A biomechanical comparison of different tying techniques of a double-stranded looped suture

Triple suture fixation for displaced comminuted olecranon fracture with a stable ulnohumeral joint

PURPOSE

To report the outcome of a novel fixation technique using three high-strength sutures which is including articular buttress suture, cerclage suture, and tension band with off-loading triceps suture (triple suture fixation) in the treatment of displaced comminuted olecranon fracture with a stable ulnohumeral joint (Mayo type IIB). The rationale of using this technique is that the sutures have been used to stabilize multiple fracture fragments in all sides of the olecranon.

MATERIAL AND METHODS

Between July 2018 and July 2021, 10 patients (7 women, 3 men; mean age, 49.9 years; mean follow-up duration, 27.8 months) with Mayo type IIB olecranon fractures who underwent triple suture fixation were included in the study. The elbow was immobilized in a splint for 2 weeks postoperatively. Range-of-motion exercises were initiated after splint removal and weight bearing was allowed at 6 weeks postoperatively.

RESULTS

Average active range of motion of the elbow was 145° of flexion (range, 135°-150°), 6.5° of extension (range, 0°-30°), 83° of supination (range, 70°-85°), and 77.5° of pronation (range, 70°-80°). Mean MEPS was 98.3 (range, 85-100) and DASH score was 3.1 (range, 0-10) at the final follow-up. Radiographic data at the final follow-up analyzed by paired t test demonstrated that there was no statistically significant difference of proximal olecranon height (OH), trochlear notch width (TW), and OH/TW ratio between postoperative treatment and normal side (p-value >.05). No complication of implant prominence, fixation failure, nonunion, infection or heterotopic ossification was found postoperatively. Breakage of drill bit occurred during drilling a distal oblique hole for articular buttress suture in one patient.

CONCLUSION

The triple suture fixation is an effective treatment with low incidence of complications in treatment of Mayo type IIB olecranon fractures. Larger comparative studies are needed to confirm the value of such technique.

Does quality of novice hand-tied square knots improve with repetition during a single training session?

Background

Knot tying is a key surgical skill for novices, and repetition over several training sessions improves knot tying. This study examined the effects of repetition within a single training session on quality of knotted loops and compared results of novice trainees and experienced surgeons.

Methods

Using 0.55 mm nylon monofilament fishing line, novices and surgeons each hand-tied 20 knotted loops, using a 2=1=1=1 configuration (surgeon's throw and three square throws). Loops were mechanically tested with a single load to failure.

Results

All loops tolerated five newtons (N) preload. More than 70% of novice and surgeon knots failed by slipping or untying, and 8.8% of novice knots and 2.5% of surgeon's knots were considered dangerous. Surgeons' loops had less extension at preload, indicating better loop security. However, during single test to failure, there was no difference in mean extension or maximum load between surgeons and novices. There was no significant difference in results of mechanical testing or modes of failure for the first and last ten knotted loops, or the first, second, third, and fourth sets of knotted loops.

Discussion

With appropriate training, novices can construct knots as strong and secure as experienced surgeons. A large percentage of knotted loops are insecure under testing conditions; extra throws may be required when using large diameter monofilament nylon. Novices may require extra training in maintenance of loop security when constructing square knots. Tying more than five or 10 knotted loops within a single training session does not provide added benefits for novices.

Does the Nice Knot Offer Less Elongation Than the Modified Prusik Knot? An In Vitro Study in Cadaver Quadriceps Tendons

BACKGROUND

ACL graft-suture fixation can be constructed with needle or needleless techniques. Needleless techniques have the advantage of decreased injury, preparation time, and cost. The Nice knot is common among upper extremity procedures, and has been shown to have higher load to failure and less elongation compared with other double loop knots; however, there are no studies that have looked at its use for ACL graft-suture construct to determine whether it offers less elongation relative to other needleless techniques.

QUESTIONS/PURPOSES

In a cadaver quadriceps tendon model, we asked: (1) Does the Nice knot have less elongation than the Prusik knot? (2) Does the Nice knot have increased peak load and stiffness compared with the Prusik knot? (3) What were the modes of failure of each knot?

METHODS

Sixteen quadriceps tendon grafts were harvested from 16 cadaver knee specimens. The median (range) age of the donors was 80 years (70 to 96) and included three male and five female donors. Eight grafts were prepared with the Prusik knot and eight with the Nice knot using a braided polyblend suture. The graft-suture constructs were mounted in a materials testing machine and subjected to a tensile loading protocol beginning with pretensioning of three cycles from 0 to 100 N at 1 Hz followed by a constant load of 50 N for 1 minute then cyclic loading of 200 cycles from 50 to 200 N at 1 Hz. The constructs were loaded to failure as the final step of the loading protocol. Elongations of the construct after each loading step, peak load, stiffness, and graft cross-sectional area were compared.

RESULTS

Construct elongations (median [IQR]) for the Nice knot were lower than that of the Prusik knot after pretensioning (4.4 mm [0.8] versus 5.7 mm [1.4]; p = 0.02), preloading (0.6 mm [0.3] versus 1.0 mm [0.3]; p = 0.005), and cyclic loading (7.4 mm [1.4] versus 10.9 mm [2.1]; p = 0.005). Peak load was not different for the Prusik knot construct compared with the Nice knot (334 N [43] versus 312 N [13]; p = 0.08). Stiffness of the Prusik knot construct (103 N/mm [17]) was no different than the Nice knot construct (110 N/mm [13]; p = 0.13). Graft cross-sectional area of the Prusik knot constructs (85 mm2 [35]) were similar to the grafts of the Nice knot constructs (97 mm2 [31]; p = 0.28). Failure mode of the constructs did not differ between groups; it was caused by suture rupture near the knots that secured the free suture ends to the machine and was seen in all 16 tests.

CONCLUSIONS

The results of this biomechanical study show that the Nice knot construct has similar or greater biomechanical properties compared with the Prusik knot in the graft suture construct, although the magnitude of the differences are not likely to the level of clinical importance.

CLINICAL RELEVANCE

The Nice knot offers an attractive alternative option for needleless ACL graft preparation technique. Future studies should consider comparison to established needle techniques such as Krackow or whipstitch and testing in an intraarticular component in an in vivo model.

Comparison of mechanical properties between Nice knot, Modified Nice knot, and surgeon's knot

BACKGROUND

The success of surgical repairs rely on the effectiveness and integrity of the surgical knots used to secure the repair. The purpose of this study is to examine and compare the performance of the Nice knot, the modified Nice knot, and a commonly used combination of surgeons' and square knots with respect to cyclic loading and load-to-failure usiflueng a high-strength suture composed of ultra-high molecular weight polyethylene in the hands of experienced surgeons.

METHODS

Two experienced surgeons threw 3 different knot types 9 times, consisting of the Nice knot, modified Nice knot, and a surgeon's knot utilizing Ultrabraid #2 sutures. Each knot was subject to cyclic loading and load to failure testing.

FINDINGS

Both surgeons had similar displacement data for the surgeon's knot, while the identity of the surgeon impacted displacement for the Nice knot (p = 0.03) and the modified Nice knot (p = 0.0002). The load to failure for the modified Nice knot (p < 0.001) and the Nice knot (p = 0.001) were significantly impacted by the surgeon tying the knot, while the surgeon's knot was not. Specimens failed where the sutures passed through the loop at the "base" of the knot.

INTERPRETATIONS

The strength and integrity of complex surgical knots are variable between surgeons. While the proposed Modified Nice Knot has a theoretical advantage because the half hitches reinforce the primary knot, in load to failure testing both the Modified Nice Knot and the Nice Knot failed where the suture passed through the loop in the primary knot.