Fluctuating asymmetry of the normal facial skeleton.

The purpose of this study was to produce reliable estimations of fluctuating facial asymmetry in a normal population. Fifty-four computed tomography (CT) facial models of average-looking and symmetrical Chinese subjects with a class I occlusion were used in this study. Eleven midline landmarks and 12 pairs of bilateral landmarks were digitized. The repeatability of the landmark digitization was first evaluated. A Procrustes analysis was then used to measure the fluctuating asymmetry of each CT model, after all of the models had been scaled to the average face size of the study sample. A principal component analysis was finally used to establish the direction of the fluctuating asymmetries. The results showed that there was excellent absolute agreement among the three repeated measurements. The mean fluctuating asymmetry of the average-size face varied at each anthropometric landmark site, ranging from 1.0mm to 2.8mm. At the 95% upper limit, the asymmetries ranged from 2.2mm to 5.7mm. Most of the asymmetry of the midline structures was mediolateral, while the asymmetry of the bilateral landmarks was more equally distributed. These values are for the average face. People with larger faces will have higher values, while subjects with smaller faces will have lower values.

New approach to establish an object reference frame for dental arch in computer-aided surgical simulation.

The purpose of this study was to develop a principal component analysis-based adaptive minimum Euclidean distances (PAMED) approach to establish an optimal object reference frame for symmetrical alignment of the dental arch during computer-aided surgical simulation (CASS). It was compared with our triangular methods and the standard principal component analysis (PCA) method. Thirty sets of maxillary digital models were used. Midsagittal and occlusal planes were ranked by three experienced evaluators based on their clinical judgment. The results showed that for the midsagittal plane, all three evaluators ranked "ideal" for all 30 models with the PAMED method, 28 with the triangular method, and at least 11 with the PCA method. For the occlusal plane, one evaluator ranked all 30 models "ideal" with both the PAMED and the PCA methods while the other two evaluators ranked all 30 models "ideal" with the triangular method. However, the differences among the three methods were minimal. In conclusion, our PAMED method is the most reliable and consistent approach for establishing the object reference frame for the dental arch in orthognathic surgical planning. The triangular method should be used with caution because it can be affected by dental arch asymmetry. The standard PCA method is not recommended.

There is variability in our perception of the standard head orientation.

The purposes of this study were to determine: (1) whether an observer's perception of the correct anatomical alignment of the head changes with time, and (2) whether different observers agree on the correct anatomical alignment. To determine whether the perception of the correct anatomical alignment changes with time (intra-observer comparison), a group of 30 observers were asked to orient, into anatomical alignment, the three-dimensional (3D) head photograph of a normal man, on two separate occasions. To determine whether different observers agree on the correct anatomical alignment (inter-observer comparison), the observed orientations were compared. The results of intra-observer comparisons showed substantial variability between the first and second anatomical alignments. Bland-Altman coefficients of repeatability for pitch, yaw, and roll, were 6.9°, 4.4°, and 2.4°, respectively. The results of inter-observer comparisons showed that the agreement for roll was good (sample variance 0.4, standard deviation (SD) 0.7°), the agreement for yaw was moderate (sample variance 2.0, SD 1.4°), and the agreement for pitch was poor (sample variance 15.5, SD 3.9°). In conclusion, the perception of correct anatomical alignment changes considerably with time. Different observers disagree on the correct anatomical alignment. Agreement among multiple observers was bad for pitch, moderate for yaw, and good for roll.

Algorithm for planning a double-jaw orthognathic surgery using a computer-aided surgical simulation (CASS) protocol. Part 1: planning sequence.

The success of craniomaxillofacial (CMF) surgery depends not only on the surgical techniques, but also on an accurate surgical plan. The adoption of computer-aided surgical simulation (CASS) has created a paradigm shift in surgical planning. However, planning an orthognathic operation using CASS differs fundamentally from planning using traditional methods. With this in mind, the Surgical Planning Laboratory of Houston Methodist Research Institute has developed a CASS protocol designed specifically for orthognathic surgery. The purpose of this article is to present an algorithm using virtual tools for planning a double-jaw orthognathic operation. This paper will serve as an operation manual for surgeons wanting to incorporate CASS into their clinical practice.

Algorithm for planning a double-jaw orthognathic surgery using a computer-aided surgical simulation (CASS) protocol. Part 2: three-dimensional cephalometry.

Three-dimensional (3D) cephalometry is not as simple as just adding a 'third' dimension to a traditional two-dimensional cephalometric analysis. There are more complex issues in 3D analysis. These include how reference frames are created, how size, position, orientation and shape are measured, and how symmetry is assessed. The main purpose of this article is to present the geometric principles of 3D cephalometry. In addition, the Gateno-Xia cephalometric analysis is presented; this is the first 3D cephalometric analysis to observe these principles.

An in vitro study of the accuracy of a new protocol for planning distraction osteogenesis of the mandible.

PURPOSE: The purpose of this study was to determine the in vitro accuracy of a new protocol for distraction osteogenesis of the mandible that involves a planning process and a surgical technique. MATERIALS AND METHODS: An experimental design was developed to simulate distraction osteogenesis on stereolithographic models of patients with craniofacial deformities. All patients had previously undergone 3-dimensional computerized scans of the craniofacial skeleton. The data from these scans were used to generate stereolithographic models. Before the fabrication of the models, the computed tomography (CT) data were manipulated to add a series of rulers and markers to the models. The 3-dimensional computerized scans were also used as the basis of the planning process. They were imported into an animation software (3D-Studio Max; Discreet, Montreal, Canada), and a virtual distractor was built and installed on the model, and the osteotomies and distraction processes were simulated. Finally, a recipe for sequencing the linear and angular changes of the distractor were calculated. A surgical technique was developed to facilitate the precise installation of the distractor as indicated in the presurgical plan. The transfer of information regarding pin position and orientation from the computer model to the patient was accomplished by creating a surgical template. This template was designed in the computer and fabricated by use of stereolithography. Mock surgery was performed on the stereolithographic models, and the results were compared with those predicted by the computer. The difference between the actual position and the predicted position was recorded. RESULTS: On the X-axis, the difference between the predicted position for the condylar marker and the actual position of the marker on the stereolithographic models was 0.6 +/- 1.1 mm. On the Y-axis, the difference between the predicted position for the condylar marker and the actual position of the marker on the stereolithographic models was -0.9 +/- 2.6. On the Z-axis, the difference between the predicted position for the condylar marker and the actual position of the marker on the stereolithographic models was 0.04 +/- 0.8 mm. There was excellent correlation between the predicted and the actual measurements for the X, Y, and Z axes: 0.98, 0.93, and 0.98, respectively. CONCLUSIONS: The results indicate that the combination of this planning process and surgical technique was very accurate. This in vitro study is the first step in determining the clinical usefulness of this protocol. If the results of this study are validated in clinical practice, this protocol will allow clinicians to improve the clinical outcomes of patients treated with distraction osteogenesis.

Computer planning for distraction osteogenesis.

Distraction osteogenesis of the mandible has found an application in the treatment of patients with a variety of different mandibular deformities. Compared with the relatively simple unidirectional distraction of long bones as described by Ilizarov, the three-dimensional distraction of the mandible is extremely complex. Whereas experience with orthognathic surgery clearly demonstrates that careful presurgical planning is necessary to achieve predictable outcomes, there are few reported methods for the planning of mandibular distraction. The authors have developed a method for planning distraction osteogenesis of the mandible that involves the use of three-dimensional modeling and animation to simulate distraction osteogenesis in virtual reality. The first step in the authors' treatment planning process is to obtain a three-dimensional computerized scan of the facial skeleton. From this scan, a three-dimensional wire-mesh model is built using animation software. With the same software, a virtual distractor is built and installed on the wire-mesh model. The osteotomies and the distraction process are then simulated. Finally, a recipe for sequencing the linear and angular changes of the distractor is calculated. The authors have used this planning process in seven patients (age range, 4 to 10 years): four with unilateral mandibular deformities and three with bilateral. The planning process has yielded predictable and reproducible results.

Distraction osteogenesis: a new surgical technique for use with the multiplanar mandibular distractor.

If distraction osteogenesis is to reach its full potential and achieve the level of accuracy that is possible with orthognathic surgery, its outcomes need to be as predictable. To this end, the authors developed a planning process for distraction osteogenesis similar to that used in orthognathic surgery. However, the success of the planning process depends on the authors' ability to execute the plan at the time of surgery. As a result, the authors needed to develop a surgical technique that would enable them to precisely install the distractor as indicated in the presurgical plan. The surgical technique presented in this article was developed for this purpose. The authors used this technique in seven patients (four boys and three girls; age range, 4 to 10 years). Four patients presented with unilateral deformities, and three patients presented with bilateral deformities. The follow-up period in this group of patients ranged from 12 to 33 months. The purpose of the technique is to replicate the position of the distractor on the mandible as determined by the presurgical plan. To this purpose, a custom drill guide and a surgical template have been developed. Both of these are used following the principles of triangulation to establish the pin position and orientation of the distractor. In the authors' hands, the use of this surgical technique has resulted in outcomes close to those predicted by the planning process.

Changing patterns in the epidemiology and treatment of zygoma fractures: 10-year review.

A ten year retrospective review of 259 zygoma fractures is presented to highlight changes in epidemiology and treatment. Motor vehicle-related trauma resulted in a majority of the injuries (80.6%), with a high incidence of multiple facial fractures (43.2%). The number of zygomatic and other facial fractures decreased over the duration of the study (by 50.0% and 20.1%, respectively, p < 0.05), perhaps reflecting lowered speed limits and the increased use of seat belts. The proportion of fractures receiving open reduction and internal fixation (ORIF) remained relatively constant (46.3%). At present, miniplate fixation is the preferred surgical treatment, accounting for 61.5% of cases in 1988 and 1989. There was a trend toward the use of multiple fixation sites and more frequent use of the lateral maxillary buttress (20.0% increase over the study period). The need for orbital floor exploration decreased by almost half, possibly reflecting improved preoperative radiologic evaluation. Despite the recent popularity of cranial bone grafting for facial reconstruction, silicone rubber was the preferred material for orbital floor repair (59.6% of cases). Although overall surgical complications were few (1.5%) there was a high incidence of associated ocular injuries (36.3%).

The treatment of nasal valve obstruction.

The purpose of this study is to present the authors' experience with nasal valve obstruction and their management scheme. Between July 1, 1988 and June 30, 1991, 27 patients were seen for nasal valve obstruction. There were 17 males and 10 females, with a median age of 39.2 years. The internal valve alone was involved in 14 patients, the external valve was involved in 2 patients, both valves were involved in 11 patients, and significant septal deviation was seen in 15 patients. Nasal valve obstruction resulted from previous surgery in 13 patients, from trauma in 8 patients, and from a "narrow nose" in 4 patients. Twenty-four patients were treated successfully, while 3 patients, seen early in the series, failed to improve. All patients were followed for a minimum of 1 year. Surgery in the nasal valve is done through an open approach and involves a systematic approach to all the structures surrounding the nasal valve. Surgical repositioning and cartilage grafting are used to reconstruct the nasal valve.

The management of septal perforations.

Twenty-five patients with septal perforations were seen between July 1, 1983, and June 30, 1989. There were 16 males and 9 females, who ranged in age from 21 to 72 years, with the median age of 41.7 years. The majority of the perforations were traumatic in origin, with 19 cases seen following septal surgery, and were between 1.5 and 2.5 cm (20), with a range of 0.5 to 4 cm. All were located at the posterior border of the quadrilateral cartilage at the vomer-ethmoid junction. All but 3 patients underwent surgical repair, and successful closure was achieved in all but 3. However, only 1 patient remained symptomatic after surgery. The surgical technique employed includes an external rhinoplasty approach, septal and intranasal mucosal flaps, and an autograft of mastoid periosteum or temporalis fascia.

Treatment of nasal surgery complications.

There are numerous articles on how to prevent and manage the untoward aesthetic and functional results of nasal surgery. However, little has been written on the disabling or life-threatening complications of nasal surgery. Recent series have reported the incidence of these complications to be between 5% and 18%. Severe complications from nasal surgery can be divided into the following four categories: hemorrhagic, infectious, traumatic, and miscellaneous. Postoperative hemorrhage is the most commonly seen problem. However, there are numerous case reports of toxic shock syndrome associated with nasal surgery and even of intracranial complications. In this article, we provide an overview of these complications and their treatment.

External rhinoplasties: indications for use.

The technique, indications and role of external rhinoplasty in nasal surgery are presented. The technique has been utilised in 563 patients with a minimum follow-up of 18 months. The external approach has been especially helpful in the severely twisted nose, secondary rhinoplasty, augmentation rhinoplasty, congenital deformities of the nose, closure of septal perforations and in the teaching and learning of rhinoplasty. In this series there were no reported complications attributable to the external approach.

The radiology of upper airway obstruction in maxillofacial trauma.

One of the prime considerations in the management of maxillofacial trauma is the diagnosis and prevention of acute upper airway obstruction. Each division of the upper aerodigestive tract may cause respiratory obstruction. In the oral cavity, a "flail" mandible, an "Andy Gump" deformity, and a sublingual hematoma may occur. In the nasopharnynx, an impacted midface, a split palate, and a nasopharyngeal hematoma may result. In the oropharynx and hypopharynx, an expanding hematoma in the retropharyngeal or lateral pharyngeal spaces may be seen. Although airway obstruction in maxillofacial trauma is a clinical diagnosis, the judicious use of radiographs helps to identify patients at risk. In this study, we review the anatomy of the upper aerodigestive tract and the potential sites of airway obstruction. A review of the radiology of airway obstruction in maxillofacial trauma will also be presented.

External rhinoplasty technique.

External rhinoplasty is a valuable tool in the surgical armamentarium of all nasal surgeons. It does not change the dynamics of the operation but offers a new method of exposure. The purpose of this paper is to present our experience with the external rhinoplasty technique in 601 patients, and review the results and complications of this approach to nasal surgery. Two patient reports are presented to demonstrate use of the technique in nasal surgery.

Nasal surgery complications.

This study examines the incidence of serious complications in nasal surgery and discusses the diagnosis and management of these complications. The authors review 259 consecutive cases performed between January 1, 1983, and August 31, 1988. One-hundred and ninety-five patients had septorhinoplasties, 29 had septoplasties, and 35 had rhinoplasties. Thirteen of these cases involved serious complications as follows: hemorrhage (5), perforation (4), infections (3), and pneumocephalus (1). All the patients with these serious complications had associated septal and/or turbinate surgery. The diagnosis and management of these complications will be discussed. In this small series of nasal surgery patients, the incidence of serious complications was 5.0 percent, with no fatalities reported. The higher incidence of serious complications occurred when associated septal and/or turbinate surgery was required. Awareness of these complications is essential because of the increasing number of patients presenting to plastic surgeons for nasal surgery in whom associated septal and/or turbinate surgery is necessary.

Rhinectomy: timing and reconstruction.

Cancer of the nasal skin is usually well-circumscribed, superficial, and has an excellent prognosis. However, a small number of aggressive lesions require a partial or total rhinectomy. We retrospectively reviewed patients seen at the M.D. Anderson Cancer Center between January 1, 1970, and December 31, 1980, for nasal cancer. There were 147 patients identified as requiring full-thickness nasal resections, of whom 68 (46.3%) required a hemi- or complete rhinectomy. Lesions requiring extensive rhinectomy usually involved the ala or were recurrent multicentric, squamous cell carcinomas greater than 4 cm. These patients had significantly poorer prognoses than the group in general. Recurrence developed in 45 patients (30.6%), and two thirds of all recurrences were seen within 2 years. In this series, the histology of the malignancy and its size, in the case of large basal cell carcinomas, were both predictive of a poor prognosis. Only the primary site was significant in predicting recurrence, whereas tumor size and histology were significant predictors of the need for an extensive rhinectomy. Delayed reconstruction is recommended in patients who are in poor health and have large recurrent lesions that are multicentric or involve the ala or dorsum. The timing of reconstruction is individualized, but a 2-year wait after surgery is recommended. Prosthetic rehabilitation is a good interim measure.