The intraindividual agreement of the bone density of the human proximal tibia

The interindividual variability in the biomechanical properties of cadaver bones has remained an unsolved problem in biomechanical investigation procedures. For this reason, it is postulated to use matched bone pairs from the same individual for comparative biomechanical tests. The rationale behind this procedure is based on the assumption that biomechanically similar behaviour is to be expected in an intraindividual rather than an interindividual comparison. Systematic studies confirming this thesis were performed on the human femur. However, investigations regarding the intraindividual properties of the proximal tibial metaphysis with respect to the underlying bone densities, have not yet been performed. In order to verify the hypothesis that matched proximal tibial metaphyses from the same donor imply corresponding bone density values, densitometric measurements (pQCT) were performed in 14 matched cadaver tibias (average age 61 years, 9 men, 5 women) which were fresh-frozen at -40 degrees C after removal. After statistical analysis of the bone density values, five tibial pairs were identified as differing on the basis of missing correlations and the existence of systematic differences within the pairwise data. In other words, only about 2/3 of the data in the random sample available was classified as comparable. As the bone density measured by pQCT technique significantly correlates with the biomechanical properties of the bone, it can be concluded from the test result available that matched human tibiae show no concurring bone density values in 1/3 of cases. Thus the pairing of corpse tibiae does not necessarily imply suitability for comparative biomechanical experiments.