The long-term mechanical integrity of non-reinforced PEEK-OPTIMA polymer for demanding spinal applications: experimental and finite-element analysis

Polyetheretherketone (PEEK) is a novel polymer with potential advantages for its use in demanding orthopaedic applications (e.g. intervertebral cages). However, the influence of a physiological environment on the mechanical stability of PEEK has not been reported. Furthermore, the suitability of the polymer for use in highly stressed spinal implants such as intervertebral cages has not been investigated. Therefore, a combined experimental and analytical study was performed to address these open questions. A quasi-static mechanical compression test was performed to compare the initial mechanical properties of PEEK-OPTIMA polymer in a dry, room-temperature and in an aqueous, 37 degrees C environment (n=10 per group). The creep behaviour of cylindrical PEEK polymer specimens (n=6) was measured in a simulated physiological environment at an applied stress level of 10 MPa for a loading duration of 2000 hours (12 weeks). To compare the biomechanical performance of different intervertebral cage types made from PEEK and titanium under complex loading conditions, a three-dimensional finite element model of a functional spinal unit was created. The elastic modulus of PEEK polymer specimens in a physiological environment was 1.8% lower than that of specimens tested at dry, room temperature conditions (P<0.001). The results from the creep test showed an average creep strain of less than 0.1% after 2000 hours of loading. The finite element analysis demonstrated high strain and stress concentrations at the bone/implant interface, emphasizing the importance of cage geometry for load distribution. The stress and strain maxima in the implants were well below the material strength limits of PEEK. In summary, the experimental results verified the mechanical stability of the PEEK-OPTIMA polymer in a simulated physiological environment, and over extended loading periods. Finite element analysis supported the use of PEEK-OPTIMA for load-bearing intervertebral implants.

[The mandatory diaper peek in newborn girls]

We present a 3 day old girl born at term presenting with an interlabial, cystic mass. Pregnancy, delivery and routine antenatal screening were unremarkable. The smooth lesion was located in the anterior half of the vulva, covered with thin vessels. The medially displaced urethra and the medio-posteriorly displaced hymen were identified. Voiding was not impaired. We discuss the differential diagnosis of vulvar masses in the newborn girl. A thorough clinical examination must be the standard of care of pediatric examinations in infants.

Histomorphometric and Radiographical Changes After Lumbar Implantation of the PEEK Nonfusion Interspinous Device in the BB.4S Rat Model

Study Design. An experimental animal study. Objective. To investigate histomorphometric and radiographical changes in the BB.4S rat model after PEEK (polyetheretherketone) nonfusion interspinous device implantation. Summary of Background Data. Clinical effectiveness of the PEEK nonfusion spine implant Wallis (Abbott, Bordeaux, France; now Zimmer, Warsaw, IN) is well documented. However, there is a lack of evidence on the long-term effects of this implant on bone, in particular its influence on structural changes of bone elements of the lumbar spine. Methods. Twenty-four male BB.4S rats aged 11 weeks underwent surgery for implantation of a PEEK nonfusion interspinous device or for a sham procedure in 3 groups of 8 animals each: 1) implantation at level L4–L5; 2) implantation at level L5–L6; and 3) sham surgery. Eleven weeks postoperatively osteolyses at the implant-bone interface were measured via radiograph, bone mineral density of vertebral bodies was analyzed using osteodensitometry, and bone mineral content as well as resorption of the spinous processes were examined by histomorphometry. Results. Resorption of the spinous processes at the site of the interspinous implant was found in all treated segments. There was no significant difference in either bone density of vertebral bodies or histomorphometric structure of the spinous processes between adjacent vertebral bodies, between treated and untreated segments and between groups. Conclusion. These findings indicate that resorption of spinous processes because of a result of implant loosening, inhibit the targeted load redistribution through the PEEK nonfusion interspinous device in the lumbar spinal segment of the rat. This leads to reduced long-term stability of the implant in the animal model. These results suggest that PEEK nonfusion interspinous devices like the Wallis implants may have time-limited effects and should only be used for specified indications.

MIAWARA-C, a new ground based water vapor radiometer for measurement campaigns

In this paper a new 22 GHz water vapor spectro-radiometer which has been specifically designed for profile measurement campaigns of the middle atmosphere is presented. The instrument is of a compact design and has a simple set up procedure. It can be operated as a standalone instrument as it maintains its own weather station and a calibration scheme that does not rely on other instruments or the use of liquid nitrogen. The optical system of MIAWARA-C combines a choked gaussian horn antenna with a parabolic mirror which reduces the size of the instrument in comparison with currently existing radiometers. For the data acquisition a correlation receiver is used together with a digital cross correlating spectrometer. The complete backend section, including the computer, is located in the same housing as the instrument. The receiver section is temperature stabilized to minimize gain fluctuations. Calibration of the instrument is achieved through a balancing scheme with the sky used as the cold load and the tropospheric properties are determined by performing regular tipping curves. Since MIAWARA-C is used in measurement campaigns it is important to be able to determine the elevation pointing in a simple manner as this is a crucial parameter in the calibration process. Here we present two different methods; scanning the sky and the Sun. Finally, we report on the first spectra and retrieved water vapor profiles acquired during the Lapbiat campaign at the Finnish Meteorological Institute Arctic Research Centre in Sodankylä, Finland. The performance of MIAWARA-C is validated here by comparison of the presented profiles against the equivalent profiles from the Microwave Limb Sounder on the EOS/Aura satellite.

Copeptin concentration in cord blood in infants with early-onset sepsis, chorioamnionitis and perinatal asphyxia

Background Vasopressin is one of the most important physiological stress and shock hormones. Copeptin, a stable vasopressin precursor, is a promising sepsis marker in adults. In contrast, its involvement in neonatal diseases remains unknown. The aim of this study was to establish copeptin concentrations in neonates of different stress states such as sepsis, chorioamnionitis and asphyxia. Methods Copeptin cord blood concentration was determined using the BRAHMS kryptor assay. Neonates with early-onset sepsis (EOS, n = 30), chorioamnionitis (n = 33) and asphyxia (n = 25) were compared to a control group of preterm and term (n = 155) neonates. Results Median copeptin concentration in cord blood was 36 pmol/l ranging from undetectable to 5498 pmol/l (IQR 7 - 419). Copeptin cord blood concentrations were non-normally distributed and increased with gestational age (p < 0.0001). Neonates born after vaginal compared to cesarean delivery had elevated copeptin levels (p < 0.0001). Copeptin correlated strongly with umbilical artery pH (Spearman's Rho -0.50, p < 0.0001), umbilical artery base excess (Rho -0.67, p < 0.0001) and with lactate at NICU admission (Rho 0.54, p < 0.0001). No difference was found when comparing copeptin cord blood concentrations between neonates with EOS and controls (multivariate p = 0.30). The highest copeptin concentrations were found in neonates with asphyxia (median 993 pmol/l). Receiver-operating-characteristic curve analysis showed that copeptin cord blood concentrations were strongly associated with asphyxia: the area under the curve resulted at 0.91 (95%-CI 0.87-0.96, p < 0.0001). A cut-off of 400 pmol/l had a sensitivity of 92% and a specifity of 82% for asphyxia as defined in this study. Conclusions Copeptin concentrations were strongly related to factors associated with perinatal stress such as birth acidosis, asphyxia and vaginal delivery. In contrast, copeptin appears to be unsuitable for the diagnosis of EOS.

Combined bone and soft-tissue augmentation surgery in temporo-orbital contour reconstruction

Temporal hollowing due to temporal muscle atrophy after standard skull base surgery is common. Various techniques have been previously described to correct the disfiguring defect. Most often reconstruction is performed using freehand molded polymethylmethacrylate cement. This method and material are insufficient in terms of aesthetic results and implant characteristics. We herein propose reconstruction of such defects with a polyetheretherketone (PEEK)-based patient-specific implant (PSI) including soft-tissue augmentation to preserve normal facial topography. We describe a patient who presented with a large temporo-orbital hemangioma that had been repaired with polymethylmethacrylate 25 years earlier. Because of a toxic skin atrophy fistula, followed by infection and meningitis, this initial implant had to be removed. The large, disfiguring temporo-orbital defect was reconstructed with a PEEK-based PSI. The lateral orbital wall and the temporal muscle atrophy were augmented with computer-aided design and surface modeling techniques. The operative procedure to implant and adopt the reconstructed PEEK-based PSI was simple, and an excellent cosmetic outcome was achieved. The postoperative clinical course was uneventful over a 5-year follow-up period. Polyetheretherketone-based combined bony and soft contour remodeling is a feasible and effective method for cranioplasty including combined bone and soft-tissue reconstruction of temporo-orbital defects. Manual reconstruction of this cosmetically delicate area carries an exceptional risk of disfiguring results. Augmentation surgery in this anatomic location needs accurate PSIs to achieve satisfactory cosmetic results. The cosmetic outcome achieved in this case is superior compared with previously reported techniques.

Retention force of plastic clips on implant bars: a randomized controlled trial

Retention of overdentures is important for patients' satisfaction. The study tested whether the clinical performance of retentive clips made of poly-ether-ether-ketone (PEEK) is superior to those made of poly-oxy-methylene (POM).

Treatment of adolescents with early-onset schizophrenia spectrum disorders: in search of a rational, evidence-informed approach

Purpose of review: We aimed to review literature on the efficacy and tolerability of psychosocial and psychopharmacological interventions in youth with early-onset schizophrenia spectrum disorders (EOS). A rationale for pragmatic psychopharmacology in EOS, including dosing, switching and adverse effect monitoring and management, is provided. Recent findings: Three randomized controlled trials (RCTs) over the last 8 years demonstrated benefits of psychosocial interventions (i.e. psychoeducation, cognitive remediation, cognitive behavioural therapy) for EOS without clear advantages of one psychosocial treatment over another. Six large, placebo-controlled, short-term RCTs over the last 4 years demonstrated that aripiprazole, olanzapine, paliperidone, quetiapine and risperidone, but not ziprasidone, were superior to placebo. Except for clozapine's superiority in treatment-refractory EOS, efficacy appeared similar across studied first-generation and second-generation antipsychotics, but tolerability varied greatly across individual agents. Summary: Antipsychotics are efficacious in the treatment of EOS. Given the lack of efficacy differences between antipsychotics (except for clozapine for treatment-refractory EOS), we propose that tolerability considerations need to guide choice of antipsychotics. Further and longer-term efficacy and effectiveness studies are urgently needed that should also explore pharmacologic and nonpharmacologic augmentation strategies.

Pancreatic stone protein as a novel marker for neonatal sepsis

Early-onset sepsis (EOS) is one of the main causes for the admission of newborns to the neonatal intensive care unit. However, traditional infection markers are poor diagnostic markers of EOS. Pancreatic stone protein (PSP) is a promising sepsis marker in adults. The aim of this study was to investigate whether determining PSP improves the diagnosis of EOS in comparison with other infection markers.

Comparison of the effects of cetylpyridinium chloride with an essential oil mouth rinse on dental plaque and gingivitis - a six-month randomized controlled clinical trial

OBJECTIVE: To compare the effects of an experimental mouth rinse containing 0.07% cetylpyridinium chloride (CPC) (Crest Pro-Health) with those provided by a commercially available mouth rinse containing essential oils (EOs) (Listerine) on dental plaque accumulation and prevention of gingivitis in an unsupervised 6-month randomized clinical trial. MATERIAL AND METHODS: This double-blind, 6-month, parallel group, positively controlled study involved 151 subjects balanced and randomly assigned to either positive control (EO) or experimental (CPC) mouth rinse treatment groups. At baseline, subjects received a dental prophylaxis procedure and began unsupervised rinsing twice a day with 20 ml of their assigned mouthwash for 30 s after brushing their teeth for 1 min. Subjects were assessed for gingivitis and gingival bleeding by the Gingival index (GI) of Löe ; Silness (1963) and plaque by the Silness ; Löe (1964) Plaque index at baseline and after 3 and 6 months of rinsing. At 3 and 6 months, oral soft tissue health was assessed. Microbiological samples were also taken for community profiling by the DNA checkerboard method. RESULTS: Results show that after 3 and 6 months of rinsing, there were no significant differences (p=0.05) between the experimental (CPC) and the positive control mouth rinse treatment groups for overall gingivitis status, gingival bleeding, and plaque accumulation. At 6 months, the covariant (baseline) adjusted mean GI and bleeding sites percentages for the CPC and the EO rinses were 0.52 and 0.53 and 8.7 and 9.3, respectively. Both mouth rinses were well tolerated by the subjects. Microbiological community profiles were similar for the two treatment groups. Statistically, a significant greater reduction in bleeding sites was observed for the CPC rinse versus the EO rinse. CONCLUSION: The essential findings of this study indicated that there was no statistically significant difference in the anti-plaque and anti-gingivitis benefits between the experimental CPC mouth rinse and the positive control EO mouth rinse over a 6-month period.