Paranasal augmentation using Medpor® implant and changes in lateral profile

Introduction

In mandibular prognathism, depression of the midfacial area is also seen in many cases, and various methods have been introduced to improve this situation. In particular, convexity in the 1/3 area of the midface plays an important role in a young- looking appearance [1]. Additionally, a concave face has been considered to be less attractive than a convex face [2,3]. In cases with depression in the midface, it can be corrected by performing maxillary advancement [4]. However, in cases with simple depression of the midfacial area, if it is corrected by such

maxillary advancement, preoperative orthodontic treatments are required, and the burden of surgery, the complexity of the surgery, and the financial burden on the patient may be substantial.

However, in paranasal augmentation cases, the effect of enlarging the midfacial skeleton can be achieved by simple surgery, and visual effects similar to maxillary advancement by osteotomy can be obtained. Augmentation of the nasal area can be performed using, for example, artificial graft materials or autologous bones. In cases using autologous bone, augmentation surgery is typically performed using the ileum or the cranium. Nevertheless, it has shortcomings in that a second surgery area is needed, and resorption can occur [5].

Thus, various artificial graft materials have been developed, and until now, various artificial graft materials have been used in paranasal augmentations. Among the various artificial graft materials, the Medpor

surgical implant (Porex Surgical, Newnan, GA, USA) is widely used and is available in various

Paranasal augmentation using Medpor ^® implant and changes in lateral profile

Jae-Seek You, Su-Gwan Kim*, Ji-Su Oh, Kyung-Seop Lim, Seung-Min Shin, Cheol-Man Kim

Department of Oral and Maxillofacial Surgery, School of Dentistry, Chosun University, Gwangju, Korea

ABSTRACT

Purpose: The purpose of this study was to simultaneously evaluate soft tissue changes induced by bilateral sagittal split osteotomy of the mandible as well as paranasal augmentation using a Medpor

implant based on cephalometric radiography before and 6 months after surgery.

Materials and Methods: We analyzed the increase in soft tissue volume in 20 patients diagnosed with mandibular advancement and midfacial depression between Feburary 2005 and Feburary 2009. Paranasal augmentation was performed using a 4.5mm-thick Medpor

implant, and lateral head radiographs were analyzed before and 6 months after surgery.

Results: The increase in soft tissue volume was 3.27±1.16 mm, which was 72.67% of the actual thickness. After surgery, no particular complication was detected, and the results were acceptable to the patients and surgeons. Based on these results, the Medpor

implant is a satisfactory artificial graft material for use in facial augmentation.

Conclusion: Paranasal augmentation using the Medpor

implant can be considered a good surgical option that can maximize the aesthetics of a patient’s face.

Key Words: Medpor, Paranasal augmentation, Lateral profile

Received Aug 27, 2013; Revised version received Sep 4, 2013 Accepted Sep 5, 2013

Corresponding author: Su-Gwan Kim

Department of Oral and Maxillofacial Surgery, School of Dentistry, Chosun University, 309 Pilmun-daero, Dong-gu, Gwangju 501- 759, Korea

Tel: 82-62-220-3819, Fax : 82-62-228-7316

E-mail : [email protected]

shapes so that it can be grafted stably in the surgery area [6].

Thus, in patients having mandibular prognathism with accompanying depression of the midfacial area, we performed a bilateral sagittal split osteotomy of the mandible and paranasal augmentation using the Medpor

simultaneously, and soft tissue changes were compared based on cephalometric radiography before and 6 months after surgery.

Materials and Methods

Study subjects

This study was conducted in 20 patients diagnosed with mandibular prognathism and midfacial depression in the Department of Oral and Maxillofacial Surgery, Chosun University Dental Hospital, between February 2005 and February 2009. They were treated with a bilateral sagittal split osteotomy of the mandible and paranasal augmentation using the Medpor

simultaneously. Of the patients, 11 were males and 9 were females. Cephalometric radiography was conducted prior to surgery, and at the follow-up observation 6 months after surgery (Table 1). The general condition of the patients

was ASA class I.

Surgical methods

After performing a bilateral sagittal split osteotomy of the mandible under general anesthesia by an oral approach, paranasal augmentation was performed under local anesthesia induced with lidocaine (containing epinephrine diluted to 1 : 100,000) using the 4.5-mm-thick Medpor

implant.

An incision was made in the buccal vestibular area in the

Table 1. Soft Tissue Changes Were Compared Based on Cephalometric Radiography before and 6 Months after Surgery

Patient Sex/age FH & N (mm) (pre op.) FH & N (mm) (post op.) Augmentation (mm) 1

2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20

Mean±standard deviation

F/25 F/23 F/27 M/22 F/24 F/34 M/22 M/28 M/44 M/29 F/25 F/24 M/25 M/22 F/25 F/23 M/27 M/30 M/21 M/28

0.50 5.73

−3.80 4.75 8.10 5.44 1.84 7.78 8.15 4.50 2.15 0.00 2.20 4.88 6.60 6.37 3.30 4.50

−2.50 3.00 3.67±3.32

4.12 9.14 0.50 7.23 11.74 8.73 2.93 9.27 9.60 7.72 5.00 5.46 5.14 7.49 9.82 9.34 6.34 8.30 3.30 6.67 6.89±2.80

3.62 3.41 4.30 2.48 3.64 3.29 1.09 1.49 1.45 3.22 2.85 5.46 2.94 3.61 3.22 2.97 3.04 3.80 5.80 3.67 3.27±1.16

FH & N: The distance from McNamara line to maximal protruding area of the paranasal soft tissue, pre op.: preoperative, post op.: postoperative, F:

female, M: male.

Fig. 1. The Medpor

was positioned.

maxillary anterior region, and the area next to the piriform aperture where a 4.5-mm-thick Medpor

would be located was exposed by subperiosteal dissection. Then, fixation of the 4.5-mm-thick Medpor

was performed using two circular round miniplates and screws. This was performed to fix the device accurately, as well as to prevent movement during the initial period after surgery. It is also advantageous for covering by soft tissues and preventing changes in position (Fig. 1). After positioning the Medpor

, the incision area was sutured by a layer-to-layer technique, and to prevent postsurgical hematomas, a compression dressing was applied.

Research methods

Similar to a study by Kim et al. [7] in the maximal protruding area of soft tissues, the distance to the McNamara line was measured. The lateral head radiographs were taken prior to surgery and 6 months after surgery, printed as 1 : 1 size, and the distance to the McNamara line was measured in the maximal protruding area of the paranasal soft tissues. Subsequently, the volume of the change in the thickness of soft tissues was calculated (Fig. 2).

Results

Patients

The patients consisted of 11 males and 9 females. No

significant difference was seen between male and female patients.

Complications

No infection or other complication, such as dysesthenia, was observed. In one case, 6 months after implanting the 4.5-mm- thick Medpor

, the changed volume of soft tissues was shown to be 5.8 mm, which was thought to be the result of slight edema.

Measurements

Prior to and at 6 months after surgery, in the maximal protruding area of paranasal soft tissues, the distance to the McNamara line was measured on lateral head radiographs, and the volume of the lateral change after using the 4.5 mm-thick Medpor

was 3.27±1.16 mm.

Discussion

Severe midfacial depression is seen frequently in, for example, Apert and Crouzon syndrome. In such cases, not only malocclusion results, but it may also mediate effects on the protection of the eye and security of the airway. In such midface depression cases, the disharmony of occlusal and respiratory function are treated and the esthetic of the face is improved by performing an osteotomy, applying the LeFort I or III [8].

Nevertheless, a mild level of underdevelopment of the midface is a relatively frequent facial skeletal variation. In cases with such skeletal variation of the face, respiratory or visual problems rarely occur, and thus maxillary advancement by osteotomy is not essential. In cases with midface development without relatively severe malocclusion, osteotomy and other treatment plans are expensive in terms of time and cost, and problems may develop in such a complex surgery. In such cases, if paranasal augmentation using artificial graft materials or autologous bone is performed, visual effects comparable to maxillary advancement can be obtained. In cases using autologous bones, problems in the generation of the second surgery area and resorption have been reported. Thus, presently, paranasal augmentation using artificial graft materials are commonly performed.

Many studies on such artificial graft materials have been reported, and satisfactory results in facial augmentation have been obtained using soft Gore-Tex

(W.L. Gore & Associates, Fig. 2. The volume of the change in the thickness of soft tissues was

calculated in the lateral head radiographs (McNamara line).

Flagstaff, AZ, USA), Proplast, and coralline hydroxyapatite [9,10]. However, shortcomings of such graft materials have been occasionally reported. In soft silicone cases, the vascularizational potential between graft materials is not sufficient; it induces underlying bone resorption, and in long- term follow-up observation, a tendency for the migration of graft materials was shown [11]. In Gore-Tex

cases, it is unstable due to the lack of proliferation to host tissues, and side effects, such as infection, seroma formation, and extrusion, have been observed [12]. Presently, Proplast is rarely used because of antigenic reactions and possible infection [13], and hydroxyapatite can readily be damaged or destroyed during loading [14].

The graft material used in this study was the Medpor

implant composed of porous high-density polyethylene.

Porous polyethylene is not degraded in the tissue fluid and resorption does not occur. It has been used as an onlay material in the facial skeleton, and its structural stability has been demonstrated in long-term studies [15-17]. Additionally, in histological studies, destruction of graft materials was not observed, and foreign body reactions are minimal [18,19].

Because of such stability, polyethylene has been used as a standard material in biocompatibility testing [20].

The size of the micropores in the Medpor

is 100-250 µm, and the pore volume accounts for 50% of the entire volume. In the porous polyethylene structure, the pores are connected in the interior, and in animal studies, tissues have been shown to grow within pores larger than 100 µm. If the pore size is smaller than 100 µm, tissue growth is restricted, and if the pore size is too big, destruction of the material may be induced [13,21].

Additionally, tissues proliferate in such pores, and fibrous encapsulation occurs less than in graft materials with smooth surfaces [19].

Medpor

is advantageous in that it shows non-antigenicity, non-resorption, and high stability. It can be fixed readily, and it can be used in many sites without loading [22].

In this study, similarly, when the Medpor

was used, satisfactory results were obtained at the 6-months follow-up observation, without specific complications. During surgery, fixation was performed using circular metal plates and screws to connect the graft materials to the inferior bone by fixating, allowing no movement of the graft materials. Additionally, this was to prevent the induction of the unexpected augmentation

volume by eliminating space between graft materials and bones and thus blocking any intercalation of soft tissues.

In 1993, Wellisz [19] used Medpor

for the reconstruction of the maxillofacial area, such as the ear, buccal, nasal, and orbital areas, and reported complications in nine of 116 cases.

In 1996, Semergidis et al. [23] reported that in patients with severe facial deformity, the atrophic mandibular angle was reconstructed using the Medpor

in four cases, and satisfactory results were obtained. Additionally, Rubin et al. [24] reported that using sheet-type Medpor

, reconstruction of the inner orbit was performed in 37 cases. Also, in 27 diplopia patients, the condition was resolved in 15 patients, and in 18 cases with depression of the eye socket, nine patients were cured.

In 2003, Yaremchuk [20] reported that over 11 years, various reconstructions in the orofacial area were performed using 370 Medpor

implants. Infection associated with the prosthesis developed in only four patients, and they mentioned that porous polyethylene was biocompatible and suitable for facial skeletal augmentation. Additionally, Yaremchuk [8] reported that using three Medpor

implants from the lower margin of the eye to the paranasal area, surgery to render the midfacial skeleton convex was performed in 14 patients over 4 years, and the device was stable and effective.

In addition, in 2009, based on studies performed in the

reconstruction of the craniofacial area using bones and graft

materials over 11 years, Neovius and Engstrand [25] reported a

retrospective study. Their results showed that in reconstruction

using porous polyethylene, the incidence of complications was

diverse, from 0 to 29%, and the most common complications

were exposure of the graft material and infection. Menderes

et al. [26] reported a higher incidence of complications in

certain areas: 2 of 3 patients in nasal reconstruction cases,

1 of 3 patients in ear reconstruction, and 1 of 14 patients in

mandibular reconstruction. Based on such complications,

Gosau et al. [27] mentioned shortcomings of Medpor

. From

2001 to 2005, in 27 patients undergoing facial augmentation,

48 Medpor

implants were used. Among them, in cases that

developed local infection and in cases in which resurgery

was performed, 10 samples were collected and histological

examinations were performed. The results showed that in

immunohistochemical staining for CD68, macrophages and a

foreign body reaction were detected, and the study suggested

that Medpor

should not be considered an immunologically

inert material.

Similarly, in this study, in one case, 6 months after the use of the 4.5 mm-thick Medpor

, the volume of the change in soft tissues was 5.8 mm. Macroscopic findings did not suggest that the graft materials should be removed. Nonetheless, as mentioned previously, the edema may have been caused by a foreign body reaction in the area of the transplanted graft materials.

When artificial graft materials such as Medpor

are used, predicting the augmentation of the facial area is important. As mentioned previously, numerous studies have been conducted using Medpor

; nonetheless, few reports have described the changed volume of soft tissues.

Kim et al. [7] reported that paranasal augmentation was performed using 3 mm-thick Medpor

, and 6 months after surgery, the increased volume of soft tissues was shown to be 2.46±0.27 mm; the increased volume of the soft tissues was 82.1% of the actual thickness, and the results satisfied both the patient and the surgeon.

In this study, similarly, prior to and at 6 months after surgery, in the maximal protruding area of soft tissues in the paranasal area, the distance to the McNamara line was measured on lateral head radiographs; after the use of 4.5 mm-thick Medpor

, the changed volume of lateral soft tissues was 3.27±

1.16 mm, and the increased volume of soft tissues was 72.67%

of the actual thickness. No particular postsurgical complication developed; nevertheless, in one case, 6 months after the use of the 4.5 mm-thick Medpor

, the changed volume of soft tissues was 5.8 mm. The patient did not present with particular discomfort and no infection was detected. All patients were satisfied with the surgery outcome. This success is considered to be the result of selecting the appropriate indication prior to surgery, fixation in a precise position, the use of circular mini-metal plates and screws to prevent movement during the early period after surgery, the use of compression dressings to prevent postsurgical hematomas, and the administration of appropriate antibiotics.

If the appropriate indication is selected and appropriate surgery and postsurgical management are achieved, paranasal augmentation using the Medpor

is considered to be a good surgical option that can maximize the esthetics of the patient’s face, which is the major aim of temporal correction, by a simple procedure.

Acknowledgments

This study was supported by research fund from Chosun University, 2013.

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