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.

Improving Performance and Access to Difficult-to-Reach Anatomy with a Powered Articulating Stapler.

Background: Modern surgical staplers should provide precise placement and transection, especially in tight spaces and on thick tissue. Ideally, a stapler would move to accommodate variations in the tissue and anatomy instead of having to move the tissue around to fit the stapler. This study was undertaken to evaluate the performance characteristics of the new Echelon 3000 Stapler (ECH3). Use of the ECH3 was compared to another marketed stapler, including tests for access, seal strength, staple formation in thick tissue, and end effector stability. Methods: Pelvic anatomy measurements were used to construct a virtual model of a Low Anterior Resection (LAR). Monte Carlo simulations were performed on the staplers to compare the probability of completing a transection with one or two firings. Using water infusion of stapled porcine ileum, pressure at first leak and percentage of leaks at critical pressures were measured. Rate of malformed staples was measured in thick tissue. End effector stability while firing and under moderate pressure were compared between staplers. After use, surgeons were surveyed on the functionality of the device. Results: ECH3 had a markedly higher probability of completing an LAR transection in one or two firings than the comparator stapler. Median initial leak pressure of stapled ileum was significantly higher, and rate of leaks was lower at 40 and 50 mmHg. ECH3 had fewer malformed staples for both 3.3- and 4.0-mm thick tissue. The end effector exhibited less angular movement during firing, and less deflection under a moderate load. Surgeons agreed the ECH3 provided precise placement and easy one-handed operation. Conclusion: The Echelon 3000 Stapler demonstrated improved access capability, tighter seals, fewer malformed staples, and greater end effector stability. These advantages were recognized by surgeons who evaluated the use of the device preclinically.

Economic Analysis of Leak Complications in Anastomoses Performed with Powered versus Manual Circular Staplers in Left-Sided Colorectal Resections: A US-Based Cost Analysis.

PURPOSE: To estimate the cost impact of using the ECHELON CIRCULAR™ Powered Stapler (ECP) compared with manual circular staplers (standard of care, SOC) among patients undergoing colectomy procedures that involve left-sided anastomosis. METHODS: A US hospital-based budget impact model was developed to estimate the impact of ECP in reducing the surgical complication of anastomotic leak. The incremental acquisition cost of ECP vs SOC was compared to the net potential savings from reduced complication costs. The model was based on complication rates from a recently published matching-adjusted indirect comparison (MAIC) that compared clinical and healthcare utilization outcomes of patients using ECP with those of a propensity score-matched retrospective SOC control cohort from a real-world clinical practice population. The model assessed total cost, average length of stay (LOS), proportion of patients with a non-home discharge, and all-cause readmission. Deterministic (DSA) and probabilistic sensitivity analyses (PSA) were conducted to evaluate the robustness of the model assumptions and inputs. RESULTS: Despite a higher device cost of $412 for ECP compared with $298 for a manual stapler, annual savings due to avoided complications with ECP was $53,987 for anastomotic leak, assuming 100 procedures per year with each type of circular stapler. ECP also helped to avoid 27 LOS days, 0.38 readmissions and 0.22 non-home discharges. Sensitivity analyses around potential drivers of costs established the robustness of economic savings with the use of ECP - with annual savings being most impacted by the probability of anastomotic leak complication in the DSA. CONCLUSION: This model demonstrates that among patients undergoing left-sided colectomy procedures, the incremental cost of using the ECHELON CIRCULAR™ Powered Stapler instead of a manual circular stapler was offset by the savings from lowered incidence and cost of management of anastomotic leaks in the hospital setting.