Sports Medicine Research: In the Lab & In the Field: Ultrasound as an Evaluation Tool of Bone Stress Injuries (Sports Med Res)
Monday, April 16, 2012

Ultrasound as an Evaluation Tool of Bone Stress Injuries

Ultrasound as a primary evaluation tool of bone stress injuries in elite track and field athletes

Papalada A., Maliaropoulos N., Tsitas K., Kiritsi O., Padhiar N., Del Buono A., Maffulli N. American Journal of Sports Medicine, 2012; 40: 915-919

Overuse injuries, specifically bone stress injuries are a problem in elite track and field athletes and often go misdiagnosed or not diagnosed at all. Though magnetic resonance imaging (MRI) is the gold standard method to diagnose a bone stress injury, it is costly. Therapeutic ultrasound (TUS) may be a cost-effective and noninvasive tool for preliminary diagnosis of stress fractures. Therefore, the purpose of this study was to determine if TUS is an accurate method for early diagnosis of bone stress injuries compared to MRI. This was a ten-year study that assessed 113 (53 males and 60 women) elite track and field athletes, who were suspected of a bone stress injury. These patients had less than 1 month of unilateral exercise induced pain that alleviated with rest, and had no history of lower leg trauma. Athletes with suspected muscle strain, compartment syndrome, or low back pain were excluded. Bilateral examinations were performed by an experienced physical therapist using a TUS device. TUS (5 cm2 probe, 1 MHz) was conducted at the site of pain with continuous ultrasound at highest intensity (2 W/cm2) and the most symptomatic point was spotted for 30 seconds (probe was moved at 1 cm/s). Patients were separated into 2 groups: 1) pain with TUS intensity and 2) no pain with TUS intensity. MRI scans were also used for suspected bone stress injuries. The authors scored the MRIs using a 5-stage grading scale to classify bone stress injuries (e.g., 0 = normal appearance, 3 = stress fractures with discrete fracture line visible). An independent radiologist blinded to athletes’ clinical features and TUS exam analyzed the imaging reports randomly. The distal tibia followed by the metatarsals were the most common sites of injuries [n = 42 (51%), n = 25 (21%), respectively], the least common site of injury was the femoral neck [n = 1 (1%)]. The MRI results showed that 2.7% had a 0 grade injury, 10.6% had a grade of 1 injury, 13.3% had a grade 2 injury, 68.2% had a grade 3 injury, and 5.3% had a grade 4 injury. Compared to MRI, TUS showed 95% sensitivity (sensitivity: positively diagnose a patient who has pathology) for high-grade injuries (i.e., MRI bone stress injury scale of 3 or 4), and 44% sensitivity for low-grade bone stress injuries (i.e., MRI bone stress injury scale of 1 or 2). The TUS was shown to have 66.6% specificity (specificity: not falsely diagnosing a healthy patient) and 99% positive predictive value (precision rate or proportion that a positive test correctly diagnosis a patient), 13.4% negative predictive value (proportion of subjects that a negative test result correctly diagnosis a patient), and 81.4% accuracy compared to the MRI as the gold standard.

The gold standard for diagnosing possible bone stress injuries is the MRI; however, this can be very costly. TUS is more cost efficient and more readily available than the MRI. The TUS was shown to be sensitive for the diagnosis of bone stress injuries compared to MRI; particularly more severe bone stress injuries. Therefore, TUS could be useful in the assessment of bone stress injuries. Physical therapists as well as athletic trainers can perform TUS if the clinician suspects the presence of a stress fracture, which could help early diagnosis of bone fractures. Earlier detection of stress fractures could lead to earlier return to sport activity. Since most of the injuries (~75%) were a grade 3 or 4 this could have led to an increase in the sensitivity of TUS since it is easier to identify the more serious injuries. It is important to note that TUS missed many low-grade MRI-detected stress injuries so it is important for clinicians to carefully monitor patients with possible low grade stress injuries and negative TUS findings. Further research with TUS will be needed to determine the reproducibility (reliability), as well as methodology to increase sensitivity. TUS may be used as the first tool in the evaluation of suspected overuse bone injury but with caution since TUS has a low ability to pick up less severe bone injuries. Do you have a TUS in your athletic training room and feel confident that you could use it as a tool for the diagnosis of early bone stress injury?

Written by: Jane McDevitt MS, ATC, CSCS
Reviewed by: Jeffrey Driban

Recommended Reading:


Papalada A, Malliaropoulos N, Tsitas K, Kiritsi O, Padhiar N, Del Buono A, & Maffulli N (2012). Ultrasound as a primary evaluation tool of bone stress injuries in elite track and field athletes. The American Journal of Sports Medicine, 40 (4), 915-9 PMID: 22366519

5 comments:

Jeffrey Driban said...

FYI - A letter to the editor was recently published regarding this article and questions some of the methods and interpretation of the results: http://ajs.sagepub.com/content/40/9/NP25.full

Alyson said...

I recently have had a case of a tibial bone stress reaction in a collegiate cheerleader. That is why this article interested me. A recent graduate from a US favoring undergraduate institution, I have been taught that one method of assessing a possible bone stress injury is US. So, yes I am familiar with this technique and find it a very useful tool in the treatment/rehab toolbox. But, I am not so sure to use it as the end-all-be-all. It can be used in conjunctions of x-ray and other testing methods, allowing for the more expensive MR to be a last resort. With the US, a great hx and a good clinical exam, as well as x-rays, you can become fairly competent that you know what you are looking for and if it is there or not. I have used US with the gel base, and also US in the water to help assess bone stress reaction, both of which have helped in my decision making. The theoretical concept makes sense, sound waves bouncing off of an unstable service (bone break or reaction) can cause an unusual increase in pain, and could be suggestive of a possible bone reaction present. US, among it many other uses, can be a definite help with deciding between treatments for your stress reactions.

My athlete currently was way to far along with her stress reaction, and MR was the only way we were going to go with our plan. If we had had a different perspective, and the clinical exam didn't show flashing lights pointing towards a stress reaction, I would be safe to say, I may have used TUS as a dx tool for the help of finding what was wrong.

Tanks for this article, it was very interesting.

Meghan Melinchak said...

Great summary. I'm interested in ultrasound settings themselves? Couldn't you theoretically produce pain anywhere with the right settings?

I've personally never had success using US as a diagnostic tool for stress fractures, but I by no mean's assume that that means its unsuccessful.

Great job!

-Meghan

Jane McDevitt said...

Meghan-

They used continuous ultrasound at highest intensity (2 W/cm2) and the most symptomatic point was spotted for 30 seconds (probe was moved at 1 cm/s). I believe you could produced pain anywhere with the right settings.

FYI - A letter to the editor was recently published regarding this article and questions some of the methods and interpretation of the results: http://ajs.sagepub.com/content/40/9/NP25.full

Brandon Green said...

I have seen multiple studies that support that US can be used to diagnose stress fractures; more specifically, in the tibia for a differential diagnosis of MTSS. Continuous US yields better results, while treatments are fairly short to focus primarily on the acoustic sound waves penetrating the suspected area of the stress fracture rather than thermal effects.

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