Rotator Cuff Tendon-bone Healing Research Articles

3D-printed Mg-incorporated PCL-based scaffolds improves rotator cuff tendon-bone healing through regulating macrophage polarization.

Introduction: Rotator cuff tear (RCT) is a common shoulder injury impacting mobility and quality of life, while traditional surgeries often result in poor healing. Tissue engineering offers a promising solution, with poly (ε-caprolactone) (PCL) being favored due to its slow degradation, biocompatibility, and non-toxicity. However, PCL lacks sufficient compression resistance. Incorporating Mg, which promotes bone growth and has antibacterial effects, could enhance RCT repair. Methods: The Mg-incorporated PCL-based scaffolds were fabricated using a 3D printing technique. The scaffolds were incorporated with different percentages of Mg (0%, 5%, 10%, 15%, and 20%). The osteogenic activities and anti-inflammatory properties of the scaffolds were evaluated in vitro using human osteoblasts and macrophages. The tissue ingrowth and biocompatibility of the scaffolds were assessed in vivo using a rat model of RCT repair. The ability of the scaffolds to enhance macrophage polarization towards the M2 subtype and inhibit inflammation signaling activation was also investigated. Results: It was found that when incorporated with 10% Mg, PCL-based scaffolds exhibited the optimal bone repairing ability in vitro and in vivo. The in vitro experiments indicated that the successfully constructed 10Mg/PCL scaffolds enhance osteogenic activities and anti-inflammatory properties. Besides, the in vivo studies demonstrated that 10Mg/PCL scaffolds promoted tissue ingrowth and enhanced biocompatibility compared to the control PCL scaffolds. Furthermore, the 10Mg/PCL scaffolds enhanced the macrophages' ability to polarize towards the M2 subtype and inhibited inflammation signaling activation. Discussion: These findings suggest that 3D-printed Mg-incorporated PCL scaffolds have the potential to improve RCT by enhancing osteogenesis, reducing inflammation, and promoting macrophage polarization. The incorporation of 10% Mg into PCL-based scaffolds provided the optimal combination of properties for RCT repair augmentation. This study highlights the potential of tissue engineering approaches in improving the outcomes of RCT repair and provides a foundation for future clinical applications.

Platelet-rich plasma-derived exosomes promote rotator cuff tendon-bone healing

BackgroundRotator cuff tear (RCT) is the most common type of shoulder joint injury, platelet-rich plasma-derived exosomes (PRP-exos) are highly promising in tissue repair and regeneration. The purpose of this study was to determine the function of PRP-exos in rotator cuff tendon-bone healing. MethodsPRP-exos were isolated from the rabbit whole blood by differential ultracentrifugation and characterized through transmission electron microscopy assay, nanoparticle tracking analysis, and western blotting. Alkaline phosphatase and Von Kossa staining were used to show tendon-derived stem cell (TDSC) differentiation. RT-qPCR and western blotting were performed to detect COL II, SOX-9, and TIMP-1. To determine the therapeutic effects of PRP-exos in vivo. Thirty New Zealand white rabbits were divided into control, model, and PRP-exos groups. The RCT animal model was constructed. The changes in tendon-bone tissue were determined by HE staining. Contents of COL-II, SOX-9, and TIMP-1 were determined by immunohistochemistry staining. ResultsPRP-exos were successfully isolated from rabbit blood. PRP-exos promoted TDSC proliferation and differentiation and also induced tendon-specific markers COL II, SOX-9, and TIMP-1 production. In vivo study revealed that PRP-exos promoted early healing of injured tendons. Rabbits treated with PRP-exos had better tissue arrangement in the tear site. Additionally, the contents of COL II, SOX-9, and TIMP-1 were also increased in the RCT rabbit model after PRP-exos treatment. ConclusionsPRP-exos enhanced tendon-bone healing by promoting TDSC proliferation and differentiation. This finding indicates that PRP-exos can serve as a promising strategy to treat rotator cuff tendon-bone healing.

Combination of autologous osteochondral and periosteum transplantation effectively promotes fibrocartilage regeneration at the tendon-bone junction of the rotator cuff in rabbits.

Rotator cuff tendon-bone healing often leads to scarring and low biomechanical strength, resulting in a tendency to re-tear. This study examined whether combining autologous osteochondral transplantation and periosteum transplantation increases fibrocartilage transition zone regeneration and improves biomechanical fixation. A total of 48 New Zealand white rabbits were divided into the periosteum, autologous osteochondral, combination of autologous osteochondral and periosteum, and control groups. The supraspinatus tendon was cut from the greater tuberosity and repaired by different transplants. A total of 12 rabbits were used for histological examination (haematoxylin and eosin staining, Masson's staining and Safranin-O staining) at 4, 8 and 12weeks after the repair, and 36 rabbits were used for biomechanical tests (maximal failure load and stiffness). At 4weeks following the operation, each group had a large tendon-bone gap with a small number of disordered collagen fibres. At 8weeks, the tendon-bone gap was smaller than that before the operation, and the tendon-bone gap in each experimental group was smaller with neater and denser collagen fibres and chondrocytes than in the control group, with the osteochondral combined periosteum group having the best results. At 12weeks, the typical tendon-bone transitional structure was observed in the osteochondral combined periosteum group, and more collagen fibres and chondrocytes were generated in each group. The osteochondral combined periosteum group had the largest staining area and the largest amount of cartilage. The maximum tensile strength and stiffness of each group increased over time. There was no significant difference in each group's maximum tensile strength and stiffness at 4weeks after the operation. However, the maximum tensile strength and stiffness of the osteochondral combined periosteum group at 8 and 12weeks after operation were significantly higher than those of other groups (P < 0.05). Histological and biomechanical results show that autologous osteochondral transplantation combined with periosteum transplantation can effectively promote the regeneration of fibrous cartilage in the tendon-bone junction of the rotator cuff. It is concluded that this technique is a new treatment method to promote tendon-bone healing in the rotator cuff.

Mechanical stimulation improves rotator cuff tendon-bone healing via activating IL-4/JAK/STAT signaling pathway mediated macrophage M2 polarization.

BackgroundIt is well known that appropriate mechanical stimulation benefits tendon-bone (T-B) healing, however, the mechanisms behind this are still uncovered completely. Here, we aimed to explore whether the IL-4/JAK/STAT signaling pathway mediated macrophage polarization was involved in mechanical stimulation induced T-B healing.MethodC57BL/6 mice rotator cuff (RC) repair model was established, and the mice were randomly allocated to the following group. 1. Mice were allowed for free cage activities after surgery (FC group); 2. Mice received treadmill running initiated on postoperative day 7 (TR group); 3. Mice only received a local injection of hydrogel containing IL-4 neutralizing antibody without postoperative intervention (FC ​+ ​AF-404-SP group); 4. Mice received a local injection of hydrogel containing IL-4 neutralizing antibody and postoperative treadmill running (TR ​+ ​AF-404-SP group). The expression of IL-4 within supraspinatus tendon (SST) enthesis was measured by Enzyme-linked immunosorbent assay (ELISA). In addition, the activation of JAK/STAT signaling pathway in macrophages and identification of macrophage phenotype at the RC insertion site was detected by Flow cytometry and qRT-PCR. T-B healing quality in this RC repair model was evaluated by histological staining, Micro-computed tomography (Micro-CT) scanning, and biomechanical testing.ResultIn this study, using the RC repair model, we confirmed that generation of IL-4, activation of the JAK/STAT signaling pathway in macrophages, the ability of macrophages to polarize towards M2 subtype, and T-B healing quality were significantly enhanced in TR group compared to FC group. When comparing FC ​+ ​AF-404-SP group with TR ​+ ​AF-404-SP group, it was found that the mechanical stimulation induced this effect was depleted following the blockade of the IL-4/JAK/STAT signaling pathway.ConclusionOur finding suggested that mechanical stimulation could accelerate T-B healing via activating the IL-4/JAK/STAT signaling pathway that modulates macrophages to polarize towards M2 subtype.The translational potential of this articleThis is the first study to reveal a significant role of mechanical stimulation in the IL-4/JAK/STAT signaling pathway activation and macrophage polarization during RC T-B healing, which highlights the IL-4/JAK/STAT signaling pathway as a potential target to mediate macrophage M2 polarization and improves T-B healing for RC repair.

Research progress of graft application in promoting rotator cuff tendon-bone healing

The incidence of re-tearing after rotator cuff repair is very high. The main reason is that the tendon-osseous junction after the operation is scar healed. In response to this problem, research in recent years has focused on the application of grafts, including cell transplantation, periosteum transplantation, cartilage transplantation, and biosynthetic transplantation. Cell transplantation is mainly a variety of stem cells from different sources. The current research has confirmed that it can achieve better results. The combined application of exosomes and stem cells may be the future development direction. Periosteum transplantation is a promising intervention method, but few clinical applications at present, and there are problems such as limited sources of materials and secondary trauma from the materials. Tissue engineered periostium and artificial bionic periostium may be alternatives to periosteal;cartilage transplantation can promote the regeneration of cartilage at the tendon-osseous junction and facilitate tendon-bone healing. However, there are also limited materials and secondary damage. There is no better solution to this problem. The slow degradation of inorganic composites and the poor effect of single use limit its application; biological derivatives have immunogenicity, poor biomechanics and other issues, there is currently no proper solution; organic synthetic grafts pay more attention to simulating the structure of the physiological tendon-osseointegration zone, and show good results in tendon-bone healing, and have good application prospects. In addition, most of the above-mentioned application research of different grafts stays at the cellular and animal level, and more research is needed in clinical application. This article briefly reviews the application status, advantages, disadvantages and development trends of the above-mentioned different grafts, in order to provide certain guidance for the clinical treatment of rotator cuff tears.

Effects of purified exosome product on rotator cuff tendon-bone healing in vitro and in vivo

Exosomes have multiple therapeutic targets, but the effects on healing rotator cuff tear (RCT) remain unclear. As a circulating exosome, purified exosome product (PEP) has the potential to lead to biomechanical improvement in RCT. Here, we have established a simple and efficient approach that identifies the function and underlying mechanisms of PEP on cell-cell interaction using a co-culture model in vitro. In the in vivo trial, adult female Sprague-Dawley rats underwent unilateral surgery to transect and repair the supraspinatus tendon to its insertion site with or without PEP. PEP promoted the migration and confluence of osteoblast cells and tenocytes, especially during direct cell-cell contact. Expression of potential genes for RCT in vitro and in vivo models were consistent with biomechanical tests and semiquantitative histologic scores, indicating accelerated strength and healing of the RC in response to PEP. Our observations suggest that circulating exosomes provide an effective option to improve the healing speed of RCT after surgical repair. The regeneration of enthesis following PEP treatment appears to be related to a mutually reinforcing relationship between direct cell-cell contact and PEP activity, suggesting a dual approach to the healing process.

Conditioned medium of human bone marrow-derived stem cells promotes tendon-bone healing of the rotator cuff in a rat model

Rotator cuff repair is a common surgery in sports medicine. During the surgery, torn tendon was re-fixed onto the bony surface. The majority of patients gain good results. However, re-tear occurs in some patients. The reason under this phenomenon is that the normal tendon-bone enthesis cannot be reconstructed. In order to strengthen the tendon-bone healing and promote enthesis regeneration, numerous manners are tested, among which stem cell related therapies are preferred. Stem cells, due to the ability of multi-lineage differentiation, are widely used in regenerative medicine. However, safety and ethics concerns limit its clinical use. Recent studies found that it is the secretome of stem cells that is biologically effective. On ground of this, we, in the current study, collected the conditioned medium of human bone marrow-derived stem cells (hBMSC-CM) and tested whether this acellular method could promote tendon-bone healing in a rat model of rotator cuff repair. By using histological, radiological, and biomechanical methods, we found that hBMSC-CM promoted tendon-bone healing of the rat rotator cuff. Then, we noticed that hBMSC-CM exerted an impact on macrophage polarization both in vivo and in vitro by inhibiting M1 phenotype and promoting M2 phenotype. Further, we proved that the benefit of hBMSC-CM on tendon-bone healing was related to its regulation on macrophage. Finally, we proved that, hBMSC-CM influenced macrophage polarization, which was, at least partially, related to Smad2/3 signaling pathway. Based on the experiments above, we confirmed the benefit of hBMSC-CM on tendon-bone healing, which relied on its immune-regulative property. Considering the accessibility and safety of acellular hBMSC-CM, we believe it is a promising candidate clinically for tendon-bone healing.

Clinical Effect of PRP with DPASB on Full-Thickness Rotator Cuff Tears and Its Role in VAS, SST, and Constant Scores of Patients.

The aim of the study is to probe the effects of platelet-rich plasma (PRP) plus double-row anchor suture bridge (DRASB) under shoulder arthroscopy on the postoperative VAS, SST and Constant scores, rotator cuff tendonbone healing, and re-tear of patients with full-thickness rotator cuff tear (RCT). A total of 60 patients with full-thickness RCT treated in our institution from August 2019 to January 2020 were picked and assigned to either group A (n = 30) or group B (n = 30) on a voluntary basis. Group B received DRASB under shoulder arthroscopy, whereas group A underwent DRASB under shoulder arthroscopy plus PRP. We compared the curative effects of both groups. Week 2, 4, 8, 12 after surgery and 6 months after surgery, VAS scores of patients in both groups declined saliently, whereas SST and Constant scores elevated, and the decrease/increase amplitude of patients in group A was sharply higher than that in group B (p < 0.05). At T2 and T3, abduction 90° external rotation, abduction 90° internal rotation, abduction and anteflexion in both groups increased strikingly, and group A harbored a brilliantly higher increase than group B (p < 0.05). At T2 and T3, serum NO and IL-6 contents were prominently dwindled in both groups, and group A held a plainly higher decrease than group B (p < 0.05). At T3, in comparison to group B, the rotator cuff tendonbone healing rate and quality of life scores in group A were higher (p < 0.05), whereas retear rate was dramatically lower (p < 0.05). DRASB under shoulder arthroscopy plus PRP therapy can blatantly meliorate the curative effect of patients with full-thickness tear, improve the shoulder joint function and tendonbone healing rate, reduce the postoperative pain degree and the incidence of retear, and can be more broadly promoted and applied clinically.

Bone marrow mesenchymal stem cell-derived exosomes promote rotator cuff tendon-bone healing by promoting angiogenesis and regulating M1 macrophages in rats

BackgroundRotator cuff tears (RCTs) often require reconstructive surgery. Tendon-bone healing is critical for the outcome of rotator cuff reconstruction, but the process of tendon-bone healing is complex and difficult. Mesenchymal stem cells (MSCs) are considered to be an effective method to promote tendon-bone healing. MSCs have strong paracrine, anti-inflammatory, immunoregulatory, and angiogenic potential. Recent studies have shown that MSCs achieve many regulatory functions through exosomes. The purpose of this study was to explore the role of bone marrow mesenchymal stem cell-derived exosomes (BMSC-Exos) in tendon-bone healing.MethodsOur study found that BMSC-Exos promote the proliferation, migration, and angiogenic tube formation of human umbilical vein endothelial cells (HUVECs). The mechanism by which BMSC-Exos achieve this may be through the regulation of the angiogenic signaling pathway. In addition, BMSC-Exos can inhibit the polarization of M1 macrophages and inhibit the secretion of proinflammatory factors by M1 macrophages. After rotator cuff reconstruction in rats, BMSC-Exos were injected into the tail vein to analyze their effect on the rotator cuff tendon-bone interface healing.ResultsIt was confirmed that BMSC-Exos increased the breaking load and stiffness of the rotator cuff after reconstruction in rats, induced angiogenesis around the rotator cuff endpoint, and promoted growth of the tendon-bone interface.ConclusionBMSC-Exos promote tendon-bone healing after rotator cuff reconstruction in rats by promoting angiogenesis and inhibiting inflammation.

High expression of VEGFA in MSCs promotes tendon-bone healing of rotator cuff tear via microRNA-205-5p.

To explore the role of vascular endothelial growth factor A (VEGFA) in tendon-bone healing of rotator cuff tear (RCT) and to investigate its possible mechanism. Mesenchymal stem cells (MSCs) were transfected with pcDNA-VEGFA. The viability of MSCs was detected by cell counting kit-8 (CCK-8) assay. Expression levels of type I and type II collagen in MSCs were detected by quantitative Real time-polymerase chain reaction (qRT-PCR). RCT was constructed in rats. Meanwhile, all rats were divided into MSCs group and MSCs-pcDNA-VEGFA group, respectively. Biomechanical test was performed to detect ultimate load of failure and stiffness in RCT rats. Dual-luciferase reporter gene assay was conducted to analyze the binding condition between microRNA-205-5p and VEGFA, which was further verified by Western blot and qRT-PCR. VEGFA overexpression significantly promoted viability and proliferation of MSCs. Expression levels of type I and type II collagen were significantly upregulated after VEGFA overexpression in MSCs. Biomechanical test showed that VEGFA overexpression in RCT rats remarkably elevated ultimate load of failure and stiffness. Dual-luciferase reporter gene assay elucidated that VEGFA was the target gene of microRNA-205-5p. Furthermore, VEGFA negatively regulated microRNA-205-5p expression. VEGFA promotes tendon-bone healing of RCT via inhibiting microRNA-205-5p expression.

Enhancement of rotator cuff tendon-bone healing using combined aligned electrospun fibrous membranes and kartogenin.

Rotator cuff tear (RCT) is a major challenging shoulder disease because the fibrocartilage zone is hard to regenerate in the enthesis. Electrospun membranes with aligned nanofibers can guide the ordered tissue regeneration and kartogenin (KGN) is able to stimulate chondrocyte differentiation of mesenchymal stem cells. In this study, we fabricated a functional engineered scaffold for regenerating tendon–bone enthesis in RCTs by taking advantage of both the structural guiding ability of aligned nanofibers and the biology effects of KGN. Polycaprolactone (PCL) fibrous membranes with aligned nanofibers loaded with or without KGN were fabricated using electrospinning and characterized using scanning electron microscopy (SEM). The release of KGN from PCL membranes and the effects of KGN on differentiation of mesenchymal stem cells were investigated. Results indicated that 100 μM KGN-loaded PCL (KGN-PCL) membranes significantly stimulated chondrogenic and tenogenic differentiation of rat bone marrow stromal cells. In addition, after PCL and 100 μM KGN-PCL membranes were applied to an acute rat RCT model, KGN-PCL membranes promoted fibrocartilage formation and collagen organization as well as increased cross-sectional area and load failure. In conclusion, PCL electrospun fibrous membranes with aligned nanofibers and KGN could be an effective tissue engineering scaffold to enhance tendon–bone healing in RCTs.

Paper #2 - The role of Scx+/Sox9+ progenitor cells in rotator cuff tendon-bone healing after injury in mice

Paper #2 - The role of Scx+/Sox9+ progenitor cells in rotator cuff tendon-bone healing after injury in mice

Human Amniotic Membrane Improves Healing in a Chronic, Massive Rotator Cuff Repair Model

Objectives:Rotator cuff tendon heals by fibrovascular scar that is weaker than native tissue leading to repairs that are prone to failure. Our objective was to investigate the ability of an amniotic membrane-derived human allograft to improve rotator cuff tendon-bone healing and skeletal muscle architecture in a chronic massive rotator cuff injury and repair model in rats. We hypothesized that application of human amniotic membrane to the tendon-bone interface at the time of repair will result in increased attachment strength and rotator cuff muscle fiber force secondary to improved bone formation and nthesis histomorphometry, less plasminogen activator inhibitor-1 (PAI-1) expression, and induced muscle repair gene expression.Methods:Eighty-five male Sprague-Dawley rats were allocated to one of four groups: (1) uninjured (U), (2) injury only (IO), (3) chronic injury and repair (CR), or (4) chronic injury and augmented repair (ER). The IO, CR, and ER groups underwent unilateral detachment of the supraspinatus and infraspinatus tendons with injection of the corresponding muscle with 3 u/kg Onabotulinum toxin A. Four weeks following injury, a surgical repair was performed in the CR and ER groups using transosseous suture fixation with human amniotic membrane applied to the tendon-bone repair site in the ER group. Animals were euthanized at four weeks following the repair. Biomechanical testing of the supraspinatus and infraspinatus tendon-bone complex and single fiber contractility testing of the supraspinatus muscle were performed. Microcomputed tomography was utilized to quantitate bone microstructure at the repair site. The healing tendon-bone interface was evaluated with histomorphometric quantification of fibrocartilage formation and collagen organization, and immunostaining with PAI-1. The rotator cuff muscle was evaluated with immunohistochemical localization for lipid deposition and total cross-sectional area. Real-time polymerase chain reaction evaluated relative expression of genes relevant to muscle repair. Statistical analysis was performed using a nonparametric Kruskal-Wallis test with significance set at p<0.05.Results:Augmentation with amniotic membrane did not lead to increased load-to-failure or stiffness compared to CR. The cross-sectional area, maximum isometric force, and specific force of individual supraspinatus muscle fibers were significantly greater with ER compared to CR (Figure 1). Microcomputed tomography revealed a larger volume of newly formed bone present at the bony footprint with ER compared to CR. Histomorphometric analysis demonstrated significantly greater fibrocartilage area and collagen organization at the healing tendon-bone insertion site with ER compared to CR at 4 week. Qualitatively, there was less PAI-1 immunostaining noted at the tendon-bone interface in the ER group. There was less lipid deposition and greater cross-sectional area of the rotator cuff muscle fibers in the ER group. Rotator cuff muscle gene expression with ER demonstrated a downregulation of apoptosis regulatory genes BCL2 and Caspase-3, adipogenesis regulatory genes FITM1 and FITM2, TNF-alpha and TGF-beta 3 compared to CR.Conclusion:Augmentation with human amniotic membrane in a chronic, massive rotator cuff injury and repair model led to greater bone formation, more organized tendon enthesis, induced muscle repair gene expression, and greater rotator cuff muscle fiber force secondary to less PAI-1 expression.

The effectiveness of demineralized cortical bone matrix in a chronic rotator cuff tear model

The purpose of this study was to assess the effect of demineralized bone matrix (DBM) on rotator cuff tendon-bone healing. The hypothesis was that compared with a commercially available dermal matrix scaffold, DBM would result in a higher bone mineral density and regenerate a morphologically superior enthesis in a rat model of chronic rotator cuff degeneration. Eighteen female Wistar rats underwent unilateral detachment of the supraspinatus tendon. Three weeks later, tendon repair was carried out in animals randomized into 3 groups: group 1 animals were repaired with DBM (n = 6); group 2 received augmentation with the dermal scaffold (n = 6); and group 3 (controls) underwent nonaugmented tendon-bone repair (n = 6). Specimens were retrieved at 6 weeks postoperatively for histologic analysis and evaluation of bone mineral density. No failures of tendon-bone healing were noted throughout the study. All groups demonstrated closure of the tendon-bone gap with a fibrocartilaginous interface. Dermal collagen specimens exhibited a disorganized structure with significantly more abnormal collagen fiber arrangement and cellularity than in the DBM-based repairs. Nonaugmented repairs exhibited a significantly higher bone mineral density than in DBM and the dermal collagen specimens and were not significantly different from control limbs that were not operated on. The application of DBM to a rat model of chronic rotator cuff degeneration did not improve the composition of the healing enthesis compared with nonaugmented controls and a commercially available scaffold. However, perhaps the most important finding of this study was that the control group demonstrated a similar outcome to augmented repairs.

What's new in shoulder and elbow surgery.

The sources for this annual update on shoulder and elbow surgery were presentations and symposia at meetings of the American Orthopaedic Society for Sports Medicine (Specialty Day, Dallas, Texas, February 16, 2002), the Arthroscopy Association of North America (Specialty Day, Dallas, Texas, February 16, 2002; Twenty-first Annual Meeting, Seattle, Washington, April 19-22, 2002; and Twentieth Fall Course, San Antonio, Texas, November 29-December 2, 2002), the American Academy of Orthopaedic Surgeons (Sixty-ninth Annual Meeting, Dallas, Texas, February 13-17, 2002), and the American Shoulder and Elbow Surgeons (Specialty Day, Dallas, Texas, February 16, 2002, and Eighteenth Annual Meeting, Napa, California, September 2001). ### Rotator Cuff #### Basic Science Several studies have employed sophisticated animal models to investigate rotator cuff repair and healing. Coleman reported on a chronic rotator cuff injury and repair model involving sheep. Infraspinatus contractile forces and histological findings were evaluated at various times following either immediate or delayed tendon repair. Longer delays to repair led to greater decreases in force and more modest recovery following repair. Muscle biopsies confirmed progressive fatty infiltration that was partially reversed after tendon repair in the group with a six-week delay before repair but not in the group with an eighteen-week delay before repair. This model has important implications regarding the recovery of strength following the repair of chronic rotator cuff tears. Rodeo presented a study on growth factor-enhanced rotator cuff tendon-bone healing in a sheep model. Histological analysis demonstrated greater new-bone and fibrovascular tissue formation in the treated animals. A substantial increase in attachment strength was noted in the treated animals at twelve weeks. The study demonstrates the ability of a growth factor to influence changes at the tendon-bone interface. MacGilivray evaluated the augmentation of rotator cuff repairs with a bioabsorbable scaffold in a goat model. Biomechanical testing showed no significant improvement in load to failure when a tendon …