Influence of a single locking throw on the in vitro holding security of five friction throws

OBJECTIVE

To compare the in vitro security of four different friction throws (square, surgeon's, Miller's, and strangle), with and without a locking throw, and a slip knot, on a vascular ligation model.

STUDY DESIGN

Experimental study.

SAMPLE POPULATION

Nine groups with nine samples per group.

METHODS

Four throws (square, surgeon's, Miller's, and strangle), with and without a locking throw, and a square throw locked in slip knot fashion, were tested to measure leakage pressure.

RESULTS

The square and surgeon's throws leaked at a lower pressure than the Miller's and strangle throws (p < .0001). The leakage pressure was below physiologic arterial pressure for the square and the surgeon's throws. After the addition of a locking throw, the five knots leaked at a similar pressure (p = .5233) above physiologic arterial pressure.

CONCLUSION

Following the addition of a locking throw, all the constructs tested in this study leaked at a similar pressure. The leakage pressure for all knots exceeded physiologic arterial pressures.

CLINICAL SIGNIFICANCE

Any throw tested may be appropriate for secure vascular ligation if the initial throw is applied correctly.

In vitro holding security of four friction knots of monofilament or multifilament suture used as a first throw for vascular ligation

OBJECTIVE

To evaluate holding security of 4 friction knots created with various monofilament and multifilament sutures in a vascular ligation model.

SAMPLE

280 friction knot constructs.

PROCEDURES

10 friction knots of 4 types (surgeon's throw, Miller knot, Ashley modification of the Miller knot, and strangle knot) created with 2-0 monofilament (polyglyconate, polydioxanone, poliglecaprone-25, and glycomer-631) and braided multifilament (silk, lactomer, and polyglactin-910) sutures were separately tied on a mock pedicle and pressure tested to the point of leakage. Linear regression analysis was performed to compare leakage pressures among suture materials (within friction knot type) and among knot types (within suture material).

RESULTS

Mean leakage pressure of surgeon's throws was significantly lower than that of all other knots tested, regardless of the suture material used. All the other knots had mean leakage pressures considered supraphysiological. Significant differences in mean leakage pressure were detected between various friction knots tied with the same type of suture and various suture types used to create a given knot. Variability in leakage pressure among knots other than the surgeon's throw was greatest for poliglecaprone-25 and lowest for polydioxanone.

CONCLUSIONS AND CLINICAL RELEVANCE

Most differences in knot security, although statistically significant, may not have been clinically relevant. However, results of these in vitro tests suggested the surgeon's throw should be avoided as a first throw for pedicle ligation and that poliglecaprone-25 may be more prone to friction knot slippage than the other suture materials evaluated.

Retention of basic suturing skills with brief or extended practice in veterinary students

OBJECTIVE

To evaluate the effect of practice duration on accuracy, retention, and confidence when learning how to tie basic surgical knots.

STUDY DESIGN

Prospective study.

SAMPLE POPULATION

Fifteen first-year veterinary students.

METHODS

Students were randomly assigned to a 2-week practice (TWP) or an 8-week practice (EWP) to learn how to tie surgeon's, strangle, and miller's knots. Students' knot-tying accuracy and confidence were evaluated immediately after training, at an intermediate time point (2-6 weeks postpractice), and at 12 weeks postpractice.

RESULTS

Students who had been trained during an extended period tied the strangle knot correctly more often at all assessments (P = .025). The ability of students trained for 2 weeks to tie the strangle knot correctly decreased over time (P = .028). These students lost some confidence (P = .03) and repositioned suture more frequently (P = .03) while constructing the strangle knot at the final time point compared with students trained for 8 weeks. Students who completed TWP felt more confident at placing surgeon's knots than friction knots at the final assessment period (P = .0164 miller's knot, P = .0056 strangle knot), whereas confidence did not differ between knot types for students who completed EWP. All students felt less confident with their knot-tying skills at 12 weeks postpractice.

CONCLUSION

Training for 8 weeks rather than for 2 weeks resulted in superior knot tying skills. Students' confidence decreased 12 weeks after training.

CLINICAL SIGNIFICANCE

Prolonged distributed practice is recommended to train students for more complex tasks such as placement of a strangle knot.

Evaluation of three ligatures in simulated equine open castration

OBJECTIVE

To compare three surgical knots for preventing leakage from the vascular bundle during ligation in simulated equine open castrations.

STUDY DESIGN

Randomized, case-control, in vitro study.

SAMPLE POPULATION

Testes (N = 60) collected from 30 horses.

METHODS

Testes were collected from 30 horses and randomly assigned to one of three groups: group G (friction, giant knot), group T (modified transfixing knot), or group S (sliding, strangle knot; n = 20/group). The assigned knot was used to ligate the vascular bundle during open castration. The length of suture material used and the leak pressure of the testicular artery were measured and compared between groups.

RESULTS

Strangle knots consistently leaked at higher pressures (median, 735.5 mm Hg; interquartile range [IQR], 735.5-735.5) compared with giant (median, 441.3 mm Hg; IQR, 367.8-643.6) and transfixing (median, 419.2 mm Hg; IQR, 323.6-643.6; P < .0001) knots. Both the strangle (median, 5 cm; IQR, 4.5-5.5) and giant (median, 6 cm; IQR, 5.35-6.075) knots required less suture material compared with the transfixing (median, 9.2 cm; IQR, 8.425-10.38; P < .0001) knot.

CONCLUSION

The three surgical knots tested withstood pressure well above physiological levels in simulated open castrations. The strangle knot withstood higher pressure and required similar (giant) or less (transfixing) suture material than the other two knots.

CLINICAL SIGNIFICANCE

This study provides evidence to support the use of a strangle knot to ligate the vascular bundle during simulated open castrations in horses.