Correction of congenital malar hypoplasia using stereolithography for presurgical planning

512

CORRECTION

As with other purulent infections, adequate drainage was performed, and specimens were obtained for culture. Empirical treatment with an antibiotic was started immediately to prevent further spread; nevertheless, an infection occurred in the left middle ear, the submasseteric space, the left parapharyngeal space, and the left antrum so that a drainage of these spaces also was necessary. This treatment, and modified antimicrobial therapy on the basis of the culture, led to rapid recovery. Joints with underlying arthritic disease tend to be more susceptible to distant infection.’ In this patient, there was an internal derangement that was associated with degenerative changes in the TMJ. This could have been a predisposing factor.

OF

CONGENITAL

MALAFt

HYPOPLASIA

References 1. Murakami K, Matsumoto K, Iizuka T, et al: Suppurative arthritis of the temporomandibular joint: Report of a case with special reference to arthroscopic observation. J Oral Maxillofac Surg 12:41, 1984 NA, Levine RH, et al: Joint infection as a 2. McCain JP, Zabiegalski complication of temporomandibular joint arthroscopy: A case report. J Oral Maxillofac Surg 51:1389, 1993 of the temponnan3. Piecuch JI, Leiblich SE: Anatomy and pathology dibular joint, in Peterson IJ (ed): Principles of Oral and Maxillofacial Surgery, vol 3. Philadelphia, PA, Lippincott, 1992, pp 1857-1871 4. Leightym SM, Spach DH, Myall RW, et al: Septic arthritis of the temporomandibular joint: Review of the literature and report of two cases in children. Int J Oral Maxillofacial Surg 22:292, 1993 5. Estehai JL: Adult septic arthritis. J Onhop Clin North Am 22292, 1993

J Oral Maxillofac Surg 56512-517, 1998

Correction of Congenital Malar Hypoplasia Using Stereolithography for Presurgical Planning WalterJ James, DDS, MD, * Mark A. Slabbekoorn, DDS, MD, f WendellA. Edgin, DDS,# and Charles K. Hardin, MDf Stereolithography has recently been introduced as an adjunct to traditional methods of treatment planning for surgical correction of dentofacial deformities. Three-dimensional (3D) reformatting of computed tomography (CT) images has simplified visualization of maxillofacial deformities, but an accurate 3D model may better support patient education and informed

Received

from Wilford

*Formerly,

Chief

Hall Medical

Department

of Oral and Maxillofacial

Chairman,

Surgery,

Barksdale

AFB, LA.

TResident,

Department

*Assistant

Chairman

of Oral and Maxillofacial and Program

SDirector

of Craniofacial Surgery.

The views expressed

Address

Director,

Surgery. Department

of Oral

Surgery.

Reconstructive

Departments

AFB, TX.

of Oral and Maxillofacial

Currently,

not reflect

Lackland

Department

Surgery,

and Maxillofacial

Center,

Resident,

the official

Surgery,

in this article policy

Department

of Plastic

are those of the authors

of the Department

of Defense

and

and do or other

of the US Government. correspondence

and reprint

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Edgin:

MDW/DSCO, 2200 Bergquist Dr, Suite 1, Lackland AFB TX 78236. This is a US government work. There is no restriction on its use. 0278.2391/98/.5604-002

1$0.00/O

59

consent, preoperative analysis of spatial movements of bony structures, fabrication of templates for autogenous grafts, and postoperative analysis. Industrial applications for stereolithography have included 3D models for automotive marketing, part design and prototyping, and aerospace part prototyping, providing a significant decrease in time and expense from design to production of products.l,* Medical applications have included prototype models for orthopedic implant fabrication and diagnostic information for complex neurosurgical and maxillofacial procedures.3s4 The stereolithographic apparatus (SLA) consists of a helium-cadmium laser (20 to 40 mW, 325nm wavelength) with computer-controlled mirrors and a movable platform suspended in liquid ultraviolet (UV) light-sensitive epoxy resin. 3D CT reconstructions are formatted and transferred to the SLA microcomputer, which controls the movements of the laser beam at speeds up to 762 mm/set. On contact with the laser emission, a 0.006 to O.OlO-inch layer of polymerized resin is formed. The developing model is then incrementally submerged and the next layer polymerized to the first in the same fashion. The sequential formation of these layers forms the 3D model, which

JAMES ET AL

FIGURE 1. fabricated

on

Frontal

513

view

of

model

surgery

on

the

acrylic

skull

SLA250.

includes detailed anatomy of the skull (Fig 1). The model is cured with UV light for 45 minutes, which completes the last 20% of the polymerization process and provides final strength to the product.

Report

of Case

The stereolithographic technology was used for the treatment planning of a 16-year-old boy complaining of dissatisfaction with his asymmetrical facial appearance. Physical examination, cephalometric analysis, photographic evaluation, and dental model analysis were completed and found to be within normal limits with the exception of severe right zygomaticomaxillary complex (ZMC) hypoplasia and right orbital enophthalmos (Fig 2A, B). Ophthalmologic evaluation was significant for 2 mm right lateral canthal dystopia secondary to hypoplasia of the lateral orbital wall, 1 to 2 mm right medial canthal dystopia, and 1 mm globe ptosis. Visual acuity was 20/15 bilaterally. The remainder of the patient’s physical examination and medical history was noncontributory. CT imaging using a GE CT HiSpeed Advantage Scanner System Model B7998JP (General Electric Medical Systems, Milwaukee, wr) was used to produce 3-mm cuts at 0” gantry tilt, 120 kV, and 200 mAs. The two-dimensional axial CT images were then reformatted and reconstituted to l-mm cuts on a workstation using Advantage Windows 3D Analysis Package B7997WM1090AT (General Electric Medical Systems). The image data were converted using GEWORM software (Materialise NV, Belgium), and scatter in the scans was eliminated using MIMICS software (Materialise NV). Data for construction of the supports for the model during fabrication were generated using CSUP software (Materialise

NV). The support and model data were merged using MEISTRO (3D Systems, Valencia, CA) and sent to the X4-250 stereolithography apparatus (3D Systems). Total data formation and model fabrication time was 35 hours, The right ZMC hypoplasia was easily visualized on the 3D model (Fig 3). The cervical spine was removed from the model, and the posterior aspect was trimmed perpendicular to the sagittal plane at the mastoid processes. Bilateral reference measurements were then made to anatomic points of projection using a digital surveyor (Great Lakes Orthodontics, Tonawanda, NY). This allowed spatial comparison of the supraorbital rims and ZMCs (Fig 4). A 14mm anterior-posterior discrepancy was noted between the left and right ZMCs. Model surgery was performed by separating the ZMC with cuts through the arch, supraorbital rim, lateral orbital wall, infraorbital rim, and lateral maxillary wall. The segment could be advanced 8 mm in the area of the zygomaticomaxillary buttress while still maintaining bony contact (Fig 1). Further augmentation of the anterior ZMC and infraorbital rim was planned using acrylic templates simulating shapes of onlay bone grafts to be placed at the time of surgery (Fig 5). After induction of general anesthesia, the patient was prepared and draped for a combined intraoral and extraoral surgical procedure. Exposure of the cranium was accomplished through a coronal flap. A full-thickness cranial bone harvest measuring 5 cm in width and 12 cm in length was obtained from the right parietal region and sectioned into two equal pieces. Half of the full-thickness harvest was then transferred to another sterile field, where preparation of the proposed onlay bone grafts was completed by a second team member using the prefabricated acrylic templates from the stereolithography model as guides (Fig 6). The stereolithography model was not used in the sterile field but can be sterilized if needed. The remaining half of the cranial bone was split through the diploe and used to reconstruct the calvarial defect. The outer table of the anterior graft was maintained in the original position, and the inner table was used to form a new outer table for the posterior portion of the cranial harvest site. Both were fixed with titanium bone plates and 2-mm screws. Further exposure of the defect, including the zygomatic arch, lateral orbital rim, and infraorbital rim, was then accomplished. Intraoral exposure of the lateral nasal rim, lateral nasal bone, and malar process was achieved through a circumvestibular incision extending from the maxillary right third molar to the left lateral incisor. An osteotomy from the superior aspect of the lateral orbital rim through the lateral orbital wall and infraorbital rim was made with a reciprocating saw, while protecting the globe. Osteotomies and separation of the zygomatic arch and zygomaticomaxillary buttress were completed at this time. The malar process was mobilized, advanced 8 mm, and secured with titanium plates adapted to the zygomaticomaxillary buttress and lateral orbital rim. An additional titanium plate was adapted to the zygomatic arch and fixed with 1.5-mm diameter screws. Cranial bone grafts were fitted to bony defects in the zygomatic arch and lateral orbital rim steps and secured with 2-mm screws. The malar onlay bone grafts were found to fit as planned on the presurgical model, requiring only minimal adjustment, and were fixed with 2.0~mm screws (Fig 7). The enophthalmos and globe position were ad-

CORRECTION

FIGURE

2. Frontal

dressed by adapting a 1.5-mm-thick floor, which was also secured with The intraoral sites were irrigated placed, the coronal flap was closed

and

basal

views

of the patient.

bone graft to the orbital a 2.0~mm screw. and closed. A drain was in a layered fashion and

A, 6, Preoperative;

OF CONGENITAL

MALAR HYPOPLASIA

C, D, postoperative

pressure dressings were applied. Postoperative recovery was uneventful except for a subpericranial seroma that required several needle aspirations. The postoperative results at 6 weeks are seen in Figure 2C and D.

JAMES ET AL

FIGURE 3.

Basal

view

of acrylic

skull

before

surgical

simulation.

FIGURE

5. St model

with acrylic

templates

Discussion The advent of stereolithography dates back to the early 1980s when three researchers, A. Hebert, H. Kodama, and C. Hull, independently worked on the concept of rapid prototyping of 3D objects by successively building them in layers using light-cured liquid resin and laser light. Both Hebert and Kodoma had dif6culty maintaining ongoing support from their organizations, and they each stopped their work before proceeding to a product. Hull5 completed a

FIGURE 4.

St model

on surveyor

during

surgical

simulation.

system that was able to automatically fabricate prototype parts in detail and coined the term “stereolithography” for this process. The first commercial machine (SLA-1) was introduced at the Autofact Show in Detroit, Michigan, in November 1987. The %A-250 was introduced in 1988, and the SLA-500, a faster and larger system, in 1989. Currently, there are more than 800 machines operational worldwide, with the number growing daily.’ The total cost is approximately

FIGURE

6. Carved

calvarial

grails

and

acrylic

templates

516

CORRECTION

OF CONGENITAL

MALAR HYPOPLASIA

authors have evaluated the milling technique and found it to be satisfactory for presurgical planning in craniofacial procedures.’ Other studies have observed dimensional error of skulls fabricated with stereolithography to be most pronounced in overestimation of the width of the skull, with an overall dimensional error less than 0.2%.8,9

FIGURE fixed.

7.

Intraoral

view

of surgical

site with

calvarial

grafts

rigidly

$200,000 to $250,000 for an SLA-250 system and $500,000 to $550,000 for the SLA-500, depending on options ordered. Medical use of SL previously has been by manufacturers of orthopedic replacement joints. These are manufactured in standard or custom dimensions, using SL for rapid prototypes. Craniofacial applications of SL include preoperative fabrication of acrylic templates for bone graft shaping and pre-adaptation of surgical plates to the desired bony movements as simulated on the SL model. In our case, trial of the proposed surgical technique on the model assisted with transfer of direct measurements of bony movements from it to the patient and allowed template fabrication of onlay bone grafts. The accuracy of stereolithography has been compared to that of conventional milling by Klein et a1.6 CT images of six patients were formatted and used for manufacture of models created from polyurethane foam on a conventional milling system. One of these imageswas also formatted for SL construction on the SLA-250 stereolithography device. The polyurethane models were observed to be brittle and soft. Hollow and internal structures of the skull were not able to be produced, and the models were not sterilizable. The milling apparatus was also unable to negotiate undercuts, resulting in collisions between the milling tool and the model and causing destruction of both. The stereolithography reproduction did provide internal anatomy and was transparent and sterilizable. Other

The current cost of fabrication of an SL complete skull ranges from $800 to $3,500, depending on which rapid prototyping and manufacturing service bureau is contacted.lO With the rapid expansion in the numbers of SLAsavailable, increasing medical applications, and resultant competition among service bureaus, this price is expected to decrease.8 The expense is offset when considering the time spent in the operating room preparing material without the use of templates and the repeated contouring and placement of the material into areas of difficult access. The preoperative adaptation of thick reconstruction bars to the SL model may also contribute to reduction of operating time and expense. In our experience, the stereolithography model provided for a more thorough preoperative diagnosis and allowed rehearsal of the surgical procedure. Template fabrication for contouring of onlay grafts saved an estimated 2 to 3 hours of operating time, which is substantial when considering the average cost for an operating room constitutes approximately 34% of an entire inpatient hospital expense. l l Ideally, CT scans should be completed in increments of 1 to 1.5 mm in the area of study for the most accurate reproduction of stereolithography models.12 The level of patient radiation exposure with 1.5~mm cuts has been addressedby Yau et aL8The number of CT slicesversus the lens dose was calculated to be 6.5 to 19.8 mGy for 25 slices and 6.9 to 21.1 mGy for 50 sliceswhen the orbits are included in the scans.These figures are much lower than the 2-Gy single-exposure dose required for progressive cataract formation.” More medical applications of the SL process will be used as the accuracy, speed, and availability of such fabrication increases. Use of SL in maxillofacial surgery procedures improves patient education and presurgical treatment planning, reduces operating room time, and decreaseshospital costs. SL alsomay be used in cases of trauma if the definitive treatment is delayed. Disadvantages of SL include minimal application in trauma cases requiring immediate treatment because the length of time required for fabrication of the SL model, and the slightly increased radiation exposure of the patient if smaller CT cuts are used for increased accuracy of the SL model.

517

MEHRA ET AL

References 1. Jacobs PF: Rapid Prototyping and Manufacturing: Fundamentals of Stereolithography (ed 1). New York, NY, Society of Manufacturing Engineers, 1992 2. Jacobs PF: Stereolithography and other RP&M Technologies from Rapid Prototyping to Rapid Tooling. New York, NY, Society of Manufacturing Engineers in cooperation with the Rapid Prototyping Association of SME, ASME Press, 1996 3. Arvier JF, Barker TM, Yau YY, et al: Maxillofacial biomodeling. Br J Oral Maxillofac Surg 32:402, 1994 4. Stoker NG, Mankovich NJ, Valentino D: Stereolithographic models for surgical planning. J Oral Maxillofac Surg 50:466, 1992 5. Hull C: Apparatus for Production of Three Dimensional Objects by Stereolithography, U.S. Patent 4,575,330, March 11, 1986 6. Klein HM, Schneider W, Alzen G, et al: Pediatric craniofacial J Oral Maxillofoc 56517-521,

*Resident,

Department School

tAssistant

Professor

Medicine,

#Professor

Center,

and Director

Department University

Boston,

Boston,

Surgery,

of Resident

Surgery,

Boston

Department School

Training, University

DepartSchool

of

of Oral and Maxillofacial

of Dental

of Pathology,

Medicine,

Boston

Boston,

University

MA.

Medical

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Surgery,

10.

11.

12. 13.

Mehra, BDS, DMD, * David A. Cottrell, DMD, f E Booth, DMD,,f and Salim Jamil, MD, PbD.f

Metastatic tumors of the oral and facial region are uncommon, with the majority metastasizing to the mandible.l-3 The most common tumors that metastasize to the jaws are breast, lung, thyroid, and prostate. Metastases to the orofacial soft tissue structures are even rarer. In an extensive review of the literature from 1945 to 1970, Hatzoitis et all found only 48 reported casesof tumor metastasisto oral soft tissues, with the gingiva and tongue being the most common sites. The following case report describes the metastasis of carcinoma of the prostate to the soft tissue structures in the facial region without evidence of any bony

Dental

9.

Presentation of Metastatic Prostate Cancer

Pushkar Donald

ment

8.

Surg 1998

An Unusual

University

7.

surgery: Comparison of milling and stereolithography for 3D model manufacturing. Pediatr Radio1 22:458, 1992 Lambrecht JT, Brix F: Individual skull model fabrication for craniofacial surgery. Cleft Palate J 27:382, 1990 Yau YY, Arvier JF, Barker TM: Technical note: Maxlllofacial biomodeling-Preliminary result. Br J Radio1 68519, 1995 Mankovich NJ, Cheeseman AM, Stoker NG: Three dimensional anatomy with stereolithography models. J Digit Imaging 3:200, 1990 Personal communication with 10 SL service bureaus located in the United States (Names and addresses available on request) Macario A, Vitez TS, Dunn B, et al: Where are the costs in perioperative care? Analysis of hospital costs and charges for inpatient surgical care. Anesthesiology 83:1138, 1995 Scan Protocol: Cyberform International, Inc, 407 International Parkway, Suite 403, Richardson, TX 75081 Hall EJ: Radiobiology for the Radiologist (ed 4). Philadelphia, PA, Lippmcott, 1994, p 383

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St,

involvement. In our review of the existing literature, we encountered only two case reports of prostate cancer metastases to orofacial soft tissues Cbuccal mucosa, parotid, and skin of neck). This case appears to be the first report of prostate cancer metastasisto the muscles of mastication and also the first report of prostate cancer metastasis to orofacial soft tissue structures without evidence of concomitant bony involvement in the maxillofacial region.

Report

of Case

A 79-year-old white man was referred to the Boston University Oral and Maxillofacial Surgery Department with a chief complaint of left-sided facial swelling involving the mandibular angle and numbness of the left lower lip. His history was significant for hypertension, type 1 diabetes mellitus, mild anemia, and stage Da prostate cancer. His prostate cancer had been treated 1 year previously with partial prostate resection (TURP), bilateral orchiectomy, and radiation. Two weeks before presentation, the patient had undergone extraction of several left posterior mandibular teeth in the affected area because of suspected dental infection. The swelling in the left posterior mandible had continued to increase despite this treatment, and paresthesiahad been present for approximately 3 weeks. Physical examination showed a 3 X d-cm, firm, indurated soft tissue mass in the left genial region that seemed fixed to the underlying tissue (Fig 1). Mild trismus and paresthesia of the left lower lip were present,without evidenceof lymphadenopathy or odynodysphagia. A panoramic radiograph was normal. The abdomen was mildly distended and non-