Effects of rod stiffness and fusion mass on the adjacent segments after floating mono-segmental fusion: a study using finite element analysis.

PURPOSE: The aims of the present study were to compare the biomechanical effects on the adjacent segments after mono-segmental floating fusion with posterior semi-rigid or rigid stabilization, and to evaluate the effect of the amount of fusion mass on the biomechanical differences. METHODS: A detailed, nonlinear L1-S1 finite element model had been developed and validated. Then five models were reconstructed by different fixation techniques on the L3-L4 level: rigid fixation with an interbody spacer (Ti + IS), rigid fixation with a large interbody spacer (Ti + IS_all), semi-rigid fixation with an interbody spacer (PEEK + IS), semi-rigid fixation with a large interbody spacer (PEEK + IS_all), and semi-rigid fixation only (PEEK). Analyses were conducted for the case of erect standing position, flexion, and extension motion. RESULTS: At L1-L2 and L2-L3, PEEK + IS demonstrated less inter-segmental rotation and nucleus pressure increments from the intact model compared with Ti + IS. The L4-L5 and L5-S1 levels showed slightly higher values with PEEK + IS, but these differences among the instrumented models were not significant. The motion difference based on the fusion mass at the adjacent levels was at most 3%. All instrumentation cases generated a 55% higher facet contact force at the lower adjacent level (L4-L5) compared to that of the intact model during 26° extension and the largest increment was detected at the upper adjacent level (L2-L3) in the Ti + IS. Instrumentation with Ti + IS markedly increased the stress in the intervertebral disk at the upper adjacent level, while the stress with PEEK + IS appeared largest at the lower adjacent level. CONCLUSIONS: Posterior instrumentation with semi-rigid rods may lower the incidence of disk and facet degeneration in the upper adjacent segment compared to rigid rods. On the other hand, the possibility of facet degeneration will be similar for all instrumentation devices in the lower adjacent segment in the long-term. The stiffness difference between rigid and semi-rigid rods on the changes in the adjacent motion segments was more crucial than amount of fusion mass.

Development of inlaid electrodes for whole column electrochemical detection in HPLC.

An electrochemical microfluidic device has been fabricated on PET (polyethylene terephthalate) substrate using an imprinting method. The imprinting transfers patterns from a stamp into a substrate mechanically. However, a blanket mould imprinting process has been introduced to embed the photolithographically produced gold metal electrode lines into the PET substrate resulting in an individually addressable array flush to better than 100 nm. The device formed one wall of a packed chromatography column. The array was electrochemically characterised using standard redox probes in both stagnant conditions and under flow. Both numerical modelling and experimental data show improved sensitivity under flow and a limiting current which scaled linearly with the cube root of the volume flow rate. A chromatographic separation of the bioanalytical significant neurotransmitter dopamine (DA) and its metabolite DOPAC was achieved and electrochemically detected at multiple locations within the column. The PET device was stable and robust to leaks to pressures well in excess of those required for chromatographic separations.

Preoperative Risk Factors of C5 Nerve Root Palsy After Laminectomy and Fusion in Patients With Cervical Myelopathy: Analysis of 70 Consecutive Patients.

STUDY DESIGN: A retrospective study. OBJECTIVE: To identify preoperative risk factors causing cervical fifth nerve root palsy (C5 palsy) after laminectomy and fusion (LF). SUMMARY OF BACKGROUND DATA: It is well known that postoperative C5 palsy is not rare after cervical surgery. Although there remains controversy, C5 palsy is considered to be more common in patients who had LF than in those who had laminoplasty. However, the reason for the higher incidence of C5 palsy in patients with LF has been poorly understood. METHODS: A total of 70 consecutive patients (mean age: 60.3 y) who had LF due to cervical myelopathy were reviewed. Patients were divided on the basis of the presence (group P) or absence (group N) of C5 palsy. Among various risk factors for C5 palsy from previous reports, 6 risk factors were selected as follows: (1) preoperative low Japanese Orthopedic Association score, (2) postoperatively increased lordosis, (3) low Pavlov ratio, (4) high signal intensity in the cord at C3-C5, (5) anterior protruding mass lesion compressing the spinal cord, and (6) presence of C4-C5 foraminal stenosis. With these factors, the 2 groups were compared by statistical analysis. RESULTS: C5 palsy occurred in 10 patients (14.3%). The mean onset time was 3.5 days (range, 1-8 d) and the mean recovery time was 3.4 months (range, 1-7 mo). There were no significant differences in the preoperative Japanese Orthopedic Association score, cervical lordosis, Pavlov ratio, high signal intensity, and anterior protruding mass between the 2 groups (P>0.05). However, C4-C5 foraminal stenosis was found in 80.0% (8/10) in group P and 21.7% (13/60) in group N. There were significant differences between the 2 groups in C4-C5 foraminal stenosis (P=0.004). CONCLUSIONS: In this study, a high occurrence rate and risk factor for C5 palsy were verified after LF. Among the various factors, C4-C5 foraminal stenosis was the only risk factor for C5 palsy. Preoperative warning for C5 palsy after LF seems to be imperatively necessary, especially in patients with C4-C5 foraminal stenosis.

Childhood acute lymphoblastic leukemia with hyperleukocytosis at presentation.

BACKGROUND: Hyperleukocytosis caused by acute lymphoblastic leukemia (ALL) is associated with early morbidity and mortality due to hyperviscosity arising from the excessive number of leukocytes.This study was designed to assess the incidence of hyperleukocytosis, survival outcomes, and adverse features among pediatric ALL patients with hyperleukocytosis. METHODS: Between January 2001 and December 2010, 104 children with previously untreated ALL were enrolled at the Pusan National University Hospital. All of them were initially stratified based on the National Cancer Institute (NCI) risk; 48 (46.2%) were diagnosed with high-risk ALL. The medical charts of these patients were retrospectively reviewed. RESULTS: Twenty (19.2%) of the 104 children with ALL had initial leukocyte counts of >100×10(9)/L, and 11 patients had a leukocyte count of >200×10(9)/L. Male gender, T-cell phenotype, and massive splenomegaly were positively associated with hyperleukocytosis. Common early complications during induction therapy included renal dysfunction, and central nervous system hemorrhage. The complete remission (CR) rate for the pediatric ALL patients with hyperleukocytosis (94.1%) was similar to the overall CR rate (95.6%). The estimated 3-year event free survival (EFS) and overall survival of ALL children with hyperleukocytosis were 75.0% and 81.2%, respectively. However, patients with initial leukocyte counts >200×10(9)/L had a lower EFS than those with initial leukocyte counts 100-200×10(9)/L (63.6% vs. 100%; P=0.046). CONCLUSION: The outcome of pediatric ALL cases with an initial leukocyte count >200×10(9)/L was very poor, probably due to early toxicity-related death during induction therapy.

[Hepatitis B surface antigen and antibody positive rates of children and adolescents in Jeju].

BACKGROUND/AIMS: Korea has been an endemic area of Hepatitis B infection. Recently, the Hepatitis B carrier population has been significantly decreasing because of Hepatitis B vaccination. The aim of this study was to analyse the Hepatitis B surface antigen (HBsAg) and the Hepatitis B surface antibody (anti-HBs) positive rates of children and adolescents in Jeju. METHODS: From January 2000 to August 2002, seropositivity of HBsAg and anti-HBs were evaluated by enzyme immunoassay (EIA) in 1,653 pediatric patients. From April 2002 to August 2002, seropositivity of HBsAg and anti-HBs were evaluated by reversed passive hemagglutination (RPHA) in 2,532 students. From July 1994 to February 2003, seropositivity of HBsAg was evaluated by EIA in 1,013 pregnant women. RESULTS: The positive rates of HBsAg and anti-HBs of children and adolescents in Jeju were 2.1% and 70.9%, respectively. The positive rates of HBsAg of pregnant women in Jeju was 4.7% and that of HBeAg in HBsAg positive pregnant women was 38.1%. In children born after 1995, as age increased, HBsAg seropositivity increased significantly and anti-HBs seropositivity decreased significantly. There was no significant difference in testing HBsAg positivity between the RPHA and the EIA tests, but testing anti-HBs positivity by EIA was significantly higher than by RPHA. CONCLUSIONS: To reduce HBsAg positive rate, regular testing for anti-HBs by EIA may be indicated until at least 15 years after the primary vaccination schedule, and booster vaccination may be indicated in subjects whose anti-HBs titer was under 10 mIU/mL. 29.1% of children and adolescents in Jeju, therefore, may need to be revaccinated.