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Thickness calibration device and LSG

Thickness calibration device would avoid leaks in LSG

They note that the suitability of a particular cartridge for a location depends on the tissue thickness at that location
The authors call for larger, multicentre studies to investigate the relationship between improper staple height and leak rate

A thickness calibration device is required in order to determine correct staple height and avoid leaks when performing laparoscopic sleeve gastrectomy (LSG), according a paper ‘A Thickness Calibration Device Is Needed to Determine Staple Height and Avoid Leaks in Laparoscopic Sleeve Gastrectomy’, published in Obesity Surgery, Drs Rose Huang (Boehringer Laboratories, Phoenixville, PA, USA) and Professor Michel Gagner (Hospital Du Sacre Coeur, Montreal, QC, Canada).

The authors begin by explaining that there are currently two methods of selecting a staple cartridge. The first is a singular method (using one type of staple cartridge (typically black) to create the entire sleeve), although this risks bleeding or leaking if the thickness of the stomach is outside the indicated range of the cartridge. In the second, ‘variable method’, the surgeon starts with the thickest load and then chooses subsequent staple loads based on how the tissues feel. However, due to the absence of an objective measurement, incorrect staple height can be taken and lead to incomplete staple formation, leakage or bleeding. As a result, the authors state that reported rates in the literature of 0-4.4% for leakage and 0.4-4% for haemorrhage using stapling devices.

Rose Huang

The authors explain that most leaks occur near the gastroesophageal junction and they hypothesised that it is the mismatch between staple height and tissue thickness that lead to leaks after LSG. Therefore, the aim of their study was to determine the range of gastric thicknesses in three areas of stapling and analyse the accuracy of techniques in selecting the appropriate staple cartridge.

Michel Gagner

In this single-centre, single-surgeon prospective study, LSG was performed with either a 40Fr bougie or a suction calibration system (ViSiGi 3D, Boehringer Labs) in alternating order. The researchers recorded each patient’s sex, age, BMI and comorbidities. Following the procedure, the double wall thickness of the excised gastric specimen was measured at three predetermined locations, namely the fundus (1cm caudal to the edge of the fundus, 0.5cm from the staple line), midbody (halfway between the fundus and the pylorus along the staple line, 0.5cm from the staple line) and antrum (2cm caudal to the pylorus along the staple line, 0.5cm from the staple line).

“This variation in cartridge suitability at the fundus underscores the need for surgeons to be certain of the tissue thickness before choosing a cartridge." 

The study used a thickness measuring apparatus (Mitutoyo QEZ767 No. 2050S; Mitutoyo), which was modified with a weight to achieve an applied pressure of 8g/mm2. After measuring the length of the staple line with a flexible ruler, the tissue thickness of each location was recorded after 15 seconds of compression.

In order to assess the suitability of each colour of staple cartridge at each predetermined anatomical location, information on closed staple height was referenced from two stapler manufacturers, Ethicon and Covidien. It was assumed that each colour of cartridge was able to cover a range of thicknesses between the data points of the preceding and following cartridges.

The researchers explained that “using the assumed range of thicknesses for each cartridge colour, a normal distribution graph was generated to determine the probability of using this colour at a particular anatomical location based on the measured mean thickness and standard deviation of that location.”

In total, 26 patients (15 female, 11 male; mean age 36.8 years (range 14–74 years)) were included in the study. The mean BMI was 45.3 (range 35.0– 61.0) overall, 44.7 (range 35.0–60.) for males, and 45.7 (range 39.0–61.0) for females. The length of the specimen was measured along the staple line in all patients and averaged 21.2cm (range 17.0–30.0cm). They report that gender was significantly correlated with the length of the stomach, and was significantly longer in males (22.9 m (range 19.0–30.0cm)) than in females (19.9cm (range 17.0–26.0 cm)) (p<0.001). They report that the stomach was thickest near the pyloric antrum and thinnest near the fundus, in both sexes (although there were five outlier cases that did not follow the general thickness profile).

Staple cartridge suitability

They note that the suitability of a particular cartridge for a location depends on the tissue thickness at that location. In this study, the surgeon used a black cartridge at the antrum of every patient. They report that the suitability of using the Covidien Tri-Staple black cartridge at the antrum for every female patient in this study was 16.55%. As the mean thickness of the antrum in females was much higher than that of the published closed staple height (3.09 vs. 2.25mm), the authors found that using the Covidien Tri-Staple  black cartridge at the antrum was appropriate in only one out of six female patients.

The same method was used in all other Covidien Tri-Staple colour cartridges at the midbody and fundus, They found that the most appropriate colour cartridge at the female midbody was black (39.51 %). The most appropriate choice of cartridge at the fundus could be either black or purple (55.23 and 57.13 %, respectively).

In the male patients, they report that the most appropriate cartridge colour at the antrum, midbody, and fundus were black (19.9 %), black (42.84 %), and purple (86.02 %), respectively.

“This variation in cartridge suitability at the fundus underscores the need for surgeons to be certain of the tissue thickness before choosing a cartridge,” they note.

In the analysis for the Ethicon Echelon Stapler, the appropriate colour cartridges at the antrum, midbody, and fundus of the female patients in the present study were black (10.59%), black (20.07%), and blue (23.99%), respectively. For the male patients, the appropriate colour cartridges at the antrum, midbody, and fundus were black (10.65 %), black (27.52 %), and blue (38.04 %).

“Overall, one stapler manufacturer is not superior to another,” the authors write. “Even though the suitability might be less than 20% at the antrum, the black cartridge is the thickest reload choice for both manufacturers on the current market. Stapler manufacturers should develop a cartridge that accommodates tissues that exceed the range of a black cartridge.”

The authors call for larger, multicentre studies to investigate the relationship between improper staple height and leak rate, adding that there is “no one-size-fits-all method for choosing the correct cartridge”. They claim that their study (and literature studies) show that there is insufficient evidence “to base recommendations for appropriate cartridges for a given tissue thickness on a single data point, and this discrepancy underscores the need for an objective means for measuring thickness.”

“There is a need for a laparoscopic tool that accurately and quantitatively measures the thickness of stomach tissue intraoperatively. A difference of less than 1mm in tissue thickness can be difficult to discern by touch but can make a difference in staple cartridge selection,” they conclude. “…A thickness measuring device would be a step toward standardizing surgical technique in laparoscopic SG…Selecting the correct staple height does not eliminate the risk of leaks, but the operating surgeon can take on an active role in leak prevention by reducing bleeding and tissue ischaemia.”    

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