Introduction

During the past two decades, porous, high-density polyethylene implants (marketed as Medpor Biomaterial by Porex Surgical Inc., Newnan, GA, USA, recently acquired by the Stryker Corp., Kalamazoo, MI, USA) have been used successfully for various applications in the reconstruction or augmentation of the facial skeleton. Among its most frequent use are for repairs of the orbital floor, malar augmentation, and reconstruction of burned ears, which have become the standard methods in many centers [1–4].

Currently, less experience with the use of porous polyethylene in reconstruction of the nasal framework has been reported. Several reports on the short- and medium-range (up to several years) tolerance of facially implanted porous polyethylene have been published that claim clinical efficacy with low morbidity rates [5–7]. Among these is a report by the author, published in this journal in 1999, on 27 patients with Medpor implants followed up during a mean period of 2 years [7]. However, long-term results on larger patient series have been scarce [8]. It was therefore desirable to continue and expand the author’s 1999 study with the aim of investigating the long-term host tissue tolerance of polyethylene implants.

Materials and Methods

The author has 16 years of experience working with Medpor implants [7, 9]. Since 1996, they have been used in 102 patients (59 females and 43 males), who underwent 108 procedures with 118 Medpor implants. The patients ranged in age from 18 to 70 years (median, 29 years). The disorders included 61 nose deformities, 33 chin hypoplasias, six malar hypoplasias, and two maxillary hypoplasias. One patient had an impression in his glabellar region (Table 1).

Table 1 Patient characteristics (n = 104)
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Physical Properties of Polyethylene

Medpor is manufactured from linear, high-density, pure polyethylene, which is sintered to create a somewhat flexible framework of interconnecting pores ranging in size from 160 to 360 μm (mean, 240 μm) [1]. Polyethylene makes up approximately one-half of the implant volume (54 %), and the remaining pores are filled with air. The interconnecting, multidirectional pore structure of the implants allows rapid ingrowth of vascularized tissue, with collagen deposition that ultimately forms a highly stable complex resistant to infection, exposure, and deformation by the contractile forces of the surrounding tissues [2].

The firm nature of the material allows carving with a large scalpel blade without collapse of its pore structure. Medpor is almost as hard as cancellous bone at room temperature but has thermoplastic abilities. When submerged in hot (82–100 °C) sterile saline for several minutes, Medpor implants can be bent to a desired shape, which becomes permanent after cooling. Warmed Medpor sheets can be cut with scissors, and thicker implants can be shaped with a bone cutter or cutting burr.

Because of its white color, Medpor implants will not be visible through overlying tissue. The Medpor surface is rough, which helps to anchor it to the tissues in a desired location. This implant is insoluble in tissue fluid, has long-term structure stability, and does not resorb. Because of its high-density properties, Medpor also has high tensile strength, which resists stress and fatigue [7].

The Follow-up Study

In this prospective study, patient data were continuously entered into the Microsoft Excel program from the first year, 1996. Postoperative information was gathered during follow-up examinations, from the computerized patient charts (in which outcome, complications, and follow-up time were recorded), or a combination of the two.

Patients living in the Stockholm area frequently attended the planning of the other surgeries or accompanied relatives or friends to the clinic. Patients who lived at a distance were contacted by telephone or letter containing a questionnaire. Aesthetic outcome was based on surgeons’ and patients’ subjective evaluations. The follow-up period ranged from 6 months to 15 years (median, 7 years). Five patients were from foreign countries or had moved abroad and were not available. Three patients never showed up after their operation, or they changed their address, and the tracing failed. Five patients changed their mind and requested removal of their implant, sometimes shortly after the procedure, and four of them were excluded from the study. For others, the follow-up period was short. A total of 12 patients were excluded.

The author’s aesthetic goals for the rhinoplasties in which Medpor was used included correction of the depressed dorsum, creation of an acceptable nasal dorsum in thick or twisted noses, and sometimes tip elevation. The functional goals were the restoration or improvement of air flow through the nasal channels and sometimes speech improvement. The AlterImage computer program (Seattle Software Design, Seattle, WA, USA) for the simulation of digital images was used for operation planning in all cases.

For nasal surgery, Medpor is available as a strut or arch-formed sheet. Both soft tissue ingrowths and collagen deposition, with subsequent vascularization, occur after implantation [2, 10], as confirmed by the microscopic investigation of five biopsies [7].

Surgical Technique

The implants used in this study were applied during the first 3 years, in part carved from the Medpor block and later supplied in sterile form by the factory as prefabricated nasal, chin, or malar shapes. Maxillary onlay and glabellar implants were individually carved. These implants were fixed to the underlying bones with titanium screws (Medpor MCP Instrument Set by Porex Surgical Inc., Newnan, GA, USA) and contoured in place, as described earlier by Yaremchuk [3, 4]. New talc-free gloves were put on before handling of implants, which were held primarily with instruments to avoid contamination from the epidermis. Operations were performed with the patient under local and dissociative anesthesia [11]. The operative field was infiltrated with 1 % lidocaine solution (AstraZeneca, London, UK), which contained epinephrine (1:200,000) to minimize bleeding.

In more than 50 % of cases, implants were individually customized by trimming and shaping to adjust them according to the preference of the surgeon for each individual patient’s needs. All carving was done with a large scalpel blade on a specially made sterile plastic carving block to avoid contamination with lint or other particulate matter. It is important to feather the edges to obtain a smooth contour and eliminate any potentially visible edges of the implant.

Implants were impregnated with cloxacillin solution (Ekvacillin; AstraZeneca) using the suction infiltration technique [12], accomplished by placing each implant in a 50-ml syringe into which cloxacillin solution has been aspirated (Fig. 1). Both the implant and the receiving pocket were lubricated with 2 % lidocaine gel (AstraZeneca), which made insertion much easier.

Fig. 1
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Impregnation of the Medpor implant with cloxacillin solution is improved by negative pressure during aspiration

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Adequate soft tissue dissection and periosteal elevation were conducted to eliminate tension over the implant and to prevent implant migration or rotation. Vicryl rapide, or PDS (Ethicon, Hamburg-Norderstedt, Germany) sutures were used for adequate duration strength at the soft tissue and the mucosal closure. Densely placed sutures created a “watertight” pocket, preventing contamination of the implant with microorganisms from the nasal environment. Patients were postoperatively placed on a 7-day course of the oral antibiotic flucloxacillin (Heracillin; AstraZeneca), 750 mg twice daily.

Eight female and two male patients underwent chin augmentation through the intraoral route. For eight females and 15 males, the external submental route was chosen (Fig. 2). For one male, two implants were placed: one through a submental incision and one intraorally. The impervious plastic film OpSite (Smith&Nephew, Hull, UK) was used to isolate the incision and reduce the risk of contaminating the implant as much as possible. Additional procedures performed in connection with chin augmentation were submental liposuction [5] and anterior platysmaplasty [4]. For two patients, chin enlargement was a part of the face-lift operation.

Fig. 2
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Chin implant placement through a intraoral and b external routes

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During the past decade, the single-piece chin implant were replaced by a two-piece implant with an interlocking peg in the middle. To prevent rotation, implants were stabilized by two 3.0 multibraided, soft, nonresorbable sutures of Mersilene (Ethicon), which attached them to the periost of the mandible.

Medpor malar implants were used in patients who also had an indication for lower blepharoplasty. Under direct vision, the periost was elevated from the malar bone, and the implants were placed with the utmost precision. Each implant was stabilized by two nonresorbable sutures, as described earlier. This rigid, coarse surface of implants has very little tolerance for the differences in position of the right and left implants compared with the malar silicone implants. Therefore, the latter are the author’s material of choice for transoral malar augmentation or augmentation at face-lift surgery.

Results

During 15 years of observation, the author performed 1,220 rhinoplasties, 260 (21 %) of which were secondary or repetitive procedures. In 61 instances, including 42 difficult nasal reconstructions, Medpor was applied during nasal surgery. These cases included 28 catastrophe noses that had undergone surgery elsewhere one to four times (mostly in Middle-Eastern countries). Eight patients had undergone previous surgery by the author. Saddle nose deformity was corrected in 19 patients (Figs. 3, 4). Statistically, Medpor was used for 1 of every 21 patients, or in 4.8 % of all the rhinoplasties performed by the author.

Fig. 3
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Stable result after 14 years (right) for case MA involving a 27-year-old woman with platyrrhinia (left) corrected using a Medpor implant of the nasal arch type before the procedure

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Fig. 4
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Case EP involving a 31-year-old woman from West Africa born with the extreme platyrrhinia, which is usual in her region. View before a, b, d and 2½ years after nose refinement with the assistance of the composite, tripartial Medpor graft (c, e). Part of the figure is published with the permission of ESPRAS

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The whole postoperative course could be assessed in some patients but only part of it in the other cases. Among the 53 followed-up rhinoplasty patients, 45 (85 %) had a smooth clinical course, and the Medpor implant contributed to restoration of nasal aesthetics and function (Figs. 5, 6). The results remained stable during the observation time of up to 15 years (Fig. 7). In the chin augmentation group, 29 patients were followed up (Fig. 8). Whereas two of them had their implants trimmed, 27 (93 %) had a smooth clinical course.

Fig. 5
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Case RG involving a 26-year-old man of Iranian origin with a grotesque-appearing nose after two open-sky surgeries (left). Center: View 1½ after reconstruction involving carved, 45-mm-long Medpor graft. Another plastic surgeon injected in 2008 3 × 0.5 ml of hyaluronic acid to the tip of the man’s nose, causing skin necrosis and subsequent loss of the tip projection. Right: View 15 years after the reconstruction

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Fig. 6
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Case DS involving a 27-year-old man born in Turkey seen after four badly executed nose surgeries (left). He presented with a classic parrot beak deformity and a thick amorphic nosetip, which was reconstructed with the aid of a manually carved 50-mm-long dorsal strut of Medpor. View 3 years later (center) and 14 years later showing the stable result (right)

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Fig. 7
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Length of the follow-up period for 57 rhinoplasty patients with 58 Medpor implants

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Fig. 8
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Length of the follow-up period for 29 chin augmentation patients with 30 Medpor implants

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Implants on the nasal dorsum were fast fixed in the lower half but had undesirable mobility at the radix. Augmented chins and malar prominences were firm and bony-like at palpation. In a patient with two Medpor grafts in the chin, the first implant was placed by the external route, and the second was placed transorally 6 months later. The result was stable after 3 years (Fig. 9). The first implant increased the capital height, and the second implant provided necessary horizontal projection. The outcome was firm, bony-like unity. Correction of protruding ears and reduction rhinoplasty completed total facial amelioration.

Fig. 9
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Case NJ involving a 37-year-old man with extreme micrognathia (upper panel). His chin was enlarged with two Medpor grafts, one each in the vertical and horizontal planes (lower panel). Part of the figure is published with the permission of ESPRAS

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The remaining cases, including all malar augmentations, had uneventful clinical courses (Fig. 10). Four patients with malar augmentation were observed longer than 10 years, and this also was the average follow-up time for the whole group. In summary, 26 patients were followed up longer than 10 years, and the follow-up period for another 18 patients was longer than 5 years. Of 106 implants in 90 patients included in the follow-up evaluation, 96 (91 %) remained unchanged during the observation time.

Fig. 10
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Case AJ involving a 53-year-old man who underwent malar augmentation with Medpor implants. Ancillary procedures at the same time were lower blepharoplasty, rhinoplasty, and lip augmentation. Left: before the procedure. Center: after 8 years. Right: after 12 years

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Complications

Some complications arose during the observation time. However, all could be mastered (Table 2). The fates of the 118 Medpor grafts implanted from 1996 to 2011 have been as follows.

Table 2 Complications in 90 followed up patients with 106 Medpor implants, 1996–2011
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As mentioned earlier, three nasal and two chin implants were removed at patient request for psychological reasons, and thus were not considered medical complications per se. One of these patients, of Vietnamese origin, had an aesthetically pleasing result, but her family refused to accept her Westernized nose, necessitating removal of the implant and restoration of her nasal dorsum to its original, more Asian character. This situation provided a unique opportunity to study the whole Medpor implant 6 months after implantation and obtain histology (Fig. 11); [7].

Fig. 11
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Case AL. a Extracted Medpor implant. b Histologic cross-section of the Medpor implant 6 months after implantation. Note the surrounding capsule of fibrotic tissue and the total ingrowth of the lamellar connective tissue into all available empty spaces. Arrows indicate larger blood vessels (hematoxylin and eosin [H&E] stain; original magnification, ×8). c Beads of polyethylene surrounded by fibrous connective tissue. Moderate lymphocytary infiltration indicates a slight inflammatory reaction (H&E stain; original magnification ×20). Part of the figure is published with the permission of Springer

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Two dorsal struts and two chin implants were too large and had to be trimmed. An attempt to expand and elevate the dome of the nasal tip ended with aesthetic failure (Fig. 12). Two females with thin skin on the nasal dorsum reported problems. The one female complained about the visible edge of the nasal arch. In the other female, dorsum elevation by the nasal arch implant was insufficient, and the arch was stuffed underneath with two smaller struts. After several years, the struts dislocated, causing contour irregularities.

Fig. 12
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Case AM involving an 20-year-old girl. An attempt made to build up and expand the right dome with the Medpor graft failed

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In another patient, a chin implant with longer-than-usual lateral wings, thought to fill out jaw contour impressions distal to the jowls, resulted in palpable subcutaneous and submucosal resistances. Transmucosal trimming solved this problem.

Infection occurred in three rhinoplasty cases. In two of the patients, from the third world, Escherichia coli and Proteus bacteria were cultured respectively, and their implants were lost. The third patient had inflammation in the tip area. Staphylococcus aureus was cultured, and treatment with cloaxacillin resulted in uneventful healing. This case was described and displayed in the author’s earlier report [7].

Two additional patients experienced partial extrusion of the implant because the nasal mucosa was sutured too tightly and ruptured. After implant reduction with a rongeur, flushing with antibiotic solution, and resuturing, further healing was unproblematic.

Discussion

Animal data have demonstrated that porous, high-density polyethylene implants permit ingrowth of well-vascularized fibrous tissue within 4 weeks [10]. Implantation of Medpor for aesthetic enhancement or reconstruction in the facial region is a safe procedure. This opinion is based on the very long follow-up period extending to 5 years or more for 43 % of the patients in the current cohort and longer than 10 years in 25 % of cases, which is rare and valuable.

Medpor use in facial reconstruction has several advantages. Frequently, general anesthesia is not needed because the implant is available from the shelf. The time spent in the operating room is substantially shorter than for cases involving harvest of an autologous bone or cartilage graft, which also increases morbidity. In addition, autologous graft procedures have an unpredictable resorption rate, with consequent relapse [13, 14] and the risk of warping.

Medpor should not be considered an all-purpose solution for every difficult rhinoplasty. It is rather an adjuvant providing a stable nasal frame around which an advanced and skillful nasal surgery is performed [7, 9].

In 2003, Yaremchuk [3] described three key maneuvers for accurate skeletal augmentation with porous polyethylene: (1) wide subperiosteal exposure of the area to be augmented, (2) screw fixation of the implant to the underlying bone, and (3) “in-place” implant contouring. These principles currently are generally accepted, but they do not apply to nasal surgery using an endonasal technique. With this technique, the proper, firm implant position relies on the precise size of the pocket and the coarse, sticky surface of the implant.

The three principles also have worked well with chin implants, which were additionally secured to the periosteum with nonresorbable sutures. Likely for the first time, the superimposed sandwich chin grafts of porous polyethylene were used successfully in a clinical case (Fig. 9).

The complication rates for Medpor are site related. Whereas implants placed subperiosteally on rigid surfaces, such as the chin or the malar prominence (Fig. 10), usually have an uneventful clinical course, implants placed in mobile body parts and areas with thin tissue coverage, such as the ear or nose, are at higher risk of extrusion or displacement. It is not surprising that in the rhinoplasty group, most complications occurred in the reconstructive cases with multiple previous surgeries, whereas in 19 patients with platyrrhinia, only two cosmetic complications were noted, namely, visible or irregular edges of the implant. This was similar to a recently described drawback with the use of excessively thin autologous grafts for nasal augmentation [15]. Gürlek et al. [16] reported three seromas in their series of 20 patients with Medpor chin implants. No seromas have been encountered in 33 patients with chin implants or in the remaining 68 patients included in this study.

In the nose, grafts placed on the stiff dorsal bridge are easier to maintain than grafts in the mobile columella. In the studied rhinoplasty population, 21 % had secondary deformities, many with primary trauma in third world countries and with a history of one or more unsuccessful correction attempts, mostly done in their home countries. Complications could therefore be expected in such rhinoplastic disaster cases regardless of the type of graft used. In this patient cohort, social habits rather than perioperative risk factors are suspected triggers for two of three nasal infections.

It could be argued that many patients in this study were followed up only for 1 or 2 years. Some others were from foreign countries, and together with the dropouts, their clinical course is unknown, so the complication rate could actually be higher. On the other hand, the clinic has the same address and phone number, and it is natural that in the case of trouble, patients return, whereas those with good results are reluctant to bother with the checkup.

Use of foreign materials in nasal reconstruction has always been and still is controversial. The silastic rubber, proplast, paraffin acrylic, Teflon and other materials used in rhinoplasty have always failed to fulfill promised expectations of long-term support and biocompatibility. The outcome has been immediate or eventual host rejection, infection, and extrusion, with a frequently serious sequel for the patient. Therefore, many experienced surgeons take a categorical stand never to use these materials [17, 18].

However, porous polyethylene is different. Its structure allows ingrowth. It becomes “semiviable” and is integrated with the surrounding host tissues (Fig. 11). The main drawback considered by many surgeons is that it is not known how porous polyethylene is tolerated by the human body in the long term. This study provides such data concerning the biocompatibility of Medpor.

Porous polyethylene currently seems to be the best alloplastic material available as a facial bone substitute. It is long-lasting, with a low frequency of complications and morbidity similar to procedures involving autologous grafts and high overall patient satisfaction [13, 19, 20].