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SAN FRANCISCO -- After conducting a detailed analysis of the forces at work during commonly performed maneuvers by elite basketball players, Duke University Medical Center researchers believe they now better understand the causes of season-ending and potentially career-threatening stress fractures of the foot.
The solution, they continued, may be as simple as adding additional arch support to athletic shoes. This preventative action appears to relieve the constant stresses and pressures suffered by the fifth metatarsal, a bone on the outside of the mid-foot between the ankle bone and the small toe.
The results of the Duke study were presented March 13, 2004, at the annual meeting of the American Academy of Orthopedic Surgery by orthopedic surgeon Joseph Guettler, M.D., of William Beaumont Hospital, Royal Oak, Mich. Guettler conducted the research while a sports medicine fellow at Duke in the Michael W. Krzyzewski Human Performance Laboratory (K Lab) at Duke.
"These stress fractures of the fifth metatarsal are a prevalent and potentially devastating injuries suffered by elite basketball players, and they appear to occur as a result of the repetitive stresses placed on the bone," Guettler said. "The fractures are tiny, but over time they can coalesce into one large fracture. It is the equivalent in the foot of what happens in shin splints."
Since there have been few studies of stress fractures of the fifth metatarsal under "real-world" conditions, the Duke researchers wanted to characterize the stresses acting upon the bone, when they were most likely to occur, and if anything could be done to lessen the pressures.
For their analysis, the researchers recruited 11 male college basketball players. Electronic pressure sensors capable of continuous readings were inserted into the soles of their shoes. The researchers also placed electromyography (EMG) sensors on two of the muscles of the foot to measure the electrical activity of the muscles.
The players were then asked to perform three of the most common maneuvers experienced during a typical basketball game: landing on one foot following a jump during a simulated lay-up, changing direction 180 degrees during a side-to-side shuffle, and pivoting 180 degrees during a forward sprint.
Detailed measurements of maximum forces, work and time elapsed were taken while players wore their normal shoes and also in shoes with accentuated arch support.
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"The greatest elapsed time and greatest average work beneath the fifth metatarsal occurred during pivot moves," Guettler explained. "And the greatest forces were experienced when players landed after lay-ups. The forces under the fifth metatarsal were consistently greater then the maneuvers were performed in shoes without an enhanced medial arch.
"The added arch caused a statistically significant reduction in the maximum forces encountered under the fifth metatarsal during the pivot and lay-up maneuvers," he said. "Additionally, peak EMG measurements were higher for all the maneuvers for players with the arch. It appears that supporting the arch may reduce the stresses encountered beneath the fifth metatarsal and help prevent these injuries in the future."
The researchers said that muscles within the foot and how they respond also play an important role in determining whether or not a specific action has a negative effect on the fifth metatarsal. The finding that EMG activity was elevated when arch support was used is an interesting one, Guettler said, adding that this phenomenon is a future avenue of research.
"This study is a perfect example of the type of work conducted in the K Lab," said Claude T. Moorman, M.D., director of sports medicine at Duke and senior member of the research team. "We identify a problem, conduct research to better understand the issues, and then come up with solutions -- all with the goal of preventing injury and improving performance."
Moorman said that the Duke findings run counter to what had been assumed by shoe manufacturers -- namely that high arch support was the cause of fifth metatarsal stress fractures. No one, however, had conducted the research to determine the answer, Moorman said.
Moorman and his K Lab colleagues are taking this research one step further.
"We plan to use magnetic resonance imaging (MRI) techniques to image basketball players over time to hopefully gain a better understanding of the sequence of events leading up to the injury, Moorman continued. "The MRI is ideal for capturing the tiny fractures that are the hallmark of the condition."
Both Guettler and Moorman said that while the current study looked at elite athletes, the findings are also applicable to all types of athletes who participate in sports requiring similar maneuvers.
The study was supported by the K Lab and the Piedmont Society, a group founded by orthopedic surgeons who trained at Duke.
Other members of the Duke were Gregory Riskan, Jeffrey Bytomski, D.O., Christopher Brown, M.D. and Jan Richardson, Ph.D.