G. Shen

Navigation-guided gap arthroplasty in the treatment of temporomandibular joint ankylosis.

Gap arthroplasty, used in the treatment of temporomandibular joint (TMJ) ankylosis, is challenging, requiring resecting of massive abnormal bone formation at the skull base with complex and distorted anatomy. This study evaluated the application of image-guided navigation to gap arthroplasty. Four gap arthroplasties were performed on patients with unilateral TMJ ankylosis under computer-assisted navigation guidance. After preoperative planning and 3-dimensional simulation, the normal anatomic structures of the TMJ were created by superimposing and comparing the unaffected and affected sides. The amount and range of ankylotic bone to be resected was determined and displayed. Registration achieved an accurate match between the intra-operative anatomy and the CT virtual images. Anatomic structures and the position of surgical instruments were shown real time on the screen. In all cases the accuracy of the system measured by the computer did not exceed 1mm. No complications occurred and the mean minimal thickness of the skull base between middle cranial fossa and reconstructed glenoid fossa was 1.97 mm. Using image-guided navigation resulted in safe surgical excision of the bony ankylosis from the skull base. Navigation-guided resection of the ankylotic bone in the TMJ gap arthroplasty was a valuable and safe technique in this potentially complicated procedure.

Effect of fiducial configuration on target registration error in image-guided cranio-maxillofacial surgery

OBJECTIVEnTo investigate the effect of the configuration of fiducials on target registration error (TRE) and test the accuracy of theoretical model of TRE prediction in image-guided cranio-maxillofacial surgery.nnnMETHODSnA skull specimen was prepared with 20 titanium microscrews placed at defined locations and scanned with a 64-slice spiral computed tomography unit. These markers were separated into a registration fiducial group and a target fiducial group. An optical tracking system was used to perform skull-to-image registration procedures. Subsequent to each registration, the TRE was calculated by the navigation system. Each configuration registration was performed 50 times and the average was regarded as TRE of the configuration. The TRE prediction was also calculated for each configuration.nnnRESULTSnThe TRE ranged from 0.58 mm to 3.88 mm. Relatively smaller values of TRE may be achieved by placing a majority of fiducials on the maxillary alveolus in proximity to the target and placing a small number on the cranium contralaterally. The TRE values are always larger than the corresponding TRE prediction but there is a high correlation between them.nnnCONCLUSIONnThe configuration of fiducials is an important factor in minimizing TRE and the TRE prediction is a good guide for fiducial marker placement.

A novel device for preoperative registration and automatic tracking in cranio-maxillofacial image guided surgery

Objective: Two key issues in image guided surgery are accurate patient-to-image registration and ongoing tracking of the patients motion. To address these concerns, a novel device for preoperative registration and automatic tracking was designed, and the accuracy attainable with the device was evaluated in experiments with a skull and in a clinical study. Methods: The device consists of a system of four titanium screws and four fluorescent spheres fixed to carbon bars which can be easily mounted on the maxillary dentition splint. Before surgery, CT image data of a skull with the device in place was acquired and registered in a navigation system. The rigidity and reproducibility of positioning of the device were measured in 15 repeated CT acquisitions of the skull with the device in place. The registration accuracy was compared to that obtained using micro-screw markers fixed to the maxillary alveolus. To determine the potential of the device in aiding image guided cranio-maxillofacial surgery, registration accuracy and surgical outcome were assessed. Results: Fifteen tests were performed for CT scanning with no loosening of the splint and device. The arithmetic mean of the standard deviation (SD) ranged from 0.47u2009mm to 0.70u2009mm. When the device was used for registration, the mean deviations for the eight anatomical structures investigated ranged from 0.56u2009mm at the left infra-orbital foramen to 0.96u2009mm at the right temple. Compared with the method in which titanium screws are fixed to the maxillary alveolus, the target registration error (TRE) obtained using the new device was much less. Using this device, clinical reduction of a zygomatic-orbital-maxillary complex fracture was successfully completed with a registration discrepancy of less than 0.5u2009mm. Conclusions: By successfully addressing the two key issues of image guided surgery, the device could be considered accurate and potentially useful for assisting in cranio-maxillofacial surgery.

Injured condylar cartilage leads to traumatic temporomandibular joint ankylosis

PURPOSEnThe exact mechanisms of traumatic temporomandibular joint ankylosis (TTMJA) are largely unknown. In this study, we explore the role of injured condylar cartilage in the development of TTMJA.nnnMATERIAL AND METHODSnOne-month-old male mice were divided into two groups. In group 1, condylar cartilage was partially removed in the right joint using a small scissors to induce ankylosis. In group 2, condylar cartilage was completely removed in the same right joint using a small scissors to induce ankylosis. The phenotypes were observed using gross observation, micro-computed tomography scans and histological examination.nnnRESULTSnThe results revealed a great deal of ectopic cartilage and bone formation in the right periarticular region in all mice in group 1, whereas there was only a small amount of ectopic cartilage present in 26.7% of the mice in group 2. Additionally, there was stronger expression of FGF9 and weaker expression of OPN in the right temporomandibular joint region in group 2 at 7 days after surgery.nnnCONCLUSIONSnThese results suggest that the injured cartilage, not the injured bone, plays a crucial role in the development of TTMJA. In addition, it offers a useful TTMJA animal model to study the molecular mechanisms of TTMJA based on the gene manipulation technology, such as gene knock-out and knock-in as well as transgenic or gene mutation.

Effect of fiducial configuration on target registration eerror in image-guided surgery-A experiment study

This paper investigates the effect of fiducials configuration on target registration error (TRE) and test the accuracy of theoretical model of TRE prediction in image-guided cranio-maxillofacial surgery. The skull specimen is prepared with 20 titanium microscrews placed at defined locations and scanned with a 64-slice spiral computed tomography unit. These markers are separated to registration fiducial group and target fiducial group. An optical tracking system is used to perform skull-to-image registration procedures. Subsequent to each registration, the TRE is calculated by the navigation system. Each configuration have been performed registration 50 times and the average is regarded as TRE of the configuration. The TRE prediction is also calculated for each configuration. The TRE ranges from 0.58mm to 3.88mm, relatively smaller values of TRE may be achieved by placing a majority of fiducials on the maxillary alveolus in proximity about the target and placing a small number on the cranium contralaterally. The TRE values are always larger than the corresponding TRE prediction but there is high correlation between them. The configuration of fiducials is an important factor in minimizing TRE and the TRE prediction is a good guidance for fiducial markers placement.

One germline mutation of PTCH gene in a Chinese family with non-syndromic keratocystic odontogenic tumours

Keratocystic odontogenic tumours (KOCTs) are common benign cystic tumours that arise sporadically or associated with nevoid basal cell carcinoma syndrome (NBCCS). PTCH mutation can be found in sporadically or NBCCS associated KOCTs. Few PTCH mutations in families with non-syndromic KOCTs have been reported. Through PCR and gene sequence analysis, the authors discovered one missense mutation c.3277G>C in exon 19 of PTCH gene in a Chinese family with non-syndromic KOCTs. This mutation causes one highly conserved glycine residue transit to arginine on the 10th transmembrane region of PTCH protein. This work revealed that the missense mutation of PTCH is the causative and dominant gene of KOCTs in this family.

Study on 3D Reconstruction of Medical Image and Orthographic Views

D reconstruction of medical image and orthographic views provide useful information for doctors. In this paper, firstly, reconstruction of medical image based on MC (Marching cubes) algorithm is implemented using Microsoft Visual C++ and the VTK (Visualization ToolKit). Secondly, to solve the problems of huge quantities of triangle meshes and stepping effects, optimizations such as mesh simplification and mesh smoothing are presented. Finally, the method to obtain the orientation of the resliced imaging planes is presented and the orthographic views are obtained based on it. The experimental results show that optimal methods are effective and the method to get the orientation of the resliced imaging planes is practical.

Emergency removal of a grinding wheel embedded in the midface via modified Le Fort I osteotomy

Le Fort I osteotomy is commonly used to rectify craniofacial deformity in orthognathic surgery and it can be used in approaching a cranial base lesion. This technique has not been well documented in craniofacial penetrating trauma. This article describes a case of midface penetrating injury caused by a grinding wheel. A modified Le Fort I osteotomy was used to remove the foreign object. This surgical approach can be safe and effective when removing foreign bodies in the midface. Good access and adequate exposure can be achieved, which facilitate precise foreign body extraction and achieve reasonable cosmetic results.