Blinded-read of bone scintigraphy: the impact on diagnosis and healing time for stress injuries with emphasis on the foot.

AIM

This study evaluated the use of bone scintigraphy (BS) for the diagnosis of stress fractures in athletes and its validity for the prediction of healing time, with a focus on foot injuries.

METHODS

In our retrospective study, 84 athletes with a total of 93 suspected stress fractures (foot, n = 66; others, n = 27) were included. A blinded-read of BS was performed by 3 observers. The standard of reference was established by an interdisciplinary truth-panel using all imaging data (scintigraphic, radiographic, and magnetic resonance imaging) and follow-up data (>12 month). Sensitivity, specificity, positive predictive value, negative predictive value, and accuracy for diagnosing stress fractures were calculated. Stress injuries were rated according to a 5-point grading score (0-4) and associated to the healing time.

RESULTS

For the diagnosis of stress injuries (n = 50/93), mean sensitivity, specificity, positive predictive value, negative predictive value, and accuracy were 97.3%, 67.4%, 77.7%, 95.6%, and 83.5%, respectively. Interobserver analysis showed a high agreement between all 3 readers (mean κ = 0.83). In univariate analysis healing time of grade 3 to 4 stress injuries was significantly higher (median, 87 days; interquartile range, 69-132 days) compared with grade 1 to 2 lesions (median, 63 days; interquartile range, 43-95 days; P = 0.0067). Moreover, healing time of scintigraphic high grade stress injuries was significantly longer in a general linear model with adjustment for cofactors (grade, 3-4 vs. 1-2; P = 0.033).

CONCLUSIONS

BS is a sensitive and reliable method for the diagnosis of stress injuries. In addition, the simplified classification for mild and severe stress injuries allows an estimation of healing time.