Biochemical serum markers of osteoblastic activity and collagen turnover were measured in a sheep model of distraction osteogenesis. Significant increases of the bone formation marker osteocalcin were found during the first part of the consolidation phase and peaked at a time point equalling the distraction phase. Collagen turnover parameters pyridinoline and the specific type I collagen marker desoxypyridinoline consistently increased during the distraction and consolidation phases. While pyridinoline peaked at a time point similar to osteocalcin, desoxypyridinoline increased to a later stage in consolidation, indicating continuous turnover of bone-specific type I collagen. The results indicate a characteristic pattern of osteoblast cellular activation during distraction osteogenesis with possible consequences for the timing of treatment.

The present article describes a newly developed device for the quantitative assessment of torsional in vivo stiffness of regenerating bone under callus distraction. Both the design and function of this device, and its use during bony consolidation are discussed. The device exhibited an accuracy of +/- 18% for stiffness under 0.1 Nm/degree, and +/- 5% stiffness above 0.1 Nm/degree. The average accuracy was +/- 14%. The data scatter for the stiffness measurement ranged between +/- 1.43% and +/- 7.68% (average: +/- 3.99%). The precision of a test machine was between +/- 0.01% and +/- 11.3% (average: +/- 3.65%). The method has the following advantages over existing methods for investigating healing: 1. no need to dismantle the external fixation for measurement; 2. preservation of the bone axis with minimal risk of misalignment during the bone healing process; 3. minimal technical requirements, with easy, noninvasive measurement; 4. no exposure to X-radiation.

The present article describes a newly developed device for the quantitative assessment of torsional in vivo stiffness of regenerating bone under callus distraction. Both the design and function of this device, and its use during bony consolidation are discussed. The device exhibited an accuracy of ± 18 % for stiffness under 0.1 Nm/°, and ± 5 % stiffness above 0.1 Nm/°. The average accuracy was ± 14 %. The data scatter for the stiffness measurement ranged between ± 1.43 % and ± 7.68 % (average: ± 3.99 %). The precision of a test machine was between ± 0.01 % and ± 11.3 % (average: ±3.65 %). The method has the following advantages over existing methods for investigating healing: 1. no need to dismantle the external fixation for measurement; 2. preservation of the bone axis with minimal risk of misalignment during the bone healing process; 3. minimal technical requirements, with easy, noninvasive measurement; 4. no exposure to X-radiation.