Question

Consider a complete loss of function in the gastroc/soleus muscle only. Which gait phases/periods would be impacted and how? Provide your rationale.

Answer 1

Human gait depends on a complex interplay of major parts of the nervous, musculoskeletal and cardiorespiratory systems.

• The individual gait pattern is influenced by age, personality, mood and sociocultural factors.
• The preferred walking speed in older adults is a sensitive marker of general health and survival.
• Safe walking requires intact cognition and executive control.
• Gait disorders lead to a loss of personal freedom, falls and injuries and result in a marked reduction in the quality of life

Gait - the manner or style of walking.

Gait Analysis -

An analysis of each component of the three phases of ambulation is an essential part of the diagnosis of various neurologic disorders and the assessment of patient progress during rehabilitation and recovery from the effects of a neurologic disease, a musculoskeletal injury or disease process, or amputation of a lower limb.

Gait speed

• The time it takes to walk a specified distance, usually 6 m or less. Slower speeds correlate with an increased risk of mortality in geriatric patients.
• Normal walking speed primarily involves the lower extremities, with the arms and trunk providing stability and balance.
• Faster speeds - body depends on the upper extremities and trunk for propulsion, balance and stability with the lower limb joints producing greater ranges of motion.

The gait cycle is a repetitive pattern involving steps and strides

A step is one single step

A stride is a whole gait cycle.

Step time - time between heel strike of one leg and heel strike of the contra-lateral leg

The demarcation between walking and running occurs when

• periods of double support during the stance phase of the gait cycle (both feet are simultaneously in contact with the ground) give way to two periods of double float at the beginning and the end of the swing phase of gait (neither foot is touching the ground

The Gait Cycle

The sequences for walking that occur may be summarised as follows:

1. Registration and activation of the gait command within the central nervous system.
2. Transmission of the gait systems to the peripheral nervous system.
3. Contraction of muscles.
4. Generation of several forces.
5. Regulation of joint forces and moments across synovial joints and skeletal segments.
6. Generation of ground reaction forces.

The normal forward step consists of two phases: stance phase; swing phase,

• Stance phase occupies 60% of the gait cycle, during which one leg and foot are bearing most or all of the body weight
• Swing phase occupies only 40% of it, during which the foot is not touching the walking surface and the body weight is borne by the other leg and foot.
• In a complete two-step cycle both feet are in contact with the floor at the same time for about 25 per cent of the time. This part of the cycle is called the double-support phase.Gait cycle phases: the stance phase and the swing phase and involves a combination of open and close chain activities.

Phases of the Gait Cycle (8 phase model):

1. Initial Contact
2. Loading Response
3. Midstance
4. Terminal Stance
5. Pre swing
6. Initial Swing
7. Mid Swing
8. Late Swing.

Heel Strike (or initial contact) - Short period, begins the moment the foot touches the ground and is the first phase of double support involves

• 30° flexion of the hip: full extension in the knee: ankle moves from dorsiflexion to a neutral (supinated 5°) position then into plantar flexion.
• After this, knee flexion (5°) begins and increases, just as the plantar flexion of the heel increased.
• Plantar flexion is allowed by eccentric contraction of the tibialis anterior
• Extension of the knee is caused by a contraction of the quadriceps
• Flexion is caused by a contraction of the hamstrings,
• Flexion of the hip is caused by the contraction of the rectus femoris.

Foot Flat (or loading response phase)

• Body absorbs the impact of the foot by rolling in pronation.
• Hip moves slowly into extension, caused by a contraction of the adductor magnus and gluteus maximus muscles.
• Knee flexes to 15° to 20° of flexion.
• Ankle plantarflexion increases to 10-15°.

Midstance

• Hip moves from 10° of flexion to extension by contraction of the gluteus medius muscle.
• Knee reaches maximal flexion and then begins to extend.
• Ankle becomes supinated and dorsiflexed (5°), which is caused by some contraction of the triceps surae muscles.
• During this phase, the body is supported by one single leg.
• At this moment the body begins to move from force absorption at impact to force propulsion forward.

Heel Off

• Begins when the heel leaves the floor.
• Bodyweight is divided over the metatarsal heads.
• 10-13° of hip hyperextension, which then goes into flexion.
• Knee becomes flexed (0-5°)
• Ankle supinates and plantar flexes

Toe Off/pre-swing

• Hip becomes less extended.
• Knee is flexed 35-40°
• Plantar flexion of the ankle increases to 20°.
• The toes leave the ground.

Early Swing

• Hip extends to 10° and then flexes due to contraction of the iliopsoas muscle 20° with lateral rotation.
• Knee flexes to 40-60°
• Ankle goes from 20° of plantar flexion to dorsiflexion, to end in a neutral position.

Mid Swing

• Hip flexes to 30° (by contraction of the adductors) and the ankle becomes dorsiflexed due to a contraction of the tibialis anterior muscle.
• Knee flexes 60° but then extends approximately 30° due to the contraction of the sartorius muscle.(caused by the quadriceps muscles).

Late Swing/declaration

• Hip flexion of 25-30°
• Locked extension of the knee
• Neutral position of the ankle.

Gait Cycle - Anatomical Considerations

• Pelvic region - anterior-posterior displacement, which alternates from left to right. Facilitates anterior movement of the leg (each side anterior-posterior displacement of 4-5°).
• Frontal plane - varus movement in the: foot between heel-strike and foot-flat and between heel-off and toe-off; hip, in lateral movements (when the abductors are too weak, a Trendelenburg gait can be observed). Valgus movement between foot-flat and heel off in the feet.
• A disorder in any segment of the body can have consequences on the individual's gait pattern.

Gait Descriptions

• Antalgic gait a limp adopted so as to avoid pain on weight-bearing structures, characterized by a very short stance phase.
• Ataxic gait an unsteady, uncoordinated walk, with a wide base and the feet thrown out, coming down first on the heel and then on the toes with a double tap.This gait is associated with cerebellar disturbances and can be seen in patients with longstanding alcohol dependency. People with 'Sensory'Disturbances may present with a sensory ataxic gait. Presentation is a wide base of support, high steps, and slapping of feet on the floor in order to gain some sensory feedback. They may also need to rely on observation of foot placement and will often look at the floor during mobility due to a lack of proprioception
• Equine gait a walk accomplished mainly by flexing the hip joint; seen in crossed leg palsy.
• Parkinsonian Gait (seen in parkinson's disease and other neurologic conditions that affect the basal ganglia). Rigidity of joints results in reduced arm swing for balance. A stooped posture and flexed knees are a common presentation. Bradykinesia causes small steps that are shuffling in presentation. There may be occurrences of freezing or short rapid bursts of steps known as ‘festination’ and turning can be difficult.
• Trendelenburg gait, the gait characteristic of paralysis of the gluteus medius muscle, marked by a listing of the trunk toward the affected side at each step.
• Hemiplegic gait a gait involving flexion of the hip because of footdrop and circumduction of the leg.
• Steppage gait the gait in footdrop in which the advancing leg is lifted high in order that the toes may clear the ground. It is due to paralysis of the anterior tibial and fibular muscles, and is seen in lesions of the lower motor neuron, such as multiple neuritis, lesions of the anterior motor horn cells, and lesions of the cauda equina.
• Stuttering gait a walking disorder characterized by hesitancy that resembles stuttering; seen in some hysterical or schizophrenic patients as well as in patients with neurologic damage.
• Tabetic gait an ataxic gait in which the feet slap the ground; in daylight the patient can avoid some unsteadiness by watching his feet.
• Waddling gait exaggerated alternation of lateral trunk movements with an exaggerated elevation of the hip, suggesting the gait of a duck; characteristic of muscular dystrophy.
• Diplegic Gait (Spastic gait). Spasticity is normally associated with both lower limbs. Contractures of the adductor muscles can create a ‘scissor’ type gait with a narrowed base of support. Spasticity in the lower half of the legs results in plantarflexed ankles presenting in ‘tiptoe’ walking and often toe dragging. Excessive hip and knee flexion is required to overcome this
• Neuropathic Gaits. High stepping gait to gain floor clearance often due to foot drop

Musculoskeletal Causes:

Pathological gait patterns resulting from musculoskeletal are often caused by soft tissue imbalance, joint alignment or bony abnormalities affect the gait pattern as a result

Gait Analysis

• The analysis of the gait cycle is important in the biomechanical mobility examination to gain information about lower limb dysfunction in dynamic movement and loading.
• When analysing the gait cycle, it is best to examine one joint at a time.
• Objective and subjective methods can be used.

Subjective

• Different gait patterns - We might ask the individual to walk normally, on insides and outsides of feet, in a straight line, running (all the time looking to compare sides and understanding of "normal").
• Ask/observe the type of footwear the patient uses (a systematic review suggests shoes affect velocity, step time, and step length in younger children's gait.

Objective

An objective approach is quantitative and parameters like time, distance, and muscle activity will be measured. Other objective methods to assess the gait cycle that use equipment include:

• Video Analysis and Treadmill
• Electronic and Computerized Apparatus
• Electronic Pedometers
• Satellite Positioning System