Looped suture properties: implications for multistranded flexor tendon repair

Flexible PBAT-Based Composite Filaments for Tunable FDM 3D Printing

Biobased composites with peculiar properties offer an attractive route for producing environmentally friendly materials. The reinforcement for poly(butylene adipate-co-terephthalate) (PBAT), based on zein-titanium dioxide (TiO₂) complex (ZTC) microparticles, is presented and used to produce composite filaments, successfully 3-dimensionally (3D) printed by fused deposition modeling (FDM). The outcome of ZTC addition, ranging from 5 to 40 wt %, on the thermo-mechanical properties of composite materials was analyzed. Results reveal that storage modulus increased with increasing the ZTC content, leading to a slight increase in the glass transition temperature. The creep compliance varies with the ZTC concentration, denoting a better resistance to deformation under constant stress conditions for composites with higher complex content. Scanning electron microscopy was used to assess the quality of interphase adhesion between PBAT and ZTC, showing good dispersion and distribution of complex microparticles in the polymer matrix. Infrared spectroscopy confirmed the formation of a valid interface due to the formation of hydrogen bonds between filler and polymer matrix. Preliminary tests on the biocompatibility of these materials were also performed, showing no cytotoxic effects on cell viability. Finally, the 3D printability of biobased composites was demonstrated by realizing complex structures with a commercial FDM printer.

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

PURPOSE

This study aims to assess the biomechanical performance of different tying techniques of a double-stranded looped suture (DSLS).

METHODS

Loop and knot security of DSLS tying techniques (nice knot (NK), modified nice knot (MNK), double-twist knot (DTK), and double-barrel knot (DBK)) were compared. The square knot of DSLS (SKD) and the square knot of single-stranded suture (SKS) had been used as references. Twenty-four loops of each configuration were created using No. 2 Fiberwire (Arthrex, Naples, Florida, USA) and tested with a material testing machine. Samples were loaded with 10 N preloads for loop security assessment. Knot security was subsequently evaluated. Twelve loops of each knot were loaded to failure. The rest were subjected to cyclic load testing and the elongation at the 50th and 1000th cycles were measured. Knot bulkiness was determined by measuring knot height before testing. Data were compared with analysis of variance and post hoc tests. Statistical significance was p < 0.05.

RESULTS

All knots showed no statistically significant difference in displacement with preload. The load-to-failure was highest in NK, followed by MNK, DTK, DBK, SKD, and SKS. The cyclic loading test at the 50th cycle and the 1000th cycle demonstrated that NK has significantly less displacement than the others except MNK. DTK provided a minimal average knot height followed by NK, SKS, DBK, MNK, and SKD.

CONCLUSION

The different tying techniques in DSLS provided the similar loop security but different knot security and knot bulkiness. NK and MNK are biomechanically superior to the other knots, whereas DTK is the least bulky. The findings in the present study may help set the guide for the surgeons to select the tying technique of DSLS to best suit their requirement.

Biomechanical comparison of the Lim/Tsai tendon repair with a modified method using a single looped suture

The Lim/Tsai tendon repair technique has been modified clinically to achieve a 6-strand repair using a single looped suture with one extratendinous knot. We compared biomechanical performance of the original and modified methods using 20 porcine flexor digitorum profundus tendons. The ultimate tensile strength, load to 2 mm gap force, mode of failure, and time taken to repair each tendon were recorded during a single cycle loading test in 10 tendons with each repair method. We found that despite having the same number of core strands, the single looped suture modified Lim/Tsai technique possessed significantly greater ultimate tensile strength and load to 2 mm gap force. Also, less repair time was required. We conclude that the modified 6-strand repair using a single looped suture has better mechanical performance than the original method. The difference likely was due to the changes in locations of the knots and subsequent load distribution during tendon loading.

Outcomes of the six-strand M-Tang repair for zone 2 primary flexor tendon repair in 54 fingers

We repaired complete divisions of flexor tendons in zone 2 in 54 fingers using a six-strand core M-Tang repair method. Partial active digital motion started with early passive digital motion carried out first in the first 3-4 weeks after surgery and full range of active motion in later weeks. The patients were followed for 4-27 months. According to Strickland criteria or Tang criteria, 24 (83%) had excellent or good, four fair and one poor results in 28 fingers with follow-up of more than one year. In the other 25 fingers which were followed for less than 12 months, 19 (76%) had excellent and good, four fair and two poor results. There were no repair ruptures. We analysed outcomes against ages, gender, pulley integrity, accompanied injuries and follow-up times. The patients younger than 37 years old, male patients and with their A2 pulley(s) vented there were significantly better outcomes. The patients with longer than one year follow-up had significantly smaller extension deficits than those with less than one year follow-up.

LEVEL OF EVIDENCE

IV.

Biomechanical investigation of uneven load bearing in six-strand Lim-Tsai flexor tendon repair using FiberLoop®

We hypothesized that, in providing biomechanical strength, at least one of the two middle strands in a modified six-strand Lim-Tsai flexor tendon repair could be divided without obvious reduction in repair strength owing to uneven load bearing. A total of 40 porcine flexor digitorum profundus tendons were repaired using the six-strand Lim-Tsai technique with a 4-0 FiberLoop^® suture and then divided into four equal groups. (no cut, one middle strand cut, both middle strand cut, one side strand cut). The biomechanical performance of repaired tendons was tested and found to vary according to the location of the cuts.

Effect of the Optimal Asymmetry on the Strength of Six-Strand Tendon Repair: An Ex Vivo Biomechanical Study

PURPOSE

To evaluate the mechanical properties of a 6-strand core suture repair with asymmetric purchase in the 2 tendon ends, in comparison with a repair with symmetric suture purchases.

METHODS

Under cyclic loading of the tendons, we recorded the fatigue strength (Forces × Cycles) of a 6-strand flexor tendon repair with different symmetry in the lengths of suture purchase in 60 porcine tendons. The symmetric repair was made with 3 groups of parallel Kessler repairs of equal suture purchase (10 mm from the cut end) in the 2 tendon stumps. The asymmetric core suture repairs were then made with a Kessler repair of equal suture purchase (10 mm from the cut end) in the 2 tendon stumps, and shifting 2 other Kessler repairs by 1, 2, 3, 4, or 5 mm, respectively, along the longitudinal axis of the tendon in relation to the first (symmetric) Kessler repair.

RESULTS

The core repairs with 2 mm or more asymmetry in suture purchases in 2 tendon ends showed significantly greater fatigue strength compared with those with symmetric suture placement. The core repairs with 3 mm or more asymmetry in suture purchases in 2 tendon ends showed significantly smaller gaps compared with those with symmetric suture placement.

CONCLUSIONS

The core repairs with 3 mm or more asymmetry in suture purchases in 2 tendon ends generated increased fatigue strength and reduced gap sizes compared with those with symmetric suture placement in an ex vivo porcine model.

CLINICAL RELEVANCE

An asymmetric core suture repair with 3 mm or more difference in purchase length may allow for earlier rehabilitation and reduce the risk of postoperative complications.

Biomechanical investigation of 'figure of 8' flexor tendon repair techniques

This biomechanical study compared the original Al-Qattan repair with other modifications postulated to reduce bulk and friction, thereby potentially improving outcome. A total of 32 cadaveric digits with intact flexor apparatus were used. In each digit, the flexor digitorum profundus and flexor digitorum superficialis tendons were cut cleanly in Zone 2. We tested Al-Qattan's technique along with three modifications using stronger suture material and varying the number of strands across the repair site. Of the four repair techniques, the modified Al-Qattan's technique using two 'figure of 8' 4-0 Fiberwire core sutures (Group 4) had the best balance of ultimate tensile strength (50.9 N), 2 mm gapping force (38 N) and friction. The modified technique provided a stronger repair for early active mobilization and has less friction than the originally described repair.