The effect of suture preloading on the force to failure and gap formation after flexor tendon repair

Assessing the application of barbed sutures in comparison to conventional sutures for surgical applications: a global systematic review and meta-analysis of preclinical animal studies

BACKGROUND

Following an initiative published by Lancet in 2002 and an IDEAL-D framework, the value of preclinical animal studies has garnered increasing attention in recent research. Numerous preclinical animal experiments tried to generate evidence to guide the development of barbed sutures. However, discernible drawbacks and incongruities in outcomes have emerged between clinical and preclinical animal studies. Therefore, this meta-analysis aimed to review the preclinical animal experiments comparing barbed sutures with conventional sutures. The authors hope to facilitate clinical translation of barbed sutures by evaluating effectiveness, safety, and physical properties/reliability.

MATERIALS AND METHODS

A systematic search of PubMed, EMBASE, Cochrane Library, and ClinicalTrials.gov was conducted to identify controlled preclinical animal experiments comparing barbed sutures with conventional sutures. The risk of bias was assessed using SYRCLE. GRADE approach was used to evaluate evidence quality. Revman was applied to analyze all the data. Subgroup, sensitivity, and meta-regression analyses were also performed.

RESULTS

A total of 62 articles were eligible with low to moderate quality, including 2158 samples from 10 different animal species across 27 surgical procedures. Barbed suture exhibited a significant reduction in suture time, limited change in Cross-Sectional Area (CSA), and decreased instances of tissue disruption (all P <0.05). Subgroup analyses, considering both clinical and research significance, indicated that barbed sutures might cause more specific adverse events and demonstrate suboptimal performance of physical properties/reliability. Meta-regression suggested that heterogeneity resulted from variations in studies and animal models.

CONCLUSION

Although barbed suture demonstrated superiority in numerous surgeries for time efficiency, its safety and physical properties/reliability might be influenced by diverse preclinical models, sutures' brand, surgeries, and anatomical sites. Further evaluation, based on standardized and well-designed animal experiments, is essential for medical device development and applications in human beings.

Gap Resistance and Tensile Strength of a Q Suture Technique During Curved Loading: An Ex Vivo Porcine Flexor Tendon Study

PURPOSE

This study aimed to determine the mechanical properties of the double Q suture technique in angular motion and to compare the gap formation associated with tendon repairs during curved and linear loading.

METHODS

Eighty porcine flexor tendons were repaired with one of two 4-strand sutures: double Q suture or double modified Kessler plus peripheral running sutures. The repaired tendons were cyclically loaded sequentially against a pulley with a radius of 2.0, 1.5, and 1.0 cm or linearly without any pulleys. The number of tendons that formed an initial or 2-mm gap at the repair site during cyclic loading, the gap size between tendon ends when cyclic loading ended, and the ultimate strength were recorded.

RESULTS

The gap at the repair site formed gradually from the dorsal to volar aspect during curved loading. No double Q repairs, but half of the double Kessler plus running suture repairs, formed an initial or 2-mm gap on the volar aspect during curved loading. The double Q group had a significantly smaller gap size on the dorsal aspect than the double Kessler plus running suture group at all three radii of curvature. The ultimate strength was similar between the two groups. There were no significant differences in linear motion between these two repairs.

CONCLUSIONS

The double Q suture is superior to the conventional 4-strand tendon core suture plus running peripheral sutures in gap resistance in angular motion. This study provides insight into the formation of an unbalanced gap on the dorsal and volar aspects of tendon repair during curved loading.

CLINICAL RELEVANCE

The double Q suture provides a simple and efficient option for flexor tendon repair considering the high risk of gap formation on the dorsal aspects of the tendon repair in angular motion.

Strength, bulk and surgery time of ex situ versus in situ flexor tendon repair in a cadaveric model

The purpose of this study was to compare strength, bulk and time of repair of human cadaveric flexor digitorum profundus tendons repaired in situ versus ex situ. Ninety-six human cadaveric flexor digitorum profundus tendons were transected 5 mm distal to the A2-pulley and randomized to 2-strand, 4-strand or 6-strand repairs. We found no significant differences in repair strength between in situ and ex situ repairs, but repair strength increased with increasing number of strands. The cross-sectional area of the repair was not significantly related to the number of strands, but 4- and 6-strand in situ repairs were bulkier than ex situ repairs. In situ repair took longer, and repair time increased with increasing number of strands. We suggest that cadaveric studies of flexor tendon repair should be performed in situ in order to better mimic the clinical reality of tissue handling and repair bulkiness.

Risk factors associated with tendon adhesions after hand tendon repair

Background

Tendon adhesions after hand tendon repair are one of the most difficult complications of hand surgery and can cause severe disability. This study aimed to assess the risk factors associated with tendon adhesions after hand tendon repair to provide a theoretical foundation for the early prevention of tendon adhesions in patients with tendon injuries. Moreover, this study intends to increase doctors' awareness of the issue and serves as a reference for developing new prevention and treatment strategies.

Methods

We retrospectively analyzed 1,031 hand trauma cases that underwent repair after finger tendon injury in our department between June 2009 and June 2019. Tendon adhesions, tendon injury zones, and other relevant information were collected, summarized, and analyzed. The significance of data was determined using a t-test or Pearson's chi-square test, and odds ratios (OR) were calculated using logistic regression tests to describe factors associated with post-tendon repair adhesions.

Results

A total of 1,031 patients were enrolled in this study. There were 817 males and 214 females with an average age of 34.98 (2-82) years. The injured side included 530 left and 501 right hands. Postoperative finger tendon adhesions occurred in 118 cases (11.45%), including 98 males and 20 females, 57 left and 61 right hands. The risk factors for the total sample in the descending order were degloving injury, no functional exercise, zone II flexor tendon injury, time from injury to surgery >12 h, combined vascular injury, and multiple tendon injuries. The flexor tendon sample shared the same risk factors as the total sample. Risk factors for the extensor tendon sample were degloving injury, no functional exercise.

Conclusions

Clinicians should pay close attention to patients with tendon trauma in hand having the following risk factors: degloving injury, zone II flexor tendon injury, lack of functional exercise, time from injury to surgery >12 h, combined vascular injury, and multiple tendon injuries. Due to the high risk of post-repair adhesions in patients with the conditions mentioned above, individualized treatment measures should be designed for the risk factors, and postoperative functional exercise of the hand is required.

Characterization of scar tissue biomechanics during adult murine flexor tendon healing

Tendon injuries are very common and result in significant impairments in mobility and quality of life. During healing, tendons produce a scar at the injury site, characterized by abundant and disorganized extracellular matrix and by permanent deficits in mechanical integrity compared to healthy tendon. Although a significant amount of work has been done to understand the healing process of tendons and to develop potential therapeutics for tendon regeneration, there is still a significant gap in terms of assessing the direct effects of therapeutics on the functional and material quality specifically of the scar tissue, and thus, on the overall tendon healing process. In this study, we focused on characterizing the mechanical properties of only the scar tissue in flexor digitorum longus (FDL) tendons during the proliferative and early remodeling healing phases and comparing these properties with the mechanical properties of the composite healing tissue. Our method was sensitive enough to identify significant differences in structural and material properties between the scar and tendon-scar composite tissues. To account for possible inaccuracies due to the small aspect ratio of scar tissue, we also applied inverse finite element analysis (iFEA) to compute mechanical properties based on simulated tests with accurate specimen geometries and boundary conditions. We found that the scar tissue linear tangent moduli calculated from iFEA were not significantly different from those calculated experimentally at all healing timepoints, validating our experimental findings, and suggesting the assumptions in our experimental calculations were accurate. Taken together, this study first demonstrates that due to the presence of uninjured stubs, testing composite healing tendons without isolating the scar tissue overestimates the material properties of the scar itself. Second, our scar isolation method promises to enable more direct assessment of how different treatment regimens (e.g., cellular ablation, biomechanical and/or biochemical stimuli, tissue engineered scaffolds) affect scar tissue function and material quality in multiple different types of tendons.

A biomechanical study of pediatric flexor profundus tendon repair. Comparing the tensile strengths of 3 suture techniques

Objectives:

To investigate the tensile strength of repaired flexor profundus tendons in young lambs, which would be equivalent to repairs in children older than 2 years of age.

Methods:

A comparative in-vitro experimental study conducted at King Saud University, Riyadh, Kingdom of Saudi Arabia from October 2014 to December 2015. We utilized 30 flexor profundus tendons of young lambs with a width of 4 mm. All tendons were repaired with a 4-strand repair technique using 4/0 polypropylene core sutures. In group I (n=10 tendons), 2 separate figure-of-eight sutures were applied. In group II (n=10 tendons), simple locking sutures were added to the corners of 2 separate figure-of-eight sutures. In group III (n=10 tendons), the locked cruciate repair was used. All tendon repairs were tested to single-cycle tensile failure.

Results:

There was no significant difference between groups II and III with regards to gap and breaking forces; and all forces of these 2 groups were significantly higher than the forces in group I.

Conclusion:

It was concluded that 4 mm-wide pediatric flexor tendons allow a 4-strand repair and the use of 4/0 sutures. The use of locking sutures increases the tensile strength to values that may allow protective mobilization in children.

A barbed suture repair for flexor tendons: a novel technique with no exposed barbs

Background:

Barbed suture technology has shown promise in flexor tendon repairs, as there is an even distribution of load and the need for a knot is eliminated. We propose that a quick and simple, novel, barbed technique without any exposed barbs on the tendon surface has comparable strength and a smaller cross-sectional area at the repair site than traditional methods of repair.

Methods:

Forty porcine flexor tendons were randomized to polybutester 4-strand barbed repair or to 4-strand Adelaide monofilament repair. The cross-sectional area was measured before and after repair. Biomechanical testing was carried out and 2-mm gap formation force, ultimate strength of repair, and method of failure were recorded.

Results:

The mean ultimate strength of the barbed repairs was 54.51 ± 17.9 while that of the Adelaide repairs was 53.17 ± 16.35. The mean 2-mm gap formation force for the barbed group was 44.71 ± 17.86 whereas that of the Adelaide group was 20.25 ± 4.99. The postrepair percentage change in cross-sectional area at the repair site for the Adelaide group and barbed group was 12.0 ± 2.3 and 4.6 ± 2.8, respectively.

Conclusions:

We demonstrated that a 4-strand knotless, barbed method attained comparable strength to that of the traditional Adelaide repair technique. The barbed method had a significantly reduced cross-sectional area at the repair site compared with the Adelaide group. The 2-mm gap formation force was less in the barbed group than the Adelaide group. Barbed repairs show promise for tendon repairs; this simple method warrants further study in an animal model.

The effect of asymmetric core suture purchase on gap resistance of tendon repair in linear cyclic loading

PURPOSE

To evaluate the biomechanical properties of an asymmetric core suture for tendon repair.

METHODS

Sixty porcine flexor tendons were repaired with 3 different 4-strand sutures using different core suture purchases: 2 sets of identical purchases of 10 mm, 2 sets of asymmetric purchases (8 mm proximal/distal stump and 12 mm distal/proximal stump), and 2 sets of identical purchases of 12 mm. The tendons were subjected to the cyclic loading for 20 cycles. The number of tendons with gaps at each cycle, elongation of gap area between tendon ends and tendon segment, gap formation forces, and ultimate strengths were recorded.

RESULTS

Tendons repaired with the asymmetric core suture purchases had the smallest gaps during cyclic loading. The elongation of gaps and tendon segments were significantly smaller than those with symmetric suture purchase of 10 or 12 mm. The asymmetric core suture repair had significant higher gap resistance forces than the symmetric suture repair at the final loading cycle.

CONCLUSIONS

A 4-strand core suture repair with asymmetric purchases on the tendon stumps generated greater gapping resistance than that with an equal length of suture purchase.

CLINICAL RELEVANCE

The asymmetric core suture purchase may be a practical measure to improve gapping resistance and fatigue strength when the suture purchase meets essential length requirements.

The effects of chronic unloading and gap formation on tendon-to-bone healing in a rat model of massive rotator cuff tears

The objective of this study was to understand the effect of pre-repair rotator cuff chronicity on post-repair healing outcomes using a chronic and acute multi-tendon rat rotator cuff injury model. Full-thickness dual tendon injuries (supra- and infraspinatus) were created unilaterally in adult male Sprague Dawley rats, and left chronically detached for 8 or 16 weeks. After chronic detachment, tears were repaired and acute dual tendon injuries were created and immediately repaired on contralateral shoulders. Tissue level outcomes for bone, tendon, and muscle were assessed 4 or 8 weeks after repair using histology, microcomputed tomography, biomechanical testing, and biochemical assays. Substantial gap formation was seen in 35% of acute repairs and 44% of chronic repairs. Gap formation negatively correlated with mechanical and structural outcomes for both healing time points regardless of injury duration. Bone and histomorphometry, as well as biomechanics, were similar between acute and chronic injury and repair regardless of chronicity and duration of healing. This study was the first to implement a multi-tendon rotator cuff injury with surgical repair following both chronic and acute injuries. Massive tear in a rodent model resulted in gap formation regardless of injury duration which had detrimental effects on repair outcomes.

The effect of suture caliber and number of core suture strands on zone II flexor tendon repair: a study in human cadavers

PURPOSE

To compare the tensile properties of a 3-0, 4-strand flexor tendon repair with a 4-0, 4-strand repair and a 4-0, 8-strand repair.

METHODS

Following evaluation of the intrinsic material properties of the 2 core suture calibers most commonly used in tendon repair (3-0 and 4-0), we tested the mechanical properties of 40 cadaver flexor digitorum profundus tendons after zone II repair with 1 of 3 techniques: a 3-0, 4-strand core repair, a 4-0, 8-strand repair, or a 4-0, 4-strand repair. We compared results across suture caliber for the 2 sutures and across tendon repair methods.

RESULTS

Maximum load to failure of 3-0 polyfilament caprolactam suture was 49% greater than that of 4-0 polyfilament caprolactam suture. The cross-sectional area of 3-0 polyfilament caprolactam was 42% greater than that of 4-0 polyfilament caprolactam. The 4-0, 8-strand repair produced greater maximum load to failure when compared with the 2 4-strand techniques. Load at 2-mm gap, stiffness, and work to yield were significantly greater in the 4-0, 8-strand repair than in the 3-0, 4-strand repair.

CONCLUSIONS

In an ex vivo model, an 8-strand repair using 4-0 suture was 43% stronger than a 4-strand repair using 3-0 suture, despite the finding that 3-0 polyfilament caprolactam was 49% stronger than 4-0 polyfilament caprolactam. These results suggest that, although larger-caliber suture has superior tensile properties, the number of core suture strands across a repair site has an important effect on time zero, ex vivo flexor tendon repair strength.

CLINICAL RELEVANCE

Surgeons should consider using techniques that prioritize multistrand core suture repair over an increase in suture caliber.

Recent developments in flexor tendon repair techniques and factors influencing strength of the tendon repair

Over the last decade, both basic researchers and surgeons have sought to identify the most appropriate techniques to be applied in flexor tendon repairs. Recent developments in experimental tendon repairs and clinical outcomes of newer repair techniques have been reviewed in an attempt to comprehensively summarize the most critical mechanical factors affecting the performance of tendon repairs and the surgical factors influencing clinical outcomes. Among them, attention to annular pulleys, the purchase and tension of the core suture, and the direction and curvature of the path of tendon motion have been found to be determining factors in the results of tendon repair.

A nitinol based flexor tendon fixation device: gapping and tensile strength measurements in cadaver flexor tendon

In this study, a new nitinol based fixation device was investigated for use in repairing severed digital flexor tendons. The device, composed of superelastic nitinol, is tubular in shape with inward facing tines for gripping tissue. Its cellular structure was designed such that it has a large effective Poisson's ratio, which facilitates a “finger trap” effect. This allows for reduced tendon compression during a resting state (to permit vascular perfusion) and increased compression during loading (to drive the tines into the tissue for gripping). To test the feasibility of using this device for flexor tendon repair, it was tested on cadaver flexor digitorum profundus tendons. The tendons were excised, cut in the region corresponding to a zone II laceration, and repaired using the device. The device was easy to install and did not prevent the tendon from bending. Constant strain rate tensile testing revealed a mean tensile strength of 57.6 ± 7.7 N, with a force of 53.2 ± 7.8 N at a 2 mm gap. This exceeds the suggested primary repair strength of 45 N, which has been proposed as the necessary strength for enabling early mobilization. Although considerable future studies will be needed to determine the suitability of the new repair device for clinical use, this study demonstrates the feasibility of utilizing a tubular, nitinol repair device for flexor tendon fixation.