The objective of this study was to examine the link between radiographic measures
of bone quality and total knee implant migration as measured by radiostereometric
analysis (RSA). Two uncemented total knee arthroplasty studies (n=65) with RSA
and bone mineral density (BMD) exams up to two years post surgery, and one study
with cemented total knees with one year RSA data (n=18) were examined. Radiograph
image texture analysis was used to characterize the bone microarchitecture,
and a feasibility study was conducted to determine if a given x-ray machine could
be used to obtain bone mineral density at the same time as the RSA exams.
Random ForestTM ensemble classification tree statistical models classified patients
into groups based on implant migration with a range of cut-points. Models
based on bone texture parameters measured from the two year radiographs had a
sensitivity of 87.5% and specificity of 80% when classifying patients who had more
than 0.3mm maximum total point motion (MTPM) at two years using the one year
exam as reference. Other cut-points were examined, with models generally having
a lower specificity if the acceptable migration was smaller, and lower sensitivity if
higher migrations were tolerable. In a predictive model, post-operative bone texture
could be used to create a model with a sensitivity of 75% and a specificity of 80%
when predicting those subjects with cemented implants who went on to more than
0.4mm total migration by one year. Bone mineral density of the proximal tibia, as
determined by clinical scanners, was not found to increase the accuracy of implant
migration group classification.
An empirical fit to central regions of a purposed-built cross-wedge calibration
phantom returned residuals of less than ±1.5% for the bone-equivalent thicknesses.
The coefficient of variation of the region greyscale values in three images spread over
three days is under 4%, showing the stability of the system to hold a calibration
between phantom exams and patient scans. Scatter and dynamic range issues will
need to be considered for an accurate calibration across the full range of areal bone
mineral densities in the distal femur and proximal tibia.
| Identifer | oai:union.ndltd.org:LACETR/oai:collectionscanada.gc.ca:NSHD.ca#10222/15361 |
| Date | 31 July 2012 |
| Creators | Hurry, Jennifer |
| Source Sets | Library and Archives Canada ETDs Repository / Centre d'archives des thèses électroniques de Bibliothèque et Archives Canada |
| Language | English |
| Detected Language | English |
| Type | Thesis |
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