Two-laboratory comparability of apparent elastic modulus measurements in bovine lumbar vertebral trabecular bone under a standardized compression protocol.

Interlaboratory comparability of trabecular bone mechanical properties is important for experimental biomechanics and density-based material assignment, but destructive testing prevents repeated measurement of the same specimen. We evaluated the comparability of apparent elastic modulus measurements obtained through two laboratory pathways using adjacent bovine lumbar vertebral trabecular bone specimens and a standardized compression protocol. Forty-eight specimens from six animals formed 24 adjacent pairs (12 longitudinal, 12 transverse). Specimens had an aspect ratio close to five, were kept hydrated, preconditioned to 0.5 % strain and compressed at 0.5 %/s after testing-system compliance correction. SGU specimens were tested on the day of preparation; paired PNIPU specimens underwent wet transport and next-day testing. Apparent modulus was calculated over 0.2-0.8 % strain. Animal-level analysis yielded a pooled mean paired pathway difference of + 0.4 % (95 % CI - 2.7 % to + 3.6 %; six animals), with pair-level Bland-Altman limits of - 14.2 % to + 17.5 %. Mean modulus was 819.9 ± 155.0 MPa longitudinally and 227.7 ± 52.0 MPa transversely. No detectable protocol-arm shift was observed in the ash-density-modulus relationship. Under the standardized practical protocol, mean modulus measurements were comparable across the two tested laboratory pathways. The limits of agreement quantify the total pair-level variability observed under this workflow and do not separate effects of local specimen heterogeneity, laboratory setting, transport, or testing delay.