Intraoperative cone beam computed tomography in the management of facial fractures

Abstract

Computed tomography is currently the standard in preoperative evaluation of facial fractures, but cone beam computed tomography (CBCT) or digital volume tomography (DVT) offers potential advantages. Intraoperative imaging may facilitate adequate fracture reduction, optimising fracture repair. The aim of this article is to demonstrate the potential benefits of a new mobile CBCT system in a series of patients with complex facial fractures. Intraoperative imaging was performed with the xCAT ENT portable CBCT system. Images were provided in three planes and in a three-dimensional reconstruction. This system was used for intraoperative imaging of 46 consecutive facial trauma patients. The impact of intraoperative CBCT on the management of these cases is described and two select cases are presented to illustrate the potential benefits of this technique. Intraoperative CBCT was successfully performed in all patients and has led to immediate consequences in 12 (26%) cases. In 5 cases, fracture reduction turned out to be insufficient and was further optimized and in 5 other cases the titanium implan (orbital mesh) was not placed in the optimal position and the position was corrected. Bony fragments were detected and removed in 2 cases. Intraoperative imaging provides a number of advantages over post-therapeutic imaging in the management of facial fractures.

Computed tomography (CT) is currently the standard in preoperative evaluation of facial fractures. Cone beam computed tomography (CBCT) or digital volume tomography (DVT) offers potential advantages over CT, including a lower radiation dose and reduced costs. The relatively poor soft-tissue contrast of CBCT is of minor importance in the assessment of bony structures, which makes CBCT an interesting alternative to CT, especially in the assessment of fractures. The value of CBCT in the management of facial fractures has been investigated by various authors. CBCT can provide skull imaging with high geometric accuracy in all planes and with three dimensional (3D) reconstruction. CBCT has proved its usefulness in facial fractures and implantology. The dataset of CBCT can also be used for virtual reconstruction, computer-assisted planning and intraoperative navigation. It can be used for postoperative control imaging to ensure adequate fracture reduction and quality control. A limiting factor of CBCT may be the relatively small field of view compared to CT.

Intraoperative imaging provides a number of potential advantages over post-therapeutic imaging. It may facilitate adequate fracture reduction, thereby optimising fracture repair. In cases of suboptimal reduction requiring surgical revision, the revision can be done immediately in the same surgical setting thus reducing additional interventions and anaesthesia. Czerwinski et al. introduced rapid intraoperative imaging for zygomatic arch fractures by scanning two planes using a C-arm. Although this technique was reported as being potentially helpful in the repair of zygomatic fractures, the two dimensional (2D) imaging appears to be insufficient for the assessment of complex fractures. In 2005, intraoperative 3D imaging based on a C-arm was published by Heiland et al., but the field of view in their series was too small to visualise both zygomatic arches, and the resolution of the images was relatively poor. Pohlenz et al. described their clinical experiences with intraoperative CBCT based on a C-arm in 2007 and 2009 with superior resolution and confirmed the high accuracy of the system, including 3D reconstruction and the clinical usefulness of the system. In two recent publications Terzic and Scolozzi have introduced image guided surgical navigation integrating ‘mirroring’ computational planning based on intraoperative CBCT imaging which could be helpful in patients with bilateral facial fractures. Some authors have described intraoperative imaging based on CT, but the availability of mobile CT scanners is limited. The associated costs and amount of radiation are significant disadvantages.

The advantages of immediate revision or reposition of bone grafts based on the results of intraoperative imaging were demonstrated in a series of patients. Intraoperative imaging offers valuable information in the management of complex facial fractures and CBCT appears to be a suitable imaging technique for this indication. The authors hypothesize that the use of intraoperative CBCT may lead to immediate intraoperative consequences in terms of a correction or optimization of fracture reduction. The aim of this article is to demonstrate the potential benefits of a new mobile CBCT system in a series of patients with complex facial fractures and to assess the percentage of cases in which intraoperative CBCT leads to immediate intraoperative revision.

Materials and methods

Intraoperative imaging was performed with the xCAT ENT portable digital volume tomography system (Xoran Technologies, Ann Arbor, USA). With this system, the patient’s head is placed on a carbon fibre head holder and the gantry rotates 360° around the head. Tube voltage is 120 kV, tube current is 2.5 mA and pulse length is 16 ms. With these settings, the radiation dose for the facial skeleton is 0.41 mSV. The size of the CBCT is 0.813 m × 1.194 m × 1.524 m and it weighs 159 kg. Its concrete use in the operating room is demonstrated in Fig. 1 .

Fig. 1
Three examples illustrating the intraoperative use of the system.

Images are provided in three different planes and in a 3D reconstruction. Reconstruction time is less than 60 s per 600 frames. Slice thickness is 0.4 mm and the field of view is 14 cm (axial) and 24 cm (cross-sectional). For 3D reconstruction, the voxel size is 0.4 mm × 0.4 mm × 0.4 mm and the field of view 230 mm × 230 mm × 144 mm, which allows for scanning of the entire midface.

This system has been used for intraoperative imaging of facial trauma in 46 consecutive patients. The authors report the impact of intraoperative CBCT on the management of these patients and two select cases are presented to illustrate the potential benefits of this new technique. With this design, the project was exempted from an institutional review board approval. The Guidelines of the Helsinki Declaration were followed.

Results

Intraoperative CBCT was feasible in all 46 patients; 38 men and 8 women aged 19–88 years (mean 46 years). The cases were: fractures of the lateral midface (complex zygomatic fractures, 17), panfacial fractures (12), isolated orbital fractures (10), fractures of the mandible (5), and central facial fractures (Le Fort II).

In 12 cases (26%) intraoperative CBCT led to immediate consequences for the intervention. In 5 cases, fracture reduction was insufficient and was optimized further. In 5 cases, the titanium implant (orbital mesh) was not placed in the optimal position and corrected consecutively. Displaced bony fragments were detected and immediately removed in 2 cases.

Case 1

A 70-year-old junk dealer was assaulted in his junkyard and hit on the head and face multiple times with an iron pipe. He presented with a large facial haematoma and multiple lacerations to the head and face. He complained about double vision in all directions and paresthesia in both cheeks but no loss of vision. The initial CT scan showed a panfacial fracture with fractures of the nasoethmoid, both zygomas, both orbital floors, a Le Fort I fracture and damage to a steel plate at the infraorbital rim that was used for the fixation of a fracture of the left zygoma some years ago. The initial appearance is demonstrated in Fig. 2 .

Fig. 2
Preoperative CT: reconstructed coronal (a) and axial (b) plane showing the panfacial fracture (Courtesy of the Institute of Clinical Radiology and Nuclear Medicine, University Hospital Mannheim, Germany).

The fractures were exposed via a bicoronal approach, an infraorbital approach on both sides via a preexisting laceration on the right, and through the scar of a previously performed infraorbital approach on the left as well as via a bilateral transoral approach. After the reduction and rigid fixation of the fractures with a series of titanium plates, (MatrixMIDFACE, Synthes GmbH, Umkirch, Germany) intraoperative imaging was performed, showing insufficient alignment of the fragments of the lateral midface on the left side ( Fig. 3 ).

Fig. 3
Intraoperative imaging showing insufficient fracture reduction of the left zygoma.

After immediate re-exposure, the fracture was again reduced and fixed. The subsequent intraoperative CBCT showed sufficient reduction ( Fig. 4 ). In this case, additional surgery due to insufficient fracture reduction could have been avoided by intraoperative CBCT.

Jan 26, 2018 | Posted by in Oral and Maxillofacial Surgery | Comments Off on Intraoperative cone beam computed tomography in the management of facial fractures
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