Cross-sectional associations between variations in ankle shape by statistical shape modeling, injury history, and race
Ankle shape and is a potentially important factor in the development of ankle OA and is often linked to history of injury as well as with race.
Injury is a major risk factor for osteoarthritis (OA), a common chronic disease of the joints that is one of the leading cause of disability among adults in the United States. Injuries likely accelerate the progression of OA in weight bearing joints by altering the joint alignment and biomechanics, thereby changing the magnitudes and locations of peak joint forces during movements, resulting in abnormal loading of the cartilage, subchondral bone, and ligamentous structures.
Injury is a major risk factor for osteoarthritis (OA), a common chronic disease of the joints that is one of the leading cause of disability among adults in the United States. Injuries likely accelerate the progression of OA in weight bearing joints by altering the joint alignment and biomechanics, thereby changing the magnitudes and locations of peak joint forces during movements, resulting in abnormal loading of the cartilage, subchondral bone, and ligamentous structures. According to the present study, OA of the ankle is less common than OA of other lower body joints.
The etiology is of primary OA most often seen in the hip and knee and reported 80% higher odds of ankle OA among those with prior ankle injury. It has been noted that the success of joint replacement in ankle OA is markedly less than that at the hip and knee so newer implants and procedures suggest some progress. There is a long latency period of around 20 years, between injury and end-stage ankle OA, a time when identification of those at risk could be the key in preventing future disability. Sprains and strains, most of which involve the ankle, were the number one cause of Emergency Department evaluation in the U.S. during 2010 to 2013. In OA, joint shape could be assessed using radiography and may help identify the individuals at higher risk of OA. This provides insights into possible biomechanical mechanisms contributing to the development of OA and suggest various strategies like weight loss, exercise to their patients for reducing risk.
Statistical Shape Modeling (SSM) was developed by Cootes, et al., as a way of segmenting images. It is an application tool for quantifying bone shape and was pioneered by Dr. Gregory, to model variations in hip shapes associated with risk of hip OA. In this study, “ankle shape” refers to the radiographic two dimensional shapes and relationships (alignment) between shapes, of the distal tibia, talus, calcaneus, and navicular in the lateral view and in the analysis, explore the cross-sectional association between ankle shape by SSM and prior report of injury in a large community-based cohort, including African American and white men and women, as a potential intermediary step in the development of OA.
Rationale behind the research
- Variations in ankle shape are associated with self-reported ankle injury and differences in ankle shape to reduce the cause of OA which is not well known to clinical diagnosis.
- This study defines the ankle shape affected in injury which is an important factor in deciding strategies for the treatment of ankle OA.
- To study ankle injury variations in ankle shape and history of injury as well as with race to cause OA.
Study outcome measures
- To define ankle shape producing a mean shape and a set of continuous variables (modes). Nineteen modes were included in a logistic regression model with injury status as the dependent variable, adjusted for intra-person correlation, sex, race, body mass index (BMI), baseline OA radiographic grade, and baseline symptoms.
Time Points: Baseline and up to 12 months.
- A significant association were seen between injury status and modes 1, 6, 13, and 19 in a model adjusted only for intra-person correlation. In a fully adjusted model, race strongly affected the estimate for mode 1 but was not statistically significant.
In this community-based cohort, it was found that variations in ankle shape are associated with self-reported ankle injury and that there are racial differences in the ankle shapes. In the current study, different modes of SSM can only be qualitatively assessed by visualizing variations in the modes, as there is no standardized reference cohort for joint shape, and thus the variations seen are specific to this population. Most of the variations identified can be summarized as alterations in bone size and in alignment between the bones.
In particular, mode 1 demonstrates an apparent shift in relative alignment that affects all 3 (tibiotalar, talonavicular, and subtalar) joints visualized on the lateral ankle radiographs. These novel findings may indicate a change in ankle morphology following injury, or that ankle morphology predisposes to injury. In either case, ankle shape could be an important factor in the development of ankle OA.