Evaluation of an intramedullary bone stabilization system using a light‐curable monomer in sheep

Abstract

Percutaneous intramedullary fixation may provide an ideal method for stabilization of bone fractures, while avoiding the need for large tissue dissections. Tibiae in 18 sheep were treated with an intramedullary photodynamic bone stabilization system (PBSS) comprised of a polyethylene terephthalate (Dacron) balloon filled with a monomer and cured with visible light in situ then harvested at 30, 90 or 180 days. In an additional 40 sheep, a mid-shaft tibial osteotomy was performed and stabilized with external fixators or external fixators combined with the PBSS and evaluated at 8, 12 and 26 weeks. Healing and biocompatibility were evaluated by radiographic analysis, microCT and/or histopathology. In non-fractured sheep tibiae, PBSS implants conformably filled the medullary canal, while active cortical bone remodeling and apposition of new periosteal and/or endosteal bone was observed with no significant macroscopic or microscopic observations. Fractured sheep tibiae exhibited increased bone formation inside the osteotomy gap with no significant difference when fixation was augmented by PBSS implants. Periosteal callus size gradually decreased over time and was similar in both treatment groups. No inhibition of endosteal bone remodeling or vascularization was observed with PBSS implants. Intramedullary application of a light curable PBSS is a biocompatible, feasible method for fracture fixation.

A Biomechanical Comparison of a Novel Expandable Photodynamic Intramedullary System to a Metal Plate and Screw System in Humerus and Femur Osteotomy Models

“…3,4,6 A recently developed Intramedullary system (IS) that utilizes a photodynamic monomer offers the potential to completely fill the intramedullary canal and provide better stabilization of a fracture or an osteotomy. 7,8 The implantation process begins with clearance of the soft tissue of the medullary canal by a flexible, cannulated, drill bit guided by a wire. 7,8 An angioplasty-like balloon adapted for this system is then inserted down the canal and filled with a liquid photodynamic monomer until the balloon is expanded and conforms to the inner cortical walls.…”

“…7,8 The implantation process begins with clearance of the soft tissue of the medullary canal by a flexible, cannulated, drill bit guided by a wire. 7,8 An angioplasty-like balloon adapted for this system is then inserted down the canal and filled with a liquid photodynamic monomer until the balloon is expanded and conforms to the inner cortical walls. 7,8 Finally, an optical fiber inserted down the cannulated balloon delivers visible blue light (436 nm) to polymerize the liquid monomer and thus hardening the implant.…”

“…7,8 An angioplasty-like balloon adapted for this system is then inserted down the canal and filled with a liquid photodynamic monomer until the balloon is expanded and conforms to the inner cortical walls. 7,8 Finally, an optical fiber inserted down the cannulated balloon delivers visible blue light (436 nm) to polymerize the liquid monomer and thus hardening the implant. 7,8 Each implant is expandable to ensure a conformal fit between the implant and the canal and could potentially offer improved biomechanics.…”

“…7,8 Finally, an optical fiber inserted down the cannulated balloon delivers visible blue light (436 nm) to polymerize the liquid monomer and thus hardening the implant. 7,8 Each implant is expandable to ensure a conformal fit between the implant and the canal and could potentially offer improved biomechanics. This technology has shown promising results in a large animal model and in clinical use.…”

“…12,13 For the femur, three IS diameter sizes (13 mm, 15 mm, 17 mm) were compared to a 4.5 mm Locking Compression Plate (LCP) and screw system. [7][8][9] Using a bone surrogate model we evaluated these implants using biomechanical parameters: stiffness, yield load, peak load, yield displacement, peak displacement, and finally cycles to failure under axial load. [5][6][7][8][9][10]14 In both models, previous biomechanical testing of plates and intramedullary rods provided a suitable predicate.…”