The use of ultrasound therapy is widespread in sports physiotherapy and physical therapy practice (Khanna et al., 2009). In most cases it is used as an adjunctive therapy to other forms of treatment and rehabilitation. This, unfortunately, is in the absence of well-designed clinical trials demonstrating any significant improvement in human function. Now, this site does not really discuss the various forms of electrophysical agents and their potential role in the management of athletes, however, I would love to open a can of worms. This article will discuss recent research on low intensity pulsed ultrasound for the management of soft-tissue injuries.
Low Intensity Pulsed Ultrasound For Soft Tissue Injuries
A study published in the British Medical Bulletin by Khanna and colleagues (2009) evaluated the evidence for use of low intenstiy pulsed ultrasound (LIPUS) in soft tissue injuries. This article included studies with both animal and human participants and also in vivo and in vitro conditions. In summary, the review found the following results.
Intervertebral Disc. Ultrasound therapy had the following effects on nucleus pulposus material:
- Increased IVD cell proliferation and matrix synthesis
- Increased proteoglycan synthesis; which increased water uptake and may regress herniation
- Induced macrohpage migration; which may increase remodelling
- Increased collagen synthesis (16-19%) (Miyamoto et al., 2005)
Ligament. Ultrasound therapy was shown to have:
- Accelerated ligament healing
- Accelerated rat medial collateral ligament injury healing (Takakura et al. 2002; Sparrow et al., 2005).
Cartilage. Ultrasound therapy was shown to have the following effects on cartilage defects:
- Significantly improved full-thickness osteochondral defects with reference to both morphologic features and histologic characteristics of repaired cartilage.
- Enhanced the healing of cartilage defects in vivo.
- Cartilage healing assisted with LIPUS produces fewer degenerative changes in the long term, as compared with controls. (Cook et al., 2001).
Tendon. The 2009 review found that therapeutic ultrasound has been found to have no effect over and above placebo on tendon healing (Khanna et al., 2009). However, this may be contradicted by some brand new research discussed below.
New Research on Tendon Healing and Ultrasound Therapy
Junior et al. (2011) randomised 28 rats with surgically induced calcaneal tendon injuries into 2 groups, a control and a LIPUS groups. The experimental group underwent 28 consecutive days of low intensity pulsed ultrasound therapy, starting on the first postoperative day. The parameters and dosage where as follows:
- 2 W of irradiation intensity applied to an effective radiation area (ERA) head of 3.8 cm2
- 16-Hz frequency
- Pulsed 20% sonication periods
- Time: 5 minutes
- SATA = 0.1 W/cm2
- SAI = 0.52 W/cm2
- Subaquatic delivery technique
Following the experiment period the results were analysed. To account for differences in animals the results were normalised to the uninvolved limb, and therefore, each animal served as their own control. The study examined outcomes variables of cross-sectional area (CSA), ultimate load (UL), tensile strength (TS), and energy absorption (EA). The results are demonstrated graphically below, and are given as the mean percentage greater than the uninvolved side:
Thus, you can see the the experimental LIPUS groups consistently performed better on all outcomes, and therefore the LIPUS has improved the biomechanical properties of the tendon.
So does that mean we should utilise ultrasound therapy for all our tendon pathologies?
My Beef With Ultrasound Therapy
There a quite a few limitations in the ultrasound literature, particularly as it applies to general clinical practice. Whilst there are the obvious issues of in vitro and animal studies, that is the requirement for validation in vivo in human subjects. It is also necessay to question do these changes at a molecular and biochemical level translate to clinically relevant improvements in function? Additionally, there are the mechanisms of “induced” injuries which frequently do not mirror the mechanism of injury seen in our sports physiotherapy clinics (Junior et al., 2011).
I also see the prescribed dosages as an issue. These studies frequently utilise daily applications of the ultrasound therapy. Whilst this is clearly achievable in the realm of elite sports physiotherapy, this is generally not an option for the general sporting population and widespread physiotherapy/physical therapy practice. This is echoed in the review by Khanna (2009) who suggests the literature is deficient on the economical benefits of LIPUS on soft-tissue healing.
Furthermore there is a clear issue of time here. If you have a 15-30 minutes consultation with your athlete (the norm for many private practices), would you elect to up to a third of their time with you on ultrasound therapy? Do you have better tools in your sports physiotherapy toolbox that you could aim at this athlete? Whilst this is very clearly a decision for you to make, based on the evidence provided in the literature as well as an individual case basis, I feel the question is worth asking.
What Are Your Thoughts?
I would love to know what your thoughts are on the use of ultrasound therapy. Please leave a comment below and answer any of my rhetorical, implied or simply unasked questions. Alternatively, let us know of your victories and losses, trials and tribulations all as they apply to ultrasound therapy.
Cook SD, Salkeld SL, Popich-Patron LS, Ryaby JP, Jones DG, Barrack RL (2001) Improved cartilage repair after treatment with low-intensity pulsed ultrasound. Clin Orthop, 391, 231 – 243
Junior SLJ, Camanho GL, Bassit ACF, Forgas A, Ingham SJM, Abdall RJ. Low-intensity pulsed ultrasound accelerates healing in rat calcaneus tendon injuries. J Orthop Sports Phys Ther 2011;41(7):526-531
Khanna A, Nelmes RT, Gougoulias N, Maffulli N, Gray J. The effects of LIPUS on soft-tissue healing: a review of literature. Br Med Bull. 2009;89:169-182.
Miyamoto K, An HS, Sah RL et al. (2005) Exposure to pulsed low intensity ultrasound stimulates extracellular matrix metabolism of bovine intervertebral disc cells cultured in alginate beads. Spine, 30, 2398–2405.
Sparrow KJ, Finucane SD, Owen JR, Wayne JS. (2005) The effects of low-intensity ultrasound on medial collateral ligament healing in the rabbit model. Am J Sports Med, 33, 1048–1056.
Takakura Y, Matsui N, Yoshiya S et al. (2002) Low-intensity pulsed ultrasound enhances early healing of medial collateral ligament injuries in rats. J Ultrasound Med, 21, 283–288.