Publications by authors named "David C Chen"

46 Publications

Sex Differences, Sleep Disturbance and Risk of Persistent Pain Associated With Groin Hernia Surgery: A Nationwide Register-Based Cohort Study.

J Pain 2021 May 5. Epub 2021 May 5.

Department of Clinical Sciences Malmö, Lund University, Malmö, Sweden; Department of Surgery, Skåne University Hospital, Malmö, Sweden.

Persistent pain after groin hernia repair is a major health problem. Sleep disturbance is associated with heightened pain sensitivity. The main objective of this study was to examine the role of sleep disturbance in the development and long-term maintenance of chronic postherniorrhaphy inguinal pain (CPIP), with exploration of sex differences. From 2012-2017, a national cohort of patients with prior groin hernia repair (n=2084;45.8% females) were assessed for the development of CPIP 12 months after surgery. Patients then underwent long-term (median 5.0 years) follow-up to evaluate the contribution of sex and sleep disturbance on the maintenance of CPIP. Associations between pre- and postoperative sleep problems (assessed at long-term follow-up) and CPIP were tested using logistic regression. Females had higher rates of CPIP with negative impact on daily activities 12 months after surgery as compared to males (14.6 vs 9.2%,p<0.0005), and were more likely to have moderate-severe CPIP in the long-term (3.1 vs 1.2%,p=0.003). Preoperative sleep problems predicted development of CPIP 12 months after surgery (adjusted odds ratio (aOR) 1.76 (95%CI 1.26-2.46),p=0.001) and CPIP in the long-term (aOR 2.20 (1.61-3.00),p<0.0001). CPIP was associated with insomnia and depression. Sleep disturbance may increase the risk for CPIP, and contribute to maintenance of postsurgical pain. PERSPECTIVE: Females are at heightened risk for CPIP as compared to males. Increased severity of pain symptoms are linked to poorer sleep and psychiatric morbidity. Given the robust associations between sleep disturbance and CPIP, interventions which consolidate and promote sleep, especially in females, may improve long-term pain control.
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http://dx.doi.org/10.1016/j.jpain.2021.04.008DOI Listing
May 2021

Intra-Operative Vascular Injury and Control During Laparoscopic and Robotic Mesh Explantation for Chronic Post Herniorrhaphy Inguinal Pain (CPIP).

Surg Technol Int 2021 04 20;38. Epub 2021 Apr 20.

Department of Surgery, David Geffen School of Medicine, Lichtenstein Amid Hernia Institute at UCLA Santa Monica, CA, USA.

Introduction: Chronic postherniorrhaphy inguinal pain (CPIP) is common following inguinal hernia repair. As even primary minimally-invasive inguinal hernia repairs carry a risk of significant intra-operative bleeding, it is unsurprising that reoperative groin exploration and mesh explantation for chronic post-inguinal herniorrhaphy pain confers an even higher risk of arteriotomy or venotomy due to a distorted anatomy and the presence of adhesions. In this report, we present a single institution's experience with the management of intra-operative vascular injury encountered during minimally invasive groin exploration and mesh explantation for CPIP.

Materials And Methods: We performed a retrospective consecutive case series study at a single academic center of patients with CPIP who underwent minimally invasive groin exploration and mesh removal during which an iatrogenic arteriotomy or venotomy occurred from September 2015 to September 2020. Descriptive statistics were collected for age, laterality of hernia repair, mean follow-up time, surgical approach (robotic vs. laparoscopic), type of intra-operative vascular injury, vascular control technique, and post-operative complications.

Results: Of 196 minimally invasive groin exploration and mesh removal cases, 46 were performed with robotic assistance and 150 were performed using traditional laparoscopy. The overall incidence of intra-operative vascular injury was 43 (22%). Fifteen of 46 (32%) robotic groin exploration and mesh removal cases and 28 of 150 (19%) laparoscopic cases involved vascular control. Three of 15 (20%) robotic cases and 23 of 28 (82%) laparoscopic cases involved a hybrid open inguinal approach to address anterior pathology (neurectomy, anterior mesh removal, hernia repair) or facilitate exposure for vascular repair. The most common site of injury was the inferior epigastric vessels. Other sites included the iliac vein, iliac artery, corona mortis, and accessory obturator vessels. Vascular control techniques included ligation with an energy device or suture, primary suture repair of injured vessel, or bovine pericardium patch angioplasty. All were managed without intra-operative vascular surgery intervention except for one case with extensive calcification that required endarterectomy and angioplasty to improve patency. No cases required conversion to midline laparotomy. Ninety three percent of the cases with large vessel bleeding during laparoscopic-assisted procedures were repaired via an open groin incision, whereas all cases of large vessel bleeding during robotic-assisted procedures were repaired robotically. None of the patients required transfusion. Postoperative complications occurred in 3 patients (7%), 2 (5%) developed hematoma formation requiring surgical evacuation, and 1 (2%) developed ipsilateral iliofemoral deep vein thrombosis (DVT) and underwent peripheral angiography and thrombolysis.

Conclusions: Although minimally invasive groin exploration and mesh explantation for CPIP is technically challenging, it is a safe and effective operation when performed at experienced centers. Iatrogenic vascular injury should be anticipated but can be effectively controlled laparoscopically, robotically, or via a hybrid open inguinal incision without conversion to a midline laparotomy and with low post-operative complication rates.
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April 2021

Clinical Guidelines Synopsis of Groin Hernia Management.

JAMA Surg 2020 Oct;155(10):980-981

Americas Hernia Society, Los Angeles, California.

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http://dx.doi.org/10.1001/jamasurg.2020.2608DOI Listing
October 2020

Effects and Interferences of Emicizumab, a Humanised Bispecific Antibody Mimicking Activated Factor VIII Cofactor Function, on Coagulation Assays.

Thromb Haemost 2019 Jul 7;119(7):1084-1093. Epub 2019 May 7.

Genentech, Inc., South San Francisco, California, United States.

Emicizumab bridges activated factor IX (FIX) and FX to restore the tenase function mediated by activated FVIII (FVIIIa), which is deficient in people with haemophilia A (PwHA). Unlike FVIII, emicizumab does not require activation to function; thus, in coagulation assays, the behavior of emicizumab may differ from that of FVIII. The objective of this study was to assess the effect of emicizumab on coagulation assays, including potential interference behavior that may produce inaccurate or misleading results. A variety of clotting-based, amidolytic/chromogenic, latex particle-enhanced turbidometric, and enzyme-linked immunosorbent methods were investigated. As expected based on its pharmacologic mechanism of action, emicizumab exhibited strong activity on the activated partial thromboplastin time (aPTT), which resulted in interference with several aPTT-based assays, most importantly the one-stage FVIII activity assay; these assays are not recommended for PwHA receiving emicizumab therapy. Pharmacodynamic activity of emicizumab, as measured by FVIII chromogenic assays, was species-dependent due to the binding specificity of the drug antibody. Outside of FVIII assays, emicizumab did not interfere with assays based on immunologic or chromogenic principles, nor with clotting assays based on nonintrinsic pathway activators, thus offering alternative choices where aPTT-based assays might otherwise be used. The observed interferences are in line with the unique mechanism of action of emicizumab. Potential interferences should be taken into account in the selection of coagulation assays and interpretation of coagulation assay test results for PwHA receiving emicizumab therapy.
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http://dx.doi.org/10.1055/s-0039-1688687DOI Listing
July 2019

Prevention of Parastomal Hernia.

Surg Technol Int 2018 Sep 11;33. Epub 2018 Sep 11.

Lichtenstein Amid Hernia Clinic, David Geffen School of Medicine at University, of California, Los Angeles, Santa Monica, CA.

Parastomal hernia (PSH), defined as an incisional hernia at the abdominal wall defect resulting from stoma formation, is a frequent complication of enterostomy (ileostomy and jejunostomy), colostomy, and urostomy. A growing body of evidence supports the use of prophylactic mesh at the time of stoma creation to prevent the development of PSH. In particular, the use of permanent mesh has been supported in the creation of an end colostomy, and prophylactic mesh has been studied for use in other types of stoma. Permanent mesh materials used for PSH prophylaxis include polypropylene, polyester, polytetrafluoroethylene, and composite prosthetics. Despite the appeal of biologic and bioabsorbable materials in an operative field that poses a potentially higher risk of infection, there is insufficient evidence to support their use in primary PSH prevention. Two-dimensional meshes are usually cut to contain a keyhole through which the bowel passes, and may be placed in the sublay/retrorectus, intraperitoneal, or preperitoneal position. Alternative techniques include placement of a non-keyhole mesh in a position similar to that of a Sugarbaker PSH repair or use of a circular stapler fired through the abdominal wall fascia and mesh simultaneously, fixing both together. Three-dimensional mesh devices, including the Prolene® and Ultrapro® Hernia Systems (PHS/UHS) (Ethicon US, LLC, Somerville, NJ), have been studied for use in PSH prevention. Novel, specialized devices such as the Koring™ (Koring AG, Basel, Switzerland) stoma mesh have been designed specifically for primary PSH prevention. While the benefits of mesh prophylaxis have been established, further evidence is needed to identify the optimal materials and technique for PSH prevention in a variety of patients and settings. The purpose of this report is to provide an overview of the operative techniques and evidence supporting prophylaxis of parastomal hernias.
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September 2018

Blended Learning Methods for Surgical Education.

Surg Technol Int 2018 Nov;33:127-132

Lichtenstein Amid Hernia Clinic, David Geffen School of Medicine at University, of California, Los Angeles, Santa Monica, CA.

The emergence and maturation of the concept of blended learning in public and military education may prove equally valuable in CME surgical education and training. Creating a learner-centric environment in which multiple modes of education are encouraged, available, integrated, and accredited can increase the level of competence achieved in CME courses. This paper defines a framework for blended surgical training using principles developed for the military and it is applied in courses at a major post-graduate surgical education center.
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November 2018

Approach to the Patient with Chronic Groin Pain.

Surg Clin North Am 2018 Jun 4;98(3):651-665. Epub 2018 Apr 4.

Department of Surgery, University of California at Los Angeles, 757 Westwood Plaza, Los Angeles, CA 90095, USA. Electronic address:

Chronic postoperative inguinal pain has become a primary outcome parameter after elective inguinal hernia repair with significant consequences affecting patient productivity, employment, and quality of life. A systematic and thorough preoperative evaluation is important to identify the etiologies and types of pain. Owing to the complex nature of chronic pain, a multimodal and multidisciplinary treatment approach is recommended. Patients with chronic pain refractory to conservative measures may be considered for surgical intervention. Triple neurectomy remains the most definitive and accepted remedial operation performed and provides effective relief in the majority of patients.
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http://dx.doi.org/10.1016/j.suc.2018.02.002DOI Listing
June 2018

Implementation of a flipped classroom approach to promote active learning in the third-year surgery clerkship.

Am J Surg 2018 Feb 6;215(2):298-303. Epub 2017 Nov 6.

University of California, Los Angeles David Geffen School of Medicine, Los Angeles, CA, USA.

Background: Constructivist student-centered instructional models such as the flipped classroom (FC) have been shown to improve learning.

Methods: A FC approach was implemented for the surgery clerkship. Data was collected in phase 1 to evaluate student learning and attitudes. Based on these results, questions for the phase 2 open-ended survey were developed to improve understanding of learner attitudes, and ascertain how well the FC aligns with constructivist principles.

Results: There was no significant difference in shelf exam performance between the control and intervention groups. A majority of students agreed that they preferred the FC over lectures, and that their learning improved. Open-ended survey analysis demonstrated that the FC fostered self-directed, active learning, and that the in-class sessions facilitated application of concepts and deeper learning. Areas identified for improvement included better alignment with learning preferences through greater variety of pre-class learning options, improvement of podcast technical quality, and utilization of smaller in-class discussion groups.

Conclusions: Students had a positive perception of the FC. The FC supports self-directed and more active and deeper in-class learning.
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http://dx.doi.org/10.1016/j.amjsurg.2017.08.050DOI Listing
February 2018

Web-Based Video Assessments of Operative Performance for Remote Telementoring.

Surg Technol Int 2017 Jul;30:25-30

Department of Surgery, David Geffen School of Medicine at UCLA, Los Angeles, California.

Introduction: Performance-based feedback is critical to surgical skills acquisition. Barriers of geography and time limit trainees' access to expert mentorship. In this study, we hypothesized that telementoring using an asynchronous, web-based video interface would allow trainees to receive systematic feedback from expert mentors despite these barriers.

Materials And Methods: Between October 2014 and October 2016, 18 surgeons in Brazil, Dominican Republic, Haiti, and Paraguay underwent in-person training in Lichtenstein for hernioplasty or laparoscopic total extraperitoneal inguinal hernia repair. After initial training, surgeons submitted 6- to 12-month interval operative videos for expert review. Expert surgeons reviewed each video using the Surgus web platform with performance metrics adapted from the Operative Performance Rating Scale (OPRS). The time required to perform video review, number of freeform comments, mean OPRS scores, and variance of OPRS scores among telementors was assessed.

Results: A total of 18 surgeons submitted 20 operative videos, and three expert surgeons reviewed each video using the Surgus platform. The median time to perform video review was 20 minutes. Median number of freeform verbal comments was eight. Mean OPRS overall performance scores were 3.9 ± 0.9 (scale of five). Mean variance in scoring among telementors for overall performance was 0.25 (maximum 5.29), suggesting a high degree of concordance.

Conclusions: Video-based assessments had a high degree of concordance among expert raters. Asynchronous performance reviews by telementors offer opportunities for longitudinal feedback that overcome geographical, material, and temporal disparities. This platform offers a means of sharing expertise in surgical training, continuing education, credentialing, and global health.
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July 2017

Sex-Specific Differences in Colon Cancer when Quality Measures Are Adhered to: Results from International, Prospective, Multicenter Clinical Trials.

J Am Coll Surg 2017 Jul 6;225(1):85-92. Epub 2017 Apr 6.

Department of Surgical Oncology, John Wayne Cancer Institute, University of California Los Angeles, Santa Monica, CA.

Background: There is no consensus on the relationship between patient sex and the location, stage, and oncologic outcome of colon cancer (CC). We hypothesized that there is a sex-specific difference in the biology and management of CC.

Study Design: Our cohort was drawn from a database of patients enrolled in international trials of nodal ultrastaging for nonmetastatic CC. These trials required strict adherence to surgical and pathologic quality measures. Postoperative follow-up included colonoscopy at 1 and 4 years and annual CT scans. Sex-specific differences in tumor biology, location, stage, and recurrence were evaluated by chi-square, Fischer's exact, and independent t-tests.

Results: The cohort included 435 males (median age 69 years) and 423 females (median age 70 years). Females had more right-sided (p = 0.03) and earlier T stage (p = 0.05) tumors, but there was no sex-based difference in pathologic grade, total lymph nodes retrieved, nodal positivity (p = 0.47) or lymphovascular invasion (p = 0.45). The overall 4-year disease-free survival (DFS) was comparable in females and males (77.9% and 77.5%, respectively). By multivariate analysis, only nodal positivity and cancer recurrence affected overall survival (OS) (p = 0.008). Neither sex nor primary tumor affected DFS or OS.

Conclusions: This is the first prospective study to demonstrate sex-specific differences in location and T stage of CC when surgical and pathologic management adhered to strict quality standards. The predominance of right-sided CC in females suggests that flexible sigmoidoscopy may be inadequate for screening and surveillance. Interestingly, earlier stage and right-sided location did not confer a DFS or OS advantage for women. Additional studies are needed to determine why females have a higher propensity for right-sided lesions and a potential difference in CC biology.
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http://dx.doi.org/10.1016/j.jamcollsurg.2017.02.019DOI Listing
July 2017

Centralized, capacity-building training of Lichtenstein hernioplasty in Brazil.

Am J Surg 2017 Feb 22;213(2):277-281. Epub 2016 Nov 22.

School of Medical Sciences of Santa Casa de São Paulo, São Paulo, Brazil.

Background: In Brazil, access to healthcare varies widely by community. Options for repair of surgically correctable conditions, such as inguinal hernias, are limited. A training program was instituted to expand access to Lichtenstein hernioplasty.

Methods: Between September, 2014 and September, 2015, 3 orders of training series took place in São Paulo, Brazil. Participating surgeons received training and assessments from expert trainers using the Operative Performance Rating Scale (OPRS). Those who completed training successfully were invited to become trainers. OPRS scores were compared between training series. Outcomes were documented up to 6 months post-training.

Results: The 3 orders of training series resulted in 45 surgeons trained and 213 hernias repaired. Eleven trainees subsequently became trainers. Mean post-training OPRS scores were 4.4 (scale of 5) and did not vary significantly between training series. The overall complication rate was 4.7%, with no hernia recurrences or reoperations at 6 months.

Conclusions: Competency-based training generates a regional network of surgeons proficient in Lichtenstein hernioplasty. Each training session progressively expands patient access to high quality operations in underserved communities in Brazil.
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http://dx.doi.org/10.1016/j.amjsurg.2016.10.011DOI Listing
February 2017

Efficacy of retroperitoneal triple neurectomy for refractory neuropathic inguinodynia.

Am J Surg 2016 Dec 30;212(6):1126-1132. Epub 2016 Sep 30.

Department of Surgery, David Geffen School of Medicine, University of California, 1304 15th Street, Suite 102, Santa Monica, CA 90404, USA. Electronic address:

Background: Refractory neuropathic inguinodynia following inguinal herniorrhaphy is a common and debilitating complication. This prospective study evaluated long-term outcomes associated with laparoscopic retroperitoneal triple neurectomy.

Methods: Sixty-two consecutive patients (51 male; mean age, 47); all failing pain management; prior reoperation in 35, prior neurectomy in 26; average follow-up 681 days (range: 90 days to 3 years). Measured outcomes include numeric pain ratings, dermatomal mapping, histologic confirmation, quantitative sensory testing, complications, narcotic usage, and activity level.

Results: Mean numerical pain scores were significantly decreased (baseline, 8.6) at all postoperative time points (POD 1, 3.6; P < .001: POD 90, 2.3, P < .001) with durable efficacy from POD 90 to 3 years (P < .001). Quantitative sensory testing showed marked group-level increases of sensory thresholds. Narcotic dependence decreased in 57/62 and was eliminated in 44/62 and activity level improved in 58/62.

Conclusions: Retroperitoneal triple neurectomy is an effective and durable treatment for refractory neuropathic inguinodynia.
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http://dx.doi.org/10.1016/j.amjsurg.2016.09.012DOI Listing
December 2016

Laparoscopic Stapled Sublay Repair With Self-Gripping Mesh: A Simplified Technique for Minimally Invasive Extraperitoneal Ventral Hernia Repair.

Surg Technol Int 2016 Oct;29:131-139

Clinical Surgery, David Geffen School of Medicine at UCLA, Los Angeles, California.

Introduction: Minimally invasive laparoscopic and robotic techniques for ventral hernia repair have evolved to achieve the benefits and minimize the limitations of both the open Rives-Stoppa sublay mesh repair and laparoscopic intraperitoneal onlay mesh (IPOM) repair. By combining the principles of a retromuscular repair with the benefits of a minimally invasive approach, these techniques attempt to decrease recurrence, increase functionality, exclude mesh from the viscera, limit infection and wound complications, and minimize pain. The difficult ergonomics, challenging dissection, and extensive suturing make traditional laparoscopic sublay repair technically challenging and has led to increased robotic utilization to overcome these limitations. We describe a laparoscopic extraperitoneal sublay mesh repair technique using an endoscopic stapler to facilitate reapproximation of the linea alba and creation of the retromuscular space, and self-gripping mesh to position and fixate the prosthetic.

Materials And Methods: Between January and June 2016, 10 patients with midline ventral and incisional hernias underwent laparoscopic extraperitoneal stapled sublay mesh repair with self-gripping mesh. Three of these cases included a laparoscopic posterior component separation with myofascial release of the transversus abdominis muscle to facilitate midline closure. Intraoperative and perioperative complications, early recurrence, pain, and narcotic usage were measured.

Results: There were no significant intraoperative complications or conversions to open surgery. Patients were discharged at 1.2 days on average. Early postoperative complications included a hernia site seroma in one patient, which resolved without intervention. There were no early postoperative infections or recurrences. Compared with traditional laparoscopic IPOM repair, there was less acute postoperative pain and use of analgesics.

Conclusions: Laparoscopic extraperitoneal stapled sublay mesh repair is a safe and effective method for the treatment of medium- to large-sized ventral and incisional hernias. This extraperitoneal stapled approach using self-gripping mesh facilitates a minimally invasive sublay repair and abdominal wall reconstruction using traditional laparoscopic tools.
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October 2016

Global Outreach Using a Systematic, Competency-Based Training Paradigm for Inguinal Hernioplasty.

JAMA Surg 2017 01;152(1):66-73

Hernia Repair for the Underserved, Omaha, Nebraska2Department of Surgery, David Geffen School of Medicine, University of California, Los Angeles.

Importance: Sustainable, capacity-building educational collaborations are essential to address the global burden of surgical disease.

Objective: To assess an international, competency-based training paradigm for hernia surgery in underserved countries.

Design, Setting, And Participants: In this prospective, observational study performed from November 1, 2013, through October 31, 2015, at 16 hospitals in Brazil, Ecuador, Haiti, Paraguay, and the Dominican Republic, surgeons completed initial training programs in hernia repair, underwent interval proficiency assessments, and were appointed regional trainers. Competency-based evaluations of technical proficiency were performed using the Operative Performance Rating Scale (OPRS). Maintenance of proficiency was evaluated by video assessments 6 months after training. Certified trainees received incentives to document independent surgical outcomes after training.

Main Outcomes And Measures: An OPRS score of 3.0 (scale of 1 [poor] to 5 [excellent]) indicated proficiency. Secondary outcomes included initial vs final scores by country, scores among surgeons trained by the regional trainers (second-order trainees), interval scores 6 months after training, and postoperative complications.

Results: A total of 20 surgeon trainers, 81 local surgeons, and 364 patients (343 adult, 21 pediatric) participated in the study (mean [SD] age, 47.5 [16.3] years; age range, 16-83 years). All 81 surgeons successfully completed the program, and all 364 patients received successful operations. Mean (SD) OPRS scores improved from 4.06 (0.87) before the initial training program to 4.52 (0.57) after training (P < .001). No significant variation was found by country in final scores. On trainee certification, 20 became regional trainers. The mean (SD) OPRS score among 53 second-order trainees was 4.34 (0.68). After 6-month intervals, the mean (SD) OPRS score among participating surgeons was 4.34 (0.55). The overall operative complication rate during training series was 1.1%.

Conclusions And Relevance: Competency-based training helps address the global burden of surgical disease. The OPRS establishes an international standard of technical assessment. Additional studies of long-term surgeon trainer proficiency, community-specific quality initiatives, and expansion to other operations are warranted.
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http://dx.doi.org/10.1001/jamasurg.2016.3323DOI Listing
January 2017

Groin Pain After Inguinal Hernia Repair.

Adv Surg 2016 09 9;50(1):203-20. Epub 2016 Jul 9.

Department of Surgery, David Geffen School of Medicine at UCLA, 10833 Le Conte Avenue, Los Angeles, CA 90095, USA; Lichtenstein Amid Hernia Clinic at UCLA, 1304 15th Street, Suite 102, Santa Monica, CA 90404, USA. Electronic address:

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http://dx.doi.org/10.1016/j.yasu.2016.04.003DOI Listing
September 2016

Neurophysiological and Clinical Effects of Laparoscopic Retroperitoneal Triple Neurectomy in Patients with Refractory Postherniorrhaphy Neuropathic Inguinodynia.

Pain Pract 2017 04 23;17(4):447-459. Epub 2016 Jun 23.

Department of Surgery, Lichtenstein Amid Hernia Clinic at UCLA, Los Angeles, California, U.S.A.

Background: Chronic postherniorrhaphy inguinal pain (CPIP) is a complex, major health problem. In the absence of recurrence or meshoma, laparoscopic retroperitoneal triple neurectomy (LRTN) has emerged as an effective surgical treatment of CPIP.

Methods: This prospective pilot study evaluated the neurophysiological and clinical effects of LRTN. Ten consecutive adult CPIP patients with unilateral predominantly neuropathic inguinodynia underwent three comprehensive quantitative sensory testing (QST) assessments (preoperative, immediate postoperative, and late postoperative). Pain severity, health-related function, and sleep quality were assessed over the course of a 6-month follow-up period.

Results: QST revealed marked increases in mechanical, pressure, thermal, and pain thresholds in the areas with maximum pain prior to LRTN surgery for the immediate (P < 0.01; mean 160.9 minutes, range 103 to 255 minutes after extubation) and late postoperative (P < 0.05; mean 27.9 days, range 14 to 78 days after surgery) assessments compared to baseline. Wind-up phenomena were eliminated postoperatively. LRTN provided robust group-level improvements of all clinical measures. No preoperative QST variables were found to be predictive of surgical outcomes. The positive change in heat pain threshold (preoperative compared to late postoperative) showed significant positive correlations with improvements of pain scores and function.

Conclusions: LRTN may produce immediate, profound, and consistent positive effects across multiple mechanical, pressure, and thermal QST variables, and marked improvements of clinical outcomes in selected CPIP patients. These data contribute to the understanding of mechanisms involved in the success of LRTN. Large, high-powered studies are warranted to determine whether preoperative or repeated longitudinal QST may guide patient selection and predict effectiveness of LRTN.
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http://dx.doi.org/10.1111/papr.12468DOI Listing
April 2017

Articulating and Reloadable Fixation Devices for Hernia Repair.

Surg Technol Int 2016 Apr;28:133-8

Department of General Surgery, Lichtenstein Amid Clinic at UCLA, University of California Los Angeles, CA.

There have been a variety of absorbable and permanent tacks, tack deployment systems, and fasteners developed for the fixation of mesh during laparoscopic ventral hernia repair. The manufacturer recommendation for all systems is for perpendicular deployment of these tacks into the tissue. Achieving this optimal angle with previously developed deployment systems is often challenging and can lead to tack failure, mesh migration, and recurrence, or may require the placement of additional ports. Additionally, current tack deployment systems lack the ability to reload, leading to increased cost when entire systems must be opened each time a reload is necessary. This article presents products designed to addresses both of these problems. These deployment instruments incorporate an articulating shaft or a hinge mechanism allowing for improved access to different parts of the abdominal cavity and delivering perpendicular placement of tacks with fewer port sites. Devices with the option of reloadable fixation decrease costs and reduce waste.
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April 2016

A genome-wide association study identifies four novel susceptibility loci underlying inguinal hernia.

Nat Commun 2015 Dec 21;6:10130. Epub 2015 Dec 21.

Kaiser Permanente Northern California, Division of Research, Oakland, California 94612, USA.

Inguinal hernia repair is one of the most commonly performed operations in the world, yet little is known about the genetic mechanisms that predispose individuals to develop inguinal hernias. We perform a genome-wide association analysis of surgically confirmed inguinal hernias in 72,805 subjects (5,295 cases and 67,510 controls) and confirm top associations in an independent cohort of 92,444 subjects with self-reported hernia repair surgeries (9,701 cases and 82,743 controls). We identify four novel inguinal hernia susceptibility loci in the regions of EFEMP1, WT1, EBF2 and ADAMTS6. Moreover, we observe expression of all four genes in mouse connective tissue and network analyses show an important role for two of these genes (EFEMP1 and WT1) in connective tissue maintenance/homoeostasis. Our findings provide insight into the aetiology of hernia development and highlight genetic pathways for studies of hernia development and its treatment.
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http://dx.doi.org/10.1038/ncomms10130DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4703831PMC
December 2015

Innovation in Pediatric Surgical Education for General Surgery Residents: A Mobile Web Resource.

J Surg Educ 2015 Nov-Dec;72(6):1190-4. Epub 2015 Aug 11.

Department of Surgery, David Geffen School of Medicine at UCLA, Los Angeles, California.

Background/objectives: General surgery residents lack a standardized educational experience in pediatric surgery. We hypothesized that the development of a mobile educational interface would provide general surgery residents broader access to pediatric surgical education materials.

Methods: We created an educational mobile website for general surgery residents rotating on pediatric surgery, which included a curriculum, multimedia resources, the Operative Performance Rating Scale (OPRS), and Twitter functionality. Residents were instructed to consult the curriculum. Residents and faculty posted media using the Twitter hashtag, #UCLAPedSurg, and following each surgical procedure reviewed performance via the OPRS. Site visits, Twitter posts, and OPRS submissions were quantified from September 2013 to July 2014.

Results: The pediatric surgery mobile website received 257 hits; 108 to the homepage, 107 to multimedia, 28 to the syllabus, and 19 to the OPRS. All eligible residents accessed the content. The Twitter hashtag, #UCLAPedSurg, was assigned to 20 posts; the overall audience reach was 85 individuals. Participants in the mobile OPRS included 11 general surgery residents and 4 pediatric surgery faculty.

Conclusion: Pediatric surgical education resources and operative performance evaluations are effectively administered to general surgery residents via a structured mobile platform.
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http://dx.doi.org/10.1016/j.jsurg.2015.06.025DOI Listing
September 2016

Wearable Technology for Global Surgical Teleproctoring.

J Surg Educ 2015 Nov-Dec;72(6):1290-5. Epub 2015 Aug 11.

Department of Surgery, David Geffen School of Medicine, University of California, Los Angeles, California. Electronic address:

Objective: In underserved communities around the world, inguinal hernias represent a significant burden of surgically-treatable disease. With traditional models of international surgical assistance limited to mission trips, a standardized framework to strengthen local healthcare systems is lacking. We established a surgical education model using web-based tools and wearable technology to allow for long-term proctoring and assessment in a resource-poor setting. This is a feasibility study examining wearable technology and web-based performance rating tools for long-term proctoring in an international setting.

Methods: Using the Lichtenstein inguinal hernia repair as the index surgical procedure, local surgeons in Paraguay and Brazil were trained in person by visiting international expert trainers using a formal, standardized teaching protocol. Surgeries were captured in real-time using Google Glass and transmitted wirelessly to an online video stream, permitting real-time observation and proctoring by mentoring surgeon experts in remote locations around the world. A system for ongoing remote evaluation and support by experienced surgeons was established using the Lichtenstein-specific Operative Performance Rating Scale.

Results: Data were collected from 4 sequential training operations for surgeons trained in both Paraguay and Brazil. With continuous internet connectivity, live streaming of the surgeries was successful. The Operative Performance Rating Scale was immediately used after each operation. Both surgeons demonstrated proficiency at the completion of the fourth case.

Conclusions: A sustainable model for surgical training and proctoring to empower local surgeons in resource-poor locations and "train trainers" is feasible with wearable technology and web-based communication. Capacity building by maximizing use of local resources and expertise offers a long-term solution to reducing the global burden of surgically-treatable disease.
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http://dx.doi.org/10.1016/j.jsurg.2015.07.004DOI Listing
September 2016

Prognostic Effect of Ultra-Staging Node-Negative Colon Cancer Without Adjuvant Chemotherapy: A Prospective National Cancer Institute-Sponsored Clinical Trial.

J Am Coll Surg 2015 Sep 18;221(3):643-51; quiz 783-5. Epub 2015 May 18.

University of California, Los Angeles, Los Angeles, CA; John Wayne Cancer Institute at Providence Saint John's Health Center, Santa Monica, CA; California Oncology Research Institute, Santa Monica, CA. Electronic address:

Background: We recently reported, in a prospective randomized trial, that ultra-staging of patients with colon cancer is associated with significantly improved disease-free survival (DFS) compared with conventional staging. That trial did not control for lymph node (LN) number or adjuvant chemotherapy use.

Study Design: The current international prospective multicenter cooperative group trial (ClinicalTrials.gov identifier NCT00949312; "Ultra-staging in Early Colon Cancer") evaluates the 12-LN quality measure and nodal ultra-staging impact on DFS in patients not receiving adjuvant chemotherapy. Eligibility criteria included biopsy-proven colon adenocarcinoma; absence of metastatic disease; >12 LNs staged pathologically; pan-cytokeratin immunohistochemistry (IHC) of hematoxylin and eosin (H&E)-negative LNs; and no adjuvant chemotherapy.

Results: Of 445 patients screened, 203 patients were eligible. The majority of patients had intermediate grade (57.7%) and T3 tumors (64.9%). At a mean follow-up of 36.8 ± 22.1 months (range 0 to 97 months), 94.3% remain disease free. Recurrence was least likely in patients with ≥12 LNs, H&E-negative LNs, and IHC-negative LNs (pN0i-): 2.6% vs 16.7% in the pN0i+ group (p < 0.0001).

Conclusions: This is the first prospective report to demonstrate that patients with optimally staged node-negative colon cancer (≥12 LNs, pN0i-) are unlikely to benefit from adjuvant chemotherapy; 97% remain disease free after primary tumor resection. Both surgical and pathologic quality measures are imperative in planning clinical trials in nonmetastatic colon cancer.
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http://dx.doi.org/10.1016/j.jamcollsurg.2015.05.007DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4657939PMC
September 2015

A real-time mobile web-based module promotes bidirectional feedback and improves evaluations of the surgery clerkship.

Am J Surg 2015 Jan 22;209(1):101-6. Epub 2014 Oct 22.

Department of Surgery, David Geffen School of Medicine, University of California, 10833 Le Conte Ave 72-235 CHS, Los Angeles, CA 90095, USA.

Background: We implemented a real-time mobile web-based reporting module for students in our surgery clerkship and evaluated its effect on student satisfaction and perceived abuse.

Methods: Third-year medical students in the surgery clerkship received surveys regarding intimidation, perceived abuse, satisfaction with clerkship resources, and interest in a surgical career. Survey data were analyzed to assess differences after implementing the mobile reporting system and to identify independent predictors of perceived abuse.

Results: With the reporting module, students perceived less intimidation by residents (P < .001) and by faculty (P = .008), greater satisfaction reporting feedback (P < .001), and greater interest in surgical careers (P = .003). Perceived abuse decreased without reaching statistical significance (P = .331). High ratings of intimidation by faculty independently predicted perceived abuse (odds ratio = 1.3), and satisfaction with anonymous reporting was a negative predictor (odds ratio = .2).

Conclusions: A mobile web-based system for real-time reporting fosters open communication and bidirectional feedback and promotes greater satisfaction with the surgery clerkship and interest in a surgical career.
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http://dx.doi.org/10.1016/j.amjsurg.2014.08.035DOI Listing
January 2015

Assessment of resident operative performance using a real-time mobile Web system: preparing for the milestone age.

J Surg Educ 2014 Nov-Dec;71(6):e41-6. Epub 2014 Jul 16.

David Geffen School of Medicine, University of California, Los Angeles, California.

Objective: To satisfy trainees' operative competency requirements while improving feedback validity and timeliness using a mobile Web-based platform.

Design: The Southern Illinois University Operative Performance Rating Scale (OPRS) was embedded into a website formatted for mobile devices. From March 2013 to February 2014, faculty members were instructed to complete the OPRS form while providing verbal feedback to the operating resident at the conclusion of each procedure. Submitted data were compiled automatically within a secure Web-based spreadsheet. Conventional end-of-rotation performance (CERP) evaluations filed 2006 to 2013 and OPRS performance scores were compared by year of training using serial and independent-samples t tests. The mean CERP scores and OPRS overall resident operative performance scores were directly compared using a linear regression model. OPRS mobile site analytics were reviewed using a Web-based reporting program.

Setting: Large university-based general surgery residency program.

Participants: General Surgery faculty used the mobile Web OPRS system to rate resident performance. Residents and the program director reviewed evaluations semiannually.

Results: Over the study period, 18 faculty members and 37 residents logged 176 operations using the mobile OPRS system. There were 334 total OPRS website visits. Median time to complete an evaluation was 45 minutes from the end of the operation, and faculty spent an average of 134 seconds on the site to enter 1 assessment. In the 38,506 CERP evaluations reviewed, mean performance scores showed a positive linear trend of 2% change per year of training (p = 0.001). OPRS overall resident operative performance scores showed a significant linear (p = 0.001), quadratic (p = 0.001), and cubic (p = 0.003) trend of change per year of clinical training, reflecting the resident operative experience in our training program. Differences between postgraduate year-1 and postgraduate year-5 overall performance scores were greater with the OPRS (mean = 0.96, CI: 0.55-1.38) than with CERP measures (mean = 0.37, CI: 0.34-0.41). Additionally, there were consistent increases in each of the OPRS subcategories.

Conclusions: In contrast to CERPs, the OPRS fully satisfies the Accreditation Council for Graduate Medical Education and American Board of Surgery operative assessment requirements. The mobile Web platform provides a convenient interface, broad accessibility, automatic data compilation, and compatibility with common database and statistical software. Our mobile OPRS system encourages candid feedback dialog and generates a comprehensive review of individual and group-wide operative proficiency in real time.
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http://dx.doi.org/10.1016/j.jsurg.2014.06.008DOI Listing
July 2015

Pain control following inguinal herniorrhaphy: current perspectives.

J Pain Res 2014 29;7:277-90. Epub 2014 May 29.

Department of Surgery, Lichtenstein Amid Hernia Clinic at UCLA, UCLA, Los Angeles, CA, USA.

Inguinal hernia repair is one of the most common surgeries performed worldwide. With the success of modern hernia repair techniques, recurrence rates have significantly declined, with a lower incidence than the development of chronic postherniorrhaphy inguinal pain (CPIP). The avoidance of CPIP is arguably the most important clinical outcome and has the greatest impact on patient satisfaction, health care utilization, societal cost, and quality of life. The etiology of CPIP is multifactorial, with overlapping neuropathic and nociceptive components contributing to this complex syndrome. Treatment is often challenging, and no definitive treatment algorithm exists. Multidisciplinary management of this complex problem improves outcomes, as treatment must be individualized. Current medical, pharmacologic, interventional, and surgical management strategies are reviewed.
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http://dx.doi.org/10.2147/JPR.S47005DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4045265PMC
June 2014

Prevention of inguinodynia: the need for continuous refinement and quality improvement in inguinal hernia repair.

World J Surg 2014 Oct;38(10):2571-3

Department of Surgery, Lichtenstein Amid Hernia Clinic at UCLA, UCLA David Geffen School of Medicine, Santa Monica, CA, USA.

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http://dx.doi.org/10.1007/s00268-014-2626-8DOI Listing
October 2014

Operative management of refractory neuropathic inguinodynia by a laparoscopic retroperitoneal approach.

JAMA Surg 2013 Oct;148(10):962-7

Department of Surgery, Lichtenstein-Amid Hernia Clinic, David Geffen School of Medicine, University of California, Los Angeles.

Importance: With the technical success of tension-free inguinal herniorrhaphy, chronic groin pain has far surpassed recurrence as the most common long-term complication.

Objective: To evaluate laparoscopic triple neurectomy of the ilioinguinal, iliohypogastric, and genitofemoral nerve trunks in the retroperitoneal lumbar plexus for treatment of refractory inguinodynia.

Design: Prospective study.

Setting: University hernia center.

Participants: Twenty consecutive patients with chronic inguinodynia (14 male; mean age, 46 years; all failing pain management; prior neurectomy in 4 patients) and follow-up to 180 days (minimum, 90 days).

Main Outcomes And Measures: Groin pain (Numeric Rating Scale score), dermatomal mapping, hernia recurrence, histologic confirmation, and complications.

Results: There were no intraoperative complications. All patients had histologic confirmation of neurectomy and clinical confirmation with dermatomal mapping. Mean numeric pain scores were significantly decreased (baseline score, 7.8) on postoperative days 1 (score, 2.9; P < .001), 7 (score, 2.2; P < .001), 30 (score, 1.7; P < .001), and 90 (score, 1.9; P < .001). Narcotic dependence decreased and activity level increased. Five patients reported transient hypersensitivity consistent with deafferentation. All had numbness in the distribution of neurectomy without complaint. Four had residual meshoma pain, with 2 undergoing subsequent reoperation to remove mesh. Orchialgia was not improved.

Conclusions And Relevance: This represents the largest series of laparoscopic retroperitoneal triple neurectomies for treatment of inguinodynia. The rate of successful intervention was better than reported for standard triple neurectomy and open extended triple neurectomy. The procedure allows access proximal to all potential sites of peripheral neuropathy and overcomes many of the limitations of open triple neurectomy. In the absence of recurrence or meshoma, it is the preferred technique for definitive management of chronic inguinal neuralgia.
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http://dx.doi.org/10.1001/jamasurg.2013.3189DOI Listing
October 2013

Delayed Migration of a WallFlex Enteral Stent Resulting in Jejunal Perforation.

Case Rep Gastrointest Med 2013 22;2013:652597. Epub 2013 Apr 22.

Department of Medicine, UCLA Medical Center, Los Angeles, CA 90095, USA.

Enteral stents are increasingly utilized to palliate malignant gastrointestinal obstruction; however, they can be associated with significant complications. We describe an unusual case of a 67-year-old male with gastric adenocarcinoma who underwent placement of a WallFlex metallic enteral stent to relieve a malignant gastric outlet obstruction. Four months later, while actively undergoing chemotherapy, he developed acute abdominal pain and was found to have delayed stent migration and jejunal perforation. He required emergent surgical resection of the perforated segment of jejunum. Delayed migration of the WallFlex enteral stent with subsequent visceral perforation has yet to be reported in the literature. Chemotherapy after stent placement has been associated with an increase in maintenance of stent patency; however, shrinkage of the local tumor by chemoradiation may increase the risk of stent migration. Care should be taken in placing enteral stents in patients undergoing continued treatment of their malignancy, as delayed migration of even uncovered stents may occur.
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http://dx.doi.org/10.1155/2013/652597DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3654626PMC
May 2013

Spheroid formation and enhanced cardiomyogenic potential of adipose-derived stem cells grown on chitosan.

Biores Open Access 2013 Feb;2(1):28-39

Institute of Polymer Science and Engineering, National Taiwan University , Taipei, Taiwan .

Mesenchymal stem cells may differentiate into cardiomyocytes and participate in local tissue repair after heart injury. In the current study, rat adipose-derived adult stem cells (ASCs) grown on chitosan membranes were observed to form cell spheroids after 3 days. The cell seeding density and surface modification of chitosan with Arg-Gly-Asp-containing peptide had an influence on the sizes of ASC spheroids. In the absence of induction, these spheroids showed an increased level of cardiac marker gene expression (Gata4, Nkx2-5, Myh6, and Tnnt2) more than 20-fold versus cells on the tissue culture polystyrene (TCPS) dish. Induction by 5-azacytidine or p38 MAP kinase inhibitor (SB202190) did not further increase the cardiac marker gene expression of these spheroids. Moreover, the enhanced cardiomyogenic potential of the spheroids was highly associated with the chitosan substrates. When ASC spheroids were plated onto TCPS with either basal or cardiac induction medium for 9 days, the spheroids spread into a monolayer and the positive effect on cardiomyogenic marker gene expression disappeared. The possible role of calcium ion and the up-regulation of adhesion molecule P-selectin and chemokine receptor Cxcr4 were demonstrated in ASC spheroids. Applying these spheroids to the chronic myocardial infarction animal model showed better functional recovery versus single cells after 12 weeks. Taken together, this study suggested that the ASC spheroids on chitosan may form as a result of calcium ion signaling, and the transplantation of these spheroids may offer a simple method to enhance the efficiency of stem cell-based therapy in myocardial infarction.
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http://dx.doi.org/10.1089/biores.2012.0285DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3569958PMC
February 2013

Quality improvement pilot program for vulnerable elderly surgical patients.

Am Surg 2011 Oct;77(10):1305-8

Department of Surgery, David Geffen School of Medicine at UCLA, Los Angeles, California 90095-6904, USA.

The elderly are a growing surgical population with more comorbidities and less physiological reserve compared with nonelderly patients. The objective of our study was to implement a quality improvement pilot program targeting the specific needs of the elderly. We prospectively enrolled consecutive patients aged 65 years or older undergoing inpatient general or vascular surgery operations. Patients completed a preoperative assessment including the Vulnerable Elder Survey (VES) to determine baseline functional status and incidence of polypharmacy (five or more medications). They were interviewed postdischarge Day 2 and Day 30 for changes in functional status. An intervention was implemented consisting of an elderly-specific postoperative order set and preoperative risk reports sent to the surgical team with instructions to order physical therapy consults and home health nursing on discharge for VES 3 or greater and geriatrics consults for patients with polypharmacy. The elderly-specific order set was used for 71 per cent of the postintervention group. There were no differences in the percentage of participants receiving physical therapy, geriatric, or home health nursing consults between the two groups. The postintervention group had significantly better functional status on postdischarge Day 30 (P < 0.01). Our preliminary data suggest that individualizing care for elderly patients is feasible and may improve postoperative outcomes.
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October 2011

Surgical treatment of chronic groin and testicular pain after laparoscopic and open preperitoneal inguinal hernia repair.

J Am Coll Surg 2011 Oct 23;213(4):531-6. Epub 2011 Jul 23.

Lichtenstein Hernia Institute, Santa Monica, CA, USA.

Background: Standard triple neurectomy does not address inguinodynia secondary to neuropathy of the genitofemoral nerve and the preperitoneal segment of its genital branch seen after inguinal hernia repair performed laparoscopically or in open preperitoneal fashion.

Study Design: Standard triple neurectomy was extended to include the genitofemoral nerve. Sixteen patients with chronic groin pain after laparoscopic and open preperitoneal inguinal hernia repair underwent operative triple neurectomy, with resection of the main trunk of the genitofemoral nerve in the retroperitoneum over the psoas muscle. All patients had previously undergone unsuccessful extensive nonsurgical pain management.

Results: Fourteen of 16 patients had significant improvement of their pain, as evidenced by a decrease in subjectively reported postoperative pain levels as compared with their preoperative baseline, a decrease or complete elimination of daily narcotic dependence, and return to baseline activities of daily living and work. One of the nonresponder patients underwent a previous open prostatectomy, and exposure of the genitofemoral nerve was not possible due to scarring from the prostatectomy. The other nonresponder patient continues to experience subjective pain equivalent to preoperative levels due to the sensation of firmness and incisional pain that arose in the setting of a postoperative wound infection. He does, however, report that his pain is of different character and quality from his preneurectomy pain and is primarily centered around the incision. His follow-up has not been long enough to determine if his symptoms will improve as his incision and scar remodel.

Conclusions: Extension of the standard triple neurectomy to include the genitofemoral nerve for treatment of inguinodynia after open and laparoscopic preperitoneal mesh repair is a safe and effective procedure.
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http://dx.doi.org/10.1016/j.jamcollsurg.2011.06.424DOI Listing
October 2011