John Lo

The long-term effect of transport distraction in the management of temporomandibular joint ankylosis.

Background: The purpose of this study was to investigate the long-term effect of condylar reconstruction by transport distraction of the mandibular ramus after the release of temporomandibular joint ankylosis. Methods: Five patients presenting with unilateral temporomandibular joint ankylosis corrected by gap arthroplasty and transport distraction of the ascending mandibular ramus were recruited for this prospective cohort study. A clinical evaluation of each case was performed longitudinally before and during the operation, during the distraction consolidation period, and 1 to 2 years after removal of the distractor. The assessment criteria included temporomandibular joint mobility and patient satisfaction expressed with reference to a visual analogue scale. Results: The mean preoperative mouth opening of the five patients was 14 mm. Coronoidectomies were performed concurrently to widen the mouth opening in all cases. Maxillomandibular osteotomies were performed in three cases to correct associated dentofacial deformities. The mean mouth opening achieved during the operations was 40.4 mm. At long-term follow-up, the mean mouth opening was 38 mm, and no sign or symptom of temporomandibular joint dysfunction was noted. The mean patient satisfaction score was 8.6 of 10. Conclusions: Transport distraction of the mandibular ramus is a good treatment modality for temporomandibular joint ankylosis, particularly for adults. It can achieve long-term, symptom-free, stable mouth opening.

Three-dimensional cephalometric norms of Chinese adults in Hong Kong with balanced facial profile

OBJECTIVE The objectives of this study were (1) to develop a 3D cephalometric analysis scheme applicable to assessing dentofacial deformities; and (2) to create a normative database of 3D cephalometric measurements for adult Chinese in Hong Kong. STUDY DESIGN A cross-sectional study was conducted on 50 male and 50 female adults with normal balanced facial profile and occlusion. Cone-beam computed tomography and stereo photogrammetry imaging were performed on all subjects. Three-dimensional virtual models were generated from imaging data, and cephalometric analysis was performed using specialized software. A new 3D cephalometric analysis scheme appropriate for orthognathic surgery as well as a new reference plane (supraorbital margin plane) for midfacial assessment was used in this study. RESULTS The cephalometric norms generated in this study were comparable with those reported in the literature for conventional 2D cephalometric analysis and the unique features of Chinese faces. The results also showed significant differences between males and females in most of the facial height measurements (P < .01). CONCLUSIONS This is the first database of 3D cephalometric norms based on CBCT and 3D photogrammetry of the Chinese population in Hong Kong. This can be a useful reference for characterizing facial deformities in 3 dimensions. Moreover, 3D cephalometric analysis has the potential of incorporating new measurement methods that are difficult if not impossible in 2D cephalometric analysis.

Perioperative antibiotic prophylaxis in orthognathic surgery: a systematic review and meta-analysis of clinical trials.

OBJECTIVE The aim of this study was to investigate whether the use of antibiotic prophylaxis in orthognathic surgery can effectively reduce the postoperative infection rate. STUDY DESIGN Electronic databases were searched and reference lists checked. Full articles meeting the inclusion criteria were retrieved. Study details and outcome data of these reports were statistically analyzed. There was no language limitation. RESULTS Five randomized clinical trials were included in the final review process: 4 articles compared the period of prophylactic antibiotic usage, and 1 compared the infection prevention effect of different types of antibiotics with placebo. Although a significantly higher infection rate was found in the placebo group, no significant difference could be found related to infection prevention between short- and long-term antibiotic regimen. CONCLUSIONS Prophylactic antibiotic regimen is considered to be useful for infection prevention in orthognathic surgery. A single-dose regimen is recommended; application for extended postoperative period is not advocated.

Are postoperative intravenous antibiotics necessary after bimaxillary orthognathic surgery? A prospective, randomized, double-blind, placebo-controlled clinical trial

Postoperative antibiotic prophylaxis is often administered intravenously, despite an increased morbidity rate compared with oral application. This study investigates whether a postoperative oral antibiotic regimen is as effective as incorporation of intravenous antibiotics after bimaxillary orthognathic surgery. 42 patients who underwent bimaxillary orthognathic surgery between December 2008 and May 2010 were randomly allocated to 2 placebo-controlled postoperative antibiotic prophylaxis groups. Group 1 received oral amoxicillin 500mg three times daily; group 2 received intravenous ampicillin 1g four times daily, during the first two postoperative days. Both groups subsequently took oral amoxicillin for three more days. Clinically, the infection rate was assessed in both study groups for a period of 6 weeks after the surgery. 9 patients (21.4%) developed infection. No adverse drug event was detected. No significant difference (p=0.45) was detected in the infection rate between group 1 (3/21) and group 2 (6/21). Age, type of surgical procedures, duration of the operative procedure, surgical procedure-related events, blood loss, and blood transfusion were all found not related to infection (p>0.05). Administration of more cost-effective oral antibiotic prophylaxis, which causes less comorbidity, can be considered to be safe in bimaxillary orthognathic surgery with segmentalizations.

Computer-Aided Maxillofacial Surgery: An Update

Introduction. Recent developments in technology have revolutionized medicine and surgery. This article aims at providing an update on the current trends in computer-aided maxillofacial surgery and illustrates these advances with clinical cases. Methods. The PubMed database was searched for articles published during the past 5 years using the keywords “maxillofacial” and “surgery, computer-assisted.” Full texts of relevant articles were retrieved, and their study details were extracted. Results. Among the 133 articles, most focused on cone-beam computed tomography (CBCT), stereophotography, surgical panning software, and intraoperative navigation. Stereophotography produces 3D facial photographs with natural color and texture, whereas CBCT generates excellent hard-tissue images with a substantially lower radiation than conventional CT scans. Information gathered from CBCT and stereophotography can be used for accurate diagnosis, virtual planning, and simulation of surgery with the aid of specialized software. The preplanned treatment can be executed accurately via intraoperative surgical navigation. Conclusion. Tremendous potential exists for computer-aided maxillofacial surgery as it moves from research to clinical care.

Facial soft tissue response to anterior segmental osteotomies: A systematic review

Bimaxillary protrusion is prevalent among Asians and anterior segmental osteotomies are commonly used for its surgical correction. The objective of this study was to evaluate the soft tissue changes resulting from anterior segmental osteotomies. The electronic databases PubMed, Scopus and ISI Web of knowledge were searched for potentially eligible studies using a set of predetermined keywords. Full texts meeting the inclusion criteria were retrieved and their references were manually searched for additional relevant articles. The study details and outcome data of these reports were extracted using spreadsheets for comparison. The methodological quality of each study was assessed. Eleven studies met the inclusion criteria. Lateral cephalometry was used in all studies. A reduction of the labial prominence with an increase in the nasolabial angle was noted subsequent to anterior segmental osteotomies. The magnitude of the reported soft tissue changes and their ratios corresponding to the osseous movements varied among studies. Long-term, prospective, methodologically sound clinical trials with larger samples and three-dimensional quantification are required to provide sufficient information for predicting the soft tissue response to anterior segmental osteotomies.

Three-Dimensional Color Maps: A Novel Tool for Assessing Craniofacial Changes

Introduction. Three-dimensional (3D) color maps are useful for analyzing data acquired by laser scanning, stereophotography, or computed tomography (CT). The authors aim to illustrate the different applications of color maps in the craniomaxillofacial region. Methods. The images obtained from the above techniques at 2 different time points are superimposed based on a common area unaffected by the surgical intervention or growth. Using specialized software, the distance differences between the 2 superimposed images are depicted in a graphical format as a 3D color map. A color-coded scale indicating the distances accompanies these maps. Results. 3D color maps can be manipulated and viewed in a variety of angles to extract the maximum diagnostic information. They facilitate the critical evaluation of facial asymmetry, accuracy of fusing CT and 3D photo data sets, and postsurgical changes. Conclusion. 3D color maps aid the objective assessment of craniofacial structures while enhancing visual comprehension and communication with patients.

Three-dimensional photogrammetry for surgical planning of tissue expansion in hemifacial microsomia.

We aim to illustrate the applications of 3‐dimensional (3‐D) photogrammetry for surgical planning and longitudinal assessment of the volumetric changes in hemifacial microsomia.

Automatic Detection and Reproduction of Natural Head Position in Stereo-Photogrammetry

The aim of this study was to develop an automatic orientation calibration and reproduction method for recording the natural head position (NHP) in stereo-photogrammetry (SP). A board was used as the physical reference carrier for true verticals and NHP alignment mirror orientation. Orientation axes were detected and saved from the digital mesh model of the board. They were used for correcting the pitch, roll and yaw angles of the subsequent captures of patients’ facial surfaces, which were obtained without any markings or sensors attached onto the patient. We tested the proposed method on two commercial active (3dMD) and passive (DI3D) SP devices. The reliability of the pitch, roll and yaw for the board placement were within ±0.039904°, ±0.081623°, and ±0.062320°; where standard deviations were 0.020234°, 0.045645° and 0.027211° respectively. Conclusion: Orientation-calibrated stereo-photogrammetry is the most accurate method (angulation deviation within ±0.1°) reported for complete NHP recording with insignificant clinical error.

Accuracy of Different Modalities to Record Natural Head Position in 3 Dimensions: A Systematic Review.

PURPOSE Three-dimensional (3D) images are taken with positioning devices to ensure a patients stability, which, however, place the patients head into a random orientation. Reorientation of images to the natural head position (NHP) is necessary for appropriate assessment of dentofacial deformities before any surgical planning. The aim of this study was to review the literature systematically to identify and evaluate the various modalities available to record the NHP in 3 dimensions and to compare their accuracy. MATERIALS AND METHODS A systematic literature search of the PubMed, Cochrane Library and Embase databases, with no limitations on publication time or language, was performed in July 2015. The search and evaluations of articles were performed in 4 rounds. The methodologies, accuracies, advantages, and limitations of various modalities to record NHP were examined. RESULTS Eight articles were included in the final review. Six modalities to record NHP were identified, namely 1) stereophotogrammetry, 2) facial markings along laser lines, 3) clinical photographs and the pose from orthography and scaling with iterations (POSIT) algorithm, 4) digital orientation sensing, 5) handheld 3D camera measuring system, and 6) laser scanning. Digital orientation sensing had good accuracy, with mean angular differences from the reference within 1° (0.07 ± 0.49° and 0.12 ± 0.54°, respectively). Laser scanning was shown to be comparable to digital orientation sensing. The method involving clinical photographs and the POSIT algorithm was reported to have good accuracy, with mean angular differences for pitch, roll, and yaw within 1° (-0.17 ± 0.50°). Stereophotogrammetry was reported to have the highest reliability, with mean angular deviations in pitch, roll, and yaw for active and passive stereophotogrammetric devices within 0.1° (0.004771 ± 0.045645° and 0.007572 ± 0.079088°, respectively). CONCLUSIONS This systematic review showed that recording the NHP in 3 dimensions with a digital orientation sensor has good accuracy. Laser scanning was found to have comparable accuracy to digital orientation sensing, but routine clinical use was limited by its high cost and low portability. Stereophotogrammetry and the method using a single clinical photograph and the POSIT algorithm were potential alternatives. Nevertheless, clinical trials are needed to verify their applications in patients. Preferably, digital orientation sensor should be used as a reference for comparison with new proposed methods of recording the NHP in future research.