In situ formation of porous space maintainers in a composite tissue defect

Abstract

Reconstruction of composite defects involving bone and soft tissue presents a significant clinical challenge. In the craniofacial complex, reconstruction of the soft and hard tissues is critical for both functional and aesthetic outcomes. Constructs for space maintenance provide a template for soft tissue regeneration, priming the wound bed for a definitive repair of the bone tissue with greater success. However, materials used clinically for space maintenance are subject to poor soft tissue integration, which can result in wound dehiscence. Porous materials in space maintenance applications have been previously shown to support soft tissue integration and to allow for drug release from the implant to further prepare the wound bed for definitive repair. This study evaluated solid and low porosity (16.9% ± 4.1%) polymethylmethacrylate space maintainers fabricated intraoperatively and implanted in a composite rabbit mandibular defect model for 12 weeks. The data analyses showed no difference in the solid and porous groups both histologically, evaluating the inflammatory response at the interface and within the pores of the implants, and grossly, observing the healing of the soft tissue defect over the implant. These results demonstrate the potential of porous polymethylmethacrylate implants formed in situ for space maintenance in the craniofacial complex, which may have implications in the potential delivery of therapeutic drugs to prime the wound site for a definitive bone repair.

Figure 1

Schematic (A) and photograph (B) of defect in rabbit mandible (Scale bars indicate 10 mm and 5 mm, respectively). Photograph (C) of rabbit mandibular defect filled with a porous implant (Scale bar indicates 5 mm).

Figure 2

Photographs of the oral mucosa over the composite defect for (A) a well-healed porous implant and (B) a poorly healed, exposed solid implant after 12 weeks of implantation. The black arrow indicates implant exposure.

Figure 3

Number of implants with healed and non-healed oral mucosa for solid and porous implants after 12 weeks of implantation (n=10 for each group).

Figure 4

Representative images (1000 μm scale bar) from (A) the solid implant group and (B) the porous implant group with higher magnifications, highlighted in yellow, (200 μm scale bar) of each (C) and (D), respectively. Histologic scores were made using magnifications shown in images (A-D). Additional higher magnification images of (C) and (D), highlighted in yellow, are shown in (E) and (F), respectively (50 μm scale bar). The solid implant shown was scored as a 1 according to Table 1, as an unorganized fibrous capsule was present around the majority of the implant (A and C). The porous implant shown was scored as a 2 due to the presence of an organized fibrous capsule, based on the magnifications shown in (B and D). Black arrows show the titanium plate. Red arrow indicates dehiscence.

Figure 5

Histologic scores of the inflammatory response at the tissue-implant interface of solid and porous implants. There was not a significant difference between the solid and porous groups as determined by the Mann-Whitney U test.

Figure 6

Histologic scores of the tissue within the pores of the porous implants.