Early breaking strength of repaired flexor tendon treated with 5-fluorouracil

Flexor Tendon Adhesion Formation: Current Concepts

Over the years, various physical and chemical/biological methods of inhibiting adhesion formation have been developed, focusing on how to suppress healing around the tendon and not inhibit healing within the tendon. Unfortunately, however, these methods are accompanied by drawbacks, both large and small, and no absolute antiadhesion method capable of maintaining tendon repair strength has yet been developed. Recent innovations in biomaterials science and tissue engineering have produced new antiadhesion technologies, such as barriers combined with cytokines and cells, which have improved outcomes in animal models, and which may find clinical relevance in the future.

Prevention of postoperative adhesions after flexor tendon repair with acellular dermal matrix in Zones III, IV, and V of the hand: A randomized controlled (CONSORT-compliant) trial

BACKGROUND

Various techniques have been attempted for preventing postoperative flexor tendon adhesion, such as modification of suture technique, pharmacological agents, and mechanical barriers. However, there is no evidence of the efficacy of these methods in clinical settings. In this study, we present the long-term outcomes of a randomized prospective study in which acellular dermal matrix (ADM) was used to prevent postoperative adhesions after tendon injury in the hand.

METHODS

From January 2017 to January 2020, all patients with an acute single flexor tendon injury in hand Zones III, IV, or V were candidates. A single-digit, total tendon rupture repaired within 48 hours, from the index finger to the little finger, was included in the study. Patients were randomly allocated to either a control or ADM group. Complications and the range of movements were recorded. Functional outcomes and a patient satisfaction questionnaire were evaluated after 12 months following the tendon repair surgery. The present study is adhered to the CONSORT guidelines.

RESULTS

A total of 25 patients was enrolled in the study: 13 patients in the ADM group and 12 in the control group. According to Buck-Gramcko II criteria, the postoperative functional outcome score was 14.38 ± 1.71 in the ADM group and 13.08 ± 1.82 in the control group (P value = .0485). Patient satisfaction was recorded at 8.38 ± 1.44 in the ADM group and 7.08 ± 1.58 in the control group (P value = .0309), a significant difference. There were no differences in complications between the 2 groups.

CONCLUSION

The beneficial effects of ADM after tendon repair were confirmed by improved postoperative functional outcome at flexor Zones III, IV, and V, preventing peritendinous adhesions and acting effectively as an anti-adhesive barrier.

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.

Cell and Biologic-Based Treatment of Flexor Tendon Injuries

The two primary factors leading to poor clinical results after intrasynovial tendon repair are adhesion formation within the digital sheath and repair-site elongation and rupture. As the outcomes following modern tendon multi-strand repair and controlled rehabilitation techniques are often unsatisfactory, alternative approaches, such as the application of growth factors and mesenchymal stem cells (MSCs), have become increasingly attractive treatment options. Successful biological therapies require carefully controlled spatiotemporal delivery of cells, growth factors, and biocompatible scaffold matrices in order to simultaneously (1) promote matrix synthesis at the tendon repair site leading to increased biomechanical strength and stiffness and (2) suppress matrix synthesis along the tendon surface and synovial sheath preventing adhesion formation. This review summarizes recent cell and biologic-based experimental treatments for flexor tendon injury, with an emphasis on large animal translational studies.

Prediction of the elastic strain limit of tendons

The elastic strain limit (ESL) of tendons is the point where maximum elastic modulus is reached, after which micro-damage starts. Study of damage progression in tendons under repetitive (fatigue) loading requires a priori knowledge about ESL. In this study, we propose three different approaches for predicting ESL. First, one single value is assumed to represent the ESL of all tendon specimens. Second, different extrapolation curves are used for extrapolating the initial part of the stress-strain curve. Third, a method based on comparing the shape of the initial part of the stress-strain curve of specimens with a database of stress-strain curves is used. A large number of porcine tendon explants (97) were tested to examine the above-mentioned approaches. The variants of the third approach yielded significantly (p<0.05) smaller error values as compared to the other approaches. The mean absolute percentage error of the best-performing variant of the shape-based comparison was between 8.14±6.44% and 9.96±9.99% depending on the size of the initial part of the stress-strain curves. Interspecies generalizability of the best performing method was also studied by applying it for prediction of the ESL of horse tendons. The ESL of horse tendons was predicted with mean absolute percentage errors ranging between 10.53±7.6% and 19.16±14.31% depending on the size of the initial part of the stress-strain curves and the type of normalization. The results of this study suggest that both ESL and the shape of stress-strain curves may be highly different between different individuals and different anatomical locations.

Hyaluronan modulates proliferation and migration of rabbit fibroblasts derived from flexor tendon epitenon and endotenon

PURPOSE

There is a growing body of evidence supporting the use of hyaluronan (HA) for treatment of injured tendons, although the mechanism of the healing effect has not yet been clarified. We therefore investigated the effects of HA on the proliferation and migration of tendon fibroblasts derived from rabbit flexor tendon epitenon and endotenon.

METHODS

From explanted rabbit intrasynovial flexor tendons (n = 5), we cultured tendon fibroblasts derived from the epitenon and endotenon. CD44 expression on the tendon fibroblasts was detected by flow cytometric analysis. Various concentrations of HA (0.1-5.0 mg/mL) were added to monolayer-cultured tendon fibroblasts. We evaluated cell proliferation by recording changes in cell number, and measured cell migration by wound-healing assay.

RESULTS

Flow cytometric analysis detected CD44 expression on the tendon fibroblasts. Treatment with HA at various concentrations notably and dose dependently inhibited cell proliferation and promoted cell migration.

CONCLUSIONS

Hyaluronan modulates the proliferation and migration of rabbit fibroblasts derived from the flexor tendon epitenon and endotenon.

Surface treatment with 5-fluorouracil after flexor tendon repair in a canine in vivo model

BACKGROUND

Topical 5-fluorouracil has been reported to reduce adhesions in animal models of tenolysis. The purpose of this study was to investigate the effects of topical 5-fluorouracil on adhesion formation after tendon repairs were subjected to immediate postoperative rehabilitation in a canine model in vivo.

METHODS

Sixty dogs were randomly assigned to either a 5-fluorouracil treatment (thirty dogs) or a control group (thirty dogs). Each treatment group was then divided into three survival time points: ten days, twenty-one days, and forty-two days. The second and fifth flexor digitorum profundus tendons from each dog were fully lacerated at the zone-II area and then were repaired. Passive motion therapy started at day 5 postoperatively and continued until the dogs were killed. The repaired tendons were evaluated for normalized work of flexion, gliding resistance, repair strength, gene expression for type-I and type-III collagen and transforming growth factor-beta1, and histological appearance.

RESULTS

The normalized work of flexion of the repaired tendons treated with 5-fluorouracil was significantly lower than that of the repaired tendons without 5-fluorouracil treatment at ten days. However, there was no significant difference between treated and untreated tendons at twenty-one and forty-two days. There was also no significant difference in gliding resistance, repair failure strength, or stiffness between treated and untreated tendons at any time point, or in the gross or histological appearance of adhesions at the time of killing. The expression of types-I and III collagen and transforming growth factor-beta1 of the repaired tendon with 5-fluorouracil treatment was significantly lower than that of the tendons without treatment at ten days postoperatively, but not at twenty-one or forty-two days.

CONCLUSIONS

Although 5-fluorouracil treatment can reduce adhesions in in vivo models of tenolysis, this treatment had only a transient effect in an in vivo model of tendon repair that included passive motion.

Auto-crosslinked hyaluronic acid gel accelerates healing of rabbit flexor tendons in vivo

This study's purpose was to assess the in vivo effect of auto-crosslinked hyaluronic acid (HA) gel, a natural HA derivative with increased viscosity and tissue residence time, on adhesions and healing of injured and surgically repaired rabbit digital flexor tendons. The second and third right deep digital flexor tendons from 48 rabbits (n = 96 tendons) were cut and repaired with a modified Kessler and running peripheral suture. Animals were randomized to two groups, receiving either HA gel or saline injected around both freshly repaired tendons. After 2, 3, 6, and 12 weeks, six rabbits in each group were euthanized. Tendon pull-out force and breaking strength were measured as a value for adhesion formation and tendon healing, respectively. A histological assessment of adhesions and healing was related to the mechanical results. A significantly faster increase in breaking strength was found in HA gel-treated compared to saline-treated tendons; this coincided with a significantly accelerated tissue repair response after injury. No significant difference in adhesion formation was found between the two groups at any time. Our results indicate a significant acceleration of in vivo healing of tendons treated with HA gel. Adhesion formation was unaffected. These results could have important clinical value in promoting rehabilitation after tendon injury.

Prevention of adhesions in surgery of the flexor tendons of the hand: what is the evidence?

INTRODUCTION

Despite advances in knowledge and refinements of technique, the management of flexor tendon injuries within the digital sheath continues to present a formidable challenge. This in turn has led to a massive expansion in search of modified surgical therapies and various adjuvant therapies, which could prevent adhesion formation without compromising digital function.

SOURCES OF DATA

A search of PubMed, Medline, CINAHL and Embase databases was performed using the keywords 'tendon adhesion prevention', 'tendon healing', 'adhesion prevention in tendons' and 'adjuvants for adhesion prevention'. Studies detailing the use of surgical, pharmacological and non-pharmacological agents for adhesion prevention in digital flexor tendons were identified, and their bibliographies were thoroughly reviewed to identify further related articles. This search identified 41 studies, which investigated the use of various pharmacological agents in adhesion prevention in digital tendons.

AREAS OF AGREEMENT

There is a need to develop and utilize an optimal method for the prevention of adhesions in the flexor tendons of the hand, due to post-surgical complications.

AREAS OF CONTROVERSY

Even though there have been significant advances in the prevention of adhesions in flexor tendons, it remains to be proved which, if any, of the current methods are the most beneficial.

GROWING POINTS

The only thing that appears clinically justified in adhesion prevention is the need for early post-operative mobilization of digits after tendon injury or repair but the best method of mobilization remains controversial.

AREAS TIMELY FOR DEVELOPING RESEARCH

Suggested changes in surgical techniques and various proposed pharmacological and non-pharmacological modalities need to withstand the test of adequately powered human trials, before their justification for potential benefit in clinical practice is accepted.

The effect of thermal preconditioning of the limb on flexor tendon healing

Thermal preconditioning reduces inflammation by inducing cytoprotective heat shock proteins. We evaluated the role of limb thermal preconditioning in a rabbit model of flexor tendon repair. The treatment groups underwent limb preconditioning by elevating the limb temperature to 41.5 degrees C for 20 minutes. The animals were sacrificed three and six weeks after flexor tendon repair. Heat shock protein72 expression of the treated limb was measured at 18 hours. Macroscopic analysis demonstrated a significant decrease in adhesion formation in the three week treatment group. The inflammatory infiltrate was significantly reduced for both treatment groups. The difference in ultimate tensile strength was not significant. We conclude that thermal preconditioning of the limb before flexor tendon repair decreases inflammation and adhesion formation in a rabbit model and has the potential to improve clinical outcome of flexor tendon surgery.