Design and Testing of a Traction/Distraction Knee Brace
Date
2018-12-18
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Thesis
Degree Level
Masters
Abstract
A new knee brace design is required to provide non-surgical distraction of the knee joint for extended periods of time. This knee brace needs to apply traction force to the joint directly, rather than indirectly unloading one compartment. In providing such a design, this research had two objectives: 1) to design a lower-leg knee brace that can apply traction load to the knee; and 2) to test prototypes of these lower-leg knee brace components and relate the traction load to wearer discomfort and interface force.
The first objective was met through prospective analysis and iterative design. A planar finite element (FE) model of the lower leg was used to analyse the effect of knee brace coverage. It was observed that increasing the coverage of the knee brace may reduce interface pressures and concentrations of force. A lower-leg knee brace was designed responding to this model, using fibreglass casts with embedded fasteners to transfer load. Braces were manufactured in three lengths for testing: 3”, 7”, and a combined (“mixed”) design with components from each.
Nine participants were recruited for pilot testing of the lower leg knee brace. A mechanical test frame was built to apply traction load to the participants’ legs through each of the prototype knee braces. The load in the test frame was increased in 3kgf increments as interface force measurements were taken. Participants self-reported their discomfort on an 11-point Likert scale or Numerical Rating Scale (NRS).
Results of the pilot study showed significant differences among the brace designs. The 3” design showed higher NRS scores than the 7” and mixed designs by a full NRS step. Graphical profiles of the interface force suggested that this difference may be the result of higher interface forces distributed across the smaller area of the 3” brace. However, no significant correlation between maximum interface force and self-reported pain was found. Parameters characterizing the shape of the participant’s lower legs indicated that leg shape may influence brace effectiveness.
This study concluded that a rigid knee brace is indeed a valid design, but a longer knee brace interface is required for the anterior surface of the leg to improve comfort. This length may not be required for the posterior surface. Further, this study demonstrated simple relationships among applied load, interface force, and wearer discomfort. Future work will adapt this design to the upper leg and optimize the design to minimize force concentrations at the joints.
Description
Keywords
Knee, Osteoarthritis, Distraction, Orthotics, Brace, Traction, Biomechanics
Citation
Degree
Master of Science (M.Sc.)
Department
Mechanical Engineering
Program
Mechanical Engineering