title: Quantification of differences in bone texture from plain radiographs in knees with and without osteoarthritis.
abstract: OBJECTIVE
  To quantify differences in bone texture between subjects with different stages of knee osteoarthritis (OA) and age- and gender-matched controls from plain radiographs using advanced image analysis methods.
  
  
  METHODS
  Altogether 203 knees were imaged using constant X-ray parameters and graded according to Kellgren-Lawrence (KL) grading scale (KL0: n = 110, KL1: n = 28, KL2: n = 27, KL3: n = 31, KL4: n = 7). Bone density-related and structure-related parameters were calculated from medial and lateral tibial subchondral bone plate and trabecular bone and from femur. Density-related parameters were derived from grayscale values and structure-related parameters from Laplacian- and local binary patterns (LBP)-based images.
  
  
  RESULTS
  Reproducibilities of structure-related parameters were better than bone density-related parameters. Bone density-related parameters were significantly (P < 0.05) higher in KL2-4 groups than in control group (KL0) in medial tibial subchondral bone plate and trabecular bone. LBP-based structure parameters differed significantly between KL0 and KL2-4 groups in medial subchondral bone plate, between KL0 and KL1-4 groups in medial and lateral trabecular bone, and between KL0 and KL1-4/KL2-4 in medial and lateral femur. Laplacian-based parameters differed significantly between KL0 and KL2-4 groups in medial side regions-of-interest (ROIs).
  
  
  CONCLUSIONS
  Our results indicate that the changes in bone texture in knee OA can be quantitatively evaluated from plain radiographs using advanced image analysis. Based on the results, increased bone density can be directly estimated if the X-ray imaging conditions are constant between patients. However, structural analysis of bone was more reproducible than direct evaluation of grayscale values, and is therefore better suited for quantitative analysis when imaging conditions are variable.
authors.affiliation: Department of Medical Technology, University of Oulu, Oulu, Finland; Medical Research Center Oulu, Oulu University Hospital and University of Oulu, Oulu, Finland. Electronic address: jukka.hirvasniemi@oulu.fi.
authors.forename: J
authors.initials: J
authors.lastname: Hirvasniemi
authors.affiliation: Department of Medical Technology, University of Oulu, Oulu, Finland; Medical Research Center Oulu, Oulu University Hospital and University of Oulu, Oulu, Finland. Electronic address: jerome.thevenot@oulu.fi.
authors.forename: J
authors.initials: J
authors.lastname: Thevenot
authors.affiliation: Department of Medical Technology, University of Oulu, Oulu, Finland. Electronic address: ville.immonen2@gmail.com.
authors.forename: V
authors.initials: V
authors.lastname: Immonen
authors.affiliation: Muonio Health Centre, Muonio, Finland. Electronic address: tuomas.liikavainio@muonio.fi.
authors.forename: T
authors.initials: T
authors.lastname: Liikavainio
authors.affiliation: Department of Medical Technology, University of Oulu, Oulu, Finland; Medical Research Center Oulu, Oulu University Hospital and University of Oulu, Oulu, Finland. Electronic address: pasi.pulkkinen@oulu.fi.
authors.forename: P
authors.initials: P
authors.lastname: Pulkkinen
authors.affiliation: Department of Medical Technology, University of Oulu, Oulu, Finland; Medical Research Center Oulu, Oulu University Hospital and University of Oulu, Oulu, Finland; Department of Diagnostic Radiology, Oulu University Hospital, Oulu, Finland. Electronic address: timo.jamsa@oulu.fi.
authors.forename: T
authors.initials: T
authors.lastname: Jämsä
authors.affiliation: Institute of Clinical Medicine, University of Eastern Finland, Kuopio, Finland; Department of Physical and Rehabilitation Medicine, Kuopio University Hospital, Kuopio, Finland. Electronic address: jari.arokoski@kuh.fi.
authors.forename: J
authors.initials: J
authors.lastname: Arokoski
authors.affiliation: Department of Medical Technology, University of Oulu, Oulu, Finland; Medical Research Center Oulu, Oulu University Hospital and University of Oulu, Oulu, Finland; Department of Diagnostic Radiology, Oulu University Hospital, Oulu, Finland. Electronic address: simo.saarakkala@oulu.fi.
authors.forename: S
authors.initials: S
authors.lastname: Saarakkala
mesh_terms: D015519:Bone Density; D016022:Case-Control Studies; D005269:Femur / Q000000981:diagnostic imaging*; D006801:Humans; D007719:Knee Joint / Q000000981:diagnostic imaging; D008297:Male; D008875:Middle Aged; D020370:Osteoarthritis, Knee / Q000000981:diagnostic imaging*; D011859:Radiography; D015203:Reproducibility of Results; D013977:Tibia / Q000000981:diagnostic imaging*
keywords: Bone; Knee; Osteoarthritis; Radiography; Texture analysis