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.     

Anatomicohistologic study of the retaining ligaments of the face and use in face lift: retaining ligament correction and SMAS plication

Plastic surgeons have sought to improve nasolabial folds, jowls, jaw lines, and cervical contour with face-lifting procedures that are abundant in the literature. The retaining ligaments of the face support facial soft tissue in normal anatomic position, resisting gravitational change. As this ligamentous system attenuates, facial fat descends into the plane between the superficial and deep facial fascia, and the stigmata of facial age develop. In this study, surgical correction of the retaining ligaments and plication of the superficial musculoaponeurotic system (SMAS) to reposition the structures that have descended with gravitation are discussed. The anatomy of the facial retaining ligaments was studied in 22 half-faces of 11 fresh cadavers, and the localization, extension, and width of the ligaments were examined macroscopically and histologically. Surgical correction of the retaining ligaments and plication of the SMAS have been accomplished in 27 face-lift patients with this anatomicohistologic study taken into consideration. There was hematoma in one patient at the cheek region and a permanent dimple caused by postoperative edema in two patients, with a localization of one zygomatic and two parotidomasseteric ligaments. In one patient, hypesthesia in the mandibular nerve region was seen, which remitted at 14 weeks. There were no other complications, and with a follow-up of 24 months, excellent aesthetic results and a high level of patient satisfaction were encountered.     

Orbital floor and infraorbital rim reconstruction after total maxillectomy using a vascularized calvarial bone flap.

A number of techniques have been introduced to support the orbital floor after maxillectomy without orbital exenteration. These methods include skin graft or muscular sling, but they have resulted in severe complications, such as enophthalmos, global ptosis, diplopia, and facial deformity. Currently, advanced microvascular reconstruction using bone and soft tissue is performed by many surgeons. This usually results in the filling of the postmaxillectomy defect, but the lack of support for the orbital rim and floor by the bone flap may still cause the complications mentioned above. Vascularized calvarial bone flap was chosen in this study for reconstruction of the orbital floor and infraorbital rim to function as a buttress, to reconstruct recipient sites of poor vascular bed after radiation therapy, and to withstand further postoperative radiation. By providing a solid floor and rim, these complications can be prevented with satisfactory function and aesthetically acceptable results. From September of 1995 to July of 1998, we performed vascularized bone flap for the reconstruction of the orbital floor and infraorbital rim in four cases after total maxillectomy involving the orbital floor. With a follow-up period from 19 to 35 months (mean, 27 months), we obtained significant improvement of functional and aesthetically acceptable results without global ptosis, enophthalmos, diplopia, or severe facial contour deformity.     

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 computational study of the passive mechanisms of eye restraint during head impact trauma

A finite element model of the eye and the orbit was used to examine the hypothesis that the orbital fat provides an important mechanism of eye stability during head trauma. The model includes the globe, the orbital fat, the extra-ocular muscles, and the optic nerve. MRI images of an adult human orbit were used to generate an idealized geometry of the orbital space. The globe was approximated as a sphere 12 mm in radius. The optic nerve and the sclera were represented as thin shells, whereas the vitreous and the orbital fat were represented as nearly incompressible solids of low stiffness. The orbital bone was modelled as a rigid shell. Frontal head impact resulting from a fall onto a hard floor was simulated by prescribing to the orbital bone a triangular acceleration pulse of 200 g (1962 m/s(2)) peak for a duration of 4.5 ms. The results show that the fat provides the crucial passive mechanism of eye restraint. The mechanism is a consequence of the fact that the fat is incompressible and that its motion is restricted by the rigidity of the orbital walls. Thus, the acceleration loads of short duration cannot generate significant distortion of the fat. In contrast, the passive muscles provide little support to the globe. When the connection between the orbital fat and the eye is absent the eye is held mainly by the optic nerve. We discuss the possible role that this loss of contact may have in some cases of the evulsion of the eye and the optic nerve.     

Semiquantitative correction of posttraumatic enophthalmos with sliced cartilage grafts

A simple surgical technique for correcting posttraumatic enophthalmos is described. The steps are as follows: (1) a plaster mold is obtained of the patient's face, (2) wax is added to the enophthalmic eye of the plaster mold until it becomes symmetrical, (3) the quantity of wax is measured, and (4) the same amount of sliced costal cartilage is implanted beneath the periosteum of the extended orbital wall behind the vertical axis of the globe. Using this technique, we have successfully treated six patients with traumatic orbital floor defects without complication. This approach is useful for decreasing the orbital volume using a semiquantitative procedure to estimate the amount of graft material required. In this respect, costal cartilage demonstrates a marked advantage, with stability and cosmetic appearance verified over 12 months of follow-up.     

Computed tomography in the diagnosis of soft tissue changes in patients with chronic osteomyelitis of the femur

Computed tomography was used to study soft tissues of the femur in 78 patients with its chronic recurrent osteomyelitis and the studied parameters were estimated. The fibrous changes were found to be more pronounced in posttraumatic osteomyelitis; the thickening of the subcutaneous fat and its atrophy were equally marked; the density gradients between the intact muscle, infiltrated muscle tissue, and purulent leakage were calculated.     

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.     

Rigid fixation of internal orbital fractures

When large portions of the internal orbit are destroyed (two to four walls), standard bone-grafting techniques for immediate and late orbital reconstruction may not yield predictable eye position. Critical bone support is most often deficient inferomedially. CT analysis of orbital volume in cases where eye position was unsatisfactory reveals that displacement of bone grafts is one mechanism of the unsatisfactory result. Other mechanisms include undercorrection and bone-graft resorption. In order to minimize postoperative bone-graft displacement, titanium implants were used to span large defects in the internal orbit to provide a platform for bone-graft support. Twenty-six implants were placed in immediate and 12 were placed in late orbital reconstructions. More reliable bone-graft position resulted. Two late infections have occurred resulting in implant removal in a 3-year period.     

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.     

Severe traumatic oculo-orbital displacement. Diagnosis and secondary treatment.

We have treated 12 patients with severe oculo-orbital trauma during the past 3 years. The structural problems, produced by disruption or displacement of the orbital cone, were treated effectively (and, on occasion, preferentially) with onlay bone grafts. For an effective correction, we advise radical mobilization of the soft tissue and simultaneous correction on the ocular adnexal deformities. Ocular muscle problems are produced by direct injury to the extraocular muscles, or oculomotor nerve, and were possible these should be corrected early. The structural damage to the eye and orbit falls into certain patterns, related to weak points about the orbit. These have been described.     

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.     

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.     

Clinical and X-ray assessment of different modes for correcting orbital bottom defects in posttraumatic deformities of the middle one-third of the facial skeleton

The paper describes the evolution and consequences of different modes of eliminating orbital bottom defects and deformities that develop in posttraumatic deformities due to bone fractures of the facial mid-skeleton. Spiral computed tomography of this portion of the facial skeleton has demonstrated that the optimum results of restoration of the orbital bottom and those of elimination of eyeball displacement give the use of osteoplasty with a split parietal bone graft.     

Incorporation of titanium mesh in orbital and midface reconstruction

Several authors have demonstrated the safety and effectiveness of titanium in orbital reconstruction. One question posed by clinicians is what happens to large pieces of titanium in communication with the paranasal sinuses or nasal-oral-pharyngeal area. This question becomes increasingly relevant as titanium is used to reconstruct extensive defects for which the destruction of bony architecture requires the placement of mesh in proximity to these areas. The objective of this study was to examine the gross and histologic soft-tissue response to large segments of titanium mesh in the setting of orbital and midface reconstruction, particularly when exposed to the nasal-oral-pharyngeal area and paranasal sinuses. In this study, large segments of titanium mesh were used in eight patients to reconstruct orbital and midface defects, with direct communication between the mesh and nasal-oral-pharyngeal area and paranasal sinuses. Four patients had suffered self-inflicted gunshot wounds; as a result, much of their midface was missing, including the inferior and medial orbital floor, maxilla, nose, naso-orbital-ethmoid complex, and hard palate. Extensive sheets of titanium mesh were used to reconstruct their medial and inferior orbital walls, nasal bridge, and maxilla. In the fifth patient, titanium mesh was used to reconstruct the maxilla after resection of a squamous cell carcinoma of the nasolacrimal duct. In the sixth and seventh patients, mesh was used to reconstruct the nasal bridge after severely comminuted nasal fractures resulted in the loss of bone and mucosa. Finally, the eighth patient had titanium mesh used to replace cocaine-induced bone loss involving the left medial orbital floor and wall and part of the maxilla. On gross examination by either endoscopy or direct inspection, all eight patients had rapid soft-tissue incorporation of the titanium mesh. Initial examination typically revealed budding of soft tissue through mesh interstices, followed by progressive incorporation. One patient's mesh was covered in only 15 days. Two patients underwent biopsies of this newly formed soft tissue. One had biopsies performed at 3, 15, and 31 months after the original operation. Biopsy examination at 3 months revealed incorporation of the titanium with fibrous soft tissue covered by ciliated respiratory epithelium, goblet cells, and squamous epithelium with metaplasia. In addition, the dense, acute inflammation present at 3 months evolved into mild, chronic inflammation at 31 months. The second patient had a single biopsy 4 months after secondary orbital reconstruction for delayed enophthalmos. Biopsy examination revealed a fibrous soft-tissue sheath lined by squamous epithelium with metaplasia. Again, mild chronic inflammation was present within the soft tissue. This study provides evidence of titanium's compatibility with soft tissue. The mesh underwent progressive incorporation with soft tissue that was then resurfaced by indigenous cells, including respiratory epithelia and goblet cells. This phenomenon occurred despite communication with the nasal-oral-pharyngeal area and paranasal sinuses.     

Reconstruction of orbital floor fracture using solvent-preserved bone graft

The orbital floor is one of the most frequently damaged parts of the maxillofacial skeleton during facial trauma. Unfavorable aesthetic and functional outcomes are frequent when it is treated inadequately. The treatment consists of spanning the floor defect with a material that can provide structural support and restore the orbital volume. This material should also be biocompatible with the surrounding tissues and easily reshaped to fit the orbital floor. Although various autografts or synthetic materials have been used, there is still no consensus on the ideal reconstruction method of orbital floor defects. This study evaluated the applicability of solvent-preserved cadaveric cranial bone graft and its preliminary results in the reconstruction of the orbital floor fractures. Twenty-five orbital floor fractures of 21 patients who underwent surgical repair with cadaveric bone graft during a 2-year period were included in this study. Pure blowout fractures were determined in nine patients, whereas 12 patients had other accompanying maxillofacial fractures. Of the 21 patients, 14 had clinically evident diplopia (66.7 percent), 12 of them had enophthalmos (57.1 percent), and two of them had gaze restriction preoperatively. Reconstruction of the floor of the orbit was performed following either the subciliary or the transconjunctival approach. A cranial allograft was placed over the defect after sufficient exposure. The mean follow-up period was 9 months. Postoperative diplopia, enophthalmos, eye motility, cosmetic appearance, and complications were documented. None of the patients had any evidence of diplopia, limited eye movement, inflammatory reactions in soft tissues, infection, or graft extrusion in the postoperative period. Providing sufficient orbital volume, no graft resorption was detected in computed tomography scan controls. None of the implants required removal for any reason. Enophthalmos was seen in one patient, and temporary scleral show lasting up to 3 to 6 weeks was detected in another three patients. Satisfactory cosmetic results were obtained in all patients. This study showed that solvent-preserved bone, which is a nonsynthetic, human-originated, processed bioimplant, can be safely used in orbital floor repair and can be considered as another reliable treatment alternative.     

A technique for the combination of clearing, staining, and injecting small mammals.

A combined method for clearing soft tissues, staining cartilage and bone, and injecting the vascular system of small mammals was developed using Mus musculus (house mouse). Mammalian muscle tissue remains milky or even opaque after "clearing" by previous techniques due to the relatively high content of intramuscular fat. A method employing chloroform-ethanol successfully renders soft tissues of mammalian specimens translucent without damaging or bleeding color from the latex injected in the circulatory system. Resulting specimens yield an excellent view of the skeletal system and the injected vascular system without obstruction by opaque tissues or disruption by physical removal of connective tissue.     

Deformation and stress distribution of the human foot after plantar ligaments release: A cadaveric study and finite element analysis

The majority of foot deformities are related to arch collapse or instability, especially the longitudinal arch. Although the relationship between the plantar fascia and arch height has been previously investigated, the stress distribution remains unclear. The aim of this study was to explore the role of the plantar ligaments in foot arch biomechanics. We constructed a geometrical detailed three-dimensional (3-D) finite element (FE) model of the human foot and ankle from computer tomography images. The model comprised the majority of joints in the foot as well as bone segments, major ligaments, and plantar soft tissue. Release of the plantar fascia and other ligaments was simulated to evaluate the corresponding biomechanical effects on load distribution of the bony and ligamentous structures. These intrinsic ligaments of the foot arch were sectioned to simulate different pathologic situations of injury to the plantar ligaments, and to explore bone segment displacement and stress distribution. The validity of the 3-D FE model was verified by comparing results with experimentally measured data via the displacement and von Mise stress of each bone segment. Plantar fascia release decreased arch height, but did not cause total collapse of the foot arch. The longitudinal foot arch was lost when all the four major plantar ligaments were sectioned simultaneously. Plantar fascia release was compromised by increased strain applied to the plantar ligaments and intensified stress in the midfoot and metatarsal bones. Load redistribution among the centralized metatarsal bones and focal stress relief at the calcaneal insertion were predicted. The 3-D FE model indicated that plantar fascia release may provide relief of focal stress and associated heel pain. However, these operative procedures may pose a risk to arch stability and clinically may produce dorsolateral midfoot pain. The initial strategy for treating plantar fasciitis should be non-operative.     

Computer-assisted secondary reconstruction of unilateral posttraumatic orbital deformity

Until now, computer-assisted surgery has not been practiced as part of the surgical routine of posttraumatic orbital reconstruction. The purpose of this study was to investigate the use of a navigation system for computer-assisted preoperative planning with virtual reconstruction to obtain symmetry of the orbits and intraoperative control of virtual contours in comparison with the clinically achieved surgical results. A further objective of the computer-assisted orbital analysis was to use an ideal measurement for the two-dimensional and three-dimensional changes following orbital reconstruction and to check the equality of the postoperative values for the affected orbits in comparison with those of the unaffected sides. Patients with unilateral posttraumatic orbital defects (n = 18) underwent computer-assisted surgery and preoperative planning using a spiral computed tomography database. Surgical procedures were preplanned with virtual correction by mirroring an individually defined three-dimensional segment from the unaffected side onto the deformed side, creating an ideal unilateral reconstruction. These computer-models were intraoperatively used as virtual templates to navigate the preplanned contours and the globe projection using the Stryker-Leibinger navigation system. Individual noninvasive registration with an overall inaccuracy of approximately 1 mm was achieved by using a maxillary occlusal splint with four markers. The mirroring of the unaffected side allowed an ideal virtual reconstruction. A mean decrease in enlarged orbital volume of 4.0 (SD +/- 1.9) cm was achieved, as was a mean increase in the sagittal globe projection of 5.88 (SD +/- 2.98) mm. With a paired Student test, the decrease between the preoperative and postoperative differences of the affected and unaffected sides was proved significant for orbital volume, globe projection, and computed tomography-based Hertel scale changes (p < 0.01). In 15 of 18 cases, simultaneous malar bone advancement resulted primarily in an additional increase in orbital volume before intraorbital augmentation with calvarial split-bone grafts could be performed. Intraorbital bony augmentation included one (n = 1), two (n = 7), three (n = 8), and all four (n = 2) orbital walls. Computer-assisted preoperative planning enables the surgeon to predict reconstructive surgical steps before the operation. Highly vulnerable structures such as the optic nerve can be detected and avoided intraoperatively, and virtually preplanned bone graft positions and/or orbital frame contours can be checked. Computer-assisted preoperative planning and surgery thus advance the difficult surgical field of orbital reconstruction, particularly through a greater exploitation of radiologic information without additional radiation to the patient.