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Post-Polio Health (ISSN 1066-5331)

Vol. 16, No. 3, Summer 2000

Post-Polio Syndrome as a Model for Musculo-Tendinous Overuse Syndromes in Military and Civilian Populations

Mary Klein, PhD, Moss Rehabilitation Research Institute, Philadelphia, Pennsylvania
Final Report

"Post-Polio Syndrome as a Model for Musculo-Tendinous Overuse Syndromes in Military and Civilian Populations" is the title of a research project recently completed by researchers at the Albert Einstein Healthcare Network (AEHN) in Philadelphia, PA. The co-investigators were Drs. Mary Ann Keenan (Department of Orthopedics, Albert Einstein Medical Center), Alberto Esquenazi (Gait Analysis Laboratory, MossRehab Hospital), and John Whyte (Moss Rehabilitation Research Institute). The main goal of this project, which was funded by a grant from the Department of the Army, was to examine the relationship between weakness, overuse and injury. By studying overuse problems among polio survivors, researchers hope to learn more about how overuse injuries develop and how the body compensates for different levels of muscle weakness.

One of the objectives of this project was to determine the effect of custom-fit orthoses on plantar fasciitis or heel pain. The hypothesis was that an orthotic that alters the pattern of muscle use in the lower extremity would hasten the resolution of plantar fasciitis symptoms. Nine polio survivors with plantar fasciitis symptoms were given ankle-foot braces and 18 adults with no history of polio and symptoms of plantar fasciitis were given molded shoe inserts. The braces and shoe inserts were custom fit and 7-10 days after the final fitting, each subject underwent a gait evaluation with and without the orthotic. Muscle activity was measured during each test. The results showed a significant improvement in symptom severity for both braces and inserts. In addition, among the subjects with inserts, there was a significant increase in plantar flexor activity during the mid-to-late stance phase of the gait cycle when the insert was worn than when the insert was not worn. The researchers speculated that the resolution of pain caused a reduction in the compensatory mechanisms associated with plantar fasciitis, resulting in gait that was more efficient and "normal." Unfortunately, the data for the subjects with braces showed no consistent trends across subjects indicating that the compensatory mechanisms employed by subjects with greater weakness are more complex and variable. Additional research is needed with a larger number of polio survivors in order to be able to characterize these mechanisms accurately.

Another objective of this project was to quantify some of the compensation behaviors utilized by individuals with leg weakness during a sit-to-stand task. A total of 12 polio survivors with primary leg weakness limited to one side were enrolled along with 6 subjects with no history of polio, who had undergone recent unilateral knee surgery. The goal was to compare the strategies used by people with chronic knee weakness (i.e. polio survivors who had lived with weakness for many years) versus those with acute knee weakness (i.e. patients who had no history of leg weakness prior to knee surgery). The subjects performed a sit-to-stand task under four different conditions. These conditions varied in terms of chair height (high vs. low) and whether the subjects could use the armrests or not. For each condition, the subject sat in the chair and then stood up as normally as possible. This was repeated 4-8 times. Muscle activity, force and motion data were collected for each test. The results showed that the subjects shifted their weight on to the strong leg when performing the task. They also tended to bear more weight on the arm on the strong side, indicating a shift in the body's center of mass toward the unaffected side. This shift was much more significant in the lower chair than in the higher one and was more significant in the polio survivors than in the surgery patients. Different compensation strategies were used to accomplish this shifting, including changing the position of the feet and increasing the rate and degree of forward motion of the trunk prior to lifting the body off the chair. Interestingly, even though the polio survivors were significantly weaker than the surgery patients, they got out of the chair quicker than the surgery patients did. This suggests that the compensatory behaviors were better established in the polio survivors, allowing them to make the necessary adjustments and complete the task in a shorter time. 

A related peer-reviewed article, "The relationship between lower extremity strength and shoulder overuse symptoms: a model based on polio survivors," written by Klein, Whyte, Keenan, Esquenazi, and Polansky was published in the Archives of Physical Medicine & Rehabilitation, 2000 Jun;81(6):789-95 81(6), 789-795.

Drs. Keenan and Esquenazi, along with Mary Klein, PhD (Moss Rehabilitation Research Institute) were recently awarded additional funding from the Department of the Army and the National Institute on Disability and Rehabilitation Research (NIDRR) to continue their work on musculoskeletal problems among polio survivors. Dr. Klein was the project director on the original Army grant. These two-year grants, totaling $1,362,500, will include both polio survivors and elder adults with no history of polio. The objective is to determine how musculoskeletal problems influence quality of life and functional ability in older adults, with and without a history of polio, and the role of exercise in treating these problems.