Porous Polyethylene Implants in Orbital Blow-Out Fractures and Enophthalmos Reconstruction

A Narrative Review of u-HA/PLLA, a Bioactive Resorbable Reconstruction Material: Applications in Oral and Maxillofacial Surgery

The advent of bioresorbable materials to overcome limitations and replace traditional bone-reconstruction titanium-plate systems for bone fixation, thus achieving greater efficiency and safety in medical and dental applications, has ushered in a new era in biomaterial development. Because of its bioactive osteoconductive ability and biocompatibility, the forged composite of uncalcined/unsintered hydroxyapatite and poly L-lactic acid (u-HA/PLLA) has attracted considerable interest from researchers in bone tissue engineering, as well as from clinicians, particularly for applications in maxillofacial reconstructive surgery. Thus, various in vitro studies, in vivo studies, and clinical trials have been conducted to investigate the feasibility and weaknesses of this biomaterial in oral and maxillofacial surgery. Various technical improvements have been proposed to optimize its advantages and limit its disadvantages. This narrative review presents an up-to-date, comprehensive review of u-HA/PLLA, a bioactive osteoconductive and bioresorbable bone-reconstruction and -fixation material, in the context of oral and maxillofacial surgery, notably maxillofacial trauma, orthognathic surgery, and maxillofacial reconstruction. It simultaneously introduces new trends in the development of bioresorbable materials that could used in this field. Various studies have shown the superiority of u-HA/PLLA, a third-generation bioresorbable biomaterial with high mechanical strength, biocompatibility, and bioactive osteoconductivity, compared to other bioresorbable materials. Future developments may focus on controlling its bioactivity and biodegradation rate and enhancing its mechanical strength.

Early Hypoglobus in Orbital Floor Reconstruction With Resorbable Implants

BACKGROUND

Among the variety of materials developed for facial bone surgery, resorbable implants are widely used in orbital wall reconstruction. There are many advantages in selecting resorbable implants, such as minimal foreign body reaction and adjustability within the damaged orbital floor. Resorbable implants are supposed to remain in place over 1 to 2 years to hold the structure of immature healing tissue surrounding the bony defects. However, some patients who have undergone orbital wall reconstruction surgery with resorbable implants suffer from early hypoglobus.

METHODS

This retrospective study was performed from January 2014 to August 2019 and follows 39 patients with unilateral pure orbital floor fractures. All orbital floor reconstruction was performed using resorbable implants via the transconjunctival approach. Exophthalmometer measurements and CT scans showing the degree of implant sagging were used to provide an index of hypoglobus.

RESULTS

Most patients showed hypoglobus over 3 to 4 months follow-up. The size of bony defect in the orbital floor showed positive correlation with follow-up exophthalmometer measurement and degree of implant sagging.

CONCLUSION

Orbital floor reconstructed with resorbable implant tends to lose load-bearing strength gradually, especially in large bony defects. Therefore, surgeons should be cautious about using resorbable implants for the maintenance of reconstructed orbital floor, especially in large bony defects.

Clinical outcome following intraoperative computed tomography-assisted secondary orbital reconstruction

BACKGROUND

Secondary post-traumatic orbital reconstructions are challenging. Portable computed tomography (CT) provides the option to acquire real-time, intraoperative images that help to detect the insufficient reconstruction of the orbit immediately. We retrospectively analyzed patients who received intraoperative CT imaging and analyzed the effect of intraoperative CT scans on revision rates and orbital volume changes before, during, and after surgery.

METHODS

From August 2014 to September 2016, eleven patients received intraoperative cone-beam CT scans to evaluate the results of secondary orbit reconstruction using Medpor + titanium implants. Patient demographics, surgical details, CT scanning protocol, and follow-up results were analyzed. 3D CT volumetry was used to analyze the orbital volume based on OsiriX MD software.

RESULTS

Based on intraoperative CT findings, seven cases required intraoperative revision to further augment the orbital cavity or adjust implants. The mean preoperative measured enophthalmos was 3.41±1.4 mm (range: 2-6 mm), which decreased to 0.73±0.4 mm (range: 0-1 mm) at postop assessment (p<0.0001). On the fracture side, there was a significant difference between preoperative vs. intraoperative and preoperative vs. postoperative volume measurements (p<0.01 for both subsets), but no significant difference between intraoperative vs. postoperative measurements.

CONCLUSION

Intraoperative CT is a valuable tool in secondary orbital reconstruction cases based on clinical enophthalmos evaluation and 3D CT volumetry. For these patients, the avoidance of another revision surgery may outweigh the disadvantage of increased operation time and additional radiation exposure.

Orbital Roof Reconstruction Using Nylon Foil Implants

PURPOSE

To describe a surgical technique of orbital roof reconstruction with a thin nylon foil implant.

METHODS

This study is a description of a surgical technique with a retrospective chart review of 3 consecutive patients treated with a nylon foil implant for a complete superior orbital defect after meningioma resection via craniotomy approach.

RESULTS

The nylon foil reconstruction achieved an anatomically stable orbit without globe dystopia, pulsatile proptosis, cerebrospinal fluid leak, or other serious cranio-orbital problems, in all cases. Postoperative visual acuity, pain, extraocular motility, proptosis, and globe position remained stable or improved in each case. There were no complications related to the orbital roof reconstruction.

CONCLUSIONS

Nylon foil implantation was an effective and inexpensive surgical technique for orbital roof reconstruction after tumor resection in this small series.

Restoration of the inferomedial orbital strut using a standardized three-dimensional printing implant

The inferomedial orbital strut (IOS) is the thin bony junction of the orbital medial wall and floor. Its fracture is common and leads to serious complications, including enophthalmos, globe dystopia and diplopia. However, anatomical restoration of the IOS is challenging owing to reduced structural support; sound anatomical background and accurate implants are therefore essential. The aim of the present study was to incorporate data from cadaveric orbit anatomy into three-dimensional (3D) printing technology and to reconstruct the complex orbital fracture elaborately. After averaging the data from computed tomography (CT) images of 100 adult cadavers, the dimensions of the IOS were extracted, and a tangent sphere was created using a computer-aided design program. The curves were compared with the CT data of 10 adult patients from the simulation test. Based on these data, a standardized 3D implant, 1.15 mm thick, was designed using polycaprolactone. The implant was placed in five patients with complex orbital fractures. The radius of the sphere in contact with the orbit, measuring 33.54 mm, was confirmed to be appropriate. A comparison between the normal side volume (V0) and the postoperative volume (V_post ) showed that they were statistically similar. Furthermore, a comparison between V0 and the preoperative volume (V_pre ), and V_post compared with V_pre also showed a statistically significant difference (P < 0.05). On follow-up, the preoperative ocular symptoms were resolved. The orbital data obtained from 100 cadavers provided standardized orbital anatomy, and 3D printed implants were created. The implants were anatomically accurate with regard to the orbital cavity and adequately covered the simulation model. The implant also showed satisfactory results when applied clinically in actual patients.

Maxillofacial reconstruction with Medpor porous polyethylene implant: a case series study

Objectives

The role of alloplastic materials in maxillofacial reconstruction is still controversial. Determining the utility of porous, high-density, polyethylene implants as a highly stable and flexible, porous alloplast, with properties such as rapid vascularization and tissue ingrowth, is crucial in cases of maxillofacial deformities and aesthetic surgery.

Materials and Methods

Thirty high-density porous polyethylene implants were implanted in 16 patients that had been referred to a private office over a three-year period. These implants were used for correcting congenital deformities, posttraumatic defects and improving the aesthetic in nasal, paranasal, malar, chin, mandibular angle, body and orbital areas.

Results

The outcomes of the cases in this study showed good aesthetic and functional results. The majority of patients had no signs of discomfort, rejection or exposure. Two implants suffered complications: a complicated malar implant was managed by antibiotic therapy, and an infected mandibular angle implant was removed despite antibiotic therapy.

Conclusion

Based on the results, the Medpor implant seems to be an excellent biomaterial for correcting various facial deformities. Advantages include its versatility and relatively ideal pore size that allows for excellent soft tissue ingrowth and coverage. It is strong, flexible and easy to shape.

Extra-ocular movement restriction and diplopia following orbital fracture repair

PURPOSE

To report a series of patients with extra-ocular movement restriction and diplopia after orbital fracture repair, and determine the effect of timing of repair and the type of implant used.

METHODS

A chart review was conducted identifying all patients >18years of age at our institution between June 2005 and June 2008 who underwent orbital fracture repair, and presented with clinically significant diplopia and extra-ocular movement restriction persisting longer than one month after repair. Data collected included timing of repair, implant used within the orbit, and need for revision.

RESULTS

Ten patients were identified with a mean time to primary orbital fracture repair at 9days (range 1-48). Seven patients underwent revision of their orbital fracture repair with removal of the previously placed implant and replacement with non-porous 0.4mm Supramid Foil, whereas one patient underwent lateral and inferior rectus recessions without revision of primary fracture repair. Titanium mesh was the intra-orbital implant found in all patients requiring revision of orbital fracture repair. All revisions resulted in resolution of clinically significant diplopia.

CONCLUSIONS

Clinically significant diplopia and extra-ocular movement restriction is not an uncommon complication after orbital fracture repair. In our series, there was a strong association between these complications and the use of porous titanium mesh implants. Revision of fractures significantly improved diplopia in all but one patient. This suggests that meticulous fracture repair and the use of non-porous implants primarily or secondarily may preclude the need for strabismus surgery after orbital trauma.

Fenestration of Solid Orbital Implants: Reducing Retrobulbar Hematoma Rate

PURPOSE

Retrobulbar hematoma is an uncommon but potentially devastating complication following repair of orbital fractures. Since 2007, the senior author routinely fenestrates the solid porous polyethylene implants commonly used for orbital reconstruction. The perforated implant may facilitate drainage of postoperative bleeding and may potentially reduce the risk of retrobulbar hematoma. This study examines the rates of retrobulbar hematoma in patients who underwent orbital fracture reconstruction with placement of fenestrated or nonfenestrated implants.

METHODS

A retrospective chart review of patients with orbital fracture reconstruction using an implant performed by the senior author between 2006 and 2016 was conducted. Data collected included age, sex, implant type, and presence of retrobulbar hematoma.

RESULTS

One hundred four patients were included in the study. One patient who was treated with a nonperforated implant was found to have a postoperative retrobulbar hematoma. The retrobulbar hematoma did not cause visual changes or increased intraocular pressure, so the patient was observed and did not undergo any surgical intervention. The hematoma resolved spontaneously without further sequela. No patients with fenestrated implants had a retrobulbar hematoma.

CONCLUSIONS

Fenestration of solid implants used in orbital floor reconstruction is simple and easy to perform, and may reduce the incidence of postoperative retrobulbar hematoma.

Postoperative Complications in Craniomaxillofacial Reconstruction With Medpor

Bone reconstruction in craniofacial surgery is a challenge for surgeons, who most commonly adopt the autogenous bone grafting and alloplastic implants in such procedures. Among the alloplastic materials, the high-density porous polyethylene is highlighted-Medpor (Medpor, Porex Surgical Inc, Newman, GA), considered to be pure polyethylene, with only 1 manufacturing process and standard pore size. The purpose of the current study has been to present through a review of literature and the types of complications derived from the use of Medpor in craniomaxillofacial bone surgery. A specific and sensitive database was initially created via PubMed, focusing on studies published in English peer-reviewed journals between 2004 and 2014, including case reports, experimental studies in humans, and prospective and retrospective studies. Forty articles were found at PubMed database. After analyzing their abstracts, 19 were selected, totaling 1453 patients and 121 complications, being the most commonly reported diplopia with 56 patients and infection with 6 patients. Most of the complications reported in the articles used for the development of the current review are not directly related to the use of the Medpor implant. The only complications directly related to the use of this biomaterial were cases of infection.

Is there an ideal implant for orbital reconstructions? Prospective 64-case study

The aim of this study was to compare the effectiveness of porous polyethylene, titanium mesh, and castor oil-derived biopolymer randomized in orbital reconstructions of defects larger than 1 cm in length on the inferior and medial walls. A total of 63 patients (64 orbits) were evaluated to determine the presence of diplopia, enophthalmos ocular motility, and infraorbital nerve paraesthesia in both the preoperative and postoperative periods. The surgeons' opinions of the ease in handling the implants were also obtained after each procedure. The patients were divided into 3 groups: 17 received porous polyethylene, 21 received castor oil-derived biopolymer, and 26 received titanium mesh. In the preoperative period, 30 patients experienced enophthalmos, 11 experienced diplopia, and 12 experienced ocular motility. Ninety days after the orbital reconstruction, 6 cases of enophthalmos persisted, as did 2 cases of diplopia and 2 cases of ocular motility. Ten patients developed some type of postoperative complication. Material removal was required in only 1 case. Regardless of the size of the defect, the materials used were found to be effective for reconstructing orbital volume; they were also found to offer ease in handling and stabilization.

Reconstruction of Inferior Orbital Wall Fractures Using Bone Fragments

INTRODUCTION

Various materials have been used as implants in orbital floor fractures. The fractured bone fragments, however, are not usually used because of their small size and delicate characteristics. To overcome this limitation, the authors used autologous bone fragments combined with fibrin glue and an absorbable plate to repair inferior orbital wall fractures.

METHODS

Thirty-four patients with orbital floor fractures treated in a single center from January 2013 to September 2014 were prospectively evaluated. Patients' demographic characteristics, clinical signs and symptoms, physical examination findings, postoperative complications, and preoperative and postoperative computed tomography findings were assessed. Fracture repair by a transconjunctival approach in which bone fragments were merged with fibrin glue and an absorbable plate was performed in all the patients.

RESULTS

Postoperative computed tomography showed good orbital fracture reduction and soft tissue restoration in all the patients. Five patients developed postoperative diplopia; however, this symptom resolved spontaneously. Exophthalmometry showed that the degree of enophthalmos had improved significantly.

CONCLUSION

Based on the results of this study, the combination of autologous bone fragments and absorbable mesh appears to be a safe and feasible option for the reconstruction of orbital floor fractures.

Combination of absorbable mesh and demineralized bone matrix in orbital wall fracture for preventing herniation of orbit

After restoration of orbit wall fracture, preventing sequelae is important. An absorbable mesh is commonly used in orbit wall fracture, yet it has limitation due to orbit sagging when bony defect is larger than the moderate size (1 × 1 cm2). In this study, the authors present a satisfactory result in treating orbit wall fracture larger than the moderate size with a combination of absorbable mesh and demineralized bone matrix.From 2009 to 2012, 63 patients with bony defect larger than the moderate size, who were treated with a combination of absorbable mesh and demineralized bone matrix, were reviewed retrospectively. The site of bony defect, size, and applied amount of demineralized bone matrix were reviewed, and a 2-year follow-up was done. Facial computed tomography scans were checked preoperative, immediate postoperative, and 2-year postoperative.Among the 63 patients, there were 52 men and 11 women. Mean age was 33.3 years. The most common cause was blunt blow (35 cases); mean defect size was 13.36 × 12.82 mm2 in inferior wall fracture and 20.69 × 14.41 mm2 in medial wall fracture. There was no complication except for 3 cases of infraorbital nerve hypoesthesia. A 2-year follow-up computed tomography showed that the surgical site preserved bony formation without herniation. In treating moderate-sized bony defect in orbit wall fracture, absorbable mesh and demineralized bone matrix can maintain structural stability through good bony formation even after degradation of absorbable mesh.

High-density porous polyethylene wedge implant in correction of enophthalmos and hypoglobus in seeing eyes

INTRODUCTION

To report the results of post-traumatic enophthalmos/hypophthalmos correction with high-density porous polyethylene wedge implants in seeing eyes.

METHODS

This is an interventional case series of 25 patients (25 eyes) with post-traumatic enophthalmos and hypophthalmos, who underwent orbital reconstruction to correct the enophthalmos and hypophthalmos using Medpor® wedge implant. The aim was an overcorrection of 1 mm in comparison to the other eye, intra-operatively. If needed, trimming of the wedge implant or adding Medpor® sheets were used to achieve the goal. Success was defined as achieving the globe position within 1 mm of the other eye in the last follow-up. Improvement and failure were considered as correction outside the success range of 1 mm and no change in the amount of enophthalmos/hypophthalmos, respectively.

RESULTS

Patients were followed for at least 6 months (mean= 12.66, SD= 12.32). Success, improvement and failure of enophthalmos correction were: 58.3% (14/24), 37.5% (9/24) and 1 (1/24, 4.1%), respectively. Success, improvement and failure of hypophthalmos correction were 73.68% (14/19), 15.78% (3/19) and 5.26% (1/19), respectively. There was no significant difference between the success rate of enophthalmos versus hypophthalmos correction (P= 0.8). Results of 1-month follow up change in enophthalmos and hypophthalmos significantly correlated (r= 0.92, P= 0.000) with the change recorded at last follow up.

CONCLUSIONS

Porous polyethylene wedge implants are useful and safe in correction of enophthalmos and hypoglobus in seeing eyes. Appropriately positioned implant yields no significant difference in correction of enophthalmos versus hypophthalmos.

[Porous polyethylene implants for ear reconstruction of middle to high-grade ear defects]

The incidence of middle to high-grade ear malformations in Germany is approximately 150 per year. For many years autologous rib cartilage has been used for ear reconstruction as a framework material. In spite of a good biocompatibility of autologous rib cartilage there are potential risks of framework deformity as well as donor site morbidity. The advantages of osseo-integrated implants have provided patients with predictable esthetic results, durability and improved retention of the ear prostheses. Porous polyethylene ear implants (Medpor®) have been used for over 20 years as a suitable framework material. The advantages of this promising technique are good biocompatibility, short hospitalization time and the possibility of a one-step reconstruction of total or subtotal ear defects. The reconstruction of ear malformations with porous polyethylene ear implants is possible even in patients over 6 years old. Moreover, polyethylene promotes revascularization due to its porous structure, resulting in a good incorporation at the implantation site. The use of porous polyethylene ear implants permits a more expedient, less invasive and reliable reconstruction in moderate or high-grade ear malformations with very convincing results.

Treatment of orbital fractures: evaluation of surgical techniques and materials for reconstruction

Reconstruction of the fractured orbit serves to prevent functional and aesthetic posttraumatic sequels. In 2004, the surgical protocol at our unit was modified with respect to techniques for surgical access, types, and materials for reconstruction. The modifications were as follows: (a) introduction of medial orbital wall reconstructions through a bicoronal approach, (b) transconjunctival approach instead of the subciliary approach, and (c) porous polyethylene or porous polyethylene-titanium instead of autologous bone grafts. To evaluate the different surgical techniques and materials used, orbital reconstructions performed at our unit from 2000 to 2007 were retrospectively studied. In total, 177 primary or first-time secondary reconstructions were performed in 176 patients. The overall rate of early complications requiring medical or surgical intervention was 6.4%, and the reoperation rate was 3.4%. There were no statistically significant differences in the frequency of cicatricial eyelid complications between the subciliary and the transconjunctival approaches. There was a reduction in operative time with the use of implants compared with the use of bone. The overall rate of infections was 2%; however, there were no infections in the group treated with implants. Seven patients had secondary surgery for persistent enophthalmos, 4 of them due to defects in the medial orbital wall that had not been corrected at the time of primary reconstruction of the orbital floor. In conclusion, porous polyethylene/porous polyethylene-titanium is a safe material for orbital reconstructions. Reconstruction of the medial orbital wall is important to prevent posttraumatic enophthalmos, particularly in combined medial wall-orbital floor fractures.

Construction of tissue engineered nerve grafts and their application in peripheral nerve regeneration

Surgical repair of severe peripheral nerve injuries represents not only a pressing medical need, but also a great clinical challenge. Autologous nerve grafting remains a golden standard for bridging an extended gap in transected nerves. The formidable limitations related to this approach, however, have evoked the development of tissue engineered nerve grafts as a promising alternative to autologous nerve grafts. A tissue engineered nerve graft is typically constructed through a combination of a neural scaffold and a variety of cellular and molecular components. The initial and basic structure of the neural scaffold that serves to provide mechanical guidance and optimal environment for nerve regeneration was a single hollow nerve guidance conduit. Later there have been several improvements to the basic structure, especially introduction of physical fillers into the lumen of a hollow nerve guidance conduit. Up to now, a diverse array of biomaterials, either of natural or of synthetic origin, together with well-defined fabrication techniques, has been employed to prepare neural scaffolds with different structures and properties. Meanwhile different types of support cells and/or growth factors have been incorporated into the neural scaffold, producing unique biochemical effects on nerve regeneration and function restoration. This review attempts to summarize different nerve grafts used for peripheral nerve repair, to highlight various basic components of tissue engineered nerve grafts in terms of their structures, features, and nerve regeneration-promoting actions, and finally to discuss current clinical applications and future perspectives of tissue engineered nerve grafts.

Update on orbital reconstruction

PURPOSE OF REVIEW

Orbital trauma is common and frequently complicated by ocular injuries. The recent literature on orbital fracture is analyzed with emphasis on epidemiological data assessment, surgical timing, method of approach and reconstruction materials.

RECENT FINDINGS

Computed tomographic (CT) scan has become a routine evaluation tool for orbital trauma, and mobile CT can be applied intraoperatively if necessary. Concomitant serious ocular injury should be carefully evaluated preoperatively. Patients presenting with nonresolving oculocardiac reflex, 'white-eyed' blowout fracture, or diplopia with a positive forced duction test and CT evidence of orbital tissue entrapment require early surgical repair. Otherwise, enophthalmos can be corrected by late surgery with a similar outcome to early surgery. The use of an endoscope-assisted approach for orbital reconstruction continues to grow, offering an alternative method. Advances in alloplastic materials have improved surgical outcome and shortened operating time.

SUMMARY

In this review of modern orbital reconstruction, several controversial issues such as surgical indication, surgical timing, method of approach and choice of reconstruction material are discussed. Preoperative fine-cut CT image and thorough ophthalmologic examination are key elements to determine surgical indications. The choice of surgical approach and reconstruction materials much depends on the surgeon's experience and the reconstruction area. Prefabricated alloplastic implants together with image software and stereolithographic models are significant advances that help to more accurately reconstruct the traumatized orbit. The recent evolution of orbit reconstruction improves functional and aesthetic results and minimizes surgical complications.