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Biomechanics of BKA

Biomechanics of BKA. Renee Kitto Port Macquarie Base Hospital. Contents. Normal gait Prerequisites of Normal Gait Gait characteristics of BKA Other causes of gait abnormalities. Normal gait. Analysing pathological gait, compare to normal

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Biomechanics of BKA

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  1. Biomechanics of BKA Renee Kitto Port Macquarie Base Hospital

  2. Contents • Normal gait • Prerequisites of Normal Gait • Gait characteristics of BKA • Other causes of gait abnormalities

  3. Normal gait • Analysing pathological gait, compare to normal • Identifying gait deviation, you can work towards normal gait • Normal gait is the most energy efficient

  4. Stance Phase • Begins at heel strike on one leg and ends at toe off on the same leg • Initial contact (heel Strike) • Loading response (0-10%) • Mid-stance (10-30%) • Terminal stance (push off) (30-50%) • Pre swing (toe off) (50-60%)

  5. Swing Phase • Begins where stance ends and is the period between toe off on one leg and heel strike on the same leg • Initial swing (60-73%) • Mid-swing (73-87%) • Terminal-swing (87-100%)

  6. Prerequisites of normal gait • Stability in Stance • Clearance in swing • Pre-position of the foot in terminal swing • Adequate step length • Energy conservation

  7. Gait characteristics • BKA gait is asymmetrical

  8. Gait Characteristics • Temporal and distance factors • Stance phase shorter on prosthetic side • Step length of the prosthetic side longer and faster • Self selected walking velocity is lower • Decreased Cadence • Average stride length is shorter

  9. Gait Characteristics • Joint Angles • Decreased knee flexion (prosthetic side) during early stance • Decreased knee flexion (prosthetic side) during late stance • Larger relative knee angle range on the prosthetic side compared to the unaffected side • Greater than normal positions of maximum hip flexion (prosthetic side) • Increased knee flexion (unaffected side) during early stance

  10. Gait Characteristics • Joint moments • Unaffected side • Higher hip extensor moment during stance • Higher hip flexor moment during early swing • Higher knee extension moment during stance • Prosthetic side • Ankle D/F moment longer in duration and larger in amplitude during early stance

  11. Gait Characteristics • Joint Power • Heel Contact (unaffected side) • Increased hip extensor activity (unaffected side) • Heel Contact (prosthetic side) • Increased hip abductor activity (unaffected side) • Increased knee extensor activity (unaffected side) • Increased hip extensor muscle bursts on both sides

  12. Gait Characteristics • Joint Power • Midstance • Increased hip abductor activity (prosthetic side) • Push-off • Increased hip flexor power generation (prosthetic side)

  13. Other causes of gait abnormalities • Prosthesis • Patients capability and general condition • Shape, length and size of the residual limb • Discomfort • Inadequate or incorrect re-education • Psychological, social or economic reasons

  14. References • Bateni, H et al (2002) Kinematic and Kinetic Variations of Below-Knee Amputee Gait. Journal of Prosthetics and Orthotics, 14, 2-10. • Engstrom, B&, Van de Ven, C (1999) Therapy for Amputees. London: Churchill Livingstone., 115-136. • Robinson, J et al (1977) Accelerographic, Temporal, and Distance Gait Factors in Below-Knee Amputees. Physical Therapy, 57, 898-904.

  15. References • Sadeghi, H et al (2001)Muscle Power Compensatory Mechanisims in Below- Knee Amputee Gait. American Journal of Physical Medicine and Rehabilitation, 80, 25-32. • Ruud, W et al (2004) Adaptions to Mass Perturbations in Transtibial Amputees: Kinetic or Kinematic Invariance. Archives of Physical Medicine and Rehabilitation, 85, 2046-2052.

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