Erfassung der Knochenheilung während der Kallusdistraktion durch ein automatisiertes torsionales Steifigkeitsmeßsystem - Assessment of Bone Healing under Callus Distraction using an automatic Torsional Stiffness Metering System

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 stiff ness under 0.1 Nm/degrees, and +/- 5 % stiff ness above 0.1 Nm/degrees. 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.