Ahmed M. Zihni

Pore size and pore shape – but not mesh density – alter the mechanical strength of tissue ingrowth and host tissue response to synthetic mesh materials in a porcine model of ventral hernia repair

BACKGROUND Over 100 types of soft tissue repair materials are commercially available for hernia repair applications. These materials vary in characteristics such as mesh density, pore size, and pore shape. It is difficult to determine the impact of a single variable of interest due to other compounding variables in a particular design. Thus, the current study utilized prototype meshes designed to evaluate each of these mesh parameters individually. METHODS Five prototype meshes composed of planar, monofilament polyethylene terephthalate (PET) were evaluated in this study. The meshes were designed to focus on three key parameters, namely mesh density, pore size, and pore shape. The prototype meshes were implanted in the preperitoneal, retrorectus space in a porcine model of ventral incisional hernia repair, and tissue ingrowth characteristics were evaluated after 90 days. Mesh-tissue composite specimens were obtained from each repair site and evaluated via T-peel mechanical testing. Force-displacement data for each T-peel test were analyzed and five characteristics of tissue ingrowth reported: peak force (fp), critical force (fc), fracture energy (Γc), work (W), and work density (Wden). Hematoxylin and eosin (H&E) stained sections of explanted mesh-tissue composites were also assessed for characteristics of tissue response including cellular infiltration, cell types, inflammatory response, extracellular matrix deposition, neovascularization, and fibrosis, with a composite score assigned to represent overall tissue response. RESULTS The medium-weight, very large pore, hexagonal (MWVLH) mesh performed significantly better than the light-weight, medium pore, diamond (LWMD) mesh for all parameters evaluated (fp, fc, Γc, W, Wden) and trended toward better results than the medium-weight, medium pore, diamond (MWMD) mesh for the majority of the parameters evaluated. When the data for the five meshes was grouped to evaluate mesh density, pore size, and pore shape, differences were more pronounced. No significant differences were observed with respect to mesh density, however significant improvement in mechanical strength of tissue ingrowth occurred as pore size increased from medium to very large. In addition, the hexagonal pores resulted in the strongest tissue ingrowth, followed by the square pores, and finally the diamond pores. Scores for several histological parameters were significantly different for these prototype meshes. For example, the MWVLH mesh showed significantly greater tissue ingrowth by neovascularization histological score than MWMD and MWVLS meshes (p<0.05) and significantly less fibrosis than LWMD and MWVLS meshes (p<0.05). CONCLUSION Pore shape and pore size significantly altered the mechanical strength of tissue ingrowth and host-site integration in a porcine model of ventral hernia repair, while mesh density had no effect.

Analysis of surgical motions in minimally invasive surgery using complexity theory

Traditional Minimally Invasive Surgery (MIS) training paradigm in which interns and junior residents perform operations under the supervision of faculty surgeons lacks objective means of assessing surgical skills. This paper studies novel real–time measures that can dynamically quantify surgical motions. In this study, the proposed measures were tested through two phases of experimental study. In the first phase, ten volunteered subjects who have no prior experience of MIS completed three trials of a surgical exercise using a laparoscopic instrument on which a motion sensor was attached. In the second phase, an MIS surgeon performed three standard surgical exercises with five replications. Then, time–delay and Hurst exponent analysis were used to measure the degree of synchronisation in surgical motions. As the results, improvement in surgical motions was observed such that the range and thickness of time–delay plots are reduced while Hurst exponents increase, as the subjects gain experience.

Advanced Endoluminal Technologies for Barrett's Esophagus

Barretts esophagus (BE) may progress to dysplasia and adenocarcinoma. The value of Barretts surveillance with random biopsies is being questioned, but new technologies may enhance detection of progression within BE and guide endoscopic resection and ablation techniques. This review will focus on optical coherence tomography and endomicroscopy for patients with BE.

Long-term outcomes following POEM for non-achalasia motility disorders of the esophagus

BackgroundOptimal treatment for symptomatic patients with non-achalasia motility disorders (NAD) such as diffuse esophageal spasm, esophagogastric junction outlet obstruction, and hypercontractile disorder is not well established. POEM has been offered to these patients since it is a less invasive and less morbid procedure but long-term outcomes remain undetermined. The aim of this study was to assess long-term outcomes of POEM for patients with NAD.MethodsRecords of 40 consecutive patients undergoing POEM for NAD from May 2011 to January 2016 at a single center were retrospectively reviewed. Preoperative and 6-month postoperative symptom scores, high-resolution manometry, pH testing, and timed barium swallow (TBS) data were collected. Patients were contacted by phone to obtain long-term symptom assessment. Symptoms were assessed using a standardized symptom questionnaire with scores for symptoms graded according to frequency and the Eckardt score.ResultsTen percent had minor complications with no postoperative sequelae. 90% of patients had significant improvement in their mean Eckardt scores (5.02 vs. 1.12, p < 0.001) at early follow-up. Improvements in chest pain (1.02–0.36, p = 0.001) and dysphagia (2.20 vs. 0.40, p = 0.001) were seen. Significant improvements in manometric pressures and esophageal emptying on TBS were observed across groups. 38% (10/26) of patients had a postoperative pH score > 14.72. Long-term (median 48 months) symptom scores were obtained from 29 (72.5%) patients. 82% of patients (24/29) had sustained symptom improvement. A small increase in the dysphagia scores was reported in the long-term follow-up compared to the immediate postoperative period (0.36–0.89, p = 0.046).ConclusionsChest pain and dysphagia are effectively palliated with POEM in patients with non-achalasia disorders of the esophagus. Significant improvements are durable in long-term follow-up. Despite earlier reports by our group suggesting possible inferior outcomes from POEM for this difficult group of patients, this study is far more encouraging. POEM should be considered in the treatment of patients with non-achalasia disorders of the esophagus.

Surgical Management for Gastroparesis

Gastroparesis is a debilitating chronic condition of indeterminate cause. Although conservative management is the mainstay of treatment, a significant percentage of patients will need interventions. Interventions range from supportive measures, such as feeding tubes, to more radical surgeries, including endoscopic pyloromyotomy (per oral pyloromyotomy), laparoscopic pyloroplasty, laparoscopic gastric stimulator placement, and even subtotal or total gastrectomy. The authors present some current treatment algorithms focused on the treatment side of the spectrum along with outcomes data to support the various approaches.

Recurrence quantification analysis for surgical motions in minimally invasive surgery

Minimally invasive surgical technique (MIS) is difficult to master due to its inherent complexity imposed by reduced work volume and limited flexibility in motions. In traditional MIS training, faculty surgeons evaluate junior surgeons performance using subjective and resource-intensive methods lacking quantitative rigour. Although recent technological advancement in surgical education has enabled more objective and automated evaluation of surgical skill, most of measures are still task-specific and thus can be hardly generalised across different operations and platforms. Therefore, this research studies a novel framework for generalised performance measure based on the analysis of non-linear dynamics in surgical motions. Specifically, surgical motions are recorded using motion sensors attached on instruments during surgical exercises. Then, intensity of recurrences in the motion data is calculated and disorder index is computed using the intensity of recurrences. The test results have shown that disorder index values can be used to quantify surgical skill levels.