forces on the resudual limb and help to achieve natural gait.
  • Was ist anders? Hier ein einfacher Vergleich des normalen Ganges in der Ebene zum Prothesengang in der Ebene.
    Keine vollständigkeit wird erwartet.
    IN jeder der folgenden Folien könnte auf die Physiotherapie hingewiesen werden, da sie die Hauptrolle im Wiedererlernen hat
  • Was ist anders? Hier ein einfacher Vergleich des normalen Ganges in der Ebene zum Prothesengang in der Ebene.
    Keine vollständigkeit wird erwartet.
    IN jeder der folgenden Folien könnte auf die Physiotherapie hingewiesen werden, da sie die Hauptrolle im Wiedererlernen hat
  • Basic Prosthetics I

    1. 1. Normal Gait vs. Prosthetic Gait Clinical Course R&D 8/23/12
    2. 2. Normal Gait Cycle – 2 phases • Stance Phase Time the foot is in contact with the floor • Swing Phase Time the foot is in the air Stance Phase 60% 8/23/12 Swing Phase 40%
    3. 3. Divisions of the Gait Cycle- 8 phases Stride (Gait Cycle) Periods Stance Swing Tasks Weight Acceptance Single Limb Support Limb Advancement Phases Initial Loading Mid Contact Response Stance 8/23/12 Terminal Stance Pre Swing Initial Swing Mid Swing Terminal Swing
    4. 4. Normal Gait Cycle Perry 1992 Inman 1981 1. Initial Contact Heel strike (0 - 2% of the GC) 2.Loading Response Foot Flat (2 -12% of the GC) 3.Mid-Stance Mid Stance (12 - 30% of the GC) 4.Terminal Stance Heel Off (30 – 50 % of the GC) 5.Pre-Swing Heel Off - Toe Off (50 – 60 % of the GC) 6.Initial Swing Toe Off - Early Accl. (60 – 73 % of the GC) 7.Mid-Swing Mid Swing (73 – 87 % of the GC) 8.Terminal Swing Deceleration (87 -100 % of the GC) 8/23/12
    5. 5. Loading Response Loading reponse phase GRF 100% BW • 60% of the body weight is transferred in 0,2 sec time 12% 8/23/12
    6. 6. Loading Response •In normal gait the body weight has a free fall in the end of terminal swing •The body weight falls about 1 cm causing high impact •The human body immediately reacts with controlled plantar flexion •The quadriceps controls knee flexion in early stance 8/23/12
    7. 7. Stance phase vs speed • Increasing speed results in increased impact. Walk Slow Walk 200 Run • Shock absorbing systems assist to achieve natural gait and reduce impact 100 0 0 8/23/12 62%
    8. 8. Terminal Stance • Maximum angle in the toe joint shows 55° in pre swing 8/23/12
    9. 9. Terminal Stance The forefoot lever arm stabilizes the knee and supports the center of mass 8/23/12
    10. 10. Terminal Stance •Full length toe lever prevents: - pelvis from droping - knee instability •Resulting in: - symmetrical gait - more equal stride length - reduced impact on the sound side 8/23/12
    11. 11. Rotation 8/23/12
    12. 12. Speed and Gait Stance Phase Swing Phase 60% 40% 5 km/h 7 km/h 8/23/12
    13. 13. Speed and Gait • Swingtime related to walking speed 0,55sec 0,40sec 0,8 m/sec 8/23/12 1,8m/sec
    14. 14. TT Typical Prosthetic Gait 1. 2. 3. 4. 5. 6. Shortened midstance Reduced stance flexion Early heel off Early toe off Reduced stance phase time Reduced knee flexion in swing (Breakey 1976) 8/23/12
    15. 15. Prosthetic issues resulting in pathologic gait - TT Typically prosthetics are too short! WHY? •Lack of suspension •Potential Clinical issue: shorter prosthetic leg (Lilja et al. 1994) •Increased hip to toe distance: •Lack of dorsiflexion •single axis knee design (Gard et al. 1996) 8/23/12
    16. 16. Prosthetic issues resulting in pathologic gait - TF • Average ground clearance 1,29cm Winter DA. Foot trajectory in human gait: a precise and multifactorial motor control task. Phys Ther 1992; 72:1:55-66 • Average socket pistoning 10mm Erikson, Roentgenological Study of certain Stump-Socket Relationship in Above-knee Amputees with Regard to Tissue Proportios, Socket Fit and Attachment Stability. Upsala J Med Sci, 1973. 78: p. 203-214. 8/23/12
    17. 17. Pathologic Gait TF Circumduction Vaulting 8/23/12 Hip Hiking Duchenne
    18. 18. Pathologic Gait TT 8/23/12
    19. 19. Plantar Dorsiflex. in ° Plantar Dorsiflex. in ° Ankle motion in stair walking Ascent Stance Swing Descent Swing Stance Normal (Andriacchi et al.1991) 8/23/12 Prosthetic (Powers et al. 1997)
    20. 20. Shortcomings of prosthetic foot design with respect to kinematics •Kinematics: The angular ranges are generally larger during stair walking than during level walking. Ascend: IC in dorsiflexion TS in plantarflexion Descend: IC in plantarflexion TS in neutral R. Riener et al. / Gait and Posture 15 (2002) 32–44 8/23/12
    21. 21. Shortcomings of prosthetic foot design with respect to kinematics •Decline: IC in slight plantarflexion TS in dorsiflexion M. Kuster,S. Sakurai, G A Wood PhD Kinematic and Kinetic Comparision of downhill and level ground walking Clinical Biomechanics Vol. 10,No. 2, pp. 79-84, 1995 8/23/12

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