Hand Perfusion in Patients with Physiological or Pathological Allen's Tests.

BACKGROUND: The Allen test (AT) is a widely used clinical tool for the preoperative assessment of sufficient dual vessel hand perfusion although the impact of a pathological AT on tissue perfusion of the hand is not entirely clear. This study reveals perfusion changes of the hand in patients with pathological and physiological AT after terminating the dual blood supply. METHODS: Patients were distributed into 2 groups (physiological and pathological AT) that each contained 25 members. Perfusion of the thumb, middle, and small fingers was measured with a laser Doppler based ("oxygen-to-see" [O2C]) device. A steady state was measured and also values at 1, 3, 5, and 10 minutes after radial occlusion were measured. RESULTS: In patients with a physiological AT, only 1 out of 18 values differed significantly from the steady state measurements after 10 minutes, whereas patients with a pathological AT showed significant alterations in 8 out of 18 values. Oxygen saturation of the superficial and deep tissues appeared to be significantly worse in patients with a pathological AT. CONCLUSION: Patients with a pathological AT suffered significantly more from the loss of dual hand perfusion than patients with a physiological AT. Patients with a pathological AT need more time to compensate for the altered perfusion pattern.

Color duplex ultrasonography versus handheld Doppler to plan anterior lateral thigh flaps.

BACKGROUND: The anterior lateral thigh flap (ALT) has become increasingly important in reconstructive surgery in the head and neck region. To cope with the problem of anatomical variability in the supplying blood vessels, preoperative evaluation is desirable. Purpose of the study is to compare the most commonly used Doppler devices Handheld Doppler (HD) and Color Doppler Ultrasonography (CDU) for their clinical reliability. METHODS: Forty five consecutive head and neck cancer patients (mean age 66.0 ± 11.2 years) were included in the study. They all underwent a reconstruction via ALT flap for a defect in the head and neck area. Study period ranged from May 2014 to August 2015. We preoperatively conducted HD and CDU on the lateral thigh and compared the intraoperative findings by measuring presence of the perforator and distance to the estimated position. RESULTS: There were 95 perforators identified in 45 patients. The sensitivity and positive predictive value (PPV) were calculated as 97.9% and 100% for CDU and 90.5% and 80.4% for HD, respectively. Accuracy was significantly greater with the HD compared to the CDU device (P < 0.001) and was strongly associated with body mass index (BMI) (P < 0.001). This effect was stronger in HD than in CDU (r = 0.800; P < 0.001 versus r = 0.673; P < 0.001). CONCLUSIONS: Our results indicate CDU is more precise and reliable than HD with respect to detecting the anatomical position of perforating arteries. © 2017 Wiley Periodicals, Inc. Microsurgery 37:388-393, 2017.

The application of temporal difference learning in optimal diet models.

An experience-based aversive learning model of foraging behaviour in uncertain environments is presented. We use Q-learning as a model-free implementation of Temporal difference learning motivated by growing evidence for neural correlates in natural reinforcement settings. The predator has the choice of including an aposematic prey in its diet or to forage on alternative food sources. We show how the predator's foraging behaviour and energy intake depend on toxicity of the defended prey and the presence of Batesian mimics. We introduce the precondition of exploration of the action space for successful aversion formation and show how it predicts foraging behaviour in the presence of conflicting rewards which is conditionally suboptimal in a fixed environment but allows better adaptation in changing environments.

Modified implant surfaces show different biofilm compositions under in vivo conditions.

OBJECTIVE: Plaque accumulation on implant surfaces can result in peri-implantitis with potential implant loss. The aim of the present study was to examine the influence of zirconium nitride (ZrN) as a potential implant surface on the biofilm composition and diversity in vivo. MATERIAL AND METHODS: ZrN- or titanium (Ti)-coated glass specimens and ZrN or roughened Ti discs were used as substrates. Pure glass and polished titanium served as controls. The specimens were mounted on removable intraoral splints in five adults. After 24 h of intraoral exposure, the biofilms were analyzed applying single-strand conformation polymorphism (SSCP analysis) of 16S rRNA genes. Sequence analysis of the dominant bands excised from the SSCP fingerprints allowed to taxonomically describe bacteria derived from biofilm samples. RESULTS: The highest number of bands was counted on pure glass and Ti 800. ZrN-coated glass and ZrN-coated titanium discs showed the lowest values for species richness. However, no significant differences were observed regarding the diversity of the identified bacterial species among all the surfaces examined. A total of 46 different bacteria were identified. The dominant bands within the fingerprints indicated bacteria belonging to the Streptococcus group as identified by their 16S rDNA sequence. CONCLUSION: A coating of glass surfaces with ZrN significantly reduced the species richness in early bacterial colonization but the diversity was not significantly changed. In consideration of the results obtained by this and former studies a ZrN coating appears to rather modify the quantity of early bacterial adherence than the quality of the microbial community structure.

Numerical simulations of different configured venous anastomosis in microvascular flap transfer.

BACKGROUND: Free flap surgery is a well-established method for covering large defects in the head and neck region. Most cases of flap failure are caused by venous thrombosis. Thus, there is a lot of discussion about the ideal design of venous anastomosis and its impact on the hemodynamics in the vessels. This study concentrates on the simulation of flow patterns of different designs of venous anastomoses. METHODS: First, fluid flow rates were measured using transit-time flow measurement in the veins of 20 patients who received free flaps between 2016 and 2017. Five different designs of porcine anastomoses were scanned using micro-computed tomography, to create three-dimensional models. In the second step, numerical simulations of the blood flow were performed to gain insights into the vessel flow patterns. RESULTS: The simulations revealed recirculation areas in the 60° and 90° end-to-side anastomoses, especially in combination with low fluid flow rates. In addition, there were large areas of recirculation in the 1:3 end-to-end anastomoses. CONCLUSION: The type of venous anastomosis should be decided individually. End-to-side anastomosis can be recommended in cases with high caliber differences or in those with high venous outflow. End-to-end anastomoses should be preferred in conditions with low venous outflow.

Distress thermometer for preoperative screening of patients with oral squamous cell carcinoma.

In this study, we evaluate the association between distress, various demographic and medical variables, and the prevalence of psychosocial distress in preoperative patients with oral squamous cell carcinoma. A total of 100 consecutive patients were recruited into the study and asked to complete the Distress Thermometer (DT) form with the Problem List questionnaire prior to surgical intervention; the average distress score was 5.7 ± 2.7. The distress score was neither correlated with age (r = -0.025; p = 0.804) nor with tumor size (r = 0.028; p = 0.785). General worries, anxiety, sadness, depression, pain, exhaustion, sleeping disorders, or problems with nutrition resulted in significantly higher distress scores compared to patients without these complaints. Individuals with a DT score of 5 or higher (p = 0.006) were advised to seek out psychological support. There is a strong correlation between a high DT score and emotional disorders, as well as physical problems.

Prospective comparison of perioperative antibiotic management protocols in oncological head and neck surgery.

OBJECTIVES: The adequate perioperative antibiotic prophylaxis in head and neck cancer surgery is an important and easy applicable tool to decrease nosocomial morbidity and mortality by reducing the rate of infections. In the study a strictly perioperative antibiosis is compared with an extended postoperative prophylactic antibiosis. We aim to clarify the value of postoperative prophylactic antibiosis for the recovery and clinical course of patients. MATERIAL AND METHODS: In this prospective study 75 consecutive patients, who underwent major oncological head and neck surgery were included and divided in three groups, each containing 25 patients. The first group received peri- and postoperative antibiotic prophylaxis (POAP) from the day of operation until the fifth day postoperatively. The second group was treated with perioperative antibiotic prophylaxis (PEAP) only. The third group received perioperative antibiotic prophylaxis and increased local antiseptic care (PAPAC). General anamnestic data was collected, as well as duration of hospitalisation, stay on intensive care unit, rate and type of infections, surgical closure of the tracheostomy, and postoperative blood parameters. RESULTS: There were no statistically significant differences in general diseases or extent of surgery between the groups. There were statistically significant fewer patients suffering from surgical site infections in subjects with POAP (n = 1) in comparison to PEAP (n = 9; p = 0.011) and PAPAC (n = 9; p = 0.011). In contrast, other nosocomial infections (pneumonia, urinary tract infection, sepsis) did not decrease under a prolonged antibiotic prophylaxis. CONCLUSION: Based on findings of the study, we recommend an extended postoperative antibiotic prophylaxis for patients undergoing major oncological head and neck surgery.

"IIb or not IIb" - The necessity of dissection in patients with oral squamous cell carcinoma.

The necessary extent of cervical dissection in oral squamous cell carcinoma (OSCC) is still under discussion. Due to its anatomical properties Robins level IIb has a special role in neck dissection. This study focuses on the lymph node metastatic behaviour of OSCC in level IIb and evaluates its worth of dissection. 183 consecutive patients with OSCC were retrospectively screened for age, gender, TNM classification, cancer stage (after UICC), tumour localization, tumour infiltrations depth, and affected cervical lymph node levels. Associations between lymph node metastases and the above-mentioned characteristics were evaluated using Pearson's chi square test and Spearman's rho correlation analyses. Metastases in level IIb were seen in only 3.3% of all patients, and none of these metastases were an exclusive metastasis. Lymph node metastases most likely occurred in levels I and IIa at ipsilateral sites, and metastases were significantly related to tumour size (p < 0.01) and the infiltration of lymph vessels (p < 0.001). The locations of primary cancer sites in metastatic disease were the soft palate, alveolar crest of the lower jaw and buccal mucosa. Lymph node metastases of OSCC in level IIb remain rare, especially as exclusive metastases and in clinically N-negative necks. The findings of our study support the hypothesis of sparing neck dissection in level IIb in cases of clinically negative necks.

Biomechanical competence of six different bone screws for reconstructive surgery in three different transplants: Fibular, iliac crest, scapular and artificial bone.

The goal of this study was to determine a combination of screw and transplantation type that offers optimal primary stability for reconstructive surgery. Fibular, iliac crest, and scapular transplants were tested along with artificial bone substrate. Six different kinds of bone screws (Medartis(©)) were compared, each type utilized with one of six specimens from human transplants (n = 6). Controlled screw-in-tests were performed and the required torque was protocolled. Subsequently, pull-out-tests were executed to determine the retention forces. The artificial bone substitute material showed significantly higher retention forces than real bone samples. The self-drilling screws achieved the significantly highest retention values in the synthetic bone substitute material. Cancellous screws achieved the highest retention in the fibular transplants, while self-drilling and cancellous screws demonstrated better retention than cortical screws in the iliac crest. In the scapular graft, no significant differences were found between the screw types. In comparison to the human transplant types, the cortical screws showed the significantly highest values in the fibula and the lowest values in the iliac crest. The best retention was found in the combination of cancellous screws with fibular graft (514.8 N + -252.3 N). For the flat bones (i.e., scapular and illiac crest) we recommend the cancellous screws.

Routine preoperative colour Doppler duplex ultrasound scanning in anterolateral thigh flaps.

The anterolateral thigh flap (ALT) is often used to reconstruct the head and neck and depends on one or more skin perforators, which often present with variable anatomy. The aim of this study was to localise and evaluate the precise position of these perforators preoperatively with colour Doppler duplex ultrasound scanning (US). We detected 74 perforators in 30 patients. The mean duration of examination with colour Doppler was 29 (range 13-51) minutes. Adequate perforators and their anatomical course could be detected preoperatively extremely accurately (p<0.001). The mean difference between the preoperatively marked, and the real, positions was 6.3 (range 0-16) mm. There was a highly significant correlation between the accuracy of the prediction and the body mass index of the patient (0.75; p<0.001). Neither the age nor the sex of the patient correlated with the accuracy of the prediction. Colour Doppler duplex US used preoperatively to localise perforators in ALT flaps is reliable and could be adopted as standard procedure.

Quantitative comparison of the expression of antimicrobial peptides in the oral mucosa and extraoral skin.

Antimicrobial peptides (AMP) defend epithelial surfaces against pathological micro-organisms. We know of no comparison of their expression between the oral mucosa and extraoral epithelium, but knowledge of differences in their quantities is of interest, possibly as a starting point for new treatments. Expression of AMP human beta-defensin (hBD)-1/-2/-3 and psoriasin in the oral mucosa and extraoral epithelium of the head and neck were measured by real-time polymerase chain reaction (RT-PCR) (n=14), immunohistochemistry (n=6), and western blot (n=8). RT-PCR showed that all the genes investigated were expressed significantly more in the oral mucosa than in the skin (hBD-1: p=0.002; hBD-2: p=0.006; hBD-3: p=0.035; psoriasin: p=0.02). Immunohistochemistry and western blot showed differential concentrations of proteins: hBD-2 (p=0.021) and hBD-3 (p=0.043) were pronounced in the oral mucosa, whereas psoriasin was raised in the extraoral skin (p=0.021). There was no difference in protein concentrations for hBD-1 (p=0.08). The observed differences in the expression of AMP may be important for new treatments such as topical application of AMP derivatives.