The Viscoelastic Behavior of Soft Tissues Must be Accounted for in Stapler Design and Surgeon Technique.

BACKGROUND: Since its adoption as a surgical technique over a half-century ago, stapling has continually undergone improvements, both in the devices used and in our understanding of tissue mechanics. To best design and use stapling devices, it is beneficial to have an intimate knowledge of the response of tissue to compression and stapling dynamics. This paper provides the relevant background in the field of biomechanics, and in particular addresses the viscoelastic behavior of soft tissues under compression. Biomechanics of Stapling: The change in shape of a solid, or strain, is related to the load applied, or stress. Biological tissues are known to have non-linear relationships between stress and strain, and generally the relationships are anisotropic (dependent upon direction). Further complicating matters, there is typically a time-dependency to the relationship for compression and recovery, resulting in viscoelastic behavior. Hence both the amount and rate of compressive force applied can be expected to impact the outcome of stapling. DISCUSSION: The growth of the laparoscopic use of staples has increased the difficulty of device design, as precise control of compression is problematic in extended length staplers. Progressive firing along the cartridge and multi-stage compression have both been found to be beneficial in providing the uniform force needed to produce well-formed staples. Such technical advances can reduce stresses within the stapler, preventing deformation of the stapler arm and undesirable strain in the tissue. Current research includes understanding the effects of changing the rate of compression on staple formation with the hope that further improvements can be achieved in this ever-fruitful method of tissue apposition.

Clinical Factors Associated With Remission of Obesity-Related Comorbidities After Bariatric Surgery.

IMPORTANCE: Little is known about comorbidity remission after bariatric surgery during typical clinical care across diverse and geographically distributed populations. OBJECTIVE: To estimate the improvement in obesity-related comorbidities after bariatric surgery and to identify clinical factors associated with these responses using a large representative population of patients. DESIGN, SETTING, AND PARTICIPANTS: This retrospective cohort study included all patients (N = 33,718) with a recorded Current Procedural Terminology code for Roux-en-Y gastric bypass (RYGB) or adjustable gastric banding (AGB) in the MarketScan Commercial Claims and Encounters Medicare Supplemental Databases from January 1, 2005, to June 30, 2010, and who had continuous enrollment from 6 months or more before to 12 months after surgery. MAIN OUTCOMES AND MEASURES: Comorbidities before and after surgery were identified using both diagnoses (from International Classification of Diseases, Ninth Revision [ICD-9] codes) and prescription drug fills. Remission was based on a record of the comorbidity within 6 months before surgery, without record of the condition 18 months after surgery, using both ICD-9 codes and medication fills, as applicable. Multivariable logistic regression models were developed to identify factors associated with remission of diabetes and hypertension. RESULTS: Among the 33,718 patients, 13 comorbidities with at least 1% prevalence before surgery were identified. Both RYGB and AGB led to statistically and clinically significant reductions in these comorbidities; remission rates for all comorbidities were higher after RYGB than AGB. For comorbidities that could be defined using both ICD-9 and prescription drug fill codes, prevalence was higher before and lower after surgery when measured by fill codes. Diagnoses using ICD-9 codes, but not prescription fill codes, increased in the 3 months before surgery. In multivariable logistic regression models for remission of diabetes mellitus after RYGB and AGB, age (RYGB: odds ratio [OR], 0.976; 95% CI, 0.965-0.988 and AGB: OR, 0.982; 95% CI, 0.971-0.933), procedure year (RYGB: OR, 1.11; 95% CI, 1.012-1.218 and AGB: OR, 1.185; 95% CI, 1.039-1.351), preoperative insulin use (RYGB: OR, 0.14; 95% CI, 0.114-0.171; AGB: OR, 0.174; 95% CI, 0.131-0.230), preoperative sulfonylurea use (RYGB: OR, 0.616; 95% CI, 0.505-0.752 and AGB: OR, 0.449; 95% CI, 0.357-0.566), and other antidiabetic medication use (RYGB: OR, 0.747; 95% CI, 0.568-0.981 and AGB: OR, 0.506; 95% CI, 0.359-0.715) were significantly associated with response after both procedures. For remission of hypertension, age (RYGB: OR, 0.964; 95% CI, 0.957-0.972 and AGB: OR, 0.968; 95% CI, 0.959-0.977), number of preoperative antihypertensive medications (RYGB: OR, 0.104; 95% CI, 0.067-0.161 and AGB: OR, 0.239; 95% CI, 0.140-0.408), and preoperative diuretic use (RYGB: OR, 1.729; 95% CI, 1.462-2.045 and AGB: OR, 1.648; 95% CI, 1.380-1.967) were significantly associated with response after both procedures. CONCLUSIONS AND RELEVANCE: Analysis of a large, representative administrative database confirmed established predictors and revealed novel variables associated with comorbidity remission after bariatric surgery. Incorporating these factors into clinical tools to assess an individual patient's risk-to-benefit profile for these procedures could enhance patient selection and the overall use of surgery for the treatment of obesity and metabolic disease.

Gastric plication: preclinical study of durability of serosa-to-serosa apposition.

BACKGROUND: Vertical gastric plication is a novel surgical approach for reducing the stomach capacity. Anterior surface plication and greater curvature plication are variations of vertical gastric plication that reduce the gastric capacity through infolding of the anterior surface or greater curvature of the stomach, respectively. These approaches have been tested, with positive results in a small number of preclinical and clinical trials. A key step toward greater investigation of vertical gastric plication as a viable bariatric procedure would be confirmation that the apposed serosal tissues can be securely and durably bonded. We compared the short-term durability of gastric plications and serosal bonds using a variety of fastening devices and techniques in a university hospital and private company setting. METHODS: A total of 30 anterior surface plication and 8 greater curvature plication procedures were performed using an open or a laparoscopic surgical technique in 38 hound dogs. The fastening devices used were T-tags, buttressed T-tags, 2 types of suture, and 4 types of staple-based fasteners. The density of the fastening devices was varied among the dogs. With 3 exceptions (2 in keeping with the study design and 1 due to complications), the dogs were followed up for 8 weeks. Histologic examinations and tensile testing were performed postmortem. RESULTS: All fastening devices created durable plication folds, except for 1 technique. The only technique that did not produce durable serosa-to-serosa adhesions was a staple/suture combination. Intentional abrasion of the apposed sites had no demonstrable effect on the bonds between the tissues in any group. Increasing the fastener density and number of rows increased the adhesions within the folds. CONCLUSION: Our findings have confirmed the short-term durability and development of dense fibrous appositions of the serosal folds for fastening approaches that create fixed serosal apposition. Additional studies are needed to identify the optimal fastening modality for anterior surface plication, greater curvature plication, and, ultimately, clinical applications of this procedure.

Laparoscopic gastric plication for treatment of severe obesity.

BACKGROUND: Current gastric restrictive procedures include either a prosthetic device or gastric resection. We present the results of a feasibility study using laparoscopic gastric plication for weight loss achieved without stapling or banding. METHODS: After institutional review board approval, 2 methods were used to achieve laparoscopic gastric volume reduction. In the first group (anterior plication [AP]), the anterior gastric wall was folded inward from the fundus to the antrum using 2 rows of running sutures. The greater and lesser curvatures were approximated to create an intraluminal fold of the stomach. In the second group (greater curvature plication [GCP]), the short gastric vessels were divided, and the greater curvature was folded inward, with 2 suture lines to reduce the gastric capacity by a large intraluminal gastric fold. RESULTS: The average preoperative body mass index was 43.3 kg/m(2) (range 36.9-49.0), and 3 patients were men. Of the 15 patients, 9 underwent AP. For the 9 patients who underwent AP, the 6- and 12-month endoscopic evaluations demonstrated comparable-size plications over time, except for in 1 patient, who had a partially disrupted fold. Of the 6 patients who underwent GCP, the 6- and 12-month follow-up endoscopic examinations demonstrated a durable intraluminal fold, except for in 1 patient, with a partial disruption at the distal fold owing to a broken suture. For patients completing 1 year of follow-up, the percentage of excess weight loss was 23.3% ± 24.8% in the AP group (n = 5) and 53.4% ± 22.7% in the GCP group (n = 6). No bleeding or infectious complications developed. The first patient in the GCP group required reoperation and plication reduction owing to gastric obstruction. CONCLUSION: Our initial experience has suggested that a reduction in gastric capacity can be achieved by way of plication of the anterior stomach and greater curvature. The early weight loss results have been encouraging, with better weight loss in patients who underwent GCP. The use of laparoscopic GCP warrants additional investigation as a primary bariatric procedure.