Vibrational characteristics of bone fracture and fracture repair: application to excised rat femur.
BACKGROUND
The vibrational characteristics of any object are directly dependent on the physical properties of that object. Therefore, changing the physical properties of an object will cause the object to adopt changed natural frequencies. A fracture in a bone results in the loss of mechanical stability of the bone. This change in mechanical properties of a bone should result in a change of the resonant frequencies of that bone. A vibrational method for bone evaluation has been introduced.


METHODS
This method uses the radiation force of focused amplitude-modulated ultrasound to exert a vibrating force directly, and remotely, on a bone. The vibration frequency is varied in the range of interest to induce resonances in the bone. The resulting bone motion is recorded and the resonance frequencies are determined. Experiments are conducted on excised rat femurs and resonance frequencies of intact, fractured, and bonded (simulating healed) bones are measured.


RESULTS
The experiments demonstrate that changes in the resonance frequency are indicative of bone fracture and healing, i.e., the fractured bone exhibits a lower resonance frequency than the intact bone, and the resonance frequency of the bonded bone approaches that of the intact bone.


CONCLUSIONS
It is concluded that the proposed radiation force method may be used as a remote and noninvasive tool for monitoring bone fracture and healing process, and the use of focused ultrasound enables one to selectively evaluate individual bones.
Alizad
Azra
A
Department of Physiology and Biomedical Engineering, Mayo Clinic College of Medicine, 200 First Street SW, Rochester, MN 55905, USA. aza@mayo.edu
Walch
Matthew
M
Greenleaf
James F
JF
Fatemi
Mostafa
M
D000818:Animals; D005264:Femoral Fractures / Q000000981:diagnostic imaging* / Q000503:physiopathology*; D017102:Fracture Healing / Q000502:physiology*; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D066298:In Vitro Techniques; D010812:Physical Stimulation / Q000379:methods*; D051381:Rats; D014463:Ultrasonography / Q000295:instrumentation / Q000379:methods*; D014732:Vibration