title: Effect of tibial plateau fracture on lubrication function and composition of synovial fluid.
abstract: BACKGROUND
  Intra-articular fractures may hasten posttraumatic arthritis in patients who are typically too active and too young for joint replacement. Current orthopaedic treatment principles, including recreating anatomic alignment and establishing articular congruity, have not eliminated posttraumatic arthritis. Additional biomechanical and biological factors may contribute to the development of arthritis. The objective of the present study was to evaluate human synovial fluid for friction-lowering function and the concentrations of putative lubricant molecules following tibial plateau fractures.
  
  
  METHODS
  Synovial fluid specimens were obtained from the knees of eight patients (twenty-five to fifty-seven years old) with a tibial plateau fracture, with five specimens from the injured knee as plateau fracture synovial fluid and six specimens from the contralateral knee as control synovial fluid. Each specimen was centrifuged to obtain a fluid sample, separated from a cell pellet, for further analysis. For each fluid sample, the start-up (static) and steady-state (kinetic) friction coefficients in the boundary mode of lubrication were determined from a cartilage-on-cartilage biomechanical test of friction. Also, concentrations of the putative lubricants, hyaluronan and proteoglycan-4, as well as total protein, were determined for fluid samples.
  
  
  RESULTS
  The group of experimental samples were obtained at a mean (and standard deviation) of 11 ± 9 days after injury from patients with a mean age of 45 ± 13 years. Start-up and kinetic friction coefficients demonstrated similar trends and dependencies. The kinetic friction coefficients for human plateau fracture synovial fluid were approximately 100% higher than those for control human synovial fluid. Hyaluronan concentrations were ninefold lower for plateau fracture synovial fluid compared with the control synovial fluid, whereas proteoglycan-4 concentrations were more than twofold higher in plateau fracture synovial fluid compared with the control synovial fluid. Univariate and multivariate regression analysis indicated that kinetic friction coefficient increased as hyaluronan concentration decreased.
  
  
  CONCLUSIONS
  Knees afflicted with a tibial plateau fracture have synovial fluid with decreased lubrication properties in association with a decreased concentration of hyaluronan.
authors.affiliation: Department of Orthopaedic Surgery, Mail Code 8894, University of California, San Diego, 200 West Arbor Drive, San Diego, CA 92103-8894, USA.
authors.forename: Brooke L
authors.initials: BL
authors.lastname: Ballard
authors.forename: Jennifer M
authors.initials: JM
authors.lastname: Antonacci
authors.forename: Michele M
authors.initials: MM
authors.lastname: Temple-Wong
authors.forename: Alexander Y
authors.initials: AY
authors.lastname: Hui
authors.forename: Barbara L
authors.initials: BL
authors.lastname: Schumacher
authors.forename: William D
authors.initials: WD
authors.lastname: Bugbee
authors.forename: Alexandra K
authors.initials: AK
authors.lastname: Schwartz
authors.forename: Paul J
authors.initials: PJ
authors.lastname: Girard
authors.forename: Robert L
authors.initials: RL
authors.lastname: Sah
mesh_terms: D000328:Adult; D000704:Analysis of Variance; D001696:Biomechanical Phenomena; D005260:Female; D006801:Humans; D006820:Hyaluronic Acid / Q000378:metabolism; D057072:Intra-Articular Fractures / Q000378:metabolism*; D008153:Lubrication; D008297:Male; D008875:Middle Aged; D011509:Proteoglycans / Q000378:metabolism; D012044:Regression Analysis; D013582:Synovial Fluid / Q000737:chemistry*; D013978:Tibial Fractures / Q000378:metabolism*
chemical_list: D011509:Proteoglycans; D006820:Hyaluronic Acid