Biomechanics

Definition

Biomechanics is the application of the branch of physics known as mechanics to living organisms or their structures. Mechanics deals with the laws of motion and the action of forces on objects.

Description

Biomechanics may involve the study of living plants or animals on any level of complexity from the molecular up to tissues and entire organs. Biomechanics at the molecular level investigates such subjects as the properties of specific biomaterials, such as collagen or elastin (proteins found in connective tissue). At the tissue level, biomechanics can be used in such new fields as tissue engineering to evaluate the strength, flexibility, and general safety of laboratory-produced tissues or tissue substitutes, or to investigate the physical properties of bone, smooth muscle, striated muscle, cartilage, or other specific tissue types. At the level of organs or entire limbs, biomechanics is often used in kinesiology, which is the study of motion of the human body. It may be used in clinical medicine as well as research, to design rehabilitation programs for specific types of injury, to evaluate gait disorders or patterns of injury in various sports or occupations, to invent and test new assistive devices and rehabilitation equipment, or to investigate transportation accidents and certain types of crimes.

Biomechanics as a branch of science can be traced back as far as the Greek philosophers Plato and Aristotle in the fourth century B.C. Aristotle wrote the first treatise on movement in animals that analyzed their bodies as mechanical systems. In the second century A.D., the Roman physician Galen wrote a book on the functions of the various parts of the human body. It served as the standard medical text in the West until 1543, when the Flemish surgeon Andreas Vesalius published a landmark text on human anatomy. The next major contribution was made by Galileo, who studied the mechanics of bone structure and the relationship between the size of an animal's bones and its body mass.

The so-called father of biomechanics, Giovanni Alfonso Borelli (1608–1679), was an Italian mathematician and physicist whose great work De motu animalium (On the Motion of Animals) was published shortly after his death. Among other discoveries, Borelli worked out the forces required for equilibrium in different joints of the human body before Isaac Newton published his three laws of motion. Borelli also determined the position of the center of gravity in human adults and measured lung volume. The highest award given by the American Society of Biomechanics (ASB) is named for Borelli.

After Borelli, there were few advances in biomechanics until the nineteenth century, when the industrial revolution prompted the invention of new metal alloys as well as new machines and methods of transportation, all of which led to clinical experimentation and advances in orthopedic surgery, dentistry, and physical therapy. The invention of photography enabled Edward Muybridge's famous studies in the 1870s of running horses and of men and women running, walking, and jumping. These photographic studies of movement were the ancestors of modern gait and motion analysis. In the twentieth century biomechanics became an interdisciplinary specialty in its own right, attracting engineers, biochemists, and biophysicists as well as health professionals. The 1970s saw the formation of national and international biomechanics societies, as well as the coining of the word "biomechanician" for scientists in the field.

KEY TERMS

Biomechanician— A scientist or health professional who specializes in biomechanics.

Forensic biomechanics— The study of or application of biomechanics to legal or criminal justice issues, such as homicide or accident investigations.

Gait analysis— The measurement and interpretation of a person or animal's characteristic pattern of walking or running.

Kinematics— The calculation or description of the movements of a body (or group of bodies) considered in themselves, apart from the causes of motion.

Kinesiology— The study of motion in the human body.

Mechanics— The branch of physics that deals with the laws of motion and the effects of forces on material bodies.

Tissue engineering— The multidisciplinary field that deals with the design and testing of biological substitutes to restore or improve tissue function. Tissue engineering makes use of biomechanical studies of natural and engineered tissues as well as cell research, biochemistry, gene and protein sequencing, and many other areas of research in the health sciences. It is sometimes referred to as regenerative medicine.

Applications

The following are only some of the major clinical applications of biomechanics in the early 2000s:

• Burn treatment. Tissue engineering has advanced the treatment of acute burns by its development of skin substitutes and various types of skin grafts made by growing transplanted skin cells on a scaffold, or artificial structure that allows for three-dimensional tissue formation.
• Dentistry and oral surgery. Biomechanics has assisted the development of minimally invasive dentistry through evaluating the strength and safety of new tooth sealants and filling materials. It is also used to evaluate the stability of dental implants and to analyze oral health problems related to the shape and structure of the jaw.
• Geriatric medicine. Biomechanics is an important part of gait assessment in the elderly. In the 1970s doctors began to use videocameras and a marker system to analyze problems in the patient's pattern of walking. Modern laboratories use gauges in the floor and a computer in addition to cameras to calculate the strength of the patient's joints and muscles and any deviation from normal patterns. This information can be used to guide planning for surgery and physical therapy as well as assess the patient's level of mobility.
• Sports medicine. Gait analysis and similar studies of arm and shoulder movement are used to prevent injuries during training as well as analyze the causes of an athletic injury.
• Occupational medicine. Biomechanical studies are routinely used to assess the effects of using power tools on workers' hands and arms, the causes of repetitive stress injuries (RSIs), the influence of flooring materials and chair design on muscle fatigue, and many similar concerns. Biomechanicians are frequently consulted in the redesigning of tools, furniture, and general workplace architecture and floor plans.
• Transportation safety. The formation of the National Transportation Safety Board (NTSB) in 1967 led to the increased use of biomechanics and kinematics (the branch of mechanics that studies the motion of a body or group of bodies) in evaluating car, airplane, and railroad design as well as in accident investigation. The use of crash-test dummies for accident reenactments and sophisticated computer software for animations or simulations are now commonplace.
• Physical therapy and rehabilitation. Gait and motion analysis can be used to plan a physical therapy program for an individual patient. Biomechanics is also involved in the development of continuous passive motion devices and other rehabilitation equipment.
• Forensic biomechanics. Forensic refers to legal or courtroom proceedings. Biomechanics can be used to help determine the cause of death or injury, and in many cases whether it is intentional or accidental. Expert witnesses often make use of computer reconstructions of a crime or accident during trials.
• Veterinary medicine. As in human medicine, gait and motion analysis can be used in both large- and small-animal practices to evaluate the location and severity of musculoskeletal or dental injuries in animals, and to plan appropriate treatment.

Professional implications

Biomechanics is a rapidly expanding interdisciplinary field of study that continues to improve diagnosis and treatment in all areas of health care. Health professionals with an interest in engineering, mechanical testing, electronics, computer software development, image or movement analysis, comparative anatomy, and similar fields may find that the study of biomechanics opens up new career possibilities as well as refining their present skills in direct patient care.

Resources

BOOKS

"Gait Disorders," Section 2, Chapter 21 in The Merck Manual of Geriatrics, edited by Mark H. Beers, MD, and Robert Berkow, MD. Whitehouse Station, NJ: Merck Research Laboratories, 2005.

"Osteoarthritis," Section 5, Chapter 52 in The Merck Manual of Diagnosis and Therapy, edited by Mark H. Beers, MD, and Robert Berkow, MD. Whitehouse Station, NJ: Merck Research Laboratories, 2005.

PERIODICALS

Alonso, R. C., G. M. Correr, A. F. Borges, et al. "Minimally Invasive Dentistry: Bond Strength of Different Sealant and Filling Materials to Enamel." Oral Health and Preventive Dentistry 3 (February 2005): 87-95.

Ateshian, G. A., and C. T. Hung. "Patellofemoral Joint Biomechanics and Tissue Engineering." Clinical Orthopaedics and Related Research 436 (July 2005): 81-90.

Bandak, F. A. "Shaken Baby Syndrome: A Biomechanics Analysis of Injury Mechanisms." Forensic Science International 151 (June 30, 2005): 71-79.

Dugan, S. A. "Sports-Related Knee Injuries in Female Athletes: What Gives?" American Journal of Physical Medicine and Rehabilitation 84 (February 2005): 122-130.

Geraci, M. C., Jr., and W. Brown. "Evidence-Based Treatment of Hip and Pelvic Injuries in Runners." Physical Medicine and Rehabilitation Clinics of North America 16 (August 2005): 711-747.

Herbst, B., S. Forrest, T. Orton, et al. The Effect of Roof Strength on Reducing Occupant Injury in Rollovers." Biomedical Sciences Instrumentation 41 (2005): 97-103.

Hohlfeld, J., A. de Buys Roessingh, N. Hirt-Burri, et al. "Tissue-Engineered Fetal Skin Constructs for Paediatric Burns." Lancet 366 (September 3, 2005): 788-790.

Lin, J. H., R. Radwin, and D. Nembhard. "Ergonomics Applications of a Mechanical Model of the Human Operator in Power Hand Tool Operation." Journal of Occupational and Environmental Hygiene 2 (February 2005): 111-119.

Lohfeld, S., V. Barron, and P. E. McHugh. "Biomodels of Bone: A Review." Annals of Biomedical Engineering 33 (October 2005): 1295-1311.

Lynnerup, N., and J. Vedel. "Person Identification by Gait Analysis and Photogrammetry." Journal of Forensic Science 50 (January 2005): 112-118.

Viano, D. C., C. Bir, T. Walilko, and D. Sherman. "Ballistic Impact to the Forehead, Zygoma, and Mandible: Comparison of Human and Frangible Dummy Face Biomechanics." Journal of Trauma 56 (June 2004): 1305-1311.

Wettergreen, M. A., B. S. Bucklen, W. Sun, and M. A. Liebschner. "Computer-Aided Tissue Engineering of a Human Vertebral Body." Annals of Biomedical Engineering 33 (October 2005): 1333-1343.

ORGANIZATIONS

American Academy of Orthopaedic Surgeons. 6300 North River Road, Rosemont, IL 60018-4262. (847) 823-7186. ?http://www.aaos.org?.

American College of Sports Medicine (ACSM). 401 West Michigan Street, Indianapolis, IN 46202-3233. (317) 637-9200. Fax: (317) 634-7817. ?http://www.acsm.org?.

American Physical Therapy Association. 1111 North Fairfax Street, Alexandria, VA 22314-1488. (703) 684-2782. ?http://www.apta.org?.

American Society of Biomechanics (ASB). ?http://www.asb-biomech.org?. Contact information for prospective members can be found on the ASB web site, as well as archived copies of the Society's newsletter in PDF format.

National Transportation Safety Board (NTSB) Headquarters. 490 L'Enfant Plaza, SW, Washington, DC 20594. (202) 314-6000. ?http://www.ntsb.gov?.

OTHER

Martin, R. Bruce, PhD. "A Genealogy of Biomechanics." Presidential lecture delivered at the 23rd annual conference of the American Society of Biomechanics (ASB), University of Pittsburgh, Pittsburgh, PA, 23 October 1999. ?http://asb-biomech.org/historybiomech/index/html?.

National Transportation Safety Board (NTSB). Highway Accident Report: Crash of 15-Passenger Van in a Bridge Abutment. Memphis, Tennessee, April 4, 2002. ?http://www.ntsb.gov/events/2004/Memphis/memphis_ani.htm?. This set of video simulations of a highway accident and the kinematics of the van's occupants during the crash is an illustrative example of the use of computer modeling and crash-test dummies in accident investigations.