Building Stronger Bones
Loss of bone density is a concern commonly associated with the elderly, for whom a simple stumble can easily result in a painful, debilitating fracture. But a variety of other conditions can make low bone density a lifetime challenge, one best addressed as early as possible.
The best-known condition associated with fragile bones is osteogenesis imperfecta, a genetically-based disorder characterized by abnormally brittle bones that affects from 20,000 to 50,000 people in the United States alone. For the past five-years, Kennedy Krieger Institute's Osteogenesis Imperfecta (OI) Clinic has focused on treating the symptoms of OI and ensuring the best quality of life possible for those that have it through a comprehensive array of services including physical therapy, orthotics, pharmacological treatment, nutritional guidance and social work.
In addition to osteogenesis imperfecta, low bone density can also affect patients with traumatic brain and spinal cord injuries, spina bifida, cerebral palsy (CP), and certain inherited metabolic disorders such as Rett Syndrome. "With OI, the underlying issue causing the low bone density is related to the production and synthesis of Type I collagen, which is the main protein involved in producing bone and other connective tissues," says Dr. Jay Shapiro, a specialist in internal medicine and endocrinology and director of the OI Clinic. "In many of these conditions, the problem occurs when a child has difficulty bearing their own weight. The rapid loss of muscle tone leads to reduced strain on the bones, which is important for bone development. When a disability involves mobility, the individual loses the effect of gravity on bone and bone cells, too. The same thing happens to astronauts in microgravity." In many of the disorders seen at the Kennedy Krieger Institute there are also genetic or metabolic factors that add to bone loss.
As with OI, the low bone density experienced by many patients with these conditions can lead to frequent, severe fractures, even in normal, daily activities. What's more, the nature of the fractures can require surgical treatment, which has its own set of complications.Long-term casting can put the development of neighboring muscles and bones at risk, while forcing children to avoid normal, age-appropriate activities can lead to depression.
Dr. Shapiro says that dual energy X-ray absorptiometry, a low-radiation scan that measures bone density, should be part of the standard evaluation for patients with limited mobility and weight-bearing ability. If a problem is detected, treatment can begin sooner and additional complications can be reduced. Currently, treatment for low bone density relies on several main agents: calcium and Vitamin D replacements and a drug class known as bisphosphonates. These drugs are often used to treat osteoporosis in the elderly and are known to be effective in slowing bone loss. Since many of these conditions also involve delayed puberty, the replacement of hormones such as estrogen or testosterone may be helpful in adolescents.
Careful monitoring of the impact of treatment is important, says Dr. Shapiro. "Calcium and Vitamin D supplements can be helpful, but patients with OI can be at higher risk for kidney stones, so it's important not to overdo it." To aid caregivers, Dr. Shapiro and Kennedy Krieger nutritionist Eileen McMahon, R.D. recently published revised guidelines for administering Vitamin D supplements to children with OI.
In some cases treatment plans can also include physical therapy as well as specific rehabilitation therapies such as functional electric stimulation for individuals whose immobility is caused by a spinal cord injury.
While there is no known cure for OI or most of the other conditions associated with low bone density, a vigorous treatment plan can increase bone mass and decrease the risk of fractures. A number of Institute research projects are attempting to improve treatments. The OI Clinic's current studies include a look at how nutrition is related to growth and bone mass, an investigation of the effects of the parathyroid drug Forteo in adults with OI, and a planned trial of Zometa, a more potent, longerlasting bisphosphonate.
"These projects are approaching the issue of how to improve bone density from a number of angles," says Dr. Shapiro. "Children with OI frequently experience significant feeding difficulties, so it's possible that inadequate nutrition is exacerbating the chemical deficiencies that lead to their bone loss. Unfortunately, bisphosphonates don't have the same impact on adults with OI as they do with children, so the Forteo study is an attempt to find an effective treatment for that population. With Zometa, we're hoping to find a way to treat low bone density effectively, with a more potent group of drugs."
According to Dr. Shapiro, aggressive treatment of bone loss can improve patients' quality of life dramatically. "For too many years, no one paid attention to the effect disorders like CP and spina bifida had on bone density. But we see the results of bone fragility, the fractures, in many patients. Bone loss is not uncommon in children with neurological or musculoskeletal disabilities. It's important to do the scans, blood tests and other groundwork to pave the way for effective treatment," he says.
For more information on conditions associated with low bone density, please call 443-923-9400 or visit the Osteogenesis Imperfecta Clinic's website at www.osteogenesisimperfecta.org.