Stress fractures account for approximately 10% of all athletic injuries. Due to the high amount of impact force, 80-90% of all stress fractures occur in the lower extremities, most commonly seen in the running population. Knowing the high prevalence of stress fractures, it is important to also understand the diagnostic accuracy of the clinical tests one uses to rule-in or rule-less likely a stress fracture.
This research article, The Ability of Clinical Tests to Diagnose Stress Fractures: A systematic Review and Meta-analysis, assesses the reliability of both therapeutic ultrasound and the tuning fork test. The review discusses when, why, and how these tests should be implemented. As Schneiders et al, points out "clinically lower-limb stress fractures can be difficult to diagnose, due to a wide range of potential differential diagnoses." This differential diagnosis process should include (but not be limited to) compartment syndrome, muscular strain, tendinitis, tendinosis, infection, and nerve entrapment. Additionally, it is important to know the gold standard for ruling in stress fractures. Currently, a triple phase technium-99 bone scan (scintigraphy) is the most accurate method of diagnosing stress fractures with a sensitivity of 100% and specificity of 76%. MRI has also shown to be highly reliable, but due to its expensive cost, they are less frequently used. Additionally, the single photon-emission CT scan is receiving a lot of attention for it's accuracy in diagnosing stress fractures, but further research is needed.
As therapists (excluding the military), we do not have the power to order the gold standard tests mentioned above, so we must rely on our own diagnostic tests to help us interpret our patient's clinical presentation. Clinical tests that are currently used and accepted include therapeutic US, the tuning fork test, superficial palpation, and palpable thickening or swelling of periosteum. This review looked at therapeutic US and the tuning fork.
Unfortunately this systematic review concluded that neither test should be used as stand alone measures for diagnosing stress fractures. Therapeutic US pooled sensitivity (64%) and specificity (63%) revealed a low to moderate performance of the test. A meta-analysis was unable to be performed on the tuning fork test. However, one article by Lesho reported high sensitivity (75%) an moderate specificity (67%) when using the 128 Hz tuning fork. Limitations to this study include an inability to perform heterogenity on the articles and a limitation in the time frame of articles reviewed.
Scneiders A, et al. (2012). The ability of clinical tests to diagnose stress fractures: a systematic review and meta-analysis. JOSPT. 2012; 42.9: 760-771. Web. 1 May 2013.