- Email: [email protected]
Improved Results in Closed Reduction of Zygomatic Arch Fractures by the Use of Intraoperative Cone-Beam Computed Tomography Imaging
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CRANIOMAXILLOFACIAL TRAUMA
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Improved Results in Closed Reduction of Zygomatic Arch Fractures by the Use of Intraoperative Cone Beam Computed Tomography Imaging Jean-Pierre Johner, MD, DMD,* Daniel Wiedemeier, PhD,y Lukas Hingsammer, MD, DMD,z Thomas Gander, PhD, MD, DMD,x Michael Blumer, MD, DMD,{ and Maximilian E. H. Wagner, MD, DMDk
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Purpose:
The use of intraoperative imaging could help overcome the insufficiency of closed reduction that can result from the absence of visible feedback to evaluate the accuracy of the reduction in isolated zygomatic arch fractures. The aim of the present study was to evaluate the use of intraoperative 3-dimensinoal cone-beam computed tomography (CBCT) to improve the accuracy of reduction, by measuring the remaining cortical step and dislocation angle. We also evaluated the effect of CBCT on the need for repeat surgery.
Patients and Methods: We performed a retrospective cohort study of patients who had undergone zygomatic arch reduction surgery from January 2008 to May 2018. The patients were grouped according to the predictor variables into group A (postoperative radiologic follow-up studies) and group B (intraoperative CBCT imaging studies). The primary outcome variables were the remaining cortical step and dislocation angle compared with the ideal virtually mirrored position. These were assessed as measures of reduction accuracy. The secondary variables included age, gender, surgery duration, and fracture type. Statistical analysis was performed using a robust multiple regression analysis. Results:
The 45 patients were divided into 2 subgroups with 18 patients in the no intraoperative imaging (control) group and 27 patients in the intraoperative imaging group. Insufficient reduction occurred in 1 patient in the group without intraoperative imaging, leading to repeat surgery. No repeat surgery was necessary in the intraoperative imaging group. The remaining cortical step of the intraoperative imaging group was significantly lower than that of the control group (0.18 vs 2.03 mm; P < .001). For the remaining dislocation angle, similar findings were observed but without statistical significance (3.93 vs 7.75 ; P = .58). Conclusions: The use of intraoperative CBCT significantly increased the accuracy of the reduction. Furthermore, the need for repeat surgery was not required for any patient in the intraoperative imaging group with CBCT-guided reduction. Ó 2019 American Association of Oral and Maxillofacial Surgeons J Oral Maxillofac Surg -:1.e1-1.e9, 2019 *Resident, Department of Craniomaxillofacial Surgery, University
Conflict of Interest Disclosures: None of the authors have any relevant financial relationship(s) with a commercial interest.
Hospital Z€ urich, Z€ urich, Switzerland. yResearch Associate, Division of Data Analysis and Statistics,
Address correspondence and reprint requests to Dr Johner:
Department of Statistical Services, University Z€ urich, Z€ urich,
Klinik und Poliklinik f€ ur Mund-, Kiefer-, und Gesichtschirurgie
Switzerland.
Universit€atsSpital Z€ urich, Frauenklinikstrasse 24, Z€ urich, 8091
zResident, Department of Craniomaxillofacial Surgery, University
Switzerland; e-mail: [email protected]
Hospital Z€ urich, Z€ urich, Switzerland. xSenior Physician, Department of Craniomaxillofacial Surgery,
Received May 29 2019 Accepted October 28 2019
University Hospital Z€ urich, Z€ urich, Switzerland.
Ó 2019 American Association of Oral and Maxillofacial Surgeons
{Attending
Physician,
Department
of
Craniomaxillofacial
0278-2391/19/31253-4
Surgery, University Hospital Z€ urich, Z€ urich, Switzerland. kAttending
Physician,
Department
of
https://doi.org/10.1016/j.joms.2019.10.025
Craniomaxillofacial
Surgery, University Hospital Z€ urich, Z€ urich, Switzerland.
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CLOSED REDUCTION OF ZYGOMATIC ARCH FRACTURES AND CBCT
Zygomatic arch fractures will mostly occur as a part of a tripod fracture. Isolated zygomatic arch fractures will account for up to 14% of all zygomatic fractures.1 The indication for surgical treatment will be conclusively justified by the clinical symptoms, including an esthetic facet due to midface asymmetry, which will result in a depressed lateral cheek, and a functional facet due to the masticatory impairment resulting from interference of the dislocated zygomatic arch fragment and condyle. Left untreated, this can result in impaired mouth opening, temporomandibular joint ankylosis, and a depressed, asymmetric cheek. Different classifications have been established by Honig and Merten,2 Ozyazgan et al,3 and Yamamoto et al.4 The typical M- or V-type fractures, classified as Yamamoto type II, Honig and Merten type I, and Ozyazgan type IBV have been reported to have favorable reduction outcomes.5 The original approach for closed reduction of the zygomatic arch fracture through a temporal incision was first described by Gillies et al6 in 1927 and remains widely used today.1,7 Other approaches have included an intraoral incision, a direct cutaneous or transbuccal approach, and a bicoronal approach.8 The indication for open reduction and internal fixation has remained restricted to multifragmented and unstable fractures. Various devices, such as the elevator, Stromeyer hook, curved mosquito forceps, Rowe zygoma elevator, Deschamps needle holder, Foley balloon catheter, and Langenbeck retractor, have been described for reduction of the zygomatic arch.9 To immobilize the bone fragments after reduction, aqua splints and percutaneous wire suture techniques have been used.10,11 Short incision approaches such as the Gillies, direct cutaneous, or intraoral incision approaches, have been commonly used owing to their benefit in minimizing scarring. However, they have the limitations of a blind surgical approach. Surgeons facing the difficulty of reducing the fracture without visualization of the fracture lines have sought for reduction feedback using digital palpation, crepitation sounds, and visible control of symmetry. However, because of the soft tissue swelling that occurs after trauma, these factors have been less reliable.12 The efficacy of reduction could be increased by ultrasound guidance, which has been proved to be accurate in assessing fractured arches, with a sensitivity of 88.2% and specificity of 100%.13 Kim et al11 supplemented the ultrasound procedure with the use of needles as reference points and localization assistance. With the limited use of ultrasound devices for maxillofacial trauma and the complicated operation room setup, few clinics have used such devices. With the increasing availability of 3-dimensional (3D) imaging devices with costs comparable to those for ultrasound
devices, the use of ultrasound devices has remained limited to several clinical centers. In addition, intraoperative 3D imaging has expanded the indications for closed repair by confirming the accuracy of reduction without the need for direct visualization.14 The aim of the present study was to compare closed reduction for isolated zygomatic fractures with and without the use of intraoperative cone-beam computed tomography (CBCT) imaging. We hypothesized that intraoperative CBCT imaging during closed reduction of isolated zygomatic fractures would provide valuable information to surgeons, because the immediate feedback would enable corrective secondary reduction attempts within the first surgery, leading to better results and fewer repeat surgeries. The purpose of the present study was to quantify the effect of intraoperative CBCT imaging by evaluating 2 radiologic measurements: the remaining cortical step and the remaining dislocation angle after closed reduction. Furthermore, we assessed secondary variables such as operation duration, age, gender, and fracture side and type.
Patients and Methods STUDY DESIGN
To address the research purpose, we designed and implemented a retrospective cohort study in accordance with the STROBE (strengthening the reporting of observational studies in epidemiology) guidelines15 and recommendations by Dodson16 on scientific writing. The study population included all patients who had presented to the University Hospital of Z€ urich for the evaluation and management of isolated zygomatic arch fractures from January 2008 to May 2018. All patients included in the present study had provided written informed consent. The ethics committee of the University Hospital of Z€ urich evaluated and approved the study protocol (approval ID, 2018-01166). VARIABLES
The predictor variable was defined by the use of intraoperative 3D CBCT imaging versus none. The implementation of intraoperative 3D CBCT imaging at our clinic occurred in December 2015 and was standard during trauma surgery. The assessed primary variables were 2 radiologic measurements used to quantify the accuracy of the reduction. First, the maximum discrepancy from the ideal position (ie, the remaining cortical step after reduction) in the zygomatic arch after reduction, was measured as the distance in millimeters (Figs 1, 2). Second, similar to the method used by Buller et al,17 the dislocation angle, formed by the secant of the outer cortical shape of the zygoma,
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older than 16 years; 2) closed reduction of unilateral or bilateral isolated zygomatic arch fractures; and 3) treatment period from January 2008 to May 2018. The patients meeting the following criteria were excluded from the study sample: 1) written informed consent not provided; 2) permission not provided for use of patient data; and 3) clinical or radiologic data missing. Patients with dislocated zygomatic arch fractures who had provided written informed consent and had met the inclusion criteria were included in the present study. SURGICAL PROCEDURE
FIGURE 1. Preoperative axial view of computed tomography scan with segmentation of the unaffected side (yellow) and mirrored ideal position of the zygomatic arch (purple) using iPlan (Brainlab). Johner et al. Closed Reduction of Zygomatic Arch Fractures and CBCT. J Oral Maxillofac Surg 2019.
zygomatic arch, and the most dislocated fragment axis, was measured. The secondary variables assessed including the operative time, patient age and gender, fracture side, and association between fracture type (variable vs M type) and the reduction accuracy. The need for revision surgery was regarded as evidence of reduction failure, as captured by the primary variables. DATA COLLECTION METHOD
To be included in the study sample, the patients had to have met the following inclusion criteria: 1) age
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FIGURE 2. Postoperative axial view of computed tomography scan with segmentation of the unaffected side (yellow) and mirrored ideal position of the zygomatic arch (purple) using iPlan (Brainlab). Johner et al. Closed Reduction of Zygomatic Arch Fractures and CBCT. J Oral Maxillofac Surg 2019.
The preoperative measures included CT scans of the viscerocranium to confirm the dislocated zygomatic arch fracture and, as needed, CT scans of the neurocranium to exclude intracerebral lesions. Other measures included blood examinations to exclude coagulation disorders and a thorough anesthetic examination to ensure a minimal risk of undergoing general anesthesia, as needed. The surgical procedure was performed by different surgeons with the experience of a senior attending within the oral and maxillofacial surgery department of the University Hospital of Z€ urich. The surgery was performed within 0 to 14 days after initial trauma. All patients were given preoperative prophylactic antibiotic treatment and disinfection with a povidone–iodine scrub. The chosen surgical approach was either an extraoral transbuccal stab incision or an intraoral incision in the vestibular fold of the maxilla. Reduction was performed using a Stromeyer hook in the extraoral transbuccal approach and either a Stromeyer hook or elevator for an intraoral approach. The choice of the surgical approach and the reduction instrument used was left to the surgeon’s discretion. For those patients who had undergone closed reduction from January 2008 to November 2015, the postoperative follow-up protocol included radiologic examination using CBCT or CT scanning. Any postoperative radiologic follow-up examination performed using 2-dimensional (2D) radiographs (eg, submentovertex projection) was excluded. From December 2015 onward, intraoperative reduction guidance was conducted using 3D intraoperative scanning with a mobile xCAT unit (Xoran Technologies, Ann Arbor, MI). The patients were positioned on an x-ray table. For the duration of the radiologic examination, the personnel within the operation room were limited to the patient, 1 anesthesiologist, and the surgeon. All the persons remaining in the operation room, including the patient, wore lead shielding for the duration of the radiologic examination. The patient was covered with a sterile cover during the radiologic examination, and the correct positioning of the
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CLOSED REDUCTION OF ZYGOMATIC ARCH FRACTURES AND CBCT
patient’s head within the gantry was confirmed by the built-in laser pointer (Fig 3). The resolution used on the xCAT unit was 0.4-mm voxel with a field of view of 14 21 cm. The rotation duration of the scan was 57.60 mA. The applied tube voltage was 120 kVp. Total The duration of the radiologic examination was 11 minutes, including the time required to drape the patient with a sterile cover and place the gantry and patient’s head. The effective radiation dose applied ranged from 0.1 to 0.3 mSv. If the intraoperative radiologic examination showed unsatisfactory reduction, the shell was removed from patient’s head, enabling another reduction maneuver in a sterile setting. This process was repeated until complete satisfaction with the reduction had been achieved. To assess the accuracy of the reduction in critical cases, the CBCT scan was superimposed through the preoperative virtual plan using automatic alignment on iPlan-CMF software, version 3.7.0.64 (Brainlab, Munich, Germany). No
postoperative external fixation or bandage was applied. The preoperative multislice CT scans, intraoperative CBCT scans, and postoperative CBCT or multislice CT scans were loaded into the iPlan-CMF (Brainlab). The bony axial slices were aligned and the pre- and postoperative scans superimposed. The opposing nonfractured sides were segmented and mirrored on the midline axis, indicating the ideal position of the fractured zygomatic arch (Figs 4, 5).
STATISTICAL ANALYSIS
The data were summarized using descriptive statistics (mean standard deviation) and explored using visualization. The 2 target variables (remaining cortical step and remaining dislocation angle) were analyzed using robust multiple regression and an SMDM estimator algorithm.18 The use of intraoperative imaging (yes vs no) served as the primary predictor variable, and the control variables included fracture type (M-type or variable), gender, and age. Model assumptions were carefully investigated using diagnostic plots, and no severe violations against the relaxed model assumptions (SMDM estimator) were found. Co-linearity among the predictors was checked using variance inflation factors. Although some seemed to correlate slightly (eg, patients were, on average, slightly older in the intraoperative imaging group), no severe issues were detected because all variance inflation factors were less than 2. The significance level for the analyses was set to an a of 0.05, and all computations were performed with the statistical software R, version 3.5.2 (R Foundation, Vienna, Austria).19
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FIGURE 3. Photograph of patient undergoing intraoperative cone beam computed tomography scan with sterile cover (xCat; Xoran Technologies, Ann Arbor, MI).
FIGURE 4. Measurement of cortical step similar to scans shown in Figs 1 and 2.
Johner et al. Closed Reduction of Zygomatic Arch Fractures and CBCT. J Oral Maxillofac Surg 2019.
Johner et al. Closed Reduction of Zygomatic Arch Fractures and CBCT. J Oral Maxillofac Surg 2019.
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Table 1. NEED FOR REVISION SURGERY
Group Control (n = 18) Clinically satisfactory reduction at first attempt Second surgery Intraoperative imaging group (n = 27) Satisfactory reduction at first attempt Satisfactory reduction at second attempt Satisfactory reduction at third attempt Second surgery
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Patients (n)
15 1 18 6 2 0
Johner et al. Closed Reduction of Zygomatic Arch Fractures and CBCT. J Oral Maxillofac Surg 2019. FIGURE 5. Measurement of cortical step similar to scans shown in Figs 1 and 2. Johner et al. Closed Reduction of Zygomatic Arch Fractures and CBCT. J Oral Maxillofac Surg 2019.
Results The study included 45 patients (9 female [20%] and 36 male [80%] patients; age >16 years) who had undergone surgery for isolated zygomatic arch fractures from January 2008 to May 2018. A clear majority of males (80%) had presented with isolated zygomatic arch fractures. The left side (n = 26; 57.7%) was affected more often than was the right side (n = 19; 42.2%). The mean age in the intraoperative imaging and control groups was 53.1 and 33 years, respectively. From January 2008 to November 2015, the 18 patients in the control group had undergone closed reduction without intraoperative 3D-CBCT imaging guidance. They then underwent postoperative radiologic examinations with either CT or CBCT scans. From December 2015 to May 2018, 27 patients had undergone closed reduction with intraoperative 3D-CBCT imaging guidance, enabling intraoperative revision, as needed. Intraoperative revision was required in 8 of these 27 patients, which resulted in a second intraoperative CBCT scan. A second revision was necessary for only 2 patients. The maximum number of intraoperative CBCT scans performed for a single patient was 3. On average, 1.37 intraoperative radiographic CBCT scans were conducted per operation. One patient in the control group without intraoperative radiologic guidance had had unsatisfactory reduction found on the postoperative CBCT scan. Hence, revision surgery was indicated and was performed on the second day after the initial surgery. No case of failed reduction was found in the intraoperative CBCT group (1 vs 0; Table 1).
The reduction accuracy was greater in the intraoperative CBCT group than in the control group. The average remaining cortical step was 0.18 0.86 in the intraoperative CBCT group and 2.03 1.40 in the control group (P < .001; Fig 6, Table 2). The remaining dislocation angle results were better (ie, lower) in the intraoperative imaging group than in the control group (3.93 5.56 vs 7.75 8.07). However, the difference was not statistically significant (P = .58; Fig 7, Table 2). The use of intraoperative radiologic guidance appeared especially useful for variable type fractures, although the effect was less obvious for M-type fractures. The average operative time was 10.82 minutes in the control group and 27.11 minutes in the intraoperative imaging group, reflecting the added time required for the radiologic examination and surgical revision, if needed.
Discussion The aim of the present study was to evaluate the effect on reduction of the intraoperative use of 3D CBCT imaging compared with reduction using palpation only. We regarded the performance of second surgery as an indication of insufficient reduction. In the intraoperative CBCT group, no patient had required repeat surgery. In contrast, in the control group, 1 patient had undergone repeat surgery. To further evaluate the reduction accuracy, 2 radiologic measures were used as primary variables: the remaining cortical step and the angle of displacement after reduction. The remaining cortical step showed significantly better outcomes in the CBCT group than in the control group. However, the angle of displacement after reduction showed no significant differences between the CBCT and control groups. The benefit of intraoperative CBCT seemed greater for variable type fractures. For Mtype fractures, the folding effect would have favored adequate reduction in any case. These results are
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Table 2. RESULTS OF ROBUST MULTIPLE REGRESSION ANALYSIS
Variable Angular dislocation Constant Use of intraoperative imaging Variable fracture type Female gender Age Cortical step Constant Use of intraoperative imaging Variable fracture type Female gender Age
Adjusted R2
b
Standard P Error b Value
0.12 1.1 3.3
2.0 2.0
.18 .58 .11
2.6
1.7
.13
1.4 0.1
2.0 0.1
.49 .09
1.3 1.8
0.4 0.4
< .001 < .001
0.7
0.3
.03
0.3 0.0
0.4 0.0
.42 .42
0.47
Johner et al. Closed Reduction of Zygomatic Arch Fractures and CBCT. J Oral Maxillofac Surg 2019.
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FIGURE 6. Graph showing remaining highest cortical step after reduction for the 2 groups. Johner et al. Closed Reduction of Zygomatic Arch Fractures and CBCT. J Oral Maxillofac Surg 2019.
consistent with previous studies that compared reduction using intraoperative ultrasound imaging.17 Regarding the patient population, middle-age, male patients constituted the vast majority of patients with isolated zygomatic fractures (36 males vs 9 females). The fractures had occurred predominantly on the left side, an indication that this fracture might result mainly from acts of violence, because 90% of humans are right-handed.20 The mean age in the control group was distinctly younger than that in the intraoperative imaging group (33 vs 53.1 years). The older age in the intraoperative CBCT group might have been because of the improved outcomes in that group resulting in a more extended indication for surgical repositioning. The benefit of using intraoperative imaging is evident. Mobile fluoroscopy and C-arm image intensifiers have been described as valuable technical tools for direct intraoperative feedback on reduction by several investigators.12,21 The implementation of 3D radiologic imaging for intraoperative reduction is not yet widespread because of the associated high costs and radiation
exposure for the patient and surgical team. However, as reported by Gander et al,22 the use of intraoperative 3D radiologic imaging will be especially valuable in preventing the need for secondary surgery. Our results were also consistent with those of Buller et al,5,17 although they had used 2 different primary vari- Q4 ables. They reported a significant decrease for the persisting angle of displacement in isolated zygomatic arch fractures after reduction using intraoperative ultrasound guidance. They examined 16 patients who had undergone closed reduction of isolated zygomatic arch fractures using intraoperative ultrasound guidance compared with 60 control subjects who had been randomly selected. Although the difference in the remaining cortical step was not statistically significant between the 2 groups, the persisting angle of displacement after reduction showed a significant decrease in the ultrasound-guidance group. Pedemonte et al23 examined the requirement for repeat surgery in a group of 25 patients treated for M-type isolated zygomatic arch fractures by distance reduction using the Gillies’ approach and intraoperative radiographic guidance with C-arm fluoroscopy. The control group consisted of another 25 patients who had only undergone postoperative radiography, which showed inadequate reduction for several patients, who required repeat second surgery. However, the difference between the 2 groups was not statistically significant. Because the radiologic guidance was performed with the C-arm positioned at a 45 angle relative to the zygomatic arch on the fractured side,
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JOHNER ET AL
FIGURE 7. Graph showing remaining dislocation angle after reduction for the 2 groups. Johner et al. Closed Reduction of Zygomatic Arch Fractures and CBCT. J Oral Maxillofac Surg 2019.
the radiograph was 2 dimensional and could not detect the remaining dislocation angle in another plane. The postoperative radiographic examinations were performed with the same submental vortex projection; thus, they also lacked any additional information. The use of 3D radiographic imaging studies in either group might have aided in identifying the patients requiring revision. Other procedures such as endoscopy24 and ultrasonography25,26 do not use radiation. The endoscopic approach through a preauricular or temporal incision has the great advantage of a direct view of the fracture and its fragment, allowing for proper reduction and fixation, if needed. Czerwinski et al24 reported that the use of an endoscopic approach allowed for direct enhanced visualization with a minimal risk of damage to the frontal branch of the facial nerve or of temporal hollowing and, thus, represented a valid alternative to the coronal incision approach. Nonetheless, compared with closed reduction, these are invasive procedures associated with a greater risk of lesions to the facial nerve, infection, and scar formation. Isolated zygomatic arch fractures are simple fractures, and patients’ and surgeons’ expectations toward the outcomes after intervention are high. Apart from
impaired functionality, esthetic factors account for the main indications for surgical treatment. Mirroring the opposing, nonfractured side might result in total facial symmetry, which is unlikely. Hence, measuring the remaining cortical step and dislocation angle of the achieved reduction to the ideal position will result in a measurement error. We assumed that the greater the dislocation of the fracture, the more evident would be the effects on impaired functionality and facial symmetry and vice versa for the smaller the dislocation. Thus, the more accurate the reduction, the fewer restrictions that would remain on functionality and esthetic appearance. However, this holds true only for limited dislocations. At some point, the remaining fracture dislocation will not automatically result in noticeable impaired functionality and facial asymmetry. Additionally, a psychological effect could occur by providing positive stimuli for a surgeon to achieve greater accuracy in the reduction and best possible outcomes from the immediate feedback. However, supreme reduction results might be achieved but have no recognizable effect on functionality and facial symmetry. Nonetheless, we believe in the benefit of constant training for optimal results to achieve a good level of expertise for those patients requiring these skills. As a retrospective study, our investigation was exposed to the hazard of selection bias. This issue was addressed by including all patients with isolated zygomatic arch fractures who had undergone surgery at our clinic within the study period and only limited by the inclusion and exclusion criteria. Although the benefits of intraoperative radiographic guidance are obvious, the radiation exposure remains a major drawback and must be addressed. In the present study, the personnel within the surgical theater were limited to the surgeon and anesthetist for the duration of the radiologic examination. Furthermore, all personnel remaining in the surgical theater, including the patient, wore or were covered by a lead apron with a lead equivalent greater than 0.25 mm. Because the radiation exposure declines rapidly with the increasing distance from the source, according to the inverse square law, the radiation exposure to the remaining personnel was negligible.27 Intraoperative CBCT scans also have the advantage of lower radiation than that with multislice CT scans. Brisco et al28 showed a significantly lower radiation dose for CBCT than for multislice CT, with a mean dose of 13 mGy versus 22 mGy, respectively. The same findings were observed for the effective dose (CBCT, 496 mSV; multislice CT, 871 mSV).28,29 Because the use of intraoperative CBCT scans will render any postoperative radiologic examination unnecessary, postoperative radiation exposure will not
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occur, and forgoing its use will be more cost-effective. The cost of an intraoperative radiologic examination in the flat-rate diagnosis related group has been estimated at US$200. In contrast, the cost for a postoperative CT scan has been estimated at US$500. By preventing the need for secondary surgical interventions using intraoperative radiologic examination of the reduction, the costs can be reduced. In addition, intraoperative radiologic examination enables the surgeon to immediately perform another reduction attempt within the first surgery.23 These cost savings must be set against the prolonged surgery time, because the time in the operating theater is very costly. In our study, average operative time was 27.11 minutes for the CBCT group and 10.82 minutes in the control group. We believe the longer operative time in the CBCT group had resulted from the use of intraoperative CBCT and any repeated reduction attempts. At our hospital, 1 hour in the operating room costs $1400. However, it is likely that the cost savings realized by omitting the postoperative radiologic examinations and the prevention of revision surgery will outweigh the costs resulting from the longer operative time. To the best of our knowledge, the present study is the first to measure the reduction accuracy using intraoperative 3D imaging studies and to assess the quality standards in the closed reduction of isolated zygomatic arch fractures. Arguments against the use of intraoperative imaging or imaging in general for closed reduction of zygomatic arch fractures might be the greater importance of the clinical outcome compared with the radiologic outcome. Nevertheless, as shown in our study, the high accuracy in fracture reduction and the steep learning curve in an academic university hospital were of greater importance to us. In conclusion, intraoperative 3D imaging using CBCT, combined with the possibility of superimposing intraoperatively acquired images with one representing a mirrored ideal fracture position, significantly increased the accuracy of reduction for isolated zygomatic arch fractures and rendered any secondary surgical interventions obsolete. Regarding multifragmented fractures, intraoperative 3D imaging of displaced fractures would seem to be especially valuable for providing viable feedback to the surgeon. Concerns regarding radiation exposure and elevated costs must be weighed against the benefits resulting from the reduction of postoperative radiologic examinations and second surgeries. The supremacy of 3D imaging techniques compared with 2D imaging techniques, such as ultrasonography, is evident. Nonetheless, the increase in accuracy must justify the additional radiation exposure. A classification system that could represent the remaining dislocation angle in 3 dimensions is desirable and more research is required.
References 1. Ungari C, Filiaci F, Riccardi E, et al: Etiology and incidence of zygomatic fracture: A retrospective study related to a series of 642 patients. Eur Rev Med Pharmacol Sci 16:1559, 2012 2. Honig JF, Merten HA: Classification system and treatment of zygomatic arch fractures in the clinical setting. J Craniofac Surg 15:986, 2004 3. Ozyazgan I, G€ unay GK, Eskitas¸c¸ioglu T, et al: A new proposal of classification of zygomatic arch fractures. J Oral Maxillofac Surg 65:462, 2007 4. Yamamoto K, Murakami K, Sugiara T, et al: Clinical analysis of isolated zygomatic arch fractures. J Oral Maxillofac Surg 65: 457, 2007 5. Buller J, Zirk E, Kreppel M, et al: Radiomorphometric analysis of isolated zygomatic arch fractures: A comparison of classifications and reduction outcomes. J Craniomaxillofac Surg 46: 1252, 2018 6. Gillies H, Kilner T, Stone D: Fractures of the malar-zygomatic compound: With a description of a new X-ray position. Br J Surg 14:651, 1927 7. Keen W: Surgery: Its Principles and Practice. Philadelphia, PA, WB Saunders, 1909 8. Hindin DI, Muetterties CE, Mehta C, et al: Treatment of isolated zygomatic arch fracture: Improved outcomes with external splinting. Plast Reconstr Surg 139:1162e, 2017 9. Quinn JH: Lateral coronoid approach for intraoral reduction of fractures of the zygomatic arch. J Oral Surg 35:321, 1977 10. Giudice A, Colangeli W, Cristofaro MG: Percutaneous reduction of an isolated zygomatic fracture using a wire suture. Br J Oral Maxillofac Surg 51:e201, 2013 11. Kim JS, Park YJ, Lee YJ, et al: Reduction of zygomatic arch isolated fracture using ultra sound and needle marking. Arch Craniofac Surg 17:198, 2016 12. Ramanoojam S, Gadre P, Shah S, Gadre KS: Assessment of the adequacy of closed reduction in fractures of the zygomatic arch using "C"-arm image intensifier. J Craniofac Surg 22:1383, 2011 13. Nezafati S, Javadrashid R, Rad S, Akrami S: Comparison of ultrasonography with submentovertex films and computed tomography scan in the diagnosis of zygomatic arch fractures. Dentomaxillofac Radiol 39:11, 2010 14. Ellis E III, Perez D: An algorithm for the treatment of isolated zygomatico-orbital fractures. J Oral Maxillofac Surg 72:1975, 2014 15. STROBE Statement. Checklist Cohort Studies; 2007. Available at: https://www.strobe-statement.org/index.php?id=availablechecklists. Accessed --Q5 16. Dodson TB: Writing a scientific paper is not rocket science!. J Oral Maxillofac Surg 73(suppl):S160, 2015 17. Buller J, et al: Intraoperative ultrasound control of zygomatic arch fractures: Does additional imaging improve reduction quality? J Oral Maxillofac Surg 77:769, 2019 18. Maechler M, Rousseeuw P, Croux C, et al: Robustbase: Basic robust statistics R version 0.93-5, 2019. Available at: http:// CRAN.R-project.org/package=robustbase. Accessed --19. R Core Team. R: A language and environment for statistical computing. Vienna, Austria, R Foundation for Statistical Computing, 2018 20. Raymond M, Pontier D: Is there geographical variation in human handedness? Laterality 9:35, 2004 21. Menon A, Karikal A, Shetty V: Does C-arm guidance improve reduction of zygomatic arch fractures?—A randomized controlled trial. J Oral Maxillofac Surg 76:2376, 2018 22. Gander T, Blumer M, Rostetter C, et al: Intraoperative 3dimensional cone beam computed tomographic imaging during reconstruction of the zygoma and orbit. Oral Surg Oral Med Oral Pathol Oral Radiol 126:192, 2018 23. Pedemonte C, Saez F, Vargas I, et al: C-arm as intraoperative control in reduction of isolated zygomatic arch fractures: A randomized clinical trial. Oral Maxillofac Surg 20:79, 2016 24. Czerwinski M, Lee C: The rationale and technique of endoscopic approach to the zygomatic arch in facial trauma. Facial Plast Surg Clin North Am 14:37, 2006
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25. Gulicher D, Krimmel M, Reinert S: The role of intraoperative ultrasonography in zygomatic complex fracture repair. Int J Oral Maxillofac Surg 35:224, 2006 26. Kiwanuka E, Smith SE, Frates MC, Caterson EJ: Use of highfrequency ultrasound guidance for intraoperative zygomatic arch fracture reduction. J Craniofac Surg 24:2036, 2013 27. Sinha S, Evans SJ, Arundell MK, Burke FD: Radiation protection issues with the use of mini C-arm image intensifiers in surgery in the upper limb: Optimisation of practice and
the impact of new regulations. J Bone Joint Surg Br 86: 333, 2004 28. Brisco J, Fuller K, Lee N, Andrew D: Cone beam computed tomography for imaging orbital trauma—Image quality and radiation dose compared with conventional multislice computed tomography. Br J Oral Maxillofac Surg 52:76, 2014 29. Stratis A, Zhang G, Lopez-Rendon X, et al: Two examples of indication specific radiation dose calculations in dental CBCT and multidetector CT scanners. Phys Med 41:71, 2017
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Improved Results in Closed Reduction of Zygomatic Arch Fractures by the Use of Intraoperative Cone Beam Computed Tomography Imaging Jean-Pierre Johner, MD, DMD,* Daniel Wiedemeier, PhD,y Lukas Hingsammer, MD, DMD,z Thomas Gander, PhD, MD, DMD,x Michael Blumer, MD, DMD,{ and Maximilian E. H. Wagner, MD, DMDk
Q7
Purpose:
The use of intraoperative imaging could help overcome the insufficiency of closed reduction that can result from the absence of visible feedback to evaluate the accuracy of the reduction in isolated zygomatic arch fractures. The aim of the present study was to evaluate the use of intraoperative 3-dimensinoal cone-beam computed tomography (CBCT) to improve the accuracy of reduction, by measuring the remaining cortical step and dislocation angle. We also evaluated the effect of CBCT on the need for repeat surgery.
Patients and Methods: We performed a retrospective cohort study of patients who had undergone zygomatic arch reduction surgery from January 2008 to May 2018. The patients were grouped according to the predictor variables into group A (postoperative radiologic follow-up studies) and group B (intraoperative CBCT imaging studies). The primary outcome variables were the remaining cortical step and dislocation angle compared with the ideal virtually mirrored position. These were assessed as measures of reduction accuracy. The secondary variables included age, gender, surgery duration, and fracture type. Statistical analysis was performed using a robust multiple regression analysis. Results:
The 45 patients were divided into 2 subgroups with 18 patients in the no intraoperative imaging (control) group and 27 patients in the intraoperative imaging group. Insufficient reduction occurred in 1 patient in the group without intraoperative imaging, leading to repeat surgery. No repeat surgery was necessary in the intraoperative imaging group. The remaining cortical step of the intraoperative imaging group was significantly lower than that of the control group (0.18 vs 2.03 mm; P < .001). For the remaining dislocation angle, similar findings were observed but without statistical significance (3.93 vs 7.75 ; P = .58). Conclusions: The use of intraoperative CBCT significantly increased the accuracy of the reduction. Furthermore, the need for repeat surgery was not required for any patient in the intraoperative imaging group with CBCT-guided reduction. Ó 2019 American Association of Oral and Maxillofacial Surgeons J Oral Maxillofac Surg -:1.e1-1.e9, 2019 *Resident, Department of Craniomaxillofacial Surgery, University
Conflict of Interest Disclosures: None of the authors have any relevant financial relationship(s) with a commercial interest.
Hospital Z€ urich, Z€ urich, Switzerland. yResearch Associate, Division of Data Analysis and Statistics,
Address correspondence and reprint requests to Dr Johner:
Department of Statistical Services, University Z€ urich, Z€ urich,
Klinik und Poliklinik f€ ur Mund-, Kiefer-, und Gesichtschirurgie
Switzerland.
Universit€atsSpital Z€ urich, Frauenklinikstrasse 24, Z€ urich, 8091
zResident, Department of Craniomaxillofacial Surgery, University
Switzerland; e-mail: [email protected]
Hospital Z€ urich, Z€ urich, Switzerland. xSenior Physician, Department of Craniomaxillofacial Surgery,
Received May 29 2019 Accepted October 28 2019
University Hospital Z€ urich, Z€ urich, Switzerland.
Ó 2019 American Association of Oral and Maxillofacial Surgeons
{Attending
Physician,
Department
of
Craniomaxillofacial
0278-2391/19/31253-4
Surgery, University Hospital Z€ urich, Z€ urich, Switzerland. kAttending
Physician,
Department
of
https://doi.org/10.1016/j.joms.2019.10.025
Craniomaxillofacial
Surgery, University Hospital Z€ urich, Z€ urich, Switzerland.
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CLOSED REDUCTION OF ZYGOMATIC ARCH FRACTURES AND CBCT
Zygomatic arch fractures will mostly occur as a part of a tripod fracture. Isolated zygomatic arch fractures will account for up to 14% of all zygomatic fractures.1 The indication for surgical treatment will be conclusively justified by the clinical symptoms, including an esthetic facet due to midface asymmetry, which will result in a depressed lateral cheek, and a functional facet due to the masticatory impairment resulting from interference of the dislocated zygomatic arch fragment and condyle. Left untreated, this can result in impaired mouth opening, temporomandibular joint ankylosis, and a depressed, asymmetric cheek. Different classifications have been established by Honig and Merten,2 Ozyazgan et al,3 and Yamamoto et al.4 The typical M- or V-type fractures, classified as Yamamoto type II, Honig and Merten type I, and Ozyazgan type IBV have been reported to have favorable reduction outcomes.5 The original approach for closed reduction of the zygomatic arch fracture through a temporal incision was first described by Gillies et al6 in 1927 and remains widely used today.1,7 Other approaches have included an intraoral incision, a direct cutaneous or transbuccal approach, and a bicoronal approach.8 The indication for open reduction and internal fixation has remained restricted to multifragmented and unstable fractures. Various devices, such as the elevator, Stromeyer hook, curved mosquito forceps, Rowe zygoma elevator, Deschamps needle holder, Foley balloon catheter, and Langenbeck retractor, have been described for reduction of the zygomatic arch.9 To immobilize the bone fragments after reduction, aqua splints and percutaneous wire suture techniques have been used.10,11 Short incision approaches such as the Gillies, direct cutaneous, or intraoral incision approaches, have been commonly used owing to their benefit in minimizing scarring. However, they have the limitations of a blind surgical approach. Surgeons facing the difficulty of reducing the fracture without visualization of the fracture lines have sought for reduction feedback using digital palpation, crepitation sounds, and visible control of symmetry. However, because of the soft tissue swelling that occurs after trauma, these factors have been less reliable.12 The efficacy of reduction could be increased by ultrasound guidance, which has been proved to be accurate in assessing fractured arches, with a sensitivity of 88.2% and specificity of 100%.13 Kim et al11 supplemented the ultrasound procedure with the use of needles as reference points and localization assistance. With the limited use of ultrasound devices for maxillofacial trauma and the complicated operation room setup, few clinics have used such devices. With the increasing availability of 3-dimensional (3D) imaging devices with costs comparable to those for ultrasound
devices, the use of ultrasound devices has remained limited to several clinical centers. In addition, intraoperative 3D imaging has expanded the indications for closed repair by confirming the accuracy of reduction without the need for direct visualization.14 The aim of the present study was to compare closed reduction for isolated zygomatic fractures with and without the use of intraoperative cone-beam computed tomography (CBCT) imaging. We hypothesized that intraoperative CBCT imaging during closed reduction of isolated zygomatic fractures would provide valuable information to surgeons, because the immediate feedback would enable corrective secondary reduction attempts within the first surgery, leading to better results and fewer repeat surgeries. The purpose of the present study was to quantify the effect of intraoperative CBCT imaging by evaluating 2 radiologic measurements: the remaining cortical step and the remaining dislocation angle after closed reduction. Furthermore, we assessed secondary variables such as operation duration, age, gender, and fracture side and type.
Patients and Methods STUDY DESIGN
To address the research purpose, we designed and implemented a retrospective cohort study in accordance with the STROBE (strengthening the reporting of observational studies in epidemiology) guidelines15 and recommendations by Dodson16 on scientific writing. The study population included all patients who had presented to the University Hospital of Z€ urich for the evaluation and management of isolated zygomatic arch fractures from January 2008 to May 2018. All patients included in the present study had provided written informed consent. The ethics committee of the University Hospital of Z€ urich evaluated and approved the study protocol (approval ID, 2018-01166). VARIABLES
The predictor variable was defined by the use of intraoperative 3D CBCT imaging versus none. The implementation of intraoperative 3D CBCT imaging at our clinic occurred in December 2015 and was standard during trauma surgery. The assessed primary variables were 2 radiologic measurements used to quantify the accuracy of the reduction. First, the maximum discrepancy from the ideal position (ie, the remaining cortical step after reduction) in the zygomatic arch after reduction, was measured as the distance in millimeters (Figs 1, 2). Second, similar to the method used by Buller et al,17 the dislocation angle, formed by the secant of the outer cortical shape of the zygoma,
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older than 16 years; 2) closed reduction of unilateral or bilateral isolated zygomatic arch fractures; and 3) treatment period from January 2008 to May 2018. The patients meeting the following criteria were excluded from the study sample: 1) written informed consent not provided; 2) permission not provided for use of patient data; and 3) clinical or radiologic data missing. Patients with dislocated zygomatic arch fractures who had provided written informed consent and had met the inclusion criteria were included in the present study. SURGICAL PROCEDURE
FIGURE 1. Preoperative axial view of computed tomography scan with segmentation of the unaffected side (yellow) and mirrored ideal position of the zygomatic arch (purple) using iPlan (Brainlab). Johner et al. Closed Reduction of Zygomatic Arch Fractures and CBCT. J Oral Maxillofac Surg 2019.
zygomatic arch, and the most dislocated fragment axis, was measured. The secondary variables assessed including the operative time, patient age and gender, fracture side, and association between fracture type (variable vs M type) and the reduction accuracy. The need for revision surgery was regarded as evidence of reduction failure, as captured by the primary variables. DATA COLLECTION METHOD
To be included in the study sample, the patients had to have met the following inclusion criteria: 1) age
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FIGURE 2. Postoperative axial view of computed tomography scan with segmentation of the unaffected side (yellow) and mirrored ideal position of the zygomatic arch (purple) using iPlan (Brainlab). Johner et al. Closed Reduction of Zygomatic Arch Fractures and CBCT. J Oral Maxillofac Surg 2019.
The preoperative measures included CT scans of the viscerocranium to confirm the dislocated zygomatic arch fracture and, as needed, CT scans of the neurocranium to exclude intracerebral lesions. Other measures included blood examinations to exclude coagulation disorders and a thorough anesthetic examination to ensure a minimal risk of undergoing general anesthesia, as needed. The surgical procedure was performed by different surgeons with the experience of a senior attending within the oral and maxillofacial surgery department of the University Hospital of Z€ urich. The surgery was performed within 0 to 14 days after initial trauma. All patients were given preoperative prophylactic antibiotic treatment and disinfection with a povidone–iodine scrub. The chosen surgical approach was either an extraoral transbuccal stab incision or an intraoral incision in the vestibular fold of the maxilla. Reduction was performed using a Stromeyer hook in the extraoral transbuccal approach and either a Stromeyer hook or elevator for an intraoral approach. The choice of the surgical approach and the reduction instrument used was left to the surgeon’s discretion. For those patients who had undergone closed reduction from January 2008 to November 2015, the postoperative follow-up protocol included radiologic examination using CBCT or CT scanning. Any postoperative radiologic follow-up examination performed using 2-dimensional (2D) radiographs (eg, submentovertex projection) was excluded. From December 2015 onward, intraoperative reduction guidance was conducted using 3D intraoperative scanning with a mobile xCAT unit (Xoran Technologies, Ann Arbor, MI). The patients were positioned on an x-ray table. For the duration of the radiologic examination, the personnel within the operation room were limited to the patient, 1 anesthesiologist, and the surgeon. All the persons remaining in the operation room, including the patient, wore lead shielding for the duration of the radiologic examination. The patient was covered with a sterile cover during the radiologic examination, and the correct positioning of the
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patient’s head within the gantry was confirmed by the built-in laser pointer (Fig 3). The resolution used on the xCAT unit was 0.4-mm voxel with a field of view of 14 21 cm. The rotation duration of the scan was 57.60 mA. The applied tube voltage was 120 kVp. Total The duration of the radiologic examination was 11 minutes, including the time required to drape the patient with a sterile cover and place the gantry and patient’s head. The effective radiation dose applied ranged from 0.1 to 0.3 mSv. If the intraoperative radiologic examination showed unsatisfactory reduction, the shell was removed from patient’s head, enabling another reduction maneuver in a sterile setting. This process was repeated until complete satisfaction with the reduction had been achieved. To assess the accuracy of the reduction in critical cases, the CBCT scan was superimposed through the preoperative virtual plan using automatic alignment on iPlan-CMF software, version 3.7.0.64 (Brainlab, Munich, Germany). No
postoperative external fixation or bandage was applied. The preoperative multislice CT scans, intraoperative CBCT scans, and postoperative CBCT or multislice CT scans were loaded into the iPlan-CMF (Brainlab). The bony axial slices were aligned and the pre- and postoperative scans superimposed. The opposing nonfractured sides were segmented and mirrored on the midline axis, indicating the ideal position of the fractured zygomatic arch (Figs 4, 5).
STATISTICAL ANALYSIS
The data were summarized using descriptive statistics (mean standard deviation) and explored using visualization. The 2 target variables (remaining cortical step and remaining dislocation angle) were analyzed using robust multiple regression and an SMDM estimator algorithm.18 The use of intraoperative imaging (yes vs no) served as the primary predictor variable, and the control variables included fracture type (M-type or variable), gender, and age. Model assumptions were carefully investigated using diagnostic plots, and no severe violations against the relaxed model assumptions (SMDM estimator) were found. Co-linearity among the predictors was checked using variance inflation factors. Although some seemed to correlate slightly (eg, patients were, on average, slightly older in the intraoperative imaging group), no severe issues were detected because all variance inflation factors were less than 2. The significance level for the analyses was set to an a of 0.05, and all computations were performed with the statistical software R, version 3.5.2 (R Foundation, Vienna, Austria).19
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FIGURE 3. Photograph of patient undergoing intraoperative cone beam computed tomography scan with sterile cover (xCat; Xoran Technologies, Ann Arbor, MI).
FIGURE 4. Measurement of cortical step similar to scans shown in Figs 1 and 2.
Johner et al. Closed Reduction of Zygomatic Arch Fractures and CBCT. J Oral Maxillofac Surg 2019.
Johner et al. Closed Reduction of Zygomatic Arch Fractures and CBCT. J Oral Maxillofac Surg 2019.
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Table 1. NEED FOR REVISION SURGERY
Group Control (n = 18) Clinically satisfactory reduction at first attempt Second surgery Intraoperative imaging group (n = 27) Satisfactory reduction at first attempt Satisfactory reduction at second attempt Satisfactory reduction at third attempt Second surgery
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Q6
Patients (n)
15 1 18 6 2 0
Johner et al. Closed Reduction of Zygomatic Arch Fractures and CBCT. J Oral Maxillofac Surg 2019. FIGURE 5. Measurement of cortical step similar to scans shown in Figs 1 and 2. Johner et al. Closed Reduction of Zygomatic Arch Fractures and CBCT. J Oral Maxillofac Surg 2019.
Results The study included 45 patients (9 female [20%] and 36 male [80%] patients; age >16 years) who had undergone surgery for isolated zygomatic arch fractures from January 2008 to May 2018. A clear majority of males (80%) had presented with isolated zygomatic arch fractures. The left side (n = 26; 57.7%) was affected more often than was the right side (n = 19; 42.2%). The mean age in the intraoperative imaging and control groups was 53.1 and 33 years, respectively. From January 2008 to November 2015, the 18 patients in the control group had undergone closed reduction without intraoperative 3D-CBCT imaging guidance. They then underwent postoperative radiologic examinations with either CT or CBCT scans. From December 2015 to May 2018, 27 patients had undergone closed reduction with intraoperative 3D-CBCT imaging guidance, enabling intraoperative revision, as needed. Intraoperative revision was required in 8 of these 27 patients, which resulted in a second intraoperative CBCT scan. A second revision was necessary for only 2 patients. The maximum number of intraoperative CBCT scans performed for a single patient was 3. On average, 1.37 intraoperative radiographic CBCT scans were conducted per operation. One patient in the control group without intraoperative radiologic guidance had had unsatisfactory reduction found on the postoperative CBCT scan. Hence, revision surgery was indicated and was performed on the second day after the initial surgery. No case of failed reduction was found in the intraoperative CBCT group (1 vs 0; Table 1).
The reduction accuracy was greater in the intraoperative CBCT group than in the control group. The average remaining cortical step was 0.18 0.86 in the intraoperative CBCT group and 2.03 1.40 in the control group (P < .001; Fig 6, Table 2). The remaining dislocation angle results were better (ie, lower) in the intraoperative imaging group than in the control group (3.93 5.56 vs 7.75 8.07). However, the difference was not statistically significant (P = .58; Fig 7, Table 2). The use of intraoperative radiologic guidance appeared especially useful for variable type fractures, although the effect was less obvious for M-type fractures. The average operative time was 10.82 minutes in the control group and 27.11 minutes in the intraoperative imaging group, reflecting the added time required for the radiologic examination and surgical revision, if needed.
Discussion The aim of the present study was to evaluate the effect on reduction of the intraoperative use of 3D CBCT imaging compared with reduction using palpation only. We regarded the performance of second surgery as an indication of insufficient reduction. In the intraoperative CBCT group, no patient had required repeat surgery. In contrast, in the control group, 1 patient had undergone repeat surgery. To further evaluate the reduction accuracy, 2 radiologic measures were used as primary variables: the remaining cortical step and the angle of displacement after reduction. The remaining cortical step showed significantly better outcomes in the CBCT group than in the control group. However, the angle of displacement after reduction showed no significant differences between the CBCT and control groups. The benefit of intraoperative CBCT seemed greater for variable type fractures. For Mtype fractures, the folding effect would have favored adequate reduction in any case. These results are
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Table 2. RESULTS OF ROBUST MULTIPLE REGRESSION ANALYSIS
Variable Angular dislocation Constant Use of intraoperative imaging Variable fracture type Female gender Age Cortical step Constant Use of intraoperative imaging Variable fracture type Female gender Age
Adjusted R2
b
Standard P Error b Value
0.12 1.1 3.3
2.0 2.0
.18 .58 .11
2.6
1.7
.13
1.4 0.1
2.0 0.1
.49 .09
1.3 1.8
0.4 0.4
< .001 < .001
0.7
0.3
.03
0.3 0.0
0.4 0.0
.42 .42
0.47
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FIGURE 6. Graph showing remaining highest cortical step after reduction for the 2 groups. Johner et al. Closed Reduction of Zygomatic Arch Fractures and CBCT. J Oral Maxillofac Surg 2019.
consistent with previous studies that compared reduction using intraoperative ultrasound imaging.17 Regarding the patient population, middle-age, male patients constituted the vast majority of patients with isolated zygomatic fractures (36 males vs 9 females). The fractures had occurred predominantly on the left side, an indication that this fracture might result mainly from acts of violence, because 90% of humans are right-handed.20 The mean age in the control group was distinctly younger than that in the intraoperative imaging group (33 vs 53.1 years). The older age in the intraoperative CBCT group might have been because of the improved outcomes in that group resulting in a more extended indication for surgical repositioning. The benefit of using intraoperative imaging is evident. Mobile fluoroscopy and C-arm image intensifiers have been described as valuable technical tools for direct intraoperative feedback on reduction by several investigators.12,21 The implementation of 3D radiologic imaging for intraoperative reduction is not yet widespread because of the associated high costs and radiation
exposure for the patient and surgical team. However, as reported by Gander et al,22 the use of intraoperative 3D radiologic imaging will be especially valuable in preventing the need for secondary surgery. Our results were also consistent with those of Buller et al,5,17 although they had used 2 different primary vari- Q4 ables. They reported a significant decrease for the persisting angle of displacement in isolated zygomatic arch fractures after reduction using intraoperative ultrasound guidance. They examined 16 patients who had undergone closed reduction of isolated zygomatic arch fractures using intraoperative ultrasound guidance compared with 60 control subjects who had been randomly selected. Although the difference in the remaining cortical step was not statistically significant between the 2 groups, the persisting angle of displacement after reduction showed a significant decrease in the ultrasound-guidance group. Pedemonte et al23 examined the requirement for repeat surgery in a group of 25 patients treated for M-type isolated zygomatic arch fractures by distance reduction using the Gillies’ approach and intraoperative radiographic guidance with C-arm fluoroscopy. The control group consisted of another 25 patients who had only undergone postoperative radiography, which showed inadequate reduction for several patients, who required repeat second surgery. However, the difference between the 2 groups was not statistically significant. Because the radiologic guidance was performed with the C-arm positioned at a 45 angle relative to the zygomatic arch on the fractured side,
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FIGURE 7. Graph showing remaining dislocation angle after reduction for the 2 groups. Johner et al. Closed Reduction of Zygomatic Arch Fractures and CBCT. J Oral Maxillofac Surg 2019.
the radiograph was 2 dimensional and could not detect the remaining dislocation angle in another plane. The postoperative radiographic examinations were performed with the same submental vortex projection; thus, they also lacked any additional information. The use of 3D radiographic imaging studies in either group might have aided in identifying the patients requiring revision. Other procedures such as endoscopy24 and ultrasonography25,26 do not use radiation. The endoscopic approach through a preauricular or temporal incision has the great advantage of a direct view of the fracture and its fragment, allowing for proper reduction and fixation, if needed. Czerwinski et al24 reported that the use of an endoscopic approach allowed for direct enhanced visualization with a minimal risk of damage to the frontal branch of the facial nerve or of temporal hollowing and, thus, represented a valid alternative to the coronal incision approach. Nonetheless, compared with closed reduction, these are invasive procedures associated with a greater risk of lesions to the facial nerve, infection, and scar formation. Isolated zygomatic arch fractures are simple fractures, and patients’ and surgeons’ expectations toward the outcomes after intervention are high. Apart from
impaired functionality, esthetic factors account for the main indications for surgical treatment. Mirroring the opposing, nonfractured side might result in total facial symmetry, which is unlikely. Hence, measuring the remaining cortical step and dislocation angle of the achieved reduction to the ideal position will result in a measurement error. We assumed that the greater the dislocation of the fracture, the more evident would be the effects on impaired functionality and facial symmetry and vice versa for the smaller the dislocation. Thus, the more accurate the reduction, the fewer restrictions that would remain on functionality and esthetic appearance. However, this holds true only for limited dislocations. At some point, the remaining fracture dislocation will not automatically result in noticeable impaired functionality and facial asymmetry. Additionally, a psychological effect could occur by providing positive stimuli for a surgeon to achieve greater accuracy in the reduction and best possible outcomes from the immediate feedback. However, supreme reduction results might be achieved but have no recognizable effect on functionality and facial symmetry. Nonetheless, we believe in the benefit of constant training for optimal results to achieve a good level of expertise for those patients requiring these skills. As a retrospective study, our investigation was exposed to the hazard of selection bias. This issue was addressed by including all patients with isolated zygomatic arch fractures who had undergone surgery at our clinic within the study period and only limited by the inclusion and exclusion criteria. Although the benefits of intraoperative radiographic guidance are obvious, the radiation exposure remains a major drawback and must be addressed. In the present study, the personnel within the surgical theater were limited to the surgeon and anesthetist for the duration of the radiologic examination. Furthermore, all personnel remaining in the surgical theater, including the patient, wore or were covered by a lead apron with a lead equivalent greater than 0.25 mm. Because the radiation exposure declines rapidly with the increasing distance from the source, according to the inverse square law, the radiation exposure to the remaining personnel was negligible.27 Intraoperative CBCT scans also have the advantage of lower radiation than that with multislice CT scans. Brisco et al28 showed a significantly lower radiation dose for CBCT than for multislice CT, with a mean dose of 13 mGy versus 22 mGy, respectively. The same findings were observed for the effective dose (CBCT, 496 mSV; multislice CT, 871 mSV).28,29 Because the use of intraoperative CBCT scans will render any postoperative radiologic examination unnecessary, postoperative radiation exposure will not
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occur, and forgoing its use will be more cost-effective. The cost of an intraoperative radiologic examination in the flat-rate diagnosis related group has been estimated at US$200. In contrast, the cost for a postoperative CT scan has been estimated at US$500. By preventing the need for secondary surgical interventions using intraoperative radiologic examination of the reduction, the costs can be reduced. In addition, intraoperative radiologic examination enables the surgeon to immediately perform another reduction attempt within the first surgery.23 These cost savings must be set against the prolonged surgery time, because the time in the operating theater is very costly. In our study, average operative time was 27.11 minutes for the CBCT group and 10.82 minutes in the control group. We believe the longer operative time in the CBCT group had resulted from the use of intraoperative CBCT and any repeated reduction attempts. At our hospital, 1 hour in the operating room costs $1400. However, it is likely that the cost savings realized by omitting the postoperative radiologic examinations and the prevention of revision surgery will outweigh the costs resulting from the longer operative time. To the best of our knowledge, the present study is the first to measure the reduction accuracy using intraoperative 3D imaging studies and to assess the quality standards in the closed reduction of isolated zygomatic arch fractures. Arguments against the use of intraoperative imaging or imaging in general for closed reduction of zygomatic arch fractures might be the greater importance of the clinical outcome compared with the radiologic outcome. Nevertheless, as shown in our study, the high accuracy in fracture reduction and the steep learning curve in an academic university hospital were of greater importance to us. In conclusion, intraoperative 3D imaging using CBCT, combined with the possibility of superimposing intraoperatively acquired images with one representing a mirrored ideal fracture position, significantly increased the accuracy of reduction for isolated zygomatic arch fractures and rendered any secondary surgical interventions obsolete. Regarding multifragmented fractures, intraoperative 3D imaging of displaced fractures would seem to be especially valuable for providing viable feedback to the surgeon. Concerns regarding radiation exposure and elevated costs must be weighed against the benefits resulting from the reduction of postoperative radiologic examinations and second surgeries. The supremacy of 3D imaging techniques compared with 2D imaging techniques, such as ultrasonography, is evident. Nonetheless, the increase in accuracy must justify the additional radiation exposure. A classification system that could represent the remaining dislocation angle in 3 dimensions is desirable and more research is required.
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