- Email: [email protected]
Orbital Volume Correction in Orbital Floor Fractures: A Comparison of Transorbital and Transantral Techniques
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CRANIOMAXILLOFACIAL TRAUMA
Orbital Volume Correction in Orbital Floor Fractures: A Comparison of Transorbital and Transantral Techniques
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Peter Dennis, DMD, MD,* Akshay Govind, DDS, MD, MHI,y Shaban Demirel, OD, PhD,z and Melissa Amundson, DDSx
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Purpose:
We compared the accuracy of orbital volume correction between the transorbital and transantral reconstructive techniques.
Materials and Methods:
A retrospective cohort study was performed of patients who had undergone repair of isolated, unilateral orbital floor blowout fractures at Legacy Emanuel Hospital from 2013 to 2018. A total of 21 patients were identified and included in the predictor variable cohorts of the transorbital versus transantral repair technique. The outcome variable of orbital volume correction was evaluated by comparing the volume of the postoperative repaired orbits with that of the contralateral noninjured orbits. Additional ordinal variables analyzed included the preoperative orbital defect size and analysis of the transantral cohort stratified by the plating technique used. Data were assessed using analysis of variance and paired t tests.
Results:
A transantral approach was used for orbital repair in 9 patients. In these patients, the postoperative orbital volume in the injured orbit was 2.69% greater than that in the uninjured orbit. The 12 patients who had undergone transantral repair had a postoperative orbital volume in the injured orbit that was 0.56% smaller than that of the uninjured orbit (P = .033). Division of the transantral cohort into 2 different plating techniques identified a less than 1% difference in mean orbital volume correction between the 2 techniques (P = .104). The average defect volume before transorbital repair was 4.87 cm3 compared with 5.22 cm3 for transantral repair (P = .907). Conclusions: The results from the present study have shown that the accuracy of orbital volume correction using the transantral approach will be comparable to that of the transorbital approach, as shown by a small, but statistically significant, increased accuracy in the volume correction with the transantral approach. Additional investigation to establish clinical correlations with these findings should be conducted. Ó 2019 Published by Elsevier Inc. on behalf of the American Association of Oral and Maxillofacial Surgeons J Oral Maxillofac Surg -:1.e1-1.e7, 2019
Orbital fractures are a common result of blunt facial trauma and can occur as an isolated fracture or with significant adjacent injuries. Pure orbital fractures have also been referred to as ‘‘blowout fractures’’ and
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will only involve the orbital walls without involvement of the inferior orbital rim. Because of the thin nature of the floor and medial walls, these regions have been most frequently involved in blowout fractures.1
*Resident, Oregon Health & Science University, Portland, OR.
Address correspondence and reprint requests to Dr Dennis: Head
yFellow, Head & Neck Surgical Associates, Portland, OR.
& Neck Surgical Associates, 1849 NW Kearney St, Rm 300, Portland,
zDirector, Department of Clinical Research, Legacy Research Institute, Portland, OR
OR 97209; e-mail: [email protected] Received August 19 2019
xAttending Surgeon, Head & Neck Surgical Associates, Portland,
Accepted October 30 2019 Ó 2019 Published by Elsevier Inc. on behalf of the American Association of Oral
OR. Conflict of Interest Disclosures: None of the authors have any Q5
and Maxillofacial Surgeons
relevant financial relationship(s) with a commercial interest.
0278-2391/19/31258-3 https://doi.org/10.1016/j.joms.2019.10.028
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TRANSORBITAL VERSUS TRANSANTRAL APPROACH FOR ORBITAL FLOOR FRACTURES
Although the diagnosis itself will not be challenging in the era of ubiquitous 3-dimensional (3D) imaging, the indications for operative intervention are less clear. Left unrepaired, the patient has the risk of developing enophthalmos, permanent gaze restriction, persistent diplopia, and/or vertical dystopia.2 However, the presence of edema and hematoma in the immediate postinjury setting will often make these clinical findings difficult to assess. Thus, most surgeons will initially use the size of the fracture and displacement of the orbital contents as evaluated from the imaging studies and the clinical examination findings to determine the need for operative intervention. Because of the ambiguity, more objective criteria have been outlined in an attempt to simplify clinical decision making. Some suggested indications for operative intervention have included fractures greater than 2 cm or more than 50% of the floor area.3 Burnstine4 proposed commonly followed guidelines, which include indications for immediate repair, delayed repair, and observation. The reasons for immediate repair included early enophthalmos or vertical dystopia, nonresolving oculocardiac reflex, and muscle entrapment (gaze restriction). Because these account for few patients with orbital blowout fractures, the benefit of intervention for most patients has remained uncertain. Although 1 to 2 weeks of close observation will be reasonable for some patients, this will inevitably result in some patients becoming lost to follow-up or experiencing insurance obstacles. An accurate correlation between fracture severity and enophthalmos has been identified as a critical link in predicting for surgical benefit. The degree of enophthalmos found to be clinically relevant is 2 mm or greater; thus, efforts have ensued to identify the degree of orbital volume change that will correlate with 2 mm of enophthalmos.5 The cited increases in orbital volume correlating with at least 2 mm of enophthalmos have range from 1.6 to 4.3 mL.6,7 In the largest study to date on orbital volume and enophthalmos, Yang et al8 identified an orbital volume of 106.85% compared with the control orbit as predictive of at least 2 mm of enophthalmos in 71.7% of patients. Regardless of the exact ratio, the clear correlation between the orbital volume change and the development of enophthalmos aligns with the goal of any orbital blowout repair—orbital volume correction. Although this goal has remained the same, the surgical approaches and strategies of repair have varied greatly. Access to the orbital floor has traditionally been achieved with a transorbital approach using lower eyelid incisions. An alternative approach through a maxillary vestibular incision and subsequent transantral access was described in the 1970s.9 Because of the lack of rigid fixation devices available, early transantral experimentation was mostly abandoned in favor
of transorbital approaches. However, technological advances in hardware ignited a resurgence in the technique in the 2000s with and without the use of an endoscope.10 The advantages of the transantral approach are essentially a zero risk of postoperative eyelid deformities because the eyelid and surrounding skin will be left undisturbed and the relative avoidance of the intraorbital fat, which can contribute to unpredictable atrophy. Numerous reduction and fixation techniques have been used, including plate fixation, Medpor (Stryker, Kalamazoo, MI), balloon, autogenous bone, and hybrids of these techniques.11-13 Most recently, our group has reported on 4 reconstructive techniques using the transantral approach without the need for an endoscope.14 Although case series studies have reported positive esthetic and functional outcomes, to the best of our knowledge, the only existing orbital volume analysis of transantral repairs was a cadaver study that assessed artificially created fractures.15 The purpose of the present study was to quantitatively compare orbital volume correction in patients with isolated orbital floor fractures who had undergone repair using a transorbital or transantral approach. We hypothesized that the orbital volume correction using transantral approaches would be comparable to the correction with transorbital approaches for isolated orbital floor blowout fractures. Furthermore, we hypothesized that scrutinizing 2 separate techniques for transantral plating would yield similar degrees of orbital volume correction.
Materials and Methods STUDY DESIGN AND SAMPLE
The present study was designed as a retrospective cohort study. The study population was composed of patients who had undergone repair of isolated, unilateral orbital floor blowout fractures at Legacy Emanuel Medical Center (LEMC), performed by a single group practice (Head & Neck Surgical Associates, Portland, OR) from 2013 to 2018. Expedited approval was obtained from the LEMC institutional review board, given the retrospective nature of our study. A patient list was collected by manually interrogating the LEMC operative room log spanning the study dates for all facial trauma cases. The patients were initially included if any diagnosis of an orbital fracture had been recorded. The exclusion criteria were then applied with the following parameters: the presence of any nonorbital floor facial fracture, the presence of bilateral orbital floor fractures, the lack of postoperative imaging studies or postoperative imaging studies that were inaccessible to us, postoperative imaging studies that did not include the entire bony orbit, and incomplete operative records.
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DENNIS ET AL
After the inclusion and exclusion criteria had been applied, 21 patients were included in the present study. Their operative records were reviewed to identify the surgical approach. Of the 21 patients, 9 had undergone repair using a transorbital approach and 12, a transantral approach. The transantral cohort was then further separated by reduction and fixation methods. Of the 12 patients in the transantral cohort, 7 had undergone repair with a flat, broad plate (FBP) that was vendor specific (KLS-Martin, Jacksonville FL), and 5 had undergone repair using a narrow, straight plate (NSP; Fig 1). In brief, the FBP is intended to rest on the posterior ledge and for the plate itself to support the entirety of the herniated orbital contents. In contrast, the NSP is placed on the posterior ledge and is used as a strut to reduce the orbital floor bone, which then supports the orbital soft tissue contents. Both of these plating methods use a large antral window with or without the use of an endoscope. VARIABLES
The predictor variable for the present study was the technique of orbital repair used—transorbital or transantral. The outcome variable was the orbital volume
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FIGURE 1. A, Example of a flat, broad plate (FBP) from KLS-Martin (Jacksonville FL) designed for transantral use. B, Example of a narrow, straight plate (NSP), which is not vendor specific. Dennis et al. Transorbital Versus Transantral Approach for Orbital Floor Fractures. J Oral Maxillofac Surg 2019.
correction, calculated as the ratio of the corrected, injured orbit to the contralateral control orbit. Other measured variables included the preoperative orbital defect size and analysis of the transantral cohort according to the plating technique used. STATISTICAL ANALYSIS
The process of orbital volume calculation began with the collection of the pre- and postoperative DICOM (Digital Imaging and Communications in Medicine) data sets. Orbital analysis was performed on the uninjured orbit to allow the use of these data as the control. The postoperative injured orbital volume was also calculated. A third volume calculation was performed if adequate imaging studies were available of the preoperative injured orbit. The orbital volume calculations were obtained using 3D Slicer, version 4.10.2, a free, open-source imaging processing and visualization software platform (Fig 2).16 Because evaluating the performance of the 3D Slicer software was not an aim of our study, all volume calculations were performed by 1 of us to reduce intraoperator variability. Manual segmentation was first traced in a sagittal plane to establish the anterior and posterior extents of the orbit, areas of common difficulty in reproduction. The anterior limit of the orbit was, therefore, determined by the superior and inferior orbital rims using the maximal point of convexity of each structure. The posterior extent of the orbit was delineated by a vertical plane established using the posterior extent of the superior orbital fissure along the lesser wing of the sphenoid. Next, axial segmentation was accomplished using the lateral and medial orbital rims in a similar fashion. Because of the ambiguity in the convexity of the medial orbit, the junction of the denser maxillary bone with the less dense lacrimal bone was used as the medial limit. Finally, the coronal segmentation was easily traced using previously established boundaries. The degree of manual segmentation was standardized as 10 planes each for the sagittal, axial, and coronal orientations. Once the 3D segments had been created, the Slicer tools were used to fill and smooth the volumes. Quantitative orbit volumetric analysis was achieved within 3D Slicer, using the Segment Statistics plugin, which calculates the volume by tallying the voxels in the segmented selection. The recorded data were assessed using the R Language and Environment for Statistical Computing, version 3.5.1 (R Foundation, Vienna, Austria) to compute the analysis of variance and paired t test results.
Results After the orbital volume calculations in Slicer, the volume characteristics were analyzed to find any differences among the FBP, NSP, and transorbital cohorts.
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TRANSORBITAL VERSUS TRANSANTRAL APPROACH FOR ORBITAL FLOOR FRACTURES
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FIGURE 2. A, Manual segmentation in axial cross-section. B, Three-dimensional view of the orbits after segmentation and smoothing. C, Manual segmentation in sagittal cross-section. D, Manual segmentation in coronal cross-section. Dennis et al. Transorbital Versus Transantral Approach for Orbital Floor Fractures. J Oral Maxillofac Surg 2019.
No statistically significant differences were found in the volume of the preoperative, postoperative, or control orbits among the cohorts (Table 1). The volume changes achieved with each approach are illustrated in Figure 3. Combining the 2 transantral approaches into a single transantral cohort to increase the group size did not change these results. The average combined transantral control orbital volume was 30.7 cm3 compared with 33.3 cm3 for the transorbital control orbital volume (P = .197). To identify a possible injury severity bias, the defect volumes were calculated for each group by subtracting the control volume from the preoperative volumes. The mean orbital defect size for the transorbital cases was 4.87 cm3, which was less than that of the transantral
Discussion
Table 1. VOLUME COMPARISON
Variable Preoperative injured orbit Control uninjured orbit Postoperative injured orbit Defect size
cohorts, although the difference was not statistically significant (Table 1). Orbital volume correction was calculated as a percentage of the control orbital volume. A visual representation of the accuracy in orbital volume correction for each surgical cohort is presented in Figure 4. The mean percentage of volume correction for the FBP, NSP, and transorbital cohorts was 99.71, 99.08, and 102.69% respectively (P = .104; Table 2). When the transantral approaches were combined into a single cohort, the mean percentage of volume correction was 99.44% (P = .033) compared with the mean percentage of volume correction for the transorbital cohort mean of 102.69% (Table 3).
FBP (cm3)
NSP (cm3)
TO (cm3)
P Value
34.5
37.4
37.5
.608
29.6
32.2
33.3
.278
29.7
32.4
32.5
.438
5.00
5.61
4.87
.907
Abbreviations: FBP, flat, broad plate; NSP, narrow, straight plate; TO, transorbital. Dennis et al. Transorbital Versus Transantral Approach for Orbital Floor Fractures. J Oral Maxillofac Surg 2019.
We hypothesized that orbital volume correction achieved when using the 2 transantral techniques would be comparable to that achieved using the transorbital method. Our results have supported this hypothesis because the difference in volume correction among the 3 cohorts was not statistically significant. These data provide clinical evidence of comparable orbital volume correction for transantral approaches compared with transorbital approaches, which had previously only been shown in a cadaver study by Wallace et al.15 One difference between their study and ours is that their transantral technique used an endoscope and endoscopes were not used in any of the cases included in the present
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FIGURE 3. Bar graph showing the preoperative and postoperative orbital volumes grouped by surgical approach. FBP, flat, broad plate; NSP, narrow, straight plate; Post, postoperative; Pre, preoperative; TO, transorbital. Dennis et al. Transorbital Versus Transantral Approach for Orbital Floor Fractures. J Oral Maxillofac Surg 2019.
study. Combining the 2 transantral plating techniques into a single cohort did allow us to show that the transantral approach had a small, but statis-
tically significant, improvement in the accuracy of the reduction compared with the transorbital approach (Table 3).
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DENNIS ET AL
FIGURE 4. Bar graph showing the comparison of the postoperative orbital volume with the contralateral uninjured control orbital volume, grouped by surgical approach. FBP, flat, broad plate; NSP, narrow, straight plate; Post, postoperative; Pre, preoperative; TO, transorbital. Dennis et al. Transorbital Versus Transantral Approach for Orbital Floor Fractures. J Oral Maxillofac Surg 2019.
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TRANSORBITAL VERSUS TRANSANTRAL APPROACH FOR ORBITAL FLOOR FRACTURES
Table 2. PERCENTAGE OF VOLUME CORRECTION STRATIFIED BY TECHNIQUE*
Technique FBP NSP TO
Mean SD 99.707 4.357 99.077 2.274 102.691 2.725
Abbreviations: FBP, flat, broad plate; NSP, narrow, straight plate; SD, standard deviation; TO, transorbital. * P = .104. Dennis et al. Transorbital Versus Transantral Approach for Orbital Floor Fractures. J Oral Maxillofac Surg 2019.
Other considerations included the calculation of the defect sizes in each technique group. By identifying the absence of differences in defect size (Table 1) and a greater mean defect in the transantral group, we could rule out the possibility that our results were skewed by case selection (ie, that transantral approaches were selectively performed when the patient had had a smaller defect). In addition to comparing the surgical techniques, the absolute values of correction deserve scrutiny. The data presented in Figure 4 assist in visualizing the remarkably accurate degree of volume reduction in all the groups. Our findings indicate that, on average, transantral approaches might slightly underrepair the orbit compared with the control orbital volume and that transorbital implant placement might tend to overrepair the orbit. Logic also supports this, because implants placed through the orbit are intended to rest on bony ledges, rendering a slight degree of overcorrection owing to implant bulk. One could argue that overcorrection in a transorbital approach would be preferable because of the possibility of fat atrophy. The correlation between enophthalmos and orbital volume has been extensively researched, because the correlation is the key link between the 3D imaging findings and the clinical outcomes. We chose to represent our volume correction as a percentage of the control orbital volume, because we found that the individual orbital volume varies greatly between individuals. Every case analyzed in the present study had a more accurate volume correction than the 106.85% cited by Yang et al8 in their analysis of volume correlation with enophthalmos. Although not included in the statistical analysis because of redundancy, the mean volume difference in each group was less than 1 cm,3, less than all reported volumes associated with clinically relevant enophthalmos.6,7 One area worth attention is the method used for orbital volume calculation. An additional goal of the present study was to explore the capability of a free, open source platform that could be used
Table 3. PERCENTAGE OF VOLUME CORRECTION STRATIFIED BY APPROACH*
Approach TA TO
Mean SD 99.444 3.513 102.691 2.725
Abbreviations: SD, standard deviation; TA, transantral; TO, transorbital. * P = .033. Dennis et al. Transorbital Versus Transantral Approach for Orbital Floor Fractures. J Oral Maxillofac Surg 2019.
without a background in computer science or software engineering. In other reported orbital volume calculation studies, the volume rendering software costs have ranged from $4000 to $10,000 annually for those software packages that publish their fees.17-19 This exorbitant cost has been a barrier to access for surgeons not affiliated with researchbased academic institutions. Slicer and Horos are both free and open source software programs, allowing for numerous plugins such as the one used for the quantitative analysis in the present study. Slicer was created in 1998 for the purpose of biomedical research and, because it is open source, has benefited from a plethora of developers with both private and federal funding. At the time of writing, 552 peerreviewed publications had used Slicer tools, the vast majority of which were medically related. Regarding the technique of volume calculation itself, no consensus has been reached for the best method. Significant technological advancements have occurred since the first volume calculation of Chinese orbits using sand.20 Defining the posterior orbit has been fraught with difficulty owing to foramen and fissures. The anterior orbital extent has been cited as the most poorly defined boundary in reported studies.21 Therefore, the volumes cited in the present study cannot be compared with the absolute volumes from other sources. It is also the reason we chose to report our volume correction as a percentage of the control orbit volume and not as the absolute volume. Some investigators have also recommended simply calculating the defect volume itself, instead of the entire orbit. However, Yang et al8 found that the orbital volume is a more reliable predictor of the development of enophthalmos than is the defect volume. A commonly cited statistic that could undermine orbital volume correction studies is the asymmetry present in human orbits. An early computed tomography study from 1985 reported a difference of 0 to 8% between the left and right orbits, prompting frequent citations of a ‘‘normal’’ orbital variation of 7 to 8%.22 However, a closer examination showed
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DENNIS ET AL
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that the mean difference in volume was actually only 1.8% in the same study, despite only having been reported as a range. More contemporary studies have reported that this variation is less than 7 to 8% and was reported as 2.1% in a recent study.19 In conclusion, despite an abundance of data on pure orbital floor blowout fractures, a great amount of subjectivity remains with regard to management. The Head & Neck Surgical Associates group has trialed various approaches and biomaterials for the repair of blowout fractures over the course of decades. It was the variety in techniques used among the surgeons that this project was performed as a retrospective study. The transantral approach has increased in popularity at LEMC (Portland, OR), and we suspect this has been true in other training programs. Several avenues of investigation could follow our study. First, clinical data on enophthalmos in cohorts of these varying approaches would allow a more direct method of assessing surgical success. Next, we have a detailed report in preparation of an investigation of the morbidity and resource usage for the different orbital approaches. Finally, we hope that open source software continues to increase in popularity and, that in the future, rapid volume calculation by clinicians could help predict clinical deficits and allow for more objective management of orbital floor blowout fractures. In brief, the results from our study have validated the use of the transantral approach without the use of an endoscope in the management of pure orbital floor blowout fractures to restore the orbital volume.
References 1. Ellis E: Orbital trauma. Oral Maxillofac Surg Clin North Am 24: 629, 2012 2. Cole P, Boyd V, Banerji S, Hollier LH: Comprehensive management of orbital fractures. Plast Reconstr Surg 120(suppl 2): 57S, 2007 3. Hawes MJ, Dortzbach RK: Surgery on orbital floor fractures: Influence of time of repair and fracture size. Ophthalmology 90: 1066, 1983 4. Burnstine MA: Clinical recommendations for repair of isolated orbital floor fractures: An evidence-based analysis. Ophthalmology 109:1207, 2002
5. Sung YS, Chung CM, Hong IP: The correlation between the degree of enophthalmos and the extent of fracture in medial orbital wall fracture left untreated for over six months: A retrospective analysis of 81 cases at a single institution. Arch Plast Surg 40:335, 2013 6. Ploder O, Klug C, Voracek M, et al: Evaluation of computer-based area and volume measurement from coronal computed tomography scans in isolated blowout fractures of the orbital floor. J Oral Maxillofac Surg 60:1267, 2002 7. Raskin EM, Millman AL, Lubkin V, et al: Prediction of late enophthalmos by volumetric analysis of orbital fractures. Ophthalmic Plast Reconstr Surg 14:19, 1998 8. Yang J-H, Hwang SB, Shin JY, et al: 3D volumetric analysis of relationship between the orbital volume ratio and enophthalmos in unoperated blowout fractures. J Oral Maxillofac Surg 77:1847, 2019 9. Walter WL: Early surgical repair of blowout fracture of the orbital floor by using the transantral approach. South Med J 65:1229, 1972 10. Ducic Y, Verret DJ: Endoscopic transantral repair of orbital floor fractures. Otolaryngol Head Neck Surg 140:849, 2009 11. Kashimura T, Soejima K, Kikuchi Y, Nakazawa H: Stability of orbital floor fracture fixation after endoscope-assisted balloon placement. J Craniofac Surg 28:e669, 2017 12. Kim JH, Kook MS, Ryu SY, et al: A simple technique for the treatment of inferior orbital blow-out fracture: A transantral approach, open reduction, and internal fixation with miniplate and screws. J Oral Maxillofac Surg 66:2488, 2008 13. Nahlieli O, Bar-droma E, Zagury A, et al: Endoscopic intraoral plating of orbital floor fractures. J Oral Maxillofac Surg 65: 1751, 2007 14. Govind A, Dierks E, Bell RB, Amundson M: Four practical reconstructive techniques using the transantral approach to the orbital floor without the need for an endoscope. J Oral Maxillofac Surg 77:2074, 2019 15. Wallace TD, Moore CC, Bromwich MA, Matic DB: Endoscopic repair of orbital floor fractures: Computed tomographic analysis using a cadaveric model. J Otolaryngol 35:1, 2006 16. Fedorov A, Beichel R, Kalpathy-Cramer J, et al: 3D Slicer as an image computing platform for the quantitative imaging network. Magn Reson Imaging 30:1323, 2012 17. Strong EB, Fuller SC, Chahal HS: Computer-aided analysis of orbital volume: A novel technique. Ophthalmic Plast Reconstr Surg 29:1, 2013 18. Gribova MN, Pluijmers BI, Resnick CM, et al: Is there a difference in orbital volume between affected and unaffected sides in patients with unilateral craniofacial microsomia? J Oral Maxillofac Surg 76:2625, 2018 19. Lieger O, Schaub M, Taghizadeh E, B€ uchler P: How symmetrical are bony orbits in humans? J Oral Maxillofac Surg 77:118, 2019 20. P’An TH: Measurement of the Chinese orbit. J Anat 67:596, 1933 21. Mottini M, Wolf CA, Seyed Jafari SM, et al: Stereographic measurement of orbital volume, a digital reproducible evaluation method. Br J Ophthalmol 101:1431, 2017 22. Forbes G, Gehring DG, Gorman CA, et al: Volume measurements of normal orbital structures by computed tomographic analysis. AJR Am J Roentgenol 145:149, 1985
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CRANIOMAXILLOFACIAL TRAUMA
Orbital Volume Correction in Orbital Floor Fractures: A Comparison of Transorbital and Transantral Techniques
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Peter Dennis, DMD, MD,* Akshay Govind, DDS, MD, MHI,y Shaban Demirel, OD, PhD,z and Melissa Amundson, DDSx
Q6 Q3
Purpose:
We compared the accuracy of orbital volume correction between the transorbital and transantral reconstructive techniques.
Materials and Methods:
A retrospective cohort study was performed of patients who had undergone repair of isolated, unilateral orbital floor blowout fractures at Legacy Emanuel Hospital from 2013 to 2018. A total of 21 patients were identified and included in the predictor variable cohorts of the transorbital versus transantral repair technique. The outcome variable of orbital volume correction was evaluated by comparing the volume of the postoperative repaired orbits with that of the contralateral noninjured orbits. Additional ordinal variables analyzed included the preoperative orbital defect size and analysis of the transantral cohort stratified by the plating technique used. Data were assessed using analysis of variance and paired t tests.
Results:
A transantral approach was used for orbital repair in 9 patients. In these patients, the postoperative orbital volume in the injured orbit was 2.69% greater than that in the uninjured orbit. The 12 patients who had undergone transantral repair had a postoperative orbital volume in the injured orbit that was 0.56% smaller than that of the uninjured orbit (P = .033). Division of the transantral cohort into 2 different plating techniques identified a less than 1% difference in mean orbital volume correction between the 2 techniques (P = .104). The average defect volume before transorbital repair was 4.87 cm3 compared with 5.22 cm3 for transantral repair (P = .907). Conclusions: The results from the present study have shown that the accuracy of orbital volume correction using the transantral approach will be comparable to that of the transorbital approach, as shown by a small, but statistically significant, increased accuracy in the volume correction with the transantral approach. Additional investigation to establish clinical correlations with these findings should be conducted. Ó 2019 Published by Elsevier Inc. on behalf of the American Association of Oral and Maxillofacial Surgeons J Oral Maxillofac Surg -:1.e1-1.e7, 2019
Orbital fractures are a common result of blunt facial trauma and can occur as an isolated fracture or with significant adjacent injuries. Pure orbital fractures have also been referred to as ‘‘blowout fractures’’ and
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will only involve the orbital walls without involvement of the inferior orbital rim. Because of the thin nature of the floor and medial walls, these regions have been most frequently involved in blowout fractures.1
*Resident, Oregon Health & Science University, Portland, OR.
Address correspondence and reprint requests to Dr Dennis: Head
yFellow, Head & Neck Surgical Associates, Portland, OR.
& Neck Surgical Associates, 1849 NW Kearney St, Rm 300, Portland,
zDirector, Department of Clinical Research, Legacy Research Institute, Portland, OR
OR 97209; e-mail: [email protected] Received August 19 2019
xAttending Surgeon, Head & Neck Surgical Associates, Portland,
Accepted October 30 2019 Ó 2019 Published by Elsevier Inc. on behalf of the American Association of Oral
OR. Conflict of Interest Disclosures: None of the authors have any Q5
and Maxillofacial Surgeons
relevant financial relationship(s) with a commercial interest.
0278-2391/19/31258-3 https://doi.org/10.1016/j.joms.2019.10.028
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TRANSORBITAL VERSUS TRANSANTRAL APPROACH FOR ORBITAL FLOOR FRACTURES
Although the diagnosis itself will not be challenging in the era of ubiquitous 3-dimensional (3D) imaging, the indications for operative intervention are less clear. Left unrepaired, the patient has the risk of developing enophthalmos, permanent gaze restriction, persistent diplopia, and/or vertical dystopia.2 However, the presence of edema and hematoma in the immediate postinjury setting will often make these clinical findings difficult to assess. Thus, most surgeons will initially use the size of the fracture and displacement of the orbital contents as evaluated from the imaging studies and the clinical examination findings to determine the need for operative intervention. Because of the ambiguity, more objective criteria have been outlined in an attempt to simplify clinical decision making. Some suggested indications for operative intervention have included fractures greater than 2 cm or more than 50% of the floor area.3 Burnstine4 proposed commonly followed guidelines, which include indications for immediate repair, delayed repair, and observation. The reasons for immediate repair included early enophthalmos or vertical dystopia, nonresolving oculocardiac reflex, and muscle entrapment (gaze restriction). Because these account for few patients with orbital blowout fractures, the benefit of intervention for most patients has remained uncertain. Although 1 to 2 weeks of close observation will be reasonable for some patients, this will inevitably result in some patients becoming lost to follow-up or experiencing insurance obstacles. An accurate correlation between fracture severity and enophthalmos has been identified as a critical link in predicting for surgical benefit. The degree of enophthalmos found to be clinically relevant is 2 mm or greater; thus, efforts have ensued to identify the degree of orbital volume change that will correlate with 2 mm of enophthalmos.5 The cited increases in orbital volume correlating with at least 2 mm of enophthalmos have range from 1.6 to 4.3 mL.6,7 In the largest study to date on orbital volume and enophthalmos, Yang et al8 identified an orbital volume of 106.85% compared with the control orbit as predictive of at least 2 mm of enophthalmos in 71.7% of patients. Regardless of the exact ratio, the clear correlation between the orbital volume change and the development of enophthalmos aligns with the goal of any orbital blowout repair—orbital volume correction. Although this goal has remained the same, the surgical approaches and strategies of repair have varied greatly. Access to the orbital floor has traditionally been achieved with a transorbital approach using lower eyelid incisions. An alternative approach through a maxillary vestibular incision and subsequent transantral access was described in the 1970s.9 Because of the lack of rigid fixation devices available, early transantral experimentation was mostly abandoned in favor
of transorbital approaches. However, technological advances in hardware ignited a resurgence in the technique in the 2000s with and without the use of an endoscope.10 The advantages of the transantral approach are essentially a zero risk of postoperative eyelid deformities because the eyelid and surrounding skin will be left undisturbed and the relative avoidance of the intraorbital fat, which can contribute to unpredictable atrophy. Numerous reduction and fixation techniques have been used, including plate fixation, Medpor (Stryker, Kalamazoo, MI), balloon, autogenous bone, and hybrids of these techniques.11-13 Most recently, our group has reported on 4 reconstructive techniques using the transantral approach without the need for an endoscope.14 Although case series studies have reported positive esthetic and functional outcomes, to the best of our knowledge, the only existing orbital volume analysis of transantral repairs was a cadaver study that assessed artificially created fractures.15 The purpose of the present study was to quantitatively compare orbital volume correction in patients with isolated orbital floor fractures who had undergone repair using a transorbital or transantral approach. We hypothesized that the orbital volume correction using transantral approaches would be comparable to the correction with transorbital approaches for isolated orbital floor blowout fractures. Furthermore, we hypothesized that scrutinizing 2 separate techniques for transantral plating would yield similar degrees of orbital volume correction.
Materials and Methods STUDY DESIGN AND SAMPLE
The present study was designed as a retrospective cohort study. The study population was composed of patients who had undergone repair of isolated, unilateral orbital floor blowout fractures at Legacy Emanuel Medical Center (LEMC), performed by a single group practice (Head & Neck Surgical Associates, Portland, OR) from 2013 to 2018. Expedited approval was obtained from the LEMC institutional review board, given the retrospective nature of our study. A patient list was collected by manually interrogating the LEMC operative room log spanning the study dates for all facial trauma cases. The patients were initially included if any diagnosis of an orbital fracture had been recorded. The exclusion criteria were then applied with the following parameters: the presence of any nonorbital floor facial fracture, the presence of bilateral orbital floor fractures, the lack of postoperative imaging studies or postoperative imaging studies that were inaccessible to us, postoperative imaging studies that did not include the entire bony orbit, and incomplete operative records.
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After the inclusion and exclusion criteria had been applied, 21 patients were included in the present study. Their operative records were reviewed to identify the surgical approach. Of the 21 patients, 9 had undergone repair using a transorbital approach and 12, a transantral approach. The transantral cohort was then further separated by reduction and fixation methods. Of the 12 patients in the transantral cohort, 7 had undergone repair with a flat, broad plate (FBP) that was vendor specific (KLS-Martin, Jacksonville FL), and 5 had undergone repair using a narrow, straight plate (NSP; Fig 1). In brief, the FBP is intended to rest on the posterior ledge and for the plate itself to support the entirety of the herniated orbital contents. In contrast, the NSP is placed on the posterior ledge and is used as a strut to reduce the orbital floor bone, which then supports the orbital soft tissue contents. Both of these plating methods use a large antral window with or without the use of an endoscope. VARIABLES
The predictor variable for the present study was the technique of orbital repair used—transorbital or transantral. The outcome variable was the orbital volume
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FIGURE 1. A, Example of a flat, broad plate (FBP) from KLS-Martin (Jacksonville FL) designed for transantral use. B, Example of a narrow, straight plate (NSP), which is not vendor specific. Dennis et al. Transorbital Versus Transantral Approach for Orbital Floor Fractures. J Oral Maxillofac Surg 2019.
correction, calculated as the ratio of the corrected, injured orbit to the contralateral control orbit. Other measured variables included the preoperative orbital defect size and analysis of the transantral cohort according to the plating technique used. STATISTICAL ANALYSIS
The process of orbital volume calculation began with the collection of the pre- and postoperative DICOM (Digital Imaging and Communications in Medicine) data sets. Orbital analysis was performed on the uninjured orbit to allow the use of these data as the control. The postoperative injured orbital volume was also calculated. A third volume calculation was performed if adequate imaging studies were available of the preoperative injured orbit. The orbital volume calculations were obtained using 3D Slicer, version 4.10.2, a free, open-source imaging processing and visualization software platform (Fig 2).16 Because evaluating the performance of the 3D Slicer software was not an aim of our study, all volume calculations were performed by 1 of us to reduce intraoperator variability. Manual segmentation was first traced in a sagittal plane to establish the anterior and posterior extents of the orbit, areas of common difficulty in reproduction. The anterior limit of the orbit was, therefore, determined by the superior and inferior orbital rims using the maximal point of convexity of each structure. The posterior extent of the orbit was delineated by a vertical plane established using the posterior extent of the superior orbital fissure along the lesser wing of the sphenoid. Next, axial segmentation was accomplished using the lateral and medial orbital rims in a similar fashion. Because of the ambiguity in the convexity of the medial orbit, the junction of the denser maxillary bone with the less dense lacrimal bone was used as the medial limit. Finally, the coronal segmentation was easily traced using previously established boundaries. The degree of manual segmentation was standardized as 10 planes each for the sagittal, axial, and coronal orientations. Once the 3D segments had been created, the Slicer tools were used to fill and smooth the volumes. Quantitative orbit volumetric analysis was achieved within 3D Slicer, using the Segment Statistics plugin, which calculates the volume by tallying the voxels in the segmented selection. The recorded data were assessed using the R Language and Environment for Statistical Computing, version 3.5.1 (R Foundation, Vienna, Austria) to compute the analysis of variance and paired t test results.
Results After the orbital volume calculations in Slicer, the volume characteristics were analyzed to find any differences among the FBP, NSP, and transorbital cohorts.
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FIGURE 2. A, Manual segmentation in axial cross-section. B, Three-dimensional view of the orbits after segmentation and smoothing. C, Manual segmentation in sagittal cross-section. D, Manual segmentation in coronal cross-section. Dennis et al. Transorbital Versus Transantral Approach for Orbital Floor Fractures. J Oral Maxillofac Surg 2019.
No statistically significant differences were found in the volume of the preoperative, postoperative, or control orbits among the cohorts (Table 1). The volume changes achieved with each approach are illustrated in Figure 3. Combining the 2 transantral approaches into a single transantral cohort to increase the group size did not change these results. The average combined transantral control orbital volume was 30.7 cm3 compared with 33.3 cm3 for the transorbital control orbital volume (P = .197). To identify a possible injury severity bias, the defect volumes were calculated for each group by subtracting the control volume from the preoperative volumes. The mean orbital defect size for the transorbital cases was 4.87 cm3, which was less than that of the transantral
Discussion
Table 1. VOLUME COMPARISON
Variable Preoperative injured orbit Control uninjured orbit Postoperative injured orbit Defect size
cohorts, although the difference was not statistically significant (Table 1). Orbital volume correction was calculated as a percentage of the control orbital volume. A visual representation of the accuracy in orbital volume correction for each surgical cohort is presented in Figure 4. The mean percentage of volume correction for the FBP, NSP, and transorbital cohorts was 99.71, 99.08, and 102.69% respectively (P = .104; Table 2). When the transantral approaches were combined into a single cohort, the mean percentage of volume correction was 99.44% (P = .033) compared with the mean percentage of volume correction for the transorbital cohort mean of 102.69% (Table 3).
FBP (cm3)
NSP (cm3)
TO (cm3)
P Value
34.5
37.4
37.5
.608
29.6
32.2
33.3
.278
29.7
32.4
32.5
.438
5.00
5.61
4.87
.907
Abbreviations: FBP, flat, broad plate; NSP, narrow, straight plate; TO, transorbital. Dennis et al. Transorbital Versus Transantral Approach for Orbital Floor Fractures. J Oral Maxillofac Surg 2019.
We hypothesized that orbital volume correction achieved when using the 2 transantral techniques would be comparable to that achieved using the transorbital method. Our results have supported this hypothesis because the difference in volume correction among the 3 cohorts was not statistically significant. These data provide clinical evidence of comparable orbital volume correction for transantral approaches compared with transorbital approaches, which had previously only been shown in a cadaver study by Wallace et al.15 One difference between their study and ours is that their transantral technique used an endoscope and endoscopes were not used in any of the cases included in the present
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FIGURE 3. Bar graph showing the preoperative and postoperative orbital volumes grouped by surgical approach. FBP, flat, broad plate; NSP, narrow, straight plate; Post, postoperative; Pre, preoperative; TO, transorbital. Dennis et al. Transorbital Versus Transantral Approach for Orbital Floor Fractures. J Oral Maxillofac Surg 2019.
study. Combining the 2 transantral plating techniques into a single cohort did allow us to show that the transantral approach had a small, but statis-
tically significant, improvement in the accuracy of the reduction compared with the transorbital approach (Table 3).
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DENNIS ET AL
FIGURE 4. Bar graph showing the comparison of the postoperative orbital volume with the contralateral uninjured control orbital volume, grouped by surgical approach. FBP, flat, broad plate; NSP, narrow, straight plate; Post, postoperative; Pre, preoperative; TO, transorbital. Dennis et al. Transorbital Versus Transantral Approach for Orbital Floor Fractures. J Oral Maxillofac Surg 2019.
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TRANSORBITAL VERSUS TRANSANTRAL APPROACH FOR ORBITAL FLOOR FRACTURES
Table 2. PERCENTAGE OF VOLUME CORRECTION STRATIFIED BY TECHNIQUE*
Technique FBP NSP TO
Mean SD 99.707 4.357 99.077 2.274 102.691 2.725
Abbreviations: FBP, flat, broad plate; NSP, narrow, straight plate; SD, standard deviation; TO, transorbital. * P = .104. Dennis et al. Transorbital Versus Transantral Approach for Orbital Floor Fractures. J Oral Maxillofac Surg 2019.
Other considerations included the calculation of the defect sizes in each technique group. By identifying the absence of differences in defect size (Table 1) and a greater mean defect in the transantral group, we could rule out the possibility that our results were skewed by case selection (ie, that transantral approaches were selectively performed when the patient had had a smaller defect). In addition to comparing the surgical techniques, the absolute values of correction deserve scrutiny. The data presented in Figure 4 assist in visualizing the remarkably accurate degree of volume reduction in all the groups. Our findings indicate that, on average, transantral approaches might slightly underrepair the orbit compared with the control orbital volume and that transorbital implant placement might tend to overrepair the orbit. Logic also supports this, because implants placed through the orbit are intended to rest on bony ledges, rendering a slight degree of overcorrection owing to implant bulk. One could argue that overcorrection in a transorbital approach would be preferable because of the possibility of fat atrophy. The correlation between enophthalmos and orbital volume has been extensively researched, because the correlation is the key link between the 3D imaging findings and the clinical outcomes. We chose to represent our volume correction as a percentage of the control orbital volume, because we found that the individual orbital volume varies greatly between individuals. Every case analyzed in the present study had a more accurate volume correction than the 106.85% cited by Yang et al8 in their analysis of volume correlation with enophthalmos. Although not included in the statistical analysis because of redundancy, the mean volume difference in each group was less than 1 cm,3, less than all reported volumes associated with clinically relevant enophthalmos.6,7 One area worth attention is the method used for orbital volume calculation. An additional goal of the present study was to explore the capability of a free, open source platform that could be used
Table 3. PERCENTAGE OF VOLUME CORRECTION STRATIFIED BY APPROACH*
Approach TA TO
Mean SD 99.444 3.513 102.691 2.725
Abbreviations: SD, standard deviation; TA, transantral; TO, transorbital. * P = .033. Dennis et al. Transorbital Versus Transantral Approach for Orbital Floor Fractures. J Oral Maxillofac Surg 2019.
without a background in computer science or software engineering. In other reported orbital volume calculation studies, the volume rendering software costs have ranged from $4000 to $10,000 annually for those software packages that publish their fees.17-19 This exorbitant cost has been a barrier to access for surgeons not affiliated with researchbased academic institutions. Slicer and Horos are both free and open source software programs, allowing for numerous plugins such as the one used for the quantitative analysis in the present study. Slicer was created in 1998 for the purpose of biomedical research and, because it is open source, has benefited from a plethora of developers with both private and federal funding. At the time of writing, 552 peerreviewed publications had used Slicer tools, the vast majority of which were medically related. Regarding the technique of volume calculation itself, no consensus has been reached for the best method. Significant technological advancements have occurred since the first volume calculation of Chinese orbits using sand.20 Defining the posterior orbit has been fraught with difficulty owing to foramen and fissures. The anterior orbital extent has been cited as the most poorly defined boundary in reported studies.21 Therefore, the volumes cited in the present study cannot be compared with the absolute volumes from other sources. It is also the reason we chose to report our volume correction as a percentage of the control orbit volume and not as the absolute volume. Some investigators have also recommended simply calculating the defect volume itself, instead of the entire orbit. However, Yang et al8 found that the orbital volume is a more reliable predictor of the development of enophthalmos than is the defect volume. A commonly cited statistic that could undermine orbital volume correction studies is the asymmetry present in human orbits. An early computed tomography study from 1985 reported a difference of 0 to 8% between the left and right orbits, prompting frequent citations of a ‘‘normal’’ orbital variation of 7 to 8%.22 However, a closer examination showed
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that the mean difference in volume was actually only 1.8% in the same study, despite only having been reported as a range. More contemporary studies have reported that this variation is less than 7 to 8% and was reported as 2.1% in a recent study.19 In conclusion, despite an abundance of data on pure orbital floor blowout fractures, a great amount of subjectivity remains with regard to management. The Head & Neck Surgical Associates group has trialed various approaches and biomaterials for the repair of blowout fractures over the course of decades. It was the variety in techniques used among the surgeons that this project was performed as a retrospective study. The transantral approach has increased in popularity at LEMC (Portland, OR), and we suspect this has been true in other training programs. Several avenues of investigation could follow our study. First, clinical data on enophthalmos in cohorts of these varying approaches would allow a more direct method of assessing surgical success. Next, we have a detailed report in preparation of an investigation of the morbidity and resource usage for the different orbital approaches. Finally, we hope that open source software continues to increase in popularity and, that in the future, rapid volume calculation by clinicians could help predict clinical deficits and allow for more objective management of orbital floor blowout fractures. In brief, the results from our study have validated the use of the transantral approach without the use of an endoscope in the management of pure orbital floor blowout fractures to restore the orbital volume.
References 1. Ellis E: Orbital trauma. Oral Maxillofac Surg Clin North Am 24: 629, 2012 2. Cole P, Boyd V, Banerji S, Hollier LH: Comprehensive management of orbital fractures. Plast Reconstr Surg 120(suppl 2): 57S, 2007 3. Hawes MJ, Dortzbach RK: Surgery on orbital floor fractures: Influence of time of repair and fracture size. Ophthalmology 90: 1066, 1983 4. Burnstine MA: Clinical recommendations for repair of isolated orbital floor fractures: An evidence-based analysis. Ophthalmology 109:1207, 2002
5. Sung YS, Chung CM, Hong IP: The correlation between the degree of enophthalmos and the extent of fracture in medial orbital wall fracture left untreated for over six months: A retrospective analysis of 81 cases at a single institution. Arch Plast Surg 40:335, 2013 6. Ploder O, Klug C, Voracek M, et al: Evaluation of computer-based area and volume measurement from coronal computed tomography scans in isolated blowout fractures of the orbital floor. J Oral Maxillofac Surg 60:1267, 2002 7. Raskin EM, Millman AL, Lubkin V, et al: Prediction of late enophthalmos by volumetric analysis of orbital fractures. Ophthalmic Plast Reconstr Surg 14:19, 1998 8. Yang J-H, Hwang SB, Shin JY, et al: 3D volumetric analysis of relationship between the orbital volume ratio and enophthalmos in unoperated blowout fractures. J Oral Maxillofac Surg 77:1847, 2019 9. Walter WL: Early surgical repair of blowout fracture of the orbital floor by using the transantral approach. South Med J 65:1229, 1972 10. Ducic Y, Verret DJ: Endoscopic transantral repair of orbital floor fractures. Otolaryngol Head Neck Surg 140:849, 2009 11. Kashimura T, Soejima K, Kikuchi Y, Nakazawa H: Stability of orbital floor fracture fixation after endoscope-assisted balloon placement. J Craniofac Surg 28:e669, 2017 12. Kim JH, Kook MS, Ryu SY, et al: A simple technique for the treatment of inferior orbital blow-out fracture: A transantral approach, open reduction, and internal fixation with miniplate and screws. J Oral Maxillofac Surg 66:2488, 2008 13. Nahlieli O, Bar-droma E, Zagury A, et al: Endoscopic intraoral plating of orbital floor fractures. J Oral Maxillofac Surg 65: 1751, 2007 14. Govind A, Dierks E, Bell RB, Amundson M: Four practical reconstructive techniques using the transantral approach to the orbital floor without the need for an endoscope. J Oral Maxillofac Surg 77:2074, 2019 15. Wallace TD, Moore CC, Bromwich MA, Matic DB: Endoscopic repair of orbital floor fractures: Computed tomographic analysis using a cadaveric model. J Otolaryngol 35:1, 2006 16. Fedorov A, Beichel R, Kalpathy-Cramer J, et al: 3D Slicer as an image computing platform for the quantitative imaging network. Magn Reson Imaging 30:1323, 2012 17. Strong EB, Fuller SC, Chahal HS: Computer-aided analysis of orbital volume: A novel technique. Ophthalmic Plast Reconstr Surg 29:1, 2013 18. Gribova MN, Pluijmers BI, Resnick CM, et al: Is there a difference in orbital volume between affected and unaffected sides in patients with unilateral craniofacial microsomia? J Oral Maxillofac Surg 76:2625, 2018 19. Lieger O, Schaub M, Taghizadeh E, B€ uchler P: How symmetrical are bony orbits in humans? J Oral Maxillofac Surg 77:118, 2019 20. P’An TH: Measurement of the Chinese orbit. J Anat 67:596, 1933 21. Mottini M, Wolf CA, Seyed Jafari SM, et al: Stereographic measurement of orbital volume, a digital reproducible evaluation method. Br J Ophthalmol 101:1431, 2017 22. Forbes G, Gehring DG, Gorman CA, et al: Volume measurements of normal orbital structures by computed tomographic analysis. AJR Am J Roentgenol 145:149, 1985
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