Porous High-density Polyethylene Research Articles

Flap prefabrication using high-density porous polyethylene in an animal model – an experimental study

BackgroundThe search for new surgical flap techniques and modifications of already existing ones is gaining increasing popularity. Progress in flap designing and harvesting have improved the functional and aesthetic results, especially in head and neck reconstruction.Material/MethodsTen pigs were used in this study. In the first operation, high-density porous polyethylene prefabrication was performed bilaterally in all pigs. After 8 weeks, each prefabricated complex was explored, resected, and macroscopically evaluated.ResultsAll of 20 prefabricated flaps survived. No serious surgical complications were observed. In 2 cases there was chronic inflammation and in 4 cases there was instability of the implant.ConclusionsAfter this experimental study, we believe that the use of high-density porous polyethylene in flap prefabrication may be a good option for reconstruction of 3-dimensional defects, especially in patients with limited donor tissues.

CT 3D Reformatting Technique to Aid Microtia Reconstruction Procedure Planning

This 8 year-old girl presented to a tertiary surgical centre with a history from birth of an absent left and a malformed right pinna, and associated bilateral hearing impairment.
 On clinical examination, the left pinna was absent and the right dysplastic. No penetrable external auditory meati were evident. Bilateral hearing impairment, more pronounced on the left, was confirmed with auditory testing.
 Prior to surgery high resolution CT imaging of the temporal bones was performed. In addition a CT of the lower thoracic cavity was undertaken to assess the costal cartilage for surgical planning.
 
 
 
 
 
 
 
 
 
 Discussion
 Microtia is a congenital deformity of the pinna, with a wide spectrum of abnormalities ranging from complete absence (anotia) to a relatively, well formed, but dysplastic pinna (Figure 2). It occurs in 1 in every 6,000 births, with a higher preponderance in select racial groups, such as the Japanese.1 
 For decades surgical procedures have been performed and evolved for the treatment of microtia. In contemporary practice theses may either be autogenous, using costal cartilage or alloplastic, using the likes of porous high density polyethylene (Medpor).2 The key autogenous surgical techniques in common practice are those described by the Brent and Nagata.3,4
 Autogenous costal cartilage is utilised in one of the key stages in reconstructing the pinna to fabricate the auricular framework. The age at which the procedure is performed is typically in childhood (8 – 10 years of age), when costal cartilage is believed to be well formed and fusion may have occurred at the mid-lower ribs levels (7th – 9th). Traditionally no pre-operative imaging has been undertaken given the difficulties with visualising cartilage at this age. On standard CT chest with traditional viewing methods the costal cartilage is poorly if at all seen in children. However, utilising some of the more advanced 3D software algorithms on contemporary CT scanners, accurate assessment to aid the surgeon prior to scheduling a procedure can be performed (Figure 1). The configuration of costal cartilage may be reviewed and if adequate fusion has occurred. A potential framework can then be outlined (Figure3a). In addition selective dimensions can be recorded to the nearest millimeter (Figure 3b). This post-processing work is undertaken with the reporting radiologist and surgical lead for the procedures.
 *Images in our institutions were acquired on Siemens Somatom 64 slice scanner with radiographic parameters of kV 120, Mas 46, slice thickness 0.6mm and DLP of 68 without the use of intravenous contrast. Coronal 3D reconstructions were performed using the InSpace software, using an arterial algorithm (Figures 1 and 3a). Alternatives employed include the use of soft tissue algorithm (Figure 3b).

One-Piece Modified Gasket Seal Technique

Objectives Review the effectiveness of a modified gasket seal technique utilizing a porous high-density polyethylene plate/rectus sheath fascia construct without fat grafting for primary closure of anterior defects following endoscopic skull base surgery. Design Retrospective review (2011-2012). Setting Single academic medical center. Methods A retrospective review of five patients who underwent expanded endoscopic endonasal surgery for various pathologies (two craniopharyngiomas, two tuberculum meningiomas, and one planum meningioma) was performed. Skull base closure was performed using a one-piece modified gasket seal technique. Primary outcome measures included postoperative cerebrospinal fluid (CSF) leaks and donor site morbidity. Results There were no postoperative CSF leaks. Two patients experienced aseptic meningitis treated with a 14-day course of steroids. Two patients experienced new postoperative chronic/recurrent sinusitis treated with oral antibiotics and topical nasal therapy. There was no donor site morbidity such as infection, hematoma, or hernias. Conclusions The one-piece modified gasket-seal closure is a safe and effective method for reconstruction of endonasal defects of the anterior skull base. Rectus sheath fascia is an appropriate dural substitute for free tissue grafting with low donor site morbidity. The construction of the one-piece graft significantly decreases operative time and lowers the learning curve for multilayered closure.

Conjunctivodacryocystorhinostomy using a high-density porous polyethylene-coated tear drain tube

To evaluate the outcome of conjunctivodacryocystorhinostomy using a high-density porous polyethylene (HDPP)-coated tear drain tube. Patients with epiphora due to a proximal lacrimal system block were included in a prospective interventional case study. A total of 22 eyes were treated with lacrimal bypass surgery using the HDPP-coated tube. On follow-up (12-41months), 21 eyes had a patent well-positioned tube with subjective relief of epiphora. In one eye, a loose sleeve was noted during surgery. The tube dislodged postoperatively and was removed. A high success rate with only a few minor complications is achievable using a HDPP-coated tear drain tube for lacrimal bypass surgery. Long-term follow-up is required to look for tube blockage due to conjunctival or nasal mucosal overgrowth.

One-Piece Modified Gasket Seal Technique

Background: The gasket-seal closure has proved to be an effective method for closure of the anterior cranial base and prevention of postoperative CSF leak following endoscopic endonasal surgery. We present our preliminary results with a modification of the gasket-seal technique, utilizing a porous high-density polyethylene plate/rectus sheath fascia construct for primary closure without intracranial fat packing.

The biocompatibility of high density porous polyethylene which is covered with fascia lata in dorsal nasal augmentation-an experimental study on rabbit model

Ten New Zealand Albino rabbits were used in this study. A lateral incision was made on the nasal dorsum and a pocket formed in the subperiosteal plane to replace the implant. A fascia lata graft was obtained from the regio femoralis. High-density porous polyethylene (HDPP) was cut and covered with fascia lata. The material was positioned in the pocket formed on the nasal dorsum. Four months post-procedure, magnetic resonance imaging (MRI) was performed to evaluate the resorption of the material. Animals were then sacrificed and the nasal dorsum, including the graft material, was removed and subjected to macroscopic and histopathological examinations. All rabbits survived the 4-month period. MRI revealed that all the graft materials were intact; no sign of resorption was evident. Macroscopically, no rejection was observed. Histopathologic examination revealed that the HDPP remained intact on the nasal dorsum. HDPP covered with fascia can therefore be used for augmentation of the nasal dorsum. HDDP is easy to work with and will avoid the increased operative time and morbidity associated with autograft harvesting.

Utility of high density porous polyethylene implants in maxillofacial surgery.

The aim of this paper was to determine the utility of high density porous polyethylene implants (HDPE) in a variety of facial skeletal deformities. Sixteen patients (age range 14-28 years) with facial deformities requiring skeletal defect reconstruction or augmentation, treated between January 2008 and December 2010. The follow-up of the patients ranged from 6 months to 2 years.The types of deformities and defects treated include: one patient each with hemifacial microsomia and nasal tip correction, two patients each with malar deformities and orbital floor reconstruction, three patients with paranasal deformities and mandibular hypoplasia and four patients with chin augmentation. A total of 24 implants were placed. The complications included infection and wound dehiscence in one patient. The implants were palpable extraorally in two patients. It is concluded that HDPE is an excellent alternative to autogenous grafts for facial skeletal augmentation. Its porous nature, excellent soft tissue growth and coverage are the advantages and disadvantages include its rigidity and sometimes it is palpable extraorally.

Enhanced performance of modified HDPE separators generated from surface enrichment of polyether chains for lithium ion secondary battery

Porous high density polyethylene (HDPE) membrane is an important type of separator for lithium ion batteries (LIBs). To improve the electrochemical performances of HDPE-based separators, a copolymer of poly(ethylene-block-ethylene glycol) (PE-b-PEG) was blended into porous HDPE separators via TIPS process. By measuring the composition, morphology and crystallinity, etc., the phase behavior and surface enrichment behavior of the HDPE/PE-b-PEG/LP system were studied. Compared with pure HDPE separators, surface enrichment of PE-b-PEG chains enhanced the compatibility between separators and liquid electrolyte and electrodes. The ionic conductivity of liquid electrolyte soaked blend separator was up to 1.24×10−3Scm−1 at 25°C. Furthermore, the interface resistance between separator and electrode was effectively reduced by the surface enriched polyether chains. All the results indicated that PE-b-PEG could be a promising blend substance to improve the electrochemical performances of HDPE separators prepared via TIPS process.

Complications Associated With Alloplastic Implants in Rhinoplasty

To evaluate the incidence of infection and extrusion of porous high-density polyethylene (pHDPE) and expanded polytetrafluoroethylene (ePTFE) implants used in rhinoplasty at a high-volume, academic facial plastic surgery practice. A total of 662 rhinoplasty procedures performed by 3 faculty surgeons from 1999 to 2008 were retrospectively reviewed. Patient demographics, medical comorbidities, operative details, and postoperative course findings were collected from patient records. The incidence of postoperative infection was 2.8% (19 of 662 patients). In each case of infection, alloplastic material had been used. Infections occurred in 1 in 5 rhinoplasty procedures in which pHDPE implants were used. In patients in whom ePTFE was used alone, the infection rate was 5.3%. Exposure developed in 12% of patients in whom an alloplast was used during surgery. Factors notably not associated with infection on bivariate analysis included sex, surgeon, purpose of procedure (functional vs cosmetic), current tobacco use, or history of cocaine use (P > .05 for all). To our knowledge, this study represents the largest evaluation of the use of pHDPE implants in rhinoplasty to date. Our findings are in contrast to those of previous studies regarding the use of pHDPE in rhinoplasty and parallel to those regarding the use of ePTFE. Caution is strongly recommended when considering the use of pHDPE in rhinoplasty.

Evaluation of a Sphere-Templated Polymeric Scaffold as a Subcutaneous Implant

To evaluate the performance of a sphere-templated poly(2-hydroxyethyl methacrylate) (poly[HEMA]) tissue scaffold as a subcutaneous implant by comparing it with widely used high-density porous polyethylene (HDPPE) implant material. We implanted sphere-templated porous poly-(HEMA) and HDPPE disks into the dorsal subcutis of C57BL/6 mice for 4 and 9 weeks. Excisional biopsy specimens of the implants and surrounding tissue were assessed for host inflammatory response, tissue ingrowth, and neovascularization using trichrome, picrosirius red, and anti-endothelial cell antibody staining. The poly(HEMA) and HDPPE implants showed resistance to extrusion and elicited a minimal inflammatory response. Both implants supported cellular and collagen ingrowth, but ingrowth within the HDPPE implant was thicker owing to the larger porous structure (>100 μm) of HDPPE, whereas the poly(HEMA) implant had much thinner collagen fibrils within much smaller (40-μm) pores, suggestive of less scar-type reaction. Neovascularization was supported by both implants. Blood vessels were identified within the fibrous ingrowth of the HDPPE and within individual pores of the poly(HEMA). Sphere-templated poly(HEMA) implanted as a subcutaneous tissue scaffold stimulates a minimal inflammatory response and supports cellular infiltration, collagen formation, and neovascularization. Because of its tightly controlled porous structure, poly-(HEMA) appears to induce less scar-type ingrowth compared with HDPPE.

Clinical Outcome of Cranioplasty With High-Density Porous Polyethylene

High-density porous polyethylene (Medpor) has long been used in cranioplasty and is still one of the best materials for calvarial reconstruction. Calvarial defects can be effectively reconstructed with fewer complications by using Medpor. This article reports our study on the use of Medpor in reconstructing calvarial defects. Twenty-three patients who underwent cranioplasty from 1999 to 2011 were included in this study. In all patients, Medpor was used for calvarial defect reconstruction, and all were followed up for at least 6 months. Most patients were satisfied with the reconstructive outcome. Only 1 patient had an infection and 1 had transient extradural seroma. All complications occurred within 2 years, and no new complications were found during the long-term follow-up. Using Medpor in cranioplasty is an effective method for reconstructing calvarial defects.

Modified Technique of Chin Augmentation With MEDPOR for Asian Patients

Commonly used chin implants are made of silicone, expanded polytetrafluoroethylene (e-PTFE), or high-density porous polyethylene (MEDPOR). Although MEDPOR is an effective implant for chin augmentation, modification of the external aspect of the implant is recommended, particularly for Asian patients, to create an appropriate shape for the new chin. It is often difficult to contour the inner aspect of the implant to conform to the patient's mandible. Without modification, a gap may exist between the implant and mandible. To address this problem, a modified augmentation technique was developed. The authors describe their modified technique for MEDPOR chin augmentation, which includes removal of the genial tubercles and, if necessary, the mental protuberance. Ninety-five patients underwent the modified MEDPOR technique of chin augmentation. Before placement of the contoured implant, a drill was used to remove the patient's genial tubercles. If the mental protuberance was deemed too prominent, it was removed as well. The implant was inserted and fixed to the mandible with 2 titanium screws. Results were satisfactory in 90 cases. Chin shape was too "strong" in 4 patients, and another patient had poor transition between the implant and mandible. Complications were minimal. The most common complication in this modified technique was lower lip numbness, which was transient in all cases. The MEDPOR chin implant can be effectively contoured to the mandible by removing the genial tubercle and/or mental protuberance. This technique is less invasive than chin osteotomy. Successful results can be achieved with minimal risks.

Comparison of Early Fibrovascular Proliferation According to Orbital Implant in Orbital Floor Fracture Reconstruction

Although reports of successful treatment results of orbital fractures are numerous, histopathologic changes associated with favorable outcomes have not yet been established. The purpose of this study was to observe fibrovascular ingrowth into implants, fibrovascularization, and inflammatory reactions in surface tissues of implants in an animal model of orbital floor fractures. Twenty-four New Zealand white rabbits were used in the study. A standardized 6-mm-diameter defect was made bilaterally in the maxillary sinuses to include bone and mucosa, and an 8 × 8-mm alloplastic implant was inserted. In the control group, a bone defect was made, but no implant was inserted. Two different implant materials 1 mm in width were used: porous high-density polyethylene (Medpor, group A) and absorbable copolymer (Macropore, group B). The implants were harvested at 1, 2, and 6 weeks after implantation. Hematoxylin-eosin stains and immunohistochemical studies of basic fibroblast growth factor (bFGF) and CD31 (platelet/endothelial cell adhesion molecule) were conducted. Full-thickness fibrovascular ingrowth into the implants was observed in group A after 2 weeks, but there was no fibrovascular ingrowth into the implant in group B. The inflammatory reactions between the implant and the connective tissue were grade 2 at 1 week and grade 1 at 2 and 6 weeks in both groups. The bFGF indexes in fibrovascular tissue growing into the nonabsorbable porous polyethylene implants (group A-1) were 0.3 at 1 week, 2.3 at 2 weeks, and 3.0 at 6 weeks. The bFGF indexes at the surface tissues of the implant in the nonabsorbable porous polyethylene implants (Medpor, group A-2) and group B were 1.0 and 1.8 at 1 week, 2.5 and 2.8 at 2 weeks, and 3.0 and 3.0 at 6 weeks. Expressions of CD31 in group A-1 were 3.8 at 1 week, 6.0 at 2 weeks, and 20.3 at 6 weeks. Expressions of CD31 in group A-2 and group B were 19.8 and 23.3 at 1 week, 38.0 and 49.3 at 2 weeks, and 64.3 and 72.0 at 6 weeks. Because there was no fibrovascular ingrowth into the absorbable copolymer implant, such implants may be advantageous in orbital wall fractures with exposures of extraocular muscle. However, the possibility of migration and extrusion of the implant cannot be excluded because there was no fibrovascular ingrowth into the absorbable copolymer implants. Therefore, nonabsorbable porous polyethylene implants are better suited for use in orbital wall fractures when there is concern about implant migration and extrusion during the early postoperative period and large orbital wall fractures.

Complete Septal Extension Grafts Using Porous High-Density Polyethylene Sheets for the Westernization of the Asian Nose

In Asian rhinoplasty, most patients need correction of the nasal tip and columella along with dorsal augmentation. A complete septal extension graft can effectively and concomitantly correct less projected tips, retracted columellar bases, and acute columella-labial angles. However, the amount of septal cartilage is not sufficient as a source for the graft; therefore, the authors used porous high-density polyethylene sheets as their graft material. Fifty-eight patients were enrolled in the study between April of 1994 and July of 2001. The authors evaluated a total of 11 measurement items (three for nasal tip, three for columella, two for alar shape or flaring, one for nostril shape, and two for symmetry of the alae and columella) by photogrammetry using standardized clinical photogrammetric techniques. Nasal tip projection, nasal bridge length, height of nose, and columella-labial angle increased significantly during an average follow-up period of 21 months, but nostril axis inclination, columellar length (Rt-Lt), and alar length (Rt-Lt) decreased significantly during the same study period. Implant exposure was noted in two cases, which was resolved by trimming the implants. Minor complications were stiffness of the columella (12 patients), buckling of the implant (nine patients), and excessive columellar show (two patients). A complete septal extension graft resulted in a more projected and caudally lengthened nasal tip; in addition, retracted columella and the acute columella-labial angle were improved aesthetically. Most complications were lower risk and preventable. Therefore, with careful use of porous high-density polyethylene, the authors could modify Asian noses into more Westernized noses. Therapeutic, IV.

Porous high-density polyethylene in facial reconstruction and revision rhinoplasty: a prospective cohort study.

IntroductionInitial methods which used human tissues as reconstruction materials caused different problems including rejection, limited shapes and infection. In 1970s, PHDPE (Medpor®) was introduced by its exclusive advantageous including no donor site morbidity, easily shaped and the minimal foreign body reaction. Hereby, we report our experience of using Medpor® in facial reconstruction especially in frontal reconstruction and orbital rim with a large sample size.MethodsThis study was a prospective cohort study. Surgical techniques included using Medpor® in reconstruction of lamina papiracea (LP) (15 patients), frontal bone (15 patients), orbital rim (18 patients) and open rhinoplasty (8 patients). All interventions on LP were performed by endoscopic procedures. All frontal operations were carried out by bicoronal incision. In orbital defects, we used subciliary incision.ResultsFrom all 56 patients, 1 case had primitive neuroectodermal tumor (PNET) of maxillary sinus. In that case, reconstruction of inferior orbital rim was not successful and extrusion was occurred after radiotherapy. In rhinoplasty and other experiences no extrusion or infection were detected within the next 1 to 3 years of follow up. There were not any palpable and visible irregularities under the skin in our experiences.ConclusionsIn this study the patients did not experience any complications during the follow up periods and the satisfaction was remarkable. Gathering these data gives rise to future review studies which can provide more organized evidences for replacing classic reconstructive methods by the presented material.

Nasal Measurements in Asians and High-Density Porous Polyethylene Implants in Rhinoplasty

To understand Asian noses, set goals for rhinoplasty, and find the best alternative columellar strut. Six values were used to evaluate the morphology of the nose: tip projection, alar-tip-columellar base angle, alar-columellar base-philtrum angle, nasolabial angle, nasofacial angle, and tip angle. One hundred average Chinese people (50 males and 50 females) were compared with 36 preoperative Chinese patients (13 males and 23 females). We presented an application of high-density porous polyethylene (Medpor) implant as a columellar strut for use in lengthening. We performed 3 surgical techniques: a single-plate strut, a double-plate strut, and a butterfly-shaped strut. Open rhinoplasty (transcolumella incision) was performed on 21 patients; closed rhinoplasty (marginal incision) was performed on 15 patients. Prominent changes in the 6 values were found in both male and female patients after rhinoplasty. An analysis of the Asian nose will help surgeons achieve better results. High-density porous polyethylene columellar strut grafts provide adequate support for refined tip definition and the shaping of the columellar-lobular angle.

Nasal Measurements in Asians and High-Density Porous Polyethylene Implants in Rhinoplasty

Nasal Measurements in Asians and High-Density Porous Polyethylene Implants in Rhinoplasty

A Paradigm Shift in Correcting Medial Orbital Fracture–Related Enophthalmos

Posttraumatic enophthalmos resulting from medial orbital wall fractures presents a complex challenge. Access to this area through traditional incisions is limited, making visualization of the fracture site difficult. This can be ameliorated by the transcaruncular approach, but with the potential for complications both with access and with reconstructive materials. The authors sought a new technique where enophthalmos correction would be based on augmenting soft tissue volume, rather than reducing the volume of the bony orbital cone. This was successfully accomplished using porous high-density polyethylene wedges. In an effort to increase overall knowledge of this technique, a retrospective review was undertaken. A retrospective chart review was undertaken to examine the senior authors' (J.F.T. and L.H.H.) experience using a lateral approach to address medial orbital fracture-related enophthalmos, aided by porous high-density polyethylene wedges to increase orbital volume. The relevant literature was reviewed and reported here. Three patients with post-medial orbital wall fracture enophthalmos were treated using a lateral approach to place porous high-density polyethylene wedges; this technique adequately corrected enophthalmos in these patients. Porous high-density polyethylene wedges can be placed into the orbit through a small lateral incision to reverse enophthalmos secondary to loss of volume after medial orbital wall fractures. Current techniques for orbital reconstruction typically focus on reduction of bony volume; this technique focuses on augmentation of soft tissue volume.

Flexible VOC sensors using conductive polymers and porous membranes for application to textiles

In order to fabricate textile-based flexible VOC sensors, two conductive polymers such as polyaniline and poly(3,4-ethylenedioxythiophene)-poly(styrene-sulfonate) (PEDOT:PSS) were used as VOC-sensing materials, and various porous organic membranes were used as base substrates on which the conductive polymers were coated. Electrical resistance change of conductive polymers by adsorption of VOCs was measured. Polyaniline showed better sensitivity than PEDOT:PSS. Porous high density polyethylene membrane exhibited the most stable signal reproducibility and dimensional stability of membrane itself. Even after covering with additional high density polyethylene membrane to protect conductive polyaniline inside, the stable signals were still obtained during repeated measurement.

Factors Affecting Porous High-Density Polyethylene Implant Exposure in Patients Undergoing Endoscopic Transsphenoidal Resection of Sellar Lesions

Objective: The purpose of this study was to determine which patient characteristics are associated with exposure of porous high-density polyethylene (PHDPE) used in transsphenoidal resection (TSR) of sellar lesions.