Effects of family history of osteoarthritis on knee morphology -- A shape model study

Date

2010

Authors

Wiemers, Jason Dean

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Abstract

Osteoarthritis is a slowly progressing disease that usually occurs later in life and is characterized by pain, swelling and inflammation of the joints. It is the leading cause of activity limitation and physical disability and a great burden to our society in terms of resources spent on treatment and surgery as well as what is lost from affected individuals not working.

The Osteoarthritis Initiative (OAI), established by the National Institute of Health with data collection beginning in 2004, is a large-scale attempt to identify biomarkers for the disease that could further our understanding of the etiology and pathophysiology of osteoarthritis. My investigation utilizes the OAI MRI database that has been created and made available to the public.

Baseline MR images of knees were obtained for a specific subset of individuals within the large Incidence cohort of the OAI. Subjects were chosen based on exclusion of risk factors that could have an influence on osteoarthritis onset or be associated with changes to the individual's congenital knee shape. The individuals chosen established two distinct groups. One cohort has an immediate family history for total knee replacement and the other does not. The groups were age and BMI matched for a total of 108 subjects.

Differences in shape between these two distinct subgroups were evaluated for a genetic influence on knee geometry that may be detectable prior to the onset of clinically significant osteoarthritis. Differences in average femoral and tibial bone geometry were investigated by comparing average bone surfaces determined for the family history (FH) and no family history (NFH) groups. Significant differences in knee geometry between the two subsets were identified through the application of statistical shape modeling methods. The femur shape model revealed six shape modes that were significantly different between the groups, and the tibia shape model uncovered four significantly different modes. In order to further the understanding of what the principal shape modes mean, discrete measures from previous studies were identified and calculated for each individual bone surface. Although the discrete measures did not show differences between the two groups, they were used to investigate the geometric traits described by the principal modes. Individual shape modes with significant differences were altered and the discrete measures were evaluated for change in magnitude from the average shape. Thus, an overview across all discrete measures was established that attempts to identify the three dimensional pattern of geometry for each principal shape mode.

A link has been established for subjects without clinically significant osteoarthritis that associates subchondral bone knee geometry with a family history for a total knee replacement. This technique has identified differences in shape between those with and without a family history and may have the potential to distinguish or classify those that are at an increased risk for osteoarthritis based on the shape of their femur and tibia.

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Keywords

Genetics, Knee Shape, Osteoarthritis, Statistical Shape Modeling

Citation

Department

Biomedical Engineering