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Why Mastering Biomechanics Is Crucial To The Profession

The foot is our prime mechanical interface with the terrestrial environment we all live in.

   In order to stand, our feet must continually bear our full weight, adjusting the location of force underneath them to keep our bodies balanced in an upright position. In order to walk, our feet must adapt to surface irregularities and efficiently move and balance our center of mass while also continually absorbing and generating ground reaction forces with each step we take. In order to run, jump or perform the vast majority of other sports activities, our feet must be able to transfer large loading forces to the ground with precise timing. This allows us to accomplish these athletic activities in a quick, efficient and well coordinated manner.

   No other part of our bodies — not our heads, hands, elbows, shoulders, hips, knees or ankles — is subjected to such large external forces from our environment for such long periods of time as are our feet. In standing, our feet continually bear about half our body weight. In walking, peak ground reaction forces are about 1.25 times body weight. In running, forces between the foot and ground are between 2.5 and 3.0 times body weight. In high jumping, plantar loading forces have been measured as high as eight times body weight.

   We all take these remarkable machines for granted while they are painlessly working in mechanical harmony with the surfaces we live on. As podiatrists, we have chosen to become members of the only medical profession that is chiefly devoted to care for this amazing mechanical organ. As such, we have been inherently assigned the task of keeping the feet of our communities functioning properly in all weightbearing activities so mechanical dysfunction of the foot does not cause pain, deformity or disability.

   If our goal, as a medical profession, is to provide the most modern and therapeutically effective medical care for the feet of our patients, then it seems quite logical that we should also be very serious about our devotion to understanding the biomechanics of these complex mechanical organs.

   We should be mature enough as a profession to realize that, regardless of our area of interest within our profession, whether it be foot and ankle surgery, diabetic foot care, sports medicine or any other podiatric subspecialty, the foot is primarily a mechanical organ. Due to this fact, the large magnitudes of external forces that affect the foot throughout our daily activities need to be a major consideration in any conservative or surgical treatment plan for our patients.

   When patients come into our offices complaining of a painful condition or deformity of the foot, we must always keep in mind the possible mechanical effects that these external forces — from the ground or from the shoe — may be having on the internal forces that are generated within the structural components of the foot and lower extremity. Whether that structural component is skin, adipose, ligament, muscle, tendon, fascia, bursa or bone, each of these parts that make up the structure of the foot and lower extremity is subjected to increased tensile, compression, shearing or torsional internal loading. These forces may, step after step, cause tissue injury, pain and foot deformity.

   Whether our treatments are conservative or surgical in nature, we should never forget or ignore the crucial fact that the foot is the prime terrestrial interface organ for our patients during their daily activities. Much of what will determine our treatment success or failure will be dependent on our depth of knowledge and how carefully our treatment methods consider the complex mechanical interactions among all the structural components of the foot and the external and internal loading forces they are subjected to throughout the day.

   Therefore, should we, as a medical profession, continue to move away from becoming experts in the mechanical function of the foot and lower extremity and move toward becoming more advanced surgical technicians with less knowledge of the negative mechanical consequences that our surgical procedures may have on the foot and rest of the lower extremity and body?

   No. As a profession, we should continue to strive toward becoming master mechanics who can diagnose and provide both expert conservative and surgical care for the most important and complex machine of the human body, the foot. Our patients deserve nothing less.

   Dr. Kirby is an Adjunct Associate Professor within the Department of Applied Biomechanics at the California School of Podiatric Medicine at Samuel Merritt University in Oakland, Calif. He is in private practice in Sacramento, Calif.

   Dr. McCord recently retired from practice at the Centralia Medical Center in Centralia, Wash.

Kevin A. Kirby, DPM


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