Stress and weight-bearing pressure helps build bone. Even a night in bed starts the bone loss process, although getting up in the morning reverses the process, the University of Washington Department of Radiology reports. When a person doesn't bear weight on his bones for a period of time, bone loss accelerates and new bone formation slows, lead author Shinjiro Takata of the University of Tokushima, Japan states in the 2001 "Journal of Medical Investigation." Disuse osteoporosis takes a long time to overcome even with medication treatment.
Causes
Anything that keeps a person off his feet for any amount of time can cause disuse osteoporosis, including illness necessitating bed rest, spinal cord injury, paralysis from stroke or fractures. Even conditioned astronauts or people who experience prolonged weightlessness can develop disuse osteoporosis. Prolonged immobility causes increased excretion of calcium in the urine and stool, which also contributes to development of disuse osteoporosis, Jackson Tan, M.D. reports in "Practical Manual of Physical Medicine and Rehabilitation: Diagnostics, Therapeutics and Basic Problems."
Effects
Bed rest for as little as one week results in loss of 1 percent on bone mineral density in the vertebrae, Takata states. Bone mineral density falls by 40 to 45 percent after 12 weeks, and after 30 weeks of immobility, over 50 percent of bone mineral density is lost, according to Tan.Minor trauma or falls can cause fractures in people with disuse osteoporosis. Muscle weakness and atrophy also usually occur in the same area. Disuse osteoporosis most often occurs in cancellous bone, also called trabecular bone. Trabecular bone makes up 66 to 90 percent of the vertebrae and 50 percent of the hip bone around the trochanter, Takata states.
Prevention
Prevention is more effective than treatment of disuse osteoporosis once it occurs. Passive range of motion and non-weight bearing exercises will not prevent disuse osteoporosis without weight-bearing. Early ambulation and use of anti-resorptive medications such as bisphosphonates, along with calcitonin and vitamin K help prevent people at high risk of disuse osteoporosis.
Treatment
Treatments of disuse osteoporosis are similar to those used for prevention. In addition, building and strengthening muscle mass around the damaged area through electrical stimulation helps atrophied bone rebuild, Takata states.
Complications
Disuse osteoporosis can result in an increase in compression fractures in the vertebrae as well as hip fractures from falls or trauma. Fractures of the hip can cause disability and death from postoperative complications, especially in the elderly, MayoClinic.com states.
