title: Tibial stress changes in new combat recruits for special forces: patterns and timing at MR imaging.
abstract: OBJECTIVE
  To characterize the incidence, location, grade, and patterns of magnetic resonance (MR) imaging findings in the tibia in asymptomatic recruits before and after 4-month basic training and to investigate whether MR imaging parameters correlated with pretraining activity levels or with future symptomatic injury.
  
  
  METHODS
  This study was approved by three institutional review boards and was conducted in compliance with HIPAA requirements. Volunteers were included in the study after they signed informed consent forms. MR imaging of the tibia of 55 men entering the Israeli Special Forces was performed on recruitment day and after basic training. Ten recruits who did not perform vigorous self-training prior to and during service served as control subjects. MR imaging studies in all recruits were evaluated for presence, type, length, and location of bone stress changes in the tibia. Anthropometric measurements and activity history data were collected. Relationships between bone stress changes, physical activity, and clinical findings and between lesion size and progression were analyzed.
  
  
  RESULTS
  Bone stress changes were seen in 35 of 55 recruits (in 26 recruits at time 0 and in nine recruits after basic training). Most bone stress changes consisted of endosteal marrow edema. Approximately 50% of bone stress changes occurred between the middle and distal thirds of the tibia. Lesion size at time 0 had significant correlation with progression. All endosteal findings smaller than 100 mm resolved or did not change, while most findings larger than 100 mm progressed. Of 10 control subjects, one had bone stress changes at time 0, and one had bone stress changes at 4 months.
  
  
  CONCLUSIONS
  Most tibial bone stress changes occurred before basic training, were usually endosteal, occurred between the middle and distal thirds of the tibia, were smaller than 100 mm, and did not progress. These findings are presumed to represent normal bone remodeling.
authors.affiliation: From the Heller Institute of Medical Research, Sheba Medical Center, Ramat Gan, Israel (A.H., D.S.M., Y.F.); Department of Biomedical Engineering, Tel Aviv University, Tel Aviv, Israel (A.H.); Department of Physiotherapy, Ariel University, Ariel, Israel (D.S.M.); Military Performance Division, U.S. Army Research Institute of Environmental Medicine, Natick, Mass (R.K.E.); Department of Radiology, State University of New York at Stony Brook, Stony Brook, NY (M.E.S.); Department of Imaging, Assaf Harofeh University Medical Center, Israel, Zerifin, Israel (N.S.); and Department of Radiology, Hospital of the University of Pennsylvania, Philadelphia, Pa (N.S.).
authors.forename: Amir
authors.initials: A
authors.lastname: Hadid
authors.forename: Daniel S
authors.initials: DS
authors.lastname: Moran
authors.forename: Rachel K
authors.initials: RK
authors.lastname: Evans
authors.forename: Yael
authors.initials: Y
authors.lastname: Fuks
authors.forename: Mark E
authors.initials: ME
authors.lastname: Schweitzer
authors.forename: Nogah
authors.initials: N
authors.lastname: Shabshin
mesh_terms: D000293:Adolescent; D000886:Anthropometry; D015775:Fractures, Stress / Q000503:physiopathology; D006801:Humans; D007557:Israel; D008279:Magnetic Resonance Imaging; D008297:Male; D008889:Military Personnel; D012307:Risk Factors; D013314:Stress, Mechanical; D011795:Surveys and Questionnaires; D013977:Tibia / Q000293:injuries / Q000502:physiology*; D013978:Tibial Fractures / Q000503:physiopathology; D055815:Young Adult