A comparison of three decalcification agents for assessments of cranial fracture histomorphology

Abstract

The extraction of mineral calcium from bone by decalcification is a critical step in the preparation of histological samples for light microscopy. This study assessed the time required for complete decalcification and the resultant histomorphological preservation of bone histomorphology by three decalcification agents: 7% hydrochloric acid (HCl), 5% nitric acid, and 10% ethylenediaminetetraacetic acid (EDTA). The goal of this study was to identify which decalcification agent provides the optimal combination of expedient processing and quality histological outcomes of cranial fracture samples. HCl provided the most rapid decalcification ( $\overline{X}$ = 3.57 days), nitric acid followed closely ( $\overline{X}$ = 10.35 days), while EDTA took significantly longer on average ( $\overline{X}$ = 78.97 days) but encompassed a broader range of times. Decalcification agent, sample thickness, sample width, and decedent age are significant predictors of decalcification time. Sample visualization quality, measured for tissues, cells, and nuclei on a five-point Likert scale, was highest for samples decalcified in 10% EDTA, second highest using 5% nitric acid, and lowest for 7% HCl. The quality difference between EDTA and nitric acid was not highly significant for any of the three features. For basic assessments of bone histomorphology, the study results indicate 5% nitric acid is suitable for the decalcification of adult specimens and samples thicker than 3 mm. EDTA is a suitable agent for thin samples of the cranial vault (<3 mm) from infants and young children less than three years old, decalcifying samples in a timeframe comparable to nitric acid while providing the best quality and clarity of samples.

Keywords: EDTA; bone histology; decalcification; forensic anthropology; forensic pathology; hydrochloric acid; nitric acid; preservation; quality.