Roeder Knot Research Articles

Transcystic biliary decompression after direct laparoscopic exploration of the common bile duct.

A purpose-designed transcystic common bile duct (CBD) decompression cannula is described for use as an alternative to T-tube insertion following laparoscopic direct CBD exploration. This permits safe primary closure of the choledochotomy. Following direct supraduodenal laparoscopic clearance of large common bile duct stones, the biliary decompression cannula is inserted percutaneously inside its peel-away sheet over a guide-wire into the CBD via the cystic duct. When in place, the cannula is secured to the cystic duct by two catgut extracorporeal Roeder knots and the choledochotomy is then closed. The terminal multiperforated S-shaped segment of the Cuschieri biliary decompression cannula prevents postoperative dislodgement. Transcystic decompression of the extrahepatic biliary tract using the Cuschieri cannula has been used in 12 patients who underwent laparoscopic supraduodenal CBD exploration for large or occluding stones. There was no instance of postoperative dislodgement of the cannula and all patients had effective drainage of the common bile duct (average 300 ml bile per 24 h). The procedure was uncomplicated in all but one patient who developed self-limiting leakage from the CBD suture line in the early postoperative period. The median hospital stay after surgery was 4 days, with a range of 3 to 10 days. The cystic duct decompression cannula was capped and sealed under an occlusive dressing at the time of discharge. Removal of the cannula was carried out without any complications as a day case 11-16 days after surgery. Transcystic biliary decompression is safe and effective. The experience with is use indicates that compared to T-tube drainage, transcystic decompression may accelerate recovery and reduce the hospital stay in patients following laparoscopic direct exploration of the CBD. Its insertion is less technically demanding than placing a T-tube through the choledochotomy. Transcystic decompression with complete primary closure of the CBD realizes the full benefits of the single-stage management of common bile duct calculi and permits confirmation of complete stone clearance after surgery.

The effect of knot geometry on the strength of laparoscopic slip knots

To evaluate and compare the strength of six different knot geometries used in laparoscopic slip knots. The strength of six extracorporeal slip knots used in laparoscopic surgery was measured using a tensiometer. Two multiple-throw laparoscopic square knots (the intracorporeal two-turn flat square knot and the extracorporeal sliding square knot) were used as controls. Each knot type was tied five times, and each type was tied in random order by the same primary and assisting surgeons using a laparoscopic pelvic surgery training model. One-way analysis of variance was performed to detect significant differences in knot strengths, and the variability in knot strength for each knot type was determined by Tukey's multiple comparison test. A statistically significant effect for knot geometry was identified. The mean knot strengths +/- standard deviation (SD), measured in newtons, from strongest to weakest, were: 4S knot (28.01 +/- 11.45), fisherman's knot (22.45 +/- 6.89), modified Roeder knot (19.86 +/- 9.30), Roeder knot (15.77 +/- 7.02), Weston knot (7.28 +/- 7.96), and Duncan knot (6.55 +/- 0.95). The mean knot strengths for the multiple-throw control square knots were as follows: intracorporeal two-turn flat square knot (41.21 +/- 2.69) and extracorporeal sliding square knot (27.81 +/- 16.27). The intracorporeal two-turn flat square knot (control) was significantly stronger (P < .05) than all slip knots except the 4S and fisherman's knot. The 4S and fisherman's knots are the strongest laparoscopic slip knots and are the only slip knots similar in strength to multiple-throw square knots.

The effect of knot geometry on the strength of laparoscopic slipknots

We evaluated and compared the strength of six extracorporeal slipknots used in laparoscopic surgery as measured with a tensiometer. Two multiple-throw laparoscopic square knots (intracorporeal two-turn flat square knot and extracorporeal sliding square knot) were used as controls. Each knot type was tied five times, and each type tied in random order by the same primary and assisting surgeons using a laparoscopic pelvic surgery training model. A one-way analysis of variance was performed to detect significant differences in knot strengths. The variability in strength for each knot type was determined using Tukey's multiple comparison test. A significant main effect for knot geometry was discovered (p <0.001). The mean knot strengths, measured in Newtons from strongest to weakest, were 4S knot 28.01 &plusmn; 11.45, fisherman's knot 22.45 &plusmn; 6.89, modified Roeder knot 19.86 &plusmn; 9.30, Roeder knot 15.77 &plusmn; 7.02, Weston knot 7.28 &plusmn; 7.96, and Duncan knot 6.55 &plusmn; 0.95. The mean knot strengths for the multiple-throw control square knots were intracorporeal two-turn flat square knot 41.21 &plusmn; 2.69 and extracorporeal sliding square knot 27.81 &plusmn; 16.27. The intracorporeal two-turn flat square knot (control) was significantly stronger (p <0.05) than all slipknots except the 4S and fisherman's knot. These are the strongest laparoscopic slipknots and are the only slipknots that compare in strength with multiple-throw square knots.

A simple modification to add strength to the Roeder knot

The Roeder knot is commonly used duing laparoscopic suturing because it may be tied extracorporeally and slid down to the target tissue with a single pass of a knot pusher. However, it is significantly weaker than extracorporeally tied knots with several throws. We compared the usual Roeder knot to one that was modified by adding a fourth loop around the standing end of the suture and a second half-hitch to the completed knot. The modified knot (26.6 newtons ±15.3) was significantly stronger (p<0.05) than the standard Roeder knot (18.0 newtons ± 12.1). If a single-pass extracorporeal knot is to be used, we recommend a modified Roeder knot when ligating pedicles at laparoscopy.

Comparative study of the holding strength of slipknots using absorbable and nonabsorbable ligature materials

The holding and tensile characteristics of five extracorporeal slipknots in relation to absorbable and nonabsorbable ligature materials have been evaluated in a standardized in vitro test rig. The knots studied: Tayside, Roeder, Melzer (modified Roeder), Cross square, and Blood knots were tied with the following materials: silk, polyamide, Dacron, polydioxanone (PDS), and lactomer (Polysorb). Following construction and slippage (run down) to a fixed-diameter loop around a cylinder, the knots were locked (tightened) using a standardized force after which they were removed from the test rig and subjected to holding strength (force required to induce reverse slippage) and other tensile characteristics (stress, strain, elasticity) by a tensiometer. Analysis of the data has demonstrated the following: (1) The safest slip knots (resist slippage) are the Tayside, Melzer, and Roeder knots tied with lactomer and Dacron. (2) The holding strengths of the Cross square and Blood knots are weak with all ligature materials tested. (3) Polydioxanone is a safe ligature material for the Melzer and Tayside but not the Roeder knot. (4) Extracorporeal slipknots tied with silk and polyamide are less secure than the equivalent knots tied with Dacron, lactomer, and polydioxanone.

Safety of Vessel Ligation in Laparoscopic Surgery

Laparoscopic ligaturing entails the use of the Roeder knot which is fashioned outside the abdomen, slipped along the ligature to the intended site and locked in place. The safety of the one-way Roeder slip knot in securing blood vessels and the tension a vessel ligature has to withstand were investigated ex vivo. Ligature tension was measured using perfused blood vessels in a test rig. From these data the ligature tension exerted by vessels up to 3 mm diameter at 150 mm Hg pressure was observed to be less than 5 grams. The relationship between ligature tension (T) and intravascular pressure (p), radius of the vessel (r) and radius of the vessel at the point of ligature (delta) is expressed by the formula: T = 3/2 pr delta. A good correlation between values for ligature tension derived from this formula and those observed in the test rig confirmed the validity of this equation for the calculation of approximate ligature tension. Catgut sutures tied with Roeder knots were subjected to strain gauge distraction under different conditions. The tension required to induce reverse slipping of the Roeder knot fashioned from 0/chromic catgut had a median value of 1125 (225-2700) grams weight. Thus in laparoscopic surgery the Roeder knot with dry chromic catgut has a substantial safety factor ratio of 55:1 in ligation of vessels up to 3 mm diameter.