Schneiders AG, Sullivan SJ, Hendrick PA, et al. The ability of clinical tests to diagnose stress fractures: a systematic review and meta-analysis. J Orthop Sports Phys Ther. 2012;42:760–771.
Clinical Question: Stress fractures can be difficult to diagnose due to differential diagnoses and imaging technologies that lack the ability to accurately detect bony changes in the early phases of injury. Proper management is dependent on early diagnosis. Scintigraphy and magnetic resonance imaging (MRI) have been established as the gold standards for diagnosing stress fractures. It has been suggested that tuning forks and therapeutic ultrasound are diagnostically accurate in identifying stress fractures. What is the accuracy of clinical tests when compared to imaging when diagnosing lower limb stress fractures?
Data Sources: Studies were identified by searching the following databases: AMED, CINAHL, Embase, MEDLINE, PEDro, PUBMED, Scopus, and SPORTDiscus. All studies published between January 1950 and June 2011 were considered for review. Key terms searched included stress fracture, fatigue fracture, insufficiency fracture, march fracture, diagnose, investigate, identify, analysis, physical exam, interpret, palpate, pressure, and ultrasound.
Study Selection: The systematic review included articles that (1) reported one or more index tests, (2) used at least one radiological reference test, (3) reported or allowed computation of diagnostic values, (4) did not impose an age restriction for participants, and (5) included only lower limb stress fracture.
Data Extraction: Two researchers searched the databases independently to retrieve and evaluate articles based on the inclusion criteria specified above. A third reviewer was used at a consensus meeting to resolve any disputes. The quality of articles was assessed using the Quality Assessment of Diagnostic Accuracy Studies (QUADAS) scale. The initial literature search included 9,321 articles. After examination for context, key words, and removal of duplicate titles, 529 abstracts had been screened. Nine full-text articles met the inclusion criteria and were examined using the QUADAS scale, which helped determine the quality of a study based on biases present in the study but was not used as an exclusionary criterion. Of the 9 articles included, 7 investigated the ability of therapeutic ultrasound, and 2 investigated the ability of tuning forks to diagnose lower limb stress fractures.
Main Results: The studies included in this review reported primarily male participants between the ages of 19 and 31 years. Magnetic resonance imaging, roentgenogram, and bone scintigraphy were the reference standards. Synthesis of data from therapeutic ultrasound articles showed a sensitivity of 64%, specificity of 63%, positive likelihood ratio of 2.1, and negative likelihood ratio of 0.3 with a 95% confidence interval. Because only two studies examined tuning forks, diagnostic data were not pooled. Tuning fork data ranged from 35% to 92%, 19% to 83%, 0.6 to 3.0, and 0.4 to 1.6 for sensitivity, specificity, positive likelihood ratio, and negative likelihood ratio, respectively.
Conclusions: Based on the available literature, it is recommended that radiological imaging be the standard of diagnosing lower limb stress fractures. Using therapeutic ultrasound and tuning forks as tools to diagnose lower limb stress fractures is not adequately supported by the current literature.
Summary: Stress fractures comprise roughly 10% of all athletic injuries, with 80% to 95% occurring in the lower limb, primarily the tibia.1,2 Due to similar symptoms as other injuries caused by overuse, stress fractures can be difficult to diagnose, so early detection is the key to proper management and treatment.1–3
Radiological imaging (ie, scintigraphy and MRI) has been deemed the gold standard for recognizing stress fractures, with MRI having the highest specificity; however, stress fractures can still be difficult to diagnose even with imaging.1,2 These tools can often be expensive to use and inaccessible to certain patient populations.
Other clinical tools that have been proposed for the diagnosis of stress fractures include tuning forks and therapeutic ultrasound. It is proposed that tuning forks can diagnose stress fractures based on the theory that the tool causes vibrations that irritate the damaged periosteum. Similarly, it has been suggested that therapeutic ultrasound causes discomfort when a stress fracture is present due to increased osteoclast reabsorption.1
Although pooled sensitivity and specificity of therapeutic ultrasound were measured at 64% and 63%, respectively, positive and negative likelihood ratios measured at 2.09 and 0.35, respectively, were small.1 Therefore, it appears that the results of the pooled data were not precise enough to draw any conclusions surrounding using therapeutic ultrasound to diagnose stress fractures in the lower limb.1 Four of the studies that reported higher positive likelihood ratios scored lower on the QUADAS. This was primarily due to not clearly specifying the selection criteria for inclusion of participants and reporting clinical data on each participant that was not clearly defined.1 Comparatively, the three remaining studies that scored higher on the QUADAS scale had small positive likelihood ratios.1 From the findings of the QUADAS scale, the authors concluded that interpretation of the results of these studies should be done with caution due to potential bias and validity compromises.1
Tuning fork data were not pooled for meta-analysis because only two studies met the inclusion criteria. Consequently, results were discussed between studies individually.1 One study had a high score on the QUADAS scale, illustrated tuning fork specificity to be moderate (67%) and sensitivity to be moderate to high (75%), and had a positive likelihood ratio of 2.3 for a 128-Hz tuning fork.1 The second study scored poorly on the QUADAS scale (12 of 26) due to unclear reporting of results. This study examined the diagnostic accuracy of 128-, 256-, and 512-Hz tuning forks.1 These tuning forks were compared to three other reference tests (MRI, roentgenograms, and bone scintigraphy), with MRI and bone scintigraphy noted as gold standard measurements.1 The 256-Hz tuning fork showed the highest sensitivity (92%, 90%, and 77.7%, respectively); however, specificity values were low, which pointed toward difficulty identifying stress fracture in the event of a positive test result.1 The other two frequencies of tuning forks' diagnostic statistics pointed toward an inability to diagnose stress fractures without radiological imaging.1 Neither study reported the confidence intervals for specificity or sensitivity or indicated poor likelihood ratios.
Although tuning forks have not been indicated as a strong tool to diagnose stress fractures (specificity: 19% to 83%),4 they may have a role in clinical evaluation due to their low cost, non-invasive nature, and relative sensitivity (75% to 100%). MRI is considered the gold standard in diagnosing lower limb stress fractures, but it is not without a possible financial burden for patients in terms of cost and the accessibility of the imaging. Due to the high sensitivity of tuning forks (sensitivity: 75% to 100%), they can provide useful information in the clinical assessment of lower limb stress fractures. However, this should not be the only information that clinicians rely on when making referrals for further imaging studies.
Athletic trainers should be cautious when using either diagnostic tool (ultrasound or tuning fork) to diagnose a stress fracture. In addition to clinical testing and diagnostic imaging, clinicians should use other tools from their subjective and objective evaluation to help determine the possibility of a stress fracture through a thorough history, including recent increases in training volume, signs and symptoms, insidious onset, sharp specific pain, and edema at the pain site.2 Additional risk factors are large quantities of physical activity with limited rest, rapid increases in physical activity, patients who participate in running sports, and patients who are over-weight and underweight.2 Ultimately, clinicians must rely on imaging tools (eg, MRI) to diagnose lower limb stress fractures, and should use subjective and objective findings to aid in the clinical decision-making process and making referrals for imaging studies.5
- Schneiders AG, Sullivan SJ, Hendrick PA, et al. The ability of clinical tests to diagnose stress fractures: a systematic review and meta-analysis. J Orthop Sports Phys Ther. 2012;42:760–771. doi:10.2519/jospt.2012.4000 [CrossRef]
- Patel DS, Roth M, Kapil N. Stress fractures: diagnosis, treatment, and prevention. Am Fam Physician. 2011;83:39–46.
- McKenna MJ, Hefferman E, Hurson C, McKierrnan FE. Clinician approach to diagnosis of stress fractures including bisphosphonate-associated fractures. QJM. 2013;107:99–105. doi:10.1093/qjmed/hct192 [CrossRef]
- Mugunthan K, Doust J, Kurz B, Glasziou P. Is there sufficient evidence for tuning fork tests in diagnosing fractures? A systematic review. BMJ Open. 2014;4:e005238. doi:10.1136/bmjopen-2014-005238 [CrossRef]
- Wright AA, Hegedus EJ, Lenchik L, Kuhn KJ, Santiago L, Smoliga JM. Diagnostic accuracy of various imaging modalities for suspected lower extremity stress fractures: a systematic review with evidence-based recommendations for clinical practice. Am J Sports Med. 2016;44:255–263. doi:10.1177/0363546515574066 [CrossRef]