Achieving stomal continence with an ileal pouch and a percutaneous implant

Abstract

In this study, a soft-tissue-anchored, percutaneous port used as a mechanical continence-preserving valve in reservoir ileo- and urostomies was functionally and morphologically evaluated in eight dogs. During follow-up, the skin failed to attach to the implant, but the intestine inside the stoma port appeared to be attached to the mesh. After reaching adequate reservoir volume, the urostomies were rendered continent by attaching a lid to the implant. The experiments were ended at different time intervals due to implant-related adverse events. In only one case did the histological evaluation reveal integration at both the implant-intestine and implant-skin interfaces, with a low degree of inflammation and the absence of bacterial colonisation. In the remaining cases, integration was not obtained and instead mucosal downgrowth and biofilm formation were observed. The skin-implant junction was characterised by the absence of direct contact between the epidermis and the implant. Varying degrees of epidermal downgrowth, granulation tissue formation, inflammatory cell infiltration and bacterial growth and biofilm formation were prominent findings. In contrast, the subcutaneously located anchor part of the titanium port was well integrated and encapsulated by fibrous tissue. These results demonstrate the opportunity to achieve integration between a soft-tissue-anchored titanium port, skin and intestine. However, predictable long-term function could not be achieved in these animal models due to implant- and non-implant-related adverse events. Unless barriers at both the implant-skin and implant-intestine junctions are created, epidermal and mucosal downward migration and biofilm formation will jeopardise implant performance.

Fig. 1

A, B Configuration of the stoma port and surgical models used. A The stoma port consisted of a skin-penetrating cylinder with an outer diameter of 20–22.5 mm and a ring-shaped anchor measuring 33–35.5 mm in diameter. The perforation of the anchor ring allowed connective tissue ingrowth. A cylindrical titanium mesh (inner diameter, 15–17.5 mm; hexagonal openings, 1.5 mm wide; wire width, 0.3–0.46 mm) was enclosed by the cylinder and attached to the anchor. B The stoma model with the titanium stoma port installed in the abdominal wall, the anchor flange located in the abdominal musculature, and the cylinder penetrating the skin. The ileal outlet from a valveless reservoir ad modum Kock was passed through the port. In a later stage, either the ileum or a ureter was anastomosed to the base of the reservoir. C, D Photographs of the stoma port implanted in dogs. C Ileostomy model after 6 weeks (EBM12) and D urostomy model after 26 weeks showing slight granulation around the implant and retraction of the efferent segment (EBM18)

Fig. 2

A–N Qualitative and quantitative topographical and chemical characterisation of the stoma port with detailed analysis of the cylinder and mesh. A–D Scanning electron micrographs and surface microtopography of the cylinder. E–H Scanning electron micrographs and surface microtopography of and the mesh. Auger electron spectroscopy (AES) depth profiling of the cylinder (I) and mesh (J). K, L Energy dispersive X-ray analysis (EDX) of the cylinder showing the oxygen and aluminium content in the surface. M Table showing the oxide thickness, chemical composition of the surface and the result from the surface topography measurements. Sa: arithmetic mean deviation of the surface; Sdr: developed surface area ratio; Sci: surface core fluid retention index. N Image showing the cylinder top (left) and mesh (right) where chemical and topographical data were obtained

Fig. 3

A–C Light micrographs showing the integration between the intestine and the inner mesh and cylindrical surface of the titanium (Ti) port in an ileostomy model (EBM12, 9 weeks). A On the anti-mesenteric side, integration was observed between the external part of the intestine and the inside of the titanium cylinder and the mesh. The vascularised fibrous tissue (FT), without signs of inflammation, filled the area around the mesh structure and merged with the outer tissue of the ileum. No major mucosal downgrowth was detected. M = intestinal mucosa, MM = muscularis. C On the opposite side, the mesentery ran along the mesh and integrated with the vascularises fibrous tissue (FT) around the mesh. No inflammation was detected. D Light micrograph showing the absence of integration between the intestine and the inner mesh and cylindrical surface of the titanium port (EBM10, 13 weeks). The intestinal mucosa (M) migrated downwards and separated from the material surface by material-adherent tissue containing numerous inflammatory cells and bacteria (red arrowhead). E Light micrograph of the skin-implant junction (EBM11, 3 weeks). The upper portion consisted of a well-keratinised epidermis (red arrowhead) that did not reach the outer surface of the port. No epidermal downgrowth was observed. In close vicinity to the implant surface, there was a zone of massive infiltration of inflammatory cells (red asterisk), mainly PMN cells and mononuclear cells, indicating subacute/chronic inflammation. A dense layer on the titanium cylinder indicated biofilm formation (red arrow). F Light micrograph showing the integration of the subcutaneous anchor placed in the abdominal muscle tissue (AM) (EBM14, 20 weeks). The anchor was well incorporated with connective tissue growing through the perforations. The vascularised fibrous tissue (FT) consisted of collagenous bundles with different orientations, forming a capsule around the titanium (Ti). No accumulation of inflammatory infiltrates was observed

Fig. 4

A Light micrographs of the skin-penetrating outer portion of the implant (EBM12, 9 weeks). The keratinised skin ends at a distance from the implant surface (red arrowhead). The space between the epidermis and the implant was filled by granulation tissue with moderate infiltration of inflammatory cells (red asterisk). At the junction between the soft tissue and the implant (red arrow), dense connective tissue parallel to the implant was well adapted to the material surface. B–D Light micrographs showing the integration between the intestine and the inner mesh and cylindrical surface of the titanium port in a urostomy model (EBM13, 14 weeks). B On the mesenteric side, integration was observed between the external part of the intestine and the inside of the titanium cylinder and the mesh. Vascularises fibrous tissue (FT) containing focal infiltrates of macrophages, PMN cells and lymphocytes was observed. No major mucosal downgrowth was detected (red arrowhead). M = intestinal mucosa. C Light micrograph further down in the cylinder showing integration between the mesentery and the vascularises fibrous tissue (FT) around the mesh. D Light micrograph illustrating mucosal downgrowth in the same sample on the anti-mesenteric side, as well as lack of integration between the intestine and the inner mesh and cylindrical surface of the titanium port (EBM13, 14 weeks)

Fig. 5

A Light micrograph demonstrating the lack of epidermis-titanium contact in the skin-penetrating part of the port (EBM18, 28 weeks). B Epidermal downgrowth (red arrowhead) along the titanium surface was observed. C Further down, there was no tight adaptation of fibrous tissue to the surface (red arrowhead), and focal areas with bacterial growth and biofilm formation were evident (red asterisks)

Fig. 6

Backscattered electron imaging (BSE-SEM) of the interface between the external part of the intestine and the inner surfaces of the titanium implant in urostomy model (EBM13, 14 weeks; shown in Fig. 4C). Images were obtained following sample treatment with iodine in potassium iodide (Lugol) solution. A The inner mesh (Ti Mesh) and the cylinder (Ti) showing integration with the fibrous tissue (FT) at the anti-mesenteric aspect of the intestine. Yellow-dotted line depicts part of the dense fibrous capsule intimately in contact with the mesh (Ti Mesh). B Peri-implant fibrous tissue (FT) delineating the mesentery and showing vascular supply (white-dotted line; BV: blood vessel) in close vicinity to the dense capsule (yellow-dotted line) around the mesh (Ti Mesh). C Magnified area highlighting fibrous bundles with different orientations in tissues integrated with the inner cylinder shown in (A) (Red rectangle)