Distraction osteogenesis (DO) is a well-established technique for treating facial gunshot wounds, since this type of injury requires the reconstruction of bone and soft tissue (Labbé et al., 1998; Bildstein et al., 2021). DO is also the only technique that allows the surgeon to recreate the alveolar ridge with its attached gum, which plays a strong role in the success rate of dental reconstruction with osteointegrated implants (Labbé et al., 2001).

This surgical procedure involves the progressive lengthening of a bone segment (1 mm/day). The technique requires the implantation of a distractor device (internal or external), which is activated daily for the lengthening of the bone and soft tissue.

Previously we reported our experience of DO using a customized external device (DEOS) with an endless screw. This bidirectional device was successfully used thanks to computer-assisted planning of distraction osteogenesis for lower face reconstruction in gunshot traumas (Benateau et al., 2016). However, activation of the device may be responsible for multiple adverse events and discomfort (Verlinden et al., 2015), which may be due to mishandling by the patient or a family member (Bonnet et al., 2012) .To overcome these issues, new generations of distractor devices, such as automated distractors, have been proposed (Ayoub et al., 2005), but these are currently not suitable for clinical practice (Goldwaser et al., 2012; Saman et al., 2013; Boisson et al., 2016).

Despite the increasing use of DO and the development of new devices in the field of DO, the role of the surrounding soft tissue in the mechanical load opposing the distraction vector is not currently understood. The forces involved in the process have not yet been precisely determined, while they are essential to the development of new-generation distraction devices, reducing adverse events, and allowing easier-to-manage treatment protocols.

Determining the overall stiffness of soft tissue involved in mandibular distraction is crucial in the mechanical design of continuous automated distraction devices. Goldwaser (Goldwaser et al., 2012) identified the following key features of a clinically useful distraction device, whether continuous/discontinuous, or automated/manual: sufficient force generation and maintenance; ability to measure the force used; robust enough to withstand in vivo environments.

Although distraction osteogenesis of the mandible is well reported in the literature, no study has been published describing the direct measurement of the soft-tissue resisting force during human mandible distraction.

The purpose of our study was to characterize the mechanical behavior of soft tissue elongated during distraction, using fresh human cadaveric specimens, in order to better understand possible causes of adverse events and pave the way for the design of next-generation automated distraction devices.