Alloplastic augmentation of the mandibular angle

J Oral Maxillofac 54:1417-1423,1996

Surg

Alloplastic Augmentation Mandibular Angle THEMISTOCLES

of the

G. SEMERGIDIS, DDS, MD,* SALVATORE A. MIGLIORE, AND GEORGE C. SOTEREANOS, DMD$

DMDJ

Purpose: This article describes the use of a large-pore polyethylene implant for mandibular angle augmentation. Patients and Methods: Patients with severe facial deformities who had previously undergone multiple surgical procedures and were now seeking esthetic improvement were included in this series. Their deficient mandibular angles and reduced ramus height were corrected with polyethylene implants appropriately sculptured and fixed to the mandible through extraoral incisions that preexisted in most patients. The surgical technique is described, and four representative cases are presented that illustrate the changes in facial contour and esthetics. Results: Postoperative appearance was considered very satisfactory, and the patients’ esthetic expectations were met to a great extent. The mandibular angle was well outlined, and facial contour and proportions were enhanced. Conclusion: This surgical procedure is recommended for mandibular angle augmentation when proper indications are strictly observed and surgical steps are accurately followed.

Traditionally, focal points of interest for esthetic facial contouring have been mainly the malar-zygomatic and chin regions. Only a few references are available on mandibular angle modifications except for treating masseter muscle hypertrophy.‘.” The two main methods of bone contouring are osteotomies or insertion of implants of various types.5 In this article we present our experience with the use of large-pore polyethylene implants for alloplastic augmentation of the mandibular angle (AMA) and discuss the indications, operative steps, and clinical results. Preoperative

better definition and distinction from the neck line. The normal shadows of the mandibular border are necessary for a pleasing angle definition, conveying a feeling of something missing when they are not apparent.4,6 Preoperative evaluation in this group of patients is no different than the one used in orthognathic cases. Full documentation of the case is obtained through radiographs, three-dimensional computed tomography (CT) scans, and a complete set of photographs. Cephalometric analysis can be very useful, whereas appropriate clinical linear measurements are necessary for planning the type and size of the implants to be used. Patients seeking recontouring of their facial features are a very particular group and must be dealt with as such from the very beginning of their treatment. They are strongly motivated, and most of them have an exact idea about the requested morphologic change. The deformities addressed are perceived by the patient, and the surgeon may sometimes have reservations concerning the necessity of correcting them. Evaluation of the psychosocial background and the anticipated benefits must be weighted against the risk involved in an elective operation. Many of the patients who need or desire an AMA procedure have had previous surgery, either cosmetic or reconstructive. Their main complaints refer to the disappearance of their ‘jawline,” “shalof the face, and poor jaw-neck definition. lowness”

Considerations

From the esthetic point of view, the angle should be long and low in profile, and less than 10.5” to create

From the Division of Plastic, Reconstructive and Oral-Maxilofacial Surgery, Department of Surgery, University of Pittsburgh, Pittsburgh, PA. * Fellow, Oral and Maxillofacial Surgeon. t Visiting Professor, Orthodontist, Craniomaxillofacial Program, $ Associate Professor. Address correspondence and reprint requests to Dr Sotereanos: 6B Scaife Hall, 3550 Terrace St, Pittsburgh, PA 15261. 0 1996 American

Association

of Oral and Maxillofacial

Surgeons

0278-2391/96/5412-0006$3.00/O

1417

ALLOPLASTIC

1418

B

FIGURE 1 Diagram showing the procedure for augmenting the mandibular angle. A, Obtuse mandibular gonial angle. B, Preshaped alloplastic implant. C, Fixation of the implant to the lateral surface of the mandible.

Clinically they present with an obtuse mandibular angle, not necessarily combined with any occlusal anomalies. In fact, most of these patients are not candidates for orthodontic or conventional orthognathic treatment, their only cephalometric deviation being the diminished posterior facial height. Technique The procedure is performed under general anesthesia. The preferred approach is extraoral through a submandibular incision placed either in a preexisting scar or in a neck skin crease. The patient is not paralyzed so that the surgeon can determine the course of the marginal mandibular branch of the facial nerve in the superiorly elevated skin-platysma flap with the use of the nerve stimulator. When the dissection has reached the inferior border of the mandible, the pterygomasseteric sling is divided and the periosteum is elevated to expose the lateral surface of the angle and the ascending ramus. The extent of the dissection superiorly is dictated by the volume of the implant to be inserted, allowing adequate spacefor intraoperative maneuvers, because the implant must be fitted on site. Medpor (Porex Surgical, College Park, GA) porous polyethylene implants, available in preformed anatomic shapes, are used as onlays straddling the posterior and inferior border of the mandible at the gonial angle (Fig 1). The implants are soaked under pressure in a broadspectrum antibiotic solution (amoxicillin) before insertion, and care is taken throughout the procedure to avoid contamination of the implant. Heating by immersion in hot sterile saline can help in adapting the implant to a desired shape, which is maintained after cooling. The implant is also sculptured with a no. 10 surgical blade on a rigid flat surface and reinserted as

AUGMENTATION

OF THE MANDIBULAR

ANGLE

many times as necessary until it is completely adapted to the lateral surface of the mandible. The edges are feathered in a way that the margins cannot be palpated through the overlying tissues, and the superior and anterior portions are trimmed until the implant seems to compensatefor the preexisting defect after redraping the elevated flap. When the esthetics are considered satisfactory from all views, the implant is rigidly fixed to the mandible with two or three 2-mm titanium screws of adequate length, avoiding injury of the inferior alveolar neurovascular bundle (Fig 1C). The pterygomasseteric sling is repaired with nonabsorbable sutures, and the wound is closed in layers after placement of a vacuum drain. The sameprocedure is performed on the contralateral side. The difference is that now the goal is to achieve symmetry with the corrected side. When surgery is completed, a pressure dressing is applied, and the patient is taken to the recovery room in an elevated head position, which, in combination with ice packs, can decrease the edema in the region. The intraoperatively administered broad-spectrum antibiotic (amoxicillin) is continued for 10 days postoperatively, and the patients generally can resume their usual activities in a week. Patients

and Methods

Eighteen patients (14 women, four men), aged between 43 and 58 years, had their deficient mandibular angle region corrected with alloplastic AMA over a 3year period (1992 to 1995) at the University of Pittsburgh Medical Center. Follow-up time ranged between 6 months and 3 years. Four selected casesillustrating the technique and the results are presented. Report of Cases Case 1 A 43-year-old woman with congenitalectodermicdysplasia syndromepresentedwith a hypoplastic mandible and maxilla as well ascleft lip and palate. She had undergone a significant number of major surgical procedures in the past 7 years (multiple osteotomies in 1988, calvarial bone grafting with temporalis flap and alloplastic malar augmentation in 1993, dental implant placement in 1994). At this point the patient was scheduled for mandibular angle augmentation with alloplastic implants. An extraoral approach through preexisting submandibular incisions was used, and the final result was very satisfying to the patient 1.5 years later (Fig 2).

Case 2 A 58-year-old woman had a long history of previous surgeries after an attempt was made in 1970 to surgical correct a malocclusion secondary to trauma. She subsequently underwent bimaxillary orthognathic procedures in 1980 for her open bite correction and genioplasty in 1990. Currently, she

SEMERGIDIS,

MIGLIORE,

AND SOTEREANOS

FIGURE 2. Case 1. Patient with congenital malformation (ectoderma1 dysplasia syndrome) who has undergone multiple orthognathic and bone grafting procedures. A, Lateral view of the patient showing lack of definition of the mandibular angle. B: Implant adapted to the lateral surface of the mandible. C; Postoperative lateral view of the patient showing augmentation of the angle.

wished correction of the diminished height and width of her face. Bilateral porous polyethylene implants were used for alloplastic augmentation of the mandibular angle through submandibular incisions, and the results were considered excellent by the patient 6 months postoperatively (Fig 3).

Case 3 A 45year-old man had a long history of reconstructive procedures after trauma. He has previously had a rib graft reconstruction of the left temperomandibular joint (TMJ)

1420

ALLOPLASTIC

AUGMENTATION

OF THE MANDIBULAR

ANGLE

FIGURE 3. Case 2. Patient with deficient angles after previous orthognathic surgery to correct residual deformity due to condylar fractures. A and B, Frontal and lateral views of the patient showing deficient mandibular angle regions. C and D, Postoperative frontal and lateral views of the patient showing esthetic restoration of mandibular contour.

and a second metatarsal free vascularized graft placed in the right TMJ. He complained of asymmetry in the region of the mandibular angle and reduced bigonial distance. Polyethylene implants of appropriate size were placed at the mandibular angles, and facial contour was restored in an esthetically pleasing manner when examined 8 months postoperatively (Fig 4). Case 4 A 49-year-old woman presented with a history of a congenital facial skeletal anomaly and traumatic injury. She had sus-

tamed a mandibular fracture in 1984 that was treated with iliac crest bone grafting, and hydroxylapatite ridge augmentation at a later date. Subsequently the patient underwent a high zygomatic-maxillary osteotomy for midfacial deficiency in 1989, and recontouring of the mandible as well as dental implant reconstruction. At this point she wished correction of the obtuse and asymmetrical mandibular angles and augmentation of her malar prominences. The augmentation procedures were performed with the use of porous polyethylene implants that were appropriately modeled to restore facial contour. The results were deemed extremely pleasing by the patient and her family 10 months after surgery (Fig 5).

SEMERGIDIS,

MIGLIORE,

AND

SOTEREANOS

1421

FIGURE 4. Case 3. Patient with rib and free metatarsal grafts for mandibular reconstruction. A, Preoperative profile view showing defect in genial angle region. B, Intraoperative view of implant fixed in place. C, Postoperative profile view of the patient showing restoration of the gonial region.

Discussion Polyethylene implants have been used in maxillofacial surgery, mainly for posttrauma reconstruction,

since 198.5, and favorable results have been reported. The Medpor implant is a medical-grade, inert, radiolucent, high-density linear polyethylene, sintered to form a framework of interconnecting pores that allow rapid

1422

ALLOPLASTIC

FIGURE 5. Case 4. Patient with deficient angles following multiple view showing flat face and lack of mandibular contour. B, Profile view contour. Ma& augmentation was also performed.

tissue ingrowth.7-9 Pore size is controlled so that more than 50% of the pores are larger than 150 pm. Collagen deposited within the pore network forms a clinically stable complex resistant to contractile forces, making surgical removal difficult should it be necessary. The implant is easy to shape, strong, but flexible to a certain extent, and stable on a long-term basis, because there are reports of more than 30 years of follow-up.7,10 Its strength resists deformation of the pores, which are critical to vascularization of the implant. Tissue fluid is subsequently able to circulate throughout the contiguous large pore structure, and in this way defense mechanisms against infection are greatly enhanced.7 As an alternative to alloplastic facial contouring, which is considered a camouflage technique, traditional corrective bone surgery can also help some of these patients. However, osteotomies, autogenous onlay or interpositional bone grafts, and long periods of orthodontic treatment do not satisfy a patient demanding a relatively minor, fast, and simple procedureS6 Moreover, some patients present with inadequate quality and quantity of bone for the osteotomies needed (Case 1).

reconstructive of the patient

AUGMENTATION

OF THE

MANDIBULAR

ANGLE

procedures after facial trauma. A, Preoperative profile three weeks postoperatively showing well defined facial

Facial augmentation with alloplastic materials is a procedure with a relatively low incidence of reported complications. ‘,11 Incorrect choice of implant, error in placement, implant displacement, hematoma, and especially infection are the most common.12 Flammability of a polyethylene implant was reported recently as a potential intraoperative hazard, but it was probably caused by the use of diathermy on the implant, which is not recommended by the manufacturer.13 Other complications related to the AMA procedure include infection and extrusion, palpable edges of the implant, swelling, and possible resorption of underlying bone.1.4,6 Of those, the most important is infection, whereas the rest either unusual or not well documented. Whitaker’ in 1989 reported infection necessitating removal of the implant in 2 of 20 patients who had AMA with Proplast implants, and Aiache,4 who used silicone implants, reported two cases of mild infection resolved with antibiotics. We had no cases of infection in our patients. The main reason why an extraoral approach was used was to avoid cross-contamination of the implant by the oral flora. Most of these patients have undergone previous surgery and usually have subman-

SEMERGIDIS,

MIGLIORE,

AND

SOTEREANOS

dibular scars that permit access at no esthetic cost. When presented with patients complaining of esthetic problems, one should be cautious about those selected for surgery.‘4,‘5 To achieve success, external motivations related to social outcome and internal motivations related to self-esteem must be thoroughly evaluated and understood by the surgeon. Psychological evaluation may be necessary to detect significant psychopathology and to enable a safe prediction of the psychosocial outcome in these cases.14 References I. Whitaker LA: Aesthetic contouring of the facial support system. Clin Plast Surg 16:815, 1989 2. Epker BN: Augmentation, in Epker BN (ed): Esthetic Maxillofacial Surgery. Philadelphia, PA, Lea & Febiger, 1994, p 80 3. Baek SM, Kim S, Bindiger A: The prominent mandibular angle: preoperative management operative technique and results in 42 patients. Plast Reconstr Surg 83:272, 1989 4. Aiache AE: Mandibular angle implants. Aesthetic Plast Surg 16:349, 1992

1423 5. Salyer KE: Malar augmentation using lamellar split osteotomy. J Craniofac Surg 5:116, 1994 6. Ousterhout DK: Mandibular angle augmentation and reduction Clin Plast Surg 18:153, 1991 7. Wellisz T: Clinical experience with the MEDPOR porous polyethylene implant. Aesthetic Plast Surg 17:339, 1993 8. Klawitter JJ, Bagwell J, Weinstein, et al: An evaluation of bone growth into porous high density polyethylene. J Biomed Mater Res lo:31 1. 1976 9. Shaber EP: Vertical interposisional augmentation genioplasty with porous polyethylene. Int J Oral Maxillofac Surg 16:678, 1987 10. Rubin LR: Polyethylene as a bone and cartilage substitute: A 32 year retrospective, in Rubin LR (ed): Biomaterials in Plastic Surgery. St Louis, MO, CV Mosby, 1953, p 477 1 I. Hinderer UT: Nasal base, maxillary, and infraorbital implantsalloplastic. Clin Plast Surg l&87, 1991 12. Adams J, Kawamoto HK: Late infection following aesthetic malar augmentation with proplast implants. Plast Reconstr Surg 95:382, 1995 13. Short- N, Steinsapir K: Flammability of high-density porous polyethylene: A potential intraoperative fire hazard. Arch Ophthalmol 112: 1276, 1994 14. Pertschuk M: Psychosocial considerations in interface surgery. Clin Plast Surg 18:11, 1991 15. Edgerton MT, Langman MW, Pruzinsky T: Patients seeking symmetrical recontouring for “perceived” deformities in the width of the face and skull. Aesthetic Plast Surg 14:59, 1990