injuryupdate
25-08-2006, 03:52 PM
You may not need a $5000 machine to speed up your fracture repair. Conventional ultrasound may help. Full text at:
http://www.ptjournal.org/cgi/content/full/86/8/1118
Ultrasound Produced by a Conventional Therapeutic Ultrasound Unit Accelerates Fracture Repair
Stuart J Warden, Robyn K Fuchs, Chris K Kessler, Keith G Avin, Ryan E Cardinal and Rena L Stewart
SJ Warden, PT, PhD, is Assistant Professor, Department of Physical Therapy and Department of Anatomy and Cell Biology, Indiana University, 1140 W Michigan St, CF-326, Indianapolis, IN 46202 (USA).
RK Fuchs, PhD, is Assistant Research Professor, Department of Anatomy and Cell Biology, Indiana University
CK Kessler, BS, is Research Assistant, Department of Physical Therapy, Indiana University. He was completing his MD studies at the Indiana University School of Medicine at the time of this study
KG Avin, PT, DPT, is Research Assistant, Department of Physical Therapy, Indiana University. He was completing his DPT studies at the time of this study
RE Cardinal, PT, DPT, is Research Assistant, Department of Physical Therapy, Indiana University. He was completing his DPT studies at the time of this study
RL Stewart, MD, FRCS(C), is Director of Orthopaedic Trauma, Wishard Health Services, and Assistant Professor of Orthopaedic Surgery, Indiana University School of Medicine, Indianapolis, Ind
stwarden@iupui.edu. Address all correspondence to Dr Warden
Submitted November 16, 2005; Accepted February 15, 2006
Abstract
Background and Purpose. 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. Subjects and 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. Discussion and Conclusion. 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 SJ, Fuchs RK, Kessler CK, et al. Ultrasound produced by a conventional therapeutic ultrasound unit accelerates fracture repair. Phys Ther. 2006;86:11181127.]
Key Words: Animal Bone Fractures Models Musculoskeletal diseases Orthopedic equipment Orthopedic procedures Physical therapy techniques Skeleton Sports medicine
Introduction
Top
Abstract
Introduction
Method
Results
Discussion and Conclusions
References
Ultrasound is a form of acoustic energy (sound) that possesses a frequency above the limit detectable by the human ear. It has been used therapeutically for more than half a century and currently is one of the most widely and frequently used electrotherapeutic modalities applied by physical therapists.1 However, its full therapeutic potential is far from established, with new applications being added regularly to its repertoire.2 One recent novel application is in the treatment of bone fractures.3,4
Fracture repair involves a complex cascade of cellular events incorporating appropriate cellular recruitment, timed genetic expression, and the sequenced synthesis of numerous compounds. Although it is considered to be a naturally optimized process, recent evidence has demonstrated that fracture repair can be influenced by ultrasound to occur more rapidly without compromising the final tissue-level outcome.3,4 The application of ultrasound in animal fracture models accelerated the return to mechanical strength of intact bone by 30% to 38%.5 Similarly, in well-designed clinical trials, ultrasound accelerated the rate of fracture repair in the tibia, radius, and scaphoid by 30% to 38%.68 By pooling of the clinical trial data, a weighted average effect size was calculated to be 6.41 (95% confidence interval [CI]=0.0111.81); this value converts into a mean improvement in healing time of 64 days with ultrasound.9
The results of studies of the effect of ultrasound on fractured bone are interesting from the perspective that physical therapists traditionally have been instructed to avoid the application of ultrasonic energy to bone. When ultrasound is applied to bone, there is an inherent risk of tissue damage. Ultrasound has selective interfacial effects at the bone surface resulting from bone having a high absorption coefficient, a high relative acoustic impedance, and an ability to propagate shear waves.10 When doses at the high end of the therapeutic range are used, these effects can generate considerable tissue damage attributable to heating and inertial cavitation effects.11,12 To achieve clinically significant improvements during fracture repair, without the risk for tissue damage, the ultrasound dose has been changed substantially from that traditionally introduced in physical therapist clinical practice. Clinically, ultrasound is introduced at an intensity commonly in the range of 0.5 to 2.0 W/cm2.1 In comparison, in investigations into the therapeutic effect of ultrasound on bone, low-intensity pulsed ultrasound (LIPUS) has been used. Low-intensity pulsed ultrasound is pulsed-wave ultrasound with a spatially averaged, temporally averaged intensity of less than 0.1 W/cm2.13 With LIPUS, heat generation at the soft tissuebone interface has been shown both theoretically14 and experimentally5 to be insignificant (<1.0°C). Similarly, the risk for tissue-damaging inertial cavitation is negligible.14
Although LIPUS has been found to be effective in the management of bone fractures, to date the clinical utility of this finding in physical therapy is limited. Specialized ultrasound units (Exogen 2000+*) have been developed for the treatment of fractured bone. Although these units are highly efficacious,68 their cost is prohibitive because the units are leased on a patient-to-patient basis rather than purchased by individual clinics. Despite the benefits observed with LIPUS, the high cost of the specialized ultrasound units has led some authors10 to question whether conventional therapeutic ultrasound units could be used by physical therapists to accelerate fracture repair. At the lower-intensity settings on these units, it is possible to produce a dose comparable to that shown to be effective during fracture repair with the specialized units.
The aim of this study was to investigate the effect of LIPUS produced by a conventional therapeutic ultrasound unit on fracture repair in an animal model. We hypothesized that LIPUS would facilitate fracture repair, as evidenced by more bone mineral at the fracture site and a stronger fracture callus at selected time points during healing.
http://www.ptjournal.org/cgi/content/full/86/8/1118
Ultrasound Produced by a Conventional Therapeutic Ultrasound Unit Accelerates Fracture Repair
Stuart J Warden, Robyn K Fuchs, Chris K Kessler, Keith G Avin, Ryan E Cardinal and Rena L Stewart
SJ Warden, PT, PhD, is Assistant Professor, Department of Physical Therapy and Department of Anatomy and Cell Biology, Indiana University, 1140 W Michigan St, CF-326, Indianapolis, IN 46202 (USA).
RK Fuchs, PhD, is Assistant Research Professor, Department of Anatomy and Cell Biology, Indiana University
CK Kessler, BS, is Research Assistant, Department of Physical Therapy, Indiana University. He was completing his MD studies at the Indiana University School of Medicine at the time of this study
KG Avin, PT, DPT, is Research Assistant, Department of Physical Therapy, Indiana University. He was completing his DPT studies at the time of this study
RE Cardinal, PT, DPT, is Research Assistant, Department of Physical Therapy, Indiana University. He was completing his DPT studies at the time of this study
RL Stewart, MD, FRCS(C), is Director of Orthopaedic Trauma, Wishard Health Services, and Assistant Professor of Orthopaedic Surgery, Indiana University School of Medicine, Indianapolis, Ind
stwarden@iupui.edu. Address all correspondence to Dr Warden
Submitted November 16, 2005; Accepted February 15, 2006
Abstract
Background and Purpose. 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. Subjects and 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. Discussion and Conclusion. 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 SJ, Fuchs RK, Kessler CK, et al. Ultrasound produced by a conventional therapeutic ultrasound unit accelerates fracture repair. Phys Ther. 2006;86:11181127.]
Key Words: Animal Bone Fractures Models Musculoskeletal diseases Orthopedic equipment Orthopedic procedures Physical therapy techniques Skeleton Sports medicine
Introduction
Top
Abstract
Introduction
Method
Results
Discussion and Conclusions
References
Ultrasound is a form of acoustic energy (sound) that possesses a frequency above the limit detectable by the human ear. It has been used therapeutically for more than half a century and currently is one of the most widely and frequently used electrotherapeutic modalities applied by physical therapists.1 However, its full therapeutic potential is far from established, with new applications being added regularly to its repertoire.2 One recent novel application is in the treatment of bone fractures.3,4
Fracture repair involves a complex cascade of cellular events incorporating appropriate cellular recruitment, timed genetic expression, and the sequenced synthesis of numerous compounds. Although it is considered to be a naturally optimized process, recent evidence has demonstrated that fracture repair can be influenced by ultrasound to occur more rapidly without compromising the final tissue-level outcome.3,4 The application of ultrasound in animal fracture models accelerated the return to mechanical strength of intact bone by 30% to 38%.5 Similarly, in well-designed clinical trials, ultrasound accelerated the rate of fracture repair in the tibia, radius, and scaphoid by 30% to 38%.68 By pooling of the clinical trial data, a weighted average effect size was calculated to be 6.41 (95% confidence interval [CI]=0.0111.81); this value converts into a mean improvement in healing time of 64 days with ultrasound.9
The results of studies of the effect of ultrasound on fractured bone are interesting from the perspective that physical therapists traditionally have been instructed to avoid the application of ultrasonic energy to bone. When ultrasound is applied to bone, there is an inherent risk of tissue damage. Ultrasound has selective interfacial effects at the bone surface resulting from bone having a high absorption coefficient, a high relative acoustic impedance, and an ability to propagate shear waves.10 When doses at the high end of the therapeutic range are used, these effects can generate considerable tissue damage attributable to heating and inertial cavitation effects.11,12 To achieve clinically significant improvements during fracture repair, without the risk for tissue damage, the ultrasound dose has been changed substantially from that traditionally introduced in physical therapist clinical practice. Clinically, ultrasound is introduced at an intensity commonly in the range of 0.5 to 2.0 W/cm2.1 In comparison, in investigations into the therapeutic effect of ultrasound on bone, low-intensity pulsed ultrasound (LIPUS) has been used. Low-intensity pulsed ultrasound is pulsed-wave ultrasound with a spatially averaged, temporally averaged intensity of less than 0.1 W/cm2.13 With LIPUS, heat generation at the soft tissuebone interface has been shown both theoretically14 and experimentally5 to be insignificant (<1.0°C). Similarly, the risk for tissue-damaging inertial cavitation is negligible.14
Although LIPUS has been found to be effective in the management of bone fractures, to date the clinical utility of this finding in physical therapy is limited. Specialized ultrasound units (Exogen 2000+*) have been developed for the treatment of fractured bone. Although these units are highly efficacious,68 their cost is prohibitive because the units are leased on a patient-to-patient basis rather than purchased by individual clinics. Despite the benefits observed with LIPUS, the high cost of the specialized ultrasound units has led some authors10 to question whether conventional therapeutic ultrasound units could be used by physical therapists to accelerate fracture repair. At the lower-intensity settings on these units, it is possible to produce a dose comparable to that shown to be effective during fracture repair with the specialized units.
The aim of this study was to investigate the effect of LIPUS produced by a conventional therapeutic ultrasound unit on fracture repair in an animal model. We hypothesized that LIPUS would facilitate fracture repair, as evidenced by more bone mineral at the fracture site and a stronger fracture callus at selected time points during healing.