Novel Approach to calculate Callus Distraction Forces in Distraction Osteogenesis and Application in the Human Tibia

Objectives Distraction osteogenesis (DO) of long trabecular bones is clinically performed with different procedures and implants. However, boundary conditions such as arising forces during distraction are mainly based on empirical values. The aim was to use a mathematical model to calculate the callus distraction force (CDF) as a parameter of such a surgical procedure. Our novel approach enables the estimation of necessary parameters and facilitates an approximation of the arising CDF in different localizations along the bone axis during DO.

Methods We adapted and implemented an existing biomechanical model based on a sheep experiment (Meyers et al., 2018) in Matlab 2019b (Mathworks Inc., Natick, MA, USA) to calculate forces arising while distracting callus tissue. For the evaluation we chose an exemplary human tibia with average length (l= 402 mm, male, age 45). Subsequently, a volumetric model of this adult tibia was created by segmentation of CT data with ImFusion Suite (ImFusion GmbH, Munich, Germany) and modelling in Catia V5R19 (Dassault Systèmes, Vélizy-Villacoublay, France) ([Fig. 1]). The 3D bone model was separated into four parts of equal length and the distraction area was determined using the respective bone cross section (proximal, central, distal) by means of Inventor 2020 (Autodesk Inc., San Rafael, CA, USA) ([Fig. 1b]). Based on the distraction area, the CDF was calculated with the implemented mathematical model for each location utilizing clinically established distraction parameters (1 mm distraction/day in three steps) and a distraction length of 5 cm.

Results and Conclusion Our results show a non-linear increase of the CDF throughout the whole distraction period for all three locations. The peak CDF rises from 0.97 N to 104 N at the proximal location ([Fig. 1]), from 0.56 N to 59.9 N at the central location, and from 0.52 N to 55.5 N at the distal location. Furthermore, an increase of the CDF after relaxation and prior to distraction from 0.0033 N to 30.7 N at the proximal location ([Fig. 1c]), from 0.0019 N to 17.7 N at the central location, and from 0.0018 N to 16.4 N at the distal location can be observed.

We conclude that the CDF rises in a non-linear manner during the distraction period and is strongly dependent on the distraction location along the bone axis. We intend to evaluate further human tibiae to increase the statistical significance and compare the results to previously published forces measured in vivo. These data may be used to optimize DO procedures. Our modelling approach is based on data obtained by an animal experiment. Hence, parameters like patient age or biological influences (e.g. blood supply) should be considered in the future.

Fig. 1 Workflow to obtain the Callus Distraction Force (CDF) for indicated locations along the tibia shaft axis. The graph displays the progression of the CDF for each distraction step at the proximal location for a distraction period of 50 days.

Stichwörter Distraction osteogenesis, Bone Lengthening, Bone Transport, Distraction Force, Biomechanical Modelling

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Artikel online veröffentlicht:
15. Oktober 2020