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Ординатура / Хирургия / Библиотека им академика М.И. Перельмана / Книга_921_Библиотеки_им_академика_М_И_Перельмана

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Section 1: General Topics
Figure 3
across the gait cycle (0% to 100%) during walking. The black solid line represents group mean data for normal, intact individuals without limb loss. The black dashed line represents group mean data for a passive (hydraulic) prosthetic knee. The red dashed line represents group mean data for a microprocessor-controlled prosthetic knee. The black dash-dot line represents group mean data for a passive prosthetic foot-ankle. The red dash­dot-dot line represents group mean data for another passive prosthetic foot-ankle. The green dotted line represents group mean data for a powered prosthetic foot-ankle. Conceptually, moments are eort and power is success.
normal intact ankle during gait (Figure 3, I). This remains a critical problem for
those with limb loss because the push­off power from the prosthetic side does not accelerate the body sufficiently to counteract the deceleration caused by the leading native limb at foot contact. This results in a change of momentum that is costly in both mechanical and metabolic terms for those with limb loss. A more effective prosthetic foot will also influence cosmesis, with the appearance of a more normal gait pattern and a less pronounced limp.
Atlas of Amputations and Limb Deciencies, Fourth Edition © 2016 American Academy of Orthopaedic Surgeons
72
Graphs illustrating sagittal plane motions; moments; and power of the hip (A, D, and G), knee (B, E, and H) and ankle (C, F, and I)
The sagittal motion of the ankle has been described as consisting of three “rocker” phases: the first rocker, from initial contact on the heel to foot flat with ankle plantar flexion; the second rocker, with the tibia advancing over the plantigrade foot in progressive dorsiflexion; and the third rocker, in which the ankle plantarflexes in late
50,51
stance.
The prosthetic foot-ankle system can emulate the first and second ankle rockers quite closely, but it does not actively plantarflex as much as the intact biologic ankle during the third
rocker. No prosthetic foot plantarflexes past neutral; the intact biologic ankle plantarflexes to 30° to 40° during the end of the stance phase of walking. Effi­cient amputee gait depends on the user’s ability to intuitively use the spring char­acteristics of the prosthetic foot to mimic the push-off forces of the biologic ankle observed during the late stance phase.
The sagittal moment profile of the foot during walking begins at near zero or slightly negative, indicating contact with the heel and a brief dorsiflexion moment. The moment crosses the axis
Chapter 6: Amputee Gait: Normal and Abnormal
and moves into a plantar flexion mo­ment as foot flat is achieved and the GRF vector passes directly through the ankle joint center. For an instant during mid­stance, all forces at the ankle are com­pressive, but as stance progresses, the sagittal moment becomes more positive, indicating substantial effort by the plan­tar flexors to restrain the shank segment and guide the ankle into controlled dor­siflexion. This might be considered an eccentric contraction of the triceps surae to restrain the forward progression of the tibia over the foot, but recent ultra­sound studies suggest that the fascicles of the gastrocnemius during walking are actually isometric and that most of the observed ankle dorsiflexion in mid­stance and terminal stance are the result of tendon stretch.52 However, a weak tri­ceps surae can result in a calcaneal gait or a crouch gait pattern. Compensation can be attempted by using the knee ex­tensors. As stance progresses, enough force is eventually generated to lift the heel and initiate plantar flexion in late stance and preswing. For the intact an­kle, small amounts of joint power are ab­sorbed as stance progresses, indicating an eccentric contraction of the plantar flexors, but in late stance and preswing, a substantial power generation peak oc­curs, indicating a concentric contraction by the plantar flexors to provide push­off energy and propel the body forward into the swing phase.
The subtalar and midtarsal joints that control the coronal plane motions of the foot relative to the ankle in the normal biologic lower limb have never been emulated with biomimetic accu­racy in prosthetic feet. Some prosthetic feet are less stiff in the coronal plane and can passively accommodate side slopes or leaning while turning. For some individuals, however, these feet feel somewhat unstable in the coronal plane. Personalized prosthetic prescrip­tions that consider the range of designs, user activities, and user functional performance goals are recommended.
Some individuals (especially children with limb loss) will choose a carbon fiber running blade as their prosthetic foot. This type of prosthesis is inher­ently unstable in stance, but can bend and flex to a large degree and provide much higher push-off power because it has no cosmetic foot cover or cush­ioned shoe. Younger children especially seem to value the trade-off, accepting instability while standing and enjoying the ability to run as fast as their peers during outdoor play. Running-specific prosthetic feet are not covered by the Centers for Medicare and Medicaid Ser­vices or private health insurers, but may be an appropriate prescription for some highly active prosthetic users, usually as a completely separate socket-pylon-foot system that can be used for running. Infants with limb loss who lack a knee have historically not been provided an articulating prosthetic knee until they begin to walk. However, recent research suggests that infants with transfemoral limb loss appear to benefit from a pros­thetic knee that can bend to accommo­date crawling.53 Such a knee also appears to improve mobility during play, as well as the achievement of the developmental milestones of pull-to-stand and walking in infants with limb loss.
The power generated in the sagittal plane by a prosthetic ankle (calculat­ed from computerized gait analysis) during late stance phase is usually less than 50% of that of the intact biologic ankle during walking,
3,18,21, 22,32,54
with no net power generation (only pow­ered and experimental passive spring prosthetic ankles can achieve normal power generation). The one exception to limited push-off power is the new, powered prosthetic ankle that can pro­vide plantar flexion power during walk-
54,55
ing.
Powered prosthetic ankles have tremendous potential, but currently are heavy, noisy, have limited battery life, are not reimbursed by the Centers for Medicare and Medicaid Services or private health insurers, and require the
user to successfully use increased push­off energy.54 A successful prototype of an MPC prosthetic foot uses the collision energy from initial contact and recycles this into propulsion energy during late
3,56,57
stance.
A few studies have shown improvements in ankle power genera­tion with these new MPC or powered prosthetic ankles, costs of walking appear unchanged,
3,54 -57
but the metabolic
3,54
suggesting that gait efficiency remains elevated for prosthetic users irrespective of the sophistication of the prosthetic component.
Prosthetic Foot Type and Ankle Kinematics and Kinetics
Prosthetic components are provided based on established criteria related to the patient’s functional level. The Medicare/Medicaid Functional Classi­fication Level58 (MFCL K-level) is rated on a scale from 0 to 4. The lower func­tioning levels (K0, K1, and K2) receive less advanced, less expensive prosthetic components (for example, solid ankle– cushioned heel [SACH] feet or passive hydraulic knees). The higher function­ing levels (K3 and K4) receive technolog­ically advanced prosthetic components (for example, energy storage and return feet or MPC elements). The physician establishes the individual’s K-level using observational gait analysis and patient input. Although ambulation attributes have been formally described,58 no reliable or valid method exists to pre­cisely determine K-level in a patient with limb loss. The Amputee Mobility Predictor (AMP)59 has some published validity, but the evidence was based on clinician ratings that have substan­tial errors. The 6-minute walk test60 is highly correlated with the AMP, takes less time to administer than the AMP, and is perhaps the most objective and least time- consuming functional level assessment available. A version of the AMP that is used for individuals with re­cent amputations (AMPnoPRO)59 can be
© 2016 American Academy of Orthopaedic Surgeons Atlas of Amputations and Limb Deciencies, Fourth Edition
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Section 1: General Topics
quite valuable in predicting successful functional level for an individual who has never used a prosthetic limb.
The functional level of the individual with limb loss is used to determine the type of prosthetic components that can be provided, and these components can ultimately influence the joint kinematics and kinetics of walking. Passive pros­thetic feet with advanced carbon fiber keels can flex and recoil substantially during late stance and preswing, but older SACH designs have wood or poly­ethylene keels with foam foot shells that compress during the late stance phase. SACH feet have a much lower power generation peak in late stance than car­bon fiber prosthetic foot designs,
21,22
and should be prescribed for those with low­er functional levels (K1 and K2). The degree of forefoot keel flexibility can be engineered to match the weight and walking speed of the individual, but rigorous data are still needed to inform the prescribing physician about the ap­propriate forefoot stiffness of specific models of prosthetic feet. The prescrip­tion of prosthetic feet is usually based on professional clinical experience, without using objective data that can be matched with a specific patient profile. A team approach with input from the user, the prosthetist, and the prescribing physi­cian is likely the most effective model of care in choosing the most cost-effective and mobility-empowering prosthetic components.
Knee Sagittal Kinematics
Normal Knee Motion
The sagittal kinematics of the intact bio­logic knee over the gait cycle begins with the knee in slight flexion at initial con­tact, flexes to approximately 15° (more at faster walking speeds) at approximately 25% of the gait cycle, and extends again to almost full extension late in the stance phase before beginning to flex again during preswing (Figure 3, B). At foot­off, the knee is in approximately 30° of flexion, continues to approximately 55°
in midswing, and extends until reaching full extension late in swing before ini­tiating slight flexion just before initial ground contact.
Transtibial Limb Loss (Retained Biologic Knee)
For those with transtibial limb loss, the preserved biologic knee typically rep­licates the sagittal plane motion of the intact biologic knee during walking, including a consistent, recognizable flexion wave during early stance. Most transtibial prosthetic users have intact knee extensors (quadriceps) and knee flexors (hamstrings) and normal motor function. The choice of prosthetic foot can influence the amount of extensor or flexor moments applied to the knee during walking, but most transtibial prosthetic users can manage the small discrepancies in knee motion that are in­duced by prosthetic feet. Most transtibial prosthetic users are able to walk with knee kinematics on their involved side similar to that of an intact biologic knee. If the normal functional performance of the biologic knee is compromised in some way in those with transtibial limb loss (for example, weakness, joint defor­mity, or motor nerve injury), the forefoot stiffness of the prosthetic foot might be increased to provide greater extensor moments in midstance, thus improving knee extension rather than a flex and recoil pattern to provide push-off power. This compromise between support and propulsion must be carefully considered for each individual.
The residual limb length of any trans­tibial amputation should be optimized, if possible, to make community ambu­lation more functional. If the amputa­tion results in a residual limb that is too short, control of the prosthesis during walking will require very high pressures at the residual limb–socket interface that will increase the risk of blisters, sores, and ulcers. If the residual limb is too long, the choice of prosthetic feet for the individual will be limited and
require difficult design and fabrication work by the prosthetist. Boyd amputa­tions or Syme ankle disarticulations that allow distal weight bearing are generally advantageous, but if they are excessively long they can limit prosthetic foot pre­scription options that provide the great­est flex and recoil during walking. Seven to 10 inches of clearance between the end of the residual limb and the floor allow the greatest range of possible pros­thetic components to meet the prosthetic user’s range of desired functional perfor­mance goals. These decisions regarding the amputation site are often driven by medical or biomechanical factors, and residual limb length optimization may not be possible for every patient. How­ever, the effects of residual limb length on pressure-to- moment relationships during ambulation and on prosthetic component choices should be consid­ered by the treating surgeon.
The choice of shoes by the prosthetic user is beyond the control of healthcare providers, but it can radically alter the kinematics and kinetics of the prosthet­ic limb and the compensatory mech­anisms of the retained biologic knee. A shoe with a higher heel will tend to incline the prosthetic limb forward and require additional knee extensor muscle activity to maintain appropriate knee extension. A few MPC feet currently on the market can accommodate different heel heights and can be set by the pros­thetic user whenever he or she changes shoes.
Transfemoral Limb Loss (Absent Biologic Knee)
Individuals with transfemoral limb loss must use a prosthetic knee joint to em­ulate the sagittal kinematics needed for walking. The prosthetic knees of indi­viduals with limb loss from transfemo­ral amputation or knee disarticulation usually lack sagittal plane flexion during early stance (Figure 3, B). The limited flexion during early stance occurs be­cause most prosthetic knees are unable
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Chapter 6: Amputee Gait: Normal and Abnormal
to flex eccentrically during the early portions of stance phase. Even users of MPC knees, which are designed to have this knee flexion wave in early stance, do not often exhibit a normal kinematic knee pattern.
61-63
The inability to walk with a normal kinematic knee pattern can be the result of a lack of trust in the knee by the user or an issue with knee alignment in the sagittal plane, or it can possibly be related to software parame­ters set by the prosthetist. The ability to achieve eccentric flexion in early stance phase in prosthetic knees has not been demonstrated convincingly.
24,61,64,65
MPC knees have demonstrated a decrease in knee hyperflexion (flex­ion greater than 60°) during the swing phase.61 This decrease makes achieving full knee extension before initial con­tact more likely at a range of different walking speeds, a key feature to avoid knee buckling and falls in individuals with transfemoral limb loss. Hydraulic or mechanical prosthetic knees usually exhibit knee hyperflexion in swing61 but can be adjusted to increase joint damp­ening to normalize the sagittal kinemat­ics of the prosthetic knee joint during swing. However, knee flexion can only be optimized for a specific flexion force and, therefore, a specific walking speed; the induced pendular mechanics of the prosthetic knee at faster or slower walking speed needs some dynamic dampening to accomplish the correct magnitude and timing of the peak flex­ion at these different speeds. For those individuals with demonstrated multiple walking speeds, an MPC knee can offer true functional and safety advantages because of this swing phase adapta­tion feature.61 Payers only reimburse an MPC knee if the patient is at level K3 or higher, uses multiple walking speeds, and can competently handle most com­munity environmental barriers, such as curbs, ramps, and stairs. Some individu als with lower functional levels (K2) can achieve multiple walking speeds (K3) when provided with an MPC knee.
24,62
In addition, there is some evidence that individuals at the K2 functional level can benefit from an MPC prosthetic knee that can dampen flexion moments to maintain stability during stumble re covery and possibly improve the safety of walking on ramps.
1
The shoe choice for a transfemoral prosthesis user has a more dramatic ef­fect on the kinematics and kinetics of walking than shoe choice for a trans­tibial prosthesis user. Shoes with in­creased heel height will tend to cause the prosthetic knee to buckle and collapse in an individual with a transfemoral amputation, increasing the risk of falls. Therefore, the range of possible shoe choices is more limited in transfemoral prosthesis users, although some MPC prosthetic feet permit the transfemoral amputee to adjust the neutral position of the ankle to accommodate different heel heights, allowing for a greater range of footwear choices. This is an important cosmetic and social inclusion issue for formal occasions (high-heeled shoes) or outdoor work activities (boots for man­ual labor) for prosthesis users.
Normal Knee Kinetics
The kinetic patterns of the knee have complex waveforms during walking but primarily provide support for the body during stance. Early stance often has a flexion moment even though the knee is near full extension, suggesting some stress on the posterior capsule because the knee must resist further extension (Figure 3, E). The sagittal knee moment quickly crosses the axis into an exten­sion moment, and substantial quad­riceps activity is needed to maintain upright stance despite external forces that would cause the knee to collapse.
Prosthetic Knee Kinetics
When an individual with a prosthetic
-
knee joint walks, the initial knee flexion moment generally locks the prosthetic knee in extension and it remains there throughout most of the stance phase.
This corresponds to the obvious lack of knee flexion during early stance ob­served in the sagittal knee motion of prosthetic knee users, even with MPC
-
knees designed to have knee flexion in early stance. As stance progresses, the flexion moment increases beyond the magnitude seen in the intact native knee, indicating substantial resistance to hyperextension by the prosthetic knee (Figure 3, E). In late stance, both normal and prosthetic knee moments have a brief extension moment just as knee flexion is initiated.
Hip Sagittal Kinematics
Sagittal hip motion is primarily sinu­soidal during walking. Stance begins with approximately 40° of flexion at initial contact, with the hip extending to neutral at midstance and moving into approximately 5° to 20° of extension during terminal stance, with greater hip extension at longer stride lengths (faster walking speeds). The hip begins to flex before foot-off and moves through neutral during midswing until the hip reaches full flexion of approximately 40° during the late swing phase.
An individual who lacks a knee joint must use the femoral residual limb to apply pressure to the interior of the prosthetic socket to simultane­ously achieve the sinusoidal hip motion during gait and control the prosthet­ic knee joint. Because the hamstrings no longer function as hip extensors for most transfemoral amputees, the gluteal muscles must provide the hip extensor forces during the first half of stance and the iliopsoas must provide the hip flexor forces during late stance and swing. Sagittal hip motion in indi­viduals with transfemoral limb loss is often shifted toward flexion and has a somewhat reduced arc of sagittal mo­tion, primarily because of a lack of full extension in late stance (Figure 3, A). The lack of push-off power from the prosthetic foot in late stance results in lower energy transferred to the limb to
© 2016 American Academy of Orthopaedic Surgeons Atlas of Amputations and Limb Deciencies, Fourth Edition
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Section 1: General Topics
initiate swing in the transfemoral pros­thesis user. Greatly increased hip flexor muscle activity can improve the range of motion of the hip in individuals with transfemoral limb loss, but generally the increased pressures in the distal ante­rior region of the residual limb–socket interface are uncomfortable or perhaps injurious to the tissue over time. The three basic mechanisms to advance the limb into swing during walking are an­kle push-off energy transferred to the tibial and femoral segments (distal to proximal strategy), hip flexor muscle activity to accelerate the thigh into flexion and initiate swing (proximal to distal strategy), and deceleration of the pelvis and trunk segments to transfer momentum to the training limb on con­tact with the lead limb (proximal to dis­tal strategy). Individuals without lower limb loss can manage all three methods with some form of energy and control optimization,66 but the range of step-to­step variance and acceptable solutions to the balance between the forces that initiate swing is not completely under­stood. Of all the tasks in human gait, swing initiation is likely less important than managing the step-to-step transi­tions during double support without wasting mechanical energy and there­fore increasing metabolic cost.
46
An individual with a hip disarticu­lation uses pelvic tilt in the sagittal plane to facilitate the motion of the missing thigh segment during ambu­lation and must learn a complex set of trunk maneuvers to maintain forward progress during walking. As a conse­quence, low back pain is a frequent symptom in individuals with more proximal limb loss.
67-71
Individuals with a short femoral residual limb segment produce hip and pelvic motions during walking that are similar to those of in­dividuals with a hip disarticulation; this makes successful community am­bulation more difficult. Every surgical and medical effort should be made to maintain an adequate femoral residual
limb segment after limb loss. Without adequate length, the pressures placed on the tissues of the residual limb are too high to be tolerated during longer periods of walking. The hip extensors and flexors are at an extreme mechan­ical disadvantage if the femoral residu­al limb is too short. Many individuals with hip disarticulation or a short fem­oral residual limb will need alternative mobility solutions, such as a scooter, wheelchair, or Lofstrand crutches for some portion of their daily activities; this is especially true as an individual ages.
Hip Sagittal Kinetics
Hip kinetics in individuals with limb loss at the knee and higher levels reflect the increased effort of the hip in mov­ing the prosthetic knee and ankle joints. The early stance hip extension moments (gluteal muscle activation) in the intact hip joint are similar to those in indi­viduals with transfemoral limb loss. As stance progresses, individuals with more proximal limb loss must apply greater hip flexion moments (iliopsoas muscle activation) to initiate swing phase knee flexion and limb advancement because they lack the ankle push-off power that can transfer energy to the swing limb.72 The action can be taxing, with peak sagittal power at the hip more than double that of normal, intact gait. This can contribute to increased pressure at the residual limb–socket interface near the distal anterior region, a loca­tion of frequent skin irritation for some transfemoral amputees. Compensatory actions to advance the prosthetic limb into swing are often observed visually, including “hip-hiking,” or Trendelen burg gait with circumduction. (Trende­lenburg gait or lateral trunk lean over the stance limb is more often related to reducing coronal moments about the hip and medial- distal and proximal-lateral socket pressure discomfort in individu­als with transfemoral limb loss.)
Ground Reaction Forces
During the stance phase of gait, an in­teraction between the individual and the ground results in force being applied to the distal foot (Figure 4). The reac­tion force measured during computer­ized gait analysis is the GRF. The GRF has three components that aid in for­ward motion during walking: anterior­posterior, medial-lateral, and vertical. The largest force during walking is the vertical GRF. The vertical GRF is a bi­modal curve with each peak reaching approximately 120% of body mass in healthy walking. The first peak in the vertical ground reaction curve measures the weight acceptance of the limb, and the second peak measures the propul­sive force needed to move the body forward. Any disturbance in the timing or magnitude of these GRF peaks indi­cates a kinematic deviation from normal walking patterns.
Individuals with limb loss generally have similar GRF patterns, but close examination reveals typical deviations. The late stance vertical GRF peak is of­ten lower in amputees than individuals without limb loss, due in part to the lack of active push-off power from almost all prosthetic feet. Typically, slower walk­ing speeds result in a less-pronounced bimodal pattern for the vertical GRF in individuals with limb loss. Wider foot placement also results in somewhat greater medial-lateral force pattern, but the magnitude remains relatively low.
Activities of Daily Living and Mobility
Data from computerized gait analyses specifically focus on walking straight
-
ahead and can help in understanding a prosthesis user’s ambulation challenges while walking straight ahead. Sagittal plane joint motions and forces provide most of the motion and allow an individ­ual to walk in a straight line. However, observations of community ambulation and function suggest that most func­tional human locomotion involves a few
Atlas of Amputations and Limb Deciencies, Fourth Edition © 2016 American Academy of Orthopaedic Surgeons
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Chapter 6: Amputee Gait: Normal and Abnormal
Figure 4
the gait cycle (0%–100%) for a normal, intact individual without lower limb loss (black solid line) and a prosthet ic device user with a transtib ial amputation (red dash- dot-dot line). Note the reduced peak vertical force in the prosthetic device user ’s data during late stance, suggesting exing of the forefoot keel of the prosthetic foot.
steps in a row before stopping or turn-
73,74
ing. for daily living involves rising from a seated posture, initiating gait, accelerat­ing, turning, decelerating, terminating gait, climbing stairs, maneuvering over and around obstacles, and returning to a standing or seated posture. This is likely a function of western urban architec­ture, but 4 ± 1 steps is the most common walking bout (number of steps before stopping), accounting for approximately 15% of all bouts for a wide range of in­dividuals with differing activity levels.
Both sedentary and active individu­als show a substantial bias toward short walking bouts; 40% of all walking bouts consist of 12 ± 1 steps or fewer in a row, and 75% of all walking bouts consist of 40 ± 1 steps or fewer in a row.75 In addition, short periods without ambu-
Line graph illustrating vertical ground reaction force during walking plotted across
only once per day but for some individ-
Much of the mobility required
uals can include 8% to 20% of the total daily steps.75 Because of the typical chal­lenges for everyday activities, stability and maneuverability of the individual with limb loss to walk short distances with competence appears more crucial than energy efficiency and gait econo­my, although the latter is still impor­tant. For children with limb loss, the ability to initiate running suddenly to keep up with friends appears more crucial than stability. Given the choice,
75
many children opt for a running limb as their primary prosthesis, even if it results in more falls and makes stand­ing still more difficult. Because most development in children is play-based, enabling high-energy movements seems an important goal in prescribing pros-
thetic components. lation occur frequently throughout the day. Long-duration walking behavior for exercise or long-distance transpor­tation does not occur often, even for in­dividuals who exercise regularly. These long-duration exercise bouts may occur
Summary
Computerized gait analysis can pro-
vide comprehensive information on the
joint motions and forces during walk-
ing for individuals with limb loss, but
additional ambulatory challenges exist within the community for prosthesis users. A comprehensive evaluation of mobility is recommended to maximize functional status in prosthesis users with lower limb loss. When determining the effect of a prosthesis on gait mechan­ics, it is important to examine the effect across the entire lower limb. The effect of a prosthesis is not isolated to a single joint; therefore, these alterations need to be considered when determining the optimal treatment plan for each patient. Computerized three- dimensional gait analysis can document the compensa­tory kinematics and kinetics in indi­viduals with lower limb loss, and it can inform clinical decision making when prescribing prosthetic components and evaluating the outcomes of surgical in­terventions. Computerized gait analy­sis is also the primary method used in scientific research into the comparative effectiveness of prosthetic component treatment choices. Understanding this literature can improve an orthopaedic surgeon’s ability to provide clinical care for individuals with limb loss and can be essential in helping the surgeon under­stand the scientific basis for the devel­opment of novel prosthetic components.
References
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Section 1: General Topics
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Chapter 7
Clinical Considerations of Observational Gait Analysis
John T. Brinkmann, MA, CPO/L, FAAOP Phillip M. Stevens, MEd, CPO, FAAOP
Abstract
It is helpful to understand the clinical concepts related to the alignment of lower limb pros­theses and observational gait assessment along with principles related to the orientation of prosthetic components and the resulting gait patterns. To achieve acceptable alignment and minimize gait deviations in patients with transtibial and transfemoral amputations, the prosthetist can adopt a methodic approach to dynamic alignment that may include structured assessment tools and incorporate video assessment.
Keywords: gait assessment; prosthetic gait deviations
Introduction
The overall goal of rehabilitation after lower limb amputation is to support a level of function commensurate with the individual’s functional capabilities before amputation. In terms of walking ability, the goal is to match as closely as possible the patient’s pre-amputation kinetic and kinematic gait parameters. However, even after successful rehabil­itation, practitioners should expect that
inappropriate distribution of forces on the residual limb, increased loading of the contralateral limb, and increased energy expenditure.
3-5
The long-term altered biomechanics observed in the gait of prosthesis users can contrib­ute to the development of orthopaedic problems, including osteoarthritis.
6,7
Gait deviations should be normalized as much as possible to minimize these deleterious effects.
structural asymmetries caused by the amputation will result in kinetic and ki­nematic asymmetries.
1,2
Gait deviations are observed and addressed by applying established clinical principles and pro­fessional judgment to arrive at the most appropriate gait pattern for each indi­vidual. A study guide is included at the end of this chapter to identify common gait deviations and causes.
Observational Gait Analysis
Because practitioners in most clinical settings do not have access to three­dimensional instrumented gait analy­sis, they rely on unassisted observation as the primary method for identifying pathologic gait patterns. Several lim­itations are inherent in observational assessment. First, many factors that influence a user’s gait are not directly
Consequences of Gait Deviations
Prosthetic gait that deviates from nor­mal parameters has detrimental phys­ical and functional effects, including
Mr. Brinkmann is a faculty member at Northwestern University’s Prosthetic and Orthotic Center and serves as a board member, owner, ocer, or committee member of the American Academy of Orthotists and Prosthetists. Mr. Stevens is an employee of the Hanger Clinic and serves as a board member, owne r, o cer, or committee member of the American Academy of O rthotists and P rosthetists.
observable. For example, the pressure of the residual limb against the socket and the corresponding joint moments caused by those pressures can only be observed using equipment and methods
not available in most clinical settings. Second, observational gait assessment has been demonstrated to have limited validity and reliability for gait-related events in neuromuscular and musculo­skeletal pathologies.
8,9
Studies focused specifically on patients with lower limb prostheses have confirmed this limita-
10,11
tion.
However, as the prosthetic prac titioner is currently limited by available resources and techniques to achieve an optimally fitting and functioning pros­thesis, observational gait assessment remains the primary strategy used by clinicians when assessing the gait of prosthesis users at the initial fitting and subsequent appointments.
Prosthetic Alignment
Prosthetic components are assembled in a particular spatial relationship to each other, commonly referred to as the alignment of the prosthesis. The align­ment process typically involves three distinct stages. During bench alignment, components are assembled and attached to the socket based on traditional pro­tocols, the manufacturers’ recommen­dations, and the clinical judgment of the prosthetist. During the static align­ment stage, adjustments are performed during weight bearing without ambu­lation, with a focus on socket fit and gross alignment. Dynamic alignment involves observation of the ambulating patient and optimization of the spatial relationship of the components.
One of the key elements of dynamic alignment involves using observational assessment and user feedback to detect and reduce common patterns of patho­logic gait (deviations) that indicate the need to change the spatial orientation of
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