Reconstruction of the tendon-bone insertion with decellularized tendon-bone composite grafts: comparison with conventional repair

A retrospective comparative study of surgical outcomes following femoral fascia patching and iliotibial ligament bony patching for primary irreparable rotator cuff tears in a geriatric population

INTRODUCTION

We performed two surgical techniques for primary irreparable rotator cuff tears: a patch technique using the femoral fascia as a graft (F technique) and a patch technique using the bony iliotibial ligament (I technique). We then evaluated the outcomes of both surgical methods.

MATERIALS AND METHODS

This study included 28 patients who were diagnosed with primary irreparable rotator cuff tears from April 2008 to April 2014. Among them, 13 underwent the F technique, whereas 15 underwent the I technique. Each clinical shoulder score was evaluated preoperatively and 2 years after surgery. The cuff integrity was evaluated via magnetic resonance imaging 2 years after surgery, with cases suffering a retear after surgery undergoing retear site examination. In group I, computed tomography (CT) was performed 3-4 months after surgery to investigate the bony part of the patch and bony fusion of the footprint.

RESULTS

Both groups showed significant improvements in the pre- and postoperative mean clinical score values. Group I had significantly better postoperative scores than group F. Postoperative retear rates were 33.3% and 76.9% for groups I and F, respectively, with group I having a significantly lower retear rate (P = 0.03). All 5 retears in group I were located at the suture between the residual rotator cuff and the graft, whereas 7 of the 10 retears in group F were located at the fixation of the graft and footprint and the remaining 3 were central. CT results in group I showed that all 15 patients had bony fusion between the bony part of the patch and the footprint.

CONCLUSION

The I technique was significantly superior to the F technique in terms of postoperative clinical scores and retear rates, suggesting its advantage for rotator cuff tissue reconstruction.

Advances focusing on the application of decellularization methods in tendon-bone healing

BACKGROUND

The tendon or ligament is attached to the bone by a triphasic but continuous area of heterogeneous tissue called the tendon-bone interface (TBI). The rapid and functional regeneration of TBI is challenging owing to its complex composition and difficulty in self-healing. The development of new technologies, such as decellularization, has shown promise in the regeneration of TBI. Several ex vivo and in vivo studies have shown that decellularized grafts and decellularized biomaterial scaffolds achieved better efficacy in enhancing TBI healing. However further information on the type of review that is available is needed.

AIM OF THE REVIEW

In this review, we discuss the current application of decellularization biomaterials in promoting TBI healing and the possible mechanisms involved. With this work, we would like to reveal how tissues or biomaterials that have been decellularized can improve tendon-bone healing and to provide a theoretical basis for future related studies.

KEY SCIENTIFIC CONCEPTS OF THE REVIEW

Decellularization is an emerging technology that utilizes various chemical, enzymatic and/or physical strategies to remove cellular components from tissues while retaining the structure and composition of the extracellular matrix (ECM). After decellularization, the cellular components of the tissue that cause an immune response are removed, while various biologically active biofactors are retained. This review further explores how tissues or biomaterials that have been decellularized improve TBI healing.

Engineering an enthesis-like graft for rotator cuff repair: An approach to fabricate highly biomimetic scaffold capable of zone-specifically releasing stem cell differentiation inducers

Rotator cuff (RC) attaches to humerus across a triphasic yet continuous tissue zones (bone-fibrocartilage-tendon), termed "enthesis". Regrettably, rapid and functional enthesis regeneration is challenging after RC tear. The existing grafts bioengineered for RC repair are insufficient, as they were engineered by a scaffold that did not mimic normal enthesis in morphology, composition, and tensile property, meanwhile cannot simultaneously stimulate the formation of bone-fibrocartilage-tendon tissues. Herein, an optimized decellularization approach based on a vacuum aspiration device (VAD) was developed to fabricate a book-shaped decellularized enthesis matrix (O-BDEM). Then, three recombinant growth factors (CBP-GFs) capable of binding collagen were synthesized by fusing a collagen-binding peptide (CBP) into the N-terminal of BMP-2, TGF-β3, or GDF-7, and zone-specifically tethered to the collagen of O-BDEM to fabricate a novel scaffold (CBP-GFs/O-BDEM) satisfying the above-mentioned requirements. After ensuring the low immunogenicity of CBP-GFs/O-BDEM by a novel single-cell mass cytometry in a mouse model, we interleaved urine-derived stem cell-sheets into this CBP-GFs/O-BDEM to bioengineer an enthesis-like graft. Its high-performance on regenerating enthesis was determined in a canine model. These findings indicate this CBP-GFs/O-BDEM may be an excellent scaffold for constructing enthesis-like graft to patch large/massive RC tears, and provide breakthroughs in fabricating graded interfacial tissue.

Basic science approaches to common hand surgery problems

The field of hand surgery is constantly evolving to meet challenges of populations with increasing age and higher demands for active living. While our surgical care has improved over the last decades, it seems that future major improvement in outcomes of clinical treatment will come through advances in biologics and the translation of major discoveries in basic science. This article aims to provide an update on where basic science solutions may answer some of the most critical issues in hand surgery, with a focus on augmentation of tissue repair.

Biomimetic strategies for tendon/ligament-to-bone interface regeneration

Tendon/ligament-to-bone healing poses a formidable clinical challenge due to the complex structure, composition, cell population and mechanics of the interface. With rapid advances in tissue engineering, a variety of strategies including advanced biomaterials, bioactive growth factors and multiple stem cell lineages have been developed to facilitate the healing of this tissue interface. Given the important role of structure-function relationship, the review begins with a brief description of enthesis structure and composition. Next, the biomimetic biomaterials including decellularized extracellular matrix scaffolds and synthetic-/natural-origin scaffolds are critically examined. Then, the key roles of the combination, concentration and location of various growth factors in biomimetic application are emphasized. After that, the various stem cell sources and culture systems are described. At last, we discuss unmet needs and existing challenges in the ideal strategies for tendon/ligament-to-bone regeneration and highlight emerging strategies in the field.

Reconstruction of large chronic rotator cuff tear can benefit from the bone-tendon composite autograft to restore the native bone-tendon interface

Purpose

We designed a paired controlled study to investigate the advantages of using bone–tendon composite autograft to reconstruct chronic rotator cuff tear compared with primary repair and provide some evidence to use the bone–tendon composite autograft.

Method

Thirty-eight Sprague–Dawley rats were used. The native bone–tendon junctions of supraspinatus and Achilles tendon insertion from two rats were harvested for gross and histological observation. Another thirty-six rats had bilateral supraspinatus tenotomy from the great tuberosity. Three weeks later, primary repair (simple tendon pullout direct repair to bone) was performed on one side and the other side was reconstructed using an Achilles–calcaneus composite autograft from the ipsilateral leg. Nine rats were sacrificed for biomechanical testing and another three were sacrificed for histological evaluation at 3, 6, and 9 weeks after surgery, respectively.

Results

The Achilles–calcaneus composite autograft group showed significantly better biomechanical characteristics at 3 and 6 weeks in terms of maximum load and stiffness. Tissue histology demonstrated an organised extracellular matrix, a clear tidemark, and distinct fibrocartilage layers in the composite graft group, similar to those of the native bone–tendon interface. Additionally, clear bone-to-bone healing and tendon-to-tendon healing were observed. By contrast, the conventional primary repair could not regenerate the structure of the native bone–tendon interface.

Conclusions

Bone–tendon autograft for chronic rotator cuff reconstruction is superior to the primary repair regarding biomechanical property and histological structure. Our study may provide some evidence in support of the reconstruction of a chronic rotator cuff tear using bone–tendon composite autografts in clinical practice.

The Translational potential of this article

The current study finds the bone-tendon autograft can restore the normal bone-tendon interface, which can not regenerate after repair and is the key factor affecting re-tear. The bone-tendon autografts from our body can be the candidates for rotator cuff tear reconstruction especially the large to massive rotator cuff tear in the future to reduce the re-tear after rotator cuff tear.

Remnant Tendon Preservation Enhances Rotator Cuff Healing: Remnant Preserving Versus Removal in a Rabbit Model

PURPOSE

To assess whether anatomic repair preserving remnant tendon tissue can enhance tendon-to-bone healing biomechanically and histologically in a rabbit rotator cuff tear model.

METHODS

In this controlled laboratory study, bilateral infraspinatus tenotomy from the greater tuberosity, with remnant tendon on the footprint, was performed in 26 New Zealand white rabbits. An open transosseous technique was used to perform bilateral infraspinatus tendon repair 1 week later. Preservation and removal of the remaining tendon were performed on the left and right sides, respectively. Seven rabbits each were killed humanely for biomechanical testing and 6 rabbits each were killed humanely for histologic evaluation at 4 and 12 weeks.

RESULTS

Significantly superior biomechanical properties were shown in the remnant tissue-preservation group at 4 and 12 weeks in terms of maximum load (89.6 ± 24.3 N vs 68.2 ± 20.7 N at 4 weeks, P = .048; 120.8 ± 27.5 N vs 93.3 ± 25.1 N at 12 weeks, P = .035) and stiffness (25.3 ± 3.4 N/mm vs 17.7 ± 5.2 N/mm at 4 weeks, P = .009; 26.7 ± 5.2 N/mm vs 19.4 ± 5.2 N/mm at 12 weeks, P < .001). Improved bone-tendon interface histologic maturity scores (14.8 ± 0.9 vs 8.2 ± 1.5 at 4 weeks, P = .027; 16.8 ± 0.7 vs 10.5 ± 1.4 at 12 weeks, P = .027) and large metachromasia areas (0.117 ± 0.053 mm² vs 0.032 ± 0.017 mm² at 4 weeks, P = .022; 0.14 ± 0.046 mm² vs 0.037 ± 0.016 mm² at 12 weeks, P = .007) were obtained in the preservation group compared with the removal group at 4 and 12 weeks.

CONCLUSIONS

This study showed that preserving remnant tissue in anatomic repair can significantly improve rotator cuff healing compared with remnant tissue removal on the footprint in terms of biomechanical properties, bone-tendon interface histologic maturity scores, and metachromasia at 4 and 12 weeks after repair in a rabbit rotator cuff tear model.

CLINICAL RELEVANCE

The results suggest that preservation of remnant tissue on the footprint containing the native bone-tendon interface, when present, may be a better option for rotator cuff healing in rotator cuff repair surgery.

Next Generation Tissue Engineering of Orthopedic Soft Tissue-to-Bone Interfaces

Soft tissue-to-bone interfaces are complex structures that consist of gradients of extracellular matrix materials, cell phenotypes, and biochemical signals. These interfaces, called entheses for ligaments, tendons, and the meniscus, are crucial to joint function, transferring mechanical loads and stabilizing orthopedic joints. When injuries occur to connected soft tissue, the enthesis must be re-established to restore function, but due to structural complexity, repair has proven challenging. Tissue engineering offers a promising solution for regenerating these tissues. This prospective review discusses methodologies for tissue engineering the enthesis, outlined in three key design inputs: materials processing methods, cellular contributions, and biochemical factors.

Biomimetic tendon extracellular matrix composite gradient scaffold enhances ligament-to-bone junction reconstruction

Management of ligament/tendon-to-bone-junction healing remains a formidable challenge in the field of orthopedic medicine to date, due to deficient vascularity and multi-tissue transitional structure of the junction. Numerous strategies have been employed to improve ligament-bone junction healing, including delivery of stem cells, bioactive factors, and synthetic materials, but these methods are often inadequate at recapitulating the complex structure-function relationships at native tissue interfaces. Here, we developed an easily-fabricated and effective biomimetic composite to promote the regeneration of ligament-bone junction by physically modifying the tendon extracellular matrix (ECM) into a Random-Aligned-Random composite using ultrasound treatment. The differentiation potential of rabbit bone marrow stromal cells on the modified ECM were examined in vitro. The results demonstrated that the modified ECM enhanced expression of chondrogenesis and osteogenesis-associated epigenetic genes (Jmjd1c, Kdm6b), transcription factor genes (Sox9, Runx2) and extracellular matrix genes (Col2a1, Ocn), resulting in higher osteoinductivity than the untreated tendon ECM in vitro. In the rabbit anterior cruciate ligament (ACL) reconstruction model in vivo, micro-computed tomography (Micro-CT) and histological analysis showed that the modified Random-Aligned-Random composite scaffold enhanced bone and fibrocartilage formation at the interface, more efficaciously than the unmodified tendon ECM. Therefore, these results demonstrated that the biomimetic Random-Aligned-Random composite could be a promising scaffold for ligament/tendon-bone junction repair.

STATEMENT OF SIGNIFICANCE

The native transitional region consists of several distinct yet contiguous tissue regions, composed of soft tissue, non-calcified fibrocartilage, calcified fibrocartilage, and bone. A stratified graft whose phases are interconnected with each other is essential for supporting the formation of functionally continuous multi-tissue regions. Various techniques have been attempted to improve adherence of the ligament/tendon graft to bone, including utilization of stem cells, growth factors and biomaterials, but these methods are often inadequate at recapitulating the complex structure-function relationships at native tissue interfaces. Here, we developed an easily-fabricated and effective biomimetic composite to promote the regeneration of ligament-bone junction by physically modifying the tendon extracellular matrix (ECM) into a Random-Aligned-Random composite using ultrasound treatment. The modified ECM enhanced expression of chondrogenesis and osteogenesis-associated epigenetic genes expression in vitro. In the rabbit anterior crucial ligament reconstruction model in vivo, results showed that the modified Random-Aligned-Random composite enhances the bone and fibrocartilage formation in the interface, proving to be more efficient than the unmodified tendon ECM. Therefore, these results demonstrated that the biomimetic Random-Aligned-Random composite could be a promising scaffold for ligament/tendon-bone junction repair.

Modifying the strength and strain concentration profile within collagen scaffolds using customizable arrays of poly-lactic acid fibers

The tendon-to-bone junction is a highly specialized tissue which dissipates stress concentrations between mechanically dissimilar tendon and bone. Upon injury, the local heterogeneities across this insertion are not regenerated, leading to poor functional outcomes such as formation of scar tissue at the insertion and re-failure rates exceeding 90%. Although current tissue engineering methods are moving towards the development of spatially-graded biomaterials to begin to address these injuries, significant opportunities remain to engineer the often complex local mechanical behavior of such biomaterials to enhance their bioactivity. Here, we describe the use of three-dimensional printing techniques to create customizable arrays of poly-lactic acid (PLA) fibers that can be incorporated into a collagen scaffold under development for tendon bone junction repair. Notably, we use additive manufacturing concepts to generate arrays of spatially-graded fibers from biodegradable PLA that are incorporated into collagen scaffolds to create a collagen-PLA composite. We demonstrate the ability to tune the mechanical performance of the fiber-scaffold composite at the bulk scale. We also demonstrate the incorporation of spatially-heterogeneous fiber designs to establish non-uniform local mechanical performance of the composite biomaterial under tensile load, a critical element in the design of multi-compartment biomaterials for tendon-to-bone regeneration applications. Together, this work highlights the capacity to use multi-scale composite biomaterials to control local and bulk mechanical properties, and provides key insights into design elements under consideration for mechanically competent, multi-tissue regeneration platforms.

Rotator cuff repair using an original iliotibial ligament with a bone block patch: preliminary results with a 24-month follow-up period

BACKGROUND

Our first-line choice of surgical method for massive shoulder rotator cuff tears not amenable to primary repair is a patching method that uses a graft consisting of a section of the iliotibial band with an attached bone block. The objective of this study was to examine the functional and structural results.

METHODS

The study included 5 patients who were not eligible for primary repair, received iliotibial band autografts with an attached bone block, and could be monitored for 2 years or more. The grafting method involved suturing the ligament part of the graft to the remaining rotator cuff and fixing the bone part to the greater tubercle of the humerus by means of a suture-bridge technique. Clinical evaluation was performed for 24 months postoperatively. Postoperative structural evaluation was performed using computed tomography at 3 to 4 months and magnetic resonance imaging at 6, 12, and 24 months.

RESULTS

A clear improvement was seen at the final clinical evaluation. Fusion of the bone graft with the greater tubercle of the humerus was confirmed on computed tomography in all patients. No retearing was observed on magnetic resonance imaging at the 24-month point, and the thickness of the ligament part of the graft was maintained.

CONCLUSION

The patching method using an iliotibial band with an attached bone block as the graft enabled good reconstruction of the rotator cuff, including the greater tubercle footprint. Moreover, good clinical results were seen at 24 months.

Single-Stage Flexor Tendon Grafting: Refining the Steps

Single-stage tendon grafting for reconstruction of zone I and II flexor tendon injuries is a challenging procedure in hand surgery. Careful patient selection, strict indications, and adherence to sound surgical principles are mandatory for return of digital motion.

A Comparative Study on the Biomechanical and Histological Properties of Bone-to-Bone, Bone-to-Tendon, and Tendon-to-Tendon Healing: An Achilles Tendon-Calcaneus Model in Goats

BACKGROUND

Surgical repair around the bone-tendon insertion (BTI) may involve bone-to-bone (BB), bone-to-tendon (BT), or tendon-to-tendon (TT) reattachment with varying healing outcome.

HYPOTHESIS

The repair of Achilles tendon-calcaneus (ATC) by reattachment of homogeneous tissue (BB or TT) would heal faster, with respect to tensile properties at the healing complex, than those of reattachment of heterogeneous tissues (BT) over time.

STUDY DESIGN

Controlled laboratory study.

METHODS

Forty-seven adolescent male Chinese goats were divided into BB, BT, and TT groups. Osteotomy of the calcaneus, reattachment of Achilles tendon to the calcaneus after removal of the insertion, and tenotomy of the Achilles tendon were performed to simulate BB, BT, and TT repair, respectively. The ATC healing complexes were harvested at 6, 12, or 24 weeks postoperatively. Mechanical and morphological properties of the healing ATC complexes were assessed by tensile testing and qualitative histology, respectively. The contralateral intact ATC complex was used as the control.

RESULTS

Failure load of BT was 33.4% lower than that of TT (P = .0243) at week 12. Ultimate strength of BT was 50.2% and 45.3% lower than that of TT at weeks 12 (P = .0002) and 24 (P = .0001), respectively. Tissue morphological characteristics of the BB and TT groups showed faster remodeling. The BT group showed limited regeneration of fibrocartilage zone and excessive formation of fibrous tissue at the healing interface.

CONCLUSION

BTI repair between homogeneous tissues (BB and TT healing) showed better healing quality with respect to mechanical and histological assessments than did healing between heterogeneous tissues (BT healing).

CLINICAL RELEVANCE

Anatomic reconstruction of ATC complex injury may be a primary concern when selecting the proper surgical approach. However, it is recommended to select fracture fixation (BB) or tendon repair (TT) instead of bone-tendon reattachment (BT) if possible to ensure better outcome at the healing interface.