Can Scaling Theory Aid In Charcot Foot Reconstruction In Obese Patients?

Andrew J. Meyr, DPM, Kelly Pirozzi, DPM, and Corine Creech, DPM

Body mass index is an objective patient finding that is known to correlate with not only the development and outcome of diabetic foot ulceration but also perioperative and long-term patient morbidity and mortality.1 The Centers for Disease Control and Prevention (CDC) reported in 2010 that 35.7 percent of United States adults and almost 17 percent of youth are defined as obese based on the body mass index (BMI).2-4 Put bluntly, obese patients have worse clinical and surgical outcomes following the development of lower extremity pathology.

   Further, we do not expect that this situation and these obesity rates are going to improve over the next several decades. In fact, they are likely to become a progressively worsening problem. Faced with this dilemma, our profession has two options: Continue to work passively within our established paradigm and offer patients conventional interventions, or actively look to other fields of study to evaluate if other research and theories may present unique options for more successful outcomes.

   One possible well-established theory within the field of veterinarian biology is that of scaling theory, which recognizes two important concepts that may be applicable to our current situation. The first is that tissue systems of organisms cannot maintain constant morphology as body mass increases. The second is that constraints of locomotion and support are different in large and small organisms. In other words, the musculoskeletal anatomy, physiology and biomechanics of the lower extremity of an active and healthy patient with a BMI of 22 are not, and probably should not, be the same as the anatomy, physiology and biomechanics of a neuropathic patient with diabetes and a BMI of 48.

   Recent investigations have studied morphologic changes as they relate to scaling theory in the so-called graviportal animals (elephants, rhinoceroses, hippopotami, etc.).5-7 These are evolutionary anatomic and physiologic adaptations that have developed over centuries to assist these animals in withstanding an increased body mass. It is the modest proposal of this investigation to review this work and interpret whether these findings may be related to the surgical reconstruction of the obese patient affected by Charcot neuroarthropathy.

Translating The Dynamics Of Graviportal Soft Tissue To Soft Tissue Loss With The Plantar Calcaneus

On an initial gross macroscopic examination, one can immediately appreciate the thickness of the soft tissues on the plantar aspect of graviportal hind limbs. Similarly, although far advanced in comparison to human feet, graviportal hind limbs consist of a highly structured network of adipose tissue organized into compartments (supporting adjacent osseous structures) and reinforced with collagen, reticulin and elastic fibers. This has the reinforcement of cushions consisting of thick sheets of fibrous connective tissue, which form the chambered adipose compartments.

   Microscopically, there is an intricate and complex neurovascular supply highlighted by numerous Pacinian corpuscles that are embedded within the adipose tissue and Meissner’s corpuscles within the dermal papillae of the thickened plantar skin.
There is an additional unique anatomic structure within the medial metatarsal adipose compartment. This is a cartilaginous rod known as the prehallux or “sixth ray,” and may provide an extra support structure to reinforce this important soft tissue.

   What are the implications for human surgical reconstruction?

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