An Ultrasound Wearable System for the Monitoring and Acceleration of Fracture Healing in Long Bones

Abstract

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.

Ultrasonic evaluation of intact, healing and osteoporotic long bones

“…It was found that ultrasound propagation velocity increases, while the broadband ultrasound attenuation decreases as the healing process evolves (Floriani et al 1967, Barbieri et al 2011, Protopappas et al 2005. Specifically, in (Protopappas et al 2005) we demonstrated that velocity measurements after 100 days of a sheep osteotomy exceed on average 80% the corresponding intact bone value, while in (Floriani et al 1967) measurements at the 6 th postoperative month on guinea pigs revealed that for completely healed bones the velocity approximated the ratio 94% of the intact bone, respectively. Concerning the early detection of complications, we showed in (Protopappas et al 2005) that the velocity across bones which finally reached bony union was higher than for those with complications even from the 50 th postoperative day.…”

“…Specifically, in (Protopappas et al 2005) we demonstrated that velocity measurements after 100 days of a sheep osteotomy exceed on average 80% the corresponding intact bone value, while in (Floriani et al 1967) measurements at the 6 th postoperative month on guinea pigs revealed that for completely healed bones the velocity approximated the ratio 94% of the intact bone, respectively. Concerning the early detection of complications, we showed in (Protopappas et al 2005) that the velocity across bones which finally reached bony union was higher than for those with complications even from the 50 th postoperative day. Additionally, the study of (Ferreira et al 2010) on pseudarthrosis in rats showed that AIB values for pseudarthrosis were higher comparing to intact bone.…”

“…After animal euthanasia, bone densitometry and three-point bending were additionally performed. It was found that the measured velocity at the end of the follow-up period was significantly correlated with the square root of the Young modulus, the ultimate strength of the healing bones and callus density (Protopappas et al 2005). However, the material and mechanical properties of healed bones reached lower values comparing to the reference values for intact bones.…”

“…In Protopappas et al (2005) and Malizos et al (2006), a system was proposed for the ultrasonic monitoring of fracture healing which was applied on a sheep tibial osteotomy with an external fixation device. The system consisted of a pair of miniature implantable ultrasound transducers, a wearable device and a centralized unit (Fig.1).…”

“…1. Wearable system for the ultrasonic monitoring of bone healing (Protopappas et al 2005) ultrasound measurements were conducted at 1 MHz. Initially, velocity measurements for the intact bones were derived which were used as reference values.…”