Rocker-soled Shoe

• Designed to roll or rock a foot forward when walking
• Rocks/rolls forward during the stance phase of gait
• The thicker sole has to have a degree of rigidity to limit bending
• Can incorporate specific curves at different parts of the shoe
  • 2 curved rocker
  • 3 curved rocker
  • Radius from ankle centre, hip centre, knee centre

Purpose

• They are used to change a specific biomechanical pattern during walking

  • Used to change the kinematic pattern, e.g:

    • limit movement of the 1st MTP joint
    • reduce ankle/knee range of motion

  • Used to change kinetic (moment pattern) and the ankle, knee or hip

    • Result in a change in the centre of pressure and/or direction of the ground reaction force vector

  • Used to change the pressure distribution under the foot (plantar pressure distribution)

  • Used to change muscle activation patterns

Other possible effects (claimed by manufacturers):

• Decreased metabolic energy consumption
• Balance training
• Improving overall body posture
• Increasing muscle strength
• These have not been backed up by clinical assessments!

Clinical Management:

• Used to manage a range of clinical conditions e.g:
  • Osteoarthritis of the foot
  • Intermittent claudication
  • Plantar fascilitis

Foot Ulceration in Diabetes

• Patients with diabetes are susceptible to:

  • Plantar ulcers (caused by increased pressure)

    • Pressures above 200 KPa can cause ulceration (Owings et al. (2009))

  • Heel ulcers (caused by increased pressure)

  • Dorsal ulcers (caused by poor fit)

  • Infection/bacterial growth (caused by increased humidity/temperature)

Research Designs for Optimising Footwear Design

• Can consider 3 levels of research questions

  • Level 1: Questions to describe phenomena

    • theoretical or conceptual material but nothing known empirically
    • lead to descriptive designs, more complex research
      

  • Level 2: Questions which explore relationships

    • study relationships among phenomena which have already been studied at descriptive level
      

  • Level 3: Questions which test knowledge about cause-effect

    • contain predictive statements about what will happen to one variable on the basis of knowing another
    • manipulate 1 variable to understand the effect it has on another

• Operationalisation: reducing phenomena to a number in order to carry out statistical analysis

  • if the outcome is not chosen appropriately, the study has limited validity

Example: - Level 1: Do patients use their footwear at home - Level 2: Relationship between footwear use and x muscle strength - Level 3: Effect of changing footwear on x muscle strength

• Rocker profile: number of parameters e.g.

  • rocker angle for curved rocker shoe
  • apex position
  • rocker axis

• Repeated measures design:

  • all people exposed to different conditions
  • e.g. testing a number of different shoe designs
    • in-shoe pressure sensor used to measure plantar pressure to quantify data
    • calculate pressure curve for sensors at a given time
    • locate area of peak pressure

Purpose of footwear for people with diabetes

• Elevated plantar pressure is a known risk factor for ulceration

• Footwear needs to be aesthetically pleasing as well as clinically effective

• Types of footwear for patients with diabetes

  • extra depth shoes
  • flexible shoes
  • traditional rocker shoes
  • curved rocker shoes

• Acceptability of footwear for patients

  • influenced by:

    • relative risk of adverse health outcome
    • previous experience with adverse health outcome

  • Prevention is better than treatment

    • better to target those who are at moderate risk with acceptable footwear choice
      

  • Manufacturing trade-off with outside geometry to create specific rocker

  • If we want to increase rocker angle, have to have a thicker outsole

    • thicker outsole = more effective
    • But less favourable to patients

Curved Rocker shoe: - Four footwear features: - Rocker angle - Apex position - Apex angle - Sole stiffness

• Typical shoe:

  • apex angle of 55% of shoe length
  • rocker angle of 10 degrees
  • rocker axis aligned with metatarsal break

• Need a control study varying each of the design features to see effect on the foot