OSTEOGENIC MECHANICAL STIMULI-PREVENT/REVERSE BONE LOSS
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Therapies which increase bone formation are highly desirable, yet few are available, and those under investigation, have significant disadvantages. Extremely low magnitude (less than 10 microstrain) biomechanical stimuli, intended to supplant the deterioration of muscle dynamics which parallel the aging process, can be introduced non-invasively into the skeleton as a non-pharmacologic means of increasing bone mass and strength. In animal studies, we have demonstrated that short periods (less than 30 min) of mechanical loading, applied at a relatively high frequency (15-90 Hz), will increase trabecular volume and number, mineral apposition rate and labeled surface, and will decrease trabecular spacing. Moreover, a one-year double-blind placebo controlled clinical trial of mechanical stimulation in 55 post- menopausal women, exposed to short duration (20 minute), low magnitude (0.2 g), 30 Hz mechanical stimuli demonstrated that lumbar spine bone mineral density (BMD), normalized for body weight, declined by 3.3 percent BMD in the control group compared to only 0.8 percent in the treated group. Similarly, in the trochanter region of the hip, a 2.8 percent loss was observed in the control group while the treated group experienced a 0.4 percent gain. Stratified for body mass index, it was clear that the efficacy of treatment was greatest in thinner women (BMI less than 24 K g/m2). The biomechanical stimulation was very well tolerated. The central hypothesis of this proposal is that osteogenic mechanical stimulation (0.3g at 30 Hz for 10 minutes daily) will effectively inhibit the rapid bone loss that immediately follows the menopause, and will serve to reverse bone loss in a population of frail elderly women. These two principal hypotheses will be addressed in a prospective, double blind, multi-center trial in which two experimental groups will be studied: women 1-6 years past the menopause (100 subjects), and women greater than 70 years of age (50 subjects). The recently menopausal women will have a hip T-score (TOTAL, neck, trochanter or intertrochanter) between -0.5 and -1.5 while the elderly participants will have T-scores less than -1.5. All women will be of thin body stature (body mass index below 26 kg/m2). In the feasibility trial, described above, it was women of this body and BMD status that were most responsive to the biomechanical treatment. The primary outcome variable, bone mineral density at the hip, will be measured at baseline and at 12-month intervals for three years. Secondary outcome variables will include BMD at the spine, and indices of bone formation and resorption, as well as the effect of these interventions upon postural stability, another key risk factor for fracture. We anticipate that the results of this study will demonstrate the attributes of a unique osteogenic biomechanical therapy for osteoporosis.
