ULTRASOUND

Ultrasound

Project Summary

In this research we will assess the repair of transverse, 3-mm wide bone gaps created at the distal radius in 28 rats that were randomly divided into two 14- groups; one was the control group and the other were to receive a daily, 20-min application of low-intensity pulsed ultrasound for 100 days. (Azuma, 2001, 28) Sequential radiographs, histomorphometrics, bone fluorescent histology and bone vascularity assessments found that all rats from both groups obtained a stage of hypertrophic-type non-union with fibrocartilage tissue formation throughout the region of osteotomy. However, treated rats exhibited areas of endochondral ossification within the fibrocartilage region. There will be no difference in type of vascularity or the newly formed bone process obtained by tetracycline labelling. Application of low-intensity ultrasound will not be capable of significantly changing the reparative process and it may not be sufficiently powerful to overcome a combination of local deleterious effects on bone healing, created by gapping, excessive motion and periosteal resection.

Project Description

Introduction

Delayed bone healing is an important issue in orthopaedics and represents the initial condition for pseudarthrosis development. This condition is responsible for a large number of complications, as bone healing does not occur all the time, despite the application of modern surgical techniques. In recent years, low-intensity pulsed ultrasound has been the subject of several studies as a new bone formation stimulator; although it's ultimate mechanism is not completely known. However, it is known that ultrasound stimulates several stages of the bone regeneration process, such as inflammatory reactions, angiogenesis and chondrogenesis (Rumack, 2004).

Literature Review

It will be demonstrated that low-intensity ultrasound stimulation of osteogenesis occurs with mediation of mRNA and growth factors, such as platelet-derived growth factor (PDGF), basic fibroblast growth factor, along with the induction of osteoblast production and increasing aggrecan gene expression. Low-intensity ultrasound can improve the mechanical properties of the bone callus by increasing local alkaline phosphatase and matrix metalloproteinase-13 (MMP-13) levels and by increasing calcium incorporation by bone cells. In addition, there is an induction of early bone formation due to prostaglandin E2 (PGE2) production. (Azuma, 2001)

In terms of human clinical applications, several studies have demonstrated a positive effect of low-intensity ultrasound on the speed of repair of recent fractures and bone healing anomalies. Ultrasound therapy has also been expanded to other conditions, such as the neutralization of the deleterious effects of nicotine on bone repair.

In rat trails, there have been reports of repaired non-union's induced in rat tibiae, healing bone acceleration in sheep osteotomies, bone distractions and bone transport in sheep metatarsals. In opposition, a recent multicentre double-blind controlled trial on the application of pulsed ultrasound on fresh fractures of clavicle did not find any influence on the healing time. (Azuma, 2001)

Despite of the favourable evidence that low-intensity is an effective treatment of bone healing anomalies; some authors did not find benefits in humans and experimental research. A recent systematic review of literature found that more homogenous and larger controlled clinical series are needed for a definitive conclusion. In addition, the limits of low-intensity ultrasound therapy in preventing ...