Evaluation and Management of Exposed High-density Porous Polyethylene Implants

Crushed Cartilage and Autologous Fat for Dorsal Nasal Refinement

BACKGROUND

Dorsal contour irregularities remain a potential undesirable sequela of rhinoplasty. Use of dorsal onlay grafts can camouflage such irregularities. In this article, a novel technique for dorsal onlay grafting utilizing crushed cartilage mixed with autologous fat is described. This study aims to assess long-term graft retention and aesthetic outcomes with this technique.

METHODS

Patients with >18-month follow-up who underwent primary open rhinoplasty with the described technique were reviewed. Three-dimensional photographs taken at multiple timepoints were overlaid with volumetric subtraction used to quantify graft retention. The Rhinoplasty module of the FACE-Q was completed by each patient, and the Rhinoplasty Assessment Scale Photographic (RASP) was completed by surgeon reviewers. Pre- and postoperative changes in dorsal height as well as RASP scores were compared with paired t-tests. Changes in BMI, dorsal volume, and dorsal height were compared with linear regression. P values <0.05 were considered significant.

RESULTS

Fourteen patients were included, mean age 32. Mean intermediate and final follow-up was 17.8 months and 28.9 months, respectively. There were no statistically significant dorsal height change (mean = 0.0 mm, p = 0.91) and minimal dorsal volume change (mean = 0.02 cm³, range:  0.08 to 0.13). Patients reported a high degree of satisfaction with facial/nasal appearance and psychological/social functioning. There was a statistically significant improvement in RASP scores (p < 0.001) postoperatively.

CONCLUSION

Crushed septal cartilage mixed with autologous fat is an effective option for dorsal nasal onlay in rhinoplasty and is associated with excellent graft retention, patient satisfaction, and nasal aesthetics.

LEVEL OF EVIDENCE IV

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Additive Manufacturing of Multi-Scale Porous Soft Tissue Implants That Encourage Vascularization and Tissue Ingrowth

Medical devices, such as silicone-based prostheses designed for soft tissue implantation, often induce a suboptimal foreign-body response which results in a hardened avascular fibrotic capsule around the device, often leading to patient discomfort or implant failure. Here, it is proposed that additive manufacturing techniques can be used to deposit durable coatings with multiscale porosity on soft tissue implant surfaces to promote optimal tissue integration. Specifically, the "liquid rope coil effect", is exploited via direct ink writing, to create a controlled macro open-pore architecture, including over highly curved surfaces, while adapting atomizing spray deposition of a silicone ink to create a microporous texture. The potential to tailor the degree of tissue integration and vascularization using these fabrication techniques is demonstrated through subdermal and submuscular implantation studies in rodent and porcine models respectively, illustrating the implant coating's potential applications in both traditional soft tissue prosthetics and active drug-eluting devices.

Argon plasma improves the tissue integration and angiogenesis of subcutaneous implants by modifying surface chemistry and topography

BACKGROUND

Tissue integration and vessel formation are important criteria for the successful implantation of synthetic biomaterials for subcutaneous implantation.

OBJECTIVE

We report the optimization of plasma surface modification (PSM) using argon (Ar), oxygen (O2) and nitrogen (N2) gases of a polyurethane polymer to enhance tissue integration and angiogenesis.

METHODS

The scaffold's bulk and surface characteristics were compared before and after PSM with either Ar, O2 and N2. The viability and adhesion of human dermal fibroblasts (HDFs) on the modified scaffolds were compared. The formation of extracellular matrix by the HDFs on the modified scaffolds was evaluated. Scaffolds were subcutaneously implanted in a mouse model for 3 months to analyze tissue integration, angiogenesis and capsule formation.

RESULTS

Surface analysis demonstrated that interfacial modification (chemistry, topography and wettability) achieved by PSM is unique and varies according to the gas used. O2 plasma led to extensive changes in interfacial properties, whereas Ar treatment caused moderate changes. N2 plasma caused the least effect on surface chemistry of the polymer. PSM-treated scaffolds significantly (P<0.05) enhanced HDF activity and growth over 21 days. Among all three gases, Ar modification showed the highest protein adsorption. Ar-modified scaffolds also showed a significant upregulation of adhesion-related proteins (vinculin, focal adhesion kinase, talin and paxillin; P<0.05) and extracellular matrix marker genes (collagen type I, fibronectin, laminin and elastin) and deposition of associated proteins by the HDFs. Subcutaneous implantation after 3 months demonstrated the highest tissue integration and angiogenesis and the lowest capsule formation on Ar-modified scaffolds compared with O2- and N2-modified scaffolds.

CONCLUSION

PSM using Ar is a cost-effective and efficient method to improve the tissue integration and angiogenesis of subcutaneous implants.

Enhancing tissue integration and angiogenesis of a novel nanocomposite polymer using plasma surface polymerisation, an in vitro and in vivo study

Current surgical reconstruction of facial defects including nose or ear involves harvesting patient's own autologous tissue, causing donor site morbidity and is limited by tissue availability. The use of alternative synthetic materials is also limited due to complications related to poor tissue integration and angiogenesis, which lead to extrusion of implants and infection. We intend to meet this clinical challenge by using a novel nanocomposite called polyhedral oligomeric silsesquioxane poly(carbonate-urea)urethane (POSS-PCU), which has already been successfully taken to the clinical bench-side as a replacement for trachea, tear duct and vascular by-pass graft. In this study, we aimed to enhance tissue integration and angiogenesis of POSS-PCU using an established surface treatment technique, plasma surface polymerisation (PSP), functionalising the surface using NH2 and COOH chemical groups. Physical characterisation of scaffolds was achieved by using a number of techniques, including water contact angle, SEM, AFM and XPS to study the effects of PSM modification on the POSS-PCU nanocomposite in detail, which has not been previously documented. Wettability evaluation confirmed that scaffolds become hydrophilic and AFM analysis confirmed that nano topographical alterations resulted as a consequence of PSP treatment. Chemical functionalisation was confirmed using XPS, which suggested the presence of NH2 and COOH functional groups on the scaffolds. The modified scaffolds were then tested both in vitro and in vivo to investigate the potential of PSP modified POSS-PCU scaffolds on tissue integration and angiogenesis. In vitro analysis confirmed that PSM modification resulted in higher cellular growth, proliferation and ECM production as assessed by biochemical assays and immunofluorescence. Subcutaneous implantation of modified POSS-PCU scaffolds was then carried out over 12-weeks, resulting in enhanced tissue integration and angiogenesis (p < 0.05). This study demonstrates a simple and cost effective surface modification method to overcome the current challenge of implant extrusion and infection caused by poor integration and angiogenesis.

In vivo tissue response and durability of five novel synthetic polymers in a rabbit model

Alloplastic materials are frequently used in facial plastic surgeries such as rhinoplasty and nasal reconstruction. Unfortunately, the ideal alloplastic material has not been found. This experimental study evaluates the tissue response and durability of five novel polymers developed as an alloplastic material. In this experimental study involving a tertiary university hospital, six subcuticular pockets were formed at the back of 10 rabbits for the implantation of each polymer and sham group. Each pocket was excised with its adjacent tissue after three months, and collected for histopathological examination. Semi-quantitative examination including neovascularisation, inflammation, fibrosis, abscess formation, multinucleated foreign body giant cells was performed, and integrity of polymer was evaluated. A statistical comparison was performed. No statically significant difference was detected in neovascularisation, inflammation, fibrosis, abscess formation and multinucleated foreign body giant cells when a paired comparison between sham and polymer II, III and IV groups was performed individually. Nevertheless, the degree of fibrosis was less than sham group in polymer I (p = .027) and V (p = .018), although the other variables were almost similar. The integrity of polymers III (9 intact, 1 fragmented) and IV (8 intact, 2 absent) was better than the other polymers. These novel synthetic polymers could be considered as good candidates for clinical applicability. All polymers provided satisfactory results in terms of tissue response; however, fibrovascular integration was higher in polymers II, III and IV. In addition, the durability of polymer III and IV was better than the others.

Use of porous high-density polyethylene grafts in open rhinoplasty: no infectious complication seen in spreader and dorsal grafts

OBJECTIVE

The aim of this study is to use porous high-density polyethylene grafts (Medpor) in open rhinoplasty and then assess complication rate and aesthetic outcomes.

METHODS

In a prospective cohort study, we performed open rhinoplasty and employed Medpor as rhinoplasty grafts. Then we compared their complication rate.

RESULTS

In a total of 64 patients, 84 Medpor grafts--8 dorsal grafts, 23 strut grafts, 8 rim grafts, 5 button grafts and 10 spreader grafts--were utilized. Moreover, 5septal perforation repairs with Medpor were performed. The complication rates were 5.3% in dorsal graft (complication in dorsal graft was only movement of implant), 21.7% in strut graft and 25.0% in rim graft. No complication was seen in spreader and button grafts. All 5septal perforation repairs were successfully performed with the same rhinoplasty approach.

CONCLUSION

Medpor can be used as dorsal and spreader graft in reconstruction of severe nose deformity with lowest complication rate and without infectious complication and extrusion.

Use of rapidly hardening hydroxyapatite cement for facial contouring surgery

Hydroxyapatite cement is an ideal alloplastic material to replace the autogenous bone grafts in craniofacial surgery. Hydroxyapatite cement is advantageous because it can be easily molded by hand unlike other alloplastic materials such as silicone and high-density polyethylene. For aesthetic applications of hydroxyapatite cement, we evaluated the efficacy and safety of the rapidly hardening hydroxyapatite cement used in facial contour augmentation, especially for the forehead and the malar area. A total of 18 cases of facial skeleton augmentation or contouring surgery using rapidly hardening hydroxyapatite cement (Mimix; Biomet, Warsaw, IN) were examined, and the long-term cosmetic results and any complications were also analyzed. The aims of facial contouring surgeries were to correct the following conditions: hemifacial microsomia, craniosynostosis, posttraumatic facial deformity, deformity after tumor resection, dentofacial deformity, and Romberg disease. The application sites of hydroxyapatite cement were the forehead, malar area, chin, and paranasal area. A mean of 16 g (range, 5-50 g) of the hydroxyapatite cement was used. Postoperative infection, seroma, and migration of the implant were not observed during the follow-up period of 23 months. Rapidly hardening hydroxyapatite cement, Mimix, is easy to manipulate, promptly sclerotized, and can be replaced by living bone tissue, with a low complication rate. Therefore, it can be an optimal treatment that can be used instead of other conventional types of alloplastic materials used in facial contouring surgery.

Current status of grafts and implants in rhinoplasty: Part II. Homologous grafts and allogenic implants

LEARNING OBJECTIVES

After reading this article, the participant should be able to: 1. Understand the challenges in restoring volume and structural integrity in rhinoplasty. 2. Identify the appropriate uses of various homologous grafts and allogenic implants in reconstruction, including: (a) freeze-dried acellular allogenic cadaveric dermis grafts, (b) irradiated cartilage grafts, (c) hydroxyapatite mineral matrix, (d) silicone implants, (e) high-density polyethylene implants, (f) polytetrafluoroethylene implants, and (g) injectable filler materials. 3. Identify the advantages and disadvantages of each of these biomaterials. 4. Understand the specific techniques that may aid in the use these grafts or implants.

SUMMARY

This review specifically addresses the use of homologous grafts and allogenic implants in rhinoplasty. It is important to stress that autologous materials remain the preferred graft material for use in rhinoplasty, owing to their high biocompatibility and low risk of infection and extrusion. However, concerns of donor-site morbidity, graft availability, and graft resorption have motivated the development and use of homologous and allogenic implants.