Computer simulation in the daily practice of orthognathic surgery

Abstract

The availability of computers and advances in imaging, especially over the last 10 years, have allowed the adoption of three-dimensional (3D) imaging in the office setting. The affordability and ease of use of this modality has led to its widespread implementation in diagnosis and treatment planning, teaching, and follow-up care. 3D imaging is particularly useful when the deformities are complex and involve both function and aesthetics, such as those in the dentofacial area, and for orthognathic surgery. Computer imaging involves combining images obtained from different modalities to create a virtual record of an individual. In this article, the system is described and its use in the office demonstrated. Computer imaging with simulation, and more specifically patient-specific anatomic records (PSAR), permit a more accurate analysis of the deformity as an aid to diagnosis and treatment planning. 3D imaging and computer simulation can be used effectively for the planning of office-based procedures. The technique can be used to perform virtual surgery and establish a definitive and objective treatment plan for correction of the facial deformity. In addition, patient education and follow-up can be facilitated. The end result is improved patient care and decreased expense.

Advances in computing have resulted in the use of computers in every aspect of daily life. This has also included the medical field, where significant advances in biotechnology, biosensors, and medical informatics have been incorporated into routine patient care. Computer simulation has also benefited from the rapid changes in computing power and display. In addition the development of cone beam computed tomography (CBCT) scans has taken three-dimensional (3D) imaging beyond the exclusive use in hospitals and into the outpatient setting. Thus this imaging has become more available and less expensive, and presents decreased radiation.

In 1965, Gordon Moore sketched out his prediction of the pace of change in silicon technology. Decades later, Moore’s Law remains true, as the number of transistors on a chip roughly doubles every 2 years. As a result, the scale gets smaller and transistor counts climb, increasing device complexity and integration. The cumulative impact of these spiralling increases in capability power, the economy and the Internet. The extrapolation of these current technological trends into the future is based on the fact that these systems are all Web-based and therefore communications barriers are absent.

In the daily practice of maxillofacial and orthognathic surgery, computer simulation provides a number of significant benefits in: (1) evaluation and diagnosis, (2) education of the patient and professionals, (3) simulation and surgical planning, and (4) follow-up. Gossett et al. have outlined a three-fold purpose for computer-simulated predictions: (1) guide the treatment to the desired result, (2) give the patient a reasonable preview of the outcome, and (3) serve as a communicating tool between orthodontist, surgeon, and patient. In reality this applies not only to computer simulation but also to the use of computer-aided visualization in general. To these three points, the following can be added: aid in the diagnosis, and communication is easily expanded via the Internet to other partners for matters such as the fabrication of custom implants. In addition, patient records can be accessed via the Internet when out of the office. These advantages are looked at more closely below.

Evaluation and diagnosis

Clinical evaluation of the patient can now be augmented by assessment of 3D images of the craniofacial skeleton. 3D anatomical relationships are difficult to learn and visualize. This is especially true for those without special training in medicine. Advanced visualization techniques can help people learn better. The use of advanced imaging modalities such as CBCT, surface imaging, serial sections, magnetic resonance imaging (MRI), and scanning digitization improve visualization and lead to a better understanding of the anatomical data and structural relationships. Sophisticated software permits the real-time visualization of 3D images and concomitant two-dimensional (2D) images in all three planes of space. We can now look closely at the temporomandibular joints, sinuses, alveolar bone, and nerves without the need for additional tomograms. Any pathology or malformations are thus more readily recognized. A clearer view of the nasal area including the septum and turbinates is possible.

In the author’s practice, the initial consultation involves an examination of the patient and then an overview of the records. If a CBCT or facial scan and photographs are needed, these are then taken. After these records are obtained, the findings are discussed with the patient, usually during the same visit, and they are shown any abnormalities or pathology using the computer and 3D display. Each operatory is thus equipped with a computer accessing the office network ( Figs 1–3 ).

Fig. 1
Typical workflow scenario. The initial data are acquired from multiple sources such as the CBCT scan, facial surface image, and dental model scans. These are then transferred to the network for database storage and file manipulation. From this, the patient-specific anatomic reconstruction (PSAR) is then created and the treatment planning completed. Thus, all treating doctors can be involved directly in the creation of the plan. Finally, custom implants and splints can be created and data sent directly to the surgical suite for surgical guidance and assistance.

Fig. 2
Computer scan being shown to the patient to allow a better understanding of the condition and for visualization of the planned treatment.

Fig. 3
Airway analysis: 3dMDvultus software platform (3dMD Inc., Atlanta, GA, USA).

The upper airway is a particularly important area that has benefitted greatly from 3D imaging. The 3D size and shape of the upper airway is correlated to obstructive sleep apnea (OSA) and is easily measured using recently developed computer software. The patient-specific airway can then be compared to age-related normal airways and to known airway sizes with obstruction. This is particularly important both in treatment planning for patients who have OSA and in planning orthognathic surgery in order not to impinge on the airway with the planned surgery. CBCT has been particularly revealing in the intra-nasal anatomy, as septal deviation and turbinate hypertrophy can be seen clearly. In surgery for OSA, the maxillomandibular advancement can be better planned based on knowledge of the exact part of the upper airway obstructed and the amount of obstruction.

Education

In the author’s practice there is a computer station in each office that has the ability to display 3D images and simulations. Once the diagnosis has been made, the patient is shown their own images and their condition is described and the specific anatomy shown. It has been found that this results in a more comprehensive understanding of the problem for the patient, which is also clearly apparent. The treatment options are also described at this time, thus allowing the patient more participation in their treatment decisions. In the final treatment planning session, the patient is shown their own 3D simulated images of the proposed surgery. This has been found to be particularly important in orthognathic, sleep, and aesthetic surgery, and can prevent undesirable outcomes when the surgeon and patient have a different concept of the goal to be achieved. Simulated images of the proposed surgery technique are also available to clarify the proposed surgery for the patient. In addition, the education of other professionals, residents, and students is facilitated using this type of presentation. In agreement with the statement of Gossett et al., this gives the patient a reasonable preview of the outcome. In this regard, the simulation technique used in the author’s practice is discussed in greater detail below.

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Jan 17, 2018 | Posted by in Oral and Maxillofacial Surgery | Comments Off on Computer simulation in the daily practice of orthognathic surgery
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