There are millions of fractures worldwide each year with an estimated 5-10% resulting in either delayed or nonunion. All told, these injuries constitute the largest cause of morbidity and socioeconomic cost in the developed world. As our population ages it becomes even more important to understand the cellular events associated with fracture repair. Low intensity pulsed ultrasound stimulation (LIPUS) is one of the proposed interventions to both enhance and accelerate bone healing. Traditional use of ultrasound directs energy into the tissues producing heat. At lower intensities, however, there is <1°C of temperature increase. Traditional use of ultrasound continues to be contraindicated at a fracture site whereas low intensity ultrasound has proven to be a benefit in the healing rate of both fresh fractures and delayed or nonunion fractures. Bone tissue is sensitive to the micromechanical stresses of low intensity ultrasound waves. Histologic studies show positive influence on osteoblasts, osteoclasts, chondrocytes and mesenchymal stem cells. Animal model studies demonstrate increased cellular calcium uptake, decreased cytokine release and suggest enhanced angiogenesis and blood flow around the fracture site. Accelerated Healing of Acute Fractures Cook et al. looked at tibial and distal radius fractures of smokers and non-smokers. Participants received either LIPUS or sham ultrasound starting within 7 days of the fracture. In those who received the LIPUS treatment, the healing time of tibial fractures was reduced by 41% in smokers and 26% in non-smokers; the healing time of distal radius fractures was reduced by 51% in smokers and 34% in non-smokers. The end point of the study was a healed fracture as judged by clinical exam and radiographic evidence (3 of 4 cortices bridged). Fractures not healed at 150 days were deemed delayed unions. Delayed union was also reduced in the LIPUS treatment groups: 8% vs. 27% placebo in non-smokers and 0% vs. 36% in smokers. Healing of Delayed and Nonunion Fractures The healing rate for delayed union is higher than that for nonunion. A report on 1370 delayed union cases had a healing rate of 89% whereas 1546 nonunion cases achieved healing in 83% of the cases. Romano et al. studied 49 patients with septic nonunions. They achieved an 85.1% success rate. Of equal importance is that "there were no side effects due to LIPUS, even in the presence of metallic implants and infection. Patients felt no discomfort during treatment."Union rates between 70-93%. The earlier treatment starts, the better the results. Clinical Application
Spatial average temporal intensity of 30mW/cm2 for 20 minutes per day (5-7 days/week) until fracture healing occurs.
References: Khan YK, Aurencin CT. Fracture Repair with Ultrasound: Clinical and Cell-Based Evaluation. J Bone Joint Surg Am. 2008;90:138-144. Griffin XL, Costello I, Costa ML. The Role of Low Intensity Pulsed Ultrasound Therapy in the Management of Acute Fractures: A Systematic Review. J Trauma. 2008;5:1446-1452. Romano CL, Romano D, Logoluso N. Low-Intensity Pulsed Ultrasound for the Treatment of Bone Delayed Union or Nonunion: A Review. Ultrasound in Med & Biol. 2009;35(4): 529-536. Cook Sd, Ryaby JP, McCabe J, Frey JJ, Heckman JD, Kristiansen TK. Acceleration of Tibial and Distal Radius Fracture Healing in Patients Who Smoke. Clin Ortho & Rel Res. 1997;337:198-207.
Fracture Repair with Low Intensity Pulsed Ultrasound
Treatment Parameters
