An examination of histomorphometric relationships in the anterior and posterior human femoral cortex.

INTRODUCTION: Static cortical bone histomorphometry utilised in forensic age-at-death estimation generally examines only the anterior femoral mid-shaft, as biomechanical strain at the posterior femur is thought to result in increased bone remodelling, osteon density and adversely affect age-at-death estimates. As osteon density increases there is a corresponding decrease in geometric variables, such as osteon area and Haversian canal diameter. The present study tests whether the inverse relationship between osteon density and osteon geometry is reflected in a modern documented Australian sample, and if this relationship differs between the anterior and posterior femoral mid-shaft. MATERIALS AND METHODS: The study sample comprises 215 femoral microradiographs (117♂ 98♀) of recorded age (18‒97 years) from the Melbourne Femur Reference Collection (MFRC). The following variables were measured in Image J across six 1 mm2 regions of interest (ROIs) from the anterior and posterior; mean intact and fragmentary secondary osteon count, osteon population density, osteon and Haversian canal area, perimeter, and diameter. RESULTS: Osteon area was positively correlated with Haversian canal size and shape metrics, and negatively correlated with osteon density. Chronological age was significantly correlated with most variables. There were significant between-group effects between the youngest (18‒34 years) and all other age groups (35‒49, 50-74 and 75 + years) for both regions. CONCLUSION: Our findings support an increased rate of remodelling associated with decreases in osteon geometry in the anterior and posterior femur. Future studies should examine static osteon histomorphometry using anterior and posterior measurements in larger samples of documented age and sex.

Femoral histomorphometric age-at-death studies: The issue of sample size and standard error.

Extant histomorphometric aging methods based on the analysis of the femoral cortex generally report small samples (N<100) and highly variable standard error of the estimate (SEE) values (±1.51‒16.98 years). The present paper reviews the published literature on femoral histomorphometry for age-at-death estimation in order to examine the relationship between sample size and SEE values, and makes recommendations for minimum reporting requirements for age-at-death studies based on statistical data. The SEE from a total of 33 studies are analysed. Sample size and confidence intervals are explored using Hennig and Cooper's simulation modelling. Analysis of effect size through a fixed-effect model is performed on 5/33 studies to examine the relationship between sample size and effect size. The pooled sex formulae from Nor et al., Martrille et al. and Thompson and the two sex-specific formulae of Pfeiffer are examined, as they report mean and standard deviation values for both chronological and estimated ages. The results of these analyses support sampling theory, specifically wide variation in SEE when N<100, narrowing as the sample size increases, and lower effect sizes in the larger of the five studies examined. The findings provide some support for a minimum threshold of 100‒150 individuals for histomorphometric age-at-death estimation. Analysis of effect size is suggested for future investigation in meta-analyses of forensic anthropological age-estimation studies. To ensure increased precision and meaningful comparison, large samples should be used for histomorphometry, and authors should report SEE and discrete statistics (e.g. n, mean, standard deviation) for both chronological age and estimated age.

Histomorphometric age estimation from the femoral cortex: A test of three methods in an Australian population.

Histological methods can be used forensically to estimate age-at-death based on patterns of change in osteon shape, size, and population density, all of which result from the continuous process of bone remodelling. The present study examines the applicability of three existing histological age-at-death estimation methods as applied to an Australian population of known age and sex. Microradiographs from 50 mid-shaft femora thin sections, equally divided by sex, were obtained from the Melbourne Femur Reference Collection (MFRC); stated chronological age-at-death is 18 to 88 years. Osteon shape metrics are measured using ImageJ and the age-at-death prediction formulae of i) Singh and Gunberg, ii) Keough et al., and iii) Goliath et al. are applied. The relationship between estimated and actual age-at-death is then statistically quantified. All three formulae demonstrate pooled and sex-specific SEE values in excess of 20 years: i) pooled ±22.92 (♂±20.91, ♀±25.20); ii) ±20.79 (♂±20.96, ♀±21.05); and iii) ±35.43 (♂±32.68, ♀±38.66). When individuals under 40 years of age were excluded from the analysis, only two of the methods demonstrated increased accuracy: i) pooled ±20.87 (♂ ±17.47, ♀ ±23.70); ii) pooled ±18.21 (♂±16.51, ♀±19.90); and iii) pooled ±41.18 (♂ ±40.12, ♀ 43.05). The present study represents a preliminary investigation of the accuracy of existing histological age-at-death standards applied in an Australian population of known age.

Skeletal age estimation in a contemporary Western Australian population using the Tanner-Whitehouse method.

Various age estimation techniques have been utilised in Australia to evaluate the age of individuals who do not have documentation to determine legal majority/culpability. These age estimation techniques rely on the assessment of skeletal development as visualised in radiographs, CT scans, MRI or ultrasound modalities, and subsequent comparison to reference standards. These standards are not always population specific and are thus known to be less accurate when applied outside of the original reference sample, leading to potential ethical implications. Therefore, the present study aims to: (i) explore the variation in developmental trajectories between the established Tanner-Whitehouse (TW) age estimation standards and a Western Australian population; and (ii) develop specific hand-wrist age estimation standards for the latter population. The present study examines digital anterior-posterior hand-wrist radiographs of 360 individuals 0 to 24.9 years of age, equally represented by sex. Each radiograph was assessed using the RUS, Carpal and 20-bone methods of Tanner et al. The standard error of the estimate (SEE) was calculated for each method (range: ♀ SEE ±0.4-11.5 years; ♂ SEE ±0.9-10.1 years). The most accurate method was TW3 RUS for females and the TW2 Carpal system for males. The 50th centile skeletal maturity scores for each year age group were plotted against average chronological age to produce polynomial regression standards with a demonstrated accuracy of (♀ SEE ±0.09-3.46 years; ♂ SEE ±0.02-3.42 years) for females and males, respectively. The standards presented here can be used in future forensic investigations that require age estimation of hand-wrist bones in a Western Australian population, however, they are not appropriate for establishing age of majority (18 years), as skeletal maturity was attained on average earlier than 15 years of age in both sexes for all three systems examined.