The bio-tribological properties of anti-adhesive agents commonly used during tendon repair

The results of preventing postoperative achilles tendon adhesion using cross-linked and non-cross-linked hyaluronic acid, a study with rat model

BACKGROUND

There are many adhesion barrier materials, cross-linked or non-cross-linked hyaluronic acid (HA), used during surgeries.

PURPOSE

This study investigates the efficacy of cross-linked and non-cross-linked HA in preventing Achilles tendon adhesions. We hypothesized that non-cross-linked HA may be more effective than cross-linked HA in preventing Achilles tendon adhesions following injury and repair.

METHODS

Twenty male Sprague Dawley rats, totaling 40 legs, underwent Achilles tendon transection and repair. Following the surgery, they were treated simultaneously with cross-linked and non-cross-linked HA formulations. The rats were divided into four groups: a positive control group, a group treated with BMC non-cross-linked HA gel, a group treated with DEFEHERE cross-linked HA gel, and a group treated with ANIKA cross-linked HA gel. Four weeks after surgery, macroscopic evaluation of peritendinous adhesion and histological analysis were conducted to assess the effectiveness of the treatments.

RESULTS

Non-cross-linked BMC HA demonstrated superior efficacy in preventing tendon adhesions compared to cross-linked HA and control groups. Histological analysis confirmed reduced adhesion severity in the non-cross-linked HA group (P < 0.05). The findings support the potential of non-cross-linked HA as a treatment to inhibit tendon adhesions. Further research, including clinical trials, is warranted to validate these results in human subjects.

CONCLUSIONS

Non-cross-linked BMC HA had significantly lower tendon adhesions parameters and better healing scores in histological analysis than cross-linked HA and control group did. Non-cross-linked HA holds promise as a potential treatment to inhibit the formation of such adhesions.

Advanced technology-driven therapeutic interventions for prevention of tendon adhesion: Design, intrinsic and extrinsic factor considerations

Tendon adhesion formation describes the development of fibrotic tissue between the tendon and its surrounding tissues, which commonly occurs as a reaction to injury or surgery. Its impact on function and quality of life varies from negligible to severely disabling, depending on the affected area and extent of adhesion formed. Thus far, treatment options remain limited with prophylactic anti-inflammatory medications and revision surgeries constituting the only tools within the doctors' armamentarium - neither of which provides reliable outcomes. In this review, the authors aim to collate the current understanding of the pathophysiological mechanisms underlying tendon adhesion formation, highlighting the significant role ascribed to the inflammatory cascade in accelerating adhesion formation. The bulk of this article will then be dedicated to critically appraising different therapeutic structures like nanoparticles, hydrogels and fibrous membranes fabricated by various cutting-edge technologies for adhesion formation prophylaxis. Emphasis will be placed on the role of the fibrous membranes, their ability to act as drug delivery vehicles as well as the combination with other therapeutic structures (e.g., hydrogel or nanoparticles) or fabrication technologies (e.g., weaving or braiding). Finally, the authors will provide an opinion as to the future direction of the prevention of tendon adhesion formation in view of scaffold structure and function designs.

The use of 5-fluorouracil in the prevention of tendon adhesions: A systematic review

BACKGROUND

This systematic review aims to study the effectiveness of 5-fluorouracil (5FU) in the reduction of tendon adhesions postsurgical repair.

METHOD

A systematic review was performed involving four databases, Cochrane, PubMed, MEDLINE, and Embase, looking for evidence of at least Level I or Level II (according to NHMRC) in the use of 5FU in tendon repairs in human or animal studies.

RESULTS

Across the four databases 546 articles were identified. Of these 12 were identified as relevant, with a further two being excluded after in depth review.

CONCLUSIONS

Nine of the 10 studies showed that 5FU was effective at reducing tendon adhesions in their respective animal studies. One of the 10 studies showed no significant change compared to the control group.

Prevention of Peritendinous Adhesion Formation After the Flexor Tendon Surgery in Rabbits: A Comparative Study Between Use of Local Interferon-α, Interferon-β, and 5-Fluorouracil

BACKGROUND

Peritendinous adhesion is the most common complication after tendon surgery, particularly in zone II of the hand. Prevention of inflammation around the tendon, which develops after trauma and surgery, can decrease the tendon adhesion formation. This study compares the effect of some anti-inflammatory cytokines with 5-fluorouracil (5-FU) on the tensile strength and in prevention of peritendinous adhesion formation.

METHODS

Sixteen rabbits were allocated equally into 4 groups. Tendons of the index and ring fingers in zone II of the right hind paw were cut in all animals and then repaired. Interferon (IFN)-α in group 1, 5-FU in group 2, normal saline in group 3, and IFN-β in group 4 were locally applied to the repaired sites. Three weeks later, tensometric and histopathologic evaluations were performed.

RESULTS

The force required for removing the tendon from the sheath was not different between the groups (P = 0.130), but the time required for removal was significantly shorter in 5-FU group (P = 0.049). The strength of repair was not different between the groups in terms of force and time needed for rupture (P = 0.11 and 0.67, respectively). In histopathologic examination, normal architecture of the tendon and peritendon environment was less disturbed in the IFN groups, especially in IFN-β specimens.

CONCLUSIONS

Local application of 5-FU significantly reduced peritendinous adhesion. Local IFN-α and IFN-β had no significant effect on the prevention of peritendinous adhesion formation. The strength of the repair was not affected by these cytokines and 5-FU.

Changes in frictional coefficient with increased tendon surface tear-An experimental animal model

AIM

Surface tribological properties of a tendon in terms of coefficient of friction and lubrication mechanism are expected to change with the progression of surface tears which can affect the optimal function of the tendon. This study investigated whether coefficient of friction proportionally increases with the progression of a surface tear in a bovine tendon model.

METHODS

The study was performed using a pin-on-glass tribometer and bovine tendon samples (n = 16) divided into 4 groups. One group of tendons had no surface tears and thus served as a control, whilst the other 3 groups comprised tendons with increasing severity of artificially-induced surface tears. The coefficient of friction and the lubrication mechanism of the four groups of samples were investigated, calculated and compared.

RESULTS

Statistical analysis showed significant change in coefficient of friction between the control group and the group with minimal tear (p < 0.05) while no difference noted between the groups of moderate to severe tear suggesting that the coefficient of friction increases initially with appearance of surface tears, though further progression to a significant tear do not cause a further increase in the frictional coefficient. There was no change in the lubrication mechanism between the groups.

CONCLUSION

This finding appears to contradict the speculation that the frictional coefficient continues to increase with an increase in surface tear severity. The finding has not been reported before and requires validation in future with testing in human tissue.

Use of human fat grafting in the prevention of perineural adherence: Experimental study in athymic mouse

Perineural adherences represent a problem after surgery involving peripheral neural system. Fat-grafting with adipose derived stem cells (ASCs) with their pro-regenerative characteristics can be important to prevent the neural damage or to facilitate the neural regeneration. Our idea was to use the fat-grafting as an anti-adherence device and test its efficacy on a postsurgical scar animal model and comparing to an antiadhesive gel. 32 athymic mice were operated under magnification, we exposed both sciatic nerves. We randomly divided all sciatic nerves into four experimental groups: burning (1), burning + carboxy-methylcellulose and poly- ethylene oxide (CMC-PEO) (2) + human adipose fat tissue (3), control group (4). Bio-mechanical evaluation was performed to measure the peak force required to pull out the nerve from the muscular bed. Results: in the CMC-PEO group the peak pull out force was 0.37 Newton. In the fat grafted group we registered a peak pull out force of 0.35 N (t Student 0.913). In burning group the force necessary to tear the nerve apart was markedly superior (0.46 N). In control group, we reported the minimal strength (0.31 N) to slide the nerve from the tissue. Histologically, in the group treated with fat-grating, a thinner scar layer was highlighted. Considering the results of this study we can support the efficacy in animal experimental model of fat graft as an anti-adherence device in peripheral nerve surgery.

RelA/p65 inhibition prevents tendon adhesion by modulating inflammation, cell proliferation, and apoptosis

Peritendinous tissue fibrosis which leads to poor tendon function is a worldwide clinical problem; however, its mechanism remains unclear. Transcription factor RelA/p65, an important subunit in the NF-κB complex, is known to have a critical role in many fibrotic diseases. Here, we show that RelA/p65 functions as a core fibrogenic regulator in tendon adhesion and that its inhibition exerts an anti-fibrogenic effect on peritendinous adhesion. We detected the upregulation of the NF-κB pathway in human tendon adhesion using a gene chip microarray assay and revealed the overexpression of p65 and extracellular matrix (ECM) proteins Collagen I, Collagen III, and α-smooth muscle actin (α-SMA) in human fibrotic tissues by immunohistochemistry and western blotting. We also found that in a rat model of tendon injury, p65 expression correlated with tendon adhesion, whereas its inhibition by small interfering (si)RNA prevented fibrous tissue formation and inflammatory reaction as evidenced by macroscopic, biomechanical, histological, immunohistochemical, and western blotting analyses. Furthermore, in cultured fibroblasts, p65-siRNA, p65-specific inhibitor, Helenalin and JSH23 suppressed cell proliferation and promoted apoptosis, whereas inhibiting the mRNA and protein expression of ECM components and cyclo-oxygenase-2, an inflammatory factor involved in tendon adhesion. Our findings indicate that p65 has a critical role in peritendinous tissue fibrosis and suggest that p65 knockdown may be a promising therapeutic approach to prevent tendon adhesion.

Prevention of peritendinous adhesions using an electrospun DegraPol polymer tube: a histological, ultrasonographic, and biomechanical study in rabbits

Purpose. One of the great challenges in surgical tendon rupture repair is to minimize peritendinous adhesions. In order to reduce adhesion formation, a physical barrier was applied to a sutured rabbit Achilles tendon, with two different immobilization protocols used postoperatively. Methods. Thirty New Zealand white rabbits received a laceration on the Achilles tendon, sutured with a 4-strand Becker suture, and half of the rabbits got a DegraPol tube at the repair site. While fifteen rabbits had their treated hind leg in a 180° stretched position during 6 weeks (adhesion provoking immobilization), the other fifteen rabbits were recasted with a 150° position after 3 weeks (adhesion inhibiting immobilization). Adhesion extent was analysed macroscopically, via ultrasound and histology. Inflammation was determined histologically. Biomechanical properties were analysed. Results. Application of a DegraPol tube reduced adhesion formation by approximately 20%—independently of the immobilization protocol. Biomechanical properties of extracted specimen were not affected by the tube application. There was no serious inflammatory reaction towards the implant material. Conclusions. Implantation of a DegraPol tube tightly set around a sutured tendon acts as a beneficial physical barrier and prevents adhesion formation significantly—without affecting the tendon healing process.

History and performance of implant materials applied as peritendinous antiadhesives

Peritendinous fibrotic adhesions after tendon surgery are still a problem up-to-date. Approaches to overcome or at least minimize adhesion formation include implantation of barrier materials, application of lubricants or combinations of materials and functionalized drugs that are controllably released and support the healing tendon to glide and achieve the full range of motion after regeneration. Although a huge amount of different materials have been experimentally tested, the optimal strategy with respect to material and method has not yet been determined. In this review, we present a historical overview of physical barriers as well as liquid agents that have been used in order to prevent peritendinous adhesion formation. The materials are divided according to their first publication into two time frames; before and after 1980. There is no claim to include all materials tested neither will the "best" material be chosen; however, we present several materials that were experimentally tested in different animal trials as well as in clinical trials in contrast to other materials that were only tested once and disappeared from the assortment of anti-adhesives; which as such is a valuable information about its applicability for this purpose.

Gliding resistance and modifications of gliding surface of tendon: clinical perspectives

The smooth gliding of the normal human digital flexor is maintained by synovial fluid lubrication and lubricants bound to the tendon surface. This system can be disrupted by degenerative conditions such as trigger finger, or by trauma. The resistance to tendon gliding after surgical repair of the lacerated digital flexor tendon relates to location of suture knots, exposure of suture materials, and type of surgical repair and materials. Restoration of a functioning gliding surface after injury can be helped by using low-friction, high-strength suture designs, therapy that enables gliding, and the addition of lubricants to the tendon surface.