title: Assessment of two-dimensional (2D) and three-dimensional (3D) lower limb measurements in adults: Comparison of micro-dose and low-dose biplanar radiographs.
abstract: OBJECTIVE
  To evaluate reliability of 2D and 3D lower limb measurements in adults using micro-dose compared to low-dose biplanar radiographs(BPR).
  
  
  METHODS
  One hundred patients (mean 54.9 years) were examined twice using micro-dose and low-dose BPR. Length and mechanical axis of lower limbs were measured on the antero-posterior(ap) micro-dose and low-dose images by two independent readers. Femoral and tibial torsions of 50 patients were measured by two independent readers using reconstructed 3D-models based on the micro-dose and low-dose BPR. Intermethod and interreader agreements were calculated using descriptive statistics, intraclass-correlation-coefficient(ICC), and Bland-Altman analysis.
  
  
  RESULTS
  Mean interreader-differences on micro-dose were 0.3 cm(range 0-1.0)/ 0.7°(0-2.9) for limb length/axis and 0.4 cm (0-1.0)/0.8°(0-3.3) on low-dose BPR. Mean intermethod-difference was 0.04 cm ± 0.2/0.04° ± 0.6 for limb length/axis. Interreader-ICC for limb length/axis was 0.999/0.991 on micro-dose and 0.999/0.987 on low-dose BPR. Interreader-ICC for micro-dose was 0.879/0.826 for femoral/ tibial torsion, for low-dose BPR was 0.924/0.909. Mean interreader-differences on micro-dose/low-dose BPR were 3°(0-13°)/2°(0°-12°) for femoral and 4°(0-18°)/3°(0°-10°) for tibial torsion. Mean intermethod-difference was -0.1° ± 5.0/-0.4° ± 2.9 for femoral/tibial torsion. Mean dose-area-product was significantly lower (9.9 times;p < 0.001) for micro-dose BPR.
  
  
  CONCLUSIONS
  2D-and 3D-measurements of lower limbs based on micro-dose BPR are reliable and provide a 10-times lower radiation dose.
  
  
  CONCLUSIONS
  • Lower limb length and mechanical axis can be reliably measured with micro-dose. • Femoral and tibial torsion can be reliably assessed with micro-dose. • Micro-dose allows a huge reduction of radiation exposure.
authors.affiliation: Radiology, Orthopedic University Hospital Balgrist, Forchstrasse 340, CH-8008, Zurich, Switzerland. andrea.rosskopf@balgrist.ch.|Faculty of Medicine, University of Zurich, Zurich, Switzerland. andrea.rosskopf@balgrist.ch.
authors.forename: Andrea B
authors.initials: AB
authors.lastname: Rosskopf
authors.affiliation: Radiology, Orthopedic University Hospital Balgrist, Forchstrasse 340, CH-8008, Zurich, Switzerland.|Faculty of Medicine, University of Zurich, Zurich, Switzerland.
authors.forename: Christian W A
authors.initials: CW
authors.lastname: Pfirrmann
authors.affiliation: Radiology, Orthopedic University Hospital Balgrist, Forchstrasse 340, CH-8008, Zurich, Switzerland.|Faculty of Medicine, University of Zurich, Zurich, Switzerland.
authors.forename: Florian M
authors.initials: FM
authors.lastname: Buck
mesh_terms: D000328:Adult; D000368:Aged; D004307:Dose-Response Relationship, Radiation; D005260:Female; D005269:Femur / Q000033:anatomy & histology* / Q000000981:diagnostic imaging; D006801:Humans; D021621:Imaging, Three-Dimensional / Q000379:methods; D035002:Lower Extremity / Q000033:anatomy & histology / Q000000981:diagnostic imaging; D008297:Male; D010388:Pelvis; D011829:Radiation Dosage; D000069079:Radiation Exposure; D011859:Radiography; D015203:Reproducibility of Results; D013977:Tibia / Q000033:anatomy & histology* / Q000000981:diagnostic imaging; D014057:Tomography, X-Ray Computed / Q000379:methods
keywords: Biplanar radiographs; Femoral torsion; Lower limbs; Micro-dose; Tibial torsion