Quantitative Evaluation of Experimental Bone Regeneration Using Indentation Tests

OBJECTIVES To determine whether the macroindentation test can be applied to quantitatively assess bone regeneration. METHODS A 3.2 mm diameter transverse monocortical defect was created on the medial aspect of both proximal metaphyses of the tibia of male Unib-WH rats. For the macroindentation tests, we used 5.00 mm diameter indenters with a 3.2 mm tip. Defect testing was performed 1 to 12 weeks following the surgical procedures to compare the hardness of the newly developed tissue over the 12-week study period. Additional histological, morphological and physical/chemical data were obtained by optical and electronic microscopy, Raman, and energy dispersive x-ray spectrometry (EDS). RESULTS The mean indentation forces increased in a time-dependent manner from 4 to 12 weeks (p<0.001). Tests performed with the 5.0 mm diameter tip were not able to measure the indentation forces in the first week after the procedure. Moreover, in the second postoperative week indentation forces and the newly formed tissue within the spinal canal were greater than those measured in the fourth and eighth weeks. CONCLUSIONS The macroindentation test can be used to quantitatively assess bone regeneration in experimental studies. The choice of indenter tip diameter should consider the study design. Level of Evidence II, Diagnostic Studies.