basic biomechanics behind the assistive devices and their uses.

1. Rashmita dash
MPO
NILD, Kolkata
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2.  Walking aids are used to assist locomotion by
reducing the load on damaged tissue,
alleviating pain, or compensating for loss of
muscular control.
 Walking frames, axillary crutches, elbow
crutches, walking sticks and tripod-based
sticks are used for a range of musculoskeletal
and neurological deficiencies including
fractures, amputation, joint replacement,
stroke-induced hemiplegia and paraplegia.
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3. A walking aid is used to support the body
by transmitting a load through the hand
and is capable of being oriented by the
upper limbs to assist in the stability,
support and restraint/propulsion functions
of gait.
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4.  A geometrical configuration which provides a stable base
of support
 Good frictional properties between the aid tips and the
ground surface which may be wet, frozen or uneven,
 Adequate strength to resist up to 60 percent body weight
repeatedly
 Enable the wrist, elbow and shoulder joint and shoulder
girdle to bear the loads transmitted by the aids
comfortably,
 Be lightweight and maneuverable for walking among
pedestrians and negotiating stairs, public transportation,
etc.
 Permit the user to release his hands quickly if required to
brace a fall. 4

5. Crutch walking offers physiological and
psychological advantages that a person
cannot gain by sitting and using wheeled
mobility.
Approximately twice as much energy is
required to walk with crutches than to walk
without assistance (Fisher & Patterson
1981).
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6. Types of crutch:-
1. Underarm
2. Triceps
3. Forearm (Lofstrand)
4. Platform
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7. There are harsh forces on the body due to
crutch walking with axillary crutches.
Forces at the crutch tip are transferred
directly to the hand and wrist and indirectly
to the axilla (Pariziale & Daniels, 1989).
Two important forces during crutch walking
are - the horizontal forces on the axilla and
the total load on the hands
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8. Crutches have many physiological and
psychological benefits to individuals who
use them by allowing them to walk instead
of using wheeled mobility to get around.
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9.  According to the study by Wilson and Gilbert
(1982), the crutch user’s hands support 1.1 to 3.4
times his/her body weight, and the axilla support a
horizontal load of about 3 to 11% of his/her body
weight.
 During partial weight bearing crutch gait, the
stance phase decreased significantly on the
affected limb and increased significantly on the
supporting limb.
 The center of gravity was shifted toward the
supporting limb side of the body (Li et al., 2001).
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10. Three loading patterns were consistently
repeated in the groups:
tending to extend the elbow and shoulder,
tending to flex the elbow and extend the
shoulder,
and tending to abduct the shoulder.
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11. 11

12. From the forces and moments at the load
cell (Fx, Fy, Mz) and the ground reaction
forces.
when the crutch was at its vertical position,
the forces and locations of the resultant
forces at the
handgrip and axillary pad were calculated
using the equation F = ma. The three
equations used for the forces at the
handgrip were:
1) FHGx + FLCx + FCTx = 0
2) FHGy + FLCy + FCTy = 0
3) MLCz + MCTz + Lx-HG_FHGy + Ly-
HG_FHGx = 0
Assuming:
a = 0
FHGz = 0
MHGz = 0
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13.  The three equations
used for the forces at
the axillary pad were:
1) FAPx + FLCx = 0
2) FAPy + FLCy = 0
3) MLCz + Lx-AP_FAPy
+ Ly-AP_FApx = 0
Assuming:
a = 0
FAPz = 0
MAPz = 0
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14. For long-term crutch users, using this
modified design for the handgrip may help
to lower the jarring forces on the hand by
the crutch handle.
The angled handgrip design can potentially
provide more comfort to crutch users by
distributing the forces along the hand
instead of Concentrating the forces on only
the front of the hand.
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15.  In the case of hip or knee pain, a cane is typically
used on the side contralateral to the affected limb
in a reciprocal pattern.
 Contralateral cane use takes advantage of the
normal reciprocating movements of the arm and
the leg while walking and it helps maintain the
patient’s center of gravity over his or her base of
support when using the cane.
 More specifically, contralateral cane use increases
the lever arm at the hip in the coronal plane,
thereby reducing compressive forces generated by
the abductor muscles and body mass at the hip
joint
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16.  When the cane is used in the ipsilateral hand of
healthy subjects, peak vertical reaction force acting on
the foot in heel strike and midstance phase decreases
the most when the cane and heel touch the ground
simultaneously.
 The center of force also does not shift significantly with
ipsilateral cane use compared with normal gait, but
when the cane is used on the contralateral side, the
center of force shifts medially.
 Based on their results in healthy subjects, these
investigators suggest that patients with varus knee OA
should use the cane in the ipsilateral hand, while those
with valgus knee OA should use the cane in the
contralateral hand.
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17. use of a cane can increase stability
by allowing a stabilizing hand reaction
force (with components
FCV and FCH) to be generated. During
single-leg support, the
body weight creates a destabilizing
moment (FWA) with respect to
the supporting foot that causes the COM
to fall toward the unsupported
side. FCV and FCH act to oppose the
downward and lateral
COM motion. Moment FCV(CA) acts to
oppose the rotational
motion of the body.
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18.  force and moment applied to the cane by
the hand can generate a horizontal AP
 ground reaction force (FH) that can
provide (B, C) propulsion or (D) braking
during gait. For simplicity, the weight and
mass of the cane are
 assumed to be negligible. When the cane
is vertical, it is necessary to exert a
moment (M) at the hand to generate the
propulsive force, as
 indicated in A and B (similarly, but not
shown, a hand moment in the opposite
direction would generate a braking force).
However, because
 the hand can only exert a small moment,
it is more effective to generate the
propulsive or braking force by holding
the cane at an appropriate angle C & D.
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19.  Cane in
contralateral hand
decreases JRF.
 Long moment arm
makes it effective.
 15% body weight
to cane reduces
joint contact forces
by 50%.
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20. Three loading patterns were consistently
repeated in the groups:
tending to extend the elbow and shoulder,
tending to flex the elbow and extend the
shoulder,
and tending to abduct the shoulder.
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21. 21

22.  Walkers are frames that provide bilateral
support without the need to control two canes
or crutches.
 A variety of walkers are manufactured and
are described based on their design:
 Base: Four tips, two tips and two wheels,
four wheels, three wheels
 Uprights: Rigid, folding, reciprocating, stair
climbing
 Proximal portion: Hand grips, platform
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23.  Free body diagram showing the
forces and moments acting on the
arms when lifting a mobility aid.
 MS is the net moment generated by
the shoulder musculature
 HS and VS are the shoulder reaction
forces,
 mW is the mass of the walker, mA
is the mass of the
 arms, and g is the acceleration due
to gravity.
 HS and VS will increase with the
amplitude of the forward (aH) and
upward (aV) walker acceleration,
and will also increase with the mass
of the walker.
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24. Three loading patterns were consistently
repeated in the groups:
tending to extend the elbow and shoulder,
tending to flex the elbow and extend the
shoulder,
and tending to abduct the shoulder.
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25. CRUTCH- Alternating (reciprocal) gait
pattern includes four point , two point,
three point gait.
Swinging (simultaneous) gait patterns
includes drag to gait swing through gait
and swing to gait .
CANE GAIT
WALKER GAIT
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26. THANK
YOU
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