Effect of a formalin-based fixation method on bone mineral content in human ex-vivo specimens

Abstract

Objective

Histopathology of formalin-fixated human ex-vivo specimens may be used as reference standard for evaluation of diagnostic index tests like CBCT or MRI. The aim was to estimate changes in bone mineral content (BMC) over time in human ex-vivo bone specimens fixated in a formalin-based solution for 24 h followed by storage in an alcohol-based medium for six months, assessed by dual-energy X-ray absorptiometry (DXA).

Methodology

Bone specimens (n = 19) from human ex-vivo mandibles donated for science were included. BMC was measured by DXA before fixation (D₀), after 24 h of immersion fixation in a formalin-based solution (D₁), and hereafter every 30 days (M₁-M₆) during storage in a 30% ethanol-based storage medium for 6 months. Changes in BMC from D₀ to D₁ and from D₀ to M₆ were calculated and mean change in BMC estimated.

Results

Mean change in BMC from D₀ to D₁ was −0.73% (95% CI −1.75%; 0.29%), and from D₀ to M₆ −1.19% (95% CI −2.14%; −0.23%).

Conclusions

No changes in BMC of ex-vivo human bone specimens were found after 24 h formalin-based immersion fixation. After six months storage in an ethanol-based medium, BMC mean loss of 1% was detected. In this range, changes in BMC are not clinically relevant.

Keywords:

• Reference standard
• bone mineral content
• DXA
• formalin fixation
• ex-vivo human specimen

Acknowledgements

The authors thank laboratory technician Jytte Utoft for her valuable help on handling the specimens and prof. Michael Vaeth for his statistical help and advice.

Disclosure statement

The authors report no conflicts of interest.