Preliminary study of reliability of transcutaneous sensors in measuring intraabdominal pressure.

Early recognition of elevated intraabdominal pressure (IAP) in critically ill patients is essential, since it can result in abdominal compartment syndrome, which is a life-threatening condition. The measurement of intravesical pressure is currently considered the gold standard for IAP assessment. Alternative methods have been proposed, where IAP assessment is based on measuring abdominal wall tension, which reflects the pressure in the abdominal cavity. The aim of this study was to evaluate the feasibility of using patch-like transcutaneous sensors to estimate changes in IAP, which could facilitate the monitoring of IAP in clinical practice. This study was performed with 30 patients during early postoperative care. All patients still had an indwelling urinary catheter postoperatively. Four wearable sensors were attached to the outer surface of the abdominal region to detect the changes in abdominal wall tension. Additionally, surface EMG was used to monitor the activity of the abdominal muscles. The thickness of the subcutaneous tissue was measured with ultrasound. Patients performed 4 cycles of the Valsalva manoeuvre, with a resting period in between (the minimal resting period was 30 s, with a prolongation as necessary to ensure that the fluid level in the measuring system had equilibrated). The IAP was estimated with intravesical pressure measurements during all resting periods and all Valsalva manoeuvres, while the sensors continuously measured changes in abdominal wall tension. The association between the subcutaneous thickness and tension changes on the surface and the intraabdominal pressure was statistically significant, but a large part of the variability was explained by individual patient factors. As a consequence, the predictions of IAP using transcutaneous sensors were not biased, but they were quite variable. The specificity of detecting intraabdominal pressure of 20 mmHg and above is 88%, with an NPV of 96%, while its sensitivity and PPV are currently far lower. There are inherent limitations of the chosen preliminary study design that directly caused the low sensitivity of our method as well as the poor agreement with the gold standard method; in spite of that, we have shown that these sensors have the potential to be used to monitor intraabdominal pressure. We are planning a study that would more closely resemble the intended clinical use and expect it to show more consistent results with a far smaller error.

Material properties of human patellar-ligament grafts from the elderly population.

The aim of the presented study was to estimate the material properties of human patellar ligaments from the elderly population by means of tensile tests. The experimental part was conducted on a custom tensile-testing device, with a built-in enclosure to simulate in-vivo conditions, using 25 (15 female, 10 male) bone-ligament-bone samples from elderly (age 83 (8)) human donors. During the tensile tests, the resultant force and displacement of the sample attachments were recorded. With this data and the values of the initial length and the initial cross-sectional area of the samples, the engineering stress and strain, the Young's modulus and the toughness at rupture were calculated for each sample. The results were then averaged and presented for all the samples together and for the female and male populations separately. The measured Young's modulus and the failure stress values were found to be significantly higher for the female samples compared to the male (p < 0.05). All the other measured properties did not show a significant difference. The toe region's material properties for the patellar ligament were also presented as valuable information for the anterior cruciate ligament reconstruction. The tensile-test results were compared to other research carried on human patellar ligaments using samples from younger donors. The comparison showed that the samples from the elderly population exhibit lower values of strain at the end of the toe region and have a lower failure strain for the patellar ligament. The Young's modulus and the failure stress of the samples in this study were in the range of other research conducted on patellar ligaments.

Analysis of the mechanical response of damaged human cervical spine ligaments.

BACKGROUND: Cervical spine ligaments that protect the spinal cord and stabilize the spine are frequently injured in motor vehicle collisions and other traumatic situations. These injuries are usually incomplete, and often difficult to notice. The focus of the presented study is placed on analysis of the effect of subfailure load on the mechanical response of the three main cervical spine ligaments: the anterior and the posterior longitudinal ligament and the ligamentum flavum. METHODS: A total of 115 samples of human cadaveric ligaments removed within 24-48 h after death have been tested. Uniaxial tension tests along the fiber direction were performed in physiological conditions on a custom designed test equipment. The ligaments were loaded into an expected damage zone at two different subfailure values (based on previously reported reference group of 46 samples), and then reloaded to failure. FINDINGS: The main effect of a high subfailure load has proven to be the toe elongation change. The toe elongation increase is affected by the subfailure load value. While anterior and posterior longitudinal ligament showed similar changes, the smallest subfailure effect was found in ligamentum flavum. INTERPRETATIONS: The normal physiological region of the cervical spine ligaments mechanical response is modified by a high subfailure load. The observed ligament injury significantly compromises ligament ability to give tensile support within physiological spinal motion.

Morphological Characteristics and Frequency of Accessory Right Hepatic Veins - Evaluation with Computed Tomography.

In the liver, there are many vascular variants, which are important in liver surgery, the presence of accessory right hepatic veins (aRHVs) in particular. Th eir frequency, number and diameter vary considerably. Detailed imaging diagnostics with computed tomography (CT) should be undertaken before surgery. Th e aim of our study was to examine the characteristics of aRHVs and their demographic correlations. Th e study included data on 188 patients that underwent CT examination of the abdomen with contrast media, 103 men (54.8%) men and 85 (45.2%) women, mean age 63.1±14.3 (range, 21-94) years. Th e measurements of hepatic veins were carried out on CT images, which were obtained from the Clinical Institute of Radiology, University Medical Centre of Ljubljana. Forty-fi ve of 142 patients had at least one aRHV: one aRHV in 37 (26.1%) cases, two aRHVs in seven (4.9%) cases, and three aRHVs in one (0.7%) case. Th e incidence of aRHV was between 24% and 39.3% (mean, 31.7%) and of more than one aRHV between 2.3% and 10.3% with 95% confi dence interval (CI). Based on the test of proportions, the proportion of cases with inferior aRHV of at least 7 mm was between 7.2% and 18.1% with 95% CI. Th e mean distance between the aRHV and the main RHV confl uences into the inferior vena cava was 3.73 cm (between 3.32 cm and 4.13 cm, 95% CI). Th e proportion of cases with confl uence distance of at least 4 cm was between 21.6% and 49.5% in cases with at least one aRHV. In cases with more than one aRHV, the distance between the middle aRHV and the main RHV ranged from 1.90 cm to 4.32 cm (95% CI). Th e T-test of independent samples showed no eff ect of age on the incidence of accessory veins (p=0.18), and the test of diff erences of interests showed no impact of sex (p=0.75). Evaluation of the incidence and diameter of aRHVs is of great importance for safe surgical procedure. Th eir presence can change the surgeon's decision in 10%-20% of cases when employing appropriate imaging technique. CT examination, which is easily accessible and minimally invasive for patients, was successful in only 80% cases, when using standard protocol for CT scanning.

A Novel Approach to Measuring Muscle Mechanics in Vehicle Collision Conditions.

The aim of the study was to evaluate a novel approach to measuring neck muscle load and activity in vehicle collision conditions. A series of sled tests were performed on 10 healthy volunteers at three severity levels to simulate low-severity frontal impacts. Electrical activity-electromyography (EMG)-and muscle mechanical tension was measured bilaterally on the upper trapezius. A novel mechanical contraction (MC) sensor was used to measure the tension on the muscle surface. The neck extensor loads were estimated based on the inverse dynamics approach. The results showed strong linear correlation (Pearson's coefficient = 0.821) between the estimated neck muscle load and the muscle tension measured with the MC sensor. The peak of the estimated neck muscle force delayed 0.2 ± 30.6 ms on average vs. the peak MC sensor signal compared to the average delay of 61.8 ± 37.4 ms vs. the peak EMG signal. The observed differences in EMG and MC sensor collected signals indicate that the MC sensor offers an additional insight into the analysis of the neck muscle load and activity in impact conditions. This approach enables a more detailed assessment of the muscle-tendon complex load of a vehicle occupant in pre-impact and impact conditions.

Knee stiffness and viscosity: New implementation and perspectives in prosthesis development.

The pendulum test is a method applied to measure passive resistance of the knee. A new and simple pendulum test with instrumentation based on infrared camera was used to evaluate knee stiffness and viscosity on a female human cadaver. The stiffness and viscosity were calculated based on the kinetic data. During the measurements, the periarticular and intraarticular soft tissue of the knee was gradually removed to determine the stiffness and viscosity as a function of the tissue removal rate. The measurements showed that the removal of tissue around the joint reduces the damping of leg oscillation, and therefore decreases the stiffness and viscosity. The contribution to knee joint damping was 10% for the skin, 20% for ligaments, and 40% for muscles and tendons. Tissue removal has a very large impact on the knee stiffness and viscosity.

Failure properties and damage of cervical spine ligaments, experiments and modeling.

Cervical spine ligaments have an important role in providing spinal cord stability and restricting excessive movements. Therefore, it is of great importance to study the mechanical properties and model the response of these ligaments. The aim of this study is to characterize the aging effects on the failure properties and model the damage of three cervical spine ligaments: the anterior and the posterior longitudinal ligament and the ligamentum flavum. A total of 46 samples of human cadaveric ligaments removed within 24-48 h after death have been tested. Uniaxial tension tests along the fiber direction were performed in physiological conditions. The results showed that aging decreased the failure properties of all three ligaments (failure load, failure elongation). Furthermore, the reported nonlinear response of cervical ligaments has been modeled with a combination of the previously reported hyperelastic and damage model. The model predicted a nonlinear response and damage region. The model fittings are in agreement with the experimental data and the quality of agreement is represented with the values of the coefficient of determination close to 1.

Intrahepatic venous anastomoses with a focus on the middle hepatic vein anastomoses in normal human livers: anatomical study on liver corrosion casts.

PURPOSE: The aim of this study is to present the anatomical data about intrahepatic venous anastomoses found in normal human livers. The focus is on the middle hepatic vein (MHV) anastomoses, because their existence or non-existence could be of crucial importance in tumour resections as well as in split or living donor liver transplantations. MATERIALS AND METHODS: The frequency of livers with intrahepatic venous anastomoses was determined on 164 corrosion casts and the diameter of each anastomosis was measured. Additionally, the type of connection and the position within the liver (liver segment) was determined for each MHV anastomosis. RESULTS: Intrahepatic venous anastomoses were found in 46 % (75/164), whereas MHV anastomoses were found in 28 % (44/164) of liver casts. Most commonly (39/44), MHV had anastomotic connections with the right hepatic vein (RHV), and also with the inferior RHV, the left hepatic vein and the short subhepatic vein. In more than three quarters of liver casts, MHV-RHV anastomoses were found in liver segment 8; in 45 % of cases, there was more than one anastomosis in this liver segment. The diameter of MHV-RHV anastomoses found in segment 8 was ≥1 mm in 90.6 % of cases. CONCLUSION: As MHV anastomoses were present in more than a quarter of all examined liver casts, we believe that detailed anatomical data presented in this article, together with up to date radiologic technics which enable even 3D reconstruction of venous anastomoses in the liver, could contribute to the clinician's decisions when planning surgical procedures.

Muscles within muscles: a tensiomyographic and histochemical analysis of the normal human vastus medialis longus and vastus medialis obliquus muscles.

The aim of this study was to show the connection between structure (anatomical and histochemical) and function (muscle contraction properties) of vastus medialis obliquus (VMO) and vastus medialis longus (VML). The non-invasive tensiomyography (TMG) method was used to determine the contractile properties (contraction time; T(c)) of VML and VMO muscle, as a reflection of the ratio between the slow and fast fibers in two groups of nine young men. VML and VMO significantly (P < 0.01) differ in the proportion of type 1 (59.6: 44%) and type 2b (6.3: 15%) fibers. The VML muscle is almost entirely composed of type 1 and type 2a fibers. In many samples of this muscle no type 2b fibers were found. The proportion of slow-twitch type 1 fibers is nearly twice as high as the proportion of fast-twitch type 2a fibers. These observations indicate that VML is a slower and more fatigue-resistant muscle than VMO muscle. These characteristics correspond to the different functions of the VML, which is an extensor of the knee, and to the VMO, which maintains the stable position of the patella in the femoral groove. Our results obtained by TMG provided additional evidence that muscle fibers within the segments of VM muscle were not homogenous with regard to their contractile properties, thereby confirming the histochemical results. T(c) can be attributed to the higher percentage of slow-twitch fibers - type 1. The statistically shorter T(c) (P ≤ 0.001) of VMO (22.8 ±â€…4.0 ms) compared with VML (26.7 ±â€…4.0 ms) in our study is consistent with previously found differences in histochemical, morphological and electrophysiological data. In conclusion, the results of this study provide evidence that the VML and VMO muscles are not only anatomically and histochemically different muscles, but also functionally different biological structures.

Deep inferior epigastric perforator flap: an anatomical study of the perforators and local vascular differences.

The objective of this study was to determine precise localization and external diameter of the lower abdominal wall perforators as well as to investigate some vascularity differences between the same parts of perfusion zones II and III according to Hartrampf perfusion zones. The study was performed on 10 fresh cadavers (20 hemiabdomens) using the gelatin injection technique. All perforators were identified, and their localization and diameter were noted. Measurements were made at the level of the fascia. We noted localization and diameter of arteries on cross-sectional planes of either part of the flap. The median sum of the external diameter of all arteries in zone I was 17.01 mm. The median sum of the external diameter of all arteries in the medial 1/3 part of zone III was 4.17 mm, and in the medial 1/3 part of zone II, it was 0.96 mm. The median sum of the external diameter of all arteries in the intermediary 1/3 part of zone III was 2.16 mm, whereas in the intermediary 1/3 part of zone II, it was 0.81 mm. Significant differences were recorded between proximal and middle horizontal regions of zones II and III and between medial vertical part of zone III and medial vertical part of zone II. Anastomoses between zones I and II are considerably smaller compared with anastomoses between zones I and III. The best vascularized parts of the lower abdominal wall were perfusion zone I, then the inner 2/3 of zone III and medial 1/3 of zone II.

Anatomy of the ligamentum venosum arantii and its contribution to the left hepatic vein and common trunk control. A study on cadaveric livers.

BACKGROUND: The control of the left hepatic vein (LHV) and the common trunk of the middle hepatic vein (MHV) and LHV (CT) is considered difficult during liver resection and could be improved by detailed knowledge on the ligamentum venosum Arantii (LV). AIM: The aim of this study was to describe the LV and its connections to the LHV and the CT and to present surgical relevance of the obtained data. MATERIAL AND METHODS: During autopsy of 50 cadavers of both sexes, the LV was exposed, measured and then dissected, simulating a surgical maneuver to facilitate the approach to the LHV and CT. The extrahepatic parts of the LHV, MHV and CT were measured. RESULTS: The LV was 52-70 mm long and 5-8 mm thick. It had a fibrotic structure and was not patent in 96% of the cases. The extrahepatic part of the LHV measured 3-19 mm, that of the MHV 3-18 mm and that of the CT 4-15 mm. CONCLUSION: LV dissection facilitated extraparenchymatous clamping of the hepatic veins: the extrahepatic parts of the LHV and CT measured > 3 mm in 86 and 84% of the cases, respectively.

Anatomy and surgical relevance of the hepatocaval ligament. A study on cadaveric livers.

BACKGROUND: There are nearly no data on the hepatocaval ligament (HCL) in the anatomical literature, though it is of high importance during surgery of the right hemiliver. AIM: The aim of this study was to determine the frequency of the HCL, its description and its relations to the inferior vena cava (IVC) and the right hepatic vein (RHV) as well as the evaluation of the surgical relevance of the data obtained. MATERIALS AND METHODS: The dissection of the livers of 43 cadavers of both sexes was performed and the presence of the HCL was established. The ligament was measured and dissected to expose the IVC and the extrahepatic part of the RHV from its inflow to the liver parenchyma. RESULTS: The ligament was present in 77% of the cases. It was 12-35 mm long and 3-18 mm wide. The extrahepatic part of the RHV was 2-12 mm long. CONCLUSION: Dissection of the HCL revealed the terminal extrahepatic part of the RHV in all cases. Anatomically, resection of the right hemiliver with elective vascular control would be possible in 85% of the cases in which the length of the extrahepatic part of the RHV was > or =3 mm.

Giant T-shaped duplication of the transverse colon. A case report.

A case of long diverticular colonic duplication producing acute abdominal pain in a 6-year-old girl is presented. Physical examination showed no signs of acute abdomen at the initial presentation. After a pain-free interval, there was a sudden onset of severe abdominal pain and a large tumor in the lower abdomen was observed. A plain x-ray showed an enormously dilated colonic pouch filled with gas. Excision of the T-shaped duplication and small part of the transverse colon was successful. Because of extensive fibrotic changes in the colon near the opening of duplication, a resection margin of at least 2 cm is recommended.

Anatomical basis of the liver hanging maneuver.

BACKGROUND/AIMS: The anterior approach to right hepatectomy using the liver hanging maneuver without liver mobilization claims to be anatomically evaluated. During this procedure a 4 to 6-cm blind dissection between the inferior vena cava and the liver is performed. Short subhepatic veins, entering the inferior vena cava could be torn and a hemorrhage, difficult to control, could occur. METHODOLOGY: On 100 corrosive casts of livers the anterior surface of the inferior vena cava was studied to evaluate the position, diameter and draining area of short subhepatic veins and inferior right hepatic vein. The width of the narrowest point on the planned route of blind dissection was determined. RESULTS: The average value of the narrowest point on the planned route of blind dissection was 8.7+/-2.3mm (range 2-15mm). The ideal angle of dissection being 0 degrees was found in 93% of cases. In 7% we found the angle of 5 degrees toward the right border of inferior vena cava to be the better choice. CONCLUSIONS: Our results show that liver hanging maneuver is a safe procedure. With the dissection in the proposed route the risk of disrupting short subhepatic veins is low (7%).

Congruence between the courses of the biliary ductal and the hepatic arterial systems.

The development of diagnostic methods and new surgical techniques means it is increasingly important to have accurate knowledge of the anatomy of the hepatic arterial and biliary systems, including their variations, at extrahepatic and intrahepatic levels. The aim of this study was to determine how often the biliary and arterial systems run together and branch in the same pattern. Fifty corrosion casts of the liver were used to analyse the origin and branching patterns of arteries and the confluences of bile ducts. In addition, both systems were analysed to determine the frequency of normal arrangements and variations. The congruence of the course of both systems was analysed at the porta hepatis and in the left and right hemilivers down to the segmental level. A congruent course of the arterial and the biliary systems was identified in 38% of cases at the porta hepatis, in 32% of cases in the left hemiliver and in 30% of the right hemiliver. The congruence of both systems at the porta hepatis and in the left hemiliver was identified only if both systems were normal. In the right hemiliver, however, the congruence of both systems was identified even when both systems were variable, but only in 10% of cases. The results of the study show that, on the basis of knowledge of the course and branching of one system, the other system cannot be predicted.

Anatomical variations of the right hepatic veins and their relevance to surgery.

BACKGROUND/AIMS: In a morphological study of the right hepatic veins anatomical characteristics of surgical importance were looked for. METHODOLOGY: 110 cadaveric human livers were prepared by the corrosion casts method. The confluence patterns of the superior right hepatic vein, the hepatocaval confluence, the accessory right hepatic veins and the anastomoses between hepatic veins in the right hemiliver were examined. RESULTS: Four types of the superior right hepatic vein, based on the length of its trunk and the confluence pattern of its main tributaries were determined and their frequency was calculated. Type I was found in 20%, type II in 40%, type III in 25% and type IV in 15%. Accessory right hepatic veins with a minimal caliber of 0.4 cm, which were always present in type IV, were also found in other types, all together in 27% of the casts. The tributary-free part of the superior right hepatic vein at hepatocaval confluence was longer than 1 cm in 77%. In the right hemiliver 109 anastomoses were found in 29/110 liver casts. CONCLUSIONS: Knowing the characteristics of different superior right hepatic vein types and of the accessory right hepatic veins may be useful in segment-oriented liver resections and in right side living donor resections.

Anatomical variations of the cystic artery.

Thorough knowledge about the origin of the cystic artery is surgically important, especially when intraoperative or post-operative bleeding occurs in the gallbladder fossa. The arterial supply of the gallbladder was studied in 81 livers. The gallbladder was supplied by one cystic artery in 86% and by two arteries in 14% of cases. When a single artery was present, it originated from the right hepatic artery in 53% of livers. Other origins included the anterior or the posterior sectional hepatic artery, the replacing right hepatic artery, and in 5% of cases, segmental arteries for segments 4, 5, 6 and 8. When two cystic arteries supplied the gallbladder, both most commonly originated from the right hepatic artery (7% incidence). In 1% of cases, a subsegmental branch for segment 6 and a subsegmental branch for segment 5 respectively, originated from the cystic artery.

Anatomical variations of the arterial pattern in the left hemiliver.

The arterial supply to the left hemiliver was studied in 70 liver casts. The arteries were divided into 15 groups according to their origin and branching pattern. The left hemiliver was supplied by one artery in 53% of cases, by two arteries in 40% and by three arteries in 7%. The left hepatic artery, which originated from the proper hepatic artery, supplied all three left segments in 39% of specimens. The replacing left hepatic artery, which originated from the left gastric artery, supplied the whole left hemiliver in 3% of cases. The incomplete, replacing left hepatic artery supplied segments 2, 3 and a part of segment 4 in 6% of cases, and only segments 2 and 3 in 11%. There was one segmental artery for segment 2 in 86%, and two in 14%. Segment 3 was supplied by one artery in 87%, and by two in 13%. Segment 4 was supplied by one artery in 39% of cases, by two arteries in 43%, by three in 14% and by four arteries in 4%.

Anatomical variations of the arterial pattern in the right hemiliver.

The arterial supply to the right hemiliver was studied in 80 liver casts. The arteries were divided into 10 groups according to their origin and branching pattern. The right hemiliver was supplied by one artery in 96% of cases and by two arteries in 4%. When there was only one artery it originated from the proper hepatic artery in 73/77 cases and from the superior mesenteric artery in 4/77 cases. The replacing right hepatic artery which originated from the superior mesenteric vessel supplied the whole right hemiliver in 5% of cases. The incomplete replacing right hepatic artery which supplied only a part of the right hemiliver was found in 4% of cases. The anterior section (segments 5 and 8) was supplied by one artery in 61%, by two arteries in 30% and by three arteries in 9% of cases. The posterior section (segments 6 and 7) was supplied by one artery in 66%, by two arteries in 31% and by three arteries in 3% of cases. Segments 5 and 7 were predominantly supplied by one artery, whereas segments 6 and 8 by two arteries.