Hoon Joo Yang

Interferences between mandibular proximal and distal segments in orthognathic surgery for patients with asymmetric mandibular prognathism depending on different osteotomy techniques

OBJECTIVE The aim of this study was to evaluate, using computer simulation, the amount of interference between the proximal and distal segments of the mandible incurred by 3 different osteotomy methods. STUDY DESIGN With the 3-dimensional facial computerized tomography data of 20 patients showing mandibular prognathism with asymmetry, simulation surgeries of conventional sagittal split ramus osteotomy (SSRO), intraoral vertical ramus osteotomy (IVRO), or short lingual osteotomy (SLO) was performed. The distal segments were moved backward (3, 6, or 9 mm) and rotated (2 degrees, 4 degrees, or 6 degrees). The amounts of interference between the proximal and distal segments of the mandible were measured and statistically analyzed. RESULTS Conventional SSRO demonstrated the greatest interference between the proximal and distal segments of the mandibles (P < .01), followed by IVRO and SLO. SLO showed less interference than IVRO in mild asymmetry cases (P < .05), but no difference was noted in severe prognathism and asymmetry cases. CONCLUSION SLO is the most favorable osteotomy method for reducing displacement of the proximal segment in mandibular prognathism with asymmetry.

Three-dimensional natural head position reproduction using a single facial photograph based on the POSIT method

We developed a new method to record and reproduce the three-dimensional natural head position (NHP) from a single photograph of a patients face using a pose from orthography and scaling with iterations (POSIT) algorithm. We attached 4-mm spherical ceramic markers to the patients face as feature points. A frontal photograph of the patients NHP was taken using an ordinary digital camera parallel to the global horizon. Computed tomography (CT) was then performed on the patient with the markers. The ceramic marker positions were determined in the 2D image and corresponded to points in the 3D model. The 3D rotation matrix determined using the feature points via the POSIT method was applied to the CT model to reproduce the NHP. A skull phantom was used to evaluate the accuracy and reproducibility of the developed method. The degree difference (°) between the true and POSIT orientations in the roll, pitch, and yaw directions was quantified as the error. The mean accuracy was -0.04 ± 0.15°, -0.17 ± 0.50°, and -0.02 ± 0.37° in the roll, pitch, and yaw directions, respectively. The method developed was highly reproducible during intra-observer and inter-observer variation analyses. The accuracy of the method was clinically acceptable, and the procedure was time- and cost-effective. This method is accurate and inexpensive; additionally, it does not affect the patients lip position, and we expect it to be routinely used during orthognathic surgery.

Bone mineral density and mandibular advancement as contributing factors for postoperative relapse after orthognathic surgery in patients with preoperative idiopathic condylar resorption: a prospective study with preliminary 1-year follow-up

OBJECTIVES The aim of this study was to analyze contributing factors for postoperative relapse after orthognathic surgery in patients with preoperative idiopathic condylar resorption (ICR). STUDY DESIGN Sixteen female patients with mandibular retrognathism and ICR were included in this prospective study. For patient factors, serum 17 β-estradiol (E2), bone mineral density, and the preoperative posterior condylar inclination were evaluated. Bone mineral density was measured using dual-energy x-ray absorptiometry (DEXA) bone densitometry and expressed by T-score. Surgical changes and postoperative relapse were measured with cephalometric analysis. The correlation between postoperative relapse and measured parameters was statistically analyzed. RESULTS The lowest T-score exhibited a significant correlation with postoperative clockwise rotation and posterior relapse tendency of the mandible (P < .05). The amount of mandibular advancement showed a significant correlation with the postoperative clockwise rotation of the mandible (P < .05). CONCLUSIONS The postoperative relapse tendency in patients with preoperative ICR is significantly related to the lowest T-score and the amount of mandibular advancement.

Postoperative stability following maxillary downward movement with Le Fort I inclined osteotomy at the lateral nasal cavity wall.

Downward movement of the maxilla is regarded as one of the less stable long-term orthognathic surgical procedures. To increase postoperative stability with direct bone contact, the conventional Le Fort I osteotomy was modified with an inclined osteotomy at the lateral nasal cavity wall. The aim of this study was to evaluate the postoperative stability of the new method for Le Fort I inclined osteotomy for downward maxillary movement. The study included 27 patients with anterior vertical deficiency of the maxilla who underwent Le Fort I inclined osteotomy for downward maxillary movement. Patients were classified into two groups according to the amount of downward movement. The amounts of relapse (cephalometric changes) of the two groups were compared and statistically analyzed. The mean amount of relapse was about 1 mm. The tendency of relapse was not increased by a large initial downward movement with Le Fort I inclined osteotomy. Le Fort I inclined osteotomy was used safely for downward movement in order to increase bone height at the piriform aperture area and resulted in direct bone contact, suggesting it is a useful technique for maintaining postoperative stability. A further study with a larger number of patients is necessary.

An integrated orthognathic surgery system for virtual planning and image-guided transfer without intermediate splint

Accurate surgical planning and transfer of the planning in orthognathic surgery are very important in achieving a successful surgical outcome with appropriate improvement. Conventionally, the paper surgery is performed based on a 2D cephalometric radiograph, and the results are expressed using cast models and an articulator. We developed an integrated orthognathic surgery system with 3D virtual planning and image-guided transfer. The maxillary surgery of orthognathic patients was planned virtually, and the planning results were transferred to the cast model by image guidance. During virtual planning, the displacement of the reference points was confirmed by the displacement from conventional paper surgery at each procedure. The results of virtual surgery were transferred to the physical cast models directly through image guidance. The root mean square (RMS) difference between virtual surgery and conventional model surgery was 0.75 ± 0.51 mm for 12 patients. The RMS difference between virtual surgery and image-guidance results was 0.78 ± 0.52 mm, which showed no significant difference from the difference of conventional model surgery. The image-guided orthognathic surgery system integrated with virtual planning will replace physical model surgical planning and enable transfer of the virtual planning directly without the need for an intermediate splint.

Estrogen modulates BMP-induced sclerostin expression via the Wnt signaling pathway

Clinical data show that estrogen levels are inversely associated with the production of sclerostin, a Wnt antagonist that recently attracted great attention over the use of its antibody in the anabolic treatment of osteoporotic conditions. However, the molecular link between sclerostin expression and estrogen signaling is not yet known. We investigated the mechanisms by which estrogen modulates sclerostin (SOST) gene expression at the cellular level in human osteoblast cells in association with bone morphogenetic protein (BMP)2 signaling given that BMP2 is a potential inducer of SOST in human mesenchymal stromal cells (hMSCs). 17β-Estradiol (E2) alone had no effect on SOST expression, which was significantly induced by treatment with BMP2 in hMSCs and osteoblasts derived from the mandibles of female donors. However, E2 suppressed the induction of SOST and other BMP2 target genes by BMP2 in hMSCs. E2 signaling was independent of the Smad pathway, which plays a critical role in SOST induction mediated by BMP2. Instead, E2 increased the transcriptional expression of β-catenin and levels of its activated form. Silencing of the gene encoding estrogen receptor (ER)α decreased E2 activity in β-catenin activation and the suppression of SOST induction by BMP2, but had no influence on BMP2-mediated SOST induction in the same conditions. Similar results were obtained after treatment with ERα antagonist as a Wnt inhibitor. In human osteoblasts, the effect of E2 on SOST expression was either suppressive or absent, depending on the cell donor. Interestingly, the SOST expression pattern after treatment with BMP2 or BMP2/E2 in human osteoblasts showing a pattern of E2 suppression on SOST induction by BMP2 correlated with the ratio of receptor activator of nuclear factor kappa-B ligand (RANKL) to osteoprotegerin (OPG) expression. These results demonstrate that estrogen signaling in osteoblasts negatively regulates SOST expression in an indirect manner through interaction with BMP2 signaling and that this regulation involves the Wnt/ERα and β-catenin pathways. This study highlights several interactions between estrogen and BMP cascades in osteoblasts that may provide a basis for therapeutic intervention for the modification of bone mass density.

Comparison of whole blood collection and double-unit erythrocytapheresis in preoperative autologous blood donation

INTRODUCTION We compared preoperative autologous blood donation (PABD) using serial manual whole blood (WB) and PABD using a single session, double-unit erythrocytapheresis in terms of the hemodynamic recovery and clinical outcomes. MATERIALS AND METHODS This study included 56 donors in the WB PABD group and 117 donors in the double-unit erythrocytapheresis PABD group. All subjects were men with body weight >70 kg, Hb level >13.3g/dL, Hct >40%, and who were scheduled for oral and maxillofacial surgery. Three cycles of manual WB collection for PABD or a single session, double-unit erythrocytapheresis using the Alyx was performed. RESULTS There were no significant differences in donor demographic variables including age, height, weight, Hb, Hct, or red cell mass between the 2 groups. The double-unit erythrocytapheresis was completed earlier than the last manual WB PABD (at 15.3 ± 4.7 days and 6.5 ± 3.2 days before surgery, p<0.001). Hct values before surgery were higher in the double-unit erythrocytapheresis PABD group than in the manual WB PABD group (39.7 ± 3.2 vs. 38.6 ± 2.7, p=0.024). ΔHct and %ΔHct before the first PABD and before surgery were lower in the double-unit erythrocytapheresis PABD group than in the manual WB PABD group (-5.6 ± 2.8 vs. -6.8 ± 2.7, p=0.010 and -12.3 ± 5.9 vs. -14.8 ± 5.6, p=0.008, respectively). The incidence of additional allogeneic blood transfusions during or after surgery and the post-operative Hb and Hct values were similar in the 2 groups. The length of hospital stay after surgery was significantly longer in the manual WB PABD group than in the double-unit erythrocytapheresis group (6.1 ± 2.5 vs. 5.4 ± 1.9, p=0.043). Of the 33 donors in the double-unit erythrocytapheresis PABD group, 7 (21.2%) reported discomforts related to the procedure, and 6 graded the discomforts (hypocalcemia, perioral tingling sense, paresthesia, dizziness, stuffiness, pain on the intravenous site, and muscle tension) as mild. CONCLUSION The single session, double-unit erythrocytapheresis prolonged the time interval between PABD and surgery and led to better hemodynamic recovery than the serial manual WB PABD, and hypocalcemic symptoms were mild.

Pulsed Electromagnetic Fields Enhance Bone Morphogenetic Protein-2 Dependent-Bone Regeneration.

The use of recombinant human bone morphogenetic protein-2 (rhBMP-2) for the purpose of promoting bone regeneration is emerging; however, the high dose of rhBMP-2 required in humans is accompanied by several limitations, including bone resorption and swelling. To reduce the dose of rhBMP-2 required, the applicability of pulsed electromagnetic fields (PEMF) was evaluated using a rat calvarial defect model. After creating an 8-mm-diameter calvarial bone defect, a collagen sponge soaked in different concentrations (0, 2.5, 5, 10 μg) of rhBMP-2 was implanted at the defect area. One week after surgery, PEMF was applied for 8 h/day over 5 days in an experimental group of animals (n = 28) using a width of 12 μs, a pulse frequency of 60 Hz, and a magnetic intensity of 10 G. Animals were sacrificed 4 weeks after surgery and assessed by microcomputed tomography and histological and immunohistochemical analyses. In the absence of application of PEMF, bone volume, bone mineral density, trabecular thickness, trabecular number, and trabecular separation, all showed statistically significant differences, depending on the concentration of rhBMP-2 utilized (p < 0.001). PEMF accelerated bone regeneration in the groups that received 0, 2.5, and 5 μg rhBMP-2 (p < 0.05). In contrast, administration of 10 μg rhBMP-2 resulted in no additive effect on bone regeneration in combination with PEMF. Groups receiving no rhBMP-2 showed distinct bone regeneration in the central zone of the bone defect when treated with PEMF, whereas they failed to bridge the defect space without PEMF. Among the groups without PEMF, soft tissue infiltrations from the outer surface on the skin side were common. Among groups with PEMF, the groups receiving 5 and 10 μg rhBMP-2 displayed denser bone with significantly reduced dead spaces. The application of PEMF did not result in an accelerated effect on bone regeneration in groups treated with 10 μg rhBMP-2. Therefore, our data demonstrate that PEMF can promote bone regeneration in animals treated with a low concentration of rhBMP-2.

Osseous alterations in the condylar head after unilateral surgical directional change in rabbit mandibular condyles: Preliminary study

The purpose of this study was to investigate bony changes in the mandibular condyle when the surface not normally subjected to masticatory forces was subjected to functional loading using a unilateral surgical experiment. Fifteen male New Zealand white rabbits, divided into two groups, were used. Oblique vertical body osteotomies of the mandible and counterclockwise rotation (CCWR) of the proximal segment (PS) [six with 1 mm (group I), six with 3 mm (group II)] were performed on the right side. Osseous changes of condyles were analyzed using micro-computed tomography and histological evaluation four weeks postoperatively. The comparison was performed between condyles on the right and left sides. Since the left condyle (control) might be affected by the operation on the right side, the results were also compared with the healthy control (group III, n = 3, 6 condyles). CCWR of the PS led to osteoporotic changes of the condyle including significantly reduced bone volume and bone mineral density (p < 0.05), thin and small number of trabeculae (p < 0.05). In addition, thinning of condylar cartilage and reduced density of cartilaginous cells were observed. However, these changes were not affected by the amount of CCWR of the PS.

Aesthetic closure of the donor site of a radial forearm free flap with two local curved skin grafts

Abstract The authors have designed an aesthetic and effective coverage technique using local curved skin grafts along with vascular pedicles without additional skin incisions to solve the disadvantages of skin coverage problem of donor site defect after radial forearm free flap (RFFF) harvesting. This has, to the authors’ knowledge, not been previously described.