Heli Maijanen

Stature and body mass estimation from skeletal remains in the European Holocene

Techniques that are currently available for estimating stature and body mass from European skeletal remains are all subject to various limitations. Here, we develop new prediction equations based on large skeletal samples representing much of the continent and temporal periods ranging from the Mesolithic to the 20th century. Anatomical reconstruction of stature is carried out for 501 individuals, and body mass is calculated from estimated stature and biiliac breadth in 1,145 individuals. These data are used to derive stature estimation formulae based on long bone lengths and body mass estimation formulae based on femoral head breadth. Prediction accuracy is superior to that of previously available methods. No systematic geographic or temporal variation in prediction errors is apparent, except in tibial estimation of stature, where northern and southern European formulae are necessary because of the presence of relatively longer tibiae in southern samples. Thus, these equations should bebroadly applicable to European Holocene skeletal samples.

Knee osteoarthritis has doubled in prevalence since the mid-20th century

Significance Knee osteoarthritis is a highly prevalent, disabling joint disease with causes that remain poorly understood but are commonly attributed to aging and obesity. To gain insight into the etiology of knee osteoarthritis, this study traces long-term trends in the disease in the United States using large skeletal samples spanning from prehistoric times to the present. We show that knee osteoarthritis long existed at low frequencies, but since the mid-20th century, the disease has doubled in prevalence. Our analyses contradict the view that the recent surge in knee osteoarthritis occurred simply because people live longer and are more commonly obese. Instead, our results highlight the need to study additional, likely preventable risk factors that have become ubiquitous within the last half-century. Knee osteoarthritis (OA) is believed to be highly prevalent today because of recent increases in life expectancy and body mass index (BMI), but this assumption has not been tested using long-term historical or evolutionary data. We analyzed long-term trends in knee OA prevalence in the United States using cadaver-derived skeletons of people aged ≥50 y whose BMI at death was documented and who lived during the early industrial era (1800s to early 1900s; n = 1,581) and the modern postindustrial era (late 1900s to early 2000s; n = 819). Knee OA among individuals estimated to be ≥50 y old was also assessed in archeologically derived skeletons of prehistoric hunter-gatherers and early farmers (6000–300 B.P.; n = 176). OA was diagnosed based on the presence of eburnation (polish from bone-on-bone contact). Overall, knee OA prevalence was found to be 16% among the postindustrial sample but only 6% and 8% among the early industrial and prehistoric samples, respectively. After controlling for age, BMI, and other variables, knee OA prevalence was 2.1-fold higher (95% confidence interval, 1.5–3.1) in the postindustrial sample than in the early industrial sample. Our results indicate that increases in longevity and BMI are insufficient to explain the approximate doubling of knee OA prevalence that has occurred in the United States since the mid-20th century. Knee OA is thus more preventable than is commonly assumed, but prevention will require research on additional independent risk factors that either arose or have become amplified in the postindustrial era.

Temporal Trends in Vertebral Size and Shape from Medieval to Modern-Day

Human lumbar vertebrae support the weight of the upper body. Loads lifted and carried by the upper extremities cause significant loading stress to the vertebral bodies. It is well established that trauma-induced vertebral fractures are common especially among elderly people. The aim of this study was to investigate the morphological factors that could have affected the prevalence of trauma-related vertebral fractures from medieval times to the present day. To determine if morphological differences existed in the size and shape of the vertebral body between medieval times and the present day, the vertebral body size and shape was measured from the 4th lumbar vertebra using magnetic resonance imaging (MRI) and standard osteometric calipers. The modern samples consisted of modern Finns and the medieval samples were from archaeological collections in Sweden and Britain. The results show that the shape and size of the 4th lumbar vertebra has changed significantly from medieval times in a way that markedly affects the biomechanical characteristics of the lumbar vertebral column. These changes may have influenced the incidence of trauma- induced spinal fractures in modern populations.

Application of the anatomical method to estimate the maximum adult stature and the age‐at‐death stature

This study focuses on the age adjustment of statures estimated with the anatomical method. The research material includes 127 individuals from the Terry Collection. The cadaveric stature (CSTA)-skeletal height (SKH) ratios indicate that stature loss with age commences before SKH reduction. Testing three equations to estimate CSTA at the age at death and CSTA corrected to maximum stature from SKH indicates that the age correction of stature should reflect the pattern of age-related stature loss to minimize estimation error. An equation that includes a continuous and linear age correction through the entire adult age range [Eq. (1)] results in curvilinear stature estimation error. This curvilinear stature estimation error can be largely avoided by applying a second linear equation [Eq. (2)] to only individuals older than 40 years. Our third equation [Eq. (3)], based on younger individuals who have not lost stature, can be used to estimate maximum stature. This equation can also be applied to individuals of unknown or highly uncertain age, because it provides reasonably accurate estimates until about 60/70 years at least for males.

Error quantification of osteometric data in forensic anthropology

This study evaluates the reliability of osteometric data commonly used in forensic case analyses, with specific reference to the measurements in Data Collection Procedures 2.0 (DCP 2.0). Four observers took a set of 99 measurements four times on a sample of 50 skeletons (each measurement was taken 200 times by each observer). Two-way mixed ANOVAs and repeated measures ANOVAs with pairwise comparisons were used to examine interobserver (between-subjects) and intraobserver (within-subjects) variability. Relative technical error of measurement (TEM) was calculated for measurements with significant ANOVA results to examine the error among a single observer repeating a measurement multiple times (e.g. repeatability or intraobserver error), as well as the variability between multiple observers (interobserver error). Two general trends emerged from these analyses: (1) maximum lengths and breadths have the lowest error across the board (TEM<0.5), and (2) maximum and minimum diameters at midshaft are more reliable than their positionally-dependent counterparts (i.e. sagittal, vertical, transverse, dorso-volar). Therefore, maxima and minima are specified for all midshaft measurements in DCP 2.0. Twenty-two measurements were flagged for excessive variability (either interobserver, intraobserver, or both); 15 of these measurements were part of the standard set of measurements in Data Collection Procedures for Forensic Skeletal Material, 3rd edition. Each measurement was examined carefully to determine the likely source of the error (e.g. data input, instrumentation, observers method, or measurement definition). For several measurements (e.g. anterior sacral breadth, distal epiphyseal breadth of the tibia) only one observer differed significantly from the remaining observers, indicating a likely problem with the measurement definition as interpreted by that observer; these definitions were clarified in DCP 2.0 to eliminate this confusion. Other measurements were taken from landmarks that are difficult to locate consistently (e.g. pubis length, ischium length); these measurements were omitted from DCP 2.0. This manual is available for free download online (https://fac.utk.edu/wp-content/uploads/2016/03/DCP20_webversion.pdf), along with an accompanying instructional video (https://www.youtube.com/watch?v=BtkLFl3vim4).

Age-related trends in vertebral dimensions.

Several studies have demonstrated age‐related changes in vertebral dimensions. Vertebral size has been reported to increase among elderly adults, with periosteal apposition resulting in increased cross‐sectional area (CSA) of the vertebral corpus combined with reduction in bone mineral density. These changes in CSA are observed to be sex‐specific, as the pronounced increase of vertebral CSA is found only in elderly males. However, the reduction in bone mineral density in old age is apparent within both sexes. It is thus hypothesized that higher fracture risk in elderly women is a result of their incapacity to increase vertebral size and thus adapt to bone mineral reduction. In this study, our aim was to explore whether the onset of these changes could be ascribed to specific age intervals and whether the proposed differences between the sexes are as great as previously suggested. To conduct this study we utilized two large early 20th century skeletal collections known as Terry and Bass (n = 181). We also utilized data from two lumbar spine magnetic resonance imaging samples as a modern‐day reference (n = 497). Age, sex and ethnicity of all individuals were known. Vertebral CSA was determined by measuring three width and length dimensions from the corpus of the fourth lumbar vertebra (L4). Our results indicate only a moderate association between age and vertebral CSA. This association was observed to be relatively similar in both sexes, and we thus conclude that there is no clear sex‐specific compensatory mechanism for age‐related bone loss in vertebral size.

Data for validation of osteometric methods in forensic anthropology

Many techniques in forensic anthropology employ osteometric data, although little work has been done to investigate the intrinsic error in these measurements. These data were collected to quantify the reliability of osteometric data used in forensic anthropology research and case analyses. Osteometric data (n = 99 measurements) were collected on a random sample of William M. Bass Donated Collection skeletons (n = 50 skeletons). Four observers measured the left elements of 50 skeletons. After the complete dataset of 99 measurements was collected on each of the 50 skeletons, each observer repeated the process for a total of four rounds. The raw data is available on Mendeley Data (DCP Osteometric Data, Version 1. DOI: 10.17632/6xwhzs2w38.1). An example of the data analyses performed to evaluate and quantify observer error is provided for the variable GOL (maximum cranial length); these analyses were performed on each of the 99 measurements. Two-way mixed ANOVAs and repeated measures ANOVAs with pairwise comparisons were run to examine intraobserver and interobserver error, and relative and absolute technical error of measurement (TEM) was calculated to quantify the observer variation. This data analysis supported the dissemination of a free laboratory manual of revised osteometric definitions (Data Collection Procedures 2.0[1], pdf available at https://fac.utk.edu/wp-content/uploads/2016/03/DCP20_webversion.pdf) and an accompanying instructional video (https://www.youtube.com/watch?v=BtkLFl3vim4). This manual is versioned and updatable as new information becomes available. Similar validations of scientific data used in forensic methods would support the ongoing effort to establish valid and reliable methods and protocols for proficiency testing, training, and certification.

The effect of age and body composition on body mass estimation of males using the stature/bi-iliac method

The stature/bi-iliac breadth method provides reasonably precise, skeletal frame size (SFS) based body mass (BM) estimations across adults as a whole. In this study, we examine the potential effects of age changes in anthropometric dimensions on the estimation accuracy of SFS-based body mass estimation. We use anthropometric data from the literature and our own skeletal data from two osteological collections to study effects of age on stature, bi-iliac breadth, body mass, and body composition, as they are major components behind body size and body size estimations. We focus on males, as relevant longitudinal data are based on male study samples. As a general rule, lean body mass (LBM) increases through adolescence and early adulthood until people are aged in their 30s or 40s, and starts to decline in the late 40s or early 50s. Fat mass (FM) tends to increase until the mid-50s and declines thereafter, but in more mobile traditional societies it may decline throughout adult life. Because BM is the sum of LBM and FM, it exhibits a curvilinear age-related pattern in all societies. Skeletal frame size is based on stature and bi-iliac breadth, and both of those dimensions are affected by age. Skeletal frame size based body mass estimation tends to increase throughout adult life in both skeletal and anthropometric samples because an age-related increase in bi-iliac breadth more than compensates for an age-related stature decline commencing in the 30s or 40s. Combined with the above-mentioned curvilinear BM change, this results in curvilinear estimation bias. However, for simulations involving low to moderate percent body fat, the stature/bi-iliac method works well in predicting body mass in younger and middle-aged adults. Such conditions are likely to have applied to most human paleontological and archaeological samples.

Analysis of Three Commonly Used Tibia Length Measurement Techniques

This study analyzes three tibia length measurement techniques on a sample of 107 tibiae. Two of the techniques meet published criteria by resting the tibia on its posterior surface with the longitudinal axis parallel to an osteometric board. The third technique does not adequately keep the longitudinal axis parallel to the board. Statistical analyses show low levels of interobserver error for all techniques and statistically significant differences between the third technique and the other two techniques. Results report a maximum difference of 6 mm between measurement techniques with the third technique having greater than 95% directional bias. A survey sent out to the American Academy of Forensic Sciences forensic anthropology community reported more than 50% of respondents having been taught the third technique when an osteometric board with a slot/hole is not available. The intermixing of the third technique with the other two has likely contributed to higher levels of interobserver error in tibia length measurements.

Reanalysis of the Trotter Tibia Quandary and its Continued Effect on Stature Estimation of Past-Conflict Service Members

Forensic casework from past‐conflicts relies on the corrected historical Trotter data for stature estimation in Fordisc. For roughly 10 years’, stature estimation using this data has produced point estimates for the tibia that are on average 1.25 inches less than the other long bones. This issue was identified after applying the equations derived from Fordisc to the USS Oklahoma commingled assemblage. Reevaluation of Fordisc revealed that a correction factor of 20 mm, instead of 10 mm, was mistakenly applied to the Trotter tibia data. Historical forensic anthropology reports written at the Defense POW/MIA Accounting Agency were utilized to identify that the overcorrection is isolated to Fordisc 3 with an error rate of 5% of known antemortem statures falling outside of the prediction intervals that relied on the tibia. Further evaluation of the Oklahoma sample indicates the 10 mm correction is still producing point estimates less than the other long bones.