Transcript Biomechanics of BKA

Biomechanics of BKA
Renee Kitto
Port Macquarie Base Hospital
Contents
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Normal gait
Prerequisites of Normal Gait
Gait characteristics of BKA
Other causes of gait abnormalities
Normal gait
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Analysing pathological gait, compare to
normal
Identifying gait deviation, you can work
towards normal gait
Normal gait is the most energy efficient
Stance Phase
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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%)
Swing Phase
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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%)
Prerequisites of normal gait
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Stability in Stance
Clearance in swing
Pre-position of the foot in terminal swing
Adequate step length
Energy conservation
Gait characteristics
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BKA gait is asymetrical
Gait Characteristics
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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
Gait Characteristics
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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
Gait Characteristics
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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
Gait Characteristics
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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
Gait Characteristics
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Joint Power
– Midstance
• Increased hip abductor activity (prosthetic
side)
– Push-off
• Increased hip flexor power generation
(prosthetic side)
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
References
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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.
References
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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.