Novel Modular Spine Blocks Affect the Lumbar Spine on Finite Element Analysis.

Introduction: There are various surgical interventions to manage osteoporotic vertebral compression fracture. Modular spine block (MSB) is a novel intravertebral fixator that can be assembled. This study aimed to quantitatively investigate the force distribution in vertebrae with the various structural designs and implantation methods by finite element analysis (FEA). Methods: A three-dimensional nonlinear FEA of the L3 implanted with MSB was constructed. Different structural designs (solid vs. hollow) and implantation methods (three-layered vs. six-layered and unilateral vs. bilateral) were studied. The model was preloaded to 150 N-m before the effects of flexion, extension, torsion, and lateral bending were analyzed at the controlled ranges of motion of 20°, 15°, 8°, and 20°, respectively. The resultant intervertebral range of motion (ROM) and disk stress as well as intravertebral force distribution were analyzed at the adjacent segments. Results: The different layers of MSB provided similar stability at the adjacent segments regarding the intervertebral ROM and disk stress. Under stress tests, the force of the solid MSB was shown to be evenly distributed within the vertebrae. The maximum stress value of the unilaterally three-layered hollow MSB was generally lower than that of the bilaterally six-layered solid MSB. Conclusions: The MSB has little stress shielding effect on the intervertebral ROM and creates no additional loading to the adjacent disks. The surgeon can choose the appropriate numbers of MSB to fix vertebrae without worrying about poly(methyl methacrylate) extravasation, implant failure, or adjacent segment disease.

Finite element analysis after rod fracture of the spinal hybrid elastic rod system.

BACKGROUND: The spinal hybrid elastic (SHE) rod dynamic stabilization system can provide sufficient spine support and less adjacent segment stress. This study aimed to investigate the biomechanical effects after the internal fracture of SHE rods using finite element analysis. METHODS: A three-dimensional nonlinear finite element model was developed. The SHE rod comprises an inner nitinol stick (NS) and an outer polycarbonate urethane (PCU) shell (PS). The fracture was set at the caudal third portion of the NS, where the maximum stress occurred. The resultant intervertebral range of motion (ROM), intervertebral disc stress, facet joint contact force, screw stress, NS stress, and PCU stress were analyzed. RESULTS: When compared with the intact spine model, the overall trend was that the ROM, intervertebral disc stress, and facet joint force decreased in the implanted level and increased in the adjacent level. When compared with the Ns-I, the trend in the Ns-F decreased and remained nearly half effect. Except for torsion, the PS stress of the Ns-F increased because of the sharing of NS stress after the NS fracture. CONCLUSIONS: The study concluded the biomechanical effects still afford nearly sufficient spine support and gentle adjacent segment stress after rod fracture in a worst-case scenario of the thinnest PS of the SHE rod system.

Nanoparticle-Hydrogel Composite Drug Delivery System for Potential Ocular Applications.

Intravitreal injections are clinically established procedures in the treatment of posterior eye diseases, such as wet age-related macular degeneration (wet AMD) which requires monthly intravitreal injections of anti-vascular endothelial growth factor (anti-VEGF) protein drugs that can lead to complications due to frequent dosing. In this study, we designed a composite drug delivery system (DDS) consisting of drug-loaded poly (lactide-co-glycolide) (PLGA) nanoparticles and a chemically crosslinked hyaluronan hydrogel to reduce the dosing frequency. The morphology, size, composition, and drug loading efficiency of the prepared nanoparticles were characterized. The properties of the modified hyaluronan polymers used were also examined. The degree of swelling/degradation and controlled release ability of the hyaluronan hydrogel and the composite DDS were identified using bovine serum albumin (BSA) as a model drug. The results show that this system can retain 75% of its wet weight without losing its integrity and release the model drug at the rate of 0.4 µg/day for more than two months under physiological conditions. In addition, the nanoparticulate formulation of the system can further improve bioavailability of the drugs by penetrating deep into the retinal layers. In conclusion, the proposed composite DDS is easily prepared with biocompatible materials and is promising for providing the sustained release of the protein drugs as a better treatment for ocular neovascular diseases like wet AMD.

Less incidence of coronary artery disease in general anesthesia compared to spinal-epidural anesthesia after total knee replacement: 90-day follow-up period by a population-based dataset.

Total knee replacement (TKR) is an effective and safe procedure. However, large-scale study to compare the incidence of coronary artery disease (CAD) after spinal or epidural anesthesia (SA-EA) or general anesthesia (GA) for TKR has not ever been conducted. To do so, we studied a population-based dataset from the Taiwan National Health Research Institute and hypothesized that the incidence of CAD might be different with regional than with general anesthesia. The risk of CAD-related events during a 90-day follow-up period among patients who received TKR under SA-EA or GA was evaluated in the present study. A total of 1500 patients from the Taiwan National Health Insurance claims database who underwent TKR from January 1, 2004, to December 31, 2006, were allocated into two groups. Group 1 included 1012 patients who received SA-EA during TKR procedure. Group 2 included 488 patients who received GA during this procedure. The number of patients who developed CAD during the 90-day follow-up period was 31 (3.1 %) in group 1 and 6 (1.2 %) in group 2. The Kaplan-Meier survival analysis of IHD-free cumulative survival rate during the 90-day follow-up period for patients who underwent TKR was significantly lower in group 1 than in group 2. The hazard ratio for the occurrence of CAD was 2.80 (95 % CI 1.16-6.78), and the hazard was higher for patients who received SA-EA than for patients who received GA after adjusted potential confounding factors. After the performance of TKR, patients had a potentially increased risk for CAD in SA-EA compared to GA during the 90-day follow-up period.

Reduction of the domino effect in osteoporotic vertebral compression fractures through short-segment fixation with intravertebral expandable pillars compared to percutaneous kyphoplasty: a case control study.

BACKGROUND: Osteoporotic vertebral compression fracture is the leading cause of disability and morbidity in elderly people. Treatment of this condition remains a challenge. Osteoporotic vertebral compression fractures can be managed with various approaches, but each has limitations. In this study, we compared the clinical outcomes obtained using short-segment fixation with intravertebral expandable pillars (I-VEP) to those obtained with percutaneous kyphoplasty in patients who had suffered vertebral compression fractures. METHODS: The study included 46 patients with single-level osteoporotic thoracolumbar fractures. Twenty-two patients in Group I underwent short-segment fixation with I-VEP and 24 patients in Group II underwent kyphoplasty. All patients were evaluated pre- and postoperatively using a visual analogue scale, anterior height of the fractured vertebra, and kyphotic angle of the fractured vertebra. The latter 2 radiological parameters were measured at the adjacent segments as well. RESULTS: There was no significant difference between the groups in terms of gender or fracture level, but the mean age was greater in Group II patients (p = 0.008). At the 1-year follow-up, there were no significant differences in the visual analogue scale scores, anterior height of the fractured vertebra, or the value representing anterior height above the fractured vertebra and kyphotic angle below the fractured vertebra, after adjusting for the patients' gender, fracture level, and age. When considered separately, the anterior height below the fractured vertebra was significantly higher and the kyphotic angle above the fractured vertebra was significantly smaller in Group I than in Group II (p = 0.029 and p = 0.008, respectively). The kyphotic angle of the fractured vertebra was significantly smaller in Group II than in Group I (p < 0.001). CONCLUSIONS: In older individuals with vertebral compression fractures, kyphoplasty restored and maintained the collapsed vertebral body with less kyphotic deformity than that induced by short-segment fixation with I-VEP. Short-segment fixation with I-VEP was more effective in maintaining the integrity of adjacent segments, which prevented the domino effect often observed in patients with osteoporotic kyphotic spines.

Association between stroke and patients with pelvic inflammatory disease: a nationwide population-based study in Taiwan.

BACKGROUND AND PURPOSE: The aim of this study is to estimate the risk of stroke in a 3-year period after pelvic inflammatory disease (PID) using a nationwide population-based study. METHODS: Our study cohort consisted of all patients with a diagnosis of PID (N = 64,515) between 2004 and 2005 with a control cohort (1:2) of age-matched controls (N = 129, 030). Each patient was tracked from hospitalization until the end of 2006. Cox regressions were performed to compute the 3-year stroke-free survival rates after adjusting for possible confounding factors. RESULTS: We found that women with PID were more likely to have strokes than the control population. After adjusting for potential confounding factors, the adjusted hazard ratio of stroke was 1.63 (95% CI, 1.45-1.85) for PID patients as compared to the general population cohort. Sensitivity analysis using a bootstrap approach further ensured the validity of the results of our study. CONCLUSIONS: We concluded that patients with PID have an association with stroke. Further research is necessary to investigate the pathophysiology between PID and stroke.