Principles of physics in surgery: the laws of mechanics and vectors physics for surgeons-part 2

Managing water dynamics for optimal outcomes in unilateral biportal endoscopic surgery: preliminary results in a new operative channel

BACKGROUND

In recent years, unilateral biportal endoscopic (UBE) surgery has become one of the most popular minimally invasive spine surgeries. Unlike traditional open surgery, UBE surgery is performed in isotonic saline solution. Therefore, comprehending the water dynamics involved in UBE surgery is crucial.

METHODS

This prospective study involved 29 patients with single-level lumbar instability or degenerative disk disease who underwent UBE surgery between April 2021 and March 2022. Water flow pressure was measured using a disposable pressure transducer. Multifidus muscle MRI images were analyzed by ImageJ software at intervertebral disc levels. Perioperative blood loss was estimated by the Gross formula. The obtained data were then analyzed with independent t tests, chi-squared tests, and Pearson's correlation.

RESULTS

Height and weight were risk factors for increased water flow pressure during UBE surgery (r = 0.424, P = 0.022, r = 0.384, P = 0.040). The phenomenon of low water flow pressure led to escalations in perioperative total blood loss, hematocrit loss and hemoglobin loss (r = -0.369, P = 0.049, r = -0.424, P = 0.022, r = -0.405, P = 0.029). An excessive water flow pressure can worsen postoperative multifidus swelling and elevate the patient's leg pain visual analogue scale (VAS) score at 1 week (r = 0.442, P = 0.016, r = 0.394, P = 0.034).

REGISTRATION

Trial registration Chinese Clinical Trial Registry, registration number ChiCTR2300078497, date of registration: 11/12/2023.

CONCLUSION

Both low and high water flow pressures can have deleterious effects. The water flow pressure should be controlled within a reasonable range during UBE surgery.

A Retrospective, Observational and Descriptive Study of 111 Ventral Hernia Repairs: Is the Open Approach Already over the Hill?

Objectives: Incisional ventral hernia repair remains a challenging surgery for abdominal wall surgeons. We report the results at 48 months post-surgery regarding open ventral hernia repair (OVHR), analyzing the recurrence rate and incidence of chronic pain. Methods: This was a retrospective, observational study of 111 consecutive patients who underwent OVHR. Between January 2017 and December 2019, patient data were collected from a database and classified by hernia type. Through questionnaires and clinical examinations, the recurrence rate and incidence of chronic pain (measured using the VAS score and a Likert scale) were obtained. Results: In all patients, the hernia repair was performed via an open approach. Long-term follow-up (48 months after surgery) revealed that 20% of patients experienced mild chronic pain alongside the flanks, and the recurrence rate was 5%. Moreover, long-term follow-up revealed the following secondary outcomes: movement limitations in sports were reported in 7% of patients, and movement limitations during long walking were reported in 11% of patients. Conclusions: Our technique for OVHR is a safe procedure with a low rate of recurrence and chronic pain. Our future aim is to organize a prospective study.

The abdominal compliance index and postoperative pain after laparoscopic gynecologic surgery: a preliminary observational cohort study

Background/aim

In gynecology, laparoscopic surgery has the advantages of reduced scarring, less postoperative pain, faster recovery, and lower risk of complications. Despite these advantages, shoulder pain still remains a major concern, affecting up to 90% of patients undergoing gynecologic laparoscopic surgery. Use of the abdominal compliance index (ACI) may offer the benefit of increased space for safer surgery and may prevent the drawback of high insufflation pressures. The aim of this study was to investigate the relationship between shoulder pain, abdominal pain, and analgesic use with the recently advised ACI, a surrogate index of abdominal expansion in patients undergoing gynecologic laparoscopic surgery.

Materials and methods

Thirty-one patients with American Society of Anesthesiologists scores of 1-3 who underwent elective gynecologic laparoscopic surgery were included. The insufflation pressure was set to 12 mmHg. ACI, defined as insufflated intraabdominal volume (L) per body surface area (m2), was used to estimate the relationship between abdominal compliance and postoperative pain.

Results

The 31 patients were separated into two groups based on median ACI level (range 1.37-2.73 L/m2), with those having values of 2.16 L/m2 or lower as group 1 and those with higher values as group 2. Abdominal visual analogue scale (VAS) scores at 30 min postoperative were significantly higher in group 2 than in group 1 (p < 0.001). Shoulder pain VAS scores at 24 h and 36 h postoperative were also significantly higher in group 2 than in group 1 (p = 0.021 and p = 0.002, respectively). The total amount of analgesic infusion and additional analgesic requirements were lower in group 1 than in group 2 (p = 0.049 and p = 0.001, respectively). ACI did not differ with patient demographic characteristics or history of abdominal/laparoscopic surgery, parity, abdominal drainage, and pneumoperitoneum time.

Conclusion

ACI, a surrogate index of abdominal expansion capacity, may be used to guide individualization of insufflation pressures by identifying female patients under risk of higher postoperative pain.

Risk factors for postoperative morbidity after ventral hernia repair in patients with liver cirrhosis. A single tertiary center cohort

<b>Introduction:</b> Ventral hernias are common among patients with liver cirrhosis.<b>Aim:</b> The aim of our work was to evaluate potential risk factors for major postoperative morbidity after ventral hernia repair in cirrhotic patients.<b>Material and methods:</b> A retrospective cohort study was performed in 45 consecutive cirrhotic patients that underwent ventral hernia repair between 2005 and 2022. Major morbidity was defined as Clavien-Dindo ≥ IIIa at 30 days postoperatively. Uni- and multivariate analysis was performed to identify risk factors for major postoperative complications.<b>Results:</b> In our cohort, we observed an overall postoperative 30-day morbidity rate of 53.33% (n = 24), with 40% (n = 18) of cases classified as Clavien-Dindo IIIa or above. Elevated serum creatinine level preoperatively was identified as a statistically significant risk factor, both in the uni- as well as the multivariate analysis for major morbidity (OR = 31.08; 95%CI [29.51-32.65]; P = 0.028).<b>Conclusions:</b> Increased creatinine levels were found to be a significant modifiable factor for major morbidity after ventral hernia repair in cases with cirrhosis. This finding underlines the impact of preoperative medical management of cirrhotic patients on postoperative outcome in this patient population.

The Rochester Model for Spinal CSF Leak Repair Simulation and Scoring

BACKGROUND AND OBJECTIVE

Iatrogenic spinal durotomies occur at a rate of 1% to 17%. Surgical simulation for durotomy repair is needed to provide affordable, accessible, and validated practice. This study sought to design and validate a simple 3-dimensional printed model for spinal cerebrospinal fluid (CSF) leak repair and to introduce the Rochester original objective structured assessment of technical skills (OSATS) CSF leak (ROCL) repair criteria for assessment.

METHODS

A spinal model was designed to mimic a lumbar laminectomy with the L3-5 lamina removed and 3-dimensional printed using Vero polymers. The model was paired with a porcine collagen "dura" that was pressurized using IV saline and overlayed with gel-molded fascial, muscle, and skin layers with an opening. Participants were provided a training model with a 1.5-cm midline durotomy, surgical microinstrument set, microscope, and 6-0 prolene suture. The 25-point ROCL repair criteria were adapted from the original OSATS principles to assess proficiency in surgical repair by 2 blinded neurosurgeons not participating in the trials. Postsimulation survey data regarding model realism were collected.

RESULTS

Six residents and 4 attendings participated. Median operative time in minutes was 13 minutes among residents and 7 minutes among attendings. Moreover, the ROCL score was a median of 19/25 for attendings and 15/25 for residents. The suture angle was statistically more consistent among senior residents and attendings compared with junior residents. Participants agreed that the model was realistic (median 4/5), useful for improving the operative technique (median 5/5), and would increase comfort in spinal CSF leak repair procedures (median 5/5). Each reusable model had a cost of $19.99 if printed with polylactic acid and each replacement dura cost <3¢.

CONCLUSION

This study presents an affordable, realistic, and educational spinal CSF leak repair model and introduces ROCL for assessment.

The Evolving Landscape of Male Varicocele Pathophysiology in the Era of Multi-Omics: A Narrative Review of the Current Literature

Male-factor infertility is implicated in over half of the millions of cases of infertility worldwide, and varicoceles are the most common correctable cause of male-factor infertility. The pathophysiologic mechanism for varicoceles is complex and next-generation technologies offer promising insights into the molecular underpinnings of this condition. In this narrative review, we highlight historical and contemporary paradigms associated with varicoceles, with an emphasis on the biological underpinnings of this disease. Specifically, we review the literature describing the underlying causes of varicoceles, discuss the molecular and cellular mechanisms causing pathological changes in some (but not all) men, and highlight key articles regarding the next-generation analyses (e.g., transcriptome, epigenome, proteome, and microbiome) being applied to better understand the condition and its treatment. These data demonstrate an ongoing evolution of the knowledge of varicoceles and the potential for improved personalized care in the future for men with this condition.

Umbilical Hernia Repair in Patients with Cirrhosis and in Patients with Severe Comorbidities-A Nationwide Cohort Study

INTRODUCTION

Umbilical hernia is a frequent condition in patients with cirrhosis. The aim of the study was to evaluate the risks associated with umbilical hernia repair in patients with cirrhosis in the elective and emergency setting. Secondly, to compare patients with cirrhosis with a population of patients with equally severe comorbidities but without cirrhosis.

METHODS

Patients with cirrhosis who underwent umbilical hernia repair from January 1, 2007, to December 31, 2018, were included from the Danish Hernia Database. A control group of patients with a similar Charlson score (≥ 3) without cirrhosis was generated using propensity score matching. The primary outcome was postoperative re-intervention within 30 days following hernia repair. Secondary outcomes were mortality within 90 days and readmission within 30 days following hernia repair.

RESULTS

A total of 252 patients with cirrhosis and 504 controls were included. Emergency repair in patients with cirrhosis was associated with a significantly increased rate of re-intervention (54/108 (50%) vs. 24/144 (16.7%), P < 0.001), 30-day readmission rate (50/108 (46.3%) compared with elective repair vs. 36/144 (25%) (P < 0.0001)), and 90-day mortality (18/108 (16.7%) vs. 5/144 (3.5%), P < 0.001). Patients with cirrhosis were more likely to undergo a postoperative re-intervention compared with comorbid patients without cirrhosis (OR = 2.10; 95% CI [1.45-3.03]).

CONCLUSION

Patients with cirrhosis and other severe comorbidity undergo emergency umbilical hernia repair frequently. Emergency repair is associated with increased risk of poor outcome. Patients with cirrhosis undergo a postoperative reintervention more frequently than patients with other severe comorbidity undergoing umbilical hernia repair.

eTEP-RS for incisional hernias in a non-robotic center. Is laparoscopy enough to perform a durable MIS repair of the abdominal wall defect?

INTRODUCTION

Incisional hernias can complicate up to 25% of laparotomies, and successful repair remains a significant clinical challenge for surgeons. Recently, the surgical technique of ventral hernia repair (eTEP-RS) has been introduced. The method was presented relatively recently and continues to evolve. The use of a robotic platform in eTEP-RS resulted in a significant improvement in ergonomics. Therefore, the questions arise as to whether the laparoscopic technique might still be feasible for such long procedures. The objective of this study is to present our early results in the treatment of patients with incisional ventral hernias using eTEP-RS and to discuss key technical aspects.

PATIENTS AND METHODS

A prospective case-controlled study was conducted for all incisional ventral hernia patients (hernia orifice between 4 and 10 cm) who underwent eTEP-RS between March 2019 and December 2021. Demographic data were recorded; and perioperative and postoperative results were analyzed.

RESULTS

We performed 34 eTEP-RS procedures. The mean duration of the surgery was 211 min (145-295). The mean width of the defect was 6.8 cm and the defect area was 42.5 cm². The mean mesh size was 498 cm² (270-625). After an average follow-up of 16 months (2-30), there was no recurrence or major complication.

CONCLUSIONS

The eTEP-RS is a safe alternative to open ventral hernia repair in selected cases and allows for the placement of a large piece of mesh in accordance with current recommendations, even in non-robotic centers. Excellent knowledge of the detailed anatomy of the abdominal wall is essential for safe and effective hernia repair. Compliance with certain rules of the laparoscopic eTEP-RS facilitates improved ergonomics for this procedure even in non-robotic centers.

Cardioprotective effect of silicon-built restraint device (ASD), for left ventricular remodeling in rat heart failure model

This study aims to evaluate the feasibility and cardio-protective effects of biocompatible silicon-built restraint device (ASD) in the rat's heart failure (HF) model. The performance and compliance characteristics of the ASD device were assessed in vitro by adopting a pneumatic drive and ball burst test. Sprague-Dawley (SD) rats were divided into four groups (n = 6); control, HF, HF + CSD, and HF + ASD groups, respectively. Heart failure was developed by left anterior descending (LAD) coronary artery ligation in all groups except the control group. The ASD and CSD devices were implanted in the heart of HF + ASD and HF + CSD groups, respectively. The ASD's functional and expansion ability was found to be safe and suitable for attenuating ventricular remodeling. ASD-treated rats showed normal heart rhythm, demonstrated by smooth -ST and asymmetrical T-wave. At the same time, hemodynamic parameters of the HF + ASD group improved systolic and diastolic functions, reducing ventricular wall stress, which indicated reverse remodeling. The BNP values were reduced in the HF + ASD group, which confirmed ASD feasibility and reversed remodeling at a molecular level. Furthermore, the HF + ASD group with no fibrosis suggests that ASD has significant curative effects on the heart muscles. In conclusion, ASD was found to be a promising restraint therapy than the previously standard restraint therapies. Stepwise ASD fabrication process (a) 3D computer model of ASD was generated by using Rhinoceros 5.0 software (b) 3D blue wax model of ASD (c) Silicon was prepared by mixing the solutions (as per manufacturer instruction) (d) Blue wax model of ASD was immersed into liquid Silicon (e) ASD model was put into the oven for 3 hours at 50 °C. (f) Blue wax started melting from the ASD model (g) ASD model was built from pure silicon (h) Two access lines were linked to the ASD device, which was connected with an implantable catheter (Port-a-cath), scale bar 100 µm. (Nikon Ldx 2.0).

Umbilical hernia repair in patients with cirrhosis: systematic review of mortality and complications

BACKGROUND

Umbilical hernia is a common and potential serious condition in patients with cirrhosis. This systematic review evaluated the risks associated with emergency and elective hernia repair in patients with cirrhosis.

METHODS

Systematic review of clinical trials identified through manual and electronic searches in several databases (last update November 2021). The primary random-effects meta-analyses evaluated mortality in patients with or without cirrhosis or following emergency versus elective repair. The quality of the evidence was assessed using GRADE and Newcastle Ottawa Scale.

RESULTS

Thirteen prospective and 10 retrospective studies including a total of 3229 patients were included. The evidence was graded as very low quality for all outcomes (mortality and postoperative complications within 90 days). In total 191 patients (6%) died after undergoing umbilical hernia repair. Patients with cirrhosis were more than eight times as likely to die after surgery compared with patients without cirrhosis [OR = 8.50, 95% CI (1.91-37.86)] corresponding to 69 more deaths/1000 patients. Among patients with cirrhosis, mortality was higher after emergency versus elective repair [OR = 2.67, 95% CI (1.87-3.97)] corresponding to 52 more deaths/1000 patients. Postoperative complications were more common in patients with cirrhosis compared with patients without cirrhosis.

CONCLUSION

Patients with cirrhosis undergoing emergency umbilical hernia repair have a considerably increased risk of death and severe complications. Accordingly, additional evidence is needed to evaluate methods that would allow elective umbilical hernia repair in patients with cirrhosis.

Novel suturing technique, based on physical principles, achieves a breaking point double that obtained by conventional techniques

BACKGROUND

Sutures have been used to repair wounds since ancient times. However, the basic suture technique has not significantly changed. In Phase I of our project, we proposed a “double diabolo” suture design, using a theoretical physical study to show that this suture receives 50% less tension than conventional sutures, and so a correspondingly greater force must be applied to break it.

AIM

To determine whether these theoretical levels of resistance were met by the new type of suture.

METHODS

An observational study was performed to compare three types of sutures, using a device that exerted force on the suture until the breaking point was reached. The tension produced by this traction was measured. The following variables were considered: Tearing stress on entry/exit points, edge separation stress, and suture break stress. The study sample consisted of 30 sutures with simple interrupted stitches (Group 1), 30 with continuous stitches (Group 2), and 30 with the “double diabolo” design (Group 3).

RESULTS

The mean degree of force required to reach the breaking point for each of these variables (tearing, separation, and final breaking) was highest in Group 3 (14.56, 18.28, and 21.39 kg), followed by Group 1 (7.36, 10.38, and 12.81 kg) and Group 2 (5.77, 7.7, and 8.71 kg). These differences were statistically significant (P < 0.001) in all cases.

CONCLUSION

The experimental results show that with the “double diabolo” suture, compared with conventional sutures, greater force must be applied to reach the breaking point (almost twice as much as in the simple interrupted suture and more than double that required for the continuous suture). If these results are confirmed in Phase III (the clinical phase) of our study, we believe the double diabolo technique should be adopted as the standard approach, especially when the suture must withstand significant tension (e.g., laparotomy closure, thoracotomy closure, diaphragm suture, or hernial orifice closure).

Effect of 3D printed polycaprolactone scaffold with a bionic structure on the early stage of fat grafting

Mature adipocytes are sensitive to stress and hypoxia, which are the two major obstacles in large-volume fat grafting. Bionic scaffolds are considered beneficial for fat grafting; however, their mechanism is still unclear. In this study, polycaprolactone scaffolds were fabricated by a 3D-printing technique and compounded with liposuction fat. They were implanted subcutaneously into nude mice. At different times, gross and histological observations were performed to evaluate the retention rates and histological morphologies. Adipocyte viability, apoptosis, and vascularization were analyzed by special immunostaining. Quantitative polymerase chain reaction was used to detect the variations in hypoxia and inflammation. The results showed that the volume and weight retentions in the scaffold group were higher than those in the fat group with the former exhibiting fewer vacuoles and less fibrosis. In immunostaining, elevated CD31+ capillaries, more perilipin+ adipocytes, and fewer TUNEL+ apoptotic cells were observed in the scaffold group by week 4. The lower expression of HIF-1α indicated the alleviation of hypoxia. In conclusion, the scaffold provided mechanical support to resist skin tension, thereby decreasing the interstitial pressure, and improving substance exchange and vascular ingrowth. In this regard, the scaffold attenuated hypoxia and promoted vascularization, making it a feasible method to increase long-term retention in fat grafting using scaffolds with suitable degradation rates and additional vascular maturation stimulation.

Water Dynamics in Unilateral Biportal Endoscopic Spine Surgery and Its Related Factors: An In Vivo Proportional Regression and Proficiency-Matched Study

BACKGROUND

Stable water dynamics during endoscopic spine surgery improves the surgeon's comfort and patient's outcomes. We aimed to measure the water dynamics during spinal surgery and identify the factors that facilitate stable water dynamics.

METHODS

This open-label, prospective, proficiency-matched, in vivo study included patients with single-level degenerative spinal disease. After assessing their heights and balancing the matched instrument, we measured the irrigation fluid pressure in various situations. We performed multiple regression analysis based on odds ratio (OR), confidence interval (CI), and relationships (proficiency-matched) with possible instrumental and physical characteristics. The instrumental factors were the presence and length of a rigid cannulation, and the physical characteristics were body mass index (body mass index [BMI]), skin-to-dura depth, height (interaction with BMI), and body weight (interaction with BMI).

RESULTS

Of the 36 patients, 29 were included. The mean pressure of the operation cavity was 16.66 ± 9.12 cm H₂O (12.25 ± 6.71 mm Hg). Water pressure with the rigid cannulation (9.41 ± 2.94 cm H₂O [6.92 ± 2.16 mm Hg]) was significantly lower than that without cannulation (23.43 ± 7.57 cm H₂O [17.26 ± 5.57 mm Hg], P < 0.01). Water pressure correlated with cannular length (OR = -1.08, CI = -1.79, -0.37, P < 0.01) and BMI (OR = 0.56, CI = 0.12, 0.99, P < 0.01). BMI showed a proportional relationship (r = 0.84, P < 0.01).

CONCLUSIONS

During biportal endoscopy, we suggest maintaining water pressure between 4.41 cm H₂O (2.41 mm Hg) and 31.00 cm H₂O (22.83 mm Hg). Compared to physical characteristics, placement of the cannula and appropriate cannula length are important factors that affect water dynamics.

Ogilvie syndrome: peculiar manifestation of acquired immunodeficiency syndrome in non-institutionalized middle age female in Tanzania

Since it was first documented in 1948 by Sir William Heneage Ogilvie, numerous cases of Ogilvie syndrome have been described in literature due to various medical and surgical causes. Nonetheless, only a handful of cases only have been documented due to underlying Acquired Immunodeficiency Syndrome (AIDS). A 41-year-old female was admitted with an acute abdomen secondary to partial mechanical intestinal obstruction or paralytic ileus based on signs and symptoms and Abdominal X-Ray (AXR). She was known to be HIV/AIDS WHO clinical stage II on treatment. On diagnostic imaging studies she had distended large bowels without features of mechanical intestinal obstruction and the diagnosis of Ogilvie syndrome was suspected after other differentials were excluded. Early recognition and appropriate management are essential, because if left untreated the bowel distension may progress to caecal perforation and fatal peritonitis. Medical imaging with Computer Tomography (CT) scan and colonoscopy has helped in achieving an accurate diagnosis and avoiding unnecessary laparotomies. Although an uncommon disorder, for earlier and accurate diagnosis a high index of suspicion is required by clinicians and radiologists who are treating patients with underlying HIV/AIDS. Ogilvie's syndrome is a rare condition and if missed can be fatal. In patients with HIV/AIDS, the symptoms may be directly due to HIV infection, secondary to opportunistic infections or possible neurotoxic effects of HIV treatment or lack of vitamin and minerals. It is important to exclude Ogilvie syndrome in patients from surgical causes of the acute abdomen to avoid unnecessary surgical procedures.

Compression therapy in venous diseases: physical assumptions and clinical effects

Compression therapy (CT) is an established treatment method in chronic venous disease. Despite years of clinical experience, choosing the optimum compression therapy, including grade and pressure distribution, which determine the efficacy of treatment poses a challenge. The paper discusses CT physical assumptions (stiffness, elasticity, static and dynamic stiffness indices), clinical effects and contraindications to CT.

Extended View: Totally Extra Peritoneal (e-TEP) Approach for Ventral and Incisional Hernia-Early results from a single center

BACKGROUND

Laparoscopy for ventral hernia repair is now an established technique with its proven benefits of less pain, early recovery, low-recurrence rate as compared to open repair. Several techniques have been described such as IPOM, MILOS, TES, EMILOS, SCOLA, e-TEP. e-TEP was originally conceptualized as an alternative approach to inguinal hernia in difficult cases (obese, previous scars) and for training surgery residents. Application of this approach for ventral hernia repair has recently been reported by few surgeons. We present our experience of e-TEP approach for ventral hernia from a tertiary care center in South India over one year duration.

MATERIALS AND METHODS

Electronically maintained data of patients who underwent e-TEP for ventral hernia during a period of November 2017 to November 2018 was reviewed retrospectively. Their demographic data, intraoperative details, postoperative complications and follow up data for a period of 6 months was noted.

RESULTS

171 patients underwent e-TEP approach ventral hernia repair. Mean age was 49.34 ± 10.75 years with hypertension being most common comorbidity. Mean BMI was 29.2 ± 4.1 kg/m². Mean defect area was 51.35 ± 45.09 cm² and mean mesh size used was 397.56 ± 208.83 cm². Fifty patients required TAR. Mean duration of surgery was 176.75 ± 62.42 min and blood loss was 78.7 ± 24.4 ml. Mean length of stay was 2.18 ± 1.27 days. Seven cases had paralytic ileus, 5 cases had surgical site infection, and 3 cases had recurrence at 6 months follow up.

CONCLUSION

e-TEP is a minimally invasive approach which is safe, feasible and also avoids placement of mesh in peritoneal cavity. Since it is a relatively new approach it requires further studies for standardization of techniques, criteria for patient selection and to study long-term outcomes.

Abdominal Compliance and Laparoscopy: A Review

Background and Objectives

Creating and maintaining a pneumoperitoneum to perform laparoscopy is governed by gas laws and the limiting physical constraints of the abdomen.

Methods

A review of how gas, biomechanical and physical properties affect the abdomen and a systematic structured Medline and PubMed search was conducted to identify relevant studies related to the topic.

Results

Abdominal compliance is a measure of ease of abdominal expansion and is determined by the elasticity of the abdominal wall and diaphragm. It is the change in intra-abdominal volume per change in intra-abdominal pressure. Caution should be exercised with pressures exceeding 12 millimeters mercury since this is defined as intra-abdominal hypertension.

Conclusions

Abdominal compliance has its limits, is unique for each patient and pressure-volume curves cannot be easily predicted. Using the lowest possible pressure to accomplish the surgical task without compromising surgical outcome is the desired goal. The clinical importance is caution and knowing there is a point where more pressure does not increase working space and only increases pressure.

Sinsky hook assisted roll preparation (SHARP): A modified technique for Descemet membrane endothelial keratoplasty donor preparation

Purpose

To describe a simple technique of sinsky hook assisted roll preparation (SHARP) for Descemet membrane endothelial keratoplasty (DMEK) donor preparation.

Methods

This experimental study was conducted at National Eye Bank, India with 40 optical grade human donor corneoscleral tissues found not suitable for surgery. 25 tissues were initially used to standardize the technique and remaining 15 for establishing the final technique. Donor corneal tissues were initially placed on a sterile Teflon block partially filled with tissue culture media. Initially, a partial thickness trephination was done followed by sinsky assisted 360° separation of the Descemet membrane (DM) from the underlying stroma (2 mm from the edge). The separation was further extended by 3–4 mm from the edge for 4–5 clock hours followed by bimanual peeling of the DM. This was followed by central 8 mm trephination. The primary outcome measures were a complete success (8 mm roll without peripheral edge tears) and partial success (8 mm roll with peripheral edge tears).

Results

DMEK roll was successfully peeled in 86.6% tissues (n = 13/15). Complete success was obtained in 66.6% tissues while partial success was obtained in 20% tissues. The median age of donor tissue was 45 years. The donor age of tissues, from which DMEK roll could not be obtained (2/12) was 15 days and 18 years.

Conclusion

SHARP is a simple technique of DMEK that does not require any sophisticated instruments.

Physics for Surgeons Part 3: Why Cyst Is Spherical in Shape?

Physical examination of any swelling is the first step in making a diagnosis. Many a times we see a patient with a spherical swelling, which is usually a cyst. The interpretation of physical signs should be based on sound principles of physics. In the present paper, we explain physical characteristics of a swelling (cyst) using principles of fluid mechanics.

Management of colon stents based on Bernoulli's principle

BACKGROUND AND AIMS

The colonic self-expanding metal stent (SEMS) has been widely used for "bridge to surgery" and palliative therapy. However, if the spread of SEMS is insufficient, not only can a decompression effect not be obtained but also perforation and obstructive colitis can occur. The mechanism of occurrence of obstructive colitis and perforation was investigated by flow dynamics.

METHODS

Bernoulli's principle was applied, assuming that the cause of inflammation and perforation represented the pressure difference in the proximal lumen and stent. The variables considered were proximal lumen diameter, stent lumen diameter, flow rate into the proximal lumen, and fluid density. To model the right colon, the proximal lumen diameter was set at 50 mm. To model the left-side colon, the proximal lumen diameter was set at 30 mm.

RESULTS

For both the right colon model and the left-side colon model, the difference in pressure between the proximal lumen and the stent was less than 20 mmHg, when the diameter of the stent lumen was 14 mm or more. Both the right colon model and the left-side colon model were 30 mmHg or more at 200 mL s^-1 when the stent lumen was 10 mm or less. Even with an inflow rate of 90-110 mL s^-1, the pressure was 140 mmHg when the stent lumen diameter was 5 mm.

CONCLUSION

In theory, in order to maintain the effectiveness of SEMS, it is necessary to keep the diameter of the stent lumen at 14 mm or more.

Pre-eclampsia renamed and reframed: Intra-abdominal hypertension in pregnancy

This hypothesis proposes pre-eclampsia is caused by intra-abdominal hypertension in pregnancy. Sustained or increasing intra-abdominal pressure ⩾12mmHg causes impaired venous return to the heart, systemic vascular resistance, ischemia reperfusion injury, intestinal permeability, translocation of lipopolysaccharide endotoxin to the liver, cytotoxic immune response, systemic inflammatory response, pressure transmission to thoracic and intra-cranial compartments, and multi-organ dysfunction. This hypothesis is predicated on Pascal's law, evidence founded in the intra-abdominal hypertension literature, and the adapted equation ΔIAP-P=ΔIAVF/Cab, where ΔIAP-P=change in intra-abdominal pressure in pregnancy, ΔIAVF=change in intra-abdominal vector force (volume and force direction) and Cab=abdominal compliance. Factors causing increased intra-abdominal pressure in pregnancy include: progressive uterine expansion, obstetrical factors that increase intra-uterine volume excessively or acutely, maternal anthropometric measurements that affect intra-abdominal pressure thresholds, maternal postures that increase abdominal force direction, abdominal compliance that is decreased, diminished with advancing gestation, or has reached maximum expansion, habitation at high altitude, and rapid drops in barometric pressure. We postulate that the threshold for lipopolysaccharide translocation depends on the magnitude of intra-abdominal pressure, the intestinal microbiome complex, and the degree of intestinal permeability. We advance that delivery cures pre-eclampsia through the mechanism of abdominal decompression.

Prostate swelling and shift during high intensity focused ultrasound: implication for targeted focal therapy

PURPOSE

We quantified prostate swelling and the intraprostatic point shift during high intensity focused ultrasound using real-time ultrasound.

MATERIALS AND METHODS

The institutional review board approved this retrospective study. Whole gland high intensity focused ultrasound was done in 44 patients with clinically localized prostate cancer. Three high intensity focused ultrasound sessions were required to cover the entire prostate, including the anterior zone (session 1), middle zone (session 2) and posterior zone (session 3). Computer assisted 3-dimensional reconstructions based on 3 mm step-section images of intraoperative transrectal ultrasound were compared before and after each session.

RESULTS

Most prostate swelling and intraprostatic point shifts occurred during session 1. The median percent volume increase was 18% for the transition zone, 9% for the peripheral zone and 13% for the entire prostate. The volume percent increase in the transition zone (p <0.001), peripheral zone (p = 0.001) and entire prostate (p = 0.001) statistically depended on the volume of each area measured preoperatively. The median 3-dimensional intraprostatic shift was 3.7 mm (range 0.9 to 13) in the transition zone and 5.5 mm (range 0.2 to 14) in the peripheral zone. A significant negative linear correlation was found between the preoperative presumed circle area ratio, and the percent increase in prostate volume (p = 0.001) and shift (p = 0.01) during high intensity focused ultrasound.

CONCLUSIONS

We quantified significant prostate swelling and shift during high intensity focused ultrasound. Smaller prostates and a smaller preoperative presumed circle area ratio were associated with greater prostate swelling and intraprostatic shifts. Real-time intraoperative adjustment of the treatment plan impacts the achievement of precise targeting during high intensity focused ultrasound, especially in prostates with a smaller volume and/or a smaller preoperative presumed circle area ratio.