Finding better ways to prevent bone loss in people with spinal cord injuries

For Dr. Catharine Craven, it was an unforgettable episode — wheelchair athletes doing a marathon each day for five consecutive days. "They raced over awful terrain in extreme weather conditions to raise awareness about what it was like to live with their disability," recalls Dr. Craven.

That scene still inspires her today. "It reminds me what I'm here for," says Dr. Craven, a researcher-clinician in Toronto Rehab's spinal cord rehabilitation program.

Dr. Craven's interest in spinal cord injury began early in life. "I refereed wheelchair basketball, and I was intrigued by the people I met and the issues that affected them. Later, my mentors at medical school encouraged me to do research in osteoporosis. The two interests converged."

Dr. Craven is a physiatrist — a physician who specializes in physical medicine and rehabilitation. Her primary research focus is the prevention and treatment of osteoporosis (thinning of the bone) after spinal cord injury. She is also investigating how exercise affects the health of people with this kind of injury.

Studies show that people with spinal cord injuries lose up to one-third of their bone density within a year of injury. "That's equivalent to the bone loss experienced by a women over a 10-year period starting at menopause," says Dr. Craven, Manager of the Bone Density Lab in the hospital's spinal cord rehabilitation program.

Much of Dr. Craven's research involves understanding the relationship between spinal cord injury and osteoporosis. "If you immobilize astronauts in space, they lose bone," says Dr. Craven. "But when they return to Earth and normal activity, the bone comes back. However, when spinal cord injury patients become active again after months of immobilization, the bone doesn't come back."

It's important to learn why because bone loss makes people with spinal cord injuries very prone to hard-to-heal fractures. These fractures can lead to weeks of hospitalization, lost work time, family time and functional independence.

Dr. Craven's research group is one of only two teams in North America tackling this problem of bone density loss. "As researchers learn more about the cells responsible for bone growth, and as our technology gets better, we're starting to understand what's happening in people with spinal cord injury."

Dr. Craven has harnessed new imaging technology to develop a leading-edge tool for measuring bone density around the knee. "Using this tool, we've shown that people with spinal cord injury have 50 per cent less lower extremity bone mineral there than their peers. Until recently, we couldn't quantify the risk."

Dr. Craven and her colleagues are also involved in the first large, multi-centre trial of a drug called risedronate to try and turn off bone loss before it occurs.

With neuroscientists edging closer to "exciting new possibilities for cure" for spinal cord injuries, it's even more important that people with these injuries maintain good bone density, says Dr. Craven. "If you don't have a skeleton to hold you up, you won't be able to take advantage of this."

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