Prosthetics and Orthotics: Biomechanics of Lower Limb

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Questions and Answers

What is the primary function of the lower limb?

Providing energy for the entire body

Mobility, which is a means of travel from one place to another (correct)

Maintaining balance during uneven surfaces

Supporting force during stopping on level surfaces

What is the average walking speed for a person with an asymmetrical gait?

1.1-1.2 m/s

1.5-1.6 m/s

1.3-1.4 m/s (correct)

1.7-1.8 m/s

Why do individuals with neuromuscular or skeletal deficits often walk slower?

To increase stability (correct)

To increase energy expenditure

To reduce joint motion

To enhance their sense of security

What happens to the range of joint motion when walking speed is reduced?

It decreases Signup and view all the answers

How does the path of the center of gravity affect energy expenditure during walking?

A smoother path reduces energy expenditure Signup and view all the answers

How do amputees adapt to walking with a prosthetic device?

They use different muscle groups to create a smoother gait pattern Signup and view all the answers

Why is energy consumption higher for amputees compared to non-amputees?

Because they use different muscle groups to compensate for the loss of the limb Signup and view all the answers

What is the relationship between metabolic cost and walking speed in non-amputees?

Metabolic cost increases with increased walking speed Signup and view all the answers

What is the primary function of the quadricep group during gait?

To control the rate of flexion and return the knee to full extension Signup and view all the answers

What is the consequence of not having knee flexion during gait?

The limb is loaded more abruptly Signup and view all the answers

Why is it challenging to provide shock absorption in prosthetic and orthotic devices?

Because the devices are too heavy, complex, and expensive Signup and view all the answers

What is the primary function of the knee during the stance phase of gait?

To support the body weight Signup and view all the answers

Why is it important to maintain the line of action of ground reaction force anterior to the knee joint axis in prosthetic and orthotic design?

To prevent knee buckling Signup and view all the answers

How can the relationship of the force line and the knee joint be affected in prosthetic and orthotic design?

By changing the foot ankle posture, locating the knee axis more posteriorly Signup and view all the answers

What is the result of delaying knee flexion in pre-swing phase for users with prosthetics or orthotics?

A less smooth, slower and less efficient gait Signup and view all the answers

What is the primary function of the knee during the initial swing phase?

To shorten the limb Signup and view all the answers

What is the purpose of the locking mechanism in prosthetic and orthotic devices?

To prevent knee motion for stability and safety Signup and view all the answers

What is the name of the prosthetic device offered by Ottobock that adjusts to normal and different walking speeds?

C-leg Signup and view all the answers

What is the typical price range of the C-leg prosthetic device?

$40,000 to $60,000 Signup and view all the answers

What is the result of using a locking mechanism in prosthetic and orthotic devices?

Stiff-Knee gait Signup and view all the answers

What is the primary function of the knee during the pre-swing phase?

To flex while partially loaded Signup and view all the answers

What is the purpose of the knee extensors during the initial swing phase?

To limit knee flexion and initiate knee extension Signup and view all the answers

Study Notes

Biomechanics of Lower Limb

The primary function of the lower limb is mobility, which involves controlling and supporting forces during various movements.

Gait Cycle

Walking speed is approximately 1.3-1.4 m/s for asymmetrical gait (normal person).
Walking speed varies with height and inversely with age.
Individuals with neuromuscular or skeletal deficits may have slower walking speeds to ensure greater stability, less pain, or enhanced feeling of security.

Energetics of Gait

A smoother path of the center of gravity results in less energy expended by the walker.
Amputees use different muscle groups to create a smoother gait pattern, resulting in higher overall energy consumption.
Metabolic oxygen consumption (energy cost and gait efficiency) correlates directly with increased walking distance and speed in non-amputees.
In amputees, the metabolic cost is higher even at normal speed.

Knee Functions during Gait

Support: The knee supports the body weight during stance phase, and the line of action of ground reaction force must be maintained anterior to the knee joint axis for knee stability.
Limb Shortening: The knee flexes during initial swing phase (60°-65°) to shorten the limb, and knee extensors contribute to limit knee flexion and initiate knee extension.
Knee Flexion: Delayed knee flexion in prosthetic or orthotic users can result in a less smooth, slower, and less efficient gait.

Prosthetic and Orthotic Devices

Ottobock's C-Leg is a microprocessor-controlled hydraulic unit that adjusts to any walking speed and ensures a secure stance phase.
The C-Leg costs between $40,000 and $60,000.
Simpler devices may be adjusted to a particular speed, but may not provide the same level of functionality.

Gait Patterns for Stiff Knee

Circumduction: Using hip abduction during hip flexion to advance the limb in a semicircular path (increased energy expenditure).
Hip Hiking: Lateral tilting or abduction of the pelvis on the contralateral limb to elevate the hip joint (higher energy expenditure).
Quadricep Group: Controlling the rate of flexion and returning the knee to full extension to smooth the movement of the center of gravity (COM).

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Description

This quiz covers the biomechanics of the lower limb, including its primary function, controlling and supporting forces, and factors affecting normal gait. Understand the normal gait cycle and how it's restored or substituted with prosthetic or orthotic devices.