The time independent material behavior of cylindrical specimens obtained from the cancelous bone of 20 cadaveric human femora were determined. In this part of the publication, the nominal values for compressive strength, limits of elasticity (yield point), strain, elastic modulus and apparent density are being reported for the cancellous bone of the femoral head and condyle. The correlations between the various parameters are analysed. A positive linear correlation between the four parameters compressive stength, limit of elasticity, modulus of elasticity and apparent density could not be excluded. The material properties vary considerably both within one single bone and between individuals. Compressive strength, modulus of elasticity and apparent density found for cancellous bone of the femoral head are greater than those found in the condyles. Within the condyles, compressive strength, elastic modulus and apparent density increase from the proximal parts to the parts closer to the joint. The medial femoral condyle showed higher compressive strength than the lateral one. Relating each of the three other parameters to the apparent density of the individual specimen did not result in equalizing the data for the material properties. This indicates that the mechanical properties of cancellous bone are strongly related to the direction of loading.

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Following a survey of the literature regarding clinical examinations and experimental studies of local absorbable carrier for an antibiotic in treatment of osteitis, a study is presented concerning clinical experience with 46 patients treated with a cefotaxim-loaded fibrin sealant. In connection with simultaneous focal sanitation the clinical results were satisfying. When autogenous cancellous bone was added at the same time, only one surgical operation was necessary in some cases to show results equivalent to other methods. Postoperatively, the cefotaxim levels in the blood and in the wound drainage fluid were measured. The serum cefotaxim concentrations were low and only identifiable for a period of 36h, whereas the wound drainage fluid contained very highly effective antibacterial concentrations over a measured period of 3.5 days. The best results were seen in cases of hematogenic osteomyelitis. The disadvantage of this system is the quick release of the antibiotic by diffusion. Therefore, high concentrations can be obtained only for a short period of several days.

In part I of this communication we reported on some time independent material properties of cancellous bone specimens from different regions of human femora. In part II we will report on our investigations of the time dependent behaviour, i.e. stress relaxation and creep. Cylindrical specimens were obtained from the head and condyles of pairs of cadaveric femora and subjected to axial loading. The data were evaluated statistically. The medianL values for relaxation of cancellous bone were greater in the femoral head than in the condyles, greater proximally than distally and greater medially than laterally in the condyles. The distribution of creep was found to be the reverse. The correlation analysis showed that a linear correlation between compressive strength, apparent density and the time dependent properties cannot be assumed. The time dependent properties reported here would appear to demonstrate the visco-elastic behaviour of cancellous bone. An experimental foundation and explanation is presented for the clinical practice of re-tightening cancellous bone screws one time only.

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