title: Total contact cast wall load in patients with a plantar forefoot ulcer and diabetes.
abstract: BACKGROUND
  The total contact cast (TCC) is an effective intervention to reduce plantar pressure in patients with diabetes and a plantar forefoot ulcer. The walls of the TCC have been indirectly shown to bear approximately 30 % of the plantar load. A new direct method to measure inside the TCC walls with capacitance sensors has shown that the anterodistal and posterolateral-distal regions of the lower leg bear the highest load. The objective of this study was to directly measure these two regions in patients with Diabetes and a plantar forefoot ulcer to further understand the mechanism of pressure reduction in the TCC.
  
  
  METHODS
  A TCC was applied to 17 patients with Diabetes and a plantar forefoot ulcer. TCC wall load (contact area, peak pressure and max force) at the anterodistal and posterolateral-distal regions of the lower leg were evaluated with two capacitance sensor strips measuring 90 cm(2) (pliance®, novel GmbH, Germany). Plantar load (contact area, peak pressure and max force) was measured with a capacitance sensor insole (pedar®, novel GmbH, Germany) placed inside the TCC. Both pedar® and pliance® collected data simultaneously at a sampling rate of 50Hz synchronised to heel strike. The magnitude of TCC wall load as a proportion of plantar load was calculated. The TCC walls were then removed to determine the differences in plantar loading between the TCC and the cut down shoe-cast for the whole foot, rearfoot, midfoot and forefoot (region of interest).
  
  
  RESULTS
  TCC wall load was substantial. The anterodistal lower leg recorded 48 % and the posterolateral-distal lower leg recorded 34 % of plantar contact area. The anterodistal lower leg recorded 28 % and the posterolateral-distal lower leg recorded 12 % of plantar peak pressure. The anterodistal lower leg recorded 12 % and the posterolateral-distal lower leg recorded 4 % of plantar max force. There were significant differences in plantar load between the TCC and the cut down shoe-cast for the whole foot, rearfoot, midfoot and forefoot (region of ulcer). Contact area significantly increased by 5 % beneath the whole foot, 8 % at the midfoot and 6 % at the forefoot in the shoe-cast (p < 0.05). Peak pressure significantly increased by 8 % beneath the midfoot and 13 % at the forefoot in the shoe-cast (p < 0.05). Max force significantly increased 6 % beneath the midfoot in the (shoe-cast p < 0.05).
  
  
  CONCLUSIONS
  In patients with diabetes and a plantar forefoot ulcer, the walls of the TCC bear considerable load. Reduced plantar contact area in the TCC compared to the shoe-cast suggests that the foot is suspended by the considerable load bearing capacity of the walls of the TCC which contributes mechanically to the pressure reduction and redistribution properties of the TCC.
authors.affiliation: Foot Wound Clinic, Department of Surgery, Westmead Hospital, Sydney, 2145 NSW Australia ; Department of Surgery, Univeristy of Sydney, Westmead Hospital, Sydney, Australia.
authors.forename: Lindy
authors.initials: L
authors.lastname: Begg
authors.affiliation: Centre for Chronic Disease Prevention, College of Health and Biomedicine, Victoria University, Melbourne, Australia ; Institute of Sport, Exercise and Active Living, Victoria University, Melbourne, Victoria Australia.
authors.forename: Patrick
authors.initials: P
authors.lastname: McLaughlin
authors.affiliation: Foot Wound Clinic, Department of Surgery, Westmead Hospital, Sydney, 2145 NSW Australia ; Department of Surgery, Univeristy of Sydney, Westmead Hospital, Sydney, Australia.
authors.forename: Mauro
authors.initials: M
authors.lastname: Vicaretti
authors.affiliation: Foot Wound Clinic, Department of Surgery, Westmead Hospital, Sydney, 2145 NSW Australia ; Department of Surgery, Univeristy of Sydney, Westmead Hospital, Sydney, Australia.
authors.forename: John
authors.initials: J
authors.lastname: Fletcher
authors.affiliation: Foot Wound Clinic, Department of Surgery, Westmead Hospital, Sydney, 2145 NSW Australia ; Arthritis and Musculoskeletal Research Group, Faculty of Health Sciences, The University of Sydney, Sydney, New South Wales Australia ; Paediatric Gait Analysis Service of New South Wales, Sydney Children's Hospitals Network (Randwick and Westmead), Sydney, New South Wales Australia.
authors.forename: Joshua
authors.initials: J
authors.lastname: Burns
mesh_terms: D001696:Biomechanical Phenomena / Q000502:physiology; D002370:Casts, Surgical; D017719:Diabetic Foot / Q000503:physiopathology* / Q000628:therapy*; D005260:Female; D005545:Forefoot, Human / Q000503:physiopathology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D011312:Pressure; D012815:Signal Processing, Computer-Assisted / Q000295:instrumentation; D016138:Walking / Q000502:physiology*
keywords: Diabetes; Foot ulcer; Offloading; Plantar pressure; Total contact cast; Wound