Effects of hydroxyapatite and alumina sheaths on postoperative peritendinous adhesions in chickens

Is conservative management of partial zone II flexor tendon laceration possible? A systematic literature review and meta-analysis

Background: There is still no consensus on managing zone II level partial flexor tendon lacerations, and the management of zone II partial flexor tendon injuries is controversial. No reliable large cohort studies or metaanalysis papers on partial flexor tendon laceration management are available in PubMed or Embase.Methods: We searched PubMed, Embase, Cochrane Library, Insight, Scopus, and Web of Science databases for primary research articles investigating outcomes of patients with partial flexor tendon injuries. The initial search was limited to human studies that were published from 1970-2021 and indexed as randomized controlled or clinical trials or observational, cross-sectional, or cohort studies. We used statistical package R version 4.1.2 for this meta-analysis.Results: The Standardised mean difference (SMD) of the common effects model was 2.020 (95% CI; 1.583-2.457; P < 0.0001), indicating that the results of conservative treatment without surgical intervention are similar to surgical intervention or better in some articles. The SMD of the random effect model was 7.093 (95% CI; 1.090-13.096; P < 0.0206), indicating the same result. Higgins' I2 value was 97.6%, indicating serious heterogeneity.Conclusions: In this first meta-analysis on flexor zone II conservative treatment, five papers with publication bias were analyzed. It is meaningful to verify the result of conservative treatment statistically. Even though this is a heterogeneous paper, conservative treatment seems to have a lot of benefits for the patient, including offering a fairly solid longterm prognosis with very few complications.

A novel titanium implant surface modification by plasma electrolytic oxidation (PEO) preventing tendon adhesion

Titanium is one of the most commonly used materials for implants in trauma applications due to its low density, high corrosion resistance and biocompatibility. Nevertheless, there is still a need for improved surface modifications of Titanium, in order to change surface properties such as wettability, antibacterial properties or tissue attachment. In this study, different novel plasma electrolytic oxidation (PEO) modifications have been investigated for tendon adhesion to implants commonly used in hand surgery. Titanium samples with four different PEO modifications were prepared by varying the electrolyte composition and analyzed with regards to their surface properties. Unmodified titanium blanks and Dotize® coating served as controls. Samples were examined using scanning electron microscopy (SEM), energy dispersive spectrometer (EDS), contact angle measuring system and analyzed for their biocompatibility and hemocompatibility (according to DIN ISO 10993-5 and 10,993-4). Finally, tendon adhesion of these specific surfaces were investigated by pull-off tests. Our findings show that surface thickness of PEO modifications was about 12-20 μm and had porous morphology. One modification demonstrated hydrophilic behavior accompanied by good biocompatibility without showing cytotoxic properties. Furthermore, no hemolytic effect and no significant influence on hemocompatibility were observed. Pull-off tests revealed a significant reduction of tendon adhesion by 64.3% (35.7% residual adhesion), compared to unmodified titanium (100%). In summary, the novel PEO-based ceramic-like porous modification for titanium surfaces might be considered a good candidate for orthopedic applications supporting a more efficient recovery.

Sr-HA scaffolds fabricated by SPS technology promote the repair of segmental bone defects

BACKGROUND

Ideal bone defect repair scaffolds should be biodegradable, biocompatible, bioactive, porous, and provide adequate mechanical support. However, it is challenging to fabricate such an ideal bone repair scaffold. Previously, we showed that 5 wt.% strontium-doped hydroxyapatite (Sr-HA) scaffolds prepared by spark plasma sintering (SPS) technology exhibited good biocompatibility. Moreover, unlike pure hydroxyapatite (HA) scaffolds, HA scaffolds containing strontium (Sr) exhibited superior bioactivity, higher proliferation rate of BMSCs and MG-63 osteoblast cells, as well as enhanced BMSCs differentiation.

METHODS

In this study, we prepared pure HA scaffolds and 5 wt.% strontium containing Sr-HA scaffolds by SPS technology without adhesive, ammonium bicarbonate as pore former. Subsequently, scanning electron microscope (SEM) and X-Ray diffraction (XRD) were used to characterize the properties of Sr-HA and HA scaffolds. The ability of the scaffolds to repair bone defects was evaluated using a critical-sized rabbit tibia-bone defect rabbit model. Thirty 3-month-old New Zealand white rabbits were randomly divided into three groups (blank control group, Sr-HA scaffolds implanted group and HA scaffolds implanted group) with 10 rabbits in each group. These rabbits are sacrificed after 8 weeks and 16 weeks of surgery, and the repair effects of each scaffold were evaluated with X-ray, micro-CT, and HE staining. The three-point bending test was employed to assess the mechanical property of repaired bones.

RESULTS

XRD pattern indicated that Sr-HA and HA scaffolds possess a similar crystal structure after sintering, and that incorporation of strontium did not form impure phase. SEM showed that the porosity of Sr-HA and HA scaffolds was about 40 %. Universal Testing Machine tests showed that Sr-HA scaffolds had better compressive strength than HA scaffolds. Bone defect was obvious, and the fibrous tissue was formed in the bone defects of rabbits in the blank control group after 8 weeks of surgery. Sr-HA and HA scaffolds enhanced osteointegration of the host bone, and extensive woven bone was formed on the surface of the Sr-HA scaffolds. After 16 weeks, the bone strump became blunt and a small amount of callus was formed in the blank control group. Comparatively, the scaffolds were substantially degraded in the Sr-HA scaffolds implanted group while scaffolds shadows still were observed in the HA implanted group. Bone remodeling and cavity recanalization were completely developed in the Sr-HA scaffolds group. The compressive strength of repaired bone in the Sr-HA scaffolds implantation group was higher than that of HA scaffolds implantation group after 8 weeks and 16 weeks of surgery.

CONCLUSIONS

Our results show that the Sr-HA composite scaffolds can effectively repair bone defects and have good biodegradable properties.

Hydroxyapatite nanobelt/polylactic acid Janus membrane with osteoinduction/barrier dual functions for precise bone defect repair

Controllable osteoinduction maintained in the original defect area is the key to precise bone repair. To meet the requirement of precise bone regeneration, a hydroxyapatite (HAp) nanobelt/polylactic acid (PLA) (HAp/PLA) Janus membrane has been successfully prepared in this study by coating PLA on a paper-like HAp nanobelt film by a casting-pervaporation method. The Janus membrane possesses dual functions: excellent osteoinduction from the hydrophilic HAp nanobelt side and barrier function originating from the hydrophobic PLA film. The cell viability and osteogenic differentiation ability of human adipose-derived stem cells (hADSCs) on the Janus membrane were assessed. The in vitro experimental results prove that the HAp nanobelt side presents high cell viability and efficient osteoinduction without any growth factor and that the PLA side can prohibit cell attachment. The in vivo repair experiments on a rat mandible defect model prove that the PLA side can prevent postoperative adhesion between bone and adjacent soft tissues. Most importantly, the HAp side has a strong ability to promote defect repair and bone regeneration. Therefore, the HAp/PLA Janus membrane will have wide applications as a kind of tissue engineering material in precise bone repair because of its unique dual osteoinduction/barrier functions, biocompatibility, low cost, and its ability to be mass-produced.

STATE OF SIGNIFICANCE

Precise bone defect repair to keeping tissue integrity and original outline shape is a very important issue for tissue engineering. Here, we have designed and prepared a novel HAp/PLA Janus membrane using a casting-pervaporation method to form a layer of PLA film on paper-like HAp nanobelt film. HAp nanobelt side of the Janus membrane can successfully promote osteogenic differentiation. PLA side of the Janus membrane exhibits good properties as a barrier for preventing the adhesion of cells in vitro. Mandible repair experiments in vivo have shown that the HAp/PLA Janus membrane can promote rat mandible repair on the HAp side and can successfully prevent postoperative adhesion on the PLA side at the same time. Therefore, the HAp/PLA Janus membrane with its osteoinduction/barrier dual functions can be applied to repair bone defect precisely.

Evaluating adhesion reduction efficacy of type I/III collagen membrane and collagen-GAG resorbable matrix in primary flexor tendon repair in a chicken model

BACKGROUND

Reduction of peritendinous adhesions after injury and repair has been the subject of extensive prior investigation. The application of a circumferential barrier at the repair site may limit the quantity of peritendinous adhesions while preserving the tendon's innate ability to heal. The authors compare the effectiveness of a type I/III collagen membrane and a collagen-glycosaminoglycan (GAG) resorbable matrix in reducing tendon adhesions in an experimental chicken model of a "zone II" tendon laceration and repair.

METHODS

In Leghorn chickens, flexor tendons were sharply divided using a scalpel and underwent repair in a standard fashion (54 total repairs). The sites were treated with a type I/III collagen membrane, collagen-GAG resorbable matrix, or saline in a randomized fashion. After 3 weeks, qualitative and semiquantitative histological analysis was performed to evaluate the "extent of peritendinous adhesions" and "nature of tendon healing." The data was evaluated with chi-square analysis and unpaired Student's t test.

RESULTS

For both collagen materials, there was a statistically significant improvement in the degree of both extent of peritendinous adhesions and nature of tendon healing relative to the control group. There was no significant difference seen between the two materials. There was one tendon rupture observed in each treatment group. Surgical handling characteristics were subjectively favored for type I/III collagen membrane over the collagen-GAG resorbable matrix.

CONCLUSION

The ideal method of reducing clinically significant tendon adhesions after injury remains elusive. Both materials in this study demonstrate promise in reducing tendon adhesions after flexor tendon repair without impeding tendon healing in this model.

Multi-layer electrospun membrane mimicking tendon sheath for prevention of tendon adhesions

Defect of the tendon sheath after tendon injury is a main reason for tendon adhesions, but it is a daunting challenge for the biomimetic substitute of the tendon sheath after injury due to its multi-layer membrane-like structure and complex biologic functions. In this study, a multi-layer membrane with celecoxib-loaded poly(l-lactic acid)-polyethylene glycol (PELA) electrospun fibrous membrane as the outer layer, hyaluronic acid (HA) gel as middle layer, and PELA electrospun fibrous membrane as the inner layer was designed. The anti-adhesion efficacy of this multi-layer membrane was compared with a single-layer use in rabbit flexor digitorum profundus tendon model. The surface morphology showed that both PELA fibers and celecoxib-loaded PELA fibers in multi-layer membrane were uniform in size, randomly arrayed, very porous, and smooth without beads. Multi-layer membrane group had fewer peritendinous adhesions and better gliding than the PELA membrane group and control group in gross and histological observation. The similar mechanical characteristic and collagen expression of tendon repair site in the three groups indicated that the multi-layer membrane did not impair tendon healing. Taken together, our results demonstrated that such a biomimetic multi-layer sheath could be used as a potential strategy in clinics for promoting tendon gliding and preventing adhesion without poor tendon healing.

Advances in the healing of flexor tendon injuries

The intrasynovial flexor tendons of the hand are critical for normal hand function. Injury to these tendons can result in absent finger flexion, and a subsequent loss of overall hand function. The surgical techniques used to repair these tendons have improved in the past few decades, as have the postoperative rehabilitation protocols. In spite of these advances, intrasynovial flexor tendon repairs continue to be plagued by postoperative scar formation, which limits tendon gliding and prevents a full functional recovery. This paper describes the current challenges of flexor tendon repair, and evaluates the most recent advances and strategies for achieving an excellent functional outcome.

The Effect of Phospholipids (Surfactant) on Adhesion and Biomechanical Properties of Tendon: A Rat Achilles Tendon Repair Model

Adhesion of the tendon is a major challenge for the orthopedic surgeon during tendon repair. Manipulation of biological environment is one of the concepts to prevent adhesion. Lots of biochemicals have been studied for this purpose. We aimed to determine the effect of phospholipids on adhesion and biomechanical properties of tendon in an animal tendon repair model. Seventy-two Wistar rats were divided into 4 groups. Achilles tendons of rats were cut and repaired. Phospholipids were applied at two different dosages. Tendon adhesion was determined histopathologically and biomechanical test was performed. At macroscopic evaluation of adhesion, there are statistically significant differences between multiple-dose phospholipid injection group and Control group and also hyaluronic acid group and Control group (p < 0.008). At microscopic evaluation of adhesion, there was no statistically significant difference (p > 0.008). Ultimate strength was highest at hyaluronic acid injection group and lowest at multiple-dose phospholipid injection group. Single-dose phospholipids (surfactant) application may have a beneficial effect on the tendon adhesion. Although multiple applications of phospholipids seem the most effective regime to reduce the tendon adhesion among groups, it deteriorated the biomechanical properties of tendon.

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.

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.

A new material for prevention of peritendinous fibrotic adhesions after tendon repair: oxidised regenerated cellulose (Interceed), an absorbable adhesion barrier

In this experimental study, we aimed to examine the ability of absorbable oxidised regenerated cellulose (Interceed, TC-7, Johnson & Johnson, USA) to inhibit the formation of peritendinous fibrotic adhesions after tendon repair in rats. Both Achilles tendons of 23 female Wistar-Albino rats weighing between 350 and 450 grams were cut and repaired. On the right side, Interceed absorbable adhesion barriers were wrapped around the repaired tendon (group I). On the left, the same procedures were applied except for the Interceed wrapping and these were grouped as control (group II). Animals were sacrificed at postoperative day 28 and macroscopic and histological examination was performed. All the animals survived and no tendon rupture was observed. No wound dehiscence, wound infection or exposure of repaired tendons occurred. Macroscopically, there were three (13.1%) tendons without adhesion formation and 20 (86.9%) tendons with inferior adhesion formation in group I; on the other hand, there were 16 tendons (69.5%) with medium grade adhesion formation and seven tendons (30.5%) with severe peritendinous adhesion formation in group II (control group) (p<0.05). Histologically, adhesion formation was absent in 11 tendons (47.8%) and slight in 12 tendons (52.2%) in group I; while in group II, it was slight in two (8.6%), moderate in 15 (65.2%) and severe in six tendons (26.2%) (p<0.05). Sixteen (69.5%) of 23 tendons in group I and 11 (47.8%) of 23 tendons in group II showed no inflammatory reaction (p<0.05). Nineteen (82.6%) tendons in group I and only one tendon in group II showed excellent to good tendon healing (p=0.00). According to our results, we feel that Interceed may have an intraoperative role to play in the reduction of adhesions after surgical tendon repair. This study suggests that absorbable oxidised regenerated cellulose merits further evaluation as a potential treatment to inhibit the formation of peritendinous adhesions. Rigorous and extensive controlled trials should be undertaken on patients undergoing tendon repair with or without this barrier.

The Use of a Hydrogel Sealant on Flexor Tendon Repairs to Prevent Adhesion Formation

The prevention of peritendinous adhesions after zone II flexor tendon repair poses a significant challenge to hand surgeons. This study evaluates a hydrogel sealant (FocalSeal-L) as a barrier to peritendinous adhesion formation. The deep flexors of toes 2 through 4 were divided and repaired in 30 chickens. Chickens were randomized to tendon repair with (n = 15) or without (n = 15) FocalSeal-L. Each group was further randomized to have their tendons studied postoperatively at 3 (n = 10), 6 (n = 10), or 12 (n = 10) weeks. Histologic evaluation revealed decreased peritendinous adhesion formation in the FocalSeal-L group. Biomechanical analysis demonstrated a decrease in work of flexion in the FocalSeal-L group that was most pronounced at 6 weeks (P = 0.0020). There was no significant difference in breaking strength. Apparently, an effective barrier to peritendinous adhesion formation, this sealant system is easy to use, biocompatible, and bioresorbable. In addition, it is not bulky or restrictive to tendon glide.

The future of flexor tendon surgery

Clinical outcomes following flexor tendon repair have made significant improvements in the last 50 years. In that time standard treatment has evolved from secondary grafting to primary repair with postoperative rehabilitation protocols. Unfortunately, excellent results are not yet attained universally following treatment. Improving understanding of tendon healing at the cellular, molecular, and genetic levels will likely enable surgeons to modulate the normal repair process. We now look toward biologic augmentation of flexor tendon repairs to address the problems of increasing tensile strength while reducing adhesion formation following injury and operative repair.

Clinical implications of growth factors in flexor tendon wound healing

Recent research has focused on the role of growth factors in flexor tendon wound healing. These basic science reports have described the identification and quantification of various growth factors in in vitro and in vivo models. Although these reports have begun to piece together the cascade of events involved in flexor tendon wound healing, the clinical relevance for the practicing hand surgeon is unclear. Growth factors are cell-secreted proteins that regulate cellular functions. These growth factors are involved in cell differentiation and growth, including the normal processes of development and tissue repair. Several growth factors recently have been identified as playing roles in tendon healing including vascular endothelial growth factor (VEGF), insulin-like growth factor (IGF), platelet-derived growth factor (PDGF), basic fibroblast growth factor (bFGF), and transforming growth factor beta (TGF-beta). In addition, the transcription factor NF-kappaB has been implicated in the signaling pathways of these growth factors. The purpose of this article is to describe what is known about the molecular basis of flexor tendon wound healing, to review the most commonly studied growth factors, and to summarize likely clinical applications of these growth factors to flexor tendon repair.

Tissue engineering of flexor tendons

Despite technical advances in suture methods and rehabilitation protocols, challenges remain in the field of flexor tendon repair. This article reviews the state-of-the-art research in the tissue engineering of flexor tendons. These early published data will hopefully lay the foundation for molecular methods and materials that can be used to reconstruct tendons to restore normal form and function in the hand.

Chondroitin sulfate-coated polyhydroxyethyl methacrylate membrane prevents adhesion in full-thickness tendon tears of rabbits

Polyhydroxyethyl methacrylate (pHEMA) membranes coated on one side with chondroitin sulfate (CS) were used to block adhesion physically and to reduce friction between healing flexor tendons and the surrounding tissue in rabbit forepaws after surgical repair. Digits with pHEMA-only, standard tendon sheath repair, and with no sheath repair were the controls. Over 12 weeks the CS-coated membranes were evaluated for joint flexion, adhesion limitation, and tendon healing progress. The membranes initially allowed for better flexion (ie, for 6 weeks), but their relative superior effectiveness faded afterward. Histology showed that adhesions were less severe and healing was better in the CS-pHEMA membranes at 3 and 6 weeks. If further studies determine precise amounts or thicknesses of CS coats that will maximize its healing properties, CS-pHEMA should prove useful in clinical settings in which restoration of tendon sheath integrity with a minimum of adhesions is not possible.