Biomechanics of the Female Pelvic Floor

Lennox Hoyte, Margot Damaser, Lennox Hoyte, Margot Damaser

• Publisher: Academic Press
• Year: 2016
• ISBN:
  9780128032299
• Topic: Biological Sciences
• Subtopic: Human Anatomy & Physiology
• Index: Biological Sciences

Biomechanics of the Female Pelvic Floor, Second Edition, is the first book to specifically focus on this key part of women's health, combining engineering and clinical expertise. This edited collection will help readers understand the risk factors for pelvic floor dysfunction, the mechanisms of childbirth related injury, and how to design intrapartum preventative strategies, optimal repair techniques, and prostheses.

The authors have combined their expertise to create a thorough, comprehensive view of female pelvic floor biomechanics in order to help different disciplines discuss, research, and drive solutions to pressing problems. The book includes a common language for the design, conduct, and reporting of research studies in female PFD, and will be of interest to biomechanical and prosthetic tissue engineers and clinicians interested in female pelvic floor dysfunction, including urologists, urogynecologists, maternal fetal medicine specialists, and physical therapists.

• Contains contributions from leading bioengineers and clinicians, and provides a cohesive multidisciplinary view of the field
• Covers causes, risk factors, and optimal treatment for pelvic floor biomechanics
• Combines anatomy, imaging, tissue characteristics, and computational modeling development in relation to pelvic floor biomechanics

Section 1

Principles of Pelvic Floor Anatomy and Biomechanics

Chapter One

What Biomechanics Has to do With the Female Pelvic Floor — A Historical Perspective

M. Alperin University of California, San Diego, CA, United States of America

Abstract

Biomechanics is a branch of the field of bioengineering which applies engineering principles and the methods of mechanics to the studies of biological systems. In other words, by means of biomechanics we can investigate how physical forces interact with living systems. As its name implies, one of the central characteristics of biomechanics is that it is highly interdisciplinary. The diverse applications of biomechanics extend from the acquisition of new knowledge and understanding of biological systems through engineering sciences to the development of new clinically relevant technologies. To facilitate a shared interdisciplinary approach to current clinical and research questions in female pelvic medicine, a common language between biomechanical engineers and health care providers must be created.

Keywords

History; Biomechanics; Female pelvic medicine

They had different backgrounds and temperaments and perspectives, and if you gave them something to think about…you were guaranteed a fresh set of eyes.

Malcolm Gladwell (2008)

The pelvic floor consists of bones, connective tissue, smooth and skeletal muscles, and their innervation. The complex mechanical function of the female pelvic floor is to provide support to the pelvic organs and contribute to continence by counteracting the forces generated by intra-abdominal pressure, gravity, and inertia, without interfering with micturition, defecation, sexual functions, and parturition. Biomechanics is a branch of bioengineering, which applies engineering principles and the methods of mechanics to the studies of biological systems. In other words, by means of biomechanics we can investigate how physical forces interact with living systems. As its name implies, one of the central characteristics of biomechanics is that it is highly interdisciplinary. This is highlighted by the American Society of Biomechanics mission statement: “To foster the exchange of information and ideas among biomechanists working in different disciplines, biological sciences, exercise and sports science, health sciences, ergonomics and human factors, and engineering, and to facilitate the development of biomechanics as a basic and applied science” [1]. Biomechanics includes the study of motion, material deformation and load bearing, tissue remodeling, flow of bodily fluids, transport of chemical constituents across biological and synthetic membranes, and tissue engineering. Thus, the applications of biomechanics are diverse, extending from expanding our understanding of biological systems through engineering sciences, to the development of novel clinically relevant technologies. Following the advancement of knowledge pertaining to the biological systems and human physiology through history presents a compelling story of long-standing symbiotic relationships between medical and biomechanical sciences.

Evolution of Biomechanics Through the Centuries

Human interest in biomechanics is long-standing and can be traced back to antiquity (650 BC–AD 200). Aristotle was fascinated by anatomy and the structure of living things and is considered to be the first biomechanician. In his book titled “De Motu Animalium” — “On the Movement of Animals,” he described animal bodies as mechanical systems [2]. After the fall of Greece, the new Roman Empire became the world’s scientific center. One of the dominant Roman figures in medicine in the 2nd century was Galen, an anatomist and a personal physician of the Roman Emperor, Marcus Aurelius. Galen promoted the application of Hippocrates’ bodily humors theory to the understanding of human diseases. As Roman law had prohibited the dissection of human cadavers, Galen performed vivisections and anatomical dissections on dead animals to determine biomechanical function of internal organs based on their structure. He summarized his observations in his monumental work, “On the Function of the Parts,” which served as the world’s medical text for close to 1500 years [3].

The advancement of all sciences, including biomechanics, was frozen until the Renaissance, which started in Italy in the late medieval period (1300–1500) and subsequently spread through the rest of Europe. One of the most prominent Renaissance figures, Leonardo da Vinci (1452–1519), who was an accomplished artist and an engineer, studied anatomy in the context of mechanics, effectively learning biomechanics. Through military and civil engineering projects and his inventions, ranging from water skis to hang gliders, Da Vinci developed an understanding of components of force vectors, friction coefficients, and the acceleration of falling objects [4]. He applied these principles to analyze force vectors of skeletal muscles and joint function. Soon afterward, the groundwork for subsequent mechanical advancements was also laid on other areas. In 1543, Copernicus published his manuscript, titled “Dē revolutionibus orbium coelestium” — “On the Revolutions of the Heavenly Spheres” [5]. In opposition to Aristotelian common-sense physics, his derivations promoted mathematical reasoning to explain orbital motion of “heavenly spheres.”

Two decades after the death of Copernicus, Galileo Galilee (1564–1642) was born in Italy. Galileo made significant contributions to observational astronomy and played an important role in the scientific revolution of the Renaissance period. He is considered to be the father of modern science. Indeed, Galileo’s investigative approach was identical to what we refer to today as the scientific method: he examined facts critically and reproduced known phenomena experimentally to determine cause and effect [6]. Galileo is also referred to as the father of biomechanics. Based on his observation that animals’ masses increased disproportionately to their sizes, Galileo concluded that their bones must also disproportionately increase in girth, adapting to the load-bearing conditions rather than merely to size. This was one of the first documented examples demonstrating the principles of biological optimization and allometry, which examines size of an organism and its consequences.

Another significant contributor to the development of biomechanics in the 17th century was Galileo’s contemporary, a French mathematician Rene Descartes (1596–1650). He suggested a philosophical system whereby all living systems, including the human body (but not the soul), are simply machines ruled by the same mechanical laws [7]. Descartes was instrumental in establishing the iatrophysical approach to medicine, which attempted to explain physiological phenomena in mechanical terms. The idea that mechanics was the key to understanding the function of the human body further promoted the evolution of biomechanics and was later embraced by the Italian physiologist and physicist Giovanni Borelli (1608–79). Borelli studied walking, running, jumping, the flight of birds, the swimming of fish, and determined the position of the human center of gravity [8,9]. In addition, he calculated and measured tidal volumes and showed that inspiration is muscle-driven and expiration is due to the elastic recoil of tissue. Similarly, he studied the piston action of the heart within a mechanical framework. Borelli also made significant contributions to astronomy, predicting that planets follow parabolic orbits due to the forces exerted on them by the sun. This work preceded Isaac Newton’s (1642–1727) law of universal gravitation, which states that a force of interaction between any two bodies in the universe is directly proportional to the product of their masses and inversely proportional to the square of the distance between them. Newton’s law of universal gravitation, published in 1687, is based on the classical mechanics principle that the motion of macroscopic objects is determined by the forces exerted upon them [10].

The second half of the Enlightenment era (1620–1780) was marked by wars in Europe, the Indian subcontinent, and the Americas, culminating in the French and American revolutions. Following the advancements in biomechanics during the 1600s, the wars and the turmoil halted major developments in the field until the early 19th century. In 1807, Thomas Young (1773–1829), an English physician and scientist whose discoveries span many areas, defined the modulus of elasticity that bares his name today [11]. Young studied fluid flow in pipes and the propagation of impulses in elastic vessels. When he applied his observations to the analysis of blood flow in the arteries, he deduced that it was the heart and not the peristaltic motion of arterial walls that mainly contributed to blood circulation. Young also engineered a device for determining the size of a red blood cell, which he remarkably accurately measured to be 7.2 μm [12].

The late 18th and the 19th centuries were the times of the Industrial Revolution, marked by the transition from hand production to new manufacturing processes using machines. The demands placed by the industrialization fostered studies of mechanics of various materials, leading to one of the most striking historical examples of significant advancement in biology made possible by application of engineering science to the human body. Toward the end of the 19th century, extensive studies of human movement were conducted in Europe. One of leaders in the field of locomotion was Christian Wilhelm Braune (1831–92), a German anatomist who determined the center of gravity of the human body through cadaveric dissections. Braune did extensive work on analysis of human gait and calculation of resistive forces placed o...