Transcript Analysis and Training of Amputees on Stairs (pps)

ANALYSIS & TRAINING OF
AMPUTEES ON
S
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Outline

Normal Biomechanics
 Differences with Below-Knee Stair Patterns
 Implications
 Video
 Brainstorming!
**Consider what muscles / segments are
affected in amputee clients during discussion
Normal Characteristics

Cadence
– Ascent = 82-116 steps/min
– Descent = 107-140 steps/min
– Shorter women go faster!

Proportions:
– Ascent = stance 50-65%
– Descent = stance 19-68%
– 31% double support
Trans-Tibial Amputees

Slower velocity (Powers et al, 1997)
– Ascent: 80% of normal
 (29.6m/min vs 33.4m/min)
– Descent: 84% of normal
 (29.6m/min vs 35.2m/min)

Significant stance phase asymmetry,
especially single support (decreased 12%
ascending, 13% descending).
Trans-tibial Amputees

Powers et al (1997)
 Decreased velocity indicative of
– Limited ability to elevate body mass.
– Diminished ability to maintain forward
progression.

Diminished single support time is an
indication of instability, and difficulty
controlling balance.
Normals

Large amount of intra-subject variability,
but high correlations of certain
characteristics between subjects.
 Higher the activity in certain muscles, the
lower the variability.
 Indicates the inherent instability of this task.
Stair Ascent

McFadyen & Winter (1988)
 Stance
– Weight Acceptance (WA)
– Pull Up (PU)
– Forward Continuance (FCN)

Swing
– Foot Clearance (FC)
– Foot Placement (FP)
Weight Acceptance

Moves body into optimal position to be
pulled up onto the step.
 Initiated by contralateral plantarflexors.
 Involves strong concentric activity of hip &
knee extensors.
 Ankle moves into ~130 dorsiflexion, with
soleus working eccentrically to stop too
much knee flexion.
Weight Acceptance – BKA’s

Powers et al (1997)
– Lengthened “initial double limb support”.
– Indicates difficulty transferring weight forwards
onto prosthesis.
– “Prosthetic DF only capable of ~70

Yack et al (1999)
– Passive properties of prosthesis cannot limit
excessive knee flexion like soleus would.
Weight Acceptance – BKA’s

Torburn et al (1994)
– Increased hip flexion (trunk flexion) to assist
moving weight forward over the foot.
Pull Up





Most unstable portion – body supported on one
limb, while all joints are flexed.
Support moment twice normal gait.
Concentric power generation by VL and
plantarflexors (mainly soleus).
Hip moments & power are variable – must control
Head/Arms/trunk segment.
Gluteus medius active at beginning of PU, keeping
pelvis level during single support.
Pull Up – BKA’s

Powers (1997), Yack (1999) & Torburn (1994)
– Amputees used a “hip dominant” strategy to raise body
weight, rather than “knee strategy”.
– Decreased joint moments & powers at knee & ankle.
– Increased joint moments, powers, and total work at hip

20% inc hip extensor work; 40% inc VL work;
 Increased & prolonged hamstring contractions
– Assist hip extension
– Protect distal tibial remnant from pressure on anterior
socket.

RF recruited to assist VL.
Forward Continuance

The subject has ascended the step, & is
moving forward to the next.
 Mainly horizontal – no vertical shift of
CoM until just prior to toe-off.
 Support moment remains extensor, with
burst of gatrocs/soleus activity at the end to
produce vertical thrust.
Forward Continuance – BKA’s
 Decreased
hip extension range /
increased trunk flexion.
 No plantarflexion for vertical thrust.
Foot Clearance

Involves lifting the leg & clearing the
intermediate step.
 Involves concentric dorsiflexor activity,
then concentric hamstring activity.
 Forward & up movement produced by hip
flexors (not RF) & contralateral vertical
thrust.
 Some RF activity to reverse knee flexion &
limit heel rise.
Foot Clearance – BKA’s
Decreased dorsiflexion range: ~50
 Knee motion not significantly different
(Powers et al 1997).

Foot Placement

Hamstrings work eccentrically to lower the
foot, with simultaneous concentric DF
activity.
 Final foot position is controlled by hip
extensors.
 Preparatory activity prior to foot contact in
RF, VL, Glut max & glut med.
RF
VL
Gmax
Gmed
McFadyen
& Winter
(1988)
Other points

Differences from ground to step 1 compared
to step1 to step 3.
 Two peaks in GRF’s
– Start of single limb support = 107%BW
– End of FCN corresponding to vertical thrust
= 115%BW

No periods of vertical movement without
concurrent horizontal movement.
 Support moment needing to be generated is
2-3 times that for level walking.
Other Points

Need up to 1200 of knee flexion.
Points for BKA’s

More prolonged & intense EMG (Powers et al
1997) through stance.
– Total combined power generation avg 32% of isometric
MMT, vs 23% in normals.

Increased energy expenditure.
 Moment & power calculations may be decreased
around the knee, as calculations do not account for
co-contraction with hamstrings.
Descent

McFadyen & Winter (1988)
 Stance
– Weight Acceptance (WA)
– Forward Continuance (FCN)
– Controlled Lowering (CL)

Swing
– Leg Pull-Through (LP)
– Foot Placement (FP)
Weight Acceptance

Usually a toe-strike
 Dominated by eccentric activity of RF, VL,
gastrocs & soleus.
 Most energy is absorbed by plantarflexors.
Weight Acceptance – BKA’s

Powers et al (1997)
– Foot contact in ~ 30 DF, thus no toe-strike, and no
energy absorption through PF’s.
– Increased Gmax & hamstrings activity to assist weight
shift.

? Softer contact = no momentum, & therefore
must actively extend to shift weight.
 Decreased knee flexion during WA.
Forward Continuance

Extensor moment at all 3 lower limb joints.
 Knee extends slightly while moving
forwards.
 Movement controlled by eccentric
plantarflexor activity.
Forward Continuance –BKA’s

Prolonged & more intense hip extensor
activity.
Controlled Lowering

Involves descent to the next step.
 Power absorbed by eccentric quads, less so
from soleus.
 Burst of concentric soleus activity at the
end, to relieve the extreme dorsiflexed
position.
 Hip flexors working concentrically –
suggests working to control
Head/Arms/Trunk segment rather than
assist in the lowering of the body
Controlled Lowering – BKA’s

Powers et al (1997)
–
–
–
–

Decreased knee flexion (170 vs 250).
Decreased ankle DF (100 vs 230).
Increased hip flexion (290 vs 170).
Greater anterior pelvic tilt.
Significant Gmax activity, & prolonged hams
activity:



Hip involved in lowering body mass
Hams co-contraction to protect distal tibia from excessive
pressure against socket (Yack et al 1999).
RF recruited earlier (late swing) and earlier
cessation of activity (16% cycle vs 47% cycle).
Leg Pull Through

Hip continues to flex concentrically.
 Knee flexion required to clear intermediate
step (but not as much as ascent ~1000).
 Ankle dorsiflexes concentrically.
Foot Placement
Reversal of movement – hip & knee extend,
ankle plantarflexes.
 Hamstrings decelerate knee extension.
 Glut med active just prior to contact – may
have been involved in keeping limb
abducted as well as preparing for WA.
 Tib-Ant contraction just prior to contact to
move impact point to outer border of foot.
 Gastrocs co-contraction in preparation for
impact.

Foot placement – BKA’s

No active plantarflexion in preparation for
impact.
McFadyen & Winter 1988)
Figure 4: EMG During Descent (McFadyen & Winter, 1988)
Other Points

Differences from step 3 to 1 compared to
step 2 to floor.
 No vertical movements without concurrent
horizontal movements.
 Descent speed correlated significantly with
cross-sectional area of knee extensors &
psoas major – suggests muscle mass plays a
role.
Other Points

Evidence of preparatory actions in Gmed, Gmax,
VL, & gastrocs.
 Two peaks in GRF’s:
– First at start of WA = 120%BW
– Second at end of FCN / start CL = 100%BW

Greater Centre-of-Mass / Centre-of-pressure
divergence indicates greater inherent instability in
descent – “controlled fall” (Zachazewski et al
1993).
Other Points
Use of handrail “in the usual fashion” did
not influence flexion/extension moments
(Andriacchi et al 1980).
 Joint ROM required:

– Up to 1000 knee flexion.
– Up to 250 ankle dorsiflexion.
IMPLICATIONS
1.



Ascent & descent requires up to 1200 knee
flexion & 250 dorsiflexion.
Uh oh.
Reduce bulk in popliteal area.
Foot placement in descent – toes over
edge to allow foot to roll over.
2. Large power bursts are required in the stance hip
& knee, and in a greater range than level
walking.
 Train through required ranges concentric &
eccentric.
 Vary tread depth & riser height to alter intensity.
 “Power”, not strength. Consider speed & timing,
esp as hip & knee extend together in ascent.
 Consider:
–
–
–
–
–
Part practice – part range -> full range.
Double support -> single support.
Practice step to same level -> 2 steps.
Minimise use of hand for pulling up or weight
bearing.
Maximal extension in ascent occurs before
contralateral foot placement.
3. In ascent, 2nd peak in GRF occurs at end of
stance (vertical thrust), produced by PF’s.
 No PF’s on amputated side – increased
demand on extensors on intact side.
 Older / frail vascular amputees may have
difficulty ascending on intact limb as
contribution from contralateral PF’s is
absent -> need to train bilaterally.
 Older / frail vascular amputees have
weakness of intact PF’s (Winter et al 1990)
-> increased demand on amputated side
quads when ascending step over step.
4. Hip & Knee flexion occur simultaneously
during swing in ascent.
 Train as a unit.
 Make use of motion-dependent
characteristics of swing (momentum/inertia)
to assist.
 Specific strategies to increase strength &
recruitment of psoas & hamstrings.
 How much circumduction is allowed?
5. Activity in RF, VL, Gmax & Gmed is
evident before foot contact.
 Specificity of practice includes stages prior
to targeted component to allow learning of
preparatory actions.
6. At no time is there a vertical shift of CoM
without a concurrent horizontal shift.
 Clients must be trained to move forward &
up, or forward & down.
 Consider what muscles / prosthetic
components should be involved in assisting
or limiting this movement.
 Eg plantarflexors normally control forward
movement during FCN in descent.
– What has to compensate?
– Will the client avoid forward movement as they
feel they have no control?
7. During descent, the largest GRF occurs at
weight acceptance – 120%BW – and most
energy is usually absorbed by PF’s.
 Implications even in “bad leg to hell” patterns.
 Landing is more stressful than lowering.
 Eccentric control of quads/hip
extensors/abductors must be trained during
landing, including proper forward shift during
WA, to assist in shock absorption and control
forward shift in place of PF’s.
 Increased demand on contralateral limb during
it’s CL phase.
8. No toe-strike during descent on prosthetic
side.
 Contralateral limb may have greater
demands on
– Knee joint flexion
– Eccentric quads strength through that increased
range.
– Ankle dorsiflexion range.

Energy absorption through eccentric quads
control -> train “impact” / knee flexion (no
greater than ~230)
9. Differences in kinematics & kinetics
observed with Floor <-> step vs
step <-> step.
 Also need to include approach – planning
step lengths appropriately, & different
ranges / powers on different steps.
 Training on 1 step does not always carry
over to a flight of steps.
10. Incorrect use of handrail is the most common
compensation.
 Pulling or weight bearing on rail masks kinematic
or kinetic deviations.
 Structure environment to minimise hand use but
maintain safety:
–
–
–
–
–

Which side holds rail? Suggest ipsilateral.
Grip
Rail vs aid vs standby assist
Height of rail (or other hand support)
Step heights in part practice to allow practice of correct
activation patterns.
Use of rail in normal fashion did not influence
flexion / extension moments.
11. Improve power in muscles that
compensate for loss of ankle mechanism.
 Ipsilateral VL, RF, (conc & ecc), hams as
hip extensor
 Contralateral PF’s, VL, RF, hams as hip
extensor.
 Ipsilateral hip flexors (no vertical thrust).
12. Remember to train Core Stability for trunk
control.
 Increased “hip dominance”, but they will
need a stable base to work off.
References
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across the hip and knee joints in the elderly. Osteoarthritis and Cartilage. 10, 5, 353-359.
Lyons, K., Perry, J, Gronley, J.K, Barnes, L, and Antonelli, D. (1983). Timing and relative intensity of hip extensor and abductor
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Seattle Lightfoot. Journal of Rehabilitation research & Development, 34, 1, 9-18.
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