title: Estimation of return-to-sports-time for athletes with stress fracture - an approach combining risk level of fracture site with severity based on imaging.
abstract: BACKGROUND
  The aim was to compare the return-to-sports-time (RTST) following stress fractures on the basis of site and severity of injury. This retrospective study was set up at a single institution. Diagnosis was confirmed by an interdisciplinary adjudication panel and images were rated in a blinded-read setting.
  
  
  METHODS
  52 athletes (female, n = 30; male, n = 22; mean age, 22.8 years) with stress fracture (SFX) who had undergone at least one examination, either MRI or bone scintigraphy, were included. Magnetic resonance images (MRI) and/or bone scintigraphy (BS) of SFX were classified as either low- or high-grade SFX, according to existing grading systems. For MRI, high-grade SFX was defined as visibility of a fracture line or bone marrow edema in T1-, T2-weighted and short tau inversion recovery (STIR) sequences, with low-grade SFX showing no fracture line and bone marrow edema only in STIR and/or T2-weighted sequences. In BS images, a mild and poorly defined focal tracer uptake represented a low-grade lesion, whereas an intense and sharply marginated uptake marked a high-grade SFX. In addition, all injuries were categorized by location as high- or low-risk stress fractures. RTST was obtained from the clinical records. All patients were treated according to a non-weight-bearing treatment plan and comprehensive follow-up data was complete until full recovery. Two-sided Wilcoxon's rank sum test was used for group comparisons.
  
  
  RESULTS
  High-risk SFX had a mean RTST of 132 days (d) [IQR 64d - 132d] compared to 119d [IQR 50d - 110d] for low-risk sites (p = 0.19). RTST was significantly longer (p = 0.01) in high-grade lesions [mean, 143d; IQR 66d - 134d] than in low-grade [mean, 95d; IQR 42d - 94d]. Analysis of high-risk SFX showed no difference in RTST (p = 0.45) between high- and low-grade [mean, 131d; IQR 72d - 123d vs. mean, 135d; IQR 63d - 132d]. In contrast, the difference was significant for low-risk SFX (p = 0.005) [low-grade; mean, 61d; IQR 35d - 78d vs. high-grade; mean, 153d; IQR 64d - 164d].
  
  
  CONCLUSIONS
  For SFX at low-risk sites, the significant difference in RTST between low- and high-grade lesions allows more accurate estimation of RTST by this approach. Both location of the injury and severity determined by imaging should therefore be considered for prediction of RTST.
authors.affiliation: Klinik für Radiologie und Nuklearmedizin, Universitätsklinikum Magdeburg A.ö.R. Otto-von-Guericke Universität, Leipziger Straße 44, Magdeburg 39120, Germany. o.dobrindt@gmail.com
authors.forename: Oliver
authors.initials: O
authors.lastname: Dobrindt
authors.forename: Birgit
authors.initials: B
authors.lastname: Hoffmeyer
authors.forename: Juri
authors.initials: J
authors.lastname: Ruf
authors.forename: Max
authors.initials: M
authors.lastname: Seidensticker
authors.forename: Ingo G
authors.initials: IG
authors.lastname: Steffen
authors.forename: Frank
authors.initials: F
authors.lastname: Fischbach
authors.forename: Alina
authors.initials: A
authors.lastname: Zarva
authors.forename: Gero
authors.initials: G
authors.lastname: Wieners
authors.forename: Gerhard
authors.initials: G
authors.lastname: Ulrich
authors.forename: Christoph H
authors.initials: CH
authors.lastname: Lohmann
authors.forename: Holger
authors.initials: H
authors.lastname: Amthauer
mesh_terms: D000293:Adolescent; D000328:Adult; D001265:Athletic Injuries / Q000175:diagnosis* / Q000503:physiopathology / Q000628:therapy; D003952:Diagnostic Imaging / Q000379:methods; D005260:Female; D015775:Fractures, Stress / Q000175:diagnosis* / Q000503:physiopathology / Q000628:therapy; D005858:Germany; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D011237:Predictive Value of Tests; D011877:Radionuclide Imaging; D020127:Recovery of Function; D012189:Retrospective Studies; D018570:Risk Assessment; D012307:Risk Factors; D012720:Severity of Illness Index; D013997:Time Factors; D016896:Treatment Outcome; D016474:Weight-Bearing; D055815:Young Adult