Low-intensity transosseous ultrasound accelerates osteotomy healing in a sheep fracture model

Comparative Study of How Low-Level Laser Therapy and Low-Intensity Pulsed Ultrasound Affect Bone Repair in Rats

OBJECTIVE

This study aimed to compare the consequences of low-level laser therapy (LLLT) and low-intensity pulsed ultrasound (LIPUS) on bone repair.

BACKGROUND DATA

Many studies have assessed the effects of LLLT and LIPUS on bone repair, but a comparison of them is rare.

METHODS

Male Wistar rats (n = 48) with tibial bone osteotomy were used. One group had the osteotomized limb treated with LLLT (GaAlAs laser, 780 nm, 30 mW, 112.5 J/cm(2)) and the second group with LIPUS (1.5 MHz, 30 mW/cm(2)), both for 12 sessions (five times per week); a third group was the control. After 20 days, rats were sacrificed and had their tibias submitted to a bending test or histomorphometric analysis.

RESULTS

In the bending test, maximum load at failure of LLLT group was significantly higher (p < 0.05). Bone histomorphometry revealed a significant increase in osteoblast number and surface, and osteoid volume in the LLLT group, and a significant increase in eroded and osteoclast surfaces in the LIPUS group.

CONCLUSION

LIPUS enhanced bone repair by promoting bone resorption in the osteotomy area, while LLLT accelerated this process through bone formation.

Transosseous application of low-intensity ultrasound for the enhancement and monitoring of fracture healing process in a sheep osteotomy model

The purpose of this study is twofold: (a) to investigate the application of transosseous low-intensity pulsed ultrasound (LiUS) on the enhancement of fracture healing and (b) to demonstrate the ability of transosseous ultrasound propagation to monitor the healing process. A midshaft tibial osteotomy model was used on 40 skeletally mature sheep, and an external fixator was applied to maintain the reduction and stabilization of the osteotomy. Two ultrasound transducers were implanted into the fracture site in contact with the bone. For investigating the efficacy of LiUS, the animals were randomly divided in two equal groups: the treatment group and the control group. The LiUS-treated animals received 200-micros bursts of 1-MHz sine waves with a pulse repetition rate of 1 kHz and average intensity of 30 mW/cm2, for 20 min daily. For monitoring purposes, an ultrasound dataset was constructed consisting of serial ultrasound measurements obtained from healing bones. Animals' sacrifice took place on the 100th post-operative day. The effect of LiUS on fracture healing was evaluated using radiographs, destructive three-point bending testing and quantitative CT-based bone mineral density (BMD) measurements. Survival analysis using Kaplan-Meier curves showed significantly higher probability of radiographic healing for the animals in the treatment group (P = 0.009). Statistical significance was also observed for callus BMD (P = 0.003, Wilcoxon nonparametric test), the breaking load (P = 0.001), extrinsic stiffness (P = 0.019), Young's modulus (P = 0.043) and ultimate strength (P = 0.051) in favor of the LiUS-treated limbs. Analysis of the obtained ultrasonic measurements showed that the propagation velocity across healing bones constitutes a significant feature able to early distinguish between healed and nonhealed bones (area under ROC curve was 0.810 and 0.841 on the 80th and 100th post-operative days, respectively). Both the LiUS application and the ultrasonic measurements are supported by an integrated telemedicine system which also incorporates an ultrasound wearable device and a patient management system.

Low-intensity pulsed ultrasound for bone healing: an overview

Low-intensity ultrasound is a biophysical form of intervention in the fracture-repair process, which through several mechanisms accelerates healing of fresh fractures and enhances callus formation in delayed unions and nonunions. The goal of this review is to present the current knowledge obtained from basic science and animal studies, as well as existing evidence from clinical trials and case series with the different applications of ultrasound in the management of fractures, delayed unions, nonunions and distraction osteogenesis. Low-intensity pulsed ultrasound is currently applied transcutaneously, although recent experimental studies have proven the efficacy of a trans-osseous application for both enhancement and monitoring of the bone healing process with modern smart implant technologies.

The healing potential of the periosteum molecular aspects

The presence of pluripotential mesenchymal cells in the under surface of the periosteum in combination with growth factors regularly produced or released after injury, provide this unique tissue with an important role in the healing of bone and cartilage. The periosteum contributes in the secondary callus formation with cells and growth factors and should always be preserved and protected when surgery is performed for the management of a fracture. The current evidence about the cellular interactions, the stimulants and the signalling pathways related to osteogenesis and chondrogenesis is described. An essential knowledge of the basics related to the contribution of the periosteum in the healing of fractures, osteotomies, during the process of distraction osteogenesis and in some degree in the repair of cartilagenous defects, provides the surgeons with a better insight to understand the upcoming "biological" interventions in the management of skeletal injuries.

An ultrasound wearable system for the monitoring and acceleration of fracture healing in long bones

An ultrasound wearable system for remote monitoring and acceleration of the healing process in fractured long bones is presented. The so-called USBone system consists of a pair of ultrasound transducers, implanted into the fracture region, a wearable device and a centralized unit. The wearable device is responsible to carry out ultrasound measurements using the axial-transmission technique and initiate therapy sessions of low-intensity pulsed ultrasound. The acquired measurements and other data are wirelessly transferred from the patient-site to the centralized unit, which is located in a clinical setting. The evaluation of the system on an animal tibial osteotomy model is also presented. A dataset was constructed for monitoring purposes consisting of serial ultrasound measurements, follow-up radiographs, quantitative computed tomography-based densitometry and biomechanical data. The animal study demonstrated the ability of the system to collect ultrasound measurements in an effective and reliable fashion and participating orthopaedic surgeons accepted the system for future clinical application. Analysis of the acquired measurements showed that the pattern of evolution of the ultrasound velocity through healing bones over the postoperative period monitors a dynamic healing process. Furthermore, the ultrasound velocity of radiographically healed bones returns to 80% of the intact bone value, whereas the correlation coefficient of the velocity with the material and mechanical properties of the healing bone ranges from 0.699 to 0.814. The USBone system constitutes the first telemedicine system for the out-hospital management of patients sustained open fractures and treated with external fixation devices.