What is Biomechanics

Biomechanics is a branch of science which employs mechanical and engineering principles to study

biological systems

The objectives of Biomechanics are:• To understand human physical performance: how

do we perform movement and apply forces? how is human motion controlled and how can it be refined;

• To understand how the biological tissues (materials) such as muscles, bones, cartilage, tendons and other soft tissues participate in such performance;

Objectives of Biomechanics Cont.

• To determine what kind of forces are acting on musculoskeletal tissue elements during physical activity;

• To find out what are the mechanical properties of the relevant biological tissues; how do they deform and endure the application of forces and how do they remodel;

• To understand the mechanisms of injury; what kind of loads cause tissues to fail (lose their structural integrity);

Examples of Questions that Biomechanics can Answer

• Truck drivers are known to develop chronic lower back pain. Is there a critical vibration spectrum which will cause injury?

• Running can produce injuries to the joints of the lower limbs. Can athletic shoes help prevent injury by improving dynamic foot-ground interaction?

• Leg amputation and a continuous use of prosthesis is likely to produce lower back pain in later life. Can such arthritic development be prevented via control of the limb structural parameters?

Examples of Biomechanical Applications

Plastic surgeon needs to perform skin graft to cover an affected area of burned skin. What is the best way to prepare skin for grafting?

Plastic surgeon needs to perform reconstructive surgery by transplanting cartilage from the sternum to the nose. How can he prevent stress related deformity

How does one control an overuse syndrome in articular cartilage such as in osteoarthritis of the knee or hip;

Examples Cont.

• An orthopedic surgeon is presented with a case of a child where the hip joint is abnormally overloaded such that it causes degeneration of the joint cartilage. What kind of solution can be applied and what are the consequences;

• Degenerative changes in a joint (Ankle, knee, hip, spine) may cause unbearable pain. The surgeon may consider fusion of the bony elements of the joint. What are the benefits and the shortcomings of the procedure.

Examples Cont.• An alternative solution to the same problem

could be to resurface the joint with prosthetic components, what kind of loads need to be considered? how should the prosthetic component be interfaced to the bony tissue? what kind of geometry need to be reproduced?

• Runners often suffer joint injuries as a result of the frequent and extensive loading. Are shoes contributory to the alleviation of such stresses? Which shoe characteristics need to be considered?

• A child broke his tibia. Is plaster casting a good solution?

Examples Cont.

• In the design of high acceleration equipment, such as: airplanes, space rockets, roller coasters and road vehicles, how does one decide what kind of accelerations can the body sustain without being injured?

• In the design of off road equipment and vehicles, exposure to vibrations considers: frequencies; amplitudes; duty cycle; exposure time, etc.?

• In the design of seat belts for automotive application, what would be an optimal configuration to prevent rib fractures?

Human Performance Biomech.

• Biomechanics in Rehabilitation

• Biomechanics in Sport

• Occupational Biomechanics

Performance of Movement1. How do we perform movement and/or apply forces;

Fn

Fm Quad

Fm Achil

Fm Calf

The Musculoskeletal SystemThe Musculoskeletal System

Anatomy&Physiology

Origin

Insertion

Musculoskeletal Biomechanics

• Modeling of the MSK system with the objective of identifying forces exerted/acting on the Bones, Joints, Muscles and other soft tissues;

• Application to Trauma, Prosthetics and Orthopedic Implant Design.

Tissue Biomechanics

• The study of the mechanical behavior of biological tissues– Force– Deformation– Growth and Remodeling– Failure

Bone Mechanics & Remodeling

Knowledge Required to deal with Biomechanical Problems

• Anatomy: understanding body structural composition

• Physiology: understanding the body operational principles

• Applied Engineering-Mechanics: The modeling tools

The Principles of Biomechanical Analysis

• We approach the biomechanical analysis similarly to the mechanical analysis:Determine the external forces either by static

modeling or by dynamic modelingDetermine the internal forces via fragmentation

and free body diagramsAttribute the internal forces and moments to the

corresponding tissuesPerform Tissue Mechanics analysis

Performance Analysis is the way to Determine the External Loading

• Document the motion (kinematics);• Measure the applied forces;• Assess muscular activity (EMG);• Analyze trajectories of motion;• Develop a dynamic model to determine the forces;• Suggest ways to ptimize the performance;• Alternatively, analyze the motions of an elite athlete

and adopt his/her criteria;

A Typical Protocol For Tissue Mechanics Study

• Determine the performance characteristics– Motion, External Forces (measurable);

• Focus on a particular body part/tissue of interest and determine the forces acting on it – Typically a model is required;

• Subject the specific part/tissue to the applied forces and obtain its mechanical behavior comparing loads and deformations;

• Compare the forces to the tissue endurance values

Data Presentation

1. Document the motion (kinematics)

2. Measure the applied forces

Ground Forces acting during locomotion

Analyze Trajectories of Motion

Determine velocities and accelerations