title: Dynamic plantar loading index detects altered foot function in individuals with rheumatoid arthritis but not changes due to orthotic use.
abstract: BACKGROUND
  Altered foot function is common in individuals with rheumatoid arthritis. Plantar pressure distributions during gait are regularly assessed in this patient group; however, the association between frequently reported magnitude-based pressure variables and clinical outcomes has not been clearly established. Recently, a novel approach to the analysis of plantar pressure distributions throughout stance phase, the dynamic plantar loading index, has been proposed. This study aimed to assess the utility of this index for measuring foot function in individuals with rheumatoid arthritis.
  
  
  METHODS
  Barefoot plantar pressures during gait were measured in 63 patients with rheumatoid arthritis and 51 matched controls. Additionally, 15 individuals with rheumatoid arthritis had in-shoe plantar pressures measured whilst walking in standardized footwear for two conditions: shoes-only; and shoes with prescribed custom foot orthoses. The dynamic plantar loading index was determined for all participants and conditions. Patient and control groups were compared for significant differences as were the shod and orthosis conditions.
  
  
  RESULTS
  The patient group was found to have a mean index of 0.19, significantly lower than the control group's index of 0.32 (p>0.001, 95% CI [0.054, 0.197]). No significant differences were found between the shoe-only and shoe plus orthosis conditions. The loading index was found to correlate with clinical measures of structural deformity.
  
  
  CONCLUSIONS
  The dynamic plantar loading index may be a useful tool for researchers and clinicians looking to objectively assess dynamic foot function in patients with rheumatoid arthritis; however, it may be unresponsive to changes caused by orthotic interventions in this patient group.
authors.affiliation: Institute for Applied Health Research, Glasgow Caledonian University, UK; Department of Orthopaedics and Sports Medicine, University of Washington, Seattle, USA. Electronic address: scott.telfer@gcu.ac.uk.
authors.forename: Scott
authors.initials: S
authors.lastname: Telfer
authors.affiliation: Life Sciences Department, Thomas More Kempen, Belgium.
authors.forename: Elien
authors.initials: E
authors.lastname: Baeten
authors.affiliation: School of Health, Sport and Bioscience, University of East London, UK.
authors.forename: Kellie S
authors.initials: KS
authors.lastname: Gibson
authors.affiliation: Institute for Applied Health Research, Glasgow Caledonian University, UK.
authors.forename: Martijn P
authors.initials: MP
authors.lastname: Steultjens
authors.affiliation: Institute for Applied Health Research, Glasgow Caledonian University, UK.
authors.forename: Deborah E
authors.initials: DE
authors.lastname: Turner
authors.affiliation: Institute for Applied Health Research, Glasgow Caledonian University, UK.
authors.forename: James
authors.initials: J
authors.lastname: Woodburn
authors.affiliation: Institute for Applied Health Research, Glasgow Caledonian University, UK.
authors.forename: Gordon J
authors.initials: GJ
authors.lastname: Hendry
mesh_terms: D000328:Adult; D000368:Aged; D001172:Arthritis, Rheumatoid / Q000503:physiopathology*; D001915:Braces; D016022:Case-Control Studies; D005260:Female; D005528:Foot / Q000503:physiopathology*; D061826:Foot Orthoses; D006801:Humans; D008297:Male; D008875:Middle Aged; D011312:Pressure; D016138:Walking / Q000502:physiology*; D016474:Weight-Bearing / Q000502:physiology*
keywords: Foot; Foot orthoses; Plantar pressure; Rheumatoid arthritis