A novel 3D-printed implant system for mandibular reconstruction (IPS® MotionPlate) - a finite element analysis

After continuity resection of the jaw, free bony flaps are used for reconstruction. Despite implementation of a digital workflow and additively manufactured custom-made implants for flap fixation, plate complications such as bony non-union remain a clinical challenge. This is the first description of the finite element analysis of a novel 3D-printed implant system for mandibular reconstruction designed to overcome this limitation. Virtual surgical planning and patient-specific finite element analysis were performed in 12 cases requiring segmental mandibulotomy. The novel custom-made implants (IPS® MotionPlate), with spring elements, were virtually designed and tested in terms of interfragmentary motion and relative load capacity in comparison with a standard plate and its physical material limits. Significant differences were found between all tested motion directions and locations of the MotionPlate versus the standard plate, aside from tilt rotation at the anterior position (p = 0.09). With the MotionPlate separation of the interfragmentary motion increased by 0.05 mm, 0.01 mm, and 0.02 mm at the posterior, medial, and anterior segments, respectively. Shear of the intefragmentary motions rose by 0.04 mm, 0.05 mm, and 0.05 mm at posterior, medial, and anterior segments, respectively. Tilt of the interfragmentary motions increased by 0.36° at the posterior segment and 0.24° at the medial segment. Inclination of interfragmentary motions increased by 0.35°, 0.35°, and 0.36° at posterior, medial, and anterior segments, respectively. The MotionPlate resulted in higher stresses than the standard plate; however, no MotionPlate stress exceeded the combined maximum shear and von Mises stresses normalized to their material limits, with a median of 0.8 and a maximum of 0.95 (IQR 0.66-0.91). The novel implant system favors interfragmentary motion while simultaneously not raising the stresses above the material limits. These findings suggest that the included spring elements effectively modulate construct stiffness, avoiding excessive rigidity without compromising overall strength.