Biomechanical comparison of occipitoatlantal screw fixation techniques

OBJECT: The stability provided by 3 occipitoatlantal fixation techniques (occiput [Oc]-C1 transarticular screws, occipital keel screws rigidly interconnected with C-1 lateral mass screws, and suboccipital/sublaminar wired contoured rod) were compared. METHODS: Seven human cadaveric specimens received transarticular screws and 7 received occipital keel-C1 lateral mass screws. All specimens later underwent contoured rod fixation. All conditions were studied with and without placement of a structural graft wired between the skull base and C-1 lamina. Specimens were loaded quasistatically using pure moments to induce flexion, extension, lateral bending, and axial rotation while recording segmental motion optoelectronically. Flexibility was measured immediately postoperatively and after 10,000 cycles of fatigue. RESULTS: Application of Oc-C1 transarticular screws, with a wired graft, reduced the mean range of motion (ROM) to 3% of normal. Occipital keel-C1 lateral mass screws (also with graft) offered less stability than transarticular screws during extension and lateral bending (p < 0.02), reducing ROM to 17% of normal. The wired contoured rod reduced motion to 31% of normal, providing significantly less stability than either screw fixation technique. Fatigue increased motion in constructs fitted with transarticular screws, keel screws/lateral mass screw constructs, and contoured wired rods, by means of 19, 5, and 26%, respectively. In all constructs, adding a structural graft significantly improved stability, but the extent depended on the loading direction. CONCLUSIONS: Assuming the presence of mild C1-2 instability, Oc-C1 transarticular screws and occipital keel-C1 lateral mass screws are approximately equivalent in performance for occipitoatlantal stabilization in promoting fusion. A posteriorly wired contoured rod is less likely to provide a good fusion environment because of less stabilizing potential and a greater likelihood of loosening with fatigue.     

Vesicovaginal fistula repair with genito-gluteal fold fat pad flap.

We report our experience of supratrigonal vesicovaginal fistula (VVF) repair cases developed after gynaecologic surgery. Two patients presented with urinary incontinence after hysterectomy and adjuvant radiation therapy for cervical carcinoma. Cystoscopy findings showed vesicovaginal fistula near the bladder neck area. In a transvaginal approach, we excised the fistulous tract and transferred the genito-gluteal fold fat pad flap for interpositioning. Postoperative cystography showed no evidence of leakage and no recurrence was found after a 1 year follow-up period. This flap technique is particularly useful for a vaginal cuff area fistula in terms of ease of dissection, lower donor site morbidity and large flap dimension. Also the fat pad provides neovascularity and lymphatic drainage, fills dead space, and enhances granulation tissue formation.     

Biological Advantages of Porous Hydroxyapatite Scaffold Made by Solid Freeform Fabrication for Bone Tissue Regeneration

Presently, commercially available porous bone substitutes are manufactured by the sacrificial template method, direct foaming method, and polymer replication method (PRM). However, current manufacturing methods provide only the simplest form of the bone scaffold and cannot easily control pore size. Recent developments in medical imaging technology, computer‐aided design, and solid freeform fabrication (SFF), have made it possible to accurately produce porous synthetic bone scaffolds to fit the defected bone shape. Porous scaffolds were fabricated by SFF and PRM for a comparison of physical and mechanical properties of scaffold. The suggested three‐dimensional model has interconnected cubic pores of 500 μm and its calculated porosity is 25%. Whereas hydroxyapatite scaffolds fabricated by SFF had connective macropores, those by PRM formed a closed pore external surface with internally interconnected pores. SFF was supposed to be a proper method for fabricating an interconnected macroporous network. Biocompatibility was confirmed by testing the cytotoxicity, hemolysis, irritation, sensitization, and implantation. In summary, the aim was to verify the safety and efficacy of the scaffolds by biomechanical and biological tests with the hope that this research could promote the feasibility of using the scaffolds as a bone substitute.     

Finite Element Modeling of Stress Distribution in Intervertebral Spacers of Different Surface Geometries

Intervertebral disc spacers using bioactive ceramics have been used to treat degenerative spinal disease. Tooth‐shaped spacers are commonly used to prevent migration, but there is a possibility of fracture when inserted or after insertion. Intervertebral disc spacers with either an isosceles triangle‐shaped tooth (T1) or a right triangle‐shaped tooth (T2) were used as a control group. The design factors for the experimental group were modified to prevent fractures induced by stress concentration, and the surfaces of the spacers were designed as either an isosceles triangle‐shaped valley (V1) or a right triangle‐shaped valley (V2). Linear analysis using finite element model (FEM) was performed, and Von Mises stress distribution was calculated by applying 1000 N of uniformly distributed load. Samples of the V2 design were made with bioactive glass‐ceramics (BGS‐7) and evaluated for compressive strength, fatigue degree, and impact strength. Von Mises stress was highest at the first tooth from the posterior side for the control group and at the center for the experimental group. Compared with the control group, the experimental group showed 18.4% and 82.5% reduction (V1 vs. T1 and V2 vs. T2, respectively) in the maximum stress at the bottom of the valleys. The FEM analysis revealed that the V2 design had the most even load distribution. The V2 samples with bioactive glass‐ceramics were evaluated for compressive strength, and all six samples were not fractured up to 24 000 N. However, the average impact strength was 19.42 kN, suggesting that momentary force caused damage at a lower load than compression with a steady speed. The BGS‐7 intervertebral disc spacer with V2 design was not fractured during the fatigue test at maximum pressure of 8000 N, R ≥10, 5 Hz, and 5 million cycles. These data confirm that the BGS‐7 spacer with the V2 design may be clinically applicable. Collectively, the modified surface geometry of the experimental group significantly lowered Von Mises stress values at the bottom of the valleys, and thus the possibility of fracture by compressive load was greatly reduced. Also, impact during insertion was confirmed to cause fracture more easily, as the impact strength was lower than the compressive strength in the experimental group.     

Leucine‐rich glioma inactivated 3 promotes HaCaT keratinocyte migration

Our finding that human skin expresses leucine‐rich glioma inactivated 3 (LGI3) raises the question of the function of this cytokine in keratinocytes. We have shown that LGI3 stimulates human HaCaT keratinocyte migration without affecting viability or proliferation. Western blot analysis showed that LGI3 induced focal adhesion kinase activation, Akt phosphorylation, and glycogen synthase kinase 3β (GSK3β) phosphorylation in these cells. Using the scratch wound assay and a modified Boyden chamber, we found that LY294002, a selective phosphatidylinositol 3‐kinase inhibitor, and LiCl, a selective GSK3β inhibitor, abolished LGI3‐induced cell migration. We tested β‐catenin levels after LGI3 treatment because the Akt‐GSK3β pathway regulates β‐catenin accumulation, and β‐catenin promotes cell migration. LGI3 treatment increased β‐catenin protein and nuclear localization, whereas LY294002 prevented LGI3‐induced focal adhesion kinase and Akt activation as well as β‐catenin accumulation. Overall, these data suggest that LGI3 stimulates HaCaT cell migration following β‐catenin accumulation through the Akt pathway.     

Periciliary Y-V epicanthoplasty

The epicanthal fold is a semilunar flap of eyelid skin on the medial aspect of the eye. Many surgical techniques have been described to eliminate the epicanthal fold, which is a feature uniquely predominant among the Asian population. However, many surgeons avoid epicanthoplasty because of the fear of visible scar formation. From January of 2002 to April of 2004, 118 patients with medial epicanthal folds underwent epicanthoplasty using a periciliary Y-V advancement procedure for the prevention of visible scar formation. The mean age of the patients was 25.2 years (range, 16 years to 56 years). The median follow-up period was 6 months (range, 2 weeks to 2 years). We performed periciliary Y-V epicanthoplasty only when a patient had wide interepicanthal distance (over 32 mm) or a completely eclipsed lacrimal caruncle.Most of the patients attained satisfactory results, and there were few complications in our cases. Scarring of the medial canthal area has not been a problem with this technique because we designed incisions along the eyelashes and skin-mucosal junctions. We have found that our periciliary Y-V epicanthoplasty is a very reliable and effective method for eliminating the epicanthal fold with minimal scar formation.     

Change in brow position after upper blepharoplasty or levator advancement

Brow position after blepharoplasty is somewhat controversial. Some authors insist that brow position remains unchanged after surgery. On the other hand, there is also an opinion that brow position changes after surgery.We evaluate the influence of upper blepharoplasty or correction of ptosis on brow position in East Asians. Sixty patients (120 eyes) who underwent upper blepharoplasty or levator advancement were evaluated for change in brow position. Marginal reflex distance 1, brow height from medial canthus, upper eyelid margin on midpupillary level, lateral canthus, and brow height from the center of the pupil were measured before surgery and 6 months after surgery. The distance between the upper lid margin and the brow was shortened after upper blepharoplasty or levator advancement, which could cause brow depression. Change in brow height was greater after levator advancement than after blepharoplasty. These findings might be helpful for the prediction of brow position after surgery. Our study also implies that the possibility of a change in postoperative brow position change should be explained to patients before surgery, particularly ptosis patients.     

p53 in cutaneous melanoma: Immunoreactivity and correlation with prognosis

p53 protein immunoreactivity was investigated in cutaneous Spitz naevi (n= 7), superficial spreading (n= 21) and nodular (n= 6) melanomas using the monoclonal antibody DO-7. Nuclear immunostaining for p53 protein was observed in 41% of all the melanomas but not in any of the Spitz naevi studied. This difference in p53 immunoreactivity appeared statistically significant (P= 0.0001; χ² test). There were also differences in p53 immunoreactivity between superficial spreading and nodular melanomas (P= 0.001, χ² test), where up to 38% of superficial spreading melanomas and 50% of nodular melanomas had demonstrated p53 nuclear immunostaining. An apparently significant correlation was observed between melanomas with poor prognostic histological indices and p53 immunoreactivity (P= 0.0016; χ² test). In conclusion, increased p53 protein immunoreactivity is found in melanomas and is associated with poorer prognosis. The differences in p53 immunohistological expression between cutaneous melanomas and Spitz naevi suggest that alterations of the protein may be important in the pathogenesis of the tumour.