Modelling & Experimental Investigations Of Distal Radius Surface Strain Distributions During Off-Axis Loading
| dc.contributor.advisor | Johnston, James (J.D.) | |
| dc.contributor.advisor | Kontulainen, Saija | |
| dc.contributor.committeeMember | Dolovich, Allan T. | |
| dc.contributor.committeeMember | Edwards, Brent W. | |
| dc.creator | Adam, Madison J.P. | |
| dc.date.accessioned | 2024-08-23T15:21:02Z | |
| dc.date.available | 2024-08-23T15:21:02Z | |
| dc.date.copyright | 2024 | |
| dc.date.created | 2024-08 | |
| dc.date.issued | 2024-08-23 | |
| dc.date.submitted | August 2024 | |
| dc.date.updated | 2024-08-23T15:21:02Z | |
| dc.description.abstract | Osteoporosis is a widespread bone disease where bones become less dense (low bone mass) and the internal structure of bone tissue breaks down, leading to weaker bones that are more prone to fracture. Distal radius fractures (Colles’ type fracture) are one of the most common types of fractures to occur. Loading is generally assumed to be purely axial, with forces aligned with the length of the distal radius when simulating a fall onto the outstretched hand. However, the mechanics of distal radius fractures are not well understood and contributions to fracture from bending caused from off-axis loading may contribute to fractures more than previously considered. The objectives of this thesis are 1) to investigate bone strain at the distal radius by creating a subject-specific two-dimensional (2D) finite element (FE) model to evaluate tensile and compressive strains on the palmar and dorsal surfaces during off-axis loading, and 2) to evaluate experimental bone strain distributions during off-axis loading of cadaveric wrist specimens to failure. Two studies were conducted to evaluate the loading characteristics of the distal radius under off-axis conditions. First a 2D ANSYS Finite Element model was created from the sagittal segmented data of one cadaveric specimen. Off-axis loading resulting from palmar load transferred through the trapezium, scaphoid/lunate bones and balanced by the palmar ligaments created a moment around the centerline of the distal radius near the common fracture location. Surface strain measurements around the common fracture site were measured from the model during off-axis loading. The second study completed two testing methods: 1) non-destructive testing measuring surface strain values during a simulated fall onto the outstretched hand at four angles (0°, 15°, 22.5°, and 30°) under dorsiflexion, 2) destructive testing at 15° attempting to replicate Colles-type fractures experienced during a fall onto the outstretched hand. Inclusion of off-axis loading in the first study resulted in Tension to Compression (T:C) ratios ranging from 0.55 to 0.71 near the common fracture site from the ANSYS finite element simulation. Peak principal compressive strain found was 6,212µε and peak tensile principal strain was 4,397µε. The palmar surface experiences a dominant tensile strain. As expected, the ligament representing radiocarpal ligaments between the distal radius and carpal bones is under tensile force. Load sensitivity was found for five different load locations. Mechanical testing in the second study involved loading each specimen, resulting in the applied force being directed approximately at the location of the scaphoid and trapezium carpal bones with the hand in dorsiflexion. The tensile (palmar) and compressive (dorsal) strain for each loading angle (0º, 15º, 22.5º, and 30º) were found to indicate a transition from dominant compressive (dorsal) strain to larger in magnitude tensile (palmar) strain with increasing angulation. With 0° angulation, primary compressive loading was found; significantly larger tensile strains were found under increases in dorsal angulation resulting in an increase in bending moments experienced during loads. Lateral strain was compressive but smaller in magnitude than either dorsal or palmar results. Purely axial (0°) loading had a decrease in T:C ratio as more force was applied: 0.44 to 0.28. For further off-axis loading at 22.5° and 30°, T:C ratios were 0.51 to 0.52 and 0.57 to 0.58 respectively. Fracture testing resulted in two transverse fractures of the distal radius. Failure loads were 822 N and 375 N. The third tested specimen did not fracture, but rather experienced a dislocation of the radiocarpal joint. For the two failed specimens, distal radius fracture patterns were consistent with the classification of Colles’ type fracture, with fracture in the transverse metaphyseal region (25-40mm proximal to carpal joint), dorsal angulation of the fragment and palmar tilt. | |
| dc.format.mimetype | application/pdf | |
| dc.identifier.uri | https://hdl.handle.net/10388/15929 | |
| dc.language.iso | en | |
| dc.subject | Distal Radius | |
| dc.subject | Surface Strain | |
| dc.subject | FEA | |
| dc.subject | Mechanical Testing | |
| dc.subject | ||
| dc.title | Modelling & Experimental Investigations Of Distal Radius Surface Strain Distributions During Off-Axis Loading | |
| dc.type | Thesis | |
| dc.type.material | text | |
| thesis.degree.department | Mechanical Engineering | |
| thesis.degree.discipline | Mechanical Engineering | |
| thesis.degree.grantor | University of Saskatchewan | |
| thesis.degree.level | Masters | |
| thesis.degree.name | Master of Science (M.Sc.) |