Statement of the NATIONAL COALITION FOR OSTEOPOROSIS AND RELATED BONE DISEASES FY2005 Appropriation for the Department of Defense before the Senate Subcommittee on Defense
Janet Rubin, M.D.
May 5, 2004
Mr. Chairman and Members of the Committee, I am Janet Rubin, M.D., Professor, Department of Medicine, Emory University and Staff Physician at the Atlanta Veterans Affairs Medical Center. I am here today on behalf of the National Coalition for Osteoporosis and Related Bone Diseases to urge your support in maintaining the Bone Health and Military Medical Readiness research program within the Department of Defense and providing necessary funding to preserve the program. The members of the Bone Coalition are the American Society for Bone and Mineral Research, the National Osteoporosis Foundation, the Paget Foundation for Paget’s Disease of Bone and Related Disorders, and the Osteogenesis Imperfecta Foundation.
Bone health is an essential element of military readiness. The goal of the Department of Defense (DOD) is to guarantee military readiness by keeping our forces trained, equipped and ready to adapt to emerging threats. Our troops must be ready and able to endure vigorous activity during combat training as well as during force operations. Soldiers are always at risk of injury, incapacitation, and degraded performance resulting from injuries such as stress fractures –all of which compromise the mission, readiness, and budget of the Armed Forces.
Although the benefits of strenuous physical activity are well documented, these activities are also known to incur certain risks. Musculoskeletal injury, for example, is the most common morbidity in civilian and military populations who participate in physical activity. In fact, fractures account for the highest number of lost duty days in the active duty population of any injury. These injuries incur a high cost to the DOD not only in lost duty days, but in health care, lost training time, and attrition of personnel. Ultimately, the operational readiness of U.S. military forces is severely compromised.
Stress fractures are one of the most common and potentially debilitating overuse injuries experienced in the military recruit population. Stress fractures occur in 0.8 to 5.2% of male recruits, and from 3 to 21% of female recruits. Recent research suggests that several factors may contribute to the increased risk for stress fracture suffered by women, including the density, shape, and size of their bones (which affect bone quality), and their nutritional, hormonal and physical conditioning status.
Lack of physical conditioning affects the U.S. as a whole, along with the military population in particular. An Institute of Medicine report published in 1998 by the Subcommittee on Body Composition, Nutrition and Health of Military Women concluded that the low initial fitness of recruits, both cardiorespiratory and musculoskeletal, appeared to be the principal factor in the development of stress fractures during basic training. The Committee also concluded that muscle mass, strength, and endurance played a critical role in the development of stress fracture. Now we know from DOD-funded research that bone structure adds to the risk of fracture, along with a history of poor diet, lack of exercise, hormonal imbalances and genetic factors. Ethnicity also plays a part.
Isn’t basic training good for recruits’ health, you may wonder. The answer is yes and no. Exercise is important to building bone health, but the type of exercise and the transition to new exercise regiments play a role in bone strength. Many new recruits, upon arrival for basic training, are unaccustomed to intense exercise, particularly strenuous running and marching activities. Under normal circumstances, the increased demand placed on bone tissue causes the bone to remodel to adapt to the new loads, and become stronger in the areas of higher stress. However, if the remodeling response of the bone cannot keep pace with the repetitive demands placed on a service member during the 8 to 12 week training period, a stress fracture may result. Without proper rest and time to heal, the stress fracture may lead to chronic pain and disability. Different types of stress fractures require different treatment. For example, femoral neck or hip stress fractures can sometimes progress to full fractures and interrupt the blood supply to the thigh bone portion of the hip joint. This in turn can cause early degenerative changes in the hip joint. Physicians consider the femoral neck stress fracture to be a medical emergency requiring immediate treatment. Researchers have raised concerns regarding the possible relationship between increased risk for stress fracture and long-term risk of osteoporosis, osteoarthritis, and other bone diseases.
Like hip stress fractures, stress fractures of the navicular (foot bone), anterior cortex of the tibia (front portion of the mid-shinbone), and proximal fifth metatarsal (a bone in the foot) are also slow to heal. Many of these diagnoses require an affected service member cease training for a lengthy period of medical care and rehabilitation until the fracture has healed. At one basic training location, over 70% of the injured soldiers pulled from training were diagnosed with overuse bone injuries.
While stress fracture injury is seen primarily in new recruits, anyone who suddenly increases his or her frequency, intensity, or duration of physical activity, such as a recently called-up reservist is potentially at risk for developing lower body stress fractures.
The study of bone health is not a simple task, as bone health requires a complex interaction between exercise and other factors that affect bone remodeling, such as nutrition, hormonal status, genetics, and biomechanics. Currently, there is a distinct gap in understanding the effects of exercise and other factors on normal bone remodeling in a young adult population; more research is needed to determine the best types of exercise regimens to build and maintain healthy bone. Moreover, an understanding of all factors affecting bone health, particularly in young, healthy men and women, is necessary to fully describe the physiological response of bone and muscle to the physical demands placed on our service members, and to maintain the health and military readiness of our service members.
At this point, Mr. Chairman I would like to identify some of the promising studies currently being funded by the DOD:
Current Studies
• Identifying key mineral and other nutritional levels needed in military rations to ensure optimal bone health of recruits: o Vitamin D, for example, is known to be deficient in the population at large, particularly in sunlight-deprived individuals, and yet it, like calcium, is key to bone health. Researchers are working to determine the proper level of vitamin D required in the military population. A related question is: What levels of vitamin D supplementation are necessary to maintain bone health?
o The effect of calcium and calorie intake on the incidence of stress fractures in the short term, and osteoporosis in the long term, is another subject of investigation.
o How do caloric restriction and disordered eating patterns – and/or related amenorrhea or menstrual period cessation – affect hormonal balance and the accrual and maintenance of peak bone mineral content is a question also under investigation.
• Researching the association between stress fractures and physical training methods, including an examination of past injuries and the effects of poor nutrition, lack of exercise, smoking, use of anti-inflammatory medications, alcohol and oral contraceptives, all of which may negatively affect bone.
• Examining the mechanisms of bone cell stimulation from the flow of surrounding fluids during compression (loading) of the bone. As the bone is repeatedly compressed due to physical activity, fluid flows in a network of spaces; this oscillating fluid flow is a potent stimulator of bone cells.
• Comparing recovery times from tibial stress fracture in subjects treated with active or placebo-controlled electric field stimulation, including evaluation of male and female responses.
• Assessing the fracture healing impact of pulsed ultrasound.
• Attempting to accelerate stress fracture healing time using conservative but generally favored treatments of rest from weight bearing activity (this averages three months).
With DOD’s critical investment support, the findings are already impressive:
• Poor physical fitness when recruit training is initiated has been identified as a strong predictor of injury. This has led to the development of a scientifically based intervention to reduce injuries at the Marine Corp Recruit Depot. An evaluation of this intervention demonstrated an overall reduction in overuse injuries and a 50% reduction in stress fractures, with no decrement in physical fitness at graduation.
• Muscle elasticity – as measured by ultrasound – has been shown to undergo physiological alterations with an abrupt transition to a running training program similar to that employed for military recruit training. MRI allows for imaging of soft tissue and can detect these alterations in muscle structure during running. Combining ultrasound characterization with MRI scanning of the muscle recruitment during running will ultimately enable physicians to pinpoint the relationship of muscle elasticity to the level of tibial stress, and, ultimately, fracture risk.
• Being able to assess metabolism and bone growth in humans will advance our understanding of bone remodeling: key to building and maintaining strong bone. DOD-funded scientists have developed a prototype of the highest resolution positron emission tomography (PET) devise existing to focus on meeting this need for improved assessment.
• Data suggests that increased bone remodeling precedes the occurrence of bone microdamage and stress fractures. Researchers found that increases in cortical bone porosity precede the accumulation of bone microdamage, suggesting an important role of increased intracortical remodeling in the development of stress fractures. If we can detect this porosity before microdamage occurs, we could prevent stress fractures.
Areas of Need
• Improved and more sensitive methods are needed for the noninvasive assessment of bone metabolism along with standard measurements of bone density and other parameters of bone strength to assess normal bone remodeling, impending risk of bone injury, and bone responses to treatment interventions.
• Structural and biomechanical factors that contribute to tibial stress fracture risk need to be explored using recent advances in technology to detect microscopic damage to tibial bone structure non-invasively, before occurrence of stress fracture injuries.
• We need to determine the relationship between whole bone geometry and tissue fragility in the human tibia, testing the linkage between geometry, gender, and the occurrence of low- impact bone fractures (those that occur with minimum force).
• DOD scientists’ research in genetic determinants of bone quality may ultimately help protect women and men against musculoskeletal injuries. Bone mineral density, while a major determinant of bone strength, is just one parameter of bone quality. Both geometric characteristics and density of bone are related to bone strength, and muscle strength and endurance have been linked to the ability of bone to withstand repetitive loading. Thus, susceptibility to stress fracture clearly has both bone and muscle components. Research on the effects of genetics, diet and nutrition, mechanical load, and other factors that might affect bone quality can now be studied using new technologies, such as magnetic resonance imaging, peripheral quantitative computed tomography, regional DXA, and tibial ultrasound, and has the potential to provide great insight into the bone remodeling and adaptation process. In addition, new techniques such as virtual bone biopsies are under development to provide more critical data.
Mr. Chairman, stress fractures and other bone related injuries erode the physical capabilities and reduce the effectiveness of our combat training units, compromising military readiness. A small investment in bone health research can make a large contribution to combat readiness. Therefore, it is imperative that the Department of Defense build on recent findings and maintain an aggressive and sustained bone health research program at a level of $6 million in FY 2005.
