Rajapakse et al. studied the effectiveness of low-intensity vibration (LIV) on bone mineral density (BMD) in people with renal osteodystrophy. Renal osteodystrophy is a disease commonly seen in patients with end-stage renal disease (ESRD). Although the pathophysiology is not fully understood, decreased renal function often leads to bone demineralization. The presumed mechanism of demineralization is related to the decrease in renal function. Changes in vitamin D metabolism in chronic kidney disease (CKD) and the decrease in renal calcitriol synthesis lead to decreased calcium absorption . The decreased absorption of calcium causes increased parathyroid hormone levels which, in turn, causes the resorption of calcium from the bone . As a result of the demineralization, bones are much more susceptible to fracture in areas such as the hip. In addition, these fractures are associated with increased morbidity and mortality rates among those with ESRD . Patients on renal dialysis are on a large number of drugs for their renal disease. A nondrug method to strengthen the skeleton could prove to be beneficial. Rajapakse et al. evaluate the effectiveness of low-magnitude, high-frequency vibration therapy to mitigate bone deficits by evaluating different parameters of bone integrity, muscle response, and patient compliance.
Currently, treatments for osteodystrophy in patients with ESRD are mostly pharmacological. Different classes of drugs are used to compensate for the deficits in the physiologic mechanisms of maintaining calcium and phosphate homeostasis. These drugs include vitamin D supplements, phosphate binders, and antiresorptive drugs. Supplemental vitamin D helps with the absorption of calcium. Indirectly, vitamin D helps stabilize PTH levels. However, the efficacy of these drugs has not been proven . In patients with advanced disease, these drugs may be ineffective . For example, severe hyperparathyroidism, which can be caused by renal failure, can become resistant to clinical therapy . An additional study done also showed the ineffectiveness of calcitriol . One study indicated the increased hypercalcemic risk associated with calcitriol is concerning . The ambiguous benefits and possible risks of taking calcitriol and vitamin D receptor activators call for a new, safer method of renal osteodystrophy therapy. Phosphate binders reduce the amount of phosphate that is absorbed into the blood by binding it within the gut. Phosphate binders can be calcium, magnesium, or aluminum based. Risks associated with these binders include harmful levels of calcium, magnesium, and aluminum in the blood . Antiresorptive drugs, such as bisphosphonates, inhibit bone resorption by stabilizing the calcium phosphorous surface of the bone and also by inhibiting the activity of osteoclasts . Bisphosphonates are not as effective in patients with low bone turnover, which is more common in patients with severe (stages 4–5) CKD. The benefits of bisphosphonate, antiresorptive drugs is limited in patients with severe CKD because some of these patients have significantly diminished bone turnover .
Rajapakse et al. are evaluating vibration therapy as a safe and effective, nondrug treatment for renal osteodystrophy. Vibration therapy is variably referred to as LIV, whole-body vibration or low-magnitude, high-frequency vibration . Patients stand on a low-magnitude, high-frequency vibrating plate for a brief period of time, commonly 20 minutes . This type of vibration has been established as safe, but high-intensity vibrations could have adverse effects on frail bones . Like exercise, vibration therapy causes bone and muscle to strengthen, and historically this was studied for astronauts . Muscle atrophy occurs rapidly in space while bone demineralization occurs gradually in a microgravity environment over an extended period of time . Astronauts are prescribed 2-hour workout sessions per day to combat muscle atrophy, and now LIV is being studied to help prevent bone demineralization . In addition to astronauts, the effects of vibration therapy have been studied on a wide range of patients. Positive results have been shown not only in young healthy adults, but also in postmenopausal women and people with cerebral palsy or muscular dystrophy . However, studies on the effects of vibration therapy on patients with renal osteodystrophy are lacking.
One of the few double-blind placebo controlled studies in patients with renal osteodystrophy was performed by Jones et al. In their abstract presented at the 2007 American Society for Bone and Mineral Research Convention, they studied the structural implications of vibration therapy on patients on dialysis. After 6 months of treatment, micro-magnetic resonance imaging (MRI) scans were performed in the distal tibia metaphysis, and postprocessing analysis was performed. This limited pilot study demonstrated improvement in bone trabecular connectivity, suggesting improved bone quality . This was a very preliminary study using MRI only in the distal tibia, and it was not followed up with a more systematic evaluation.
Although minimal research has been done regarding renal osteodystrophy specifically, vibration therapy has been tested more extensively on patients with osteoporosis, especially postmenopausal women. In a study done by Rubin et al., a slight benefit was demonstrated in the treated group. In this 1-year prospective, randomized, double-blind, and placebo-controlled trial, vibration therapy inhibited the decline in BMD that follows menopause. The benefit was seen in the hip and the spine. However, only dual-energy X-ray absorptiometry (DXA) was used to measure BMD. Compliance with treatment was also analyzed, and a significant effect of compliance on effectiveness of the vibration treatment was demonstrated . Meta-analysis has shown that in postmenopausal women, adolescents, and children, LIV had a small but significant effect. For young adults, no significant benefit was demonstrated .
The study conducted by Rajapakse et al. was one of the first using vibration therapy to treat renal osteodystrophy. The pilot study contained a small sample size of 15 subjects in the placebo group and 15 subjects in the treatment group. Compliance varied significantly within each of these small groups, and the final analysis demonstrated that the efficacy of treatment is highly dependent on compliance. Much of the research has been performed on animals such as sheep and mice . Similar studies on humans evaluating the efficacy of LIV have mainly focused on osteoporosis. Although Rubin et al. studied a larger cohort for a longer period of time, their evaluation was limited to DXA. In contrast, Rajapakse et al. have used multiple complementary modalities including DXA, MRI, and computed tomography. In addition, they used more advanced analysis of the acquired data to evaluate not just BMD but also trabecular patterns and tibial stiffness. Furthermore, evaluation of calf muscle cross-sectional area provided important information. Another unique element of this was the correlation of PTH levels with bone changes. Like most studies, Rajapakse et al. excluded comorbidities. However, most other studies excluded renal osteodystrophy as a comorbidity. One of the few studies evaluating patients with renal osteodystrophy was performed by Jones et al. This study evaluated only trabecular patterns in the proximal tibia using MRI.
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