Theoretical simulation of temperature elevations in a joint wear simulator during rotations.

The objective of this study is to develop a theoretical model to simulate temperature fields in a joint simulator for various bearing conditions using finite element analyses. The frictional heat generation rate at the interface between a moving pin and a stationary base is modeled as a boundary heat source. Both the heat source and the pin are rotating on the base. We are able to conduct a theoretical study to show the feasibility of using the COMSOL software package to simulate heat transfer in a domain with moving components and a moving boundary source term. The finite element model for temperature changes agrees in general trends with experimental data. Heat conduction occurs primarily in the highly conductive base component, and high temperature elevation is confined to the vicinity of the interface in the pin. Thirty rotations of a polyethylene pin on a cobalt-chrome base for 60 s generate more than 2.26 °C in the temperature elevation from its initial temperature of 25 °C at the interface in a baseline model with a rotation frequency of 0.5 Hz. A higher heat generation rate is the direct result of a faster rotation frequency associated with intensity of exercise, and it results in doubling the temperature elevations when the frequency is increased by100%. Temperature elevations of more than 7.5 °C occur at the interface when the friction force is tripled from that in the baseline model. The theoretical modeling approach developed in this study can be used in the future to test different materials, different material compositions, and different heat generation rates at the interface under various body and environmental conditions.

Evaluation of phrenic nerve stimulation trigger lag and synchronization in different modes of ventilation.

Phrenic nerve stimulation is currently being investigated for the prevention of diaphragm atrophy in patients with mechanically supported breathing. Patients receiving breathing support from mechanical ventilation are at risk of mismatches between respiratory demand and ventilator support. Our objectives were to determine if a novel phrenic nerve stimulation device provided stimulation during inspiration as intended and did not exacerbate any potential discordances. A benchtop electromechanical simulation model was developed to validate phrenic nerve stimulation with simulated breathing. The phrenic nerve stimulation device was evaluated with a mechanical ventilator attached to a breathing simulator. The trigger ratio and time lag between phrenic nerve stimulation and mechanical ventilation was measured for multiple disease and ventilator parameters. For the 1:1 breath trigger ratio test, 99.79% of intended stimulation breaths received stimulation at the correct time. For the 1:4 breath trigger ratio test, 99.72% of intended stimulation breaths received stimulation at the correct time. For trigger lag times for the inspiratory and expiratory phases, the mean inspiratory lag was 36.10 ± 10.50 ms and 16.61 ± 3.61 ms, respectively. The following discordance scenarios were evaluated in conjunction with simulated phrenic nerve stimulation: asynchrony-false trigger, dyssynchrony-early trigger, dyssynchrony-late trigger, dyssynchrony-early cycling, dyssynchrony-late cycling. Testing demonstrated none of these discordances were exacerbated by the simulated phrenic nerve stimulation. The novel phrenic nerve stimulation device delivered electrical stimulation therapy as intended and did not exacerbate any simulated discordances.

Hepatic Portal Venous Gas: An Ill Omen or a Misleading Sign.

Hepatic portal venous gas (HPVG), a rare radiological finding, is historically considered an ominous sign with 100% mortality rates. The dictum that HPVG warrants surgical intervention is challenged in the recent literature. This is because of the identification of various causes of HVPG other than bowel gangrene. Most of these newly identified causes can be managed conservatively. However, bowel gangrene, if missed, is fatal. Hence, sound clinical judgment and accurate diagnosis based on specific clinical parameters and imaging findings are important. We present a case of a young male with tumor lysis syndrome and neutropenic sepsis. He underwent treatment for a relapse of T-cell acute lymphocytic leukemia and presented with abdominal pain and distension. Computed tomography (CT) scan showed HPVG, and the differential diagnosis was neutropenic colitis or pseudomembranous colitis, with steroid use as the probable cause. The patient was managed conservatively. The case emphasizes that the evaluation for a specific cause of HPVG is important to reduce unnecessary surgery. A succinct literature review provides the reasons for the changing mortality rates.

Roux-en-Y fistulojejunostomy in the management of persistent external pancreatic fistula: is it olde worlde?

OBJECTIVES: This article aimed to identify patient selection criteria and approach in treating persistent external pancreatic fistulas surgically with Roux-en-Y fistulojejunostomy, and the study evaluated the outcomes of Roux-en-Y fistulojejunostomy with a review of the relevant literature. MATERIAL AND METHODS: A retrospective data analysis from January 2010 to May 2017 revealed 6 patients managed with Roux-en-Y fistulojejunostomy for persistent external pancreatic fistulas, and their details were entered in a proforma. Standard surgical steps were performed in all patients, and the patients were followed up postoperatively for 1 year. Data were analyzed for outcomes, and the literature was reviewed. RESULTS: Four of 6 patients had persistent external pancreatic fistulas following pancreatic necrosectomy, 1 had surgery for pancreatic pseudocyst, and 1 after pancreaticoduodenectomy for pancreatic head mass. An average duration of conservative management was 14 weeks, and Roux-en-Y fistulojejunostomy was performed at a median distance of 6 cm from pancreas via a midline laparotomy. All patients recovered without major complications. Only 1 patient developed diabetes at a 1-year follow-up. CONCLUSION: Fistulojejunostomy is a safe and effective treatment for persistent pancreatic fistula having the benefit of avoiding a difficult major pancreatic resectional surgery in an already debilitated patient with frozen tissue planes, along with low postoperative morbidity and mortality. The short- and mid-term outcomes in the literature for this procedure are good, as it has also been seen in our study on diverse indications.

An outcome analysis of laparoscopic management of diverticulitis.

BACKGROUND: All operative procedures for simple or complicated diverticulitis, including primary resection and anastomosis (PRA) with or without a diverting stoma, Hartmann procedure (HP), or stoma reversal, whether done in an elective setting or as an emergency, can be performed laparoscopically. However, owing to low incidence of the disease and complexity of the procedure, there are very few studies on outcomes of laparoscopic surgery for sigmoid diverticulitis from India. AIM: The present study was undertaken to evaluate outcomes of laparoscopically treated patients of sigmoid diverticulitis. METHODS: Prospective observational study enrolled 37 patients with sigmoid diverticulitis managed laparoscopically from March 2015 to March 2017. Demographic, clinical, operative, postoperative, and complication data were entered into a patient proforma and analyzed. RESULTS: Eleven simple and 26 complicated diverticulitis patients were operated laparoscopically, 22 in emergency setting and 15 in elective setting. Only three patients required conversion to open surgery-two due to dense adhesions and one due to chronic obstructive pulmonary disease (COPD). No patients had ureteric or bowel injury. Eighteen patients underwent laparoscopic PRA without stoma, 11 patients had PRA with stoma, 6 had HP, and 2 had laparoscopic lavage. Results showed lesser blood loss, shorter hospital stay, and fewer complications in the elective group and simple diverticulitis patients. None of the patients had anastomosis-related complications. Two patients had stoma-related complications. CONCLUSION: Laparoscopic management of diverticulitis is feasible, safe, provides the benefits of less wound-related complications, and shorter hospital stay and should be the surgical procedure of choice in elective or emergency setting for simple/complicated diverticulitis.

Roux-en-Y fistulojejunostomy in the management of persistent external pancreatic fistula: Is it olde worlde?

OBJECTIVE: This article aims to identify the patient selection criteria and approach in treating persistent external pancreatic fistulas surgically with Roux-en-Y fistulojejunostomy, and it evaluates the outcomes of Roux-en-Y fistulojejunostomy with a review of the relevant literature. MATERIAL AND METHODS: A retrospective data analysis from January 2010 to May 2017 revealed 6 patients who were managed with Roux-en-Y fistulojejunostomy for persistent external pancreatic fistulas, and their details were entered in a proforma. Standard surgical steps were performed in all patients, and the patients were followed up postoperatively for 1 year. Data were analyzed for outcomes, and the literature was reviewed. RESULTS: Four of 6 patients had persistent external pancreatic fistulas following pancreatic necrosectomy, 1 had surgery for pancreatic pseudocyst, and 1 after pancreaticoduodenectomy for pancreatic head mass. An average duration of conservative management was 14 weeks, and Roux-en-Y fistulojejunostomy was performed at a median distance of 6 cm from pancreas via a midline laparotomy. All patients recovered without major complications. Only 1 patient developed diabetes at a 1-year follow-up. CONCLUSION: Fistulojejunostomy is a safe and effective treatment for persistent pancreatic fistula having the benefit of avoiding a difficult major pancreatic resectional surgery in an already debilitated patient with frozen tissue planes, along with low postoperative morbidity and mortality. The short- and mid-term outcomes in the literature for this procedure are good, as it has also been seen in our study on diverse indications.

Ileal duplication cyst in the elderly complicated by appendicitis: A rare case report and review of literature.

INTRODUCTION: Gastrointestinal duplication cysts are rare, generally found in infants and young adults. Adult presentation is rare. PRESENTATION OF THE CASE: We present an elderly lady who presented with right iliac fossa pain. Imaging showed a terminal ileal duplication cyst. Laparoscopic right hemicolectomy was done. Histopathology confirmed ileal duplication cyst with reactive appendicitis. DISCUSSION: Surgical resection is deemed appropriate management due to known complications like obstruction, hemorrhage, perforation and malignant degeneration. Resection of only the cyst is adequate in completely isolated cases. However, others require resection of adjoining small bowel. CONCLUSION: We highlight the rare occurrence in elderly and its management laparoscopically.

Development of a clinically relevant impingement test method for a mobile bearing lumbar total disc replacement.

BACKGROUND CONTEXT: Total disc arthroplasty is an alternative therapy to spinal fusion for the treatment of neck or low back pain and is hypothesized to reduce the risk of disease progression to the adjacent spinal levels. Radiographic and retrieval analyses of various total disc replacements (TDRs) have shown evidence of impingement damage. Impingement of TDRs can occur when the device reaches the limits of its functional range of motion, causing contact between peripheral regions of the device. PURPOSE: Impingement can be associated with increased wear and mechanical damage; however, impingement conditions are not simulated in current standardized mechanical bench test methods. This study explored the test conditions necessary to apply clinically relevant impingement loading to a lumbar TDR in vitro. STUDY DESIGN: An experimental protocol was developed and evaluated using in vivo retrievals for qualitative and quantitative validation. METHODS: Retrieval analysis was conducted on a set of 11 size 3 retrieved Charité devices using American Society for Testing and Materials F561 as a guide. The impingement range of motion was determined using a combination of modeling and experiments, and was used as an input in vitro testing. A 1-million cycle in vitro test was then conducted, and the in vitro samples were characterized using methods similar to the retreived devices. RESULTS: All in vitro tested samples exhibited impingement regions and damage patterns consistent with retrieved devices. Consistent with the retrievals, the impingement damage on the rim was a combination of abrasive wear and plastic deformation. Micro computed tomography (microCT) was used to quantitatively assess rim damage due to impingement. Rim penetration was statistically lower in the retrievals when compared with both in vitro groups. Rim elongation was comparable among all groups. The simulated-facet group had statistically greater angular rim deformations than the retrieval group and the no-facet group. CONCLUSIONS: Results demonstrate that clinically relevant impingement seen on mobile bearings of lumbar TDRs can be replicated on the bench.

Small bowel obstruction due to an endometriotic ileal stricture with associated appendiceal endometriosis: A case report and systematic review of the literature.

INTRODUCTION: Endometriosis is defined as the presence of functional ectopic endometrial tissue outside the uterine cavity. It rarely involves the small bowel and obstruction due to the same is highly uncommon. Preoperative diagnosis is difficult based on clinical and radiological studies. Diagnosis can be confirmed only on histopathological examination of the surgically resected specimen. PRESENTATION OF CASE: A 44 years old lady presented with repeated episodes of abdominal pain, non bilious vomiting and diarrhea. She also gave history of abdominal pain during every menstruation. She had diffuse abdominal tenderness and the computed tomography showed a concentric infective/inflammatory thickening of the distal ileum. Colonoscopy confirmed a tight distal ileal stricture After a failed trial of conservative management, she underwent a laparoscopic right hemicolectomy. The histopathological examination revealed multiple endometriotic foci in the ileum and the appendix. DISCUSSION: Ileal endometriosis presenting as obstruction is uncommon and very few cases have been reported thus far. The symptoms are usually cyclical but may later become continuous with the progression of the disease. Preoperative diagnostic dilemma is due to the clinical and the radiological similarities to inflammatory, infective and irritable bowel diseases. CONCLUSION: Ours is probably the first case of small bowel obstruction due to ileal and appendiceal endometriosis that was managed with laparoscopic right hemicolectomy. We highlight the preoperative diagnostic dilemma and the progression of the cyclical symptoms. Thus, endometriosis must be considered in cases of small bowel obstruction in women in the reproductive age group as a rare cause.

Laparoscopic management of a two staged gall bladder torsion.

Gall bladder torsion (GBT) is a relatively uncommon entity and rarely diagnosed preoperatively. A constant factor in all occurrences of GBT is a freely mobile gall bladder due to congenital or acquired anomalies. GBT is commonly observed in elderly white females. We report a 77-year-old, Caucasian lady who was originally diagnosed as gall bladder perforation but was eventually found with a two staged torsion of the gall bladder with twisting of the Riedel's lobe (part of tongue like projection of liver segment 4A). This together, has not been reported in literature, to the best of our knowledge. We performed laparoscopic cholecystectomy and she had an uneventful post-operative period. GBT may create a diagnostic dilemma in the context of acute cholecystitis. Timely diagnosis and intervention is necessary, with extra care while operating as the anatomy is generally distorted. The fundus first approach can be useful due to altered anatomy in the region of Calot's triangle. Laparoscopic cholecystectomy has the benefit of early recovery.

Correction of discrepancy between prescribed and actual blood flow rates in chronic hemodialysis patients with use of larger gauge needles.

The blood flow rate delivered by the dialysis machine (d-BFR) may not be accurately reflected by the blood flow rate set on the machine (sm-BFR). High negative arterial pressure may lead to deformity of the blood pump-segment tubing, resulting in a lower stroke volume and d-BFR. The Hagen-Poiseuille law predicts that the use of larger gauge needles should make arterial pressure less negative. Twenty-two patients on chronic hemodialysis therapy with a percentage of reduction in urea (PRU) levels less than 65% and/or a greater than 10% difference between sm-BFR and d-BFR underwent dialysis using one-gauge larger arterial and venous needles. d-BFR increased by 23 +/- 5 mL/min. Arterial pressure became less negative by 58 +/- 5 mmHg, and venous pressure decreased by 31 +/- 7 mm Hg. Changes in arterial and venous pressures allowed sm-BFR to be increased to 500 mL/min in all 22 patients, resulting in an increase in d-BFR of 83 +/- 7 mL/min. This translated into an increase in PRU of 5% +/- 0.01%. All results were significant at P < 0.001. A survey showed that less than 5% of needles used in our region were 14 G. This study shows that the use of larger gauge needles can significantly increase d-BFR and PRU as a result of changes in arterial and venous pressures, resulting in a significantly increased dialysis dose at no additional cost.

Gold nanoparticle-based detection of genomic DNA targets on microarrays using a novel optical detection system.

The development of a nanoparticle-based detection methodology for sensitive and specific DNA-based diagnostic applications is described. The technology utilizes gold nanoparticles derivatized with thiol modified oligonucleotides that are designed to bind complementary DNA targets. A glass surface with arrays of immobilized oligonucleotide capture sequences is used to capture DNA targets, which are then detected via hybridization to the gold nanoparticle probes. Amplification with silver allows for detection and quantitation by measuring evanescent wave induced light scatter with low-cost optical detection systems. Compared to Cy3-based fluorescence, silver amplified gold nanoparticle probes provide for a approximately 1000-fold increase in sensitivity. Furthermore, direct detection of non-amplified genomic DNA from infectious agents is afforded through increased specificity and even identification of single nucleotide polymorphisms (SNP) in human genomic DNA appears feasible.

Disc degeneration assessed by quantitative T2* (T2 star) correlated with functional lumbar mechanics.

STUDY DESIGN: Experimental correlation study design to quantify features of disc health, including signal intensity and distinction between the annulus fibrosus and nucleus pulposus, with T2* magnetic resonance imaging (MRI) and correlate with the functional mechanics in corresponding motion segments. OBJECTIVE: Establish the relationship between disc health assessed by quantitative T2* MRI and functional lumbar mechanics. SUMMARY OF BACKGROUND DATA: Degeneration leads to altered biochemistry in the disc, affecting the mechanical competence. Clinical routine MRI sequences are not adequate in detecting early changes in degeneration and fails to correlate with pain or improve patient stratification. Quantitative T2* relaxation time mapping probes biochemical features and may offer more sensitivity in assessing disc degeneration. METHODS: Cadaveric lumbar spines were imaged using quantitative T2* mapping, as well as conventional T2-weighted MRI sequences. Discs were graded by the Pfirrmann scale, and features of disc health, including signal intensity (T2* intensity area) and distinction between the annulus fibrosus and nucleus pulposus (transition zone slope), were quantified by T2*. Each motion segment was subjected to pure moment bending to determine range of motion (ROM), neutral zone (NZ), and bending stiffness. RESULTS: T2* intensity area and transition zone slope were significantly correlated with flexion ROM (P = 0.015; P = 0.002), ratio of NZ/ROM (P = 0.010; P = 0.028), and stiffness (P = 0.044; P = 0.026), as well as lateral bending NZ/ROM (P = 0.005; P = 0.010) and stiffness (P = 0.022; P = 0.029). T2* intensity area was also correlated with lateral bending ROM (P = 0.023). Pfirrmann grade was only correlated with lateral bending NZ/ROM (P = 0.001) and stiffness (P = 0.007). CONCLUSION: T2* mapping is a sensitive quantitative method capable of detecting changes associated with disc degeneration. Features of disc health quantified with T2* predicted altered functional mechanics of the lumbar spine better than traditional Pfirrmann grading. This new methodology and analysis technique may enhance the assessment of degeneration and enable greater patient stratification for therapeutic strategies. LEVEL OF EVIDENCE: N/A.

Synchronous hepatocellular carcinoma with renal cell carcinoma: a case report and review of literature of multiple synchronous primary malignancies.

Multiple synchronous primary malignancies have been reported since the 19th century. A number of proposed theories as to the predisposing factors have been discussed. The criteria to diagnose multiple primary malignancies have been revised by Warren and Gates. We hereby present a case of an asymptomatic individual detected with a synchronous hepatocellular carcinoma and a renal cell carcinoma, its presentation, diagnosis, and the management. The occurrence of synchronous hepatocellular carcinoma with renal cell carcinoma is very rare and only a few cases have been reported. Synchronous extrahepatic primary malignancies have been reported in a few studies across the world though with a varied incidence rate. The occurrence seems to be in the older age group without gender differentiation. The extrahepatic malignancies were more common in cirrhotic livers though the overall survival does not differ between patients with hepatocellular carcinoma alone and hepatocellular carcinoma with synchronous extrahepatic malignancies.

The biomechanics of a multilevel lumbar spine hybrid using nucleus replacement in conjunction with fusion.

BACKGROUND CONTEXT: Degenerative disc disease is commonly a multilevel pathology with varying deterioration severity. The use of fusion on multiple levels can significantly affect functionality and has been linked to persistent adjacent disc degeneration. A hybrid approach of fusion and nucleus replacement (NR) has been suggested as a solution for mildly degenerated yet painful levels adjacent to fusion. PURPOSE: To compare the biomechanical metrics of different hybrid implant constructs, hypothesizing that an NR+fusion hybrid would be similar to a single-level fusion and perform more naturally compared with a two-level fusion. STUDY DESIGN: A cadaveric in vitro repeated-measures study was performed to evaluate a multilevel lumbar NR+fusion hybrid. METHODS: Eight cadaveric spines (L3-S1) were tested in a Spine Kinetic Simulator (Instron, Norwood, MA, USA). Pure moments of 8 Nm were applied in flexion/extension, lateral bending, and axial rotation as well as compression loading. Specimens were tested intact; fused (using transforaminal lumbar interbody fusion instrumentation with posterior rods) at L5-S1; with a nuclectomy at L4-L5 including fusion at L5-S1; with NR at L4-L5 including fusion at L5-S1; and finally with a two-level fusion spanning L4-S1. Repeated-measures analysis of variance and corrected t tests were used to statistically compare outcomes. RESULTS: The NR+fusion hybrid and single-level fusion exhibited no statistical differences for range of motion (ROM), stiffness, neutral zone, and intradiscal pressure in all loading directions. Compared with two-level fusion, the hybrid affords the construct 41.9% more ROM on average. Two-level fusion stiffness was statistically higher than all other constructs and resulted in significantly lower ROM in flexion, extension, and lateral bending. The hybrid construct produced approximately half of the L3-L4 adjacent-level pressures as the two-level fusion case while generating similar pressures to the single-level fusion case. CONCLUSIONS: These data portend more natural functional outcomes and fewer adjacent disc complications for a multilevel NR+fusion hybrid compared with the classical two-level fusion.