Ultrasound produced by a conventional therapeutic ultrasound unit accelerates fracture repair.
OBJECTIVE
A recent novel application of ultrasound therapy is the treatment of bone fractures. The aim of this study was to investigate the effect on fracture repair of ultrasound produced by a conventional therapeutic ultrasound unit as used by physical therapists.


METHODS
Bilateral midshaft femur fractures were created in 30 adult male Long-Evans rats. Ultrasound therapy was commenced on the first day after fracture and introduced 5 days a week for 20 minutes a day. Each animal was treated unilaterally with active ultrasound and contralaterally with inactive ultrasound. Active ultrasound involved a 2-millisecond burst of 1.0-MHz sine waves repeating at 100 Hz. The spatially averaged, temporally averaged intensity was set at 0.1 W/cm2. Animals were killed at 25 and 40 days after fracture induction, and the fractures were assessed for bone mass and strength.


RESULTS
There were no differences between fractures treated with active ultrasound and fractures treated with inactive ultrasound at 25 days. However, at 40 days, active ultrasound-treated fractures had 16.9% greater bone mineral content at the fracture site than inactive ultrasound-treated fractures. This change resulted in a 25.8% increase in bone size, as opposed to an increase in bone density, and contributed to active ultrasound-treated fractures having 81.3% greater mechanical strength than inactive ultrasound-treated fractures.


CONCLUSIONS
These data indicate that ultrasound produced by a conventional therapeutic ultrasound unit as traditionally used by physical therapists may be used to facilitate fracture repair. However, careful interpretation of this controlled laboratory study is warranted until its findings are confirmed by clinical trials.
Warden
Stuart J
SJ
Department of Physical Therapy, Indiana University, CF-326, Indianapolis, IN 46202, USA. stwarden@iupui.edu
Fuchs
Robyn K
RK
Kessler
Chris K
CK
Avin
Keith G
KG
Cardinal
Ryan E
RE
Stewart
Rena L
RL
D000818:Animals; D001696:Biomechanical Phenomena; D015519:Bone Density; D005264:Femoral Fractures / Q000000981:diagnostic imaging / Q000628:therapy*; D017102:Fracture Healing / Q000502:physiology*; D008297:Male; D011859:Radiography; D051381:Rats; D020318:Rats, Long-Evans; D018709:Statistics, Nonparametric; D013314:Stress, Mechanical; D014464:Ultrasonic Therapy / Q000295:instrumentation*