Gait Dysfunction in Neurologic Conditions

Objectives

• Discuss Motor Control of gait.

• Discuss the impact of neurologic dysfunction on gait.

• Introduce Outcome Measures for the assessment of various elements of gait.

• Apply subtasks of gait and the hypothesis-driven clinical decision-making process to the assessment of gait.

Phases of Gait

• Bipedal Gait: Characterized by limbs moving in a rhythmical, symmetrical, alternating pattern.

• Motor Modules (Muscle Synergies): Coordinated patterns of muscle activity essential for functional tasks like gait.

Fun Facts of Typical Gait

• During comfortable walking speed, gait involves $60\%$ in stance and $40\%$ in swing. This proportion evens out as walking speed increases.

• An individual's most comfortable walking speed is also their most energy-efficient speed.

• The average gait speed for healthy adults is approximately $1.46\text{ m/s}$ (with a cadence of $1.9\text{ steps per second}$ and a step length of $76.3\text{ cm}$).

• The average steps per minute are $110-115$.

• Walking speed is considered the "6th Vital Sign" due to its strong correlation with functional ability, fall risk, and mortality in adults.

Walking Subtasks and Muscle Synergies

• Motor modules combine the co-activation of multiple muscles to achieve specific gait subtasks:

  • Bodyweight Support

    • Muscles involved: Glutes, Quads, PF (Plantar Flexors), PLTA (Posterior/Lateral Tibialis Anterior), Ham (Hamstrings).

  • Propulsion

    • Muscles involved: Quad, PF, PLTA, Ham, Glute.

  • Limb Advancement

    • Muscles involved: Glutes, Quad, PF, PL, Ham, Glute.

• These subtasks also involve:

  • Spatial Coordination: Relates to the synergy composition.

  • Temporal Coordination: Relates to the synergy timing.

Task Requirements of Gait

• Progression: Involves rhythmical patterns of muscle activation that successfully initiate, continue, and terminate body movement.

• Stability: Requires coordination of motor and sensory systems for body orientation and stability to maintain the Center of Mass (COM) over a moving Base of Support (BOS).

• Adaptation: Refers to the flexibility of the system to adjust gait to changing task and environmental demands.

Functional Components of Gait Subtasks (Adapted from Moore KL, 2017)

• Body Weight Support

  • Stability: Securing the limb for weight acceptance, providing vertical stabilizing forces against gravity, and shock absorption.

• Propulsion

  • Progression: Generating horizontal force to propel the body forward.

• Limb Advancement

  • Progression: Advancing the swing leg.

  • Stability: Repositioning the limb in preparation for weight acceptance.

  • Adaptability: Avoiding obstacles.

Motor Control of Walking

• Motor Abundance: The motor system possesses more degrees of freedom than necessary to achieve a specific outcome. This enables the nervous system to generate multiple equally effective movement solutions.

• Motor Variability: Refers to variations in movement patterns and muscle activation even when performing the same action. This allows the motor system to be adaptable to new or unexpected challenges.

• Distinction: Motor abundance represents the available resources for movement, while motor variability signifies the different ways these resources are actually used during movement.

Sensory and Cognitive Systems' Impacts on Gait

• Visual Processing:

  • Essential for visual object recognition to move effectively in space (identifying surface/object and its relation to the person).

  • Important for body alignment with reference to gravity and the environment.

  • Visual flow input helps modulate speed and stepping frequency.

• Somatosensation:

  • Influences stepping frequency.

  • Triggers the onset of swing (afferent input from hip flexors when stretched).

  • Provides inputs crucial for postural control and gait adaptation, especially on varied surfaces.

  • Contributes to interlimb coordination (rhythmical arm and leg movements).

• Cognition:

  • Critical for gait initiation and gait adaptation in complex environments.

Impact of Neurologic Dysfunction on Gait

• Walking dysfunction affects over $80\%$ of stroke survivors.

• Although most individuals regain some level of ambulation, hemiparetic gait post-stroke is typically slow, metabolically demanding, and unstable.

• The level of ambulation following a stroke is a long-term predictor of participation and disability.

Impact of Stroke on Motor Control

• Individuals post-stroke often exhibit reduced isolated control and atypical synergies/coupling of muscle groups.

• This results in a merging of motor modules with limited variability in movement, leading to decreased speed, stability, and efficiency in gait (as per J NeuroEngineering Rehabil 18, 58 (2021)).

Hemiparetic Gait Post-Stroke

• Characterized by a combination of dysfunctions:

  • Motor System Dysfunction

  • Sensory System Dysfunction

  • Visual System Dysfunction

Motor System Dysfunction

• Impaired Cortical Drive:

  • Leads to impaired or disordered force production.

  • Causes abnormal coupling of muscles.

  • Results in mass patterns of movement (abnormal synergy) and decreased selective/isolated control.

  • Common coactivation/abnormal synergistic patterns occur, contributing to decreased variability of movement.

  • Associated with reduced gait speed, efficiency, and stability.

Motor Disorders: Paresis/Force Production/Weakness

• Impacts on Bodyweight Support/Stance Phase:

  • Equinovarus foot position at initial contact:

    • Limits dorsiflexion (DF) in midstance, preventing tibial progression.

    • Can contribute to knee hyperextension in mid and terminal stance.

    • Impairs propulsion and gait speed.

    • Provides an unstable surface in stance (Campanini I. Front Neuro 2020; Esquenazi A. Toxicon. 2023).

  • Quadriceps weakness:

    • Results in decreased knee control during loading and midstance, leading to knee hyperextension or buckling.

  • Glut/Hip Extensor weakness:

    • Causes decreased gait speed and a forward trunk lean in stance.

  • Glut/Hip Abductor weakness:

    • Leads to a Trendelenberg gait with a lateral trunk lean; decreases the Base of Support (BOS).

• Impacts on Propulsion/Plantarflexors:

  • Reduced central drive to plantarflexors (PF) contributes to impaired propulsion, resulting in slower walking speeds and increased energy cost of walking

  • Trail limb angle (stretch to hip flexors) plays a significant role.

  • Decreased paretic propulsion results in slower gait speed and less walking distance, potentially limiting community mobility

• Impacts on Limb Advancement/Swing Phase:

  • Hip flexion (@ initiation of swing):

    • Decreased knee flexion in pre-swing (propulsion) with reduced toe clearance.

    • Results in shortened step length and altered foot position at heel strike (impacting postural control).

    • Compensatory strategies include posterior pelvic tilt and activation of abdominals, circumduction with hip hike, and vaulting over the contralateral limb.

    • These compensatory movements are also related to impaired propulsion and trail limb angle.

  • Tibialis Anterior weakness:

    • Decreased activation of TA during limb advancement contributes to tripping and falling (impacting adaptability).

    • Can affect progression (gait speed) and contribute to decreased efficiency.

Motor Disorders: Impaired Coordination

• Impaired Segmental Coordination:

  • Inability to control the timing and scaling of movement, leading to an Ataxic gait pattern.

  • Characterized by varied BOS, irregular stepping, and a staggered gait.

  • Often involves impaired coupling of arm and leg movements.

  • More common in pathologies of the cerebellum and basal ganglia.

• Abnormal Phasing of Multi-joint Movements:

  • Includes co-activation of agonists and antagonists.

  • The impact on mobility is more significant with increased speed of movement; movements may be more controlled at slower speeds or during single-joint actions.

Sensory Dysfunction

• Absent or Impaired Sensory Input: Affects information regarding body position in space and surface navigation.

• Consequences:

  • Slower gait speed.

  • Impaired postural control and adaptability, which worsens on irregular terrain.

  • Ataxic gait pattern.

  • Decreased or irregular stance time and step length.

  • Gait may improve with increased visual inputs and decline when visual cues are limited.

Visual Dysfunction

• Impaired or Inaccurate Visual Cues:

  • Impacts the gait movement itself and the ability to navigate/interpret the environment.

  • Leads to impaired adaptability.

  • Results in impaired obstacle avoidance.

  • Hinders the ability to modulate speed and stepping.

Cognitive Dysfunction

• Can encompass issues with memory, attention, or executive function.

• Consequences:

  • Impaired gait initiation, adaptation, and navigation.

  • Slower gait speed.

  • Impaired dual-task ability (the capacity to walk while attention is divided to another task).

Gait Assessment

• Observation Gait Analysis

• Functional Independence Measure (FIM) - Note: Retired in 2019.

• 10 Meter Walk Test

• 6 Minute Walk Test

• Functional Gait Assessment

Observation Gait Assessment

• Procedure:

  • Includes observations with and without an assistive device or orthosis.

  • Needs to be observed in both the frontal and sagittal planes.

  • Focus on:

    • Identifying the environment, surface, and level of assistance needed.

    • Observing posture and symmetry of the gait pattern.

    • Describing Lower Extremity (LE) kinematics from a proximal to distal pattern in each phase of gait.

    • Hypothesizing underlying impairments in body structure and function contributing to gait dysfunction.

• Reliability: Video recording can significantly improve the reliability of observational analysis of gait.

Observation Gait Analysis – Normative Data (Kinematics and Muscle Activity)

• Initial Contact:

  • Ankle: Neutral $0^\circ$.

  • Knee: Appears extended.

  • Hip: $20^\circ$ flexion; Hip extensors and abductors active.

• Loading Response:

  • Ankle: $5^\circ$ Plantarflexion (PF); Eccentric Pretibials.

  • Knee: $20^\circ$ flexion; Eccentric Quads.

  • Hip: $20^\circ$ flexion; Hip extensors and abductors active.

• Mid Stance:

  • Ankle: $10^\circ$ Dorsiflexion (DF); Concentric Gastrocnemius (GS).

  • Knee: Appears extended; Concentric Quads.

  • Hip: Neutral; some hamstring and abductor activity.

• Terminal Stance:

  • Ankle: $15^\circ$ DF; Concentric GS.

  • Knee: Appears extended; Eccentric Quads.

  • Hip: $20^\circ$ extension; assistance from rectus femoris.

• Pre Swing:

  • Ankle: $5^\circ$ PF; Concentric GS.

  • Knee: Concentric Hamstrings to achieve $40^\circ$ flexion; Inactive Quadriceps.

  • Hip: $10^\circ$ extension; minimal iliacus and quads activity.

• Initial Swing:

  • Ankle: Neutral $0^\circ$; Concentric Pretibials.

  • Knee: $60^\circ$ flexion; Concentric Gracilis.

  • Hip: $15^\circ$ flexion; some iliacus and quads activity.

• Mid Swing:

  • Ankle: Neutral $0^\circ$; Concentric Pretibials.

  • Knee: $25^\circ$ flexion; Eccentric Hamstring.

  • Hip: $25^\circ$ flexion; Hamstring activity.

• Terminal Swing:

  • Ankle: Neutral $0^\circ$; Concentric Pretibials.

  • Knee: Appears extended; Eccentric Hamstring; Concentric Quads.

  • Hip: $20^\circ$ flexion; Hamstring activity.

Common Gait Deviations in Hemiparetic Gait and Possible Impairments

• Initial Contact/Loading:

  • Gait Deviations: Decreased heel strike, foot slap, equinovarus foot position.

  • Possible Impairments: Weakness of pretibials, decreased DF PROM (Passive Range of Motion), impaired somatosensation.

• Midstance/Terminal Stance:

  • Gait Deviations: Positive Trendelenberg sign, decreased tibial progression, knee hyperextension or flexion, shortened step length, decreased trail limb position.

  • Possible Impairments: Weakness of plantarflexors, hip extensors/abductors, quadriceps; decreased DF, hip extension PROM; impaired somatosensation.

• Preswing:

  • Gait Deviations: Decreased push-off.

  • Possible Impairments: Weakness of plantarflexors; impaired somatosensation.

• Swing Phase:

  • Gait Deviations: Hip hike, circumduction, vaulting, decreased knee flexion, decreased peak DF.

  • Possible Impairments: Weakness of pretibials > hip flexors > quadriceps; decreased DF ROM; impaired sensation.

Alternative Methods of Gait Analysis

• Kinematic Quantitative Gait Analysis: Measures spatial and temporal variables of gait.

  • Variables: Speed, cadence, stride/step length and time, double limb support, stance and swing time, acceleration, BOS width.

  • Methods: Capture patient footprints, use of a gait grid, accelerometers, commercial instrumented systems, footswitches, video-based motion analysis, EMG.

• Kinetic Gait Analysis: Analyzes forces involved in gait.

  • Variables: Ground reaction forces, pressure forces, center of pressure and torque.

  • Methods: Force plates, dynamometers.

Functional Independence Measure (FIM): Retired

• Description: An $18$-item observational measure assessing a patient's disability level and the amount of assistance required for ADLs.

• Items: Includes self-care, sphincter control, transfers, locomotion, communication, and social cognition.

• Usage: Used exclusively in Rehabilitation settings.

10 Meter Walk Test

• Purpose: Standardized assessment of both comfortable and fast walking speed in meters/second over a short distance.

• Administration:

  • Patient can use bracing or assistive devices.

  • Assist for safety can be provided, but if it affects forward propulsion speed, a score of "$0$" meters is documented.

  • If assist or devices are used, the assessment should not be compared to a later assessment completed with different levels of assist or devices.

• Normative Data/Interpretation:

  • <0.4\text{ m/s}: Household ambulators.

  • $0.4-0.8\text{ m/s}$: Limited community ambulators.

  • >0.8\text{ m/s}: Community ambulators.

• Measurement of Detectable Change (MDC):

  • Acute: $0.11\text{ m/s}$.

  • Chronic (>6\text{ months} comfortable speed): $0.18\text{ m/s}$.

• Minimally Clinically Important Difference (MCID):

  • Subacute (<45\text{ days}): $0.16\text{ m/s}$.

Functional Gait Assessment (FGA)

• Purpose: Assesses postural stability during walking and an individual’s ability to perform multiple motor tasks while walking.

• Background: A revised version of the Dynamic Gait Index.

• Administration:

  • Standardized administration and scoring of $10$ items.

  • Individuals need to be able to walk without assistance from another person, but can use a device or bracing.

• Cut-off for Older Adults: <22/30 indicates a risk for falls.

• MDC: $4.2\text{ pts}$ or $14.1\%$ change (applicable for acute, subacute, and chronic stroke).

6 Minute Walk Test (6MWT)

• Purpose: A sub-maximal exercise test used to assess walking endurance and aerobic capacity.

• Administration:

  • Standardized administration including instructions and course setup.

  • Patient can use bracing or assistive devices.

  • Patient can stand and rest, but if they sit, the assessment ends.

  • Assist for safety can be provided, but if it affects forward propulsion speed, a score of "$0$" meters is documented.

  • If assist or devices are used, the assessment should not be compared to a later assessment completed with different levels of assist or devices.

• Predictive Value: Can be more predictive of potential for community mobility than the 10 MWT.

• Normative Data for Community Dwelling Elders:

  • Distance walked >205\text{ m} discriminated between home and limited community ambulators.

  • Distance walked >288\text{ m} discriminated between limited and unlimited community ambulators.

• MDC:

  • Subacute ($30-150\text{ days}$ post-stroke): $61.0\text{ m}$.

• MCID:

  • Chronic (>6\text{ months}): $34.4\text{ m}$.

Combined Set up For All! (Environmental Setup for Core Measures)

• Total Path Length: $12\text{ meters}$ for the 6MWT.

• Cones for 6MWT Turnaround: Placed at $49\text{ inches}$ from the ends of the $12\text{-meter}$ path.

• 10mWT Start/Stop: $6\text{ meters}$ segment within the path.

• FGA Items: Performed in a $20\text{-foot}$ segment with a $12\text{-inch}$ width (cones at $2\text{ meters}$ from each end).