The surface of bones: methods of recording entheseal changes

Entheses, which are macroscopically visible three-dimensional (3D) features on bones where muscles attach, have a complex etiology that includes muscle use in activities, age, and body size. Most studies of entheseal changes are based on scoring methods. Scoring methods often have high observer error rates and are often analyzed with low power statistics. Furthermore, scoring methods fail to capture the complexity of enthesis morphology, which includes proliferative and erosive traits that can be viewed as a 3D topography similar to landscapes. Recent studies have employed both two-dimensional metric data and 3D data from laser scans and CT-scans. Using a variety of software packages, anthropologists have displayed the scanned entheses in color coded topographical maps that can be moved and rotated to reveal entheses' complex morphology. The quantitative nature of these data, which include 3D surface area and fractal dimensions, is less subjective and statistical tests are easier to apply, but error rates are still problematic for some measures. Additionally, these studies reveal that entheseal changes correlate with age and body size; these correlations are sometimes considered problematic since the correlations hinder activity reconstructions, which is often the goal when examining entheses.