A Biomechanical Proof-of-Concept Study of Scaffold-Augmented Distraction Osteogenesis Using 3D-Printed Hyperelastic...

Distraction osteogenesis (DO) for limb lengthening often requires prolonged fixation while the regenerate consolidates. Adjuncts that improve the regenerate quality could reduce morbidity and treatment time. Hyperelastic Bone™ (HEB) is a 3D-printed hydroxyapatite (HA)/polylactic-co-glycolic acid (PLGA) scaffold, but its efficacy as an osteotomy-site adjunct during DO is unclear. After IACUC approval, rabbits underwent left tibial lengthening with a mini-rail external fixator distracted at 0.75 mm/day to 20% tibial length and received no scaffold (control), traditional Hyperelastic Bone™ (10% PLGA/90% HA), or a biphasic formulation (10% PLGA/70% HA/20% β-tricalcium phosphate [β-TCP]) placed subperiosteally at the osteotomy site. The contralateral tibiae served as references. After 8 weeks of consolidation, radiographs, micro-CT (prespecified endpoint: regenerate BMD), and torsional testing (prespecified endpoint: stiffness) were performed. Fourteen rabbits underwent attempted lengthening. Intraoperative fractures (n = 2) and fixation loss (n = 3) reduced complete terminal datasets to nine, all of which completed micro-CT and torsion testing. Radiographs confirmed regenerate formation. Regenerate BMD remained below contralateral values with controls being intermediate to the traditional and biphasic HEB formulations (60.5%, 63.8%, and 54.7% of contralateral, respectively). Despite no mineral density improvement, scaffold-treated regenerate demonstrated higher torsional stiffness and strength metrics, greatest with the biphasic formulation, with lower failure displacement and higher polar moment of inertia. Statement of Clinical Significance: A scaffold that improves functional regenerate performance could enable earlier safer weight bearing and device removal and reduce nonunion/refracture risk in DO.