Clinical Use of Tuning Forks to Identify Running-Related Stress Fractures

Abstract

PURPOSE: To examine the diagnostic ability, sensitivity and specificity of tuning forks (of three different frequencies) on stress fractures in trained runners. METHODS: X-rays, bone scans and magnetic resonance images were collected on forty-five runners (31.2 ± 13.1 years) presenting with symptoms of stress fractures. Vibrating tuning forks of 3 frequencies (128, 256, 512 Hz) were placed on the tender bony sites and pain ( 0 = "no pain"; 1 = "mild pain"; 2 = "moderate pain"; 3 = "severe pain") was rated by each runner for each tuning fork. The relationship between pain ratings and positive radiographic imaging findings were examined. Sensitivity and specificity for detecting stress fractures were determined for each fork. RESULTS: The 256 Hz fork produced overall higher average pain scores (1.73 ± 0.96) than either the 128 Hz or 512 Hz forks (1.17 ± 1.05 and 0.82 ± 1.05; p=0.0001). The odds ratio of any positive pain score (rating of 1-3) to positive imaging evidence of stress fracture was 2.67 compared to a "0" pain score. A score of "3" (severe pain) from any fork was associated with a higher risk of imaging evidence of stress fracture compared to scores 0-2; the odds ratio of demonstrating imaging evidence of stress fractures was 5.91 with a pain rating of "3" compared to pain ratings of less than 3. CONCLUSIONS: Of all the tuning forks, stress fractures manifested more frequently with mild to severe pain ratings than no pain rating with the 256Hz fork. These results suggest that the tuning fork test should be used as an adjunct to clinical examination only and that a negative test should not supplant appropriate imaging for the diagnosis of stress fractures in runners. In the clinic, patients should be requested to quantify their perception of pain using the four-point scale (no pain increase, mild, moderate, severe). Any tuning fork-induced pain rating is associated with a positive imaging finding, but a reported pain value of 3 can be considered highly predictive for the presence of stress fracture. The tuning fork test may be most useful in those cases where imaging may not be readily available, such as in the field where a decision must be made regarding participation in running. Given its ability to produce a greater pain response, the authors propose that the 256 Hz tuning fork may be the most useful frequency to use in the clinical setting.