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J Oral Maxillofac Surg69:285-294, 2011

Application of Virtual Surgical Planningfor Total Joint Reconstruction With a

Stock Alloplast SystemRavi Chandran, DMD, PhD,* Gary D. Keeler, DDS,†

Andrew M. Christensen, BS,‡ Katherine A. Weimer, MS,§ and

Ron Caloss, DDS, MD�

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urgical management of temporomandibular joint (TMJ)nkylosis can be challenging because of altered anatomynd proximity to key structures including the middleranial fossa, middle ear, and branches of the externalarotid artery. Navigation-guided resection has beensed to improve the margin of safety.1,2 Computer-as-isted design/computer-assisted manufacturing technol-gy has been developed for the surgical simulation andlanning of complex craniofacial procedures.3-7 How-ver, we are not aware of its use in managing moreomplex TMJ reconstruction. This modality offers theotential to improve safety and outcomes.We describe the use of computer-assisted virtualodel surgery to manage a patient with TMJ bony an-

ylosis. Interactive virtual surgical planning softwareSurgiCase CMF; Materialise NV, Leuven, Belgium) wassed to manipulate a 3-dimensional (3D) computed to-ographic (CT) based patient model to preplan the

esection, design cutting guides, and choose the appro-riate stock prosthesis size (for the Biomet Microfix-tion TMJ system; Biomet Microfixation, Jacksonville,L). Additive manufacturing technology (ie, rapid proto-yping) was used to fabricate stereolithographic modelsnd cutting guides to transfer the virtual plan to theperating room. The goal was to improve surgeon con-dence, patient safety, and the final fit of the stockrosthesis.

echnique

A 57-year-old African American woman was re-erred to the Department of Oral-Maxillofacial Surgery

*Resident, Department of Oral-Maxillofacial Surgery, University

f Mississippi Medical Center, Jackson, MS.

†Assistant Professor, Department of Oral-Maxillofacial Surgery,

niversity of Mississippi Medical Center, Jackson, MS.

‡President, Medical Modeling Inc, Golden, CO.

§Manager, Virtual Surgical Planning, Medical Modeling Inc,

olden, CO.

�Associate Professor and Program Director, Department of Oral-

axillofacial Surgery, University of Mississippi Medical Center,

ackson, MS.

285

nd Pathology at the University of Mississippi Medicalenter at Jackson for management of left TMJ bonynkylosis. On physical examination she was noted toave no mandibular range of motion. She had a debil-

tated dentition with no posterior occlusion beyondhe first premolars. A Panorex and a CT scan con-rmed the diagnosis of complete left TMJ bony anky-

osis with loss of normal condyle and fossa anatomy,ncreasing the concern for middle cranial fossa expo-ure during the resection. The right TMJ was normalFig 1).

The plan was to perform a single-stage resectionnd reconstruction of the left TMJ with a Biomettock total joint prosthesis. Medical Modeling IncGolden, CO) agreed to provide its computer-assistedesign/computer-assisted manufacturing technologynd engineering expertise to perform the surgeryirtually on a 3D CT-based model of the patient andhen to use additive manufacturing to fabricate surgi-al guides that would allow transfer of the plan to theperating room setting. The goals were to improveurgeon confidence and patient safety and to improvehe final fit of the noncustom fossa and condylarrostheses.The patient’s CT data in DICOM (Digital Imaging

nd Communications in Medicine) format was trans-erred to Medical Modeling by its secure file-transferrotocol site. Communication between the surgeonR.C.) and biomedical engineers for the virtual surgi-al planning was performed by a Web-based confer-nce.

Address correspondence and reprint requests to Dr Caloss: De-

artment of Oral and Maxillofacial Surgery, University of Mississippi

edical Center, 2500 N State St, Jackson, MS; e-mail: rcaloss@

mc.edu

2011 American Association of Oral and Maxillofacial Surgeons

278-2391/11/6901-0042$36.00/0

oi:10.1016/j.joms.2010.03.010

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286 TMJ RESECTION AND PROSTHETIC RECONSTRUCTION

Bony segmentation and rendering of the 3D max-llofacial skeleton was carried out using SurgiCaseMF software. This software facilitates anatomicisualization and virtual simulation of osteotomies,ony movements, and resections on a 3D bony levelnd visualization of the 2-dimensional reformattedT images.The surgeon indicated on the 3D model where he

esired osteotomy placement for the condyle/ra-us resection. The model was manipulated to as-

ess the location of the osteotomies relative to theiddle cranial fossa and mandibular foramen

Fig 2). The virtual resection was then performed.easurements were made to assure that an ade-uate thickness of bone remained below the middleranial fossa. The medial-lateral width of the supe-ior osteotomy was also measured so the surgeonould avoid overinstrumentation on the medial

IGURE 1. A, B, Coronal and sagittal computed tomographiccans showing complete left temporomandibular joint bony anky-osis and loss of normal condyle and fossa anatomy.

handran et al. TMJ Resection and Prosthetic Reconstruction.Oral Maxillofac Surg 2011.

ide of the joint (Fig 3). l

Digital files of the Biomet TMJ fossa and condylarrostheses were imported into the SurgiCase CMFoftware. The size of each prosthesis was visualizeddjacent to the residual fossa and ramus. The best-fitomponents were selected (Fig 4). The condylar pros-hesis had a premature contact on the lateral ramus athe angle region. It was anticipated that this areaould have to be reduced intraoperatively. Render-

ngs of this were provided and used intraoperativelys a guide for reduction of the lateral ramus to im-rove the adaptation of the condylar prosthesisFig 5). The bone thickness at each screw hole waseasured and the recommended screw length wasapped out for the surgeon to refer to intraopera-

ively (Fig 6).Superior (condyle) and inferior (ramus) cutting

uides were designed to adapt to adjacent bone.hey served to direct the osteotomies and transfer

he virtual plan to the operating room. FreeFormoftware (SensAble Technologies, Woburn, MA)as used for the design of the guides. Care was

aken to design the guides so they would be smallnough to introduce through the planned preauric-lar and submandibular dissections for access. Theondyle cutting guide had sufficient depth to en-ure proper medial-lateral angulation of the oscillat-ng saw blade. The screw holes in the cuttinguides coincided with the planned screw holes forhe fossa and condylar prostheses. This allowed theutting guide screw holes to serve as a guide forositioning of the prosthesis components as virtu-lly planned (Fig 7).

Stereolithographic files for the preresected anat-my model, postresected anatomy model, selectedossa and condylar prostheses, and cutting guidesere prepared for rapid prototype fabrication ofhysical models. They were subsequently sent to theurgeon so that he could confirm adequate osteotomyesign, adaptation of the cutting guides, and theroper prosthesis size and position (Fig 8). The mod-ls and guides were subsequently sterilized accordingo the manufacturer’s recommendations for use intra-peratively.The patient was taken to the operating room and

tandard preauricular and modified submandibularissections were carried out to gain access. The pa-ient was noted to have a complete bony ankylosisith no discernable joint space. The cutting guidesere adapted to the bone and secured in place withone screws. Fit of the guides to the bone was con-idered excellent by the surgeon at the time of fixa-ion (Fig 9). The superior and inferior osteotomiesere carried out and the condyle/ramus was resectedithout complication (Fig 10).The patient was then placed into maxillomandibu-

ar fixation. The stereolithographic models of the

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CHANDRAN ET AL 287

ossa and condylar prostheses were used as sizers toonfirm proper fit of the planned stock prosthesis.he fossa prosthesis was then placed against the re-idual bone. Minimal recontouring of the lateral as-ect of the zygomatic arch was necessary to improvet. The bone on the lateral aspect of the mandibularngle was reduced as planned to improve the fit of theondylar prosthesis. The previously drilled cuttinguide screw holes served to confirm proper position-ng of the prosthesis as virtually planned (Fig 11). Theatient was released from maxillomandibular fixation,nd adequate joint function and occlusion were con-rmed. The intraoperative maximum interincisal open-

ng was 41 mm, and at 3 months postoperatively it wasaintained at 30 mm.A deviation study was performed to assess the

ctual position of the fossa and condylar prosthesesn relation to the virtual plan. An intraoperative CTcan was obtained with an xCAT ENT (Xoran Tech-ologies, Ann Arbor, MI) after placement of theotal joint prosthesis. Segmentation was performednd renderings of the 3D maxillofacial skeleton androsthesis were created from this DICOM dataset.hese renderings were superimposed on the pre-

IGURE 2. A-C, Virtual plan foruperior and inferior osteotomiesor the condyle/ramus resection.

handran et al. TMJ Resectionnd Prosthetic Reconstruction.Oral Maxillofac Surg 2011.

perative model with the virtually planned place- n

ent of the total joint components. The preopera-ive and postoperative scans were not performedith the patient in centric occlusion or maxillo-andibular fixation. Thus, the mandible was in a

lightly different position during each scan. Also,he 2 scans were performed on different machines.herefore, manual alignment adjustments were per-

ormed to achieve the best possible bony superim-osition, and a true quantitative measurement isot feasible. Because the fossa prosthesis is made ofltra high-molecular-weight polyethylene, it is radi-lucent and was not visible on the intraoperativecan. To replicate the fossa position, a digital com-uter-assisted design file of the fossa was importednd aligned based on the position of the screwssed to secure the fossa implant. Figure 12 showslose alignment of the actual prosthesis to the vir-ually planned one.

iscussion

Computer-assisted planning and intraoperativeavigation have led to improved preoperative plan-
ing and precision surgery for complex craniomax-

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llofacial surgery.1-7 Xia et al validated the use of aomputer-aided surgical simulation system to per-orm osteotomies for correction of complex dento-acial deformities. Rapid prototyping is used to fab-icate occlusal splints and transfer the virtual

IGURE 3. A, B, Various measurements on the virtual model wereuperior osteotomy was measured so the surgeon would avoid ovuperior osteotomy to the middle cranial fossa was also measured

handran et al. TMJ Resection and Prosthetic Reconstruction. J O

lanning to the operating room.3-5 They also usedomputer planning and intraoperative navigationor secondary reconstruction of post-traumatic skel-tal deformities.6 Hirsch et al7 described the use ofsimilar technology to virtually plan mandibular

to assist in planning the resection. The medial-lateral width of thementation on the medial side of the joint. The distance from the

axillofac Surg 2011.

FIGURE 4. A-C, Digital files ofthe Biomet temporomandibularjoint fossa and condylar prosthe-ses were imported using Surgi-Case CMF software. The best-fitting sizes were selected.

Chandran et al. TMJ Resectionand Prosthetic Reconstruction.J Oral Maxillofac Surg 2011.

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CHANDRAN ET AL 289

umor resection and reconstruction with a free fib-la bone graft.Intraoperative navigation has been used to guide

MJ ankylosis resection.1,2 However, we are notware of any previous reports of computer-aided sur-

IGURE 5. A-C, Renderings were provided to identify the locationoted.


IGURE 6. A, B, The bone thickness (gray numbers) at each screwas recorded for the surgeon to refer to intraoperatively.

handran et al. TMJ Resection and Prosthetic Reconstruction. J Oral M

ical planning for the management of an ankylosisase as we have described.Custom or stock alloplast prosthesis can be used to

econstruct the TMJ after ankylosis resection is per-ormed. A major advantage of a stock prosthesis is

a premature contact between the prosthesis and gonial angle was


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ower cost compared with a custom-designed one.he resection and reconstruction can be performed

n a single-stage surgery. A disadvantage of a stockrosthesis is the potential increase in time required

ntraoperatively to choose the best-fitting prosthesisnd in recontouring bone to improve the fit. The finaldaptation to the underlying bone may not be asrecise as a custom-fabricated one. A poorer-fitting

IGURE 7. A-E, Superior (condyle) and inferior (ramus) cutting gun the cutting guides coincided with the planned screw holes for theo serve as a guide for positioning of the prosthesis components a


rosthesis that does not integrate with the underlying c

one may be more prone to developing a surroundingbrous capsule. This could allow micromovement,ontributing to screw loosening and possible implantailure.8

We are not aware of a study comparing the clinicalesults of a similarly designed custom and stock TMJotal joint prosthesis. Thus, it is not known if a simi-arly designed stock prosthesis performs as well as a

re designed to adapt to adjacent bone. Note that the screw holesnd condylar prostheses. This allowed the cutting guide screw holeslly planned.


ides wefossa as virtua

ustom-fit one. The orthopedic literature does not

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CHANDRAN ET AL 291

enerally show improved clinical outcomes whenomparing custom-fit with off-the-shelf prostheses forotal hip arthroplasty.9,10

The application of virtual surgical planning andemplate-based clinical transfer in this case allowed uso achieve the desired goals of improving surgeononfidence and patient safety. It is likely that it alsomproved the final fit and positioning of the pros-hesis.

Virtual surgery provides a “dress rehearsal” for thectual surgery. The 3D computer modeling allows theurgeon to better conceptualize the anatomic partsnd recognize potential problems. The surgeon doesot have to rely as much on imagination or experi-nce to envision how the surgery will unfold and

IGURE 8. A, B, Preresected and postresected maxillofacial mod-ls, cutting guides, and prostheses were fabricated using additiveanufacturing technology for verification of the virtual plan.


void complications. The surgical plan can easily beCJ

ltered on the computer to choose the most appro-riate plan. It is an invaluable training tool, particu-

arly for less experienced resident surgeons.Measurements can be made and taken to the oper-

ting room to improve confidence. For instance,nowing the depth of the superior condylar osteot-my is important to avoid carrying instrumentationoo far medially where blood vessels lie. Knowing theosition of the superior osteotomy relative to theiddle cranial fossa is also important.The condylar cutting guide was designed with a

rajectory that was perpendicular to the lateral sur-ace of the zygomatic arch. This allowed for an im-roved fit of the fossa prosthesis because the portionhat rests against the residual glenoid fossa is oriented

IGURE 9. A, B, Fossa and ramus cutting guides were adaptednd secured in place. Care was taken to design the guides to bemall enough to introduce through the planned preauricular andubmandibular dissections used for access.


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t 90 degrees to the part that overlies and is screw-etained to the zygomatic arch.

We placed different-sized digital prosthesis compo-ents against the resected mandible and skull base toetermine which size was the best fit before surgery.he virtual surgical planning on the computer alsollowed us to see the premature contact of the con-ylar prosthesis at the mandibular angle. We knewhis area of bone had to be reduced at the time ofurgery to improve the adaptation of the prosthesis tohe lateral ramus and avoid torquing the condylaread in the fossa.Although interactive “3D” computer software cre-

tes a model that allows one to better sense the 3Delationships of objects, it is important to realize ones still viewing a 2-dimensional object on a flat screen.n addition, without haptic technology, one does notave the sense of feel, which the surgeon commonlyelies on. For these reasons, stereolithographic mod-ls that can be physically held and manipulated stillave usefulness. In the present case, models were

IGURE 10. A, B, The superior and inferior osteotomies werearried out as virtually planned and the condyle/ramus unit wasesected.


sed to confirm and better appreciate what was per-CJ

ormed virtually on the computer. The fit of the cut-ing guides and prosthesis was confirmed on the phys-cal skull models. This was important becauseccurately designed and fitting cutting guides are es-ential for the clinical transfer of the virtual surgicallan to the operating room. As one develops familiar-

ty with interactive software and virtual planning on aomputer, physical modeling may be less relevant.Although this technology may allow one to achievebetter result, is the cost reasonable? To be cost-

ffective, this technology must save the surgeon timend not be cost prohibitive. We did not specificallyook at this. However, we can make some generalomments. We believe the preoperative planning

IGURE 11. A, B, The fossa and condylar prostheses were se-ured in place. Minimal recontouring of the mandibular angle wasecessary to improve fit as predicted initially (Fig 5). The previouslyrilled cutting guide screw holes served as a guide for positioningf the prostheses as virtually planned.


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CHANDRAN ET AL 293

IGURE 12. A-D, The preoperative virtual plan and postoperative models were superimposed. Manual adjustments to align the bonynatomy were done to allow for the most accurate view of the prostheses and comparison of predicted with actual placement position. Colorapping shows close alignment of the actual prosthesis to the virtually planned one.

handran et al. TMJ Resection and Prosthetic Reconstruction. J Oral Maxillofac Surg 2011.

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ranslated into a more streamlined surgery that tookess time to perform. This ultimately can translate intoavings for the surgeon and patient or third-partyayer. Overall, we believed that the added expense ofhis technology was offset by cost savings in using aingle-stage stock prosthesis (compared with a 2-stageustom prosthesis) and in a decrease in operatingime.

A remote service provider with the necessary infra-tructure to carry out the described technique is es-ential. The surgeon does not need to be a softwarexpert or invest in the technology. The surgeon has toommit time to downloading the CT DICOM data andit in on a Web conference with the engineers toerform the virtual surgery. There is a learning curve

or everyone involved that takes time and effort. Withxperience, efficiency should increase and the timeequired should decrease.

We have described the first-time application of vir-ual surgical planning and template-based clinicalransfer to carry out TMJ resection and total jointrosthetic reconstruction in a patient with a bonynkylosis using a Biomet stock TMJ prosthesis. Thisechnology improved surgeon confidence and patientafety. The virtual planning allowed a “customized” fitf a noncustom prosthesis. Improved fit of the stockrostheses likely will provide a greater chance for

ong-term implant success.

eferences1. Schmelzeisen R, Gellrich NC, Schramm A, et al: Navigation-

guided resection of temporomandibular joint ankylosis pro-motes safety in skull base surgery. J Oral Maxillofac Surg 60:1275, 2002

2. Yu HB, Shen GF, Zhang SL, et al: Navigation-guided gap arthro-plasty in the treatment of temporomandibular joint ankylosis.Int J Oral Maxillofac Surg 38:1030, 2009

3. Xia JJ, Gateno J, Teichgraeber JF, et al: Accuracy of the com-puter-aided surgical simulation (CASS) system in the treatmentof patients with complex craniomaxillofacial deformity: A pilotstudy. J Oral Maxillofac Surg 65:248, 2007

4. Xia JJ, Gateno J, Teichgraeber JF: Three-dimensional computer-aided surgical simulation for maxillofacial surgery. Atlas OralMaxillofac Surg Clin North Am 13:25, 2005

5. Gateno J, Xia JJ, Teichgraeber JF, et al: Clinical feasibility ofcomputer-aided surgical simulation (CASS) in the treatment ofcomplex craniomaxillofacial deformities. J Oral Maxillofac Surg65:728, 2007

6. Xia JJ, Gateno J, Teichgraeber JF: A new paradigm for complexmidface reconstruction: A reversed approach. J Oral MaxillofacSurg 67:693, 2009

7. Hirsch DL, Garfein ES, Christensen AM, et al: Use of computer-aided design and computer-aided manufacturing to produceorthognathically ideal surgical outcomes: A paradigm shift inhead and neck reconstruction. J Oral Maxillofac Surg 67:2115,2009

8. Wolford LM: Factors to consider in joint prosthesis systems.Proc (Bayl Univ Med Cent) 19:232, 2006

9. Bert JM: Custom total hip arthroplasty. J Arthroplasty 11:905,1996

0. Gotze C, Rosenbaum D, Hoedemaker J, et al: Is there a need ofcustom-made prostheses for total hip arthroplasty? Gait analy-sis, clinical and radiographic analysis of customized femoral
components. Arch Orthop Trauma Surg 129:267, 2009

virtual scanning total joint

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