Clinical Note Clinical Outcome of 285 Medpor Grafts used for Craniofacial Reconstruction PATIENTS AND METHODS

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1 Clinical Note Clinical Outcome of 285 Medpor Grafts used for Craniofacial Reconstruction Roberto Cenzi, MD,* Antonio Farina, MD, y Luca Zuccarino, MD, z Francesco Carinci, MD Ferrara, Italy Porous polyethylene (Medpor) is an alloplastic material worldwide used for craniofacial reconstruction. To evaluate complications and risk factors associated with this synthetic graft, a retrospective study was performed. A series of 285 Medpor grafts were placed in 187 patients. Age, sex, diagnosis at admission, site, type of surgical insertion, type of fixation, and outcome (no complications, anesthesia, exposure, infection, and implant remodeling and removal) are considered. By means of univariate and multivariate analyses, we detect variables most associated with poor outcome. Univariate analysis showed that graft survival curves stratified according to (1) diagnosis at admission and (2) site are statistically significant. Subsequently, a Cox analysis was performed: both variables are also predictors of graft outcome. Porous polyethylene is a reliable alloplastic material that can be satisfactory used for craniofacial reconstruction. However, some sites (i.e., nose, maxilla, and ear) and diagnosis at admission (i.e., syndromic patients previously operated) are related to an higher risk of implant failure. operation time. On the contrary, homologue bank tissues and animal derived products are not completely safe because unknown diseases can be potentially transferred. Consequently, alloplastic materials are used for craniofacial reconstruction. Among them, porus polyethylene (Medpor) has been extensively used since the 1990s. Its properties make it an excellent choice for correcting cranial and facial defects. The implant is easy to shape, flexible, remarkably stable, and exhibits rapid soft-tissue ingrowth. Porus polyethylene has been used to repair cranial defects, 1 4 to restore facial deformities, 5 7 to reconstruct ear 8,9 and orbit 10,11, as spherical orbital prosthesis, to correct lower eyelid retraction, 15,16 and to restore nasal function and shape Reported complications are persisting pain and anesthesia, implant exposure, infection, and subsequent graft removal. From this point of view, however, there is a lack in regards to rate of failure and associated risk factors. Consequently, we analyzed the clinical outcome of 285 Medpor grafts used for craniofacial reconstruction to detect complications and risk factors. Key Words: Facial reconstruction, alloplastic material, Medpor, porous polyethylene, Cox analysis Craniofacial skeletal defects should be ideally correct with autologous bone or cartilage. However, collecting an adequate amount of bone from other donor sites of the same patient is not always possible, it carries additional morbidity, and it makes for a prolonged From the *Department of Maxillofacial Surgery, Civil Hospital, Rovigo, y Department of Histology, University of Bologna, z Department of Maxillofacial Surgery, University of Ferrara, and Department of Maxillofacial Surgery, University of Ferrara, Italy. Address correspondence to Dr. Carinci Francesco, Chair of Maxillofacial Surgery, ENT Clinic, Arcispedale S. Anna, Corso Giovecca, 203, Ferrara, Italy; crc@unife.it PATIENTS AND METHODS One hundred eighty-seven patients consecutively grafted with porous polyethylene for craniofacial reconstruction were enrolled in this retrospective study. They were operated at the Civil Hospital of Rovigo between January 1992 and June The mean follow-up was 60 months. Patients Patients included 103 (55.1%) males and 84 (44.9%) females. They ranged in age from 5 to 83 (median age 27) years at the time of admission. The diagnosis were as follows: 43 (23%) craniofacial fractures, 65 (34.8%) class II and III malocclusions, 35 (18.7%) facial or craniofacial tumors, and 44 (23.5%) craniofacial malformations (i.e., Treacher-Collins syndrome, Goldenhar syndrome, Binder syndrome, cleft lip and palate, ear malformations). 526

2 OUTCOME OF 285 MEDPOR GRAFTS FOR CRANIOFACIAL RECONSTRUCTION / Cenzi et al Grafted Sites Eight sites were grafted. The number of grafts per site was as follows: 9 ribs, 35 zygomatic bones, 65 cranial vaults, 56 mandibles, 27 ears, 40 maxillae, 49 orbits, and 4 noses. Grafts were inserted as follows: 27 inlay, 242 onlay, 10 onlay plus polyethylene fragments, 4 polyethylene fragments, 2 onlay plus inlay. Two hundred twenty-six (79.3%) grafts were fixed with screws, whereas the remaining 59 (20.7%) were sutured. Treatment and Outcome Usually, Medpor grafts were inserted in a one-stage procedure during the treatment of the main pathology. In cancer patients, for example, porous polyethylene was placed in the temporal fossa after tamporalis muscle transposition for maxillary reconstruction; in blow-out fractures, Medpor was used to restore the continuity of orbital floor; in cases of class II and III malocclusion as well in syndromic patients, Medpor was inserted to improve maxillary and mandible contour, to rebuild ear, and to restore nasal shape and to paranal area. Note that syndromic patients (for example, cleft patients) underwent more than one surgical procedure so that grafts were inserted very often in scarring tissues. All patients were followed up and examined on a monthly basis for the first 6 months after treatment and every 6 months thereafter. Implant exposure, infection, graft remodeling, and removal were considered treatment failures. of independent variables such as age and sex and whether an event (i.e., exposure, infection, and graft remodeling and removal) is likely occur. If the associated probability was less then 5% (P, 0.05), the difference was considered statistically significant. In the process of performing the regression analysis, odds ratios and 95% confidence bounds were calculated. Confidence bounds did not have to include the value Stepwise Cox analysis allowed us to detect the variables most associated with graft failure. RESULTS The variables analyzed were age, sex, patient s disease, site, type of insertion (i.e., inlay, onlay, polyethylene fragments, onlay plus polyethylene fragments, and onlay plus inlay), primary stability (obtained by screws or sutures), and outcome. The last was classified as good and failure (if there were implant exposure, infection, graft remodeling, and removal). Global disease-specific survival rate was approximately 93% (Fig 1). Among the studied variables, we considered only those associated with a significant effect on graft survival rate. Survival curves stratified according to patient diseases are reported in Figure 2. Grafts inserted in syndromic patients have a worse outcome (x 2 =14.87, 3 df, P, , log rank test). Figure 3 shows survival curves stratified according to sites: nose, maxilla, and ear have worse outcomes (x 2 = 39, Statistical Analyses Univariate analysis Disease-specific survival curves were calculated according to the product-limit method (Kaplan- Meier algorithm) 20. Time zero was defined as the date of the graft insertion. Grafts that are still inserted were included in the total number at risk only up to the time of the patient s last follow-up. Therefore, the implant survival rate only changed when one of the failure variables occurred. The calculated graft survival rate was the maximum estimate of the true survival curve. A log rank test was used to compare survival curves, generated by stratifications for a variable of interest. Cox regression analysis Cox regression analysis was then applied to determine the single contribution of covariates on graft survival rate. Cox regression analysis compares survival data while taking into account the statistical value Fig 1 Overall disease-specific survival rate. 527

3 THE JOURNAL OF CRANIOFACIAL SURGERY / VOLUME 16, NUMBER 4 July df, P = , log rank test). Survival curves stratified according to type of graft insertion are reported in Figure 4. No statistically significant difference was detected (x 2 =4.8, 4 df, P, 0.3, log rank test). No difference was noted as regard type of fixation (i.e., screws vs. sutures) (x 2 =2.07, 1 df, P = 0.15, log rank test) (Fig 5). Cox analysis was then performed by using those variables that reach a statistically significant value in univariate analysis (i.e., patient disease and site). Multivariate analysis was adjusted for patient s age and sex (Table 1). Site and type of graft insertion reached a statistically significant value. Table 2 lists the series by causes of failure. Fig 2 Disease-specific survival rate calculated according to patient disease categories (x 2 = 14.87, 3 df, P, , log rank test). (1) Class II and III malocclusions (96 grafts); (2) fractures (57 grafts); (3) tumors (38 grafts); (4) malformations (93 grafts). DISCUSSION Although autologous bone and cartilage graft are the gold standard for craniofacial reconstruction, they carry additional morbidity related to the second operation field and to a prolonged operation time. Moreover, bone grafts resorb in a way that is not predictable, and in some sites (such as the temporal fossa), they can not be used. Consequently, alloplastic materials have a specific role in craniofacial reconstruction, especially because they are more safe compared with homologue bank tissues and animal derived products, which can potentially transfer diseases of an unknown etiology. Fig 3 Disease-specific survival rate calculated according to grafted site categories (x 2 = 39, 7df, P = , log rank test). (1) Rib (9 grafts); (2) zygomatic bone (35 grafts); (3) cranial vault (65 grafts); (4) mandible (56 grafts); (5) ear (27 grafts); (6) maxilla (40 grafts); (7) orbit (49 grafts); (8) nose (4 grafts). Fig 4 Disease-specific survival rate calculated according to type of graft insertion (x 2 = 4.8, 4df, P, 0.31, log rank test). (1) Inlay (n = 27); (2) onlay + polyethylene fragments (n = 10); (3) onlay (n = 242); (4) polyethylene fragments (n = 4); (5) onlay + inlay (n = 2). 528

4 OUTCOME OF 285 MEDPOR GRAFTS FOR CRANIOFACIAL RECONSTRUCTION / Cenzi et al Table 1. Cox Regression Analyses Performed by Considering Univariate Significant Variables 95.0% Confidence Interval for Hazard Rate Variables Hazard Rate Lower Upper P Value Sex ns Age ns Graft site Diagnosis Medporisapure polyethylenewith a uniquemanufacturing process and pore size. Technically, it is easy to work with; it can be carved, contoured, adapted, and fixated to obtain a precise, three-dimensional construct. Physically, it is a pure, biocompatible, and strong substance that does not resorb or degenerate. It demonstrates long-term stability, high tensile strength, and a virtual lack of surrounding soft-tissue reaction. Several articles have shown porus polyethylene s effectiveness to restore craniofacial defects Few complications are reported: persistent pain, paresthesia, implant exposure, infection, and subsequent graft removal. From this point of view, however, there is a lack in regards to rate of failure and associated risk factors, and therefore we analyzed the clinical outcome of 285 Medpor grafts to detect variables associated with implant failure. Our global rate of complication is 6.31%, which is comparable with that reported in large series. 5 7,11,13,16 Main causes of failure are exposure with subsequent infection. Implant removal was the treatment in most cases. Sometimes, it was possible to remodel the graft to remove the infected part of the graft (Table 2). Diagnosis at admission and site are associated with a statistically significant higher risk of failure (Table 1). As regards the site, nose, maxillae, and ear are sites with worse outcome. Previous studies in large series 17,18 have shown that porous polyethylene implants can be successfully used for nasal reconstruction, but infections are possible because grafts are usually inserted in secondary rhinoplasty where extensive scarring and thin, soft tissue coverage are encountered. Ear reconstruction has similar problems, especially those related to a thin skin. Moreover, different areas of a single site have different outcomes. In the maxilla, for example, grafts placed in the paranasal area have an higher risk of infection compared with those inserted in other part of upper jaw and in the ear; grafts inserted behind the cartilage to increase the outer projection have a better prognosis compared with those used for ear reconstruction. Seven of 40 grafts placed in the maxilla have mucosal exposure and then infection. Most complications arose in syndromic patients where notable scars of previous operations were present. Those scars reduced tissue elasticity. The same factor explains why diagnosis at admission has a significant statistical impact. In fact, syndromic patients (for example, cleft patients) underwent more than one surgical procedure so that grafts were inserted very often in scarring tissues. Table 2. Distribution of the Series According to Causes of Failure Sex Age Diagnosis Site Fixation Type of Insertion Cause of Failure F 18 Fracture Maxilla Screws Onlay Removal F 26 Malformation Maxilla Screws Onlay Removal F 23 Malformation Maxilla Screws Onlay Removal F 17 Malformation Maxilla Screws Onlay Removal F 6 Malformation Maxilla Screws Onlay Removal F 6 Malformation Maxilla Screws Onlay Removal M 30 Malocclusion Mandible Screws Onlay + fragments Removal M 29 Fracture Zygomatic bone Screws Onlay Removal M 25 Fracture Mandible Screws Onlay Removal M 8 Malformation Ear Sutures Onlay Removal M 8 Malformation Ear Sutures Onlay Removal M 7 Malformation Nose Sutures Onlay Removal M 7 Malformation Nose Sutures Onlay Removal M 33 Malformation Ear Sutures Onlay Removal M 43 Malformation Mandible Sutures fragments Removal M 27 Malformation Mandible Screws Onlay Removal M 17 Malformation Maxilla Screws Onlay Remodeling M 57 Tumor Ear Screws Onlay Removal 529

5 THE JOURNAL OF CRANIOFACIAL SURGERY / VOLUME 16, NUMBER 4 July 2005 Paresthesia is a minor complication reported in literature. Ng et al 11 describe a series of 30 patients with orbital blowout fractures that were repaired using porous polyethylene sheets. They reported one major complication (a case of recurrent implant infection leading to implant removal) and three minor postoperative complications (2 cases of postoperative infraorbital anesthesia and 1 case of a palpable titanium screw). In our series, reconstruction of the orbital floor is related to an high rate of paresthesia (11 of 49 cases), but this symptom was present preoperatively, and it was associated with an orbital floor macrogap. Consequently, it cannot be related to graft insertion. Type of surgical insertion and type of fixation did not reach statistical prognostic values. Although a mixed system of insertion occurred in only 5.6% of our series, these have a worst outcome (Fig 4). This trend occurs because the higher the number of grafts and surgical procedures, the higher is the risk of contamination. Because no difference was noted between grafts fixed with or without screws, we can infer that a correct implant integration can be obtained without screws if the graft has a good primary stability. In conclusion, porous polyethylene implants offer an excellent alternative to bone and cartilage in reconstruction of many facial defects and deformities. It is a biocompatible, strong substance that does not resorb or degenerate. It is easy to work with, can be fixated, and demonstrates long-term stability. However, exposure and infection are possible, especially in grafts covered by thin and scarring soft tissues. Consequently, some sites (i.e., nose, maxilla, and ear) and diagnosis at admission (i.e., syndromic patients who have undergone several operations) are risk factors that can affected the clinical outcome. 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