Acoustic Emissions Testing for Occult Pediatric Fractures and Stress Fractures
Principle Investigator: Kathleen McHale
Co-investigators: Jihui Li, Mark Theiss, Samuel Hawken
Funded by: Inova Health System
Some fractures do not routinely show up on initial X-rays. These common fractures are
- Toddlers’ fractures, i.e. occult fractures of the tibia in walking age children
- Salter-Harris fractures, i.e. fractures through the physis particularly at the ankle and the wrist
- Stress fractures in older children and adults from cyclical loading
Stress fractures of the tibia and of the metatarsals in adults often have normal initial X-rays. Often, X-rays are negative until signs of healing (toddlers’ or S-H fractures) or progression (stress fractures) take place. Diagnostic tools such as bone scans, CT scans, and MRI can be costly, time consuming, and require sedation (MRI). Non-invasive, inexpensive tools have been developed for occult, partial structural failure, i.e. ultrasound and acoustic emissions. Ultrasound (US) is an active acoustic inspection technique in which the sound wave is directed at an area of interest; if it intersects a crack or other discontinuity, a reflected wave is returned. It is performed on an unloaded structure. It has been shown to be good for large diaphyseal long bone fractures in children but is less dependable for juxta-articular and Salter-Harris fractures, lesions of the small bones of the hands and feet, fracture lines less than one millimeter, and for stress fractures. Acoustic emission (AE) is a method of inspection in which a generation of transient elastic waves is produced by a sudden redistribution of stress in a material. When a structure is subjected to an external stimulus, e.g. change in pressure, localized sources trigger the release of energy in the form of stress waves, which propagate to the surface and are recorded by sensors. AE technique enables the nondestructively detection and monitoring loading-induced “microcracks” in real time. The proposed research will investigate the use of AE in the detection and monitoring of occult fractures in children that are not difficult to diagnose by initial plain X-ray. The goal of this research is to develop AE as a diagnostic tool that can be used in the office setting to confirm the presence of a subtle fracture in the pediatric population. Additional benefit will be the minimization of radiation exposure, cost, and time to diagnosis.