Research

Foot Complications of Diabetes and Musculoskeletal Changes During Space Flight

Established in September 2002, the laboratory has as its primary foci the study of lower-extremity disease in diabetes mellitus and the exploration of musculoskeletal changes during space flight. At the time of writing, Dr. Cavanagh is in the process of recruiting his research team and establishing new collaborative relationships within the Cleveland Clinic Foundation.

Foot Complications of Diabetes

Lower-extremity amputation in people with diabetes continues to be a major public health problem. More than 65,000 amputations are performed annually on diabetic patients in the United States, and, despite recent efforts, this number is increasing. Ulceration in the neuropathic foot is a major precursor of amputation, and thus identification of risk factors, together with primary and secondary prevention of foot ulceration, are key goals of our research program. To understand the mechanical stresses that occur during foot-shoe interaction and that cause many plantar ulcers, we are developing three-dimensional finite-element models of the interface between foot and shoe.

Our group also has an interest in magnetic resonance imaging of the foot, and we have recently found evidence of remarkable atrophy in all the intrinsic muscles of the neuropathic subjects when compared to nondiabetic controls. Although sensory neuropathy is often emphasized in considerations of diabetic foot pathology, our results show that the consequences of motor neuropathy in the feet are profound in people with diabetes.

Neuropathic patients experience problems with gait and posture. They also suffer more falls and fractures. We are using gait analysis techniques to explore both the role of the foot as a sensory organ and the contributions of proprioception to the control of movement. As Dr. Cavanagh also serves as Academic Director of the Diabetic Foot Care program for the Cleveland Clinic Foundation, his research program is closely integrated with the activities of CCF ‘s newly established Diabetic Foot Clinic.

Musculoskeletal Changes during Space Flight

The loss of bone mineral in the lower extremities is widely viewed as one of the critical factors that may limit long-term human habitation of space. Decrements in muscle function as a result of prolonged exposure to microgravity also have important implications for performance and safety during space missions. A major aim of ongoing projects is to investigate the role that load reduction and reduced muscle activity may play in the loss of bone mineral and muscle strength. Two experiments are currently under way, one ground based and the other on the International Space Station (ISS).

Our ground-based study is designed to examine the efficacy of exercise in microgravity. Tests are conducted on a simulator in which human subjects walk and run while suspended in a harness apparatus to simulate microgravity conditions. This arrangement is being used to examine the biomechanics and perceived comfort of exercise in microgravity; ultimately, the data will be coupled with a robotic simulation of the exercise using human cadaver limbs to measure bone strain during simulated microgravity exercise.

As part of the in-flight experiment, we are characterizing the comparative load on the lower extremities during entire days of working on Earth versus on the ISS. We are using instrumentation from the Human Research Facility (http://hrf.jsc.nasa.gov/). Pre- and post-flight estimates of bone mineral density, muscle cross-sectional area, and joint torques provide a perspective against which the consequences of changes in activity profiles can be judged. The results of this research will provide an understanding of the role of mechanical stress in in-flight osteopenia and important information to assist in the design of exercise countermeasures to bone and muscle loss.