Critical loss of primary implant stability in osteosynthesis locking screws under cyclic overloading

Primary implant stability, which refers to the stability of the implant during the initial healing period is a crucial factor in determining the long-term success of the implant and lays the foundation for secondary implant stability achieved through osseointegration. Factors affecting primary stability include implant design, surgical technique, and patient-specific factors like bone quality and morphology. In vivo, the cyclic nature of anatomical loading puts osteosynthesis locking screws under dynamic loads, which can lead to the formation of micro cracks and defects that slowly degrade the mechanical connection between the bone and screw, thus compromising the initial stability and secondary stability of the implant. Monotonic quasi-static loading used for testing the holding capacity of implanted screws is not well suited to capture this behavior since it cannot capture the progressive deterioration of peri‑implant bone at small displacements. In order to address this issue, this study aims to determine a critical point of loss of primary implant stability in osteosynthesis locking screws under cyclic overloading by investigating the evolution of damage, dissipated energy, and permanent deformation. A custom-made test setup was used to test implanted 2.5 mm locking screws under cyclic overloading test. For each loading cycle, maximum forces and displacement were recorded as well as initial and final cycle displacements and used to calculate damage and energy dissipation evolution. The results of this study demonstrate that for axial, shear, and mixed loading significant damage and energy dissipation can be observed at approximately 20 % of the failure force. Additionally, at this load level, permanent deformations on the screw-bone interface were found to be in the range of 50 to 150 mm which promotes osseointegration and secondary implant stability. This research can assist surgeons in making informed preoperative decisions by providing a better understanding of the critical point of loss of primary implant stability, thus improving the long-term success of the implant and overall patient satisfaction.

A mechanically validated open-source silicone model for the training of gastric perforation sewing

BACKGROUND

Gastrointestinal perforation is commonly seen in emergency departments. The perforation of the stomach is an emergency situation that requires immediate surgical treatment. The necessary surgical skills require regular practical training. Owing to patient`s safety, in vivo training opportunities in medicine are restricted. Animal tissue especially porcine tissue, is commonly used for surgical training. Due to its limiting factors, artificial training models are often to be preferred. Many artificial models are on the market but to our knowledge, none that mimic the haptic- and sewing properties of a stomach wall at the same time. In this study, an open source silicone model of a gastric perforation for training of gastric sewing was developed that attempts to provide realistic haptic- and sewing behaviour.

METHODS

To simulate the layered structure of the human stomach, different silicone materials were used to produce three different model layups. The production process was kept as simple as possible to make it easily reproducible. A needle penetration setup as well as a systematic haptic evaluation were developed to compare these silicone models to a real porcine stomach in order to identify the most realistic model.

RESULTS

A silicone model consisting of three layers was identified as being the most promising and was tested by clinical surgeons.

CONCLUSIONS

The presented model simulates the sewing characteristics of a human stomach wall, is easily reproducible at low-costs and can be used for practicing gastric suturing techniques.

TRIAL REGISTRATIONS

Not applicable.

Capacity of the medullary cavity of tibia and femur for intra-bone marrow transplantation in mice

Intra-bone marrow transplantation (IBMT) has been adapted for mouse models to improve the seeding efficiency of transplanted hematopoietic stem and progenitor cells. Commonly used injection volumes for IBMT into the tibia differ between 10 and 40 μL even though considerable amounts of injected cells leak into the blood circulation immediately after injection. Injection of 3 μL trypan blue into the tibia of dead BALB/c mice showed staining in large vessels of hind limbs, even without supporting circulation. We therefore tested the effective capacity of the medullary cavity of dissected tibiae and femora of different mouse strains by bioluminescence imaging after injection of luciferase expressing cells. Cell leakage was already observed at 3 μL of injection volume and the measured emission rate increased significantly when 5 and 10 μL of volume with the same cell concentration were injected. Surprisingly, increasing injection volumes containing constant cell amounts resulted in comparable emission rates, suggesting a similar amount of leaked and absorbed cells independent of the injection volume. However, the absorption of a specific amount of injected cells could not be confirmed, as the ratio of leaked to absorbed cells was similar between IBMT that were performed with a constant injection volume containing either low or high cell amounts. In summary, for optimal cell transplantation via IBMT in mice we suggest to inject a high concentrated cell suspension with a maximum injection volume of 3 μL.

Erythropoietin drives breast cancer progression by activation of its receptor EPOR

Breast cancer is a leading cause of cancer-related deaths. Anemia is common in breast cancer patients and can be treated with blood transfusions or with recombinant erythropoietin (EPO) to stimulate red blood cell production. Clinical studies have indicated decreased survival in some groups of cancer patients treated with EPO. Numerous tumor cells express the EPO receptor (EPOR), posing a risk that EPO treatment would enhance tumor growth, but the mechanisms involved in breast tumor progression are poorly understood.

Here, we have examined the functional role of the EPO-EPOR axis in pre-clinical models of breast cancer. EPO induced the activation of PI3K/AKT and MAPK pathways in human breast cancer cell lines. EPOR knockdown abrogated human tumor cell growth, induced apoptosis through Bim, reduced invasiveness, and caused downregulation of MYC expression. EPO-induced MYC expression is mediated through the PI3K/AKT and MAPK pathways, and overexpression of MYC partially rescued loss of cell proliferation caused by EPOR downregulation. In a xenotransplantation model, designed to simulate recombinant EPO therapy in breast cancer patients, knockdown of EPOR markedly reduced tumor growth.

Thus, our experiments in vitro and in vivo demonstrate that functional EPOR signaling is essential for the tumor-promoting effects of EPO and underline the importance of the EPO-EPOR axis in breast tumor progression.

Muscle hypertrophy due to scarring of the S1 nerve root

Segmental muscle enlargement occurs in a variety of neurogenic conditions. We present a patient with calf hypertrophy, likely produced by continuous neuromuscular irritability and compensatory type 1 and type 2 muscle fiber hypertrophy. The underlying lesion of the S1 nerve root was caused by scarring, which could be demonstrated by Gadolinum enhanced, fat saturated magnetic resonance imaging. Thus, the application of this technique is recommended in otherwise etiologically unclear cases of neurogenic muscular lesions in order to detect chronic nerve root pathology.

[Optic nerve neuritis after 50 years of age: symptom of a previously undiagnosed multiple sclerosis]

BACKGROUND

The onset of multiple sclerosis after the age of 50 years is rare. We report four patients with optic neuritis and oligoclonal bands or increased IgG production in the cerebrospinal fluid. Three of them subsequently developed clinically definite multiple sclerosis.

PATIENTS

Four apparently healthy women, 62, 56, 50 and 50 years of age, presented with progressive visual loss, three patients in one eye and one patient in both eyes. The diagnostic work-up revealed no findings indicating an ischemic process, an infectious, systemic inflammatory, or neoplastic disease. Examination of the cerebrospinal fluid revealed oligoclonal bands and/or increased production of IgG. Visual acuity recovered during the following weeks to 8 months. Three of the 4 patients subsequently developed additional neurologic signs compatible with multiple sclerosis.

CONCLUSION

Optic neuritis can be the presenting sign of multiple sclerosis even after the age of 50.

Importance of effective central nervous system therapy in isolated bone marrow relapse of childhood acute lymphoblastic leukemia. BFM (Berlin-Frankfurt-Münster) Relapse Study Group

Presymptomatic central nervous system (CNS) treatment in children with a late isolated first bone marrow (BM) relapse of acute lymphoblastic leukemia (ALL) was based on intermediate-dose systemic and intrathecal (IT) methotrexate (MTX) in the multicenter trial, ALL-REZ BFM 85. Because this was associated with an excess of overt second CNS relapses, cranial radiotherapy (cRT) plus prolonged triple IT therapy with MTX, cytarabine, and prednisone was instituted during the course of the subsequent trial, ALL-REZ BFM 87. Results of children with or without cRT, but otherwise identical chemotherapy, are presented here. Between April 1985 and March 1990, 93 children with their first late isolated BM relapse of ALL were entered on protocols ALL-REZ BFM 85M and ALL-REZ BFM 87. An intensive 6-month phase of multiagent chemotherapy that included 8 courses of systemic MTX (1 g/m2) plus IT MTX was followed by 2 years of conventional maintenance therapy with daily 6-thioguanine and biweekly MTX. Children with bone marrow transplantation excluded, 73 were in complete remission at the end of intensive polychemotherapy, 40 of whom received fractionated cRT plus triple IT therapy during the following 6 months; 11 did not receive cRT but prolonged triple IT; 22 received neither cRT nor prolonged triple IT. Except for a higher percentage of children who had received cRT in front-line protocols (29 of 33 v 20 of 40), the patient groups without or with salvage cRT were comparable. Of 33 children without salvage cRT, 26 relapsed, compared with 21 of 40 who had received cRT (P < .05). The difference was solely attributable to second relapses with CNS involvement (10 of 33 v 1 of 40; P < .01). Estimated 6-year event-free survival rates were .18 for children without cRT and .46 for children with cRT (P < .01). In patients without cRT, no impact of prolonged IT therapy could be shown. The data suggest that second CNS prophylaxis with cRT and prolonged triple IT therapy in children with late isolated BM relapse of ALL is effective in preventing CNS relapses, in reducing the overall relapse rate, and in increasing the overall survival rate.

Urolithiasis in Tennessee: an occupational window into a regional problem

BACKGROUND

Urinary tract stones (stones) are believed to be unusually common in the southeastern United States but neither the incidence of nor the risk factors for stones are known.

METHODS

In three well-defined occupational populations in eastern Tennessee, we assessed the prevalence, incidence, and cumulative incidence of stones and measured biochemical risk factors for lithogenesis.

RESULTS

The age-adjusted prevalence of stones was 18.5 percent in Tennessee compared to 7.7 percent among White males in US NHANES (prevalence ratio 2.4, 95% CI 1.7, 3.3). The cumulative incidence (risk) was 27.8 percent by age 65, higher than in any other reported population. Risk factors were age, a family history, and urinary saturation with calcium-oxalate (COAX). Persons with a positive family history and the highest measured CAOX index had a predicted lifetime risk of 88.8 percent. Biochemical factors affecting lithogenesis were hypercalciuria, hyperoxaluria, and low urine volume.

CONCLUSION

Future research should characterize the geographic boundaries of a southeastern "stone-belt" and explore genetic and dietary hypotheses that might explain it.

Nephropathy in cadmium workers: assessment of risk from airborne occupational exposure to cadmium

To assess the quantitative relation between exposure to airborne cadmium and various markers of renal tubular and glomerular function, 45 male workers employed at a plant that recovers cadmium from industrial waste and 32 male hospital workers of similar age and geographical location were examined. Cumulative external exposure to airborne cadmium (dose) was estimated from historical air sampling data, adjusted for respirator use. Increasing cadmium dose was associated with multiple renal tubular functional abnormalities, including reduced reabsorption of beta-2-microglobulin (beta-2), retinol binding protein (RBP), calcium, and phosphate. Serum creatinine concentration also increased with cadmium dose, suggesting impaired glomerular function. Mean systolic and diastolic blood pressures were higher in the cadmium workers than in the unexposed (134 v 120 mm Hg and 80 v 73 mm Hg respectively), but only systolic blood pressure was significantly associated with cadmium dose in multivariate analyses. Cadmium dose remained the most important predictor of serum creatinine concentration after controlling for age, blood pressure, body size, and other extraneous factors. Logistic regression to model the probability (prevalence) of various renal abnormalities with increasing dose of cadmium was used. The probability of multiple tubular abnormalities and raised serum creatinine concentration increased sharply at cumulative cadmium exposures exceeding 300 mg/m3 days, corresponding to working for 4.3 years at the current permissible United States exposure limit for cadmium dust.

Secretory immunoglobulin A (sIgA) in the serum of cystic fibrosis patients

Clearly increased sIgA values were found in cystic fibrosis patients in more than 70%. The highest concentrations were seen in patients with obstructive liver disease. There were no correlations between sIgA and liver-associated enzymes. Postmortem histology and sIgA correlated well. These data suggest a pertinent role of sIgA assessment in evaluation of hepatic involvement in cystic fibrosis.

A contribution regarding the Rett syndrome

Andreas Rett described a "cerebral atrophic syndrome accompanying hyperammonemia" for the first time in 1966, and by 1983 over 80 such cases had been identified and described not only in Austria but also in other countries. If the information at our disposal is correct, we have reported on what we believe is the first case of a patient with a definite Rett syndrome in the German Democratic Republic. We are, regrettably, still unable to contribute decisively to the clarification of the etiology and pathogenesis of the disease, but will, through further publications and papers at pediatric and child-neuropsychiatric meetings, continue to spread the knowledge of the symptomatology. It is remarkable that in the present case neither computer tomography nor electroencephalography showed definite abnormalities despite much effort. Definite proof of cerebral atrophy cannot, therefore, yet be furnished. But we still have no doubt that our diagnosis is correct. We intend, within the framework of a joint study being conducted by the University Pediatric Hospital Rostock and the Ludwig Boltzmann Institute, Vienna, as part of the scientific and technical cooperation between the Republic of Austria and the German Democratic Republic, to investigate further the epidemiology and etiology of this disease in cooperation with our Departments of Metabolic Disturbances and Genetics.