The cell biology of suturing tendons

Management of partial extensor tendon lacerations of the hand and forearm: A national survey of practice in the United Kingdom

BACKGROUND

Partial extensor tendon lacerations of the hand and forearm are common. There is a lack of evidence to guide their management and it is also unclear at what threshold surgeons would consider repair necessary. This study aimed to identify national surgical management of partial extensor tendon lacerations of the hand and forearm (zones 2-8) and assess surgeons' willingness to randomise in a future trial.

METHODS

A 34-item online survey was developed by the steering group and, via a trainee-led collaborative model, was disseminated to plastic and orthopaedic surgeons in the UK. Summary data were calculated for each survey item, and the variations between zones and specialties were explored using linear regression.

RESULTS

142 complete responses were recorded (response rate 71%). On average, respondents said that 46% tendon division was the maximum they would manage in clinical practice without surgical repair. There was no significant difference in this percentage between zones or surgical specialties. Importantly, the majority (83%) of surgeons would be willing to randomise patients in a clinical trial to repair versus no-repair, within 29%-61% tendon division, demonstrating clinical equipoise.

CONCLUSIONS

There is significant variation in UK practice regarding the surgical management of partial extensor tendon lacerations of the hand and forearm and clinical equipoise exists regarding the decision to repair or not. A definitive randomised trial is warranted to identify the optimum management of this common injury.

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.

Current clinical opinion on surgical approaches and rehabilitation of hand flexor tendon injury-a questionnaire study

The management of flexor tendon injury has seen many iterations over the years, but more substantial innovations in practice have been sadly lacking. The aim of this study was to investigate the current practice of flexor tendon injury management, and variation in practice from the previous reports, most troublesome complications, and whether there was a clinical interest in potential innovative tendon repair technologies. An online survey was distributed via the British Society for Surgery of the Hand (BSSH) and a total of 132 responses were collected anonymously. Results showed that although most surgeons followed the current medical recommendation based on the literature, a significant number of surgeons still employed more conventional treatments in clinic, such as general anesthesia, ineffective tendon retrieval techniques, and passive rehabilitation. Complications including adhesion formation and re-rupture remained persistent. The interest in new approaches such as use of minimally invasive instruments, biodegradable materials and additive manufactured devices was not strong, however the surgeons were potentially open to more effective and economic solutions.

Instantaneous self-healing and strongly adhesive self-adaptive hyaluronic acid-based hydrogel for controlled drug release to promote tendon wound healing

The treatment of tendon injuries is an important healthcare challenge. Irregular wounds, hypocellularity, and prolonged inflammation impede the rate of healing for tendon injuries. To address these problems, a high-tenacity shape-adaptive, mussel-like hydrogel (PH/GMs@bFGF&PDA) was designed and constructed with polyvinyl alcohol (PVA) and hyaluronic acid grafted with phenylboronic acid (BA-HA) by encapsulating polydopamine and gelatin microspheres containing basic fibroblast growth factor (GMs@bFGF). The shape-adaptive PH/GMs@bFGF&PDA hydrogel can quickly adapt to irregular tendon wounds, and the strong adhesion (101.46 ± 10.88 kPa) can keep the hydrogel adhered to the wound at all times. In addition, the high tenacity and self-healing properties allow the hydrogel to move with the tendon without fracture. Additionally, even if fractured, it can quickly self-heal and continue to adhere to the tendon wound, while slowly releasing basic fibroblast growth factor during the inflammatory phase of the tendon repair process, promoting cell proliferation, migration and shortening the inflammatory phase. In acute tendon injury and chronic tendon injury models, PH/GMs@bFGF&PDA significantly alleviated inflammation and promoted collagen I secretion, enhancing wound healing through the synergistic effects of its shape-adaptive and high-adhesion properties.

Localized delivery of ibuprofen via a bilayer delivery system (BiLDS) for supraspinatus tendon healing in a rat model

The high prevalence of tendon retear following rotator cuff repair motivates the development of new therapeutics to promote improved tendon healing. Controlled delivery of non-steroidal anti-inflammatory drugs to the repair site via an implanted scaffold is a promising option for modulating inflammation in the healing environment. Furthermore, biodegradable nanofibrous delivery systems offer an optimized architecture and surface area for cellular attachment, proliferation, and infiltration while releasing soluble factors to promote tendon regeneration. To this end, we developed a bilayer delivery system (BiLDS) for localized and controlled release of ibuprofen (IBP) to temporally mitigate inflammation and enhance tendon remodeling following surgical repair by promoting organized tissue formation. In vitro evaluation confirmed the delayed and sustained release of IBP from Labrafil-modified poly(lactic-co-glycolic) acid microspheres within sintered poly(ε-caprolactone) electrospun scaffolds. Biocompatibility of the BiLDS was demonstrated with primary Achilles tendon cells in vitro. Implantation of the IBP-releasing BiLDS at the repair site in a rat rotator cuff injury and repair model led to decreased expression of proinflammatory cytokine, tumor necrotic factor-α, and increased anti-inflammatory cytokine, transforming growth factor-β1. The BiLDS remained intact for mechanical reinforcement and recovered the tendon structural properties by 8 weeks. These results suggest the therapeutic potential of a novel biocompatible nanofibrous BiLDS for localized and tailored delivery of IBP to mitigate tendon inflammation and improve repair outcomes. Future studies are required to define the mechanical implications of an optimized BiLDS in a rat model beyond 8 weeks or in a larger animal model.

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 use of bidirectional barbed suture in the treatment of a complete common calcanean tendon rupture in a dog: Long-term clinical and ultrasonographic evaluation

The canine common calcanean tendon can be repaired successfully using a modified Kessler knotless barbed technique. A long-term ultrasound follow-up showed improved and increased normal tendon fibrillar echotexture and homogeneity.

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.

Four-Dimensional Imaging of Soft Tissue and Implanted Biomaterial Mechanics: A Barbed Suture Case Study for Tendon Repair

Timely, recent developments in X-ray microcomputed tomography (XμCT) imaging such as increased resolution and improved sample preparation enable nondestructive time-lapse imaging of polymeric biomaterials when implanted in soft tissue, which we demonstrate herein. Imaging the full three-dimensional (3D) structure of an implanted biomaterial provides new opportunities to assess the micromechanics of the interface between the implant and tissues and how this changes over time as force is applied in load-bearing musculoskeletal applications. In this paper, we present a case study demonstrating in situ XμCT and finite element analysis, using a dynamically loaded barbed suture repair for its novel use in tendon tissue. The aim of this study was to identify the distribution of stress in the suture and tendon as load is applied. The data gained demonstrate a clear 3D visualization of microscale features in both the tissue and implant in wet conditions. XμCT imaging has revealed, for the first time, pores around the suture, preventing full engagement of all the barbs with the tendon tissue. Subsequent finite element analysis reveals the localized stress and strain, which are not evenly distributed along the suture, or throughout the tissue. This case study demonstrates for the first time a powerful in situ mechanical imaging tool, which could be readily adapted by other laboratories to interrogate and optimize the interface between the implanted biomaterials and the soft tissue.

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.

Improving results of flexor tendon repair and rehabilitation

BACKGROUND

The global time and effort attributed to improving outcomes in the management of flexor tendon injury are large, but the degree of advancement made over the past 50 years is relatively small. This review examines the current perceived wisdom in this field and aims to explore the limitations to the authors' understanding of the tendon healing process, examining how this may be a factor that has contributed to the authors' modest progress in the field.

METHODS

The authors critically evaluate the sum of laboratory and clinical literature on the topic of zone II flexor tendon management that has guided their practice and provide evidence to support their methods.

RESULTS

The review highlights some of the key developments over the years and assesses their influence on changing current practice. It also highlights recent innovations, which have the potential to influence flexor tendon outcomes by altering the surgical approach, techniques, and rehabilitation regimens. Future innovations in the field will also be discussed to examine their potential in expanding the development in the management of flexor tendon injury.

CONCLUSIONS

A better understanding of flexor tendon biology will allow progress in developing new therapies for flexor tendon injuries; however, there are as yet few real breakthroughs that will dramatically change current practice.

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

Background:

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

Methods:

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

Results:

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

Conclusions:

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

Sutured tendon repair; a multi-scale finite element model

Following rupture, tendons are sutured to reapproximate the severed ends and permit healing. Several repair techniques are employed clinically, with recent focus towards high-strength sutures, permitting early active mobilisation thus improving resultant joint mobility. However, the arrangement of suture repairs locally alters the loading environment experienced by the tendon. The extent of the augmented stress distribution and its effect on the tissue is unknown. Stress distribution cannot be established using traditional tensile testing, in vivo, or ex vivo study of suture repairs. We have developed a 3D finite element model of a Kessler suture repair employing multiscale modelling to represent tendon microstructure and incorporate its highly orthotropic behaviour into the tissue description. This was informed by ex vivo tensile testing of porcine flexor digitorum profundus tendon. The transverse modulus of the tendon was 0.2551 \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\pm $$\end{document}± 0.0818 MPa and 0.1035 \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\pm $$\end{document}± 0.0454 MPa in proximal and distal tendon samples, respectively, and the interfibrillar tissue modulus ranged from 0.1021 to 0.0416 MPa. We observed an elliptically shaped region of high stress around the suture anchor, consistent with a known region of acellularity which develop 72 h post-operatively and remain for at least a year. We also observed a stress shielded region close to the severed tendon ends, which may impair collagen fibre realignment during the remodelling stage of repair due to the lack of tensile stress.

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.

Support for partial lesions of the flexor tendons of the fingers: a retrospective study of 36 cases

The treatment of traumatic partial injuries of the flexor tendons of the fingers is seldom published. The only published clinical series states that the therapeutic approach depends on the existence or absence of a preoperative trigger. We hypothesized that the therapeutic attitude mainly depends on the percentage of the injured cross-section. Our retrospective series included 36 partial lesions of 31 fingers in 29 patients. The average age was 42 years, there were 19 men. We noted 8 lesions in zones I, 21 in zone II and 2 in zone III. The average percentage of the injured cross-section was 35% and ranged from 10% to 90%. If the lesion was less than 50% (29 tendons), a tangential resection was performed. If the lesion exceeded 50% (seven tendons), a direct suture was performed, supplemented by a running suture. At a follow-up of 34 months, the average pain on a visual analogue scale was 0.7. The average percentage of strength compared to the contralateral side was 93%. The Quick DASH score was 6.2. The range of motion averaged 214° with extremes ranging from 90° to 260°. We observed no cases of hypertrophic callus, neither through the MRI nor through the ultrasonography. Complications such as trigger finger, pseudoblocage or rupture were not observed. Based on our results, in case of partial injury of a flexor tendon, we propose to perform a tangential resection in cross-section lesions up to 50%, and a suture for those which exceeded 50%.

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.

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

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

Suture techniques for tendon repair; a comparative review

Over the past five decades we have seen numerous iterations of suture repair methods for tendon. The pursuit of the ultimate repair has led to many repair methods being described. This comprehensive compilation of the suture repair techniques will describe the factors that affect repair success, including repair strength, gapping resistance, glide and rehabilitation. Different approaches to rejoining severed tendons will be critiqued on their biomechanical ability to improve tendon repair strength, maintaining glide, reducing tendon damage, and minimising adhesion formation. It is important to highlight how the suture repairs have evolved and improved but also review how they may contribute to their own trauma. The apparent paradox between providing mechanical strength and minimising adhesions require refinements in the field to improve on functional outcomes.

Suture techniques for tendon repair; a comparative review

Over the past five decades we have seen numerous iterations of suture repair methods for tendon. The pursuit of the ultimate repair has led to many repair methods being described. This comprehensive compilation of the suture repair techniques will describe the factors that affect repair success, including repair strength, gapping resistance, glide and rehabilitation. Different approaches to rejoining severed tendons will be critiqued on their biomechanical ability to improve tendon repair strength, maintaining glide, reducing tendon damage, and minimising adhesion formation. It is important to highlight how the suture repairs have evolved and improved but also review how they may contribute to their own trauma. The apparent paradox between providing mechanical strength and minimising adhesions require refinements in the field to improve on functional outcomes.

A conceptual framework for computational models of Achilles tendon homeostasis

Computational modeling of tendon lags the development of computational models for other tissues. A major bottleneck in the development of realistic computational models for Achilles tendon is the absence of detailed conceptual and theoretical models as to how the tissue actually functions. Without the conceptual models to provide a theoretical framework to guide the development and integration of multiscale computational models, modeling of the Achilles tendon to date has tended to be piecemeal and focused on specific mechanical or biochemical issues. In this paper, we present a new conceptual model of Achilles tendon tissue homeostasis, and discuss this model in terms of existing computational models of tendon. This approach has the benefits of structuring the research on relevant computational modeling to date, while allowing us to identify new computational models requiring development. The critically important functional issue for tendon is that it is continually damaged during use and so has to be repaired. From this follows the centrally important issue of homeostasis of the load carrying collagen fibrils within the collagen fibers of the Achilles tendon. Collagen fibrils may be damaged mechanically-by loading, or damaged biochemically-by proteases. Upon reviewing existing computational models within this conceptual framework of the Achilles tendon structure and function, we demonstrate that a great deal of theoretical and experimental research remains to be done before there are reliably predictive multiscale computational model of Achilles tendon in health and disease.

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.