Biomechanical analysis of flexor tendon repair using knotted Kessler and Bunnell techniques and the knotless Bunnell technique

Biomechanical comparison of different suture materials with different techniques in tendon repair: An ex-vivo study

OBJECTIVES

Sheep Achilles tendons are used as an effective preclinical model of flexor tendon repair in plastic surgery, due to their biomechanical properties, which are similar to humans. The aim of this study was to examine the efficacy and biomechanical outcomes of suture materials and tendon repair techniques in flexor tendon repair.

MATERIAL AND METHODS

72 sheep tendons were obtained for a total of 12 different scenarios. Tendons were repaired using 4 different suture types and 3 different suture techniques. After repair, the tendons were fixed at both ends and subjected to biomechanical tests. Ultimate Failure Load (UFL) and 2-mm Gap Load (GL) per scenario were compared statistically within and between groups.

RESULTS

UFL and GL of all sutures were significantly different between the modified Kessler, Bunnell and Krackow techniques (P < 0.05), and between Monosorb, Ti-Cron and V-loc sutures (P < 0.05). UFL and GL according to repair technique were not significantly different for the Propilen suture (P > 0.05).

CONCLUSION

When UFL and GL were considered together, our findings indicate that optimal strength scenarios were for the modified Kessler technique using Monosorb or V-loc sutures.

Effect of loading speed on gap resistance and tensile strength of flexor tendon repair under cyclic loading test

Postoperative digit motion is important for the functional recovery of injured tendons. To date, it is unknown whether the loading speed impacts the biomechanical properties of a repaired tendon. This study investigated the effect of loading speed on the gap resistance and tensile strength of tendon repairs. One hundred porcine flexor tendons were repaired with two core sutures, 4-strand modified Kessler and double Q, and cyclically loaded at the speeds of 10, 40, 80, 160, and 320 mm/min. The number of tendons that formed an initial or 2 mm gap at the repair site during cyclic loading, stiffness at the 1st and 20th loading cycles, gap size between tendon ends when cyclic loading ended, and the ultimate strength were recorded. Under the lowest loading speed, the tendons repaired with the 4-strand modified Kessler suture developed significantly larger gaps and smaller stiffness than those with a greater loading speed. The loading speed did not affect the maximum strength of both tendon repairs. The findings suggest that very slow motion promotes gap formation of tendon repair with inferior gap resistance. The rate corresponds to regular hand action or the tendon core suture possessing a strong gap resistance increases the safety margin during early active finger movement. Our findings help to guide the exercise regimens after tendon surgery.

Krackow Stitch and Whipstitch Use in Distal Biceps Tendon Rupture Repair: A Porcine Composite Bone Biomechanical Study

The suture combination of a Krackow stitch plus a whipstitch can be used to strengthen a tendon rupture repair. We compared biomechanical outcomes of suture repair techniques for distal biceps tendon ruptures using a single Krackow stitch with and without a whipstitch and a whip-stitch alone. Data were obtained from 36 thawed porcine flexor profundus tendons. A cortical button was secured to fourth-generation composite bone using No. 2 FiberWire (Arthrex) and No. 2 FiberLoop (Arthrex). The primary outcome was maximum load to failure. Secondary outcomes were displacement at the bone-tendon interface, total construct elongation, and stiffness. The Krackow plus whipstitch group (mean, 493.82 N; SD, 209.44 N) had a greater maximum load to failure as compared with the single Krackow group (mean, 333.71 N; SD, 172.32 N) (P=.01) and single whipstitch group (mean, 207.27 N; SD, 66.42 N) (P<.001). The single Krackow group (mean, 1.67 mm; SD, 0.89 mm) had a greater bone-tendon interface displacement (P=.01) after preloading and before cyclic loading than the single whipstitch group (mean, 0.83 mm; SD, 0.58 mm). There were no other secondary outcome differences between groups. A repair using Krackow plus whipstitch is biomechanically stronger with no difference in bone-tendon interface displacement, total construct elongation, or stiffness when compared with a single Krackow or single whipstitch. We recommend this repair technique for distal biceps tendon rupture repair, which may accelerate rehabilitation and decrease re-rupture rate. [Orthopedics. 2023;46(4):224-229.].

A review of cyclic testing protocols for flexor tendon repairs

BACKGROUND

Cyclic testing of flexor tendons aims to simulate post-operative rehabilitation and is more rigorous than static testing. However, there are many different protocols, making comparisons difficult. We reviewed these protocols and suggested two protocols that simulate passive and active mobilization.

METHODS

Literature search was performed to look for cyclic testing protocols used to evaluate flexor tendon repairs. Preload, cyclic load, number of cycles, frequency and displacement rate were categorised.

FINDINGS

Thirty-five studies with 42 different protocols were included. Thirty-one protocols were single-staged, while 11 protocols were multiple-staged. Twenty-nine out of 42 protocols used preload, ranging from 0.2 to 5 N. Preload of 2 N was used in most protocols. The cyclic load that was most commonly used was between 11 and 20 N. Cyclic load with increment of 10 N after each stage was used in multiple-staged protocols. The most commonly used number of cycles was between 100 and 1000. Most protocols used a frequency of <1 Hz and displacement rate between 0 and 20 mm/min.

INTERPRETATION

We propose two single-staged protocols as examples. Protocol 1: cyclic load of 15 N to simulate passive mobilization with preload of 2 N and 2000 cycles at frequency of 0.2 Hz.; Protocol 2: cyclic load of 38 N to simulate active mobilization, with the same preload, number of cycles, and frequency as above. This review consolidates the current understanding of cyclic testing and may help clinicians and investigators improve the design of flexor tendon repairs, allow for comparisons of different repairs using the same protocol, and evaluate flexor tendon repairs more rigorously before clinical applications.

Comparing Biomechanical Properties, Repair Times, and Value of Common Core Flexor Tendon Repairs

BACKGROUND

The aim of the study was to compare biomechanical strength, repair times, and repair values for zone II core flexor tendon repairs.

METHODS

A total of 75 fresh-frozen human cadaveric flexor tendons were harvested from the index through small finger and randomized into one of 5 repair groups: 4-stranded cross-stitch cruciate (4-0 polyester and 4-0 braided suture), 4-stranded double Pennington (2-0 knotless barbed suture), 4-stranded Pennington (4-0 double-stranded braided suture), and 6-stranded modified Lim-Tsai (4-0 looped braided suture). Repairs were measured in situ and their repair times were measured. Tendons were linearly loaded to failure and multiple biomechanical values were measured. The repair value was calculated based on operating room costs, repair times, and suture costs. Analysis of variance (ANOVA) and Tukey post hoc statistical analysis were used to compare repair data.

RESULTS

The braided cruciate was the strongest repair ( P > .05) but the slowest ( P > .05), and the 4-stranded Pennington using double-stranded suture was the fastest ( P > .05) to perform. The total repair value was the highest for braided cruciate ( P > .05) compared with all other repairs. Barbed suture did not outperform any repairs in any categories.

CONCLUSIONS

The braided cruciate was the strongest of the tested flexor tendon repairs. The 2-mm gapping and maximum load to failure for this repair approached similar historical strength of other 6- and 8-stranded repairs. In this study, suture cost was negligible in the overall repair cost and should be not a determining factor in choosing a repair.

Enhanced biological fixation of ligaments to bone tissues utilizing chitin fabrics

In ligament reconstruction involving anterior cruciate ligament surgery, biological fixation between the transferred ligament and bone tissue is critical for achieving successful outcomes. Here, we administered chitin fabrics into the bone tunnels and evaluated their efficacy in promoting biological fixation. An animal model on the rat's patellar ligament was employed. First, bone tunnels were created in the lateral condyle of the femur. The ligament was then separated from the tibial tuberosity, and half was inserted into the tunnel and fixed with the use of end button. Animals in the experimental group were treated with microfiber nonwoven chitin fabric, whereas control animals received no treatment. Specimens were collected at 2, 4, and 6 weeks after surgery, and the fixation strength was measured by mechanical tests. Histological sections were prepared from samples prepared 4 weeks after surgery, and the diameter of bone tunnel and the width ratio of collagenous tissue in the bone tunnel were measured. Administration of chitin significantly increased the mean fixation strength at 4 and 6 weeks after surgery. Furthermore, chitin also promoted bone formation in the bone tunnel and increased the density of collagen fibers. Thus, microfiber nonwoven chitin fabric enhanced the biological fixation of the ligament to the bone tissue. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 106B: 2355-2360, 2018.