Intraocular and intraorbital compartment pressure changes following orbital bone grafting: a clinical and laboratory study

Visual loss is an uncommon but catastrophic complication after intraorbital bone grafting for the reconstruction of acute traumatic defects or long-standing enophthalmos. Increased intraocular or intraorbital compartment pressure may be pathogenic in this setting. A two-part study was designed to test the null hypothesis that intraocular and intraorbital compartment pressure values remain constant despite orbital volume reduction with graft material. Laboratory study: Intraocular and intraorbital compartment pressures were measured during sequential orbital volume reduction in New Zealand White rabbits that had been randomized to one of three groups: intact orbits (n = 10), acute orbital wall defects (n = 8), and chronic (3 months) orbital wall defects (n = 11). Intraocular pressure was significantly (p<0.05) elevated in all three groups of orbits undergoing orbital volume reduction compared with control, nonoperated orbits. Intraorbital compartment pressure values did not change significantly from control levels throughout the grafting sequence. Although no significant differences existed between groups in the maximum levels of intraocular pressure attained, the chronic group demonstrated a greater rate of rise and slower rate of decline. Clinical study: Using applanation tonometry, intraocular pressure was measured before and serially after orbital floor exploration and intraorbital placement of split calvarial bone grafts in 19 patients who presented with orbital-zygomatic complex fractures that required surgery. A separate group of 16 patients with orbital-zygomatic complex fractures that required exploration of the orbital floor but not bone grafting was used for comparison. A significant (p<0.05) elevation of intraocular pressure was observed immediately after bone grafting compared with nongrafted orbits, but values returned to normal within 30 minutes and remained stable through the third postoperative day. There were no cases of visual impairment in any patients in either group as the result of surgical treatment. These data indicate that orbital volume reduction with graft material results in significant, temporary elevation of intraocular pressure. No significant elevations of intraorbital compartment pressure were detected in the rabbit orbits. Data from this study may have direct relevance in defining guidelines for "tolerable" changes in orbital tissue and globe pressures after surgery.     

The longitudinal orbital CT projection: a versatile image for orbital assessment

The newer generation of CT scanners allows reconstruction of images in coronal, sagittal, and oblique planes from a single set of axial scans. These computer-generated images are described as reformatted. We have found an oblique image reformatted along the plane connecting the apex of the orbit and the center of the globe to be especially useful in assessing orbital disorders. We have named this image the longitudinal orbital projection. This projection allows direct visualization of the inferior rectus muscle and orbital floor in acute and old orbital trauma. With the image produced life size, direct measurements of enophthalmos and proptosis can be made preoperatively and postoperatively, thereby facilitating planning and follow-up. The projection is also useful in combination with other planes of reformation for the localization of tumors. The longitudinal orbital projection is now a routine part of the CT examination of the orbit in our institution. Whereas it already has become an invaluable aid in the diagnosis and follow-up of congenital and acquired orbital lesions, the longitudinal orbital projection promises to clarify the effects of trauma on the inferior rectus muscle and globe position.     

Presurgical planning and time efficiency in orthognathic surgery: the use of computer-assisted surgical simulation

Orthognathic procedures require extensive preoperative planning to maintain high fidelity of fabricated splints to anticipated skeletal and soft tissue changes. The authors report their use of the computer-assisted surgical simulation modeling system in preoperative planning and splint fabrication and the significant reduction in their overall preoperative time. Upper and lower bite registrations were sequentially created on a single bite jig with fast-drying bis-acryl material, which was then mounted to a fiducial-based facebow for facial skeleton indexing. Indexing data were submitted, and occlusal splints were fashioned and returned to the senior surgeon. Between September 2010 and January 2011, 10 consecutive patients were enrolled. Surgical indications included six Le Fort I advancements and four combined Le Fort I/bilateral sagittal split osteotomy cases. Average time for bite registration was 10 minutes 16 seconds ± 1 minute 33 seconds, with an additional 8 minutes 6 seconds ± 4 minutes 45 seconds needed for modeling and virtual splint confirmation. Six patients required cephalometric tracings, for an additional 12 minutes 50 seconds ± 1 minute 10 seconds. Average total session time for all patients was 26 minutes 14 seconds ± 9 minutes 13 seconds. Computer-assisted surgical simulation markedly decreased the time for preoperative splint planning and fabrication time, and had a positive impact on reimbursement rates for orthognathic surgery, as calculated on a per-hourly basis. The improved accuracy generated may lead to decreased operative times and improved outcomes. CLINICAL QUESTION/LEVEL OF EVIDENCE: Therapeutic, IV.     

Surgical management of the anophthalmic orbit, part 1: congenital

Congenital microphthalmos and anophthalmos are rare conditions in which orbital growth is deficient. Hypoplasia of the globe affects the bony orbit (micro-orbitism), the conjunctival sac, and eyelids (microblepharism), and it may be associated with abnormalities of the entire hemifacial skeleton (hemifacial microsomia). In the present article, the authors review a series of 19 patients with microphthalmos (nine had right-sided, one had bilateral, and nine had left-sided microphthalmos) who were treated in the Orbitopalpebral Unit at Hospital Foch over a period of 15 years (follow-up, 5 months to 18 years).Orbital expansion was achieved using spherical implants (n = 13), orbital osteotomies (n = 4), and orbital expanders (n = 2). Both expanders were removed within 6 months because of failure (one infection and one rupture). The current preferred method for orbital expansion is to use serial implants in the growing orbit and osteotomies in cases of late referral or insufficient orbital volume in the older child. The target proportions of the reconstructed orbit are not planned to mirror the healthy side exactly. The inferior orbital rim is kept higher to support the orbital implant, and the orbit is kept shallow to avoid a sunken appearance.Cranial bone grafts were used to augment deficient orbital contours; they were assisted by anterior transposition of the temporalis muscle (n = 5) when additional orbital volume was required. Conjunctival sac reconstruction was achieved by the use of serial conformers placed in the conjunctival sac during the neonatal period, followed by grafts of buccal mucosa and full-thickness skin maintained in place with a tarsorrhaphy for 3 to 6 months. Eyelid reconstruction using local flaps and skin grafts proved to be necessary in cases treated by osteotomy expansion, although reconstruction was not required after expansion using serial solid shapes. The results illustrate an evolution in approach and concepts of reconstruction of the microphthalmic orbit and emphasize the need for an integrated craniofacial approach for this complex deformity.     

Quantitative assessment of osseous, ocular, and periocular changes after hypertelorism surgery

The purpose of this study was to develop a methodology to quantify osseous, ocular, and periocular fat changes caused by correction of orbital hypertelorism to test the hypothesis that there is a quantitatively predictable relationship between the movement of the osseous orbit and that of the ocular globe. A retrospective review was performed of 10 patients who were status post unilateral or bilateral transcranial medial orbital translocation, for whom there were archival digital data for preoperative and postoperative (mean interval = 30 months) three-dimensional computed tomographic (CT) scans. In addition to standard demographic and surgical data, the clinical preoperative and postoperative interpupillary and intermedial canthal distances were recorded. By using a computer graphics workstation, the CT digital data were registered to four surgically unaltered anatomic fiducial points to allow longitudinal quantitative comparisons. The following three-dimensional measurements were made for each patient preoperatively and postoperatively: interdacryon and interocular centroid distances, and on a standard series of three horizontal and two vertical planes, the position of the medial and lateral orbital walls, and the thickness of the medial and lateral periorbital fat (20 orbits). CT digital distances were compared with similar clinical distances when possible. The age at operation ranged from 4.0 to 12.5 years (mean, 6.6 years). The reduction in interdacryon distance exceeded the reduction in intercentroid distance (mean interdacryon change = -5.3 mm versus mean intercentroid change = -2.7 mm). Although there was a strong correlation between the amount of reduction of the lateral orbital wall and intercentroid distances, there was only a moderate correlation between the reduction in the intercentroid distance and that of the medial orbital wall. Similarly, there was a moderate correlation between the decrease in thickness of the lateral periorbital fat and the reduction of intercentroid distance but not of the medial orbital fat. In conclusion, medial translocation of the orbit does not produce equivalent movement of the ocular globe; neither the intermedial canthal nor the interdacryon distance is a useful predictor of ocular centroid position; and if the goal of hypertelorism operation is reduction of interocular distance, then CT measurement of globe intercentroid distance is essential for outcome assessment.     

Reconstruction of internal orbital fractures with Vitallium mesh

Trauma to the face frequently results in internal orbital fractures that may produce large orbital defects involving multiple walls. Accurate anatomic reconstruction of the bony orbit is essential to maintain normal appearance and function of the eye following such injuries. Autogenous bone grafts do not always produce predictable long-term support of the globe. Displacement and varying amounts of bone-graft resorption can lead to enophthalmos. This study examines the use of Vitallium mesh in the acute reconstruction of internal orbital defects. Fifty-four patients with 66 orbits underwent reconstruction of internal orbital defects with Vitallium mesh. Associated fractures were anatomically reduced and rigidly fixed. Forty-six patients and 57 orbits had adequate follow-up for analysis of results. The average follow-up was 9 months, with 85 percent of the patients followed 6 months or longer. There were no postoperative orbital infections, and none of the Vitallium mesh required removal. Large internal orbital defects can be reconstructed using Vitallium mesh with good results and little risk of infection. Vitallium mesh appears to be well tolerated in spite of free communication with the sinuses. Stable reconstruction of the internal orbit can be achieved and predictable eye position maintained without donor-site morbidity.     

A stereotactic system for guiding complex craniofacial reconstruction.

A stereotactic system has been designed to address the problem of achieving symmetry in complex and extensive craniofacial defects. Preliminary testing suggests that such a system, which allows for the intraoperative application of preoperative CT planning, will be useful in guiding the reconstruction of congenital or acquired bony time, is being used to investigate the correlation of intraoperative globe position following enophthalmos correction with long-term outcome, particularly as it relates to the size and location of the orbital defect, and the timing of the procedure.     

Orbital volume measurements in enophthalmos using three-dimensional CT imaging

The purpose of this study was to investigate enophthalmos by measuring the volume of various orbital structures using off-line computer techniques on images generated by a CT scanner. Eleven patients with enophthalmos had CT scans of the orbits consisting of 30 to 40 adjacent 1.5-mm slices. The data from the scans were analyzed on a Nova 830 stand-alone computer system using software programs that allowed measurement of total bony orbital volume, total soft-tissue volume, globe volume, orbital fat volume, neuromuscular tissue volume, and apex-to-globe distance in the horizontal plane. These data were analyzed comparing the volumes in the normal eye with the volumes in the enophthalmic eye in each patient. The analysis demonstrated a statistically significant increase in bony orbital volume in the enophthalmic eye, but the total soft-tissue volume, fat volume, neuromuscular tissue volume, and globe volume were the same as in the normal eye. The apex-to-globe distance, a measure of the degree of enophthalmos, was less in the enophthalmic eye than in the normal eye. These results suggest that in the majority of patients, the cause of posttraumatic enophthalmos is increased bony orbital volume rather than by soft-tissue loss or fat necrosis. (Several patients showed no volume discrepancies, and it is likely that cicatricial contracture is responsible for the enophthalmos in these cases.) This study suggests that the objective of surgery for correction of enophthalmos in patients with a volume discrepancy should be to decrease the volume of the bony orbit and to increase the anterior projection of the globe.     

3D-Assisted Quantitative Assessment of Orbital Volume Using an Open-Source Software Platform in a Taiwanese Population

Orbital volume evaluation is an important part of pre-operative assessments in orbital trauma and congenital deformity patients. The availability of the affordable, open-source software, OsiriX, as a tool for preoperative planning increased the popularity of radiological assessments by the surgeon. A volume calculation method based on 3D volume rendering-assisted region-of-interest computation was used to determine the normal orbital volume in Taiwanese patients after reorientation to the Frankfurt plane. Method one utilized 3D points for intuitive orbital rim outlining. The mean normal orbital volume for left and right orbits was 24.3±1.51 ml and 24.7±1.17 ml in male and 21.0±1.21 ml and 21.1±1.30 ml in female subjects. Another method (method two) based on the bilateral orbital lateral rim was also used to calculate orbital volume and compared with method one. The mean normal orbital volume for left and right orbits was 19.0±1.68 ml and 19.1±1.45 ml in male and 16.0±1.01 ml and 16.1±0.92 ml in female subjects. The inter-rater reliability and intra-rater measurement accuracy between users for both methods was found to be acceptable for orbital volume calculations. 3D-assisted quantification of orbital volume is a feasible technique for orbital volume assessment. The normal orbital volume can be used as controls in cases of unilateral orbital reconstruction with a mean size discrepancy of less than 3.1±2.03% in females and 2.7±1.32% in males. The OsiriX software can be used reliably by the individual surgeon as a comprehensive preoperative planning and imaging tool for orbital volume measurement and computed tomography reorientation.     

Treatment of exophthalmos

Current procedures for Graves' exophthalmos fail to achieve complete correction. The standard orbital decompressions were therefore modified to maximize the degree of volumetric increase behind the axis of the globe. In 15 orbits, the preoperative exophthalmos averaged 9.5 mm, whereas the postoperative exophthalmos was 4.1 mm. Postoperative CT study demonstrated that the remaining posterior orbital wall, combined with the persistently increased intraocular muscle volume, blocked retrodisplacement of the globe, despite adequate total volumetric increase. The increased muscle volume varied from 2 to 5 cc. Despite this residual exophthalmos, the modified four-wall expansion provides excellent aesthetic results with visual improvement and resolution of chemosis and exposure keratitis.     

Use of virtual surgery and stereolithography-guided osteotomy for mandibular reconstruction with the free fibula

Fibular osteotomy remains a challenging aspect of mandibular microsurgical reconstruction, dependent largely on surgeon experience, intraoperative judgment, and technical speed. Virtual surgical planning and stereolithographic modeling is a relatively new technique that can allow for reduction in the learning curve associated with neomandible contouring, enhanced levels of accuracy, and acceleration of a time-consuming intraoperative step. The authors present a video (narrated and edited from planning sessions and intraoperative use of technique to illustrate the technology) and describe their favorable results. Five patients underwent composite resection of the mandible and free fibula osteocutaneous reconstruction over a 6-month period (December of 2009 to June of 2010) at a single institution using a virtual planning session and stereolithographic modeling. Outcomes assessed included technical accuracy, aesthetic contour, and functional outcomes. All patients achieved negative margins with cutting guide-directed resection. Use of this technique eliminated the need for intraoperative measurement and yielded fibular segments with excellent apposition and faithful duplication of the preoperative plan. Minimal adjustments were needed for inset. Flap survival was 100 percent. All patients have maintained preoperative occlusion and a symmetric mandibular contour on Panorex study, three-dimensional computed tomography, and clinical examination. Accuracy of the reconstructed contour was confirmed using computed tomographic image overlay. This virtual surgical planning technique combined with stereolithographic model-guided osteotomy is the mainstay of the authors' approach to fibular osteotomy when dealing with patients requiring mandibular reconstruction. The authors feel this technology facilitates realization of technical accuracy, aesthetic contour, and functional outcomes and may be particularly useful if free fibular mandibular reconstruction is performed less frequently. CLINICAL QUESTION/LEVEL OF EVIDENCE: Therapeutic, IV.     

Blepharo-canthal deformities in patients following craniofacial surgery

Functional problems and deformities of the eyes have become a major concern in the surgical treatment of ortital hypertelorism and craniofacial dysostosis, as experience with skeletal relocation for these disorders has been gained. Comprehensive preoperative and postoperative study and measurements of the bony orbits, the globes, the lids, the canthi, and the nose are necessary for the evaluation of present techniques and the design of alternative procedures. Some of the deformities of the blepharo-canthal complex are part of the congenital malformation. Other distortions, seen only postoperatively, are secondary to specific surgical maneuvers. Awareness of these primary and secondary factors has led to better soft tissue reconstruction at the time of the bony orbital translocations or the craniofacial disjunction. We describe the techniques which we have found especially useful in avoiding and correcting these postoperative blepharocanthal deformities.     

Surgical management of the anophthalmic orbit, part 2: post-tumoral

Ablative surgery for tumors of the globe and its adnexal structures is frequently the cause of major orbitofacial deformity. Radiotherapy compounds the problem because it suppresses skeletal growth in the growing patient and induces a contraction of the remaining soft tissues in the orbit. Goals for reconstruction in these patients include the restoration of orbital structures to allow the fitting of an ocular prosthesis and the correction of distorted orbitofacial relationships. The authors present a series of 53 patients (mean age, 29 years; 28 male) who were treated over the past 18 years by composite reconstruction of the post-tumoral anophthalmic orbit. The follow-up ranged from 5 months to 18 years (mean, 7.75 years). Four patients were treated primarily (immediate reconstruction after tumor ablation), and 49 were treated secondarily (mean oncological follow-up since ablative surgery, 14.8 years). Twenty-eight patients underwent orbital enucleation (including three bilateral cases), 23 underwent orbital exenteration, and two underwent evisceration. Forty-two patients received radiotherapy, including 20 enucleation patients, 15 exenteration patients, and seven others in whom details of primary therapy were incomplete. A staged reconstruction was undertaken in each case; it considered, in turn, the bony orbital volume (orbital remodeling and cranial bone grafts), orbital contents (implant, temporalis muscle transposition, cranial bone grafts, and dermafat grafts), conjunctival sac (mucosal and skin grafts), ocular prosthesis, eyelids (local flaps and skin grafts), and additional procedures to restore orbitofacial symmetry. The authors conclude that the long-term results of post-tumoral orbital reconstruction are favorable, and they particularly recommend the use of autogenous tissues in irradiated orbits.     

Quantitative Assessment of Orbital Implant Position – A Proof of Concept

Introduction

In orbital reconstruction, the optimal location of a predefined implant can be planned preoperatively. Surgical results can be assessed intraoperatively or postoperatively. A novel method for quantifying orbital implant position is introduced. The method measures predictability of implant placement: transformation parameters between planned and resulting implant position are quantified.

Methods

The method was tested on 3 human specimen heads. Computed Tomography scans were acquired at baseline with intact orbits (t0), after creation of the defect (t1) and postoperatively after reconstruction of the defect using a preformed implant (t2). Prior to reconstruction, the optimal implant position was planned on the t0 and t1 scans. Postoperatively, the planned and realized implant position were compared. The t0 and t2 scans were fused using iPlan software and the resulting implant was segmented in the fused t2 scan. An implant reference frame was created (Orbital Implant Positioning Frame); the planned implant was transformed to the reference position using an Iterative Closest Point approach. The segmentation of the resulting implant was also registered on the reference position, yielding rotational (pitch, yaw, roll) as well as translational parameters of implant position.

Results

Measurement with the Orbital Implant Positioning Frame proved feasible on all three specimen. The positional outcome provided more thorough and accurate insight in resulting implant position than could be gathered from distance measurements alone. Observer-related errors were abolished from the process, since the method is largely automatic.

Conclusion

A novel method of quantifying surgical outcome in orbital reconstructive surgery was presented. The presented Orbital Implant Positioning Frame assessed all parameters involved in implant displacement. The method proved to be viable on three human specimen heads. Clinically, the method could provide direct feedback intraoperatively and could improve postoperative evaluation of orbital reconstructive surgery.     

Improving aesthetic outcomes after alloplastic chin augmentation

A novel approach to increase chin projection with alloplastic material is presented. Key aspects of the technique include the consideration of anthropometric normal values in preoperative assessment and planning, a submental approach with wide subperiosteal exposure of the area to be augmented, the use of two-piece porous polyethylene implants for augmentation, and screw fixation of the implant to the mandible. Screw fixation improves the predictability and precision of reconstruction by preventing implant displacement, by obliterating gaps between the implant and the facial skeleton, and by facilitating final implant contouring. In a series of 46 patients (24 primary and 22 secondary) operated on over a 6-year period, this approach allowed anatomically correct, stable chin contours to be created. Iatrogenic problems with macrogenia, mentalis dysfunction, and soft-tissue distortion resulting from implant migration and capsular contracture have been avoided. There have been no infections. Two patients who had had multiple previous chin operations requested revisional surgery to refine contour.     

The direct effect of intraorbital pressure on orbital growth in the anophthalmic piglet.

Tissue expanders placed within the orbit can have a positive effect on orbital and ipsilateral midfacial growth. To date, there is no precise method for controlling and monitoring expansion to induce normal growth in the developing facial skeleton. The present study was undertaken to determine the optimal physiologic pressure required to stimulate normal orbital growth and to determine whether above-normal growth could be achieved with higher intraorbital pressures. Using a neonatal swine model, an accurate method of monitoring intraorbital pressure, precisely controlling intraorbital expansion, and achieving normal orbital growth was explored. Sixteen male, 3-week-old Yorkshire piglets were randomly divided into three surgical groups. In each group, the left orbit was the experimental side, and the contralateral right orbit served as an untreated control. Group 1 (n = 6) underwent enucleation only. Group 2 (n = 5) underwent enucleation and orbital expansion at a near-normal physiologic pressure of 20 mmHg. Group 3 (n = 5) underwent enucleation and orbital expansion at a supernormal pressure of 60 mmHg. Spherical tissue expanders (10 cc) with a separate injection port were utilized as the orbital expanders. Pressure was monitored by an electronic manometer that was calibrated daily. Morphology of the orbits was documented by photography, the dimensions of the orbits were quantitated by three-dimensional mechanical digitization, and orbital volumes were calculated. In the unexpanded, anophthalmic control group, a significant reduction in radial growth after evisceration was seen. In group 2, the orbit stimulated with a consistent pressure of 20 mmHg, just above the physiologic normal pressure of 17 mmHg, showed an increase in radial dimension of 8 percent compared with the unoperated side. In the high-pressure group of 60 mmHg, an increase of 16 percent in the radius was observed over the 4-week period. This led to a corresponding increase in orbital volumes with increased pressure. Utilizing a paired t test, these differences in the radial and volumetric growth of the orbit were statistically significant (p < 0.005). The results obtained demonstrated a direct relationship between intraorbital pressure and the growth of the bony orbit in the radial dimension. On the basis of this study, we concluded that orbital expansion maintained at normal physiologic pressure can stimulate normal orbital growth in the neonatal facial skeleton. In addition, application of above-normal pressures for expansion can induce accelerated orbital growth.     

Upper and lower eyelid reconstruction

Reconstruction of the eyelids can range from simple repair to the integration of multiple complex procedures. Knowledge of eyelid anatomy, adequate preoperative planning, and meticulous surgical technique will optimize the anatomical and functional result. The purpose of this article is to review the relevant anatomy for eyelid reconstruction, to simplify defect analysis and preoperative planning, and to provide options for reconstruction of this complex area.     

A computational/experimental platform for investigating three-dimensional puzzle solving of comminuted articular fractures

Reconstructing highly comminuted articular fractures poses a difficult surgical challenge, akin to solving a complicated three-dimensional (3D) puzzle. Preoperative planning using computed tomography (CT) is critically important, given the desirability of less invasive surgical approaches. The goal of this work is to advance 3D puzzle-solving methods towards use as a preoperative tool for reconstructing these complex fractures. A methodology for generating typical fragmentation/dispersal patterns was developed. Five identical replicas of human distal tibia anatomy were machined from blocks of high-density polyetherurethane foam (bone fragmentation surrogate), and were fractured using an instrumented drop tower. Pre- and post-fracture geometries were obtained using laser scans and CT. A semi-automatic virtual reconstruction computer program aligned fragment native (non-fracture) surfaces to a pre-fracture template. The tibiae were precisely reconstructed with alignment accuracies ranging from 0.03 to 0.4 mm. This novel technology has the potential to significantly enhance surgical techniques for reconstructing comminuted intra-articular fractures, as illustrated for a representative clinical case.     

Full-thickeness anterior blepharotomy and transpalpebral fat decompression in Graves' orbitopathy

A chief morbidity of Graves eye disease is eyelid retraction and exophthalmus. Transpalpebral orbital fat removal accomplished with full thickness anterior blepharotomy was performed in 4 patients (5 orbits). Preoperative and postoperative ocular exposure symptoms, visual acuity, upper eyelid retraction and proptosis were evaluated. In all 5 operated orbits preoperative symptoms resolved; good results were achieved from the functional and cosmetic point of view. Full-thickness anterior blepharotomy combined with fat decompression is a safe and effective surgery for patients with upper eyelid retraction and exophthalmus due to enlarged orbital fat compartment.