Biomedical subjects

V Yeow

Publications and source records attributed to V Yeow.

6 recordsLinked to original sources

PubMed2002

[Endoscopically assisted Le Fort 1 osteotomy: a study in human cadaver heads].

METHODS AND RESULTS: Endoscopically assisted Le Fort 1-osteotomy was performed in a cadaver study with six human skulls. Vertical incisions were used to approach the maxilla using the endoscope. The bone cuts could be carried out with a 4-mm osteotome preserving the buccal mucosa. The downfracture of the maxilla was accomplished without damaging the descending palatal arteries, which could be verified endoscopically. Rigid fixation was performed using 1.5-mm titanium plates (Synthes, Mathys AG, Bettlach, Switzerland) and self-drilling screws. DISCUSSION: This cadaver study showed that the Le Fort 1 osteotomy could be carried out through limited approaches using endoscopic techniques and self-drilling fixation tools. Further experimental work and improvements will help to introduce this technique into clinical application.

Bone Plates↗

PubMed2002

[Individually CAD-CAM technique designed, bioresorbable 3-dimensional polycaprolactone framework for experimental reconstruction of craniofacial defects in the pig].

METHODS: Twenty orbital defects (2 x 2 cm) were created in ten adult Yorkshire pigs. Two software products (Velocity and Mimix) were evaluated with regard to image processing, three-dimensional reconstruction, and fabrication of individually shaped polycaprolactone (PCL) scaffolds to reconstruct these defects. Four different techniques were tested for the reconstruction: group 1 = no reconstruction, group 2 = polylactide sheet, group 3 = PCL scaffold, group 4 = bone marrow-coated PCL scaffold. The pigs were sacrificed at 3 months. RESULTS: In group 1 soft tissue scar formation could be found, but without any new bone. Group 2 showed a thick fibrous capsule around the PLLA sheet, whereas at the border zone of the defect signs of new bone formation could be detected. In group 3 the PCL scaffolds were filled with fibrous tissue and some areas that showed new bone formation (6.4% of the area of the defect). In group 4 the new bone formation (17.8% of the area of the defect) was significantly higher in quantity than in group 3. CONCLUSION: The PCL scaffold coated with bone marrow seems to be a material that effectively provides osteoinduction with formation of new bone. Long-term results at 12 months are still pending.

Absorbable Implants↗

PubMed2001

Endoscopically assisted Le Fort I osteotomy.

OBJECTIVES: A new technique of the Le Fort I osteotomy using endoscopic techniques through limited approaches has been evaluated. PATIENTS: This technique was first carried out successfully in a study on six cadavers. Thereafter we performed endoscopically assisted Le Fort l osteotomy in two patients. METHODS: Four vertical incisions were used in the vestibule (paranasally and posteriorly) as approaches. The endoscope allowed direct visualization of the osteotomy of the maxilla including the pterygomaxillary junction. The osteotomies could be accomplished with a straight 4 mm osteotome for medial and lateral antral walls and nasal septum and a curved osteotome for the pterygomaxillary junction. RESULTS: The procedures were successful. The descending palatal arteries could be preserved in all cases as a result of endoscopic control. Rigid fixation of the downfractured maxillae was carried out using self-drilling titanium screws and plates. CONCLUSION: Endoscopic visualization allowed safe osteotomy of the medial antral wall preserving the descending palatal artery in all cases and hence less bleeding. Postoperative oedema and swelling in the two clinical cases was definitely reduced when compared with the conventional technique. The time needed for these first two clinical cases was approximately 1 h 30 min, i.e., about 30 min more than with the open technique. Further experience and experimental work, and refinements in technique will help to improve this procedure in its clinical application.

Adult↗

PubMed2001

Repair of composite zygomatico-maxillary defects with free bone grafts and free vascularized tissue transfer.

INTRODUCTION: Three-dimensional repair of the zygomatico-maxillary defect calls for an elaborate technique to achieve facial symmetry and correct globe position. We present a technique, which combines the use of a free vascularized soft tissue flap and free bone grafts for repair of composite zygomatico-maxillary defects. PATIENTS: Three patients that underwent radical resection of the maxilla and the zygoma have undergone facial reconstruction using this technique. The mean follow up was 9 months. METHODS: The key points of this technique are: (1) precise reconstruction of the zygomatico-maxillary complex including the orbit; (2) creation of a skeletal framework for canthopexy and suspension of the free flap; (3) repair of through-and-through soft tissue defects with a folded musculocutaneous free flap; and (4) simultaneous harvesting and reconstruction using two surgical teams to reduce the duration of surgery. RESULTS: Reconstruction of the zygomatico-maxillary complex could be successfully accomplished in a single surgical procedure. CONCLUSION: This paper presents a method of repairing zygomatico-maxillary defects with free bone grafts and vascularized soft tissue. However, this concept has yet to be reviewed in the long term.

Aged↗

PubMed1999

Establishment of animal models using experimental rats for allogeneic tissue transplantation and quantitative flow cytometric detection of immunochimera.

Establishment of animal models used for allogeneic tissue transplantation, MHC phenotyping as well as quantitative detection of immunochimera were carried out in this study. Both Buffalo (BUF) and Lewis (LEW) rats were chosen as the target animals. The rats were treated with single dose cyclophosphamide (Cy) of 25 to 100 mg/kg to mimic the standard conditioning therapy. Total white blood cells (WBC) were monitored daily for up to 8 days: WBC reached the nadir by day 4 and started to recover by day 5 with an obvious rebounce at day 7 of Cy treatment. Flow cytometric techniques were used to determine the haplotypes of the major histocompatibility complex (MHC) as well as quantitative detection of immunochimerism in unfractionated rat WBC. Monoclonal antibodies against the rat class-I MHC antigens RT1Aab and RT1Au were used to label the class-I MHC antigens on total rat WBC. The results showed that the BUF rats were positive for both RT1Aab and RT1Au antigens, whilst the LEW rats were negative for both. Immunochimera was mimicked in vitro by serial dilution, ranging from 1/1 to 1/10(5) of (BUF/LEW) WBC. A sensitivity of 1/10(4) (BUF/LEW WBC) was achieved. The results showed that there were at least 2 major MHC mismatched loci between BUF and LEW rats and flow cytometry provided a sensitive method for the detection of immunochimera in unfractionated rat WBC. We concluded from this study that both strains of rats could be used as models for allogeneic tissue transplantation across at least two major MHC-mismatches. The sensitivity of flow cytometric method was satisfactory for the detection of immunochimera.

Animals↗

PubMed1998

Ecthyma gangrenosum in a patient with hypogammaglobulinemia.

Ecthyma gangrenosum is a characteristic skin lesion that is caused by Pseudomonas aeruginosa (P. aeruginosa) in the majority of cases. Systemic P. aeruginosa usually complicates debilitating conditions like leukaemia, burns and cystic fibrosis. We report a patient with underlying hypogammaglobulinemia who developed ecthyma gangrenosum secondary to P. aeruginosa septicaemia, which was potentially life-threatening. Recognition of the characteristic skin lesions with prompt initiation of appropriate antibiotics and intravenous immunoglobulins were life-saving. A review of the English literature reports three other cases of ecthyma gangrenosum in patients with underlying hypogammaglobulinemia.

Agammaglobulinemia↗