Clinical signs of orbital wall fractures as a function of anatomic location

OBJECTIVE

The objective of this study was to see whether clinical signs of medial orbital wall fractures distinguished these fractures from fractures of the lateral orbital wall and the orbital floor.

STUDY DESIGN

The orbital fractures of 424 patients were analyzed. The patients were divided into 2 groups: (1) patients with orbital fractures with a medial orbital wall component and (2) patients with orbital fractures without a medial orbital wall component.

RESULTS

Orbital fractures with involvement of the medial orbital wall showed a significantly higher incidence (P =.001) of diplopia and exophthalmos (P =.039) than fractures without involvement of the medial wall.

CONCLUSION

Posttraumatic orbital clinical signs are associated with a higher incidence of medial orbital wall component fracture. Apparent lack of involvement of the medial orbital wall should not be an exclusion criterion for a surgical intervention when clinical orbital signs exist.

Normal anatomy on tomograms for dental implants

Some dentists may be unfamiliar with reading conventional tomograms made of dental implant sites. The purpose of this article is to aid dentists in identifying normal anatomical landmarks on cross-sectional slices and to correlate them to sagittal slices.

Accuracy of drilling guides for transfer from three-dimensional CT-based planning to placement of zygoma implants in human cadavers

The accuracy of surgical drilling guides was assessed for placement of zygoma implants. Six zygoma fixtures of length 45 mm (Nobel Biocare, Göteborg, Sweden) were placed in three formalin-fixed human cadavers using surgical drilling guides. The fabrication of these custom-made drilling guides was based on three-dimensional computerized tomography (3D-CT) data for the maxillary-zygomatic complex. The installation of the implants was simulated preoperatively using an adopted 3D-CT planning system. In addition, anatomical measurements of the zygomatic bone were performed on the 3D images. The preoperative CT images were then matched with postoperative ones in order to assess the deviation between the planned and installed implants. The angle between the planned and actually placed implants was < 3 degrees in four out of six cases. The largest deviation found at the exit point of one of the six implants was 2.7 mm. The present study showed that the use of surgical drilling guides should be encouraged for zygoma implant placement because of the lengths of the implants involved and the anatomical intricacies of the region.

Human masticatory muscle volume and zygomatico-mandibular form in adults with mandibular prognathism

Although several investigators have reported associations between masticatory muscles and skeletal craniofacial form, there is no agreement on the association. We tested the hypothesis that masticatory muscle volume correlates with the size and form of the adjacent local skeletal sites. For this purpose, we investigated the morphological association of the cross-sectional area and volume of temporal and masseter muscles with zygomatico-mandibular skeletal structures using computerized tomography (CT) in 25 male adults with mandibular prognathism. Muscle variables significantly correlated with widths of the bizygomatic arch and temporal fossa but not with the cranium width. Masseter volume significantly correlated with cross-sectional areas of the zygomatic arch and mandibular ramus. Masseter orientation was almost perpendicular to the zygomatic arch and mandibular antegonial region. The zygomatic arch angle significantly correlated with the antegonial angle. The results of the study suggest that the masticatory muscles exert influence on the adjacent local skeletal sites.

[Surgical features on intraoral approach for the management of isolated zygomatic arch fractures]

The Authors report on their experience of 18 patients with isolated fractures of the zygomatic arch who were treated via intraoral approach. The procedures were performed between the 2nd and 8th post-trauma day and the results obtained were evaluated via post-operative CT scan and periodic follow-up visits for six months. In describing the surgical technique, the Authors recommend that the fracture be reduced with the patient's mouth open, in order to overcome the anatomical obstacle constituted by the coronoid process of the mandible and avoid, as far as possible, external approaches and osteosynthesis with screws or miniplates, which often give rise to unaesthetic results and localized pain. In conclusion, this approach is seen to be the method of choice in the treatment of isolated zygomatic arch fractures in that it is simple, effective and substantially free from complications.

A histomorphometric analysis of heavily loaded and non-loaded implants

PURPOSE

To investigate the bone tissue response at the interface of loaded and non-loaded implants used in an orthopedic anchorage system after a continuous, non-axial force application of 5 N over 2 months.

MATERIALS AND METHODS

Twenty-nine Brånemark System implants were placed in the zygomatic arches of 5 dogs. After a healing period of 8 weeks, 20 implants (4 in each dog) were loaded during 8 weeks with a large non-axial orthopedic force application of 5 N. This force was directed between the implants and a maxillary splint to move the maxilla forward. Nine implants were not loaded during this period. At the termination of the experiment, all 29 implants were retrieved for radiographic as well as for histologic analysis. Computer-based histomorphometric quantifications were performed via light microscopy and computer software. Bone-metal contact (BMC), bone surface area (BSA) inside the threads, and the bone mirror area (BMA) of the implants were measured. Statistical comparisons between the loaded and non-loaded implants were carried out. In the group of loaded implants a 2-factor analysis of variance was used.

RESULTS

There were no statistically significant differences found in BMC, BSA, and BMA between the loaded and non-loaded implants, both for all the threads and for only the cervical region of the implants. Nor were there statistically significant differences between the non-pressure and pressure sides or for different lengths of the loaded implants.

DISCUSSION

The loaded implants maintained the osseointegration achieved during the 8-week healing period.

CONCLUSIONS

The results of this study indicate that titanium implants can be used as anchorage for orthopedic force application systems.

Traumatic chronic TMJ dislocation: report of an unusual case and discussion of management

Dislocation of the temporomandibular joint (TMJ) is most often spontaneous, but it can be associated with direct or indirect head and neck trauma. The disorder may be treated in general by simple closed techniques, if managed acutely. If the dislocation becomes chronic, however, open reduction is usually required. The article discusses various methods for an open surgical approach described in the literature. A case of a prolonged TMJ dislocation is presented, involving a severe bilateral mandibular dislocation with the condyles displaced into the infratemporal fossa and the lateral poles of the condyles articulating on the inner aspect of the zygomatic arch. An open approach, involving masseter, temporalis, and the medial pterygoid muscles, was utilized, followed by the use of scissors mouth props, Erich arch bars, and postoperative elastic traction.

[Total resection of the zygomatic arch in the growth period: experimental study in rats]

The results obtained after total unilateral resection of the zygomatic arch in Wistar rats were evaluated by means of cephalometric measurements. The resection of the right zygomatic arch was carried out in one-month-old rats, and the animals were sacrificed two months later. The skull and hemimandibles were submitted to axial and lateral radiographic incidences. Based on the obtained radiographs, measurements were carried out by means of a computer system, which compared both sides of the specimens. The obtained values were submitted to statistical analysis. There was significant difference as to the extent of the temporal fossa, but there was no significant difference as to other measures of the maxilla. There was significant difference between both sides regarding the height of the body and the length of the base of the mandible.

Bilateral coronoid hyperplasia in two brothers

Coronoid hyperplasia is a rare condition of unknown aetiology that can occur in both unilateral and bilateral forms. Without radiographic investigation the diagnosis is often missed. Researchers have postulated a familial form of inheritance. This study reports the occurrence of coronoid hyperplasia in two brothers. The parents were unaffected and there are no other siblings. The diagnosis was confirmed with the aid of panoramic radiographs and axial computed tomographic scans with para-sagittal reconstructions which demonstrated enlargement of the coronoid processes and in one case impingement against the zygomatic bone. One brother was successfully treated with a unilateral intra-oral coronoidectomy whilst the other was unsuccessfully treated with a bilateral intra-oral coronoidectomy.

Radiographic evidence of cranial bone mobility

The purpose of this retrospective chart review was to determine if external manipulation of the cranium alters selected parameters of the cranial vault and base that can be visualized and measured on x-ray. Twelve adult patient charts were randomly selected to include patients who had received cranial vault manipulation treatment with a pre- and post-treatment x-ray taken with the head in a fixed positioning device. The degree of change in angle between various specified cranial landmarks as visualized on x-ray was measured. The mean angle of change measured at the atlas was 2.58 degrees, at the mastoid was 1.66 degrees, at the malar line was 1.25 degrees, at the sphenoid was 2.42 degrees, and at the temporal line was 1.75 degrees. 91.6% of patients exhibited differences in measurement at 3 or more sites. This study concludes that cranial bone mobility can be documented and measured on x-ray.

Radiation-induced craniofacial bone growth inhibition: development of an animal model

Craniofacial deformities caused by therapeutic radiation-induced bone growth inhibition can occur in up to 100% of survivors of childhood head and neck cancers. The mechanism of radiation-induced craniofacial bone growth inhibition is poorly understood. The objective of this study is to establish a model of radiation-induced craniofacial bone growth inhibition to study the pathophysiology of radiation on growing membranous bone. Seven-week-old male New Zealand white rabbits were randomized into 4 groups (n = 10/group) and received a single dose of orthovoltage radiation (0, 15, 25, or 35 Gy) to the right orbital-zygomatic complex. Serial radiographs and computed tomography scans were performed for cephalometric analysis, bone volume, and bone density measurements until skeletal maturity at 21 weeks. Statistically significant ( P < 0.05) reductions in orbital-zygomatic complex linear bone growth, bone volume, and bone density were found after radiation with 25 or 35 Gy compared with nonirradiated control animals. A significant ( P < 0.05) decrease in orbital-zygomatic complex volume was noted after 15-Gy radiation but there were no significant effects on linear bone growth as assessed by cephalometric analysis at this dose. This study establishes the rabbit orbital-zygomatic complex as a suitable model for the study of radiation-induced craniofacial bone growth inhibition and will permit investigation into the underlying cellular and molecular basis of this injury.

The use of computed tomography to define zygomatic complex position

PURPOSE

The purpose of this study was to analyze the use of midline references and landmarks to assess the position of the zygomatic complex relative to the cranial base, and to test the reliability of these measurements in assessing facial symmetry.

METHODS

Direct skull measurements were compared with measurements made on computed tomography (CT) images. The effect of CT scanner error, technologist error, gantry angle error, error of skull inclination, and error due to the presence of titanium rigid fixation hardware were assessed. To test observer variation and the effect of each level of error, 4 blinded bilateral measurements were repeated 3 times by 5 observers on both dry skull and CT scans. A mixed effect analysis of variance model then assessed for effect of method of measurement (dry skull vs CT), observer, CT scanner, technologist, gantry angle, skull inclination, and rigid fixation.

RESULTS

A total of 2,040 measurements were made. Measurements for zygomatic complex posterior and anterior width and height were reliable and had an interobserver variations of 0.02 +/- 0.03 mm, 0.5 +/- 0.4 mm, and 0.37 +/- 0.3 mm, respectively. The difference between dry skull and CT assessment for the 3 reliable measurements was 1.2 +/- 0.3 mm, 0.44 +/- 0.4 mm, and 1.1 +/- 0.5 mm, respectively. The errors produced by the CT scanner, technologist, and rigid internal fixation hardware were not clinically significant. The measurements were not sensitive to gantry angle and skull inclination changes of 10 degrees or less. A fourth measurement assessing zygomatic complex projection was found not to be accurate or reliable.

CONCLUSIONS

These findings suggest that the 3 CT scan measurements describing the position of the zygomatic complex relative to the cranial base are clinically useful.

Aneurysmal bone cyst of the zygoma. A case report and review of the literature

Aneurysmal bone cyst is a cystic vascular osseous tumor. It is rare in the craniofacial area; it is even rarer in the zygoma. A case of aneurysmal bone cyst of the zygoma was presented. Its pathogenesis, clinical and radiological features and treatment options were discussed under the view of the literature.

[Pneumatization of the zygomatic arch on pantomography]

BACKGROUND

The pneumatized spaces of the zygomatic arch (zygomatic air cell defect) are a clinically asymptomatic variation of the temporal bone. The empty spaces of the articular eminence and temporal bone of the zygomatic arch are depicted on radiographs as a sharply demarcated osteolytic lesion of round or oval shape. The aim of this study was to determine the prevalence and characteristics of the ZACD in our outpatients.

MATERIALS AND METHODS

We investigated the panoramic radiographs of 1,084 patients who were treated during 1 February and 31 July 2000. The mean age of the 1,084 patients was 41.9 years (SD: 17.2 years; range: 2-96): 628 patients were male (58%) and 456 female (42%). A ZACD was found in 20 of 1,084 patients (prevalence: 1.85%). The mean age of the patients with a ZACD was 43.2 years (SD: 18.4 years; range: 7-87): 11 were female (55%) and 9 male (45%).

RESULTS

A bilateral ZACD was found in 20% (four patients). Interestingly, one of these ZACD patients was a 7-year-old boy. Up to now, it had generally been accepted that pneumatization of the zygomatic arch takes place after puberty with the youngest persons with ZACD being 15 years of age. Our findings should prompt consecutive studies on the prevalence of ZACD in children. This finding can be relevant in patients treated for spreading otitis media or mastoiditis.

Placement of endosteal implants in the zygoma after maxillectomy: a Cadaver study using surgical navigation

Endosteal implants facilitate obturator prosthesis fixation in tumor patients after maxillectomy. Previous clinical studies have shown, however, that the survival of implants placed into available bone after maxillectomy is generally poor. Nevertheless, implants positioned optimally in residual zygomatic bone provide superior stability from a biomechanical point of view. In a pilot study, the authors assessed the precision of VISIT, a computer-aided surgical navigation system dedicated to the placement of endosteal implants in the maxillofacial area. Five cadaver specimens underwent hemimaxillectomy. The cadaver head was matched to a preoperative high-resolution computed tomograph by using implanted surgical microscrews as fiducial markers. The position of a surgical drill relative to the cadaver head was determined with an optical tracking system. Implants were placed into the zygomatic arch, where maximum bone volume was available. The results were assessed using tests for localization accuracy and postoperative computed tomographic scans of the cadaver specimens. The localization accuracy of landmarks on the bony skull was 0.6 +/- 0.3 mm (average +/- SD), as determined with a 5-df pointer probe; the localization accuracy of the tip of the implant burr was 1.7 +/- 0.4 mm. The accuracy of the implant position compared with the planned position was 1.3 +/- 0.8 mm for the external perforation of the zygoma and 1.7 +/-1.3 mm for the internal perforation. Eight of 10 implants were inserted with maximal contact to surrounding bone, and two implants were located unfavorably. Reliable placement of implants in this region is difficult to achieve. The technique described in this article may be very helpful in the management of patients after maxillary resection with poor support for obturator prostheses.

Complete bony fusion of the mandible to the zygomatic complex and maxillary tuberosity: case report and review

Congenital craniofacial disorders represent approximately 20% of all birth defects. One of these disorders is syngnathia, of which only 24 cases have been reported since 1936. Twenty cases involved fusion of the alveolar processes of the maxilla and mandible. Only four are similar to the presented case, which includes bony fusion of the ascending ramus of the mandible to the zygomatic complex and the posterior part of the maxilla. This case report will present details from the 23rd week of gestation to 8 months of age when the infant underwent the first attempt to free the syngnathia. The literature is discussed and a causative mechanism and new classification are proposed.

Reduction malarplasty through an intraoral incision: a new method

Until recently, osteotomies and surgeries to reposition prominent zygoma have been performed by means of a coronal incision or intraoral and preauricular incisions. Such incisions have penalties such as scars, the possibility of facial nerve injury, and long operative times. After reflecting on their past experiences with facial bone surgery, the authors developed an alternative approach. In this method, the cheekbone protrusion is corrected by performing an osteotomy and repositioning through an intraoral incision only. During the past 3 years, the authors have operated on 23 patients with malar prominences. The amount of bone to be removed is determined by preoperative interviews, physical examinations, and x-rays. Intraoral incisions provide access to the zygomatic body and lateral orbital rim. After L-shaped osteotomies (two parallel vertical and one transverse osteotomy at the medial part of the zygomatic body), the midsegment is removed. The posterior portion of the zygomatic arch was approached through the medial aspect and was outfractured using a curved osteotome. After completing the triple osteotomy, the movable zygomatic complex was reduced medially and fixed with miniplates and screws on the zygomaticomaxillary buttress. The patients were followed for 9.5 months, with acceptable results and few complications. The authors conclude that this technique is an effective and safe method of reduction malarplasty.

Computer-assisted quantitative measurements by three-dimensional images on zygomatic fracture deformities

OBJECTIVE

To investigate an available method for quantitative diagnosis of zygomatic fractures that allow quantitative classification and diagnosis.

METHODS

The radiographs and 2- and 3-dimensional CT images of 57 patients with zygomatic fractures were measured and analyzed by a computer-assisted measuring system before and after treatment. This was used to diagnose the displacement and deformity of the fractures.

RESULTS

(1) Using anthropology points and a computer-assisted measuring system, a new method was established to assess the displacement of the zygomatic fractures. (2) Displacement of the zygomatic fractures was approximately diagnosed by measuring different angles of the CT images. (3) A new classification was proposed based on the deformities of the zygomatic fractures: Type A, zygomatic body was intact and not displaced; Type B, zygomatic body was intact but displaced (including comminuted zygomatic arch fractures); Type C, zygomatic body was comminuted and displaced. (4) There were 4 subtypes with characteristics in the most common Type B fractures. (5) Different images had different advantages for diagnosing zygomatic fractures.

CONCLUSIONS

(1) Displacement of the zygomatic fractures can be quantitatively diagnosed by measuring 3-D CT images. (2) The computer-assisted 3-D CT measuring system is accurate, reliable, and clinically feasible for diagnosing zygomatic fractures. (3) The best image to diagnose the displacement of the fractures should be used.

The zygomaticus fixture: an alternative approach for implant anchorage in the posterior maxilla

Implant rehabilitation of the edentulous maxilla continues to challenge the ingenuity and clinical skills of the surgeon and restorative dentist. Advanced posterior alveolar resorption combined with increased maxillary sinus pneumatization often leaves insufficient bone for implant anchorage. Even more challenging are conditions such as cleft deformities and maxillectomy defects which present a discontinuous maxilla and complex bony and soft tissue anatomy. Much attention has been paid to combining bone graft procedures either with immediate or delayed implant placement in the management of this type of complex defect anatomy. Various types of bone graft augmentation methods carry significant patient morbidity, require lengthy healing time and are resource demanding. Recently Brånemark introduced an alternative method of securing posterior maxillary implant anchorage using a longer titanium implant placed through the palatal aspect of the second premolar region transantrally into the os zygomaticum (zygoma). This paper describes the indications and clinical applications of the zygomaticus fixture and reviews current outcome data.

Assessment of zygomatico-orbital complex fractures using ultrasonography

Twenty-two patients were referred to the maxillofacial surgical unit for assessment and management of suspected fractures of the zygomatico-orbital complex. In each case, both routine plain radiographic and ultrasound examinations were made. The aim of the study was to investigate the sensitivity and reliability of ultrasound to detect such fractures. Imaging with ultrasound was carried out at five areas: the infraorbital margin; lateral wall of the maxillary sinus; zygomatic arch; frontozygomatic process; and orbital floor. Both radiographic and ultrasound findings were correlated with the findings at operation. An overall agreement of 85% between radiographs and ultrasound scans was found. Ultrasound imaging was most reliable at the lateral wall of the maxillary sinus, where the sensitivity was 94% and specificity 100%. The positive predictive value at this area was 100% compared with radiographic findings. We conclude that ultrasound is a useful tool in imaging facial trauma as an initial investigation, and can help to reduce the total number of radiographs required for the diagnosis of fractures of the zygomatico-orbital complex.

Comparison of the panoramic radiographic and CT features of post-Caldwell-Luc maxillary sinuses

OBJECTIVE

To clarify the panoramic radiographic features of the post-Caldwell-Luc maxillary sinus.

METHODS

The panoramic radiographs were compared with the axial CT scans of 48 symptomatic post-Caldwell-Luc maxillary sinuses which had been operated on more than 5 years previously.

RESULTS

The two characteristic features of the post-Caldwell-Luc maxillary sinus on panoramic radiographs were a right-angled triangular shape, due to absence of the floor of the maxillary sinus and radiopacity of the posterior wall and zygomatic bone, and an ill-defied panoramic innominate line. This shape was related to the finding of a contracted sinus with a radiolucent lumen on the CT scans. There was also close relationship between the ill-defined panoramic innominate line and thickened posterior wall on the CT scans.

CONCLUSION

The characteristic features of the post-Caldwell-Luc maxillary sinus on panoramic radiographs were a right-angled triangular shape and an ill-defined panoramic innominate line. These features were related to a contracted sinus and a thickened posterior wall on the CT scans.

Incidence of os japonicum in Anatolian dry skulls and plain cranium radiographs of modern Anatolian population

INTRODUCTION

The zygoma may sometimes be divided into two parts by either a horizontal or a vertical suture. Such a bipartite bone has been given the name of os japonicum as it has been mostly observed in Japanese.

MATERIAL

In this study 1266 zygomatic bones in 633 Anatolian dry skulls and 1348 zygomatic bones in 674 plain cranium radiographs of adult patients have been examined.

RESULTS

Os japonicum was present in 2.2% of female and 1.7% of male subjects. All of the 24 multipartite bones observed in the study were bipartite except one. In addition, of 690 female zygomatic bones examined radiologically 15 (2.2%), and 658 male bones 12 (1.8%) were bipartite or tripartite, a total of 674 plain cranium radiographs.

CONCLUSION

The results were compared with those of other populations. As a result evaluation of both dry skulls and plain radiographs as a single sample, our results were again closely similar to Main Island Japan and other East Asia groups.

Intraosseous hemangioma of the orbit

Intraosseous hemangiomas of the orbit are very rare tumors. A case of cavernous hemangioma of the superolateral orbital rim is presented. A 45-year-old woman had a 1-year history of progressive swelling in the left lateral brow area. A computed tomography scan showed a well-marginated osteolytic lesion on the frontal bone near the frontozygomatic suture. The lesion was thought to be fibrous dysplasia, and the patient underwent tumor excision. The histological diagnosis was cavernous hemangioma. Cavernous spaces were filled with blood between the bony trabeculae. The spaces were lined by benign flattened endothelium. Intraosseous hemangioma should be suspected when a patient presents with an enlarging mass fixed to bone around the orbit.