title: Temperature influence on DXA measurements: bone mineral density acquisition in frozen and thawed human femora.
abstract: BACKGROUND
  Determining bone mineral density (BMD) with dual-energy x-ray absorptiometry (DXA) is an established and widely used method that is also applied prior to biomechanical testing. However, DXA is affected by a number of factors. In order to delay decompositional processes, human specimens for biomechanical studies are usually stored at about -20 degrees C; similarly, bone mineral density measurements are usually performed in the frozen state. The aim of our study was to investigate the influence of bone temperature on the measured bone mineral density.
  
  
  METHODS
  Using DXA, bone mineral density measurements were taken in 19 fresh-frozen human femora, in the frozen and the thawed state. Water was used to mimic the missing soft tissue around the specimens. Measurements were taken with the specimens in standardized internal rotation. Total-BMD and single-BMD values of different regions of interest were used for evaluation.
  
  
  RESULTS
  Fourteen of the 19 specimens showed a decrease in BMD after thawing. The measured total-BMD of the frozen specimens was significantly (1.4%) higher than the measured BMD of the thawed specimens.
  
  
  CONCLUSIONS
  Based on our findings we recommend that the measurement of bone density, for example prior to biomechanical testing, should be standardized to thawed or frozen specimens. Temperature should not be changed during measurements. When using score systems for data interpretation (e.g. T- or Z-score), BMD measurements should be performed only on thawed specimens.
authors.affiliation: Centre of Trauma and Hand and Reconstructive Surgery, Friedrich-Schiller-University Jena, Erlanger Allee 101, Jena, Germany. Dirk.Waehnert@uni-jena.de
authors.forename: Dirk
authors.initials: D
authors.lastname: Wähnert
authors.forename: Konrad L
authors.initials: KL
authors.lastname: Hoffmeier
authors.forename: Gabriele
authors.initials: G
authors.lastname: Lehmann
authors.forename: Rosemarie
authors.initials: R
authors.lastname: Fröber
authors.forename: Gunther O
authors.initials: GO
authors.lastname: Hofmann
authors.forename: Thomas
authors.initials: T
authors.lastname: Mückley
mesh_terms: D015502:Absorptiometry, Photon / Q000379:methods* / Q000592:standards*; D000368:Aged; D000369:Aged, 80 and over; D000886:Anthropometry / Q000379:methods; D016477:Artifacts; D001696:Biomechanical Phenomena / Q000502:physiology; D001831:Body Temperature / Q000502:physiology*; D015519:Bone Density / Q000502:physiology*; D002102:Cadaver; D005260:Female; D005269:Femur / Q000033:anatomy & histology / Q000000981:diagnostic imaging* / Q000502:physiology*; D005270:Femur Head / Q000033:anatomy & histology / Q000000981:diagnostic imaging / Q000502:physiology; D005272:Femur Neck / Q000033:anatomy & histology / Q000000981:diagnostic imaging / Q000502:physiology; D006801:Humans; D008297:Male; D008875:Middle Aged; D015203:Reproducibility of Results; D013696:Temperature