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Section 1: General Topics
the components in established ways. Research has demonstrated that, although
prosthesis users are able to accurately
sense and report changes in pros thetic
function resulting from changes in alignment, these reports are less accurate for
angular alignment changes of less than
6° and translational alignment changes
of less than 20 mm of translation.
12,13
Goal of Dynamic Alignment
Although different goals for prosthetic
alignment have been suggested, no single optimal alignment has been objectively measured or described.14 Rather,
studies have demonstrated that a range
of alignments are acceptable to both patients and prosthetists.
14-16
Although the
reduction of asymmetries is a legitimate
goal, not all parameters of gait reach the
same level of symmetry when a prosthesis is optimally aligned for a particular
patient.17 In addition, a direct relationship between kinetic and kinematic
changes should not be assumed.2 There
is evidence that patients consider overall function more important than the
presence or degree of gait deviation, so
prosthetists must use clinical judgment
in determining which deviations should
be minimized to ensure optimal longterm health and function.
18
Factors Affecting
Gait Patterns
Each component of a prosthesis can con
tribute directly or indirectly to the gait
pattern of the patient. The prosthetist
is responsible for ensuring that the fit
of the prosthetic socket and the associated suspension mechanism are optimal
and support the functional level of the
patient. In addition, the functional characteristics of the foot, ankle, and knee
components can substantially affect the
patient’s gait pattern and must be considered. Factors as seemingly benign as
the height and density of a shoe’s heel
can affect the orientation of the foot
in the sagittal plane, alter the location
of ground reaction forces, and affect
proximal joint moments. All relevant
factors should be carefully considered
during the evaluation, fitting, and alignment processes.
Because many patients receive
their first prosthesis after a period of
prolonged debilitation, it is especially
important for the rehabilitation team to
assess how strength, range of motion,
and other health factors may contribute
to a poor gait pattern during the early
phases of prosthetic ambulation. Such
deviations are best addressed through
rehabilitation and training rather than
adjustments to the prosthesis. As such,
these patient factors are best assessed
and addressed in collaboration with a
physical therapist.
Performing Dynamic
Alignment
After the appropriateness of the overall
fit and function of the prosthesis has
been confirmed, the prosthetist can
refine the alignment during multiple
walking trials. For maximum safety,
initial ambulation should occur with
the patient supported by parallel bars.
Ambulation should then proceed within
the clinical environment, using the appropriate assistive devices when needed.
Although initial walking trials should be
performed on level terrain, they can ultimately include common environmental
barriers and terrains, provided that the
-
patient’s safety and comfort is ensured.
During ambulation, ground reaction forces act on the prosthetic foot
creating multiplanar rotational moments between the prosthesis and the
residual limb. Different orientations
of prosthetic components in relation
to each other change the magnitude
and direction of these rotational forces,
causing different joint and socket reaction moments.19 Such alignment variations can cause observable kinematic
changes, gait deviations, and gait improvements.
affect prosthetic gait in predictable ways,
certain gait deviations are commonly
20,21
Because these moments
observed as a consequence of specific
malalignments.22 Identification of these
deviations can guide the prosthetist in
adjusting the alignment to reduce inappropriate moments and optimize
the gait pattern. Gross malalignments
in each plane should be reduced when
they are observed. Because sagittal plane
malalignments can substantially affect
coronal plane moments, it is advisable
to finalize the sagittal plane alignment
first, followed by the coronal plane
alignment.
23
The spatial orientation of components in a prosthesis is commonly described according to angular and linear
relationships. Angular relationships in
the sagittal plane involve socket flexion, foot dorsiflexion, socket extension,
and foot plantar flexion. In the coronal
plane, the angular relationship involves
socket abduction, foot eversion, socket
adduction, and foot inversion. Linear
relationships include anterior and posterior translation of the components in
the sagittal plane and medial and lateral translation in the coronal plane.
Transverse plane orientation involves
internal or external rotation from the
line of progression (Table 1).
Transtibial Gait Deviations
Although less apparent than deviations
observed with transfemoral prostheses,
there are several gait deviations commonly associated with the use of transtibial prostheses. These include step
length asymmetries, aberrant stance
flexion of the knee during loading response, frontal plane knee instability,
lateral trunk bending in midstance,
premature heel rise, abrupt loading of
the sound side, sound-side vaulting, and
visible pistoning within the prosthesis.
Step Length Asymmetries
Best observed in the sagittal plane,
step length asymmetries can present as
shortened steps on either the affected or
the contralateral side. A short step on
the contralateral side is more common
Atlas of Amputations and Limb Deciencies, Fourth Edition © 2016 American Academy of Orthopaedic Surgeons
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Chapter 7: Clinical Considerations of Observational Gait Analysis
Tab le 1
and often results from the patient’s lack
of confidence in his or her prosthesis
and an associated reluctance to shift and
maintain full body weight onto the pros
thetic limb. This is particularly common
among patients with limited prosthetic experience. As such, improvement
may be seen with time, training, and
improved confidence in the prosthesis.
Less frequently, a shortened prosthetic
step length may be observed. This is often the result of a flexion contracture of
the knee that prevents full extension in
terminal swing and ultimately shortens
the prosthetic step length.
Spatial Relationships of Prosthetic Components
Plane Angular Linear
Sagittal Socket exion/extension
Foot dorsiexion/plantar exion
Coronal Socket abduction/adduction
Foot eversion/inversion
Transverse Internal/external rotation of socket or foot
Anterior/posterior translation of
socket or foot
Medial/lateral translation of socket
Relative inset of foot in relation to
socket
frequently in individuals with shorter
residual limb lengths who are more
prone to anterior distal tibial pressures
-
in the socket.
Although less frequently observed,
knee kinematics in loading response
also can be characterized as reduced
or absent stance flexion or, in extreme
cases, even as hyperextension. Excessive
extension of the socket, an exces sively
anterior foot placement beneath the
socket, excessive plantar flexion, or an
excessively stiff prosthetic keel are all
prosthetic factors that can precipitate
this deviation. Alternatively, this type
of loading response may also be the
Aberrant Stance Flexion
During loading response, a controlled
flexion of 10° to 15° is desired at the
knee. Several variables may unfavorably
product of a voluntary compensation
for weak quadriceps by patients who
fear inadvertent buckling of the knee
and forcibly maintain knee extension.
accelerate this flexion event. Excessive
dorsiflexion of the foot, excessive socket
flexion, an excessively posterior placement of the foot underneath the socket,
and an excessively stiff prosthetic heel
mechanism can all produce this destabilizing moment. A similar effect is seen
when an individual changes the shoe of
the prosthesis to one with a higher heel,
which places the socket in a more flexed
position and effectively increases the
dorsiflexion angle between the plantar
surface of shoe and the patient’s knee.
This deviation may also be seen in patients who do not eccentrically contract
their knee extensors during loading response, either because of quadriceps
weakness or because of the resultant
discomfort created in the socket. As
such, this deviation may be seen more
Frontal Knee Instability
A modest varus moment at the knee
during midstance is generally acceptable. Deviations from this pattern
usually result from faulty prosthetic
alignment. However, excessive varus or
valgus moment also can be caused by an
excessive medial/lateral dimension of
the socket, so special attention should
be given to socket fit if this deviation is
observed. A valgus moment will likely
result from a relatively outset position of
the prosthetic foot beneath the socket.
Similarly, an excessive varus moment
may result from a prosthetic foot that
has been excessively inset. Changes in
step width also can precipitate these
events. For example, a novice walker
who progressively narrows his or her
step width may begin to experience increasing varus moments. In contrast, a
cautious walker who chooses to widen
his or her step width when not using an
assistive device (such as a walker) may
experience a valgus moment at the knee.
Lateral Trunk Bending
Although more commonly associated
with the use of transfemoral prostheses,
a lateral trunk bend will occasionally
be seen in patients using a transtibial
prosthesis during single-limb stance on
the prosthetic limb. This typically occurs when a patient is not fully loading
his or her prosthesis, either because of
socket discomfort or inadequate training or experience. It may also result
from compensation for weak ipsilateral
hip abductors. If the underlying causes
of this deviation are not addressed early
in prosthetic gait training, a fixed habit
may be established.
Premature Heel Rise
Premature heel rise can be thought of as
the result of a prosthetic toe lever that is
too stiff to allow the forward progression
over the foot during single-limb support. Often, it is coupled with patient
reports of increased perceived exertion
during ambulation. It may result from
a foot that is too stiff, too plantarflexed,
or positioned too far anteriorly beneath
the socket.
Abrupt Loading of the Sound Limb
In contrast to premature heel rise, an
inadequate prosthetic toe level allows
the patient to “drop-off” abruptly onto
the sound limb. This may be observed if
the toe of the prosthesis is too flexible or
if the foot is either too dorsiflexed or positioned too far posteriorly beneath the
socket. It has been suggested that the
resultant abrupt loading experienced by
the sound limb may lead to the premature development of osteoarthritis of the
knee and hip. Published evidence has
consistently supported the position that,
for active prosthesis users, the stiffer,
© 2016 American Academy of Orthopaedic Surgeons Atlas of Amputations and Limb Deciencies, Fourth Edition
83
Section 1: General Topics
dynamic resistances associated with
energy storage and release in prosthetic
feet reduce the “drop-off” experienced
at the end of single-limb support on the
prosthesis, with an associated reduction
on the loading rate of the sound-side
24,25
limb.
Sound-Side Vaulting
If a patient is concerned that the toe of
his or her prosthesis may not clear the
ground, a “vaulting strategy” may be adopted in which a sudden concentric contraction of the contralateral side plantar
flexors briefly lengthens the contralateral
limb to allow more space for clearance
of the prosthesis. This strategy is seen
among both transtibial and transfemoral
prosthesis users, and it may initially be
a product of inexperience and a lack of
confidence. For more established users,
it may persist as an individual walking
preference. However, any deviations of
the prosthesis that functionally increase
its length also should be considered and
addressed at the time of observation.
These commonly include a prosthetic
foot aligned in too much plantar flexion
or inadequate suspension, allowing the
prosthesis to piston and functionally
lengthen during the swing phase.
Excessive Pistoning
The term pistoning is commonly used to
describe any vertical movement of the
residual limb within the socket. This
can be observed during early swing
when the residual limb pulls out of the
socket or during weight acceptance as
the limb reseats into the proper position
within the socket. A modest amount of
pistoning is to be expected with certain
suspension strategies, including both
cuff strap and anatomically contoured
socket suspension systems. In other systems, visible pistoning is atypical and
warrants further investigation. For example, excessive pistoning with the use
of suction suspension or locking liners
may indicate a torn sleeve or a mechanical failure in the clutch lock mechanism,
respectively. In addition, pistoning may
be observed if the residual limb has lost
volume and no longer matches the socket volume of the prosthesis.
Transfemoral Gait
Deviations
The gait deviations observed with the
use of transfemoral prostheses are both
more common and more noticeable
than those associated with transtibial
prostheses. Although the relatively bony
nature of the transtibial limb generally
facilitates reasonable control of the prosthesis, the redundant soft tissues of the
transfemoral limb often present a challenge in achieving consistent prosthetic
control. In addition, the shortened anatomic lever arm of the more proximal
residual limb, the increased lever arm of
the longer prosthesis, and compromised
muscular control of the residual limb at
the transfemoral amputation level further reduce a patient’s ability to control
his or her gait pattern while wearing a
transfemoral prosthesis. This is evident
in the coronal instabilities commonly
observed at this amputation level, as
well as in the challenges in maintaining
sagittal knee stability during standing
and ambulation.
Step Length Asymmetry
One of the more commonly observed
gait deviations at the transfemoral amputation level is step length asymmetry, which is characterized by a long
prosthetic step and a shortened step on
the contralateral side. As patients transition from loading response into mid
and terminal stance on their prostheses,
sagittal knee stability becomes a greater
concern. In response, prosthesis users
are often reluctant to shift and maintain
their weight fully on their prostheses
and allow their body weight to transfer
from the heel to the toe of the prosthetic
foot. Rather, a common compensatory
action is a shortened sound-side step, allowing patients to off-load the prosthesis
prematurely. In contrast, confidence in
their sound limb allows them to take a
much longer step with their prosthetic
limb. This collective deviation of a long
prosthetic step coupled with a shortened
sound-side step is especially common
in newer amputees and can become established if not identified and corrected
early in gait training. In addition, hip
flexion contractures, which are commonly present at this amputation level,
preclude the hip on the affected side
from attaining sufficient extension to allow a full length sound-side step. Thus,
gait training and flexibility are key considerations when managing step length
asymmetry at this amputation level.
Stance Phase Knee Instability
For a patient with a transfemoral amputation, voluntary control of the knee
angle is attained through activation of
the hip extensors. Knee stability can be
enhanced by alignment considerations
and the choice of prosthetic knee mechanisms, either through mechanical design or microprocessor regulation. Knee
instability may be the product of a foot
set in excessive dorsiflexion, a prosthetic
heel that is too stiff, or a knee joint positioned too far anteriorly beneath the
socket. Corrective actions may include
plantar flexion of the foot, a softer prosthetic heel, or a more stable alignment in
which the knee joint is moved posteriorly beneath the socket. Such alignment
strategies may be especially helpful in
patients with weaker hip extensors or
shorter limb lengths who are otherwise
challenged in the voluntary control of
their knee stability.
Foot Rotation
Rotational control of the transfemoral
prosthesis is often complicated by the
fleshy nature of the residual limb and
the comparative lack of underlying bony
anatomy. Axial rotation of the prosthesis
on the limb can occur and is generally
observed through the rotational alignment of the foot. This can result from an
ill-fitting socket that is either too tight or
Atlas of Amputations and Limb Deciencies, Fourth Edition © 2016 American Academy of Orthopaedic Surgeons
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Chapter 7: Clinical Considerations of Observational Gait Analysis
too loose. External rotation may occur if
the heel of the foot or the shoe is too stiff
or the foot is set in excessive dorsiflexion. The proximally invasive contours
of many transfemoral sockets are such
that many users will rotate their sockets
to improve prosthesis comfort. Accordingly, rotational alignment should be
gin proximally at the level of the socket,
with subsequent orientation of the knee
and foot positions. Chronic rotational
problems, or transverse alignment that
alternates between internal and external
rotation, may also be indicative of poor
hip control, and may require strengthening and gait retraining.
-
Lateral Trunk Bending
Lateral trunk bending is another
commonly observed deviation at the
transfemoral level. In able-bodied ambulation, coronal stability during midstance is attained as the abductors of
the stance limb stabilize the pelvis, preventing it from dropping and ultimately
assisting swing phase clearance. This
mechanism is compromised in users of
transfemoral prostheses because the amputation often severs the distal attachment of the abductor musculature. As a
consequence, the weakened hip musculature and shortened femur are unable
to obtain adequate stabilization against
the lateral wall of the prosthetic socket
to control the drop of the pelvis. Lacking
this ability, patients frequently compensate by actively bending their trunk laterally over the prosthesis during stance.
This action serves to elevate the contralateral pelvis, facilitating swing phase
clearance. It also positions the center of
mass closer to the prosthetic foot, reducing the loads experienced in the distal
lateral region of the prosthetic socket.
Assuming a well-fitting socket in
which loads are born down the lateral
shaft of the femur rather than its distal
edge, with proper training many transfemoral prostheses users can learn to
shift their weight at their hips rather
than at their trunk to restore a more
balanced gait. However, for individuals
with shorter residual limbs or weak hip
abductors, some degree of lateral trunk
bending may be inevitable.
Excessive Heel Rise
The swing phase heel rise (swing phase
knee flexion) observed in the prosthesis
should generally match that observed
in the contralateral limb. Heel rise generally increases at faster gait speeds.
Hydraulic knee cylinders represent a
well-established means of regulating
the amount of heel rise because greater speeds will create greater hydraulic
resistance to knee flexion. If available,
changes to hydraulic swing resistance
can be used to match the heel rise of
the prosthesis to that of the sound limb.
An alternative strategy is seen in
friction-based knee systems. In these
knee designs, the amount of heel rise
observed in the prosthesis can be modestly adjusted by increasing or decreasing the friction settings about the knee
joint. However, these friction settings
will not adapt to changes in velocity;
therefore, increased walking speeds
yield a greater amount of heel rise. These
types of knees are generally reserved for
single-speed walkers because the friction resistance can be set to the patient’s
self-selected walking speed.
Excessive Terminal Impact
Frequently, patients prefer to experience a “terminal impact” at the end of
swing in which the prosthesis reaches
full extension before the acceptance
of bodyweight. This impact, although
unsightly and inconsistent with the
behavior of the contralateral knee,
provides the users with a sense of certainty that the prosthesis is in a stable
position beneath them. The amount of
impact preferred will vary from patient
to patient depending on walking experience and confidence in the prosthesis.
Just as mechanisms exist to modulate
the amount of knee flexion observed
in early swing, similar mechanical and
hydraulic mechanisms exist to control
the rate and amount of knee extension
observed in late swing. Inadequate
swing phase resistance or excessive
extension assist can cause excessive
terminal impact. Precise adjustments
are often required to balance control of
knee flexion in early swing with knee
extension in late swing.
Whips
Ideally, the prosthetic knee joint should
track within the line of progression as
it flexes and extends through the swing
phase. Deviations to this ideal are common and are described as whips. A prosthetic knee joint that is set in excessive
internal rotation creates a lateral whip in
which the rising heel deviates laterally
at the beginning of swing. In contrast,
a knee joint set in excessive external rotation creates a medial whip in which
the rising heel deviates medially. Visible whips are often the product of poor
prosthetic alignment. Alternatively, a
prosthesis donned in relative internal
or external rotation will also create a
visible whip. This situation can occur
in a newer prosthesis user who is still
learning how to properly don his or her
device, or as an intentional effort by
the user to increase the comfort of the
prosthesis by changing the orientation
of the brim. As previously described,
rotational instabilities are a common
problem for transfemoral prostheses
users because of the fleshy nature of
the limbs and the lack of supporting
bony structures within the socket. As
with foot rotation, whips also can be
the product of a poorly fitting socket.
Circumduction
The term circumduction is used to describe a pattern of hip motion in which
flexion is coupled with abduction to
attain swing phase clearance. There
are several causes that can precipitate
this compensation. A patient who lacks
confidence in the stability of his or her
prosthetic knee, whether because of
© 2016 American Academy of Orthopaedic Surgeons Atlas of Amputations and Limb Deciencies, Fourth Edition
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Section 1: General Topics
inexperience or unstable alignment,
may prefer a gait that utilizes hip circumduction because less flexion of the
prosthetic knee is required. Alternatively, if the prosthesis is too long, hip
circumduction may aid in attaining
swing phase clearance. Less frequently,
certain knee settings may be at fault,
including excessive hydraulic resistance
to swing flexion, excessive constant friction settings, or an excessive extension
assist mechanism. As with many other
transfemoral gait deviations, circumduction should be identified and addressed
early in the rehabilitation process because it often can become an established
compensation strategy.
Vaulting
Much like circumduction, vaulting
represents an alternative strategy used
to ensure swing phase clearance. As
was previously described in the transtibial section, any prosthetic deviation
that lengthens the prosthesis (excessive plantar flexion, prosthetic build
height, or poor suspension) can create a scenario where vaulting on the
contralateral side is needed to attain
swing phase clearance. The deviation
is common at the transfemoral level
because prostheses users lack voluntary control of knee flexion to ensure
adequate clearance. Because vaulting
and circumduction are complimentary
compensations, they often share underlying causes.
Instrumented Components
Components that are instrumented to
record socket reaction moments can assist practitioners in making alignment
decisions, and good agreement has been
found between alignment using an instrumented component and traditional
methods.26 Because of the similarity
with alignments achieved using conventional methods, the instrumented
component may be most appropriate
for challenging cases or when alignment is performed by less experienced
prosthetists.
Video Assessment
Advances in hardware and software
have resulted in high-definition video
recording technology that is readily accessible to most clinicians. Use of high
quality video (with adequate lighting
and correct camera placement) has been
shown to improve reliability of observational gait assessment.27 A software
program with analysis tools has been
shown to increase interrater reliability when assessing patients with neuromuscular disorders, and a similar
benefit may exist when assessing the
gait of prosthesis users.28 Unassisted observational gait assessment and
assessment enhanced by the use of a
software program has been shown to
allow reliable determination of initial
contact and foot-off during prosthetic
gait, indicating that both techniques
are useful for assessing temporal and
spatial parameters.
29
Prosthetic Observational
Gait Score
The Prosthetic Observational Gait Score
(a modification of the Edinburgh Gait
Score) was developed to aid prosthetists
during observational gait assessment. As
with most gait scores, the intraobserver
reliability of the Prosthetic Observational Gait Score is greater than the interobserver reliability30 (Figure 1).
Summary
The gait deviations commonly observed
with transradial and transfemoral prostheses often have a number of potential
causes. Assessment and optimization
of the gait of patients with lower limb
prostheses is a qualitative clinical task,
requiring close collaboration between
the patient, prosthetist, and other members of the rehabilitation team. Adopting
a methodic approach to dynamic alignment, using a structured assessment
tool, and incorporating video assessment can aid prosthetists in achieving
an acceptable alignment that minimizes
gait deviations and supports the activity
level of the patient.
Atlas of Amputations and Limb Deciencies, Fourth Edition © 2016 American Academy of Orthopaedic Surgeons
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Chapter 7: Clinical Considerations of Observational Gait Analysis
Figure 1
et al: Repeatability of a new observational gait score for unilateral lower limb amputees. Gait Posture 2010;32[1]:39-45.)
Chart for determining the Prosthetic Observational Gait Score. (Reproduced with permission from Hillman SJ, Donald SC, Herman J,
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