O r t h o g n a t h i c S u r g e r y an d the Temporomandibular Joint Patient John C. Nale, DMD, MDa,b,* KEYWORDS Orthognathic surgery TMJ Treatment Resorption Reconstruction Virtual surgical plan
KEY POINTS
The role of orthognathic surgery for the correction of dentofacial deformities is widely accepted. However, its role in the treatment of temporomandibular joint disorders (TMD) is quite controversial. There are numerous studies that show improvement of temporomandibular joint (TMJ) dysfunction1–3 following orthognathic surgery, whereas there are just as many that show no significant improvement or even worsening of symptoms following surgery.4,5 Interestingly, data also suggest that TMD patients will show some improvement in symptoms with simply the passage of time; this poses the question as to whether or not improvement of symptoms occurs as a result of surgery or due to the cyclic nature of TMD. It should also be noted that a small percentage of asymptomatic patients who undergo orthognathic surgery actually develop TMD symptoms. With these facts under consideration, one can infer
that orthognathic surgery cannot predictably treat TMD. Instead, surgeons should simply recognize that TMD coexists in a subset of patients requiring orthognathic surgery for the correction of a skeletal malocclusion. Therefore, TMD and skeletal malocclusions should be treated as separate entities. Given the potential for TMD symptoms to worsen following orthognathic surgery, it is important to recognize those patients with TMD and manage them independently of the dentofacial deformity. Most advocate that this should be done before planned orthognathic surgery. Once symptoms have significantly improved or resolved, focus may then shift to the orthognathic phase of treatment. The astute surgeon must then recognize those patients with a high risk of surgical relapse related to postoperative condylar remodeling and modify their treatment plans and surgical
Disclosures: None. a Department of Oral and Maxillofacial Surgery, Louisiana State University Health Science Center, New Orleans, LA, USA; b Private Practice, Carolina’s Center for Oral and Facial Surgery, 8840 Blakeney Professional Drive, Suite 300, Charlotte, NC 28277, USA * Private Practice, Carolina’s Center for Oral and Facial Surgery, 8840 Blakeney Professional Drive, Suite 300, Charlotte, NC 28277. E-mail address: [email protected] Oral Maxillofacial Surg Clin N Am - (2014) -–http://dx.doi.org/10.1016/j.coms.2014.08.012 1042-3699/14/$ – see front matter Ó 2014 Elsevier Inc. All rights reserved.
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Orthognathic surgery cannot be used as a predictable treatment of temporomandibular joint disorders (TMD). TMD symptoms should be treated independent of dentofacial deformities. Orthognathic surgery treatment plans should be modified in TMD patients to minimize exacerbation of symptoms. Patients with a class II malocclusion secondary to condylar resorption should be managed carefully due to their high risk of surgical relapse. Virtual surgical planning has improved the accuracy of combined orthognathic surgery and alloplastic temporomandibular joint reconstruction.
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Nale technique to minimize the potential for early and late postoperative malocclusion (Box 1). TMD can be defined as a collection of signs and symptoms related to the masticatory system. Those signs and symptoms include TMJ pain, pain associated with the muscles of mastication, headache, limited mouth opening, and joint noise. It has been reported that at least one of these symptoms occurs in approximately 50% of all patients seeking treatment of skeletal malocclusion.1,6 These patients require a thorough workup to establish the primary cause of their TMD symptoms. The work-up for TMD should include a history, physical examination, radiologic examination, and laboratory evaluation if indicated.
HISTORY A detailed questionnaire given to the patient before the initial appointment is the typical avenue to assemble the collection of TMD symptoms. The surgeon’s interview with the patient should focus on the chief complaint and symptom descriptors such as location, onset of occurrence, condition or character, alleviating or aggravating factors, timing, and so on.
PHYSICAL EXAMINATION Evaluation of the patient’s mandibular range of motion should be detailed. Pain-free maximum incisor opening should be noted, followed by maximum opening with passive stretching. The onset and location of pain during opening should also be recorded because this may help in the establishment of the origin of pain. Next, the muscles of mastication should be evaluated. Each muscle group should be palpated individually and assessed for pain, spasms, or fasciculations. Next, the joints should be loaded by having the patient bite on a tongue blade. Contralateral pain may indicate an intracapsular origin of pain, where ipsilateral pain may suggest a muscular origin. Next, the lateral and posterior aspects of the condyles
Box 1 Primary goals of orthognathic surgery on the TMJ patient Identify cause of TMD symptoms Successfully treat TMD symptoms Correct the dentofacial deformity Minimize the risk of relapse Minimize the risk of postoperative TMD symptoms
should be palpated. Palpation is useful for detecting intracapsular pain and joint noise and for establishing the amount of translation of the condylar head during mouth opening. Lastly, an otoscopic examination should be performed to rule out any potential cause for pain located within the ear.
RADIOLOGIC EXAMINATION The panoramic radiograph is useful for the screening of the mandibular condyle and its relationship to the glenoid fossa. It also allows for visualization of the coronoid process of the mandible. Computed tomography (CT) and cone beam computed tomography (CBCT) allow for a more detailed and 3-dimensional view of TMJ. These modalities allow for the visualization of any asymmetries, cortical erosions, subchondral cysts, tumors, heterotopic bone, ankylosis, or any other bony abnormality. Newer software also allows serial images to be superimposed to evaluate for active growth or resorption (Fig. 1). However, a panoramic radiograph, CT, or CBCT cannot visualize the TMJ disc. Magnetic resonance imaging is considered the “gold standard” for the evaluation of the soft tissues of the joint. Its multiplanar images allow for direct visualization of disc position at rest and during mouth opening. On occasion, a technetium 99 bone scan may be indicated. This modality is sensitive in the detection of bone activity such as remodeling or resorption. Unfortunately, it cannot differentiate between the two.
LABORATORY EVALUATION Laboratory testing is generally reserved for those patients who are suspected to have a systemic disease process. An erythrocyte sedimentation rate and C-reactive protein may be ordered to check for these acute phase reactants. A positive test result indicates the presence of a systemic inflammatory process, but is not specific for the cause. More specific tests for various immune factors such as rheumatoid factor and antinuclear antibody may also be indicated. Once the appropriate data have been collected, an accurate diagnosis can be established and the patient treated appropriately. Reversible measures are indicated as the first line of treatment. Such reversible measures include patient education, medications, physical therapy, and occlusal splint therapy. Generally patients respond favorably to this form of treatment, but occasionally pain and TMJ dysfunction persist. In this subset of patients, irreversible treatments such as trigger point injections, botox
Orthognathic Surgery and the TMJ Patient
Fig. 1. Superimposition of cone-beam CT scans of the same patient taken 1 year apart.
injections, arthrocentesis, arthroscopy, or even open arthroplasty can improve symptoms refractory to conservative therapy (Box 2). If a patient fails to respond to these treatments, there is no reason to think that they will improve with orthognathic surgery. Fig. 2 suggests an algorithm for the treatment of TMD symptoms in patients with a dentofacial deformity. Although treatment of symptomatic disc derangements is typically performed before any planned orthognathic procedure, some argue that it is safe and predictable for both to be done simultaneously. Wolford7 suggests that the benefits of concomitant surgery include the following: 1. Requires one operation and general anesthetic 2. Balances occlusion, TMJs, jaws, and neuromuscular structures 3. Decreases overall treatment time 4. Eliminates unfavorable TMJ sequelae that can occur when performing orthognathic surgery only 5. Avoids iatrogenic malocclusion that can occur when performing open TMJ surgery only The case against concomitant surgery is that the condyle-fossa relationship becomes vulnerable to the experience of the surgeon.8 That is, there is potentially a higher chance of postoperative malocclusion related to a change in the condylefossa relationship following surgery.
Box 2 Treatment of TMD symptoms in patients with a dentofacial deformity Reversible Treatment of TMD Patient Education Medications Nonsteroidal antiinflammatory drugs (antiRA meds) Muscle relaxants Antidepressants Physical Therapy ROM exercises Passive stretching Spray and stretch Ultrasound Transcutaneous electrical nerve stimulation Occlusal Splint Therapy Irreversible Treatment of TMD Trigger Point Injections Botox Arthrocentesis Arthroscopy Open Arthroplasty
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Fig. 2. Flow diagram and treatment algorithm for patients with a dentofacial deformity and TMD symptoms. NSAID, nonsteroidal antiinflammatory drug.
Orthognathic Surgery and the TMJ Patient SURGICAL CONSIDERATIONS UNIQUE TO SPECIFIC SKELETAL MALOCCLUSIONS Once a patient has responded to the treatment of TMD symptoms, correction of the dentofacial deformity may be addressed. Surgical patients will likely present with a class II or class III skeletal malocclusion with or without asymmetry. Before any surgical treatment plan is formulated, the surgeon should be familiar with the jaw relationships that are more susceptible to the development of postoperative pain, TMJ dysfunction, and condylar resorption. Only with this knowledge can a treatment plan be tailored to minimize the patient’s risk.
Class III Malocclusion Patients having a class III skeletal malocclusion are the least likely of all jaw relationships to have preoperative TMD. However, the risk of developing postoperative TMD does exist. Therefore, they should be managed accordingly. Class III patients undergoing a bilateral sagittal split osteotomy (BSSO) do show some degree of postoperative posterior or lateral displacement of the condyle, but in large this does not cause a significant change in TMJ disc position nor result in significant postoperative pain.9–11 Therefore, a surgeon should have no reservations using this technique when performing mandibular setback surgery in patients with a history of TMD. An intraoral vertical ramus osteotomy (IVRO) has been advocated by some as the technique of choice in TMD patients with a class III skeletal malocclusion (Fig. 3). The rational is that an IVRO will result in an anterior and inferior displacement of the condyle. This displacement increases the joint space and promotes disc reduction in joints with disc displacement with reduction or recent progression to disc displacement without reduction.12 Hu and colleagues13 showed that 75% of patients undergoing an IVRO had an improvement or resolution of TMJ pain and no asymptomatic patients developed new pain, whereas only 40% of patients undergoing BSSO showed improvement in symptoms and 8% of asymptomatic patients developed new symptoms. The debate over which surgery to perform exists because patients undergoing IVRO must be placed in maxillomandibular fixation (MMF) for an extended period of time postoperatively; this may increase the risk of developing limited mouth opening. Also, because of the condylar sag that occurs as a result of an IVRO, the condyle may reseat in a more superior position, due to muscle pull, following the release of MMF. Consequently, this would lead to an open-bite deformity.
Fig. 3. Intraoral vertical ramus osteotomy. This surgical option may minimize postoperative TMD symptoms in patients requiring mandibular setback.
Class II Malocclusion—Progressive/Idiopathic Condylar Resorption It has been proposed that TMJ remodeling can be both functional and dysfunctional.14–18 Functional remodeling involves morphologic changes of the articular surfaces of the TMJ that does not cause any significant alterations of the joint or the occlusion. Conversely, remodeling of the TMJ is considered to be dysfunctional if the morphologic changes lead to a loss of condylar-ramus height, resulting in mandibular retrusion and a class II malocclusion. In some, it may also lead to an anterior open bite. Dysfunctional remodeling has historically been termed condylar resorption. Condylar resorption may occur as a result of several reasons. A few examples include systemic and local arthritidis and trauma. If no obvious cause is identified, it is termed idiopathic condylar resorption (ICR). Patients with a history of condylar resorption pose a difficult challenge to the treating orthodontist and orthognathic surgeon. The difficulty arises because any treatment that causes excessive mechanical loading may predispose the patient to further condylar resorption and the resulting class II open-bite deformity (Fig. 4). The surgical treatment of class II open-bite patients usually involves
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Fig. 4. Cephalometric radiographs depicting postoperative relapse following orthognathic surgery for correction of a class II skeletal malocclusion. (A) Pre-op. (B) Post-op day 1. (C) Completion of orthodontics at 3 months postop. (D) 3 years post-op.
a Le Fort I osteotomy in conjunction with a bilateral sagittal split of the mandible, with or without counterclockwise rotation of the maxillomandibular complex. This combination of procedures increases the mechanical load of the TMJ19 and may result in postsurgical relapse. The key to successful treatment is recognition of those patients who are at high risk for postsurgical condylar resorption and to modify treatment to minimize their risk. Predisposing factors for developing postsurgical relapse secondary to condylar resorption have been well documented. Patients with systemic diseases such as rheumatoid arthritis, scleroderma, systemic lupus erythematosus, and other vascular collagen diseases have been reported as high risk.20–23 Predisposing factors for ICR include TMJ dysfunction, being a young woman, having a high mandibular plane angle, and having a posteriorly inclined condylar neck.21,23–29
Preoperatively, patients with a systemic disease should be referred to a rheumatologist for evaluation and treatment. It has been suggested that all high-risk patients be placed on antiinflammatory medication, tumor necrosis factor a inhibitors, or matrix metalloproteinase inhibitors, because targeted pharmacotherapy might be able to prevent further condylar resorption.30 Occlusal splints are also recommended for those patients with TMJ pain and dysfunction. The splint serves 2 purposes. The first purpose is to limit joint loading; the second is to determine cessation of the resorptive process. Patients are fitted with a splint with registered contact of the mandibular teeth. If the lower incisors lose contact over time, this indicates active resorption.31 Serial radiologic imaging, orthopantogram and cephalometric radiographs, and CBCT can be used to evaluate change in condylar shape. A technetium 99 bone scan may also be useful in determining active resorption. Timing of surgery
Orthognathic Surgery and the TMJ Patient should also be strongly considered. ICR is most active in the teenage years and mid 20s; therefore, surgeons should consider waiting until after the age of 25 years to correct the dentofacial deformity. Intraoperatively, special considerations exist for patients who are at a high risk of developing postoperative condylar resorption. Joss and Vassalli32 reported long-term relapse (condylar resorption) for cases treated with bicortical screws (2%–50.3%), whereas miniplates had comparatively much less relapse (1.5%–8.9%). Arnett and Gunson26 relate this statistical difference to condylar torquing as a result of bicortical screws displacing the proximal segment during fixation of BSSOs. He, therefore, recommends the use of monocortical miniplates for fixation of BSSOs (Fig. 5). If possible, one might also consider limiting the surgical correction to just the maxilla. Hoppenreijs and colleagues27 reported that the incidence of condylar resorption after surgery performed only on the maxilla for correction of class II open bite was less than that after bimaxillary osteotomies (9% compared with 23%). Lastly, if bimaxillary surgery is required, one might consider minimizing mandibular advancement because larger advancements stretch the surrounding soft-tissue components and this tension can lead to greater compression and mechanical loading of the condyle, resulting in resorption.33–35 Postsurgical management should include medications as needed, class II elastics, and occlusal splint therapy after debanding. Patients should be observed on a regular basis because relapse
Fig. 5. Sagittal split osteotomy using miniplate fixation for mandibular advancement.
usually presents with an anterior open bite between 6 months and 3 years following surgery.19 It should also be noted that repeating an osteotomy on the condylar resorption patient whose first orthognathic surgery was unsuccessful has close to a 50% failure rate reported in the literature.19,25,36 To minimize failure rate, total joint replacement may be considered, especially in those patients with symptomatic or active resorption (Fig. 6).
COMBINED ORTHOGNATHIC SURGERY AND ALLOPLASTIC TEMPOROMANDIBULAR JOINT RECONSTRUCTION Occasionally, a patient may present with both a skeletal-facial deformity and an end-stage TMJ pathologic condition. In this scenario, orthognathic surgery combined with alloplastic TMJ reconstruction should be considered. Commonly, the dentofacial deformity occurs as a result of the TMJ disease due to resorption or decreased condylar growth. Often times these patients have had numerous failed treatment attempts or suffer from chronic joint pain or dysfunction. TMJ disorders commonly associated with skeletal-facial deformities include reactive arthritis, condylar hyper- or hypoplasia, ICR, congenital deformation, trauma, or other end-stage TMJ pathologic conditions. These common TMJ disorders often result in a loss of condylar-ramus height. Patients with advanced disorders will have a steep mandibular plane angle, loss of chin projection, and possibly an anterior open bite. Their chief complaints may include joint or facial pain, difficulty chewing, and esthetics. For patients diagnosed with end-stage TMJ pathologic condition, one might consider a combination of orthognathic surgery and alloplastic joint reconstruction (Fig. 7). For unilateral TMJ pathologic condition, one would consider a Le Fort I osteotomy combined with a mandibular unilateral sagittal split and total joint reconstruction on the contralateral side. For bilateral TMJ pathologic condition, one would consider a Le Fort I osteotomy combined with a bilateral total joint reconstruction. TMJ reconstruction and mandibular advancement with custom alloplastic total joint prostheses in conjunction with maxillary osteotomies, for counterclockwise rotation of the maxillomandibular complex, has been shown to be a stable procedure.37 However, the surgery requires meticulous planning to restore form and function to the patient. The difficulty of the surgery arises from the fact that the joint prosthesis must be manufactured to correspond with the planned new position of the maxilla and mandible. Any inaccuracy may
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Fig. 6. (A, B) Total joint reconstruction used to correct an open-bite malocclusion after surgical relapse following orthognathic surgery. This patient had developed chronic pain and limited mouth opening before joint replacement.
result in a persistent malocclusion and compromised facial esthetics. Traditionally, planning begins with cephalometric analysis to predict the final position of the maxillary incisors; this likely requires a counterclockwise rotation of the maxillomandibular complex. Jaw relation records are taken and transferred to stone models. Model surgery based off of the cephalometric analysis is then performed to produce an intermediate and final splint. Also, a 2-piece stereolithographic model of the patient’s skull is fabricated from a preoperative CT scan. Bilateral condylectomies or a condylectomy and sagittal split osteotomy are performed on the model (Fig. 8). Once completed, the intermediate splint is used to establish the new position of the mandible (Fig. 9). The stereolithographic model is then sent to TMJ Concepts (Ventura, CA, USA) for a wax-up and ultimately, final production of the patient-specific joint prosthesis. With this method, the joints are placed first during surgery and the final position of the maxilla is established off of the new position of the mandible. During the planning phase of treatment, there are many steps in which inaccuracies may occur. Errors with impressions, bite registration, and face-bow transfer would result in inaccurate mounted stone models. Of course this would then perpetuate into an intermediate splint that places the mandible into a position other than that which is planned. Another step that may introduce error during planning is when the intermediate occlusion is established on the stereolithographic model. It is very common for these models to have gross inaccuracies in tooth anatomy (Fig. 10). There are 2 reasons for this. The first is that patients typically have their images taken in the CT scanner with their mouths closed. Having their upper and lower teeth touch during
the imaging process ultimately distorts the image quality of the occlusal surfaces of the teeth. The other reason is that metallic restorations cause scattering of the image. This scattering is then transferred to the stereolithographic model. Regardless of the cause, the surgeon may find it difficult to seat the intermediate splint onto the model because of these inaccuracies. If the upper and lower teeth are not placed into the exact relationship relative to the stone model, the joints will be fabricated based off of an inaccurate mandibular position. This inaccuracy would then be transferred to the patient’s final occlusion.
VIRTUAL SURGICAL PLANNING Recently, there has been a paradigm shift in orthognathic surgery planning. To minimize the inaccuracies associated with traditional planning methods, it is becoming more common for surgeons to plan surgeries virtually using computeraided surgical simulation (CASS). Gelesko and colleagues38 described CASS as a method that generally consists of 4 phases: 1. Data acquisition phase: clinical examination with bite registrations and anthropometric measurements; radiographic examination/CT scan 2. Planning phase: importation of 3D CT data into proprietary planning software 3. Surgical phase: translation of the virtual surgical plan to patients using stereolithographic models, cutting guide stents, occlusal splints, or intraoperative navigation 4. Assessment phase: evaluation of the accuracy of virtual surgical plan transfer using intraoperative or postoperative CT imaging It has been demonstrated that the CASS protocol39 is not only feasible40,41 but also can
Orthognathic Surgery and the TMJ Patient
Fig. 7. (A–D) This patient developed facial asymmetry, chronic pain, and limited mouth opening following an undiagnosed condyle fracture as a child. A treatment plan consisting of a left total joint replacement in conjunction with orthognathic surgery was chosen due to the end-staged nature of the left joint.
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Fig. 8. A 2-piece stereolithographic model depicting a left-sided unilateral sagittal split performed in conjunction with a right-sided total joint replacement for the correction of a skeletal malocclusion.
Fig. 10. The occlusal surfaces of the teeth are grossly distorted on this stereolithographic model. The distortion may occur as a result of scatter from the CT scan or if the patient had their teeth occluded while taking the CT scan.
accurately and consistently be transferred to the patient’s maxilla and mandible at the time of surgery.42–45 Once the final position of the occlusion is established, an intermediate and final splint can be manufactured based on the virtual image. This technique may also be used to improve the accuracy of combined orthognathic and joint reconstruction surgery. Planning begins with the data acquisition phase of the CASS system. Natural head position is established with either fiducial markers placed onto the patient’s face along the true vertical and horizontal lines or with the use of a gyroscope. Next, another fiducial marker is placed into a bite jig and placed into the patient’s mouth, which captures an occlusal record. With the fiducial markers in place, a CT or CBCT scan is taken. Stone models of the patient’s occlusion are then obtained and placed into the previously
used bite jig. The stone models are then digitized with either a laser surface scanner or a CBCT scanner. Lastly, the final occlusion is established on the stone models and then scanned. The planning phase begins by uploading the Digital Imaging and Communications in Medicine data from CT scans or CBCT scans and digital models obtained from a laser scanner to a thirdparty service provider to facilitate software manipulation and splint fabrication (Medical Modeling Inc, Golden, CO, USA). The software engineers then integrate the different datasets to create an accurate digital image of the patient (Fig. 11). Next, a planning session involves establishing the final position of the maxilla based off of the desired incisor position relative to the upper lip. Next, the mandibular position is established using the predetermined final occlusion. Symmetry of
Fig. 9. The intermediate occlusion is established on the stereolithographic model using an acrylic splint fabricated from dental stone models following traditional model surgery.
Fig. 11. Datasets from a CT or CBCT and dental stone models are integrated to create an accurate digital image of the patient’s bony skeleton and teeth.
Orthognathic Surgery and the TMJ Patient
Fig. 12. (A) Virtual image of a healed, 1-year-old condyle fracture in a 63-year-old woman. (B) A virtual condylectomy is performed after the engineer has corrected the yaw, pitch, and roll deformities.
the maxilla and mandible are also established by correcting deformities of yaw, pitch, and roll. Lastly, virtual condylectomies are performed (Fig. 12). It is this last step that differentiates combined orthognathic and temporomandibular joint
reconstruction CASS from that of traditional orthognathic surgery. The condylectomies are performed approximately 5 mm below the sigmoid notch, if anatomy allows, to create space for the fossa component of the prosthesis.
Fig. 13. (A) Stereolithographic model reflecting a virtual surgical plan. (B) Wax-up of the alloplastic joint prosthesis on the stereolithographic model. (C) Virtual cutting guide for the condylectomy. (D) Actual cutting guide used during surgery.
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Nale Once the virtual condylectomy is performed, Medical Modeling will produce a stereolithographic model reflecting the virtual reconstruction of the maxilla and mandible. It is from this model that the custom joints will be manufactured. To insure accuracy of the location of the condylectomy, cutting guides may also be fabricated (Fig. 13). The CASS model is also used to generate an intermediate and final interocclusal splint via CAD/CAM technology. Movahed and colleagues46 suggest that for patients undergoing active orthodontics, fabrication of interocclusal splints should be delayed, in relation to fabrication of the stereolithographic model, until 2 weeks before surgery. At that time new dental models should be obtained and incorporated into the virtual plan. This step will improve the accuracy of the splints. The newly created custom joints and interocclusal splints are then used to transition the virtual plan to the surgical phase of treatment. Surgery is sequenced by first positioning a K-wire into nasion as a vertical reference. Bilateral or unilateral condylectomy and unilateral sagittal split are performed. Next, the patient is placed into MMF with the intermediate splint interposed. If the patient is undergoing a unilateral sagittal split, the proximal and distal segments are fixated while the surgeon is still working in the patient’s mouth. Otherwise, the joint prosthesis is then secured. Next, MMF is released and intermediate occlusion confirmed, followed by the Le Fort I osteotomy. The patient is then placed into MMF with the final splint interposed and the maxilla is secured into its final vertical position. MMF is released and the final occlusion is confirmed. The assessment phase of the treatment protocol is accomplished by superimposing a postoperative CT scan or CBCT scan and the virtually planned models. The software engineers at Medical Modeling Inc will overlay static anatomic landmarks of the cranium. The difference in position of specific landmarks of the maxilla and mandible can then be measured.
SUMMARY The role of orthognathic surgery in the treatment of TMD has been debated for years. The difficulty in establishing a cause-and-effect relationship between orthognathic surgery and improvement in symptoms stems from the multifactorial nature of TMD combined with variables in surgical technique. As a result, it is advocated that TMD and dentofacial deformities be treated independent of one another. Most advocate the treatment of TMD first. Only once symptoms have improved, may treatment of the skeletal malocclusion be
addressed. Also, understanding that TMD can potentially worsen following orthognathic surgery, it is important to modify the surgical treatment plan to minimize the risk of exacerbation of TMJ pain, dysfunction, and condylar resorption. Lastly, those patients with end-stage TMD and a dentofacial deformity may require combined orthognathic surgery and alloplastic TMJ reconstruction. The success of this surgery greatly depends on the experience of the surgeon. However, the efficiency and accuracy of the procedure can be optimized with the use of virtual surgical planning.
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and bimaxillary osteotomies in patients with anterior open bite. A clinical and radiological study. Int J Oral Maxillofac Surg 1998;27:81–91. Hwang SJ, Haers PE, Sailer HF. The role of a posteriorly inclined condylar neck in condylar resorption after orthognathic surgery. J Craniomaxillofac Surg 2000;28:85–90. Hwang SJ, Haers PE, Zimmermann A, et al. Surgical risk factors for condylar resorption after orthognathic surgery. Oral Surg Oral Med Oral Pathol 2000;89: 542–52. Gunson MJ, Arnett GW, Milam SB. Pathophysiology and pharmacologic control of osseous mandibular condylar resorption. J Oral Maxillofac Surg 2012; 70:1918–34. Handelman CS, Greene CS. Progressive/Idiopathic condylar resorption: an orthodontic perspective. Semin Orthod 2013;19:55–70. Joss CU, Vassalli IM. Stability after bilateral sagittal split osteotomy advancement surgery with rigid internal fixation: a systematic review. J Oral Maxillofac Surg 2009;67:301–13. Kobayashi T, Izumi N, Kojima T, et al. Progressive condylar resorption after mandibular advancement. Br J Oral Maxillofac Surg 2012;50:176–80. Kawamata A, Fujishita M, Nagahara K, et al. Threedimensional computed tomography evaluation of postsurgical condylar displacement after mandibular osteotomy. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 1998;85:371–6. Scheerlinck JP, Stoelinga PJ, Blijdorp PA, et al. Sagittal split advancement osteotomies stabilized with miniplates. 2-5 years follow-up. Int J Oral Maxillofac Surg 1994;23:127–31. Crawford JG, Stoelinga PJ, Blijdorp PA, et al. Stability after reoperation for progressive condylar resorption after orthognathic surgery: report of seven cases. J Oral Maxillofac Surg 1994;52:460–6. Dela Coleta KE, Wolford LM, Goncalves JR, et al. Maxillo-mandibular counter-clockwise rotation and mandibular advancement with TMJ Concepts total joint prostheses part I – skeletal and dental stability. Int J Oral Maxillofac Surg 2009; 38:126–38. Gelesko S, Markiewicz MR, Weimer K, et al. Computer-aided orthognathic surgery. Atlas Oral Maxillofac Surg Clin North Am 2012;20(1):107–18. Xia JJ, Gateno J, Teichgraeber JF. New clinical protocol to evaluate craniomaxillofacial deformity and plan surgical correction. J Oral Maxillofac Surg 2009;67:2093–106. Gateno J, Xia JJ, Teichgraeber JF. Clinical feasibility of computer-aided surgical simulation (CASS) in the treatment of complex craniomaxillofacial deformities. J Oral Maxillofac Surg 2007;65:728. Xia JJ, Gateno J, Teichgraeber JF. Three-dimensional computer-aided surgical simulation for
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Nale maxillofacial surgery. Atlas Oral Maxillofac Surg Clin North Am 2005;13(1):25–39. 42. Hsu SS, Gateno J, Bell RB, et al. Accuracy of a computer-aided surgical simulation protocol for orthognathic surgery: a prospective multicenter study. J Oral Maxillofac Surg 2013;71:128–42. 43. Xia JJ, Gateno J, Teichgraeber JF, et al. Accuracy of the computer-aided surgical simulation (CASS) system in the treatment of patients with complex craniomaxillofacial deformity: a pilot study. J Oral Maxillofac Surg 2007;65(2):248–54. 44. Sun Y, Luebbers H, Agbaje JO, et al. Accuracy of upper jaw positioning with intermediate splint fabrication after virtual planning in bimaxillary
orthognathic surgery. J Craniofac Surg 2013;24: 1871–6. 45. Zinser MJ, Sailer HF, Ritter L, et al. A paradigm shift in orthognathic surgery? A comparison of navigation, computer-aided designed/computer-aided manufactured splints, and “classic” intermaxillary splints to surgical transfer of virtual orthognathic planning. J Oral Maxillofac Surg 2013;71:2151. e1–21. 46. Movahed R, Teschke M, Wolford LM. Protocol for concomitant temporomandibular joint custom-fitted total joint reconstruction and orthognathic surgery utilizing computer-assisted surgical simulation. J Oral Maxillofac Surg 2013;71:2123–9.
KEY POINTS
The role of orthognathic surgery for the correction of dentofacial deformities is widely accepted. However, its role in the treatment of temporomandibular joint disorders (TMD) is quite controversial. There are numerous studies that show improvement of temporomandibular joint (TMJ) dysfunction1–3 following orthognathic surgery, whereas there are just as many that show no significant improvement or even worsening of symptoms following surgery.4,5 Interestingly, data also suggest that TMD patients will show some improvement in symptoms with simply the passage of time; this poses the question as to whether or not improvement of symptoms occurs as a result of surgery or due to the cyclic nature of TMD. It should also be noted that a small percentage of asymptomatic patients who undergo orthognathic surgery actually develop TMD symptoms. With these facts under consideration, one can infer
that orthognathic surgery cannot predictably treat TMD. Instead, surgeons should simply recognize that TMD coexists in a subset of patients requiring orthognathic surgery for the correction of a skeletal malocclusion. Therefore, TMD and skeletal malocclusions should be treated as separate entities. Given the potential for TMD symptoms to worsen following orthognathic surgery, it is important to recognize those patients with TMD and manage them independently of the dentofacial deformity. Most advocate that this should be done before planned orthognathic surgery. Once symptoms have significantly improved or resolved, focus may then shift to the orthognathic phase of treatment. The astute surgeon must then recognize those patients with a high risk of surgical relapse related to postoperative condylar remodeling and modify their treatment plans and surgical
Disclosures: None. a Department of Oral and Maxillofacial Surgery, Louisiana State University Health Science Center, New Orleans, LA, USA; b Private Practice, Carolina’s Center for Oral and Facial Surgery, 8840 Blakeney Professional Drive, Suite 300, Charlotte, NC 28277, USA * Private Practice, Carolina’s Center for Oral and Facial Surgery, 8840 Blakeney Professional Drive, Suite 300, Charlotte, NC 28277. E-mail address: [email protected] Oral Maxillofacial Surg Clin N Am - (2014) -–http://dx.doi.org/10.1016/j.coms.2014.08.012 1042-3699/14/$ – see front matter Ó 2014 Elsevier Inc. All rights reserved.
oralmaxsurgery.theclinics.com
Orthognathic surgery cannot be used as a predictable treatment of temporomandibular joint disorders (TMD). TMD symptoms should be treated independent of dentofacial deformities. Orthognathic surgery treatment plans should be modified in TMD patients to minimize exacerbation of symptoms. Patients with a class II malocclusion secondary to condylar resorption should be managed carefully due to their high risk of surgical relapse. Virtual surgical planning has improved the accuracy of combined orthognathic surgery and alloplastic temporomandibular joint reconstruction.
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Nale technique to minimize the potential for early and late postoperative malocclusion (Box 1). TMD can be defined as a collection of signs and symptoms related to the masticatory system. Those signs and symptoms include TMJ pain, pain associated with the muscles of mastication, headache, limited mouth opening, and joint noise. It has been reported that at least one of these symptoms occurs in approximately 50% of all patients seeking treatment of skeletal malocclusion.1,6 These patients require a thorough workup to establish the primary cause of their TMD symptoms. The work-up for TMD should include a history, physical examination, radiologic examination, and laboratory evaluation if indicated.
HISTORY A detailed questionnaire given to the patient before the initial appointment is the typical avenue to assemble the collection of TMD symptoms. The surgeon’s interview with the patient should focus on the chief complaint and symptom descriptors such as location, onset of occurrence, condition or character, alleviating or aggravating factors, timing, and so on.
PHYSICAL EXAMINATION Evaluation of the patient’s mandibular range of motion should be detailed. Pain-free maximum incisor opening should be noted, followed by maximum opening with passive stretching. The onset and location of pain during opening should also be recorded because this may help in the establishment of the origin of pain. Next, the muscles of mastication should be evaluated. Each muscle group should be palpated individually and assessed for pain, spasms, or fasciculations. Next, the joints should be loaded by having the patient bite on a tongue blade. Contralateral pain may indicate an intracapsular origin of pain, where ipsilateral pain may suggest a muscular origin. Next, the lateral and posterior aspects of the condyles
Box 1 Primary goals of orthognathic surgery on the TMJ patient Identify cause of TMD symptoms Successfully treat TMD symptoms Correct the dentofacial deformity Minimize the risk of relapse Minimize the risk of postoperative TMD symptoms
should be palpated. Palpation is useful for detecting intracapsular pain and joint noise and for establishing the amount of translation of the condylar head during mouth opening. Lastly, an otoscopic examination should be performed to rule out any potential cause for pain located within the ear.
RADIOLOGIC EXAMINATION The panoramic radiograph is useful for the screening of the mandibular condyle and its relationship to the glenoid fossa. It also allows for visualization of the coronoid process of the mandible. Computed tomography (CT) and cone beam computed tomography (CBCT) allow for a more detailed and 3-dimensional view of TMJ. These modalities allow for the visualization of any asymmetries, cortical erosions, subchondral cysts, tumors, heterotopic bone, ankylosis, or any other bony abnormality. Newer software also allows serial images to be superimposed to evaluate for active growth or resorption (Fig. 1). However, a panoramic radiograph, CT, or CBCT cannot visualize the TMJ disc. Magnetic resonance imaging is considered the “gold standard” for the evaluation of the soft tissues of the joint. Its multiplanar images allow for direct visualization of disc position at rest and during mouth opening. On occasion, a technetium 99 bone scan may be indicated. This modality is sensitive in the detection of bone activity such as remodeling or resorption. Unfortunately, it cannot differentiate between the two.
LABORATORY EVALUATION Laboratory testing is generally reserved for those patients who are suspected to have a systemic disease process. An erythrocyte sedimentation rate and C-reactive protein may be ordered to check for these acute phase reactants. A positive test result indicates the presence of a systemic inflammatory process, but is not specific for the cause. More specific tests for various immune factors such as rheumatoid factor and antinuclear antibody may also be indicated. Once the appropriate data have been collected, an accurate diagnosis can be established and the patient treated appropriately. Reversible measures are indicated as the first line of treatment. Such reversible measures include patient education, medications, physical therapy, and occlusal splint therapy. Generally patients respond favorably to this form of treatment, but occasionally pain and TMJ dysfunction persist. In this subset of patients, irreversible treatments such as trigger point injections, botox
Orthognathic Surgery and the TMJ Patient
Fig. 1. Superimposition of cone-beam CT scans of the same patient taken 1 year apart.
injections, arthrocentesis, arthroscopy, or even open arthroplasty can improve symptoms refractory to conservative therapy (Box 2). If a patient fails to respond to these treatments, there is no reason to think that they will improve with orthognathic surgery. Fig. 2 suggests an algorithm for the treatment of TMD symptoms in patients with a dentofacial deformity. Although treatment of symptomatic disc derangements is typically performed before any planned orthognathic procedure, some argue that it is safe and predictable for both to be done simultaneously. Wolford7 suggests that the benefits of concomitant surgery include the following: 1. Requires one operation and general anesthetic 2. Balances occlusion, TMJs, jaws, and neuromuscular structures 3. Decreases overall treatment time 4. Eliminates unfavorable TMJ sequelae that can occur when performing orthognathic surgery only 5. Avoids iatrogenic malocclusion that can occur when performing open TMJ surgery only The case against concomitant surgery is that the condyle-fossa relationship becomes vulnerable to the experience of the surgeon.8 That is, there is potentially a higher chance of postoperative malocclusion related to a change in the condylefossa relationship following surgery.
Box 2 Treatment of TMD symptoms in patients with a dentofacial deformity Reversible Treatment of TMD Patient Education Medications Nonsteroidal antiinflammatory drugs (antiRA meds) Muscle relaxants Antidepressants Physical Therapy ROM exercises Passive stretching Spray and stretch Ultrasound Transcutaneous electrical nerve stimulation Occlusal Splint Therapy Irreversible Treatment of TMD Trigger Point Injections Botox Arthrocentesis Arthroscopy Open Arthroplasty
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Fig. 2. Flow diagram and treatment algorithm for patients with a dentofacial deformity and TMD symptoms. NSAID, nonsteroidal antiinflammatory drug.
Orthognathic Surgery and the TMJ Patient SURGICAL CONSIDERATIONS UNIQUE TO SPECIFIC SKELETAL MALOCCLUSIONS Once a patient has responded to the treatment of TMD symptoms, correction of the dentofacial deformity may be addressed. Surgical patients will likely present with a class II or class III skeletal malocclusion with or without asymmetry. Before any surgical treatment plan is formulated, the surgeon should be familiar with the jaw relationships that are more susceptible to the development of postoperative pain, TMJ dysfunction, and condylar resorption. Only with this knowledge can a treatment plan be tailored to minimize the patient’s risk.
Class III Malocclusion Patients having a class III skeletal malocclusion are the least likely of all jaw relationships to have preoperative TMD. However, the risk of developing postoperative TMD does exist. Therefore, they should be managed accordingly. Class III patients undergoing a bilateral sagittal split osteotomy (BSSO) do show some degree of postoperative posterior or lateral displacement of the condyle, but in large this does not cause a significant change in TMJ disc position nor result in significant postoperative pain.9–11 Therefore, a surgeon should have no reservations using this technique when performing mandibular setback surgery in patients with a history of TMD. An intraoral vertical ramus osteotomy (IVRO) has been advocated by some as the technique of choice in TMD patients with a class III skeletal malocclusion (Fig. 3). The rational is that an IVRO will result in an anterior and inferior displacement of the condyle. This displacement increases the joint space and promotes disc reduction in joints with disc displacement with reduction or recent progression to disc displacement without reduction.12 Hu and colleagues13 showed that 75% of patients undergoing an IVRO had an improvement or resolution of TMJ pain and no asymptomatic patients developed new pain, whereas only 40% of patients undergoing BSSO showed improvement in symptoms and 8% of asymptomatic patients developed new symptoms. The debate over which surgery to perform exists because patients undergoing IVRO must be placed in maxillomandibular fixation (MMF) for an extended period of time postoperatively; this may increase the risk of developing limited mouth opening. Also, because of the condylar sag that occurs as a result of an IVRO, the condyle may reseat in a more superior position, due to muscle pull, following the release of MMF. Consequently, this would lead to an open-bite deformity.
Fig. 3. Intraoral vertical ramus osteotomy. This surgical option may minimize postoperative TMD symptoms in patients requiring mandibular setback.
Class II Malocclusion—Progressive/Idiopathic Condylar Resorption It has been proposed that TMJ remodeling can be both functional and dysfunctional.14–18 Functional remodeling involves morphologic changes of the articular surfaces of the TMJ that does not cause any significant alterations of the joint or the occlusion. Conversely, remodeling of the TMJ is considered to be dysfunctional if the morphologic changes lead to a loss of condylar-ramus height, resulting in mandibular retrusion and a class II malocclusion. In some, it may also lead to an anterior open bite. Dysfunctional remodeling has historically been termed condylar resorption. Condylar resorption may occur as a result of several reasons. A few examples include systemic and local arthritidis and trauma. If no obvious cause is identified, it is termed idiopathic condylar resorption (ICR). Patients with a history of condylar resorption pose a difficult challenge to the treating orthodontist and orthognathic surgeon. The difficulty arises because any treatment that causes excessive mechanical loading may predispose the patient to further condylar resorption and the resulting class II open-bite deformity (Fig. 4). The surgical treatment of class II open-bite patients usually involves
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Fig. 4. Cephalometric radiographs depicting postoperative relapse following orthognathic surgery for correction of a class II skeletal malocclusion. (A) Pre-op. (B) Post-op day 1. (C) Completion of orthodontics at 3 months postop. (D) 3 years post-op.
a Le Fort I osteotomy in conjunction with a bilateral sagittal split of the mandible, with or without counterclockwise rotation of the maxillomandibular complex. This combination of procedures increases the mechanical load of the TMJ19 and may result in postsurgical relapse. The key to successful treatment is recognition of those patients who are at high risk for postsurgical condylar resorption and to modify treatment to minimize their risk. Predisposing factors for developing postsurgical relapse secondary to condylar resorption have been well documented. Patients with systemic diseases such as rheumatoid arthritis, scleroderma, systemic lupus erythematosus, and other vascular collagen diseases have been reported as high risk.20–23 Predisposing factors for ICR include TMJ dysfunction, being a young woman, having a high mandibular plane angle, and having a posteriorly inclined condylar neck.21,23–29
Preoperatively, patients with a systemic disease should be referred to a rheumatologist for evaluation and treatment. It has been suggested that all high-risk patients be placed on antiinflammatory medication, tumor necrosis factor a inhibitors, or matrix metalloproteinase inhibitors, because targeted pharmacotherapy might be able to prevent further condylar resorption.30 Occlusal splints are also recommended for those patients with TMJ pain and dysfunction. The splint serves 2 purposes. The first purpose is to limit joint loading; the second is to determine cessation of the resorptive process. Patients are fitted with a splint with registered contact of the mandibular teeth. If the lower incisors lose contact over time, this indicates active resorption.31 Serial radiologic imaging, orthopantogram and cephalometric radiographs, and CBCT can be used to evaluate change in condylar shape. A technetium 99 bone scan may also be useful in determining active resorption. Timing of surgery
Orthognathic Surgery and the TMJ Patient should also be strongly considered. ICR is most active in the teenage years and mid 20s; therefore, surgeons should consider waiting until after the age of 25 years to correct the dentofacial deformity. Intraoperatively, special considerations exist for patients who are at a high risk of developing postoperative condylar resorption. Joss and Vassalli32 reported long-term relapse (condylar resorption) for cases treated with bicortical screws (2%–50.3%), whereas miniplates had comparatively much less relapse (1.5%–8.9%). Arnett and Gunson26 relate this statistical difference to condylar torquing as a result of bicortical screws displacing the proximal segment during fixation of BSSOs. He, therefore, recommends the use of monocortical miniplates for fixation of BSSOs (Fig. 5). If possible, one might also consider limiting the surgical correction to just the maxilla. Hoppenreijs and colleagues27 reported that the incidence of condylar resorption after surgery performed only on the maxilla for correction of class II open bite was less than that after bimaxillary osteotomies (9% compared with 23%). Lastly, if bimaxillary surgery is required, one might consider minimizing mandibular advancement because larger advancements stretch the surrounding soft-tissue components and this tension can lead to greater compression and mechanical loading of the condyle, resulting in resorption.33–35 Postsurgical management should include medications as needed, class II elastics, and occlusal splint therapy after debanding. Patients should be observed on a regular basis because relapse
Fig. 5. Sagittal split osteotomy using miniplate fixation for mandibular advancement.
usually presents with an anterior open bite between 6 months and 3 years following surgery.19 It should also be noted that repeating an osteotomy on the condylar resorption patient whose first orthognathic surgery was unsuccessful has close to a 50% failure rate reported in the literature.19,25,36 To minimize failure rate, total joint replacement may be considered, especially in those patients with symptomatic or active resorption (Fig. 6).
COMBINED ORTHOGNATHIC SURGERY AND ALLOPLASTIC TEMPOROMANDIBULAR JOINT RECONSTRUCTION Occasionally, a patient may present with both a skeletal-facial deformity and an end-stage TMJ pathologic condition. In this scenario, orthognathic surgery combined with alloplastic TMJ reconstruction should be considered. Commonly, the dentofacial deformity occurs as a result of the TMJ disease due to resorption or decreased condylar growth. Often times these patients have had numerous failed treatment attempts or suffer from chronic joint pain or dysfunction. TMJ disorders commonly associated with skeletal-facial deformities include reactive arthritis, condylar hyper- or hypoplasia, ICR, congenital deformation, trauma, or other end-stage TMJ pathologic conditions. These common TMJ disorders often result in a loss of condylar-ramus height. Patients with advanced disorders will have a steep mandibular plane angle, loss of chin projection, and possibly an anterior open bite. Their chief complaints may include joint or facial pain, difficulty chewing, and esthetics. For patients diagnosed with end-stage TMJ pathologic condition, one might consider a combination of orthognathic surgery and alloplastic joint reconstruction (Fig. 7). For unilateral TMJ pathologic condition, one would consider a Le Fort I osteotomy combined with a mandibular unilateral sagittal split and total joint reconstruction on the contralateral side. For bilateral TMJ pathologic condition, one would consider a Le Fort I osteotomy combined with a bilateral total joint reconstruction. TMJ reconstruction and mandibular advancement with custom alloplastic total joint prostheses in conjunction with maxillary osteotomies, for counterclockwise rotation of the maxillomandibular complex, has been shown to be a stable procedure.37 However, the surgery requires meticulous planning to restore form and function to the patient. The difficulty of the surgery arises from the fact that the joint prosthesis must be manufactured to correspond with the planned new position of the maxilla and mandible. Any inaccuracy may
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Fig. 6. (A, B) Total joint reconstruction used to correct an open-bite malocclusion after surgical relapse following orthognathic surgery. This patient had developed chronic pain and limited mouth opening before joint replacement.
result in a persistent malocclusion and compromised facial esthetics. Traditionally, planning begins with cephalometric analysis to predict the final position of the maxillary incisors; this likely requires a counterclockwise rotation of the maxillomandibular complex. Jaw relation records are taken and transferred to stone models. Model surgery based off of the cephalometric analysis is then performed to produce an intermediate and final splint. Also, a 2-piece stereolithographic model of the patient’s skull is fabricated from a preoperative CT scan. Bilateral condylectomies or a condylectomy and sagittal split osteotomy are performed on the model (Fig. 8). Once completed, the intermediate splint is used to establish the new position of the mandible (Fig. 9). The stereolithographic model is then sent to TMJ Concepts (Ventura, CA, USA) for a wax-up and ultimately, final production of the patient-specific joint prosthesis. With this method, the joints are placed first during surgery and the final position of the maxilla is established off of the new position of the mandible. During the planning phase of treatment, there are many steps in which inaccuracies may occur. Errors with impressions, bite registration, and face-bow transfer would result in inaccurate mounted stone models. Of course this would then perpetuate into an intermediate splint that places the mandible into a position other than that which is planned. Another step that may introduce error during planning is when the intermediate occlusion is established on the stereolithographic model. It is very common for these models to have gross inaccuracies in tooth anatomy (Fig. 10). There are 2 reasons for this. The first is that patients typically have their images taken in the CT scanner with their mouths closed. Having their upper and lower teeth touch during
the imaging process ultimately distorts the image quality of the occlusal surfaces of the teeth. The other reason is that metallic restorations cause scattering of the image. This scattering is then transferred to the stereolithographic model. Regardless of the cause, the surgeon may find it difficult to seat the intermediate splint onto the model because of these inaccuracies. If the upper and lower teeth are not placed into the exact relationship relative to the stone model, the joints will be fabricated based off of an inaccurate mandibular position. This inaccuracy would then be transferred to the patient’s final occlusion.
VIRTUAL SURGICAL PLANNING Recently, there has been a paradigm shift in orthognathic surgery planning. To minimize the inaccuracies associated with traditional planning methods, it is becoming more common for surgeons to plan surgeries virtually using computeraided surgical simulation (CASS). Gelesko and colleagues38 described CASS as a method that generally consists of 4 phases: 1. Data acquisition phase: clinical examination with bite registrations and anthropometric measurements; radiographic examination/CT scan 2. Planning phase: importation of 3D CT data into proprietary planning software 3. Surgical phase: translation of the virtual surgical plan to patients using stereolithographic models, cutting guide stents, occlusal splints, or intraoperative navigation 4. Assessment phase: evaluation of the accuracy of virtual surgical plan transfer using intraoperative or postoperative CT imaging It has been demonstrated that the CASS protocol39 is not only feasible40,41 but also can
Orthognathic Surgery and the TMJ Patient
Fig. 7. (A–D) This patient developed facial asymmetry, chronic pain, and limited mouth opening following an undiagnosed condyle fracture as a child. A treatment plan consisting of a left total joint replacement in conjunction with orthognathic surgery was chosen due to the end-staged nature of the left joint.
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Fig. 8. A 2-piece stereolithographic model depicting a left-sided unilateral sagittal split performed in conjunction with a right-sided total joint replacement for the correction of a skeletal malocclusion.
Fig. 10. The occlusal surfaces of the teeth are grossly distorted on this stereolithographic model. The distortion may occur as a result of scatter from the CT scan or if the patient had their teeth occluded while taking the CT scan.
accurately and consistently be transferred to the patient’s maxilla and mandible at the time of surgery.42–45 Once the final position of the occlusion is established, an intermediate and final splint can be manufactured based on the virtual image. This technique may also be used to improve the accuracy of combined orthognathic and joint reconstruction surgery. Planning begins with the data acquisition phase of the CASS system. Natural head position is established with either fiducial markers placed onto the patient’s face along the true vertical and horizontal lines or with the use of a gyroscope. Next, another fiducial marker is placed into a bite jig and placed into the patient’s mouth, which captures an occlusal record. With the fiducial markers in place, a CT or CBCT scan is taken. Stone models of the patient’s occlusion are then obtained and placed into the previously
used bite jig. The stone models are then digitized with either a laser surface scanner or a CBCT scanner. Lastly, the final occlusion is established on the stone models and then scanned. The planning phase begins by uploading the Digital Imaging and Communications in Medicine data from CT scans or CBCT scans and digital models obtained from a laser scanner to a thirdparty service provider to facilitate software manipulation and splint fabrication (Medical Modeling Inc, Golden, CO, USA). The software engineers then integrate the different datasets to create an accurate digital image of the patient (Fig. 11). Next, a planning session involves establishing the final position of the maxilla based off of the desired incisor position relative to the upper lip. Next, the mandibular position is established using the predetermined final occlusion. Symmetry of
Fig. 9. The intermediate occlusion is established on the stereolithographic model using an acrylic splint fabricated from dental stone models following traditional model surgery.
Fig. 11. Datasets from a CT or CBCT and dental stone models are integrated to create an accurate digital image of the patient’s bony skeleton and teeth.
Orthognathic Surgery and the TMJ Patient
Fig. 12. (A) Virtual image of a healed, 1-year-old condyle fracture in a 63-year-old woman. (B) A virtual condylectomy is performed after the engineer has corrected the yaw, pitch, and roll deformities.
the maxilla and mandible are also established by correcting deformities of yaw, pitch, and roll. Lastly, virtual condylectomies are performed (Fig. 12). It is this last step that differentiates combined orthognathic and temporomandibular joint
reconstruction CASS from that of traditional orthognathic surgery. The condylectomies are performed approximately 5 mm below the sigmoid notch, if anatomy allows, to create space for the fossa component of the prosthesis.
Fig. 13. (A) Stereolithographic model reflecting a virtual surgical plan. (B) Wax-up of the alloplastic joint prosthesis on the stereolithographic model. (C) Virtual cutting guide for the condylectomy. (D) Actual cutting guide used during surgery.
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Nale Once the virtual condylectomy is performed, Medical Modeling will produce a stereolithographic model reflecting the virtual reconstruction of the maxilla and mandible. It is from this model that the custom joints will be manufactured. To insure accuracy of the location of the condylectomy, cutting guides may also be fabricated (Fig. 13). The CASS model is also used to generate an intermediate and final interocclusal splint via CAD/CAM technology. Movahed and colleagues46 suggest that for patients undergoing active orthodontics, fabrication of interocclusal splints should be delayed, in relation to fabrication of the stereolithographic model, until 2 weeks before surgery. At that time new dental models should be obtained and incorporated into the virtual plan. This step will improve the accuracy of the splints. The newly created custom joints and interocclusal splints are then used to transition the virtual plan to the surgical phase of treatment. Surgery is sequenced by first positioning a K-wire into nasion as a vertical reference. Bilateral or unilateral condylectomy and unilateral sagittal split are performed. Next, the patient is placed into MMF with the intermediate splint interposed. If the patient is undergoing a unilateral sagittal split, the proximal and distal segments are fixated while the surgeon is still working in the patient’s mouth. Otherwise, the joint prosthesis is then secured. Next, MMF is released and intermediate occlusion confirmed, followed by the Le Fort I osteotomy. The patient is then placed into MMF with the final splint interposed and the maxilla is secured into its final vertical position. MMF is released and the final occlusion is confirmed. The assessment phase of the treatment protocol is accomplished by superimposing a postoperative CT scan or CBCT scan and the virtually planned models. The software engineers at Medical Modeling Inc will overlay static anatomic landmarks of the cranium. The difference in position of specific landmarks of the maxilla and mandible can then be measured.
SUMMARY The role of orthognathic surgery in the treatment of TMD has been debated for years. The difficulty in establishing a cause-and-effect relationship between orthognathic surgery and improvement in symptoms stems from the multifactorial nature of TMD combined with variables in surgical technique. As a result, it is advocated that TMD and dentofacial deformities be treated independent of one another. Most advocate the treatment of TMD first. Only once symptoms have improved, may treatment of the skeletal malocclusion be
addressed. Also, understanding that TMD can potentially worsen following orthognathic surgery, it is important to modify the surgical treatment plan to minimize the risk of exacerbation of TMJ pain, dysfunction, and condylar resorption. Lastly, those patients with end-stage TMD and a dentofacial deformity may require combined orthognathic surgery and alloplastic TMJ reconstruction. The success of this surgery greatly depends on the experience of the surgeon. However, the efficiency and accuracy of the procedure can be optimized with the use of virtual surgical planning.
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