Augmentation of mechanical properties in osteoporotic vertebral bones – a biomechanical investigation of vertebroplasty efficacy with different bone cements

Recent clinical trials have reported favorable early results for transpedicular vertebral cement reinforcement of osteoporotic vertebral insufficiencies. There is, however, a lack of basic data on the application, safety and biomechanical efficacy of materials such as polymethyl-methacrylate (PMMA) and calciumphospate (CaP) cements. The present study analyzed 33 vertebral pairs from five human cadaver spines. Thirty-nine vertebrae were osteoporotic (bone mineral density < 0.75 g/cm2), 27 showed nearly normal values. The cranial vertebra of each pair was augmented with either PMMA (Palacos E-Flow) or experimental brushite cement (EBC), with the caudal vertebra as a control. PMMA and EBC were easy to inject, and vertebral fillings of 20-50% were achieved. The maximal possible filling was inversely correlated to the bone mineral density (BMD) values. Cement extrusion into the spinal canal was observed in 12% of cases. All specimens were subjected to axial compression tests in a displacement-controlled mode. From load-displacement curves, the stiffness, S, and the maximal force before failure, Fmax, were determined. Compared with the native control vertebrae, a statistically significant increase in vertebral stiffness and Fmax was observed by the augmentation. With PMMA the stiffness increased by 174% (P = 0.018) and Fmax by 195% (P = 0.001); the corresponding augmentation with EBC was 120% (P = 0.03) and 113% (P = 0.002). The lower the initial BMD, the more pronounced was the augmentation effect. Both PMMA and EBC augmentation reliably and significantly raised the stiffness and maximal tolerable force until failure in osteoporotic vertebral bodies. In non-porotic specimens, no significant increase was achieved.     

Pathological Processing Techniques and Final Diagnosis of Breast Cancer Sentinel Lymph Nodes

Background

Recommendations for intraoperative and postoperative breast sentinel lymph node (SLN) processing differ widely. Micrometastases and isolated tumor cells (ITC) have recently been proposed as prognostically and therapeutically relevant. We compared 3 SLN protocols with regard to intraoperative and postoperative diagnosis.

Materials and Methods

SLN in cohort I (270 patients) were intraoperatively assessed by stereomicroscopy. Intraoperative frozen section (IFS) was used only in stereomicroscopically suspicious SLN. In cohort II (197 patients), all SLN were examined with only 1 IFS. Final SLN workup in cohorts I and II consisted of complete step sectioning with immunohistochemistry. In cohort III (268 patients) 2 or more IFS were performed followed by 3 step sections and immunohistochemistry.

Results

pN1 stages were significantly higher in cohorts I and II (33.3% and 34.0% respectively) than in cohort III (24.6%). Intraoperative false negativity for the detection of metastases (pN1) ranged from 54.4% (cohort I) and 35.8% (cohort II) to 21.2% (cohort III). In contrast, ITC were detected significantly more frequently in cohort I (9.3%) and cohort II (14.7%) than in cohort III (1.9%).

Conclusions

Higher rates of SLN metastases and ITC in cohort I/II compared to cohort III suggest that IFS may result in tissue loss thus increasing the risk of missing metastases. Sparse IFS but complete postoperative SLN workup with step sectioning and immunohistochemistry provides more accurate information regarding minimal disease in SLN, but often results in delayed axillary lymph node dissection. This is important for preoperative patient information and recommendations in SLN processing protocols.     

Calcineurin inhibitor dose‐finding before kidney transplantation in HIV patients

Kidney transplantation in HIV‐infected patients is associated with a higher rate of graft rejection as well as an increased toxicity of the immunosuppressive therapy. Specifically, the use of the calcineurin inhibitor tacrolimus is problematic because of a narrow therapeutic range, a high interindividual variability of trough levels, and multiple interactions with combination antiretroviral therapy (cART). Our objective was to establish the optimal individual immunosuppressive dose for the time after kidney transplantation. We administered a temporary course of immunosuppressive therapy in three HIV‐infected patients with end‐stage renal disease (ESRD) after wait‐listing and prior to transplantation for deceased donor kidney transplantation. Starting with a tacrolimus dose of 1 mg twice daily, the dose was titrated to reach a tacrolimus trough level of 8–12 ng/ml. HIV had been diagnosed 7–14 years prior. All patients had no detectable HIV‐1 RNA while on cART. All three patients had been on chronic dialysis for 4, 7, and 10 years. In two patients, the intended tacrolimus trough levels of 8–12 ng/ml were achieved within a month. The required tacrolimus dose ranged from 0.5 mg thrice weekly to 10 mg daily. In one case, ventricular tachycardia occurred, so the immunosuppressive therapy was switched to cyclosporine A. So far, two patients have been transplanted successfully. In summary, dose‐finding of immunosuppressive therapy with tacrolimus in patients on cART before renal transplantation is feasible and appears useful to minimize immunosuppressive therapy‐related complications in the post‐transplantation period.     

Applicability of strain measurements on a contra angle handpiece for the determination of alveolar bone quality during dental implant surgery

Alveolar bone quality is considered to be an important prognostic factor in dental implant stability. Although numerous methods have been described, no technique allows for reliable diagnostics. The purpose of this study was to determine if strain measurements on the shaft of a contra angle handpiece during implant bed preparation could be used for the determination of bone quality. Experiments in polyurethane foam and human cadaver bone were conducted to investigate whether strain measurements could be correlated with other diagnostic parameters, such as the surgeon's tactile sensation during drilling, implant insertion torque, implant stability, elastic modulus of bone and bone quality as assessed radiographically. Tests were also performed to determine if strain measurements could be used to distinguish various types of bone. As axial feed and contact pressure during the drilling process could not be standardized under simulated clinical conditions, substantial deviations in the time needed to complete the drilling occurred. Under controlled circumstances using polyurethane foam, this problem could be addressed by a normalization procedure, but great variations occurred in human cadaver bone. As bone quality could not be reliably determined, especially when a cortical layer was present, strain measurements on a contra angle handpiece appears to be inappropriate for this purpose.     

Effects of the helium-neon laser on rat kidney epithelial cells in culture

The cellular mechanisms of action of low power lasers are only partially understood. Therefore, we have studied effects of helium-neon (He−Ne) laser irradiation in a cell culture model. The studies were performed with the permanent rat kidney cell line RK-L. By electron microscopy, significant ultrastructural changes of the cells were seen after He−Ne irradiation at 40 mW/cm² for 4h (569 J/cm²), including detritus-like formations of the cell organelles close to the nucleus. While such changes were not observed after 1 h irradiation (142 J/cm²), the number of cells in mitosis increased under this condition. In addition, the rate of incorporation of³H-thymidine into DNA decreased transiently 6–9 h after 1 h He−Ne irradiation of the cells. The consumption of glucose was also lowered for 10 h after irradiation, while the production of lactate increased. Finally, the synthesis of prostaglandin E₂ was reduced following irradiation. These results show that the He−Ne laser induces significant effects at the cellular level. In addition, our findings support the concept that the biological effects of low power laser treatment involve changes in the cell cycle.     

Eccentric fixation in Stargardt's disease assessed by Tübingen perimetry

PURPOSE: To measure eccentric fixation characteristics in visual fields of patients with Stargardt's disease. METHODS: The positions of fixation loci (FL) in the visual field were determined by Tübingen perimetry (TP), using the position of the blind spots in 173 patients. Altogether, 669 visual fields were measured at baseline and during follow-up. Twenty patients were also examined by scanning laser ophthalmoscope (SLO). RESULTS: Ninety-five of 173 patients showed a ring scotoma with central fixation in at least one test, which could persist for up to 18.8 years. The median age for a 50% chance of the development of eccentric fixation was 23.6 years. One hundred four patients (203 eyes) used eccentric fixation in at least one eye; in 154 eyes, the FL was placed below the scotoma and in 33 eyes to the left of it, in 11 to the right of it, and in 5 above it. Once the FL was chosen, it remained within the same visual field area at subsequent tests, varying on average by 1.76 degrees. Compared with SLO results, the mean distance between FL and PRL was 1.90 degrees. CONCLUSIONS: It is possible to determine the position of the FL by perimetry with sufficient accuracy if the blind spot is well delimited. Stargardt patients can keep central fixation for different time intervals before changing to an eccentric FL. Most of them show an FL below the central scotoma, which is considered favorable for horizontal reading.     

Infraorbital eyelid edema as the presenting sign of bronchogenic carcinoma

A 59‐year‐old man presented at our department with a 4‐week history of persisting and therapy‐refractory infraorbital edema ( Fig. 1 ). There was no previous history of eyelid edema, allergic reactions, autoimmune diseases, or new medications. Earlier therapy with corticosteroids and antihistamines was ineffective.

Figure 1 Open in figure viewer PowerPoint Persistent swelling of both infraorbital folds     

Lymphocytes proliferate in blood and lymph nodes following interleukin-2 therapy in addition to highly active antiretroviral therapy.

BACKGROUND: Substantial redistribution of lymphocytes occurs upon the initiation of highly active antiretroviral therapy (HAART) and immune-based HIV therapies. OBJECTIVE: To evaluate the relative contribution of apoptosis and proliferation to changes in lymphocyte populations in peripheral blood and lymph node resulting from interleukin-2 (IL-2) therapy in patients receiving stable HAART. METHODS: Lymphocyte apoptosis was analyzed on various subtypes using fluorescence activated cell sorting with an annexin-V antibody in peripheral blood and by the TUNEL (terminal uridine nucleotide end labelling) method in corresponding lymph node sections. Lymphocyte proliferation was evaluated using an antibody against the cell cycle-associated marker Ki-67 (MIB-1) in peripheral blood and lymph nodes. RESULTS: A transient increase in apoptosis was seen in peripheral blood and lymph nodes during a cycle of subcutaneous IL-2. A pronounced proliferative effect of IL-2 (from 6.4% of total lymphocytes in patients only treated with HAART to 23.4% in those treated with HAART + IL-2) was detected in peripheral blood, affecting the CD4, CD8 and CD16/56 subsets to a similar extent. Remarkably, the proliferative effect also occurred in lymphoid tissues. While the lymph node structure gradually disintegrated over 24 months in some individuals, the amount of proliferating lymphocytes, including CD4 cells, B cells and follicular dendritic cells, greatly increased upon IL-2, while HIV RNA load in lymph nodes remained unaffected. CONCLUSION: These results show that IL-2 leads to lymphocyte proliferation in peripheral blood and lymph nodes without an impact on viral load in lymphoid tissue. These results have important implications for attempts to reconstitute the immune system in HIV disease.