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.