An Overview of Computer-Assisted Navigation: Guiding the Surgeon’s Knife in Maxillofacial Surgery

Introduction

Any surgical treatment plan starts with a perfect diagnosis and adequate information about the lesion, its proximity to adjacent structures and its surrounding anatomical landmarks. In the management of defects and disorders, developmental or acquired in oral and maxillofacial surgery, the main aim is to restore and re-establish facial form, symmetry, and function.^1,2 To achieve the mentioned facial symmetry, form, and function, the correct imaging technique is very important. The oral and maxillofacial region has numerous vascular structures and complicated anatomy which need to be identified and preserved. The basic imaging technique used before oral and maxillofacial surgical procedures usually includes orthopantomography (OPG), Cone Beam Computed Tomography (CBCT), Magnetic Resonance Imaging (MRI), and Computed Tomography scan (CT scan).

With the advancement in imaging technology, it has become easier for surgeons to visualize all the details and obtain large data on the lesion and structures by advanced digital imaging procedures. One such innovation in this field is computer-assisted navigation surgery. It was first put into use in neurosurgical procedures by Wantanabe in the year 1987 and was later introduced in oral surgical procedures.^3,4 It is a minimal invasive technique that permits a direct approach to the target region via a small incision. It utilizes the images in preparing data and split it into – the first part- pre-surgical planning assisted by computer. It comprises pre-operative surgical stimulations with mock-up replicas and threedimensional images to identify the dental implant’s exact size and position, evaluate the treatment plans, and obtain an error-free representation of nearby and underlying vital organs as well as the skeletal anatomy of the patients.⁵ The other part includes navigation, which evolved in the order of —“diagnosis-surgical planning-surgery”. This permit the surgeon to envision the three-dimensional MRI or CT details of the patient in real time and the exact place of surgical instruments on the screen of the monitor. Navigation system requires the amalgamation of imaging and surgical field. This ensures concurrent visualization of various images so that the intraoperative structures can be disclosed. It allows navigation in areas of anatomical sensitivity.

Computer-assisted navigation systems have been developed to upgrade the surgical procedure and reduce intraoperative invasiveness, thus it becomes a minimal invasive surgical technique with improved accuracy.⁶

This article aims to shortly review the information available on computer-assisted navigation systems, their clinical applications, and the scope of navigation surgery systems in oral surgery.

The computer navigation system resembles the automobile’s Global Positioning System (GPS). It consists of three components —a localizer which is alike a space satellite, a surgical probe which acts as the waves released by the GPS, and a CT scan data set which corresponds to a road chart.⁷ It can also be used as Positron emission tomography (PET scan) or magnetic resonance imaging (MRI). There are major two kinds of accessible surgical navigation systems nowadays which include optical tracking systems and electromagnetic tracking systems.

The variance between the electromagnetic tracking systems and optical tracking systems

Optical tracking systems and electromagnetic tracking systems differ mainly in the method of providing information to the surgeon.

The optical navigation system utilizes infrared sensors with light reflectors attached to the patient’s head and a hand-held probe. The system camera on the computer displays the light-emitting structure and instrument. In this way, it becomes possible to trace the instrument and its position in the surgical field.⁸

The electromagnetic navigation system utilizes the electromagnetic field and the reference points fixed on the patient’s head along with the wired instrument used by the surgeon in the surgical area. However, its display on the camera system of the computer is not required.⁹

Method of registration

Registration can be done by marker-free technique^10,11 and marker-based technique.^12,13

Marker-free technique^14-16- It depends on the canio-facial anatomy of the patient. It can be done by registering the protuberances of bone and correlating it with the structures detected on the CT scan.

Marker-based technique^17-19- Markers are essential for this method. The markers become evident on the preoperative images and can be detected easily in the patient during the procedure. The markers can be skin adhesive reference markers, dental splints, or boneimplanted screws.

Clinical implementation of navigation surgery

With about ten years of experience, navigation surgery has found various clinical application in oral surgery and have proved to be beneficial. These include:-

Navigation surgery in maxillofacial trauma: Fractures involving orbital and zygomatic regions are encountered more commonly and the treatment becomes difficult and depends mainly on the displacement of the fractured bone and its stability.^20,21 Treatment of orbito-zygomatic fracture is a challenging procedure as this region forms the width of the midfacial and its proper restoration is important for normal form, esthetic, and function.²² The advantage of computer-assisted navigation surgery is the accurate pre-operative preparation leading to precise orbital reconstruction.²³ Navigation surgery in the orbital fracture can be performed using three-dimensional repositioning of the bones with the advantage that the surgeon has three-dimensional pictures of where the virtual bone replica should be rebuilt to obtain uniformity with the uninvolved side. In a study done by Leonard Bergeron et al., 50 patients with major facial fractures were assessed, out of which 28 were treated by the navigation system and 22 were treated without the navigation system. The result showed that the use of the navigation system reduced the surgical time by 36.1%.²⁴

Computer-assisted navigation surgery proves to be a useful method for the correction of complex midfacial orbito-zygomatic fractures in emergency maxillofacial surgery cases.²⁵

Navigation surgery in the removal of foreign bodies:

Removal of foreign bodies from the cranial/ oral-maxillofacial region becomes challenging due to the risk of damaging adjacent vital structures and improper visualization.²⁶ The impacted foreign object may alter the normal anatomy of this region making it even more difficult to operate. Thus, adequate information about the exact location of the foreign object and precise planning of the treatment is necessary to avoid major complications.²⁷ Preoperative CT scanning and three-dimensional image reconstruction make it easier to locate the object and its relation with surrounding structures and blood vessels. Shintaro Sukegawa et al. planned to remove a foreign body impacted in the maxilla using navigation-guided surgery to attempt a minimal invasive procedure. The technique proved to be useful with decreased operative time.²⁸ Location of the foreign body in a three-dimensional space becomes easy and accurate by the navigation system and proves to be effective for foreign body removal.²⁹

Navigation surgery in dentoalveolar surgeries: Removal of deeply impacted teeth, supernumerary teeth, etc. becomes difficult at times. Determining the correct position of the impacted teeth is very important for minimizing the time required for surgery. This leads to less damage to the bone while removing and decreasing post-operative complications.³⁰ Therefore, it is necessary to obtain a three-dimensional image to learn about the position and relation of the tooth with surrounding structures before surgery. The navigation system can be useful for this reason. In a study by Wang et al., ³¹ it was reported that the computer-assisted navigation system gives advantages in the removal of deeply seated impacted teeth which includes:

• Locating the deeply impacted teeth accurately that helps in guiding them to the correct access point, minimizes bone loss and trauma.

• To differentiate between permanent tooth germ and deeply impacted tooth.

• To identify and mark safe margins thus preserving the surrounding vital structures.

Navigation surgery in Orthognathic Surgery: Orthodontic surgery by navigation system ensures to avoid critical structures in approximation. As compared to the conventional methods, navigation surgery proves to be beneficial by the advancement or setback of the maxilla and mandible in an absolute position.³² Navigation systems in distraction osteogenesis permit precise localization of the osteotomy sites, positioning of distractor screw holes, and adjustment of the distractor.³³ A study on 15 patients was done by Giovanni Badiali et al. to determine the absolute accuracy of maxillary repositioning during orthognathic surgery. They suggested that guided navigation makes post-operative outcomes possible for maxillary repositioning.³⁴ Thus, it is attainable to improvise the precision, well-being, and safety of orthognathic surgery by confirming the surgery planned with navigation.³⁵

Conclusion

Advancements and research in the field of medicine continue in the search for the best technique. Computer-assisted navigation can be now recognized as a minimal invasive procedure and prove to be a boon in surgeries in the oral and maxillofacial regions. Navigation surgery is superior to the conventional methods in terms of accuracy, time taken for the surgery, preservation of adjacent structures, precision, and minimalizing complications. The use of a computer-assisted navigation system is useful in performing osteotomy procedures, foreign object removal, and craniofacial fractures which can be performed safely and precisely. A surgical approach in difficult areas, areas that cannot be assessed or visualized directly can be safely done with careful preservation and anatomical attention with a navigation system.

Source(s) of support

Nil

Conflicting Interest

None