title: Cortical Bone Thickness of the Distal Part of the Tibia Predicts Bone Mineral Density.
abstract: BACKGROUND
  Poor bone density may affect surgical planning, treatment outcome, and postoperative protocols. Many patients with foot and ankle problems have not undergone a dual x-ray absorptiometry (DXA) scan, which is currently the gold standard for determining bone density. The purpose of this study was to determine if the cortical bone thickness (CBT) of the distal part of the tibia measured on radiographs correlated with bone mineral density.
  
  
  METHODS
  After exclusion criteria were applied, 167 consecutive adult patients (mean age and standard deviation [SD], 62 ± 11.62 years) who had had standardized ankle radiographs and a DXA scan within 6 months of each other were included in this retrospective study. The CBT was measured with both the gauge and the average method on standardized anteroposterior, lateral, and hindfoot alignment radiographs. The relationship between CBT in the distal part of the tibia and DXA findings in the hip, proximal part of the femur, and lumbar spine was assessed with Pearson correlations. The interrater and intrarater reliability of CBT measurements was assessed with intraclass correlation coefficients. Subgroup analysis was performed to determine the ability of CBT thresholds to predict osteoporosis.
  
  
  RESULTS
  Average CBT measurements on the anteroposterior, lateral, and hindfoot alignment views strongly correlated with DXA findings in the proximal part of the femur (r = 0.70, 0.64, and 0.55, respectively; p < 0.0001), the hip (r = 0.74, 0.67, and 0.53; p < 0.0001), and the lumbar spine (r = 0.61, 0.60, and 0.47; p < 0.0001). The interrater and intrarater reliability of the CBT measurements was excellent. Use of a 3.5-mm average CBT of the distal part of the tibia on the anteroposterior view as the threshold value for predicting osteoporosis (T score less than -2.5) had a sensitivity of 100%, a specificity of 25%, an accuracy of 33%, a positive predictive value of 19%, and a negative predictive value of 100%.
  
  
  CONCLUSIONS
  Measurement of the average CBT of the distal part of the tibia is a quick and reliable method for obtaining information on bone quality. CBT measured on standard ankle radiographs correlated strongly with DXA results and may prove to be a useful screening tool for osteoporosis.
  
  
  METHODS
  Diagnostic Level II. See Instructions for Authors for a complete description of levels of evidence.
authors.affiliation: University of Iowa Hospitals and Clinics, Iowa City, Iowa Jalanpatterson@gmail.com.
authors.forename: Jason
authors.initials: J
authors.lastname: Patterson
authors.affiliation: University of Iowa Hospitals and Clinics, Iowa City, Iowa.
authors.forename: Chamnanni
authors.initials: C
authors.lastname: Rungprai
authors.affiliation: University of Iowa Hospitals and Clinics, Iowa City, Iowa.
authors.forename: Taylor
authors.initials: T
authors.lastname: Den Hartog
authors.affiliation: University of Iowa Hospitals and Clinics, Iowa City, Iowa.
authors.forename: Yubo
authors.initials: Y
authors.lastname: Gao
authors.affiliation: University of Iowa Hospitals and Clinics, Iowa City, Iowa.
authors.forename: Annunziato
authors.initials: A
authors.lastname: Amendola
authors.affiliation: University of Iowa Hospitals and Clinics, Iowa City, Iowa.
authors.forename: Phinit
authors.initials: P
authors.lastname: Phisitkul
authors.affiliation: University of Iowa Hospitals and Clinics, Iowa City, Iowa.
authors.forename: John
authors.initials: J
authors.lastname: Femino
mesh_terms: D015502:Absorptiometry, Photon; D000368:Aged; D015519:Bone Density / Q000502:physiology*; D000071538:Cortical Bone / Q000000981:diagnostic imaging*; D005260:Female; D005269:Femur / Q000000981:diagnostic imaging; D006801:Humans; D008159:Lumbar Vertebrae / Q000000981:diagnostic imaging; D008297:Male; D008875:Middle Aged; D010024:Osteoporosis / Q000000981:diagnostic imaging*; D011859:Radiography / Q000379:methods*; D012189:Retrospective Studies; D013977:Tibia / Q000000981:diagnostic imaging*