The effects of embalming using a 4% formalin solution on the compressive mechanical properties of human cortical bone.
BACKGROUND
The use of formalin fixed bone tissue is often avoided because of its assumed influence on the mechanical properties of bone. Fixed bone tissue would minimise biological risks and eliminate preservation issues for long duration experimental tests. This study aimed to determine the short- and long-term effects of embalming, using a solution with 4% formalin concentration, on the mechanical properties of human cortical bone.


METHODS
Three-millimetre cylindrical specimens of human cortical bone were extracted from two femoral diaphyses and divided in four groups. The first group was used as control, the remaining three groups were left in the embalming solution for 48 h, 4 week, and 8 week, respectively. Compressive mechanical properties, hardness and ash density were assessed. The last was used to check the homogeneity among the four groups.


RESULTS
No significant differences were found among the four groups in yield stress, ultimate stress and hardness. The specimens stored for 8 week in the embalming solution had significant lower Young's modulus (-24%), higher yield strain (+20%) and ultimate strain (+53%) compared to the other groups.


CONCLUSIONS
On a short-term perspective, embalming did not affect the compressive mechanical properties, nor hardness of human cortical bone, whereas a long-term preservation (8 week) did significantly affect Young's modulus, yield strain and ultimate strain in compression. Preserving bone segments for up to 4 week in an embalming solution with low formalin concentration seems to be an interesting alternative when collecting and/or managing fresh or fresh-frozen bone segments for biomechanical experiments is not possible.
Ohman
Caroline
C
Laboratorio di Tecnologia Medica, Istituti Ortopedici Rizzoli, Bologna, Italy.
Dall'Ara
Enrico
E
Baleani
Massimiliano
M
Van Sint Jan
Serge
S
Viceconti
Marco
M
D015519:Bone Density / Q000187:drug effects; D019245:Compressive Strength / Q000187:drug effects*; D055119:Elastic Modulus / Q000187:drug effects; D004615:Embalming / Q000379:methods; D005269:Femur / Q000187:drug effects*; D005557:Formaldehyde; D006244:Hardness / Q000187:drug effects; D006801:Humans; D013314:Stress, Mechanical; D016707:Tissue Fixation / Q000379:methods
D005557:Formaldehyde