Obesity is a severe concern worldwide and its prevalence is expected to continue to increase. Linked to diabetes, kidney disease, heart disease, and high blood pressure among other things, obesity has been identified as the forthcoming, largest preventable cause of mortality. Osteoarthritis, surgical consequences, distribution of subcutaneous adipose tissue, and alteration of joint biomechanics have vast implications in total joint repair (TJR). Previous studies have linked obesity to increased forces through weight-bearing lower extremities, alterations in gait, and risk of implant failure. The objectives of this study were to (1) provide a tool to predict lower extremity dimensions and shape variations of subcutaneous adipose tissue, (2) identify the degree to which obesity influences shape variation of the osseous anatomy of the knee joint, and (3) lay a foundation to compare the knee contact force of obese patients in activities of daily living.
Long-leg EOS films were obtained, retrospectively over 5 years, from 232 patients that were being seen at the Adult Reconstruction Clinic at the University of Iowa. Using custom Matlab algorithms, measurements of soft tissue distribution and lower extremity osseous anatomy were obtained and analyzed. Additionally knee contact force measurements were obtained through motion capture analysis and modeling in Anybody Technology.
Males and females had similar lower extremity shapes, with females having greater knee circumferences than males. The variability of PPT and PTT tended to be greater in females and increased with increasing BMI. Although similar in the anteroposterior direction, males tended to have on average 12mm wider proximal tibias in the mediolateral direction. Clinical observations of increased post-operative complications trend with these findings. The future of research into biomechanics of obesity will rely heavily on anatomic models of the obese lower extremities, which until this work did not exist.