Vibration and Bone Healing

[Guest guest]

Here is more information on the effects of mechanical vibration on the body,

in this case the enhanced healing of the bones.

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Anabolism. Low mechanical signals strengthen long bones.

Rubin C, AS, Bain S, Mallinckrodt C, McLeod K Nature 2001 Aug

9;412(6847):603-4

Although the skeleton's adaptability to load-bearing has been recognized for

over a century, the specific mechanical components responsible for

strengthening it have not been identified. Here we show that after

mechanically stimulating the hindlimbs of adult sheep on a daily basis for a

year with 20-minute bursts of very-low-magnitude, high-frequency vibration,

the density of the spongy (trabecular) bone in the proximal femur is

significantly increased (by 34.2%) compared with controls. As the strain

levels generated by this treatment are three orders of magnitude below those

that damage bone tissue, this anabolic, non-invasive stimulus may have

potential for treating skeletal conditions such as osteoporosis. conditions

such as osteoporosis. conditions such as osteoporosis conditions such as

osteoporosis.

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The Use of Low-Intensity Ultrasound to Accelerate the Healing of Fractures

C Rubin, M Bolander, JP Ryaby, M Hadjiargyrou J of Bone & Joint Surgery

83:259 (2001)

Introduction

Double-blind, prospective, placebo-controlled clinical trials demonstrate

that healing times of fresh fractures of the radius and tibia are reduced by

up to 40% with the use of low-intensity ultrasound.

Animal studies indicate that low-intensity ultrasound exposure results in

stronger and stiffer callus formation and in acceleration of the endochondral

ossification process.

Extensive clinical evidence demonstrates that ultrasound represents a safe,

noninvasive method of accelerating the healing of fresh fractures of the

tibia, the distal aspect of the radius, the scaphoid, and the metatarsals.

Clinical studies indicate that ultrasound reduces the confounding effect of

smoking and patient age on the fracture-healing process.

Ultrasound requires a brief, twenty-minute, daily at-home treatment regimen

and has no known contraindications.

The effectiveness of low-intensity ultrasound has also been demonstrated in

the clinical treatment of delayed unions and nonunions.

Fracture-healing is a complex biological process that involves the spatial

and temporal orchestration of numerous cell types, hundreds if not thousands

of genes, and the intricate organization of an extracellular matrix, all

working toward restoring the bone's mechanical strength and rapid return to

full function. It has often been argued that nature has optimized this

process and thus it would be difficult to interventionally accelerate or

augment fracture-healing. How can science conceivably improve upon 600

million years of vertebrate evolution?

Nevertheless, it is just this goal that has inspired an intense effort among

basic-science and clinical investigators from a vast array of biotechnology

and bioengineering disciplines at academic as well as industrial

laboratories, to seek a means of accelerating the healing of fractured bones.

In this article, the basic-science and clinical evaluation of the use of

low-intensity ultrasound is reviewed and the case is made that nature's

process of fracture-healing, while elegant, can be accelerated with respect

to achieving the ability to support clinically relevant loads.

The Food and Drug Administration approved the use of low-intensity ultrasound

for the accelerated healing of fresh fractures in October 1994 and for the

treatment of established nonunions in February 2000. The first regulatory

approval was based primarily upon two rigorous, double-blind,

placebo-controlled clinical trials, which showed that the rate of healing of

fresh fractures is accelerated by treatment with ultrasound1,2. In concert

with these clinical studies, substantive basic-science data demonstrated that

ultrasound has a strong positive influence on each of the three key stages of

the healing process (inflammation, repair, and remodeling) because it

enhances angiogenic, chondrogenic, and osteogenic activity. Complementing the

basic-science and clinical data is accumulating evidence that ultrasound has

a role in the treatment of delayed unions and nonunions as well as in the

reduction of overall costfactors that ultimately must be considered in the

clinical-outcome equation........

Overview

On the basis of a broad spectrum of laboratory and clinical studies, several

biological mechanisms (direct and indirect) have been proposed to explain the

influence of ultrasound on the acceleration of the fracture-repair process.

Data from various in vitro studies suggest that ultrasound may induce

conformational changes in the cell membrane and thus alter ionic permeability

45,46 and second messenger activity47,48. Changes in second messenger

activity could then conceivably lead to downstream alterations in gene

expression, resulting in an acceleration of the fracture-repair process by

upregulating cartilage and bone-specific genes as well as others.

Rawool et al.56 reported that ultrasound also stimulates angiogenesis, thus

increasing blood flow to the fracture site and inherently delivering the key

components, such as growth factors and cytokines, that are necessary for the

normal healing process. Yang et al.54 and Nolte et al.40 suggested that

ultrasound stimulates chondrogenesis and cartilage hypertrophy, resulting in

an earlier onset of endochondral formation and thus leading to an increase in

stiffness and strength of the fracture site, as noted by Wang et al.38.

While the mechanism of ultrasound interaction with the wound response may not

be defined, it is clear that the fracture-repair process is extremely complex

and that a host of cells, genes, and other regulatory factors (for example,

cytokines and functional load-bearing), many of which may be influenced by

the ultrasound signal, work together during the healing process.

A large repository of basic-science and clinical work suggests a means by

which fracture-healing can be augmented by low-intensity ultrasound.

Considering the number of ways in which the healing process can be disrupted,

a potential advantage of ultrasound treatment is that it does not overtly

depend on a singular mechanism or on a single phase of the healing process.

Instead, it appears to influence several aspects of the healing process in

the inflammatory, reparative, and remodeling phases. Since the intervention

is noninvasive, it could be argued that ultrasound represents a combination

of conservative and aggressive treatment that encourages the normal process

of healing.

That conclusion is supported by a recent study, by Heckman and Sarasohn-Kahn79

, on the economic benefits of treating tibial fractures with low-intensity

ultrasound. Considering the number of these fractures that advance to

nonunion, there could be an estimated overall cost-savings of between $13,000

and $15,000 per case (including the cost of the ultrasound therapy)

associated with the use of low-intensity ultrasound.

The fracture-repair process is sophisticated yet primal, delicate yet robust.

It involves many interdependent stages, and it relies on temporal and spatial

orchestration of a wide array of genes and cell types. A complex injury, or a

systemic state that compromises the healing process, is associated with a

higher risk of delayed union and nonunion as well as with the potential for

diminished function, and this accentuates the need to consider proven

interventions.The use of ultrasound, through a variety of mechanisms, some

biological and some physical, can culminate in a fracture-healing process

that is both accelerated and augmented. Ultimately, however, ensuring that

the process is completed is the most critical goal..........

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Dr Mel C Siff

Denver, USA

Supertraining/