The Cellular Effect of a Single Interrupted Suture on Tendon

Enhancing prosthesis stability at the cricoid cartilage in equine laryngoplasty using 3-D-printed laryngeal clamps: An ex vivo model study

OBJECTIVE

To assess a three-dimensional (3-D)-printed laryngeal clamp (LC) designed to enhance the anchoring of laryngeal prostheses at the cricoid cartilage.

STUDY DESIGN

Ex vivo biomechanical study.

SAMPLE POPULATION

A total of 22 equine larynges.

METHODS

Two experimental groups included larynges with standard prosthetic laryngoplasty (PL; n = 10) and larynges with prosthetic laryngoplasty modified with laryngeal clamps (PLLC; n = 10). All constructs underwent 3000 cycles of tension loading and a single tension to failure. Recorded biomechanical parameters included maximum load, actuator displacement, and construct failure. Finite element analysis (FEA) was performed on one PL and one PLLC construct.

RESULTS

The maximum load at single tension to failure was 183.7 ± 46.8 N for the PL construct and 292.7 ± 82.3 N for the PLLC construct (p = .003). Actuator displacement at 30 N was 1.7 ± 0.5 mm and 2.7 ± 0.7 mm for the PL and PLLC constructs, respectively (p = .011). The cause of PL constructs failure was mostly tearing through the cartilage whereas the PLLC constructs failed through fracture of the cricoid cartilage (p = .000). FEA revealed an 11-fold reduction in the maximum equivalent plastic strain, a four-fold reduction in maximum compressive stress, and a two-fold increase in the volume of engaged cartilage in PLLC constructs.

CONCLUSION

The PLLC constructs demonstrated superior performance in biomechanical testing and FEA compared to standard PL constructs.

CLINICAL SIGNIFICANCE

The use of 3-D-printed laryngeal clamps may enhance the outcomes of laryngoplasty in horses. In vivo studies are necessary to determine the feasibility of performing laryngoplasty using the laryngeal clamp in horses.

A Hybrid Electrospun-Extruded Polydioxanone Suture for Tendon Tissue Regeneration

Many surgical tendon repairs fail despite advances in surgical materials and techniques. Tendon repair failure can be partially attributed to the tendon's poor intrinsic healing capacity and the repurposing of sutures from other clinical applications. Electrospun materials show promise as a biological scaffold to support endogenous tendon repair, but their relatively low tensile strength has limited their clinical translation. It is hypothesized that combining electrospun fibers with a material with increased tensile strength may improve the suture's mechanical properties while retaining biophysical cues necessary to encourage cell-mediated repair. This article describes the production of a hybrid electrospun-extruded suture with a sheath of submicron electrospun fibers and a core of melt-extruded fibers. The porosity and tensile strength of this hybrid suture is compared with an electrospun-only braided suture and clinically used sutures Vicryl and polydioxanone (PDS). Bioactivity is assessed by measuring the adsorbed serum proteins on electrospun and melt-extruded filaments using mass spectrometry. Human hamstring tendon fibroblast attachment and proliferation were quantified and compared between the hybrid and control sutures. Combining an electrospun sheath with melt-extruded cores created a hybrid braid with increased tensile strength (70.1 ± 0.3N) compared with an electrospun only suture (12.9 ± 1 N, p < 0.0001). The hybrid suture had a similar force at break to clinical sutures, but lower stiffness and stress. The Young's modulus was 772.6 ± 32 MPa for the hybrid suture, 1693.0 ± 69 MPa for PDS, and 3838.0 ± 132 MPa for Vicryl, p < 0.0001. Hybrid sutures had lower overall porosity than electrospun-only sutures (40 ± 4% and 60 ± 7%, respectively, p = 0.0018) but had a significantly larger overall porosity and average pore diameter compared with surgical sutures. There were similar clusters of adsorbed proteins on electrospun and melt-extruded filaments, which were distinct from PDS. Tendon fibroblast attachment and cell proliferation on hybrid and electrospun sutures were significantly higher than on clinical sutures. This study demonstrated that a bioactive suture with increased tensile strength and lower stiffness could be produced by adding a core of 10 μm melt-extruded fibers to a sheath of electrospun fibers. In contrast to currently used sutures, the hybrid sutures promoted a bioactive response: serum proteins adsorbed, and fibroblasts attached, survived, grew along the sutures, and adopted appropriate morphologies.

Bio-Enhanced Neoligaments Graft Bearing FE002 Primary Progenitor Tenocytes: Allogeneic Tissue Engineering & Surgical Proofs-of-Concept for Hand Ligament Regenerative Medicine

Hand tendon/ligament structural ruptures (tears, lacerations) often require surgical reconstruction and grafting, for the restauration of finger mechanical functions. Clinical-grade human primary progenitor tenocytes (FE002 cryopreserved progenitor cell source) have been previously proposed for diversified therapeutic uses within allogeneic tissue engineering and regenerative medicine applications. The aim of this study was to establish bioengineering and surgical proofs-of-concept for an artificial graft (Neoligaments Infinity-Lock 3 device) bearing cultured and viable FE002 primary progenitor tenocytes. Technical optimization and in vitro validation work showed that the combined preparations could be rapidly obtained (dynamic cell seeding of 10⁵ cells/cm of scaffold, 7 days of co-culture). The studied standardized transplants presented homogeneous cellular colonization in vitro (cellular alignment/coating along the scaffold fibers) and other critical functional attributes (tendon extracellular matrix component such as collagen I and aggrecan synthesis/deposition along the scaffold fibers). Notably, major safety- and functionality-related parameters/attributes of the FE002 cells/finished combination products were compiled and set forth (telomerase activity, adhesion and biological coating potentials). A two-part human cadaveric study enabled to establish clinical protocols for hand ligament cell-assisted surgery (ligamento-suspension plasty after trapeziectomy, thumb metacarpo-phalangeal ulnar collateral ligamentoplasty). Importantly, the aggregated experimental results clearly confirmed that functional and clinically usable allogeneic cell-scaffold combination products could be rapidly and robustly prepared for bio-enhanced hand ligament reconstruction. Major advantages of the considered bioengineered graft were discussed in light of existing clinical protocols based on autologous tenocyte transplantation. Overall, this study established proofs-of-concept for the translational development of a functional tissue engineering protocol in allogeneic musculoskeletal regenerative medicine, in view of a pilot clinical trial.

How controlled motion alters the biophysical properties of musculoskeletal tissue architecture

INTRODUCTION

Movement is fundamental to the normal behaviour of the hand, not only for day-to-day activity, but also for fundamental processes like development, tissue homeostasis and repair. Controlled motion is a concept that hand therapists apply to their patients daily for functional gains, yet the scientific understanding of how this works is poorly understood.

PURPOSE OF THE ARTICLE

To review the biology of the tissues in the hand that respond to movement and provide a basic science understanding of how it can be manipulated to facilitate better functionThe review outlines the concept of controlled motion and actions across the scales of tissue architecture, highlighting the the role of movement forces in tissue development, homeostasis and repair. The biophysical behaviour of mechanosensitve tissues of the hand such as skin, tendon, bone and cartilage are discussed.

CONCLUSION

Controlled motion during early healing is a form of controlled stress and can be harnessed to generate appropriate reparative tissues. Understanding the temporal and spatial biology of tissue repair allows therapists to tailor therapies that allow optimal recovery based around progressive biophysical stimuli by movement.

In vitro evaluation of the response of human tendon-derived stromal cells to a novel electrospun suture for tendon repair

Recurrent tears after surgical tendon repair remain common. Repair failures can be partly attributed to the use of sutures not designed for the tendon cellular niche nor for the promotion of repair processes. Synthetic electrospun materials can mechanically support the tendon whilst providing topographical cues that regulate cell behaviour. Here, a novel electrospun suture made from twisted polydioxanone (PDO) polymer filaments is compared to PDS II, a clinically-used PDO suture currently utilised in tendon repair. We evaluated the ability of these sutures to support the attachment and proliferation of human tendon-derived stromal cells using PrestoBlue and Scanning Electron Microscopy. Suture surface chemistry was analysed using X-ray Photoelectron Spectroscopy. Bulk RNA-Seq interrogated the transcriptional response of primary tendon-derived stromal cells to sutures after 14 days. Electrospun suture showed increased initial cell attachment and a stronger transcriptional response compared to PDS II, with relative enrichment of pathways including mTorc1 signalling and depletion of epithelial mesenchymal transition. Neither suture induced transcriptional upregulation of inflammatory pathways compared to baseline. Twisted electrospun sutures therefore show promise in improving outcomes in surgical tendon repair by allowing increased cell attachment whilst maintaining an appropriate tissue response.

The strengths of one-, two-, and three-weave Pulvertaft tendon repairs

We tested the tensile strength of the proximal juncture of tendon grafts with Pulvertaft tendon repairs in 18 cadaveric digital flexor tendons. These tendons were divided into three groups of six: single, two, or three weaves. Each of the interlacing weaves was secured with eight anchoring sutures. The specimens were loaded in a biomechanical tester until failure. The ultimate tensile strength did not show any significant differences across all three groups with statistical power of 0.77. The mean tendon elongation before repair failure showed significant difference at 10 mm (standard deviation (SD) 2), 16 mm (SD 3), and 15 mm (SD 3), respectively. All specimens failed by intra-tendinous pull-out of the weaves. We conclude that the two-weave Pulvertaft construct demonstrated comparable tensile strength to three weaves and tendon elongation was similar when two or three weaves were used.

Microsurgical reconstruction affects the outcome in a translational mouse model for Achilles tendon healing

Background

Animal models are one of the first steps in translation of basic science findings to clinical practice. For tendon healing research, transgenic mouse models are important to advance therapeutic strategies. However, the small size of the structures complicates surgical approaches, histological assessment, and biomechanical testing. In addition, available models are not standardized and difficult to compare. How surgery itself affects the healing outcome has not been investigated yet. The focus of the study was to develop a procedure that includes a transection and microsurgical reconstruction of the Achilles tendon but, unlike other models, preserves the sciatic nerve. We wanted to examine how distinct parts of the technique influenced healing.

Methods

For this animal model study, we used 96 wild-type male C57BL/6 mice aged 8–12 weeks. We evaluated different suture techniques and macroscopically confirmed the optimal combination of suture material and technique to minimize tendon gap formation. A key element is the detailed, step-by-step illustration of the surgery. In addition, we assessed histological (Herovici and Alcian blue staining) outcome parameters at 1–16 weeks postoperatively. Microcomputed tomography (micro-CT) was performed to measure the bone volume of heterotopic ossifications (HOs). Biomechanical analyses were carried out using a viscoelastic protocol on the biomechanical testing machine LM1.

Results

A modified 4-strand suture combined with a cerclage for immobilization without transection of the sciatic nerve reliably eliminated gap formation. The maximal dorsal extension of the hindlimb at the upper ankle joint from the equinus position (limited by the immobilization cerclage) increased over time postoperatively (operation: 28.8 ± 2.2°; 1 week: 54 ± 36°; 6 weeks: 80 ± 11.7°; 16 weeks: 96 ± 15.8°, p > 0.05). Histological staining revealed a maturation of collagen fibres within 6 weeks, whereas masses of cartilage were visible throughout the healing period. Micro-CT scans detected the development of HOs starting at 4 weeks and further progression at 6 and 16 weeks (bone volume, 4 weeks: 0.07604 ± 0.05286 mm³; 6 weeks: 0.50682 ± 0.68841 mm³; 16 weeks: 2.36027 ± 0.85202 mm³, p > 0.001). In-depth micro-CT analysis of the different surgical elements revealed that an injury of the tendon is a key factor for the development of HOs. Immobilization alone does not trigger HOs. Biomechanical properties of repaired tendons were greatly altered and remained inferior 6 weeks after surgery.

Conclusion

With this study, we demonstrated that the microsurgical technique greatly influences the short- and longer-term healing outcome. When the sciatic nerve is preserved, the best surgical reconstruction of the tendon defect is achieved by a 4-strand core suture in combination with a tibiofibular cerclage for postoperative immobilization. The cerclage promotes a gradual increase in the range of motion of the upper ankle joint, comparable with an early mobilization rehabilitation protocol. HO, as a key mechanism for poor tendon healing, is progressive and can be monitored early in the model.

The translational potential of this article

The study enhances the understanding of model dependent factors of healing. The described reconstruction technique provides a reproducible and translational rodent model for future Achilles tendon healing research. In combination with transgenic strains, it can be facilitated to advance therapeutic strategies to improve the clinical results of tendon injuries.

The evidence-base for the management of flexor tendon injuries of the hand: Review

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There is no consensus on the optimal flexor tendon repair technique at each anatomical flexor zone.

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There is paucity of high quality evidence.

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Heterogenous study designs limit inter-study comparisons.

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Patient reported outcome measures are crucial but there is a perennial need for robust disease-specific tools to be utilised.

An Exploratory Study Using Semi-Tabular Plate in Zone II Flexor Tendon Repair

Background: This study evaluated the feasibility of using a low-profile titanium (Ti) plate implant, also known as the Ti-button, for Zone II flexor tendon repair. We hypothesize that the use of the Ti-button can distribute the tensile force on the digital flexor tendons to achieve better biomechanical performance.

Methods: Twenty lacerated porcine flexor tendons were randomly divided into two groups and repaired using Ti-button or 6-strand modified Lim-Tsai technique. Ultimate tensile strength, load to 2 mm gap force, and mode of failure were recorded during a single cycle loading test. We also harvested twelve fingers with lacerated flexor digitorum profundus tendons from six fresh-frozen cadaver hands and repaired the tendons using either Ti-button method or modified Lim-Tsai technique. A custom-made bio-friction measurement jig was used to measure the gliding resistance and coefficient of friction of the tendon sheath interface at the A2 pulley.

Results: The ultimate tensile strength, load to 2 mm gap force, stiffness, and gliding resistance of the Ti-button repairs were 101.5 N, 25.7 N, 7.8 N/mm, and 2.2 N respectively. Ti-button repairs had significantly higher ultimate tensile strength and stiffness than the modified Lim-Tsai repair. However, Ti-button also increased the gliding resistance and coefficient of friction but there was no significant difference between the two repair techniques.

Conclusions: Ti-button repair displayed comparable mechanical properties to the traditional repair in terms of 2-mm gap formation and gliding resistance, but with a stronger repair construct. Thus, this deepened our interest to further investigate the potential of using Ti-button implant in Zone II flexor tendon repair by studying both the mechanical and biochemical (tendon healing) properties in more in-depth.

Biomechanical comparison of modified Lim/Tsai tendon repairs with intra- and extra-tendinous knots

We compared the Lim/Tsai tendon repair technique using an extra-tendinous knot with modification using an intra-tendinous knot. The ultimate tensile strength, load to 2 mm gap force, stiffness, mode of failure, location of failure, and time taken to repair each tendon were recorded during a single cycle loading test in 20 tendons with each repair method. We found that the ultimate tensile strength and 2 mm gap force of the modified Lim/Tsai repair with an extra-tendinous knot (56 SD 5 N and 14 SD 2 N, respectively) were statistically significantly higher than that of the modified Lim/Tsai repair with intra-tendinous knot (51 SD 7 N and 11 SD 2 N, respectively). We conclude that the modified Lim/Tsai repair with extra-tendinous knot is stronger, despite having the same number of core strands.

Comparison of Flexor Tendon Suture Techniques Including 1 Using 10 Strands

PURPOSE

To compare mechanical properties of a multistrand suture technique for flexor tendon repair with those of conventional suture methods through biomechanical and clinical studies.

METHODS

We describe a multistrand suture technique that is readily expandable from 6 to 10 strands of core suture. For biomechanical evaluation, 60 porcine flexor tendons were repaired using 1 of the following 6 suture techniques: Kessler (2-strand), locking cruciate (4-strand), Lim/Tsai's 6-strand, and our modified techniques (6-, 8-, or 10-strand). Structural properties of each tenorrhaphy were determined through tensile testing (ultimate failure load and force at 2-mm gap formation). Clinically we repaired 25 flexor tendons using the described 10-strand technique in zones I and II. Final follow-up results were evaluated according to the criteria of Strickland and Glogovac.

RESULTS

In the biomechanical study, tensile properties were strongly affected by repair technique; tendons in the 10-strand group had approximately 106%, 66%, and 39% increased ultimate load to failure (average, 87 N) compared with those in the 4-, 6-, and 8-strand groups, respectively. Tendons in the 10-strand group withstood higher 2-mm gap formation forces (average, 41 N) than those with other suture methods (4-strand, 26 N; 6-strand, 27 N; and 8-strand, 33 N). Clinically, we obtained 21 excellent, 2 good, and 2 fair outcomes after a mean of 16 months (range, 6-53 mo) of follow-up. No patients experienced poor results or rupture.

CONCLUSIONS

The 10-strand suture repair technique not only increased ultimate strength and force at the 2-mm gap formation compared with conventional suture methods, it also showed good clinical outcomes. This multistrand suture technique can greatly increase the gap resistance of surgical repair, facilitating early mobilization of the affected digit.

TYPE OF STUDY/LEVEL OF EVIDENCE

Therapeutic IV.

A comparative study of the effects of growth and differentiation factor 5 on muscle-derived stem cells and bone marrow stromal cells in an in vitro tendon healing model

PURPOSE

To investigate the ability of muscle-derived stem cells (MDSCs) supplemented with growth and differentiation factor-5 (GDF-5) to improve tendon healing compared with bone marrow stromal cells (BMSCs) in an in vitro tendon culture model.

METHODS

Eighty canine flexor digitorum profundus tendons were assigned into 5 groups: repaired tendon (1) without gel patch interposition (no cell group), (2) with BMSC-seeded gel patch interposition (BMSC group), (3) with MDSC-seeded gel patch interposition (MDSC group), (4) with GDF-5-treated BMSC-seeded gel patch interposition (BMSC+GDF-5 group), and (5) with GDF-5-treated MDSC-seeded gel patch interposition (MDSC+GDF-5 group). After culturing for 2 or 4 weeks, the failure strength of the healing tendons was measured. The tendons were also evaluated histologically.

RESULTS

The failure strength of the repaired tendon in the MDSC+GDF-5 group was significantly higher than that of the non-cell and BMSC groups. The stiffness of the repaired tendons in the MDSC+GDF-5 group was significantly higher than that of the non-cell group. Histologically, the implanted cells became incorporated into the original tendon in all 4 cell-seeded groups.

CONCLUSIONS

Interposition of a multilayered GDF-5 and MDSC-seeded collagen gel patch at the repair site enhanced tendon healing compared with a similar patch using BMSC. However, this increase in vitro was relatively small. In the clinical setting, differences between MDSC and BMSC may not be substantially different, and it remains to be shown that such methods might enhance the results of an uncomplicated tendon repair clinically.

CLINICAL RELEVANCE

Muscle-derived stem cell implantation and administration of GDF-5 may improve the outcome of tendon repair.

The Interlocking Modification of the Cross Locked Cruciate Tendon Repair (Modified Adelaide Repair): A Static and Dynamic Biomechanical Assessment

The 4-strand cross-locked cruciate flexor tendon repair technique (Adelaide technique) has been shown to have comparably high resistance to gap formation and ultimate tensile strength. This study aimed to determine whether an interlocking modification to the Adelaide repair would impart improved biomechanical characteristics. Twenty four sheep flexor tendons were harvested, transected and repaired using either standard or modified Adelaide techniques. Repaired tendons were cyclically loaded. Gap formation and ultimate tensile strength were measured. Additionally, suture exposure on the tendon surface was determined. There was a statistically significant increase in resistance to gap formation in the early phase of cyclic loading within the modified Adelaide group. In the later stages of testing no significant difference could be noted. The average final load to failure in the modified group was higher than the standard group but this did not achieve statistical significance. Interlocking suture techniques in four strand tendon repair constructs can improve gapping behavior in the early phase of cyclic loading.

Flexor tendon healing within the tendon sheath using bioabsorbable poly-L/D-lactide 96/4 suture. A histological in vivo study with rabbits

The bioabsorbable poly-L/D-lactide (PLDLA) 96/4 suture has good biomechanical and knot properties, and sufficient tensile strength half-life for flexor tendon repair. In the present study, the biocompatibility of PLDLA suture was compared with that of coated braided polyester suture in the rabbit flexor digitorum profundus tendon repaired within the tendon sheath. Postoperative unrestricted active mobilization was allowed. The tendons were studied histologically after 1-, 3-, 6-, 12-, 26-, and 52-week follow-ups. No differences were found in the biocompatibility between the suture materials, with only scattered multinuclear giant cells near the sutures in both groups from 6 weeks onwards. At 52 weeks, most of the PLDLA material was absorbed and the histological structure of the tendon appeared normal, whereas in the polyester repairs the suture knots filled the repair site, causing bulking of the tendon surface, and the collagen alignment appeared disoriented. The results suggest that the PLDLA 96/4 is a suitable suture material for flexor tendon repair.

Correspondence of high-frequency ultrasound and histomorphometry of healing rabbit Achilles tendon tissue

OBJECTIVES

Static and dynamic high-frequency ultrasound of healing rabbit Achilles tendons were set in relationship to histomorphometric analyses at three and six weeks post-surgery.

MATERIALS AND METHODS

Twelve New Zealand White rabbits received a clean-cut Achilles tendon laceration (the medial and lateral Musculus gastrocnemius) and were repaired with a four-strand Becker suture. Six rabbits got additionally a tight polyester urethane tube at the repair site in order to vary the adhesion extent. Tendons were analysed by static and dynamic ultrasound (control: healthy contralateral legs). The ultrasound outcome was corresponded to the tendon shape, tenocyte and tenoblast density, tenocyte and tenoblast nuclei width, collagen fibre orientation and adhesion extent.

RESULTS

The spindle-like morphology of healing tendons (ultrasound) was confirmed by the swollen epitenon (histology). Prediction of adhesion formation by dynamic ultrasound assessment was confirmed by histology (contact region to surrounding tissue). Hyperechogenic areas corresponded to acellular zones with aligned fibres and hypoechogenic zones to not yet oriented fibres and to cell-rich areas.

CONCLUSIONS

These findings add new in-depth structural knowledge to the established non-invasive analytical tool, ultrasound.

Performance of a knotless four-strand flexor tendon repair with a unidirectional barbed suture device: a dynamic ex vivo comparison

With increased numbers of reports using barbed sutures for tendon repairs we felt the need to design a specific tendon repair method to draw the best utility from these materials. We split 30 sheep deep flexor tendons in two groups of 15 tendons. One group was repaired with a new four-strand barbed suture repair method without knot. The other group was repaired with a conventional four-strand cross-locked cruciate repair method (Adelaide repair) with knot. Dynamic testing (3-30 N for 250 cycles) and additional static pull to failure was performed to investigate gap formation and final failure forces. The barbed suture repair group showed higher resistance to gap formation throughout the test. Additionally final failure force was higher for the barbed suture group compared with the conventional repair group. When used appropriately, barbed suture materials could be beneficial to use in tendon surgery, especially with regard to early loading of the repair site and gap formation.

Primary flexor tendon surgery: the search for a perfect result

Repair of the divided flexor tendon to achieve normal, or near normal, function is an unsolved problem, with each result still uncertain. The authors believe the way forward in primary flexor tendon surgery clinically is by use of strengthened but simpler sutures, appropriate venting of the pulley system, and maintaining early rehabilitation. However, there needs also be consideration of patient factors and other aspects. Research needs to continue more widely, in both the laboratory and the clinical environment, to find ways of better modifying adhesions after surgical repair of the tendon.

Avoidance of unfavourable results following primary flexor tendon surgery

This review describes the biological problems faced by those managing primary flexor tendon injuries and explains why these problems still thwart attempts to achieve normal, or near normal, function after this injury, despite a century of surgical effort. It considers the historical background of the early 20(th) century attempts to improve the results and analyses the clinical usefulness of more recent research into tendon core and circumferential suture modification, including the authors' work in this field, and changes in post-operative mobilisation over the last 50 years. More recent manipulation of the sheath to improve results and the future possibility of manipulation of adhesions are discussed. It also discusses other factors, e.g., the patient, the experience of the surgeon, the use of therapists, the timing of repair, complex injuries, injuries in zones other than zone 2, which can have a bearing on the results and considers how these can be modified to avoid an unfavourable outcome.

The effect of suture coated with mesenchymal stem cells and bioactive substrate on tendon repair strength in a rat model

PURPOSE

Exogenously administered mesenchymal stem cells and bioactive molecules are known to enhance tendon healing. Biomolecules have been successfully delivered using sutures that elute growth factors over time. We sought to evaluate the histologic and biomechanical effect of delivering both cells and bioactive substrates on a suture delivery vehicle in comparison with sutures coated with bioactive substrates alone.

METHODS

Bone marrow-derived stem cells were harvested from Sprague-Dawley rat femurs. Experimental cell and substrate-coated, coated suture (CS) group sutures were precoated with intercellular cell adhesion molecule 1 and poly-L-lysine and seeded with labeled bone marrow-derived stem cells. Control (substrate-only [SO] coated) group sutures were coated with intercellular cell adhesion molecule 1 and poly-L-lysine only. Using a matched-paired design, bilateral Sprague-Dawley rat Achilles tendons (n = 105 rats) were transected and randomized to CS or SO repairs. Tendons were harvested at 4, 7, 10, 14, and 28 days and subjected to histologic and mechanical assessment.

RESULTS

Labeled cells were present at repair sites at all time points. The CS suture repairs displayed statistically greater strength compared to SO repairs at 7 days (12.6 ± 5.0 N vs 8.6 ± 3.7 N, respectively) and 10 days (21.2 ± 4.9 N vs 16.4 ± 4.8 N, respectively). There was no significant difference between the strength of CS suture repairs compared with SO repairs at 4 days (8.1 ± 5.1 N vs 6.6 ± 2.3 N, respectively), 14 days (22.8 ± 7.3 N vs 25.1 ± 9.7 N, respectively), and 28 days (40.9 ± 12.4 N vs 34.6 ± 15.0 N, respectively).

CONCLUSIONS

Bioactive CS sutures enhanced repair strength at 7 to 10 days. There was no significant effect at later stages.

CLINICAL RELEVANCE

The strength nadir of a tendon repair occurs in the first 2 weeks after surgery. Bioactive suture repair might provide a clinical advantage by jump-starting the repair process during this strength nadir. Improved early strength might, in turn allow earlier unprotected mobilization.

Albumin-coated bioactive suture for cell transplantation

Cell therapy holds the promise for a novel modality in the surgical toolkit; however, delivery of cells into damaged soft tissues constitutes a challenge. The authors hypothesized that growing stem cells on the surface of absorbable sutures in vitro and then implanting them via stitching would be a suitable delivery route for cell therapy. Fibronectin, poly-L-lysine, and albumin coatings were used to increase attachment of human and rat bone-marrow-derived mesenchymal stem cells (BMSC) to polyfilament absorbable sutures in vitro. Fluorescence microscopy was performed to localize the cells on the suture. After 48 hours of incubation, the albumin-coated sutures had the highest cell number, and after 168 hours cell number reached confluency. In the in vivo experiments, a 10-mm incision was made on the triceps surae muscle of male Wistar rats and rat BMSC coated sutures were placed into the muscle. Two days after the implantation, cells were seen on the surface of the sutures as well as in the surrounding muscle tissue. Long-term results at 5 weeks showed that transplanted cells survived and the sutures were partly absorbed. In conclusion, coating absorbable sutures with proteins, especially serum albumin, improves attachment and proliferation of cells, and only 48 hours in culture is enough to cover the sutures sufficiently. Using these stitches in vivo resulted in short-term and long-term survival of cells. As a result, albumin-coated suture can be a vehicle for stem cell therapy in soft tissues such as muscle, tendon, or peripheral nerves.

Epitendinous suture techniques in extensor tendon repairs--an experimental evaluation

PURPOSE

The tension-band principle might be relevant to extensor tendon repairs, and a dorsal-only Silfverskiöld epitendinous repair is stronger and stiffer than more conventional techniques in vitro. We aimed to evaluate the strength and stiffness of the strongest epitendinous sutures described, using an in vitro model that subjects the repair to angular force over a pulley, thereby creating a tension-band model.

METHODS

Silfverskiöld dorsal-only epitendinous extensor tendon repairs in porcine foot tendons (n = 8) were compared to reverse (buried) Silfverskiöld (n = 8), Halsted (n = 8), and interrupted horizontal mattress (IHM) repairs (n = 6) in vitro with a tensiometer around a 45° pulley. Thirty tendons total were tested to assess the force required for 2-mm gapping and ultimate tensile strength.

RESULTS

The IHM repair had a significantly higher ultimate tensile strength (43 N; SD, 10 N) than the other repairs, which had strengths between 27 N (SD, 4 N) and 31 N (SD, 7 N). The IHM was also significantly more resistant to gapping than the Silfverskiöld and Halsted repairs.

CONCLUSIONS

Interlocking horizontal mattress, dorsal-only extensor tendon repairs were significantly stronger and more resistant to gapping than Silfverskiöld and Halsted repairs. Other repairs were still strong and resistant to gapping in comparison to previously published data for conventional repairs.

CLINICAL RELEVANCE

The IHM is a relatively difficult technique to perform, and it remains to be seen whether the additional strength translates to clinical benefits over the easier Silfverskiöld technique.

Outcome of zone 2 flexor tendon injuries: Kleinert versus controlled active motion therapy regimens

Introduction

No single optimal regimen for the rehabilitation of flexor tendon injuries has yet been determined. We aimed to evaluate if a change in rehabilitation from a modified Kleinert to a controlled active motion (CAM) regimen had an effect on outcomes in a regional plastic surgery unit. We did this by comparing ruptures and range of movement of zone 2 repairs following both Kleinert and CAM regimens.

Methods

We performed a retrospective case series review, analysing data collected prospectively between 2004 and 2007. During 2004 and 2005, patients were rehabilitated with a modified Kleinert regimen, and during 2006 and 2007 a CAM regimen was used. We looked at total active motion (TAM) and ruptures at 12-week follow-up for all zone 2 repairs, and compared the two regimens.

Results

There were 38 patients with 42 injured digits in the Kleinert group, and 34 patients with 39 injured digits in the CAM group. There was no statistically significant difference in TAM achieved between the Kleinert and CAM regimens overall (70% versus 72% of normal in each group respectively, P = 0.70 t-test). Patients over 30 years old achieved significantly worse outcomes in the Kleinert group than in the CAM group ( P = 0.03). One digit ruptured following a Kleinert regimen (2.6%) compared with four digits in the CAM group (11.7%).

Conclusion

In this study, we found no overall difference in outcome following a Kleinert or CAM rehabilitation regimen. Rupture rates were higher in the CAM group by four-fold. In our patients those over 30 years had poorer outcomes when rehabilitated with a Kleinert regimen.

The effects of growth and differentiation factor 5 on bone marrow stromal cell transplants in an in vitro tendon healing model

The effects of growth differentiation factor-5 (GDF-5) and bone marrow stromal cells (BMSCs) on tendon healing were investigated under in vitro tissue culture conditions. BMSCs and GDF-5 placed in a collagen gel were interpositioned between the cut ends of dog flexor digitorum profundus tendons. The tendons were randomly assigned into four groups: 1) repaired tendon without gel; 2) repaired tendon with BMSC-seeded gel; 3) repaired tendon with GDF-5 gel without cells; and 4) repaired tendon with GDF-5 treated BMSC-seeded gel. At 2 and 4 weeks, the maximal strength of repaired tendons with GDF-5 treated BMSCs-seeded gel was significantly higher than in tendons without gel interposition. However, neither BMSCs nor GDF-5 alone significantly increased the maximal strength of healing tendons at 2 or 4 weeks. These results suggest that the combination of BMSCs and GDF-5 accelerates tendon healing, but either BMSCs or GDF-5 alone are not effective in this model.

The tension band principle and angular testing of extensor tendon repairs

Extensor tendons in the finger are flat and not amenable to repair by core and epitendinous sutures. Mattress sutures and Kessler repairs without epitendinous stitching are often used for extensor tendon divisions in the fingers. Except when in full extension, the finger presents a series of curved surfaces (at each joint) to the tendon. It was hypothesized that extensor tendons are subject to the 'tension band' principle and that they might be amenable to repair by dorsal-only epitendinous sutures. A Silfverskiöld dorsal-only repair was compared with mattress and Kessler repairs in vitro on a curvilinear testing apparatus. The epitendinous technique was found to be significantly more resistant to gapping and rupture, as well as more resistant to deformation (i.e. stiffer) than the conventional techniques.

IMMEDIATE AND LATE EFFECT OF SUTURES IN EXTRASYNOVIAL TENDONS: BIOMECHANICAL STUDY IN RATS

Objective: The aim of this study was to evaluate the effects on the mechanical properties of rats’ calcaneus tendons, of repair arrangements using suture material in the absence of any healing process. Method: Twelve male Wistar rats were used. They were subjected to placement of a modified Kessler suture stitch in the calcaneus tendon. The sacrifices were performed immediately after and six weeks after the operation. The mechanical properties studied were maximum load, tension in the maximum load and module of elasticity. The contralateral tendon was used as a control. Results: The statistical analysis showed that for the times studied, the values for mechanical properties did not present any significant differences. In relation to the control, i.e. the contralateral tendon without a suture, the results demonstrated that, six weeks after the operation, the values for the modulus of elasticity were lower, whereas there were no significant variations in maximum load or tension at maximum load. Conclusion: Placement of suture material on an extrasynovial tendon without lesions decreased the modulus of elasticity, but it did not interfere with the maximum load or tension at maximum load, six weeks after the operation.

Influence of locking stitch size in a four-strand cross-locked cruciate flexor tendon repair

PURPOSE

The 4-strand cross-locked cruciate technique (Adelaide technique) for repairing flexor tendons in zone II is a favorable method in terms of strength and simplicity. The purpose of this study was to investigate the effects of varying the cross-lock stitch size in this repair technique. Outcomes measured were load to failure and gap formation.

METHODS

We harvested 22 deep flexor tendons from adult pig forelimbs and randomly allocated them into 2 groups. After cutting the tendons at a standard point, we performed a 4-strand cross-locked cruciate repair using 3-0 braided polyester with either 2-mm cross-locks (n = 11) or 4-mm cross-locks (n = 11). All repairs were completed with a simple running peripheral suture using 6-0 polypropylene. Repaired tendons were loaded to failure and the mechanism of failure, load to failure, stiffness, and load to 2-mm gap formation were determined.

RESULTS

All repairs failed by suture breakage; we noted no suture pullout. There was no difference in load to failure (71.7-71.1 N; p = .89) or stiffness (4.1-4.6 N/mm; p = .23) between the 2-mm cross-lock and the 4-mm cross-lock groups. There was a trend toward higher resistance to 2-mm gap formation with the 4-mm cross-locks (55-62.2 N; p = .07).

CONCLUSIONS

Four-strand cross-locked cruciate repairs with cross-lock sizes of 2 and 4 mm provide high tensile strength and are resistant to pullout. Repairs with 4-mm cross-locks tend to provide a more central load distribution and better gapping resistance than repairs with 2-mm cross-locks.

Viability and proliferation of pluripotential cells delivered to tendon repair sites using bioactive sutures--an in vitro study

PURPOSE

We evaluated the fate of pluripotential stem cells adherent to a suture carrier after being passed through tendon tissue in vitro.

METHODS

FiberWire suture segments were coated with poly-L-lysine (PLL) and a 2 × 10(6) C3H10T1/2 (a mouse embryo pluripotential cell line) cell suspension. The sutures were incubated for 7 days, passed through two 1-cm segments of acellularized rabbit Achilles tendons and tied (horizontal mattress). The repairs were frozen and sectioned (6 μm). The sections were stained with 4',6-diamidino-2-phenylindole and a live/dead viability/cytotoxicity (calcein/ethidium homodimer) kit and examined with fluorescent microscopy to evaluate cell presence and viability. Alamar Blue was used in parallel to assess metabolic activity.

RESULTS

PLL-coated sutures showed a 3-fold increase in fluorescence when compared with the phosphate-buffered saline-coated controls. At day 3, fluorescence was 2.2 times greater. At day 5, a 2-fold increase was found, and at day 8 there was no significant difference in values. Furthermore, after delivery of the cells into tendon, fluorescence readings for the samples (n = 19) showed 9450 compared with the positive control at 21,218. At 96 hours the mean was 27,609 compared with 34,850 for the positive control. The difference in fluorescence means at 48 hours and 96 hours were significant (p < .001). Live-dead and DAPI staining confirmed the presence of live cells at the tendon repair site.

CONCLUSIONS

Sutures seeded with pluripotential embryonic cells deliver cells to a tendon repair site. The cells deposited at the repair site survive the trauma of passage and remain metabolically active, as seen in staining and metabolic assay studies. Use of bioactive sutures leads to repopulation of the acellular zone surrounding sutures within the tendon.

Tendon is covered by a basement membrane epithelium that is required for cell retention and the prevention of adhesion formation

The ability of tendons to glide smoothly during muscle contraction is impaired after injury by fibrous adhesions that form between the damaged tendon surface and surrounding tissues. To understand how adhesions form we incubated excised tendons in fibrin gels (to mimic the homeostatic environment at the injury site) and assessed cell migration. We noticed cells exiting the tendon from only the cut ends. Furthermore, treatment of the tendon with trypsin resulted in cell extravagation from the shaft of the tendons. Electron microscopy and immunolocalisation studies showed that the tendons are covered by a novel cell layer in which a collagen type IV/laminin basement membrane (BM) overlies a keratinised epithelium. PCR and western blot analyses confirmed the expression of laminin β1 in surface cells, only. To evaluate the cell retentive properties of the BM in vivo we examined the tendons of the Col4a1^+/Svc mouse that is heterozygous for a G-to-A transition in the Col4a1 gene that produces a G1064D substitution in the α1(IV) chain of collagen IV. The flexor tendons had a discontinuous BM, developed fibrous adhesions with overlying tissues, and were acellular at sites of adhesion formation. In further experiments, tenotomy of wild-type mice resulted in expression of laminin throughout the adhesion. In conclusion, we show the existence of a novel tendon BM-epithelium that is required to prevent adhesion formation. The Col4a1^+/Svc mouse is an effective animal model for studying adhesion formation because of the presence of a structurally-defective collagen type IV-containing BM.

The cell biology of suturing tendons

Trauma by suturing tendon form areas devoid of cells termed "acellular zones" in the matrix. This study aimed to characterise the cellular insult of suturing and acellular zone formation in mouse tendon. Acellular zone formation was evaluated using single grasping sutures placed using flexor tendons with time lapse cell viability imaging for a period of 12h. Both tension and injury were required to induce cell death and cell movement in the formation of the acellular zone. DNA fragmentation studies and transmission electron microscopy indicated that cells necrosed. Parallel in vivo studies showed that cell-to-cell contacts were disrupted following grasping by the suture in tensioned tendon. Without tension, cell death was lessened and cell-to-cell contacts remained intact. Quantitative immunohistochemistry and 3D cellular profile mapping of wound healing markers over a one year time course showed that acellular zones arise rapidly and showed no evidence of healing whilst the wound healing response occurred in the surrounding tissues. The acellular zones were also evident in a standard modified "Kessler" clinical repair. In conclusion, the suture repair of injured tendons produces acellular zones, which may potentially cause early tendon failure.

The cellular biology of flexor tendon adhesion formation: an old problem in a new paradigm

Intrasynovial flexor tendon injuries of the hand can frequently be complicated by tendon adhesions to the surrounding sheath, limiting finger function. We have developed a new tendon injury model in the mouse to investigate the three-dimensional cellular biology of intrasynovial flexor tendon healing and adhesion formation. We investigated the cell biology using markers for inflammation, proliferation, collagen synthesis, apoptosis, and vascularization/myofibroblasts. Quantitative immunohistochemical image analysis and three-dimensional reconstruction with cell mapping was performed on labeled serial sections. Flexor tendon adhesions were also assessed 21 days after wounding using transmission electron microscopy to examine the cell phenotypes in the wound. When the tendon has been immobilized, the mouse can form tendon adhesions in the flexor tendon sheath. The cell biology of tendon healing follows the classic wound healing response of inflammation, proliferation, synthesis, and apoptosis, but the greater activity occurs in the surrounding tissue. Cells that have multiple "fibripositors" and cells with cytoplasmic protrusions that contain multiple large and small diameter fibrils can be found in the wound during collagen synthesis. In conclusion, adhesion formation occurs due to scarring between two damaged surfaces. The mouse model for flexor tendon injury represents a new platform to study adhesion formation that is genetically tractable.

Effect of gelatin hydrogel incorporating fibroblast growth factor 2 on human meniscal cells in an organ culture model

Efforts to use growth factors to enhance the healing potential of the meniscus have been impeded because their half-lives are too short to maintain the biological activity. The thread was coated with gelatin hydrogel and fibroblast growth factor 2 (FGF 2) was biologically stabilized by incorporating in a gelatin hydrogel-coated thread. The purpose of this study is to investigate the effect of gelatin hydrogel-coated thread incorporating FGF 2 on human meniscal cells in an organ culture. Twenty-five menisci were cut into small pieces, and selected pieces were sutured with gelatin hydrogel-coated thread incorporating FGF 2 (FGF(+) group) or physiologic saline (FGF(-) group), followed by organ culture. The meniscal samples histologically evaluated 4, 7, and 14 days later. The cell density and the number of PCNA-positive cells for the FGF(+) group were higher than those of the FGF(-) group, while the number of TUNEL-positive cells was lower. These results suggest that FGF 2 stimulates the proliferation of meniscal cells and inhibits meniscal cell death. Gelatin hydrogel-coated threads releasable FGF 2 may be useful to promote repairing of human meniscus.

Digital oedema, adhesion formation and resistance to digital motion after primary flexor tendon repair

The development of digital oedema, adhesion formation, and resistance to digital motion at days 0, 3, 5, 7, 9 and 14 after primary flexor tendon repairs using 102 long toes of 51 Leghorn chickens was studied. Oedema presented as tissue swelling from days 3 to 7, which peaked at day 3. After day 7, oedema was manifest as hardening of subcutaneous tissue. The degree of digital swelling correlated with the resistance to tendon motion between days 3 and 7. At day 9, granulation tissues were observed around the tendon and loose adhesions were observed at day 14. Resistance to digital motion increased significantly from day 0 to day 3, but did not increase between days 3 and 9. The early postoperative changes appear to have three stages: initial (days 0-3, increasing resistance with development of oedema), delayed (days 4-7, higher resistance with continuing oedema) and late (after day 7-9, hardening of subcutaneous tissue with development of adhesions).

Bioactive sutures for tendon repair: assessment of a method of delivering pluripotential embryonic cells

PURPOSE

Pluripotential embryonic cells may be seeded onto sutures intended for tendon repair. These cells may be influenced to adhere to suture material using adhesion substrates, and furthermore, these cells may remain in culture attached to those sutures. These cell-impregnated sutures may be useful for promoting healing of tendon repairs.

METHODS

Ten-centimeter segments of 4-0 sutures (FiberWire) were coated overnight with 10 microg/mL fibronectin, 10 microg/mL poly-l-lysine, or phosphate-buffered saline. The sutures were placed in dishes and covered with a suspension of C3H10T1/2 cells at concentrations of 1 x 10(6), 2 x 10(6), or 4 x 10(6) cells for 24 hours. The sutures were then placed into low adhesion polypropylene tubes with Dulbecco's modified Eagle's medium and 10% fetal bovine serum for 7 days. The presence of viable cells on these sutures was assessed by the colorimetric Alamar blue cell proliferation assay. Spectrophotometry was used to quantify the relative amount of cell proliferation across the experimental groups. The sutures were also visually inspected using phase-contrast light microscopy.

RESULTS

Our results show that at all seeding densities (1 x 10(6), 2 x 10(6), and 4 x 10(6) cells), the suture segments coated with poly-l-lysine and fibronectin showed a significant increase in C3H10T1/2 cell adhesion. Coating the suture with poly-l-lysine increased the adherent cell number to 17% of the initial seeding concentration compared with 2% for the control. Fibronectin coating increased the number of adherent viable cells present to 6.6%.

CONCLUSIONS

Pluripotential embryonic cells may be seeded onto sutures, adhere, and survive in culture. Coating sutures with poly-l-lysine and fibronectin offers significant improvement in retention of viable cells. This technique may be a useful adjunct for future tendon healing studies.

Comparison of zones 1 to 4 flexor tendon repairs using absorbable and unabsorbable four-strand core sutures

Absorbable sutures behave favourably in vitro and in an animal model. We report the outcome of flexor tendon injuries in a series of 272 consecutive patients treated over 45 months with a mean follow-up of 4 (range 3-12) months. Five hundred and seventy-six tendons were repaired in 416 digits. The patients were not randomised and all repairs were performed using a Strickland four-strand core technique. In 191 (73%) patients an absorbable core suture was used (Group 1) and in 81 (27%) a non-absorbable material was used (Group 2). There were six ruptures (2%) in Group 1 and two (2%) in Group 2. Using the original Strickland criteria, there were 72% excellent/good and 28% fair/poor results in the absorbable core suture group, and 73% and 27%, respectively, in the non-absorbable core suture group. This study suggests that appropriate absorbable core sutures can be used safely for flexor tendon repair.

Flexor tendon injuries of the hand treated with TenoFix: mid-term results

BACKGROUND

Recently, the Teno Fix device has been detailed in the literature. Conventional stranded cruciate repair requires splinting to protect the sutures from excessive loading, and then, active motion is strongly limited leading to a possible incomplete functional recovery.

MATERIALS AND METHODS

The authors report on their experience in treating 21 patients presenting primary flexor tendon injuries within the digital sheath in zone 2, in all fingers (including the thumb), at an average follow-up of 16 (range: 6-26) months.

RESULTS

There were, according to Strickland and Glogovac criteria: 12 excellent; 6 good; 3 fair.

CONCLUSIONS

This new device is practical clinically and can effect strong tendon repairs that withstand early active finger motion, but the best indication is to treat only selected cases of sharp flexor tendon lesions in zone 2. Using this technique it is possible to achieve a quick functional recovery and early return to work.