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Biomechanics of BKA

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Biomechanics of BKA Renee Kitto Port Macquarie Base Hospital Contents Normal gait Prerequisites of Normal Gait Gait characteristics of BKA Other causes of gait ... – PowerPoint PPT presentation

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Title: Biomechanics of BKA


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 asymetrical

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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