Biologic approaches to enhance rotator cuff healing after injury

Editorial Commentary: Biologic Augmentation of Rotator Cuff Repair: Platelet-Rich Plasma May Be of Significant Benefit, Whereas Atelocollagen Cannot Be Recommended

The field of orthobiologics continues to advance at a rapid pace and theoretically holds some promise to augment the biologic healing response in rotator cuff repair (RCR). However, the clinical evidence for use of substances such as platelet-rich plasma (PRP) for RCR remains inconclusive. Atelocollagen, as a synthetic collagen substitute, has been proposed as another alternative to provide more collagen substrate for healing, but outcomes data with this technique is lacking. In contrast, (biologic) PRP has been well studied, does not show adverse outcomes, and has been shown to improve healing of large to massive tears, as well as RCR outcomes. As biologic augmentation options continue to push the envelope on indications, due diligence is required to carefully examine options for safety and efficacy. Evolutions in RCR should also continue to motivate sports medicine surgeons and researchers to seek out further innovations to improve patient outcomes. That said, PRP outcome improvement for RCR is not definitive and requires further study. RCR can humble even the best of surgeons and demands that we continue to look for ways to improve outcomes.

Does timing influence rehabilitation outcomes in arthroscopic rotator cuff repair with biceps rerouting? a prospective randomized study

BACKGROUND

Arthroscopic rotator cuff repair with biceps rerouting (ABR) has emerged as a reliable option for treating large posterosuperior rotator cuff tears (RCTs). This study aims to compare functional and structural outcomes of early vs. delayed motion rehabilitation protocols following ABR.

METHODS

A total of 101 patients with semirigid, large, posterosuperior RCTs undergoing ABR were randomized into 2 groups: group I (early motion) with 53 patients (34 females, 19 males) and group II (delayed motion) with 48 patients (31 females, 17 males). In group I, the mean age was 63.9 years (range, 46-79), and in group II, it was 65.4 years (range, 43-78). The mean follow-up periods for group I and group II were 16.2 and 15.5 months, respectively. Preoperative and postoperative assessments were conducted at 3, 6, and 12 months, with structural integrity assessed with magnetic resonance imaging at a minimum follow-up of 12 months. Statistical analyses were performed to compare outcomes between the 2 groups.

RESULTS

Both groups demonstrated significant improvements in visual analog scale score (group I: 4.0-1.6, group II: 3.7-1.4, P = .501), University of California-Los Angeles shoulder score (group I: 21.5-31.4, group II: 22.4-30.6, P = .331), and acromiohumeral interval (group I: 8.2 mm-9.1 mm, group II: 8.6 mm-9.5 mm, P = .412), with no statistically or clinically meaningful differences. Active range of movements (ROM) were not significantly different between groups, except for active forward flexion at 3 months (group I: 140.1°, group II: 119.2°, P = .006), that was not shown to be translated clinically into differences in function or healing between the groups in this study. Notably, retear rates were similar between groups (group I: 22.6%, group II: 20.8%, P = .826).

CONCLUSION

This study's findings reveal no clinically discernible differences in active range of motion at 1-year follow-up between patients who underwent ABR for semirigid, large, posterosuperior RCTs and were assigned to either early or delayed motion protocols. Notably, the early motion group demonstrated a plateau in maximum range of movement improvement as early as 3 months postsurgery. Based on these results, implementing an early motion protocol is recommended as an effective approach in the postoperative rehabilitation following ABR.

Bioactive Patch for Rotator Cuff Repairing via Enhancing Tendon-to-Bone Healing: A Large Animal Study and Short-Term Outcome of a Clinical Trial

Tissue engineering has demonstrated its efficacy in promoting tissue regeneration, and extensive research has explored its application in rotator cuff (RC) tears. However, there remains a paucity of research translating from bench to clinic. A key challenge in RC repair is the healing of tendon-bone interface (TBI), for which bioactive materials suitable for interface repair are still lacking. The umbilical cord (UC), which serves as a vital repository of bioactive components in nature, is emerging as an important source of tissue engineering materials. A minimally manipulated approach is used to fabricate UC scaffolds that retain a wealth of bioactive components and cytokines. The scaffold demonstrates the ability to modulate the TBI healing microenvironment by facilitating cell proliferation, migration, suppressing inflammation, and inducing chondrogenic differentiation. This foundation sets the stage for in vivo validation and clinical translation. Following implantation of UC scaffolds in the canine model, comprehensive assessments, including MRI and histological analysis confirm their efficacy in inducing TBI reconstruction. Encouraging short-term clinical results further suggest the ability of UC scaffolds to effectively enhance RC repair. This investigation explores the mechanisms underlying the promotion of TBI repair by UC scaffolds, providing key insights for clinical application and translational research.

Inlay Scaffold Augmentation of Rotator Cuff Repairs Enhances Histologic Resemblance to Native Enthesis in Animal Studies: A Systematic Review

PURPOSE

To investigate the outcomes of inlay positioned scaffolds for rotator cuff healing and regeneration of the native enthesis after augmentation of rotator cuff tendon repairs in preclinical studies.

METHODS

A literature search was performed using the PubMed, Embase, and Cumulative Index to Nursing and Allied Health Literature databases according to Preferred Reporting Items for Systematic Reviews and Meta-analyses guidelines. Preclinical studies reporting on outcomes after inlay tendon augmentation in rotator cuff repair were included. Preclinical study quality was assessed using an adapted version of the Gold Standard Publication Checklist for animal studies. The level of evidence was defined based on the inclusion of clinical analyses (grade A), biomechanical analyses (grade B), biochemical analyses (grade C), semiquantitative analyses (grade D), and qualitative histologic analyses (grade E).

RESULTS

Thirteen preclinical studies met the inclusion criteria. Quality assessment scores ranged from 4 to 8 points, and level-of-evidence grades ranged from B to E. Sheep/ewes were the main animal rotator cuff tear model used (n = 7). Demineralized bone matrix or demineralized cortical bone was the most commonly investigated scaffold (n = 6). Most of the preclinical evidence (n = 10) showed qualitative or quantitative differences regarding histologic, biomechanical, and biochemical outcomes in favor of interpositional scaffold augmentation of cuff repairs in comparison to controls.

CONCLUSIONS

Inlay scaffold positioning in preclinical studies has been shown to enhance the healing biology of the enthesis while providing histologic similarities to its native 4-zone configuration.

CLINICAL RELEVANCE

Although onlay positioned grafts and scaffolds have shown mixed results in preclinical and early clinical studies, inlay scaffolds may provide enhanced healing and structural support in comparison owing to the ability to integrate with the bone-tendon interface.

Efficacy of platelet-rich plasma in rotator cuff repair: systematic review and meta-analysis

OBJECTIVE

To analyze the efficacy and safety after the application of platelet-rich-plasma (PRP) as an adjuvant in arthroscopic rotator cuff repairs.

MATERIAL AND METHODS

A bibliographic search of the literature of prospective studies with level of evidence one or two was carried out from January 2004 to December 2021, including studies that compare the functional and re-tear results after arthroscopic cuff repair rotator with or without PRP.

RESULTS

A total of 281 articles were identified, of which 14 met the inclusion criteria. The overall re-rupture rate was 24%. In the PRP group, a decrease in the re-rupture rate and better functional results were demonstrated, although these differences were not significant.

CONCLUSIONS

Adjuvant treatment with PRP has shown promising results, although there is not yet enough evidence to provide a clear advantage for routine use in clinical practice.

[Translated article] Efficacy of platelet-rich plasma in rotator cuff repair: Systematic review and meta-analysis

OBJECTIVE

To analyse the efficacy and safety after the application of platelet-rich-plasma (PRP) as an adjuvant in arthroscopic rotator cuff repairs.

MATERIAL AND METHODS

A bibliographic search of the literature of prospective studies with level of evidence one or two was carried out from January 2004 to December 2021, including studies that compare the functional and re-tear results after arthroscopic cuff repair rotator with or without PRP.

RESULTS

A total of 281 articles were identified, of which 14 met the inclusion criteria. The overall re-rupture rate was 24%. In the PRP group, a decrease in the re-rupture rate and better functional results were demonstrated, although these differences were not significant.

CONCLUSIONS

Adjuvant treatment with PRP has shown promising results, although there is not yet enough evidence to provide a clear advantage for routine use in clinical practice.

Local Injection of Rapamycin-Loaded Pcl-Peg Nanoparticles for Enhanced Tendon Healing in Rotator Cuff Tears via Simultaneously Reducing Fatty Infiltration and Drug Toxicity

As a common cause of shoulder pain, rotator cuff tears (RCTs) are difficult to treat clinically because of their unsatisfactory prognosis due to the fatty infiltration caused by muscle-derived stem cells (MDSCs). Previous studies have found that rapamycin (RAPA) can inhibit fatty infiltration. However, systemic administration of RAPA may cause complications such as infection and nausea, while local administration of RAPA may lead to the cytotoxicity of tendon cells, affecting the healing of rotator cuffs. In this study, biocompatible and clinically approved polycaprolactone-polyethylene glycol (PCL-PEG) is formulated into an injectable nanoparticle for the sustained release of RAPA. The results indicate that the RAPA/PCL-PEG nanoparticles (NPs) can efficiently prolong the release of RAPA and significantly reduce the cytotoxicity of tendon cells caused by RAPA. The study of the fatty infiltration model in rats with delayed rotator cuff repair shows that weekly intraarticular injection of RAPA/PCL-PEG NPs can more effectively reduce the fatty infiltration and muscle atrophy of rat rotator cuffs and leads to better mechanical properties and gait improvements than a daily intraarticular injection of RAPA. These findings imply that local injection of RAPA/PCL-PEG NPs in the shoulder joints can be a potential clinical option for RCTs patients with fatty infiltration.

Clinical outcomes of rotator cuff repair with subacromial bursa reimplantation: a retrospective cohort study

Background

The subacromial bursa has been found to be a rich, local, source of mesenchymal stem cells but is removed for visualization during rotator cuff repair. Reimplantation of this tissue may improve rotator cuff healing. The purpose of this study is to evaluate clinical outcomes of rotator cuff repair with and without subacromial bursa reimplantation.

Methods

Patients aged 37-77 with a full-thickness or near full-thickness supraspinatus tears underwent arthroscopic transosseous-equivalent double row rotator cuff repair. In patients prior to July 2019, the subacromial bursa was resected for visualization, and discarded. In patients after July 2019, the subacromial bursa was collected using a filtration device connected to an arthroscopic shaver and reapplied to the bursal surface of the tendon at the completion of the rotator cuff repair. Rotator cuff integrity was evaluated via magnetic resonance imaging on bursa patients at 6 months postoperatively. Minimum 18-month clinical outcomes (Single Assessment Numeric Evaluation, American Shoulder and Elbow Surgeons, patient satisfaction) were compared between bursa and nonbursa cohorts.

Results

A total of 136 patients were included in the study (control n = 110, bursa n = 26). Preoperative demographics and tear characteristics were not different between groups. Average follow-up was significantly longer in the control group (control: 3.2 ± 0.7 years; bursa: 1.8 ± 0.3 years; P < .001). The control group showed a significantly higher Single Assessment Numeric Evaluation score (control: 87.9 ± 15.8, bursa: 83.6 ± 15.1, P = .037) that did not meet minimum clinically important difference. The American Shoulder and Elbow Surgeons and patient satisfaction scores were similar between the groups. Symptomatic retears were not significantly different between groups (control: 9.1%, bursa 7.7%, P = .86). Seven patients in the control group underwent reoperation (6.4%), compared to 0 patients in the bursa group (0%, P = .2). Six-month postoperative magnetic resonance images obtained on bursa patients demonstrated 85% rotator cuff continuity (n = 17/20) as defined via Sugaya classification.

Conclusion

Augmentation of rotator cuff repair with bursal tissue does not appear to have negative effects, and given the accessibility and ease of harvest of this tissue, further research should be performed to evaluate its potential for improved tendon healing or clinical outcomes.

Biphasic Interpositional Allograft for Rotator Cuff Repair Augmentation Is Safe in an Ovine Model

PURPOSE

To perform a preclinical histologic assessment of a biphasic acellular interpositional cancellous allograft in an ovine model of rotator cuff repair (RCR) designed to better understand its safety profile and effects on tendon healing after RCR.

METHODS

Thirty skeletally mature sheep with clinically normal shoulders with an artificially created degenerative infraspinatus tendon tear were randomized to control and treatment groups. Animals were euthanized at 3 weeks, 6 weeks, and 12 weeks. After gross dissection, rotator cuff specimens were fixed with formalin and polymerized for sectioning and staining. Blinded histologic scores evaluated inflammatory cell infiltrates, signs of degradation, particulate debris, collagen arrangement, neovascularization, and enthesis qualitative measures.

RESULTS

There were no treatment specimens that exhibited histologic signs of a significant infection, inflammatory infiltrate, or foreign body reaction such as granuloma or fibrous capsule formation. Histologic scores in all categories were not significantly different at all time points, including the primary end point mean cumulative inflammatory score (control: 3.66 ± 1.21 vs treated: 4.33 ± 1.51, P = .42), when comparing the treatment and control RCR groups. In general, the degree of tendon healing and host tissue response was essentially equivalent between the 2 groups with observation of low overall levels of inflammation and progressive improvements in collagen organization, reduced tenocyte activity, and fibrocartilaginous enthesis reformation.

CONCLUSIONS

This histologic study demonstrated the use of a biphasic interpositional allograft for RCR augmentation in an ovine model does not generate an inflammatory response or foreign body reaction. Use of the biphasic interpositional allograft resulted in a histological profile that was essentially equivalent to that of a standard RCR at 3-, 6-, and 12-week postoperative timepoints. These findings suggest that a biphasic interpositional allograft is safe for further clinical investigation in humans before broader clinical application.

CLINICAL RELEVANCE

Patch augmentation of RCR is a popular technique that has shown clinical success in improving the likelihood of a successful repair in patients at elevated risk for retear. Newer augmentation technologies are being developed to address the biology at the interface between the bone and soft tissue where failure typically occurs.

Drug Delivery Approaches to Improve Tendon Healing

Tendon injuries disrupt the transmission of forces from muscle to bone, leading to chronic pain, disability, and a large socioeconomic burden. Tendon injuries are prevalent; there are over 300,000 tendon repair procedures a year in the United States to address acute trauma or chronic tendinopathy. Successful restoration of function after tendon injury remains challenging clinically. Despite improvements in surgical and physical therapy techniques, the high complication rate of tendon repair procedures motivates the use of therapeutic interventions to augment healing. While many biological and tissue engineering approaches have attempted to promote scarless tendon healing, there is currently no standard clinical treatment to improve tendon healing. Moreover, the limited efficacy of systemic delivery of several promising therapeutic candidates highlights the need for tendon-specific drug delivery approaches to facilitate translation. This review article will synthesize the current state-of-the-art methods that have been used for tendon-targeted delivery through both systemic and local treatments, highlight emerging technologies used for tissue-specific drug delivery in other tissue systems, and outline future challenges and opportunities to enhance tendon healing through targeted drug delivery.

The Plug-Type Patch Results in Immediate and Postoperative Advantages in Graft-to-Bone Integration for Bridging Massive Rotator Cuff Tears in a Chronic Rabbit Model

BACKGROUND

Various patches have been used to bridge massive rotator cuff tears (MRCTs) by reconnecting the cuff tendons to the humeral head, but the outcomes continue to be suboptimal. Notably, the graft-bone junction is a vulnerable site for failure, which requires optimization in patch design and techniques to enhance initial and postoperative fixation strength at the graft-bone interface.

HYPOTHESIS

The plug-type patch (Plug-Pat) through intratunnel fixation would optimize mechanical characteristics in initial graft-to-bone fixation and subsequently improve postoperative biomechanical and histological properties in graft-to-bone healing when compared with the routine rectangular patch (Rect-Pat).

STUDY DESIGN

Controlled laboratory study.

METHODS

A total of 60 mature male New Zealand White rabbits underwent acute rotator cuff defects to create chronic models with MRCTs. The fascia lata autograft was then harvested to prepare a Plug-Pat, which was distally rooted in the bone tunnel and proximally sutured to native tendons in a horizontal mattress fashion to reconnect the humeral head and cuff tendons. The control group was repaired with a routine Rect-Pat that was secured onto the bone surface for graft-bone fixation. After surgery, the cuff-graft-bone complexes of rabbits in both groups were harvested immediately (0 weeks) for time-zero initial fixation strength and refreshed contact area assessment, and at 6 or 12 weeks for postoperative biomechanical and histological evaluation.

RESULTS

The Plug-Pat significantly enhanced initial fixation strength in comparison with the Rect-Pat (mean ± SD; failure load, 36.79 ± 4.53 N vs 24.15 ± 2.76 N; P < .001) and decreased failure at the graft-bone interface of the construct at 0 weeks, with a significantly increased refreshed bone bed contact area (52.63 ± 2.97 mm² vs 18.28 ± 1.60 mm²; P < .001) between the graft and bone. At 6 and 12 weeks postoperatively, the Plug-Pat similarly resulted in greater failure load (43.15 ± 4.53 N vs 33.74 ± 2.58 N at 6 weeks; P = .001; 76.65 ± 5.04 N vs 58.17 ± 5.06 N at 12 weeks; P < .001) and stiffness (10.77 ± 2.67 N/mm vs 8.43 ± 0.86 N/mm at 6 weeks; P = .066; 16.98 ± 2.47 N/mm vs 13.21 ± 1.66 N/mm at 12 weeks; P = .011), with less specimen failure at the graft-bone interface than the Rect-Pat. In histological analyses, the Plug-Pat had a higher postoperative graft-bone integration score than the Rect-Pat, showing a more mature intratunnel healing interface with fibrocartilage tidemark formation, improved collagen properties, and more oriented cells when compared with those at the surface healing interface in the Rect-Pat.

CONCLUSION

The Plug-Pat enhanced initial fixation strength and enlarged the refreshed contact area for graft-bone connection at time zero and subsequently improved postoperative biomechanical properties and graft-bone integration at the graft-bone healing interface when compared with the Rect-Pat.

CLINICAL RELEVANCE

The Plug-Pat using intratunnel fixation may be a promising strategy for patch design to optimize its initial and postoperative graft-bone connection for bridging reconstruction of MRCTs.

Tendon transfers for massive rotator cuff tears

Massive rotator cuff tears (MRCTs) present a particular challenge due to high rates of retear that can range from 18 to 94%, failure of healing after repair, and potential for irreparability.

Management of MRCTs must take into consideration the patient's characteristics, clinical examamination and expectation, number and quality of muscle tendons units involved.

Conservative treatment, arthroscopic long head of the biceps tenotomy, cuff debridement, partial repair, and superior capsule reconstruction are viable solutions to treat selected patients.

The goal of tendon transfers is to achieve stable kinematic by restoring rotational strength and force coupling of the shoulder joint.

The ideal candidate is a young, motivated patient with small degenerative changes of the glenohumeral joint, a massive irreparable cuff tear, significant atrophy, fatty infiltration, and functional deficit.

Patients with posterosuperior massive tears have impaired shoulder function with external rotation weakness and eventually lag sign If the teres minor is affected.

Latissimus dorsi transfer is the most used with results lasting for long follow-up and lower Trapezius transfer is becoming a surgical option. For anterosuperior tears, there is still controversial if pectoralis major is the best option when compared to latissimus dorsi although this last has a similar vector force with the supraspinatus tendon.

Complications associated with tendon transfers include neurovascular injury, infection, and rupture of the transferred tendon.

Histologic and biomechanical evaluation of the thoracolumbar fascia graft for massive rotator cuff tears in a rat model

BACKGROUND

Fascial autografts, which are easily available grafts, have provided a promising option in patients with massive rotator cuff tears. However, no fascial autografts other than the fascia lata have been reported, and the exact healing process of the fascia-to-bone interface is not well understood. The objective of this study is to histologically and biomechanically evaluate the effect of the thoracolumbar fascia (TLF) on fascia-to-bone healing.

METHODS

A total of 88 rats were used in this study. Eight rats were killed at the beginning to form an intact control group, and the other rats were divided randomly into 2 groups (40 rats per group): the TLF augmentation group (TLF group) and the repair group (R group). The right supraspinatus was detached, and a 3 × 5 mm defect of the supraspinatus was created. The TLF was used to augment the torn supraspinatus in the TLF group, whereas in the R group, the torn supraspinatus was repaired in only a transosseous manner. Histology and biomechanics were assessed at 1, 2, 4, 8, and 16 weeks postoperatively.

RESULTS

The modified tendon maturation score of the TLF group was higher than that of the R group at 8 weeks (23.00 ± 0.71 vs. 24.40 ± 0.89, P = .025) and 16 weeks (24.60 ± 0.55 vs. 26.40 ± 0.55, P ≤ .001). The TLF group showed a rapid vascular reaction, and the peak value appeared at 1 week. Later, the capillary density decreased, and almost no angiogenesis was observed at 8 weeks postoperatively. Immunohistochemistry results demonstrated a significantly higher percentage of collagen I in the TLF group at 4, 8, and 16 weeks (24.78% ± 2.76% vs. 20.67% ± 2.11% at 4 weeks, P = .046; 25.46% ± 1.77% vs. 21.49% ± 2.33% at 8 weeks, P = .026; 34.77% ± 2.25% vs. 30.01% ± 3.17% at 16 weeks, P = .040) postoperatively. Biomechanical tests revealed that the ultimate failure force in the TLF group was significantly higher than that in the R group at the final evaluation (29.13 ± 2.49 N vs. 23.10 ± 3.47 N, P = .022).

CONCLUSIONS

The TLF autograft can promote a faster biological healing process and a better fixation strength. It could be used as an alternative reinforcement or bridging patch when the fascia lata is not appropriate or available for superior capsule reconstruction (SCR).

Translational therapy from preclinical animal models for muscle degeneration after rotator cuff injury

Chronic rotator cuff tears are debilitating diseases which significantly affect patients’ quality of life and pose substantial financial burden to the society. The intraoperative reparability of injured tendon and postoperative probability of tendon retear are highly associated with the quality of torn muscles, specifically, the severity of muscle atrophy and fatty infiltration. Animal models that reproduce the characteristic muscle pathology after rotator cuff injury have been developed and used to provide insight into the underlying biology and pathophysiology. In this review, we briefly summarize the current information obtained from preclinical animal studies regarding the degenerative change of cuff muscle subsequent to tendon release and/or suprascapular nerve denervation. Importantly, we focus on the potential translational therapeutic targets or agents for the prevention or reversal of muscle atrophy and fatty infiltration. While further studies are warranted to assess the safety and efficacy of novel therapies derived from these preclinical animal research, we believe that their clinical translation for the treatment of rotator cuff disorders is on the horizon.

The Translational potential of this article

Novel therapeutic strategies described in this review from preclinical animal studies hold a great translational potential for preventing or reversing rotator cuff muscle pathology, while further assessments on their safety and efficacy are warranted.

Regeneration of Chronic Rotator Cuff Tear in a Rabbit Model: Synergetic Benefits of Human Umbilical Cord Blood-Derived Mesenchymal Stem Cells, Polydeoxyribonucleotides, and Microcurrent Therapy

Objective

To investigate synergic therapeutic effects of combined injection of intralesional mesenchymal stem cells derived from human umbilical cord blood (UCB-MSCs) and polydeoxyribonucleotide (PDRN) combined with microcurrent therapy (MIC) on full thickness rotator cuff tendon tear (FTRCTT) in rabbit models.

Methods

Thirty-two rabbit models were assigned to 4 different groups. FTRCTT in the supraspinatus tendon was created. After 6 weeks, 4 types of procedures (0.2 mL normal saline injection, group 1 (G1-NS); 0.2 mL SC injection, group 2 (G2-MSC); 0.2 mL SC and weekly four injections of 0.2 mL PDRN with sham MIC, group 3 (G3-MSC+PDRN+sham MIC); and 0.2 mL SC and weekly four injections of 0.2 mL PDRN with MIC for four weeks, group 4 (G4-MSC+PDRN+MIC)) were performed in FTRCTT. Gross morphologic and histological changes of proliferating cell nuclear antigen (PCNA), vascular endothelial growth factor (VEGF) and platelet endothelial cell adhesion molecule (PECAM-1) and motion analysis were performed.

Results

There was a significant difference in gross morphologic changes between baseline and week 4 posttreatment in group 4 compared to the other three groups (p = 0.01). In groups 3 and 4, all parameters of histochemical and motion analysis have been found to be significantly greater than the ones in groups 1 and 2 (p < 0.05). In group 4, PCNA-, VEGF-, and PECAM-1-stained cells, as well as walking distance, were significantly greater than the ones in group 3 (p < 0.05).

Conclusion

The treatment with UCB-MSCs and PDRN combined with MIC might be the most effective in rabbit models' traumatic FRTCTT.

Segmentally Demineralized Cortical Bone With Stem Cell-Derived Matrix Promotes Proliferation, Migration and Differentiation of Stem Cells in vitro

A recent study has shown that demineralized cortical bone (DCB) did not improve the healing of tendon-bone interface. Considering that there is a gradient of mineral content in the tendon-bone interface, we designed a segmentally demineralized cortical bone (sDCB) scaffold with two different regions: undemineralized cortical bone section within the scaffold (sDCB-B) and complete demineralized cortical bone section within the scaffold (sDCB-D), to mimic the natural structure of the tendon-bone interface. Furthermore, the extracellular matrix (ECM) from tendon-derived stem cells (TDSCs) was used to modify the sDCB-D region of sDCB to construct a novel scaffold (sDCB-ECM) for enhancing the bioactivity of the sDCB-D. The surface topography, elemental distribution, histological structure, and surface elastic modulus of the scaffold were observed using scanning electron microscopy, energy-dispersive X-ray spectroscopy, Fourier transform infrared spectroscopy, histological staining and atomic force microscopy. Cell proliferation of bone marrow mesenchymal stem cells (BMSCs) and TDSCs cultured on scaffolds was evaluated using the Cell Counting kit-8, and cell viability was assessed by Live/Dead cell staining. Cell morphology was detected by fluorescent staining. The ability of the scaffolds to recruit stem cells was tested using transwell migration assay. The expression levels of bone-, cartilage- and tendon-related genes and proteins in stem cells were assessed by the polymerase chain reaction and western blotting. Our results demonstrated that there was a gradient of Ca and P elements in sDCB, and TDSC-derived ECM existed on the surface of the sDCB-D region of sDCB. The sDCB-ECM could promote stem cell proliferation and migration. Moreover, the sDCB-B region of sDCB-ECM could stimulate osteogenic and chondrogenic differentiation of BMSCs, and the sDCB-D-ECM region of sDCB-ECM could stimulate chondrogenic and tenogenic differentiation of TDSCs when compared to DCB. Our study indicated that sDCB-ECM might be a potential bioscaffold to enhance the tendon-bone interface regeneration.

Systematic Review of Platelet-Rich Plasma for Rotator Cuff Repair: Are We Adhering to the Minimum Information for Studies Evaluating Biologics in Orthopaedics?

Background

The therapeutic efficacy of orthobiologic therapies for rotator cuff repair is difficult to evaluate owing to reporting inconsistences. In response, the Minimum Information for Studies Evaluating Biologics in Orthopaedics (MIBO) guidelines were developed to ensure standard reporting on orthobiologic therapies.

Purpose

To systematically review clinical studies evaluating platelet-rich plasma (PRP) for full-thickness rotator cuff repair and adherence to MIBO guidelines.

Study Design

Scoping review; Level of evidence, 4.

Methods

A search was performed according to the PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) guidelines using PubMed, EMBASE, and the Cochrane Library databases. Inclusion criteria were clinical studies reporting on rotator cuff tears (≥1 cm) surgically repaired with PRP. Patient demographics, biologic intervention, and adherence to the MIBO guidelines were systematically reviewed.

Results

A total of 19 studies (1005 patients) were included in this review. Across all studies, 58.5% of the MIBO checklist items for PRP were reported. Out of 47 checklist items, 19 were reported in over 85% of studies, whereas 22 were reported in less than half of studies. Details of whole-blood processing and characteristics, as well as PRP processing and characteristics, were reported inconsistently, and no study provided adequate information to enable the precise replication of preparation protocols for PRP.

Conclusion

This systematic review highlights the current reporting deficiencies within the scientific literature of important variables for evaluating PRP for full-thickness rotator cuff repair. There was widespread variability among published studies that evaluate PRP for this application and, more specifically, studies were limited by inconsistent universal reporting of whole-blood and PRP processing and postprocessing characteristics. To improve our understanding of biologic efficacy and to promote repeatability, stricter adherence to the MIBO guidelines is necessary. We propose that the checklist limitations be addressed and that modification of the MIBO guidelines be considered to improve the reporting of individual components within certain categories.

Safety and Efficacy of Autologous Dermal Fibroblast Injection to Enhance Healing After Full-Thickness Rotator Cuff Repair: First-in-Human Pilot Study

Background:

There is growing interest in various biological supplements to improve tendon healing in patients after arthroscopic rotator cuff repair. The ideal biological supplement to strengthen rotator cuff remains unknown.

Purpose:

To assess the safety and efficacy of autologous cultured dermal fibroblast (ADF) injection on tendon-to-bone healing in patients after arthroscopic rotator cuff repair.

Study Design:

Case series; Level of evidence, 4.

Methods:

Included were 6 patients who underwent arthroscopic rotator cuff repair between June 2018 and March 2020; all patients had a full-thickness rotator cuff tear (>2 cm) involving the supraspinatus and infraspinatus tendons. The patients were injected with ADF between the repaired tendon and footprint during arthroscopic rotator cuff repair using the suture bridge technique. The safety of ADFs and the procedure was evaluated at 5 weeks postoperatively, and the anatomical healing of the repaired tendon was accessed at 6 months postoperatively using magnetic resonance imaging and at 12 months using ultrasonography. Outcomes including shoulder range of motion (ROM), visual analog scale (VAS) for pain, and functional scores were measured at 6 and 12 months postoperatively.

Results:

Adverse reactions to ADF injection were not observed at 6 months after surgery. VAS and functional scores at 6 and 12 months postoperatively were significantly improved compared with preoperative scores (all P < .05). However, there was no significant difference on any ROM variable between preoperative and postoperative measurements at 6 and 12 months (all P > .05). No healing failure was found at 6 and 12 months postoperatively.

Conclusion:

There was no adverse reaction to ADF injection, and all patients had successful healing after rotator cuff repair. A simple and easily accessible ADF injection may be a novel treatment option for increasing the healing capacity of torn rotator cuff tendons. Further clinical research is needed to verify the study results.

ADSC-Based Cell Therapies for Musculoskeletal Disorders: A Review of Recent Clinical Trials

Recently published clinical trials involving the use of adipose-derived stem cells (ADSCs) indicated that approximately one-third of the studies were conducted on musculoskeletal disorders (MSD). MSD refers to a wide range of degenerative conditions of joints, bones, and muscles, and these conditions are the most common causes of chronic disability worldwide, being a major burden to the society. Conventional treatment modalities for MSD are not sufficient to correct the underlying structural abnormalities. Hence, ADSC-based cell therapies are being tested as a form of alternative, yet more effective, therapies in the management of MSDs. Therefore, in this review, MSDs subjected to the ADSC-based therapy were further categorized as arthritis, craniomaxillofacial defects, tendon/ligament related disorders, and spine disorders, and their brief characterization as well as the corresponding conventional therapeutic approaches with possible mechanisms with which ADSCs produce regenerative effects in disease-specific microenvironments were discussed to provide an overview of under which circumstances and on what bases the ADSC-based cell therapy was implemented. Providing an overview of the current status of ADSC-based cell therapy on MSDs can help to develop better and optimized strategies of ADSC-based therapeutics for MSDs as well as help to find novel clinical applications of ADSCs in the near future.

Mesenchymal stem cell-derived exosomes: therapeutic implications for rotator cuff injury

Rotator cuff injuries are a common clinical condition of the shoulder joint. Surgery that involves reattaching the torn tendon to its humeral head bony attachment has a somewhat lower success rate. The scar tissue formed during healing of the rotator cuff leads to poor tendon-related mechanical properties. To promote healing, a range of genetic interventions, as well as cell transplantation, and many other techniques have been explored. In recent years, the therapeutic promise of mesenchymal stem cells (MSCs) has been well documented in animal and clinical studies. Some data have suggested that MSCs can promote angiogenesis, reduce inflammation and cell proliferation and increase collagen deposition. These functions are likely paracrine effects of MSCs, particularly mediated through exosomes. Here, we review the use of MSCs-related exosomes in tissues and organs. We also discuss their potential utility for treating rotator cuff injuries, and explore the underlying mechanisms of their effects.

Current Biological Strategies to Enhance Surgical Treatment for Rotator Cuff Repair

Rotator cuff tear is one of the most common shoulder problems encountered by orthopedic surgeons. Due to the slow healing process and high retear rate, rotator cuff tear has distressed millions of people all around the world every year, especially for the elderly and active athletes. This disease significantly impairs patients' motor ability and reduces their quality of life. Besides conservative treatment, open and arthroscopic surgery contributes a lot to accelerate the healing process of rotator cuff tear. Currently, there are many emerging novel treatment methods to promote rotator cuff repair. A variety of biological stimulus has been utilized in clinical practice. Among them, platelet-rich plasma, growth factors, stem cells, and exosomes are the most popular biologics in laboratory research and clinical trials. This review will focus on the biologics of bioaugmentation methods for rotator cuff repair and tendon healing, including platelet-rich plasma, growth factors, exosomes and stem cells, etc. Relevant studies are summarized in this review and future research perspectives are introduced.

In Vivo Imaging of Fibroblast Activity Using a 68Ga-Labeled Fibroblast Activation Protein Alpha (FAP-α) Inhibitor: Study in a Mouse Rotator Cuff Repair Model

BACKGROUND

Rotator cuff repair site failure is a well-established clinical concern. Tendon-to-bone healing is initiated by inflammatory mediators followed by matrix synthesis by fibroblasts. The kinetics of fibroblast accumulation and activity are currently poorly understood.

METHODS

Ninety-six mice underwent supraspinatus tendon repair. Six were used for imaging using a novel 68Gallium (Ga)-labeled fibroblast activation protein alpha (FAP-α) inhibitor and positron emission tomography-computed tomography (PET/CT) at days 0 (before surgery), 3, 7, 14, and 28. Sixty-eight animals were divided into 4 groups to be evaluated at 3, 7, 14, or 28 days. Twenty-two native shoulders from mice without surgery were used as the control group (intact tendon). Six animals from each group were used for histological analysis; 6 from each group were used for evaluation of fibroblastic response-related gene expression; and 10 mice each from the intact, 14-day, and 28-day groups were used for biomechanical testing.

RESULTS

There was minimal localization of 68Ga-labeled FAP-α inhibitor in the shoulders at day 0 (before surgery). There was significantly increased uptake in the shoulders with surgery compared with the contralateral sides without surgery at 3, 7, and 14 days. 68Ga-labeled FAP-α inhibitor uptake in the surgically treated shoulders increased gradually and peaked at 14 days followed by a decrease at 28 days. Gene expression for smooth muscle alpha (α)-2 (acta2), FAP-α, and fibronectin increased postsurgery followed by a drop at 28 days. Immunohistochemical analysis showed that FAP-α-positive cell density followed a similar temporal trend, peaking at 14 days. All trends matched closely with the PET/CT results. Biomechanical testing demonstrated a gradual increase in failure load during the healing process.

CONCLUSIONS

68Ga-labeled FAP-α inhibitor PET/CT allows facile, high-contrast in vivo 3-dimensional imaging of fibroblastic activity in a mouse rotator cuff repair model.

CLINICAL RELEVANCE

Noninvasive imaging of activated fibroblasts using labeled radiotracers may be a valuable tool to follow the progression of healing at the bone-tendon interface.

Rotator cuff anchor repair: Histological changes associated with the recovering mechanical properties in a rabbit model

Rotator cuff anchor repair is an increasingly common surgical procedure but the failure rate remains high. In order to improve surgical outcomes, a better understanding of postrepair histological and cellular responses at the tendon-bone attachment site (enthesis) is needed. We examined operated shoulders from 42 New Zealand female white rabbits. The animals underwent unilateral supraspinatus detachment followed by anchor repair a week later. To assess enthesis reformation, fibrocartilage staining area and the number of chondrocytes or nonchondrocytes were quantified at 0, 1, 2, and 4 weeks postrepair. Using linear regression, we correlated these results with the load to failure and stiffness recorded during mechanical testing of the tendons. Fibrocartilage staining and chondrocyte number increased during the first 2 weeks of enthesis formation. Between 2 and 4 weeks, fibrocartilage staining plateaued while chondrocyte number decreased. The presence of nonchondrocytes remained similar between 0- and 1-week postrepair but then decreased abruptly at 2 weeks. There was a linear correlation between fibrocartilage staining area and load to failure as well as stiffness. Nonchondrocyte number negatively correlated with stiffness. Early plateau of fibrocartilage staining and decrease in chondrocytes between 2 and 4 weeks postrepair suggest a blunted enthesis formation response in our animal model.

Hierarchically Demineralized Cortical Bone Combined With Stem Cell-Derived Extracellular Matrix for Regeneration of the Tendon-Bone Interface

BACKGROUND

Poor healing of the tendon-bone interface after rotator cuff repair is one of the main causes of surgical failure. Previous studies demonstrated that demineralized cortical bone (DCB) could improve healing of the enthesis.

PURPOSE

To evaluate the outcomes of hierarchically demineralized cortical bone (hDCB) coated with stem cell-derived extracellular matrix (hDCB-ECM) in the repair of the rotator cuff in a rabbit model.

STUDY DESIGN

Controlled laboratory study.

METHODS

Tendon-derived stem cells (TDSCs) were isolated, cultured, and identified. Then, hDCB was prepared by the graded demineralization procedure. Finally, hDCB-ECM was fabricated via 2-week cell culture and decellularization, and the morphologic features and biochemical compositions of the hDCB-ECM were evaluated. A total of 24 rabbits (48 samples) were randomly divided into 4 groups: control, DCB, hDCB, and hDCB-ECM. All rabbits underwent bilateral detachment of the infraspinatus tendon, and the tendon-bone interface was repaired with or without scaffolds. After surgery, 8 rabbits were assessed by immunofluorescence staining at 2 weeks, and the others were assessed by micro-computed tomography (CT) examination, immunohistochemical staining, histological staining, and biomechanical testing at 12 weeks.

RESULTS

TDSCs were identified to have universal stem cell characteristics including cell markers, clonogenicity, and multilineage differentiation. The hDCB-ECM contained 3 components (bone, partial DCB, and DCB coated with ECM) with a gradient of calcium and phosphorus elements, and the ECM had stromal cell-derived factor 1, biglycan, and fibromodulin. Macroscopic observations demonstrated the absence of infection and rupture around the enthesis. The results of immunofluorescence staining showed that hDCB-ECM promoted stromal cell recruitment. Results of micro-CT analysis, immunohistochemical staining, and histological staining showed that hDCB-ECM enhanced bone and fibrocartilage formation at the tendon-bone interface. Biomechanical analysis showed that the hDCB-ECM group had higher ultimate tensile stress and Young modulus than the DCB group.

CONCLUSION

The administration of hDCB-ECM promoted healing of the tendon-bone interface.

CLINICAL RELEVANCE

hDCB-ECM could provide useful information for the design of scaffolds to repair the tendon-bone interface, and further studies are needed to determine its effectiveness.

Engineering multi-tissue units for regenerative Medicine: Bone-tendon-muscle units of the rotator cuff

Our body systems are comprised of numerous multi-tissue units. For the musculoskeletal system, one of the predominant functional units is comprised of bone, tendon/ligament, and muscle tissues working in tandem to facilitate locomotion. To successfully treat musculoskeletal injuries and diseases, critical consideration and thoughtful integration of clinical, biological, and engineering aspects are necessary to achieve translational bench-to-bedside research. In particular, identifying ideal biomaterial design specifications, understanding prior and recent tissue engineering advances, and judicious application of biomaterial and fabrication technologies will be crucial for addressing current clinical challenges in engineering multi-tissue units. Using rotator cuff tears as an example, insights relevant for engineering a bone-tendon-muscle multi-tissue unit are presented. This review highlights the tissue engineering strategies for musculoskeletal repair and regeneration with implications for other bone-tendon-muscle units, their derivatives, and analogous non-musculoskeletal tissue structures.

Rotator cuff repair techniques: Current concepts

Arthroscopic rotator cuff repair is being performed by an ever-increasing number of surgeons. With an ageing population and growing patient expectations it is crucial that clinical outcomes are optimised. Anatomical reduction of the tendon back to its footprint with minimal tension contributes to this, but this can only be achieved if key biomechanical factors are taken into consideration. In this review of the technical aspects of a rotator cuff repair, we focus on: (1) patient positioning, (2) biomechanical principles, (3) optimal visualisation, and (4) repair techniques for both anterior and postero-superior tears.

Celecoxib significantly reduces opioid use after shoulder arthroplasty

BACKGROUND

The opioid crisis has illuminated the risks of opioid use for pain management, with renewed interest in reducing opioid consumption after common orthopedic procedures. Anti-inflammatory medication is an important component of multimodal pain management for patients undergoing orthopedic surgery. The purpose of this study was to evaluate the effect of celecoxib on pain control and opioid use after shoulder surgery.

METHODS

Patients scheduled for either total shoulder replacement (group 1) or rotator cuff repair (group 2) were candidates for the study. The exclusion criteria included allergy to celecoxib, coagulopathy, use of anticoagulants, baseline use of long-acting opioids, and a history of medical conditions such as myocardial infarction or stroke. Consenting patients were randomized by type of procedure using block randomization to receive either placebo or celecoxib 1 hour prior to the procedure and for 3 weeks postoperatively. The primary outcome measure assessed was opioid utilization as measured by morphine-equivalent dose (MED). Secondary outcome measures included pain scores at 3 and 6 weeks postoperatively. Data were analyzed using multiple linear regression.

RESULTS

Of 1081 patients scheduled for either total shoulder replacement or rotator cuff repair from February 2014 to February 2018, 78 were enrolled for arthroplasty (group 1, with 39 receiving celecoxib and 39 receiving placebo) and 79 were enrolled for rotator cuff repair (group 2, with 40 receiving celecoxib and 39 receiving placebo). Compared with the placebo arm, patients prescribed celecoxib took fewer MEDs by -168 (95% confidence interval [CI], -272 to -64; P < .01) at 3 weeks in the total population and by -197.7 (95% CI, -358 to -38; P = .02) in the arthroplasty group. Similarly, at 6 weeks, total MEDs used was -199 (95% CI, -356 to -42; P < .01) in the total population and -270 (95% CI, -524 to -16; P = .04) in the arthroplasty group. No statistically significant differences in opioid consumption were found between study arms in the cuff repair group, at either 3 or 6 weeks. Of note, preoperative opioid use was statistically associated with higher levels of opioid use in the total population and group 1 at 3 and 6 weeks (P < .01 for all) but not in group 2 (P > .05 for both).

CONCLUSIONS

Use of morphine equivalents was statistically significantly less at 3 and 6 weeks in patients who took celecoxib in the total population and in the arthroplasty group. Patients prescribed celecoxib for 3 weeks after shoulder surgery took less opioid medication for pain at 3 and 6 weeks. Multimodal pain control using celecoxib is an effective way to reduce postoperative opioid use in shoulder arthroplasty patients. Preoperative opioid use is associated with higher levels of opioid use after shoulder arthroplasty.

Healing rates after rotator cuff repair for patients taking either celecoxib or placebo: a double-blind randomized controlled trial

Background

Use of anti-inflammatory medications (NSAIDs) is an important component of multimodal pain control after orthopedic procedures to avoid opioid overutilization and abuse. However, the deleterious effects of NSAIDs on tendon healing are of particular concern in rotator cuff repair (RCR). The purpose of this study was to evaluate the effect of celecoxib or placebo on healing rates after RCR when administered in the perioperative and immediate postoperative period using MRI evaluation at one year postoperatively. A secondary aim was to determine whether clinical differences existed between patients with intact or non-intact repairs.

Methods

Patients aged ≤65 years with partial- or full-thickness rotator cuff tear (<25x25 mm) were randomized to receive celecoxib 400 mg or placebo 1 hour before the procedure and 200mg bid for 3 weeks postoperatively. All patients were treated as clinically indicated at the time of surgery and followed standard postoperative protocol. Repair integrity was evaluated with MRI using the Sugaya classification for repair integrity. Data were analyzed using multivariable logistic regression by intent to treat.

Results

Seventy-nine patients were enrolled; 21 were lost to follow-up, 6 did not have cuff repair, 5 were revised, and 2 declined follow-up, leaving 45 patients with one-year follow-up. Five of these patients did not complete MRI, leaving 40 patients for review. Eighteen of 20 patients (90%) who received celecoxib completed all doses of study medication as did 15 of 20 patients (75%) who received placebo. The patient groups were similar for demographics, clinical results, and healing rate. After adjusting for tear size, no statistically significant difference in healing rate was found between groups, with 10 of 20 celecoxib patients (50%) having intact repair at 1 year compared with 14 of 20 placebo patients (70%) (OR = 0.53, 95% CI: 0.14, 2.08, P = 0.35).

Conclusion

Half of the patients who received celecoxib had an intact repair compared with 70% intact repair for patients receiving placebo. Although not statistically significant in this small study, larger studies are needed to clarify this important clinical concern. The authors do not recommend use of celecoxib for postoperative pain control after RCR.

The role of adipose derived stem cells in the treatment of rotator cuff tears: from basic science to clinical application

Over the last decade, regenerative medicine has become increasingly popular throughout the scientific community. The poor healing capacity at the tendon-bone interface makes the rotator cuff an appealing target for biologic agents. Adipose derived stem cells are mesenchymal cells with the capacity for self-renewal and multipotential differentiation. They have been recently proposed, both in isolation and as adjuvants to existing surgical therapies, for the treatment of rotator cuff tears. Several studies have been carried out in this research field, starting from the biological characteristics of adipose derived stem cells, their preparation and culture, up to the application in the experimental field on animal models and on humans. The purpose of this study was to provide a state of the art about the current basic science and clinical literature for the effectiveness of adipose derived stem cells in the treatment of rotator cuff tears.

A 3-Dimensional Bioprinted Scaffold With Human Umbilical Cord Blood-Mesenchymal Stem Cells Improves Regeneration of Chronic Full-Thickness Rotator Cuff Tear in a Rabbit Model

BACKGROUND

Chronic full-thickness rotator cuff tears (FTRCTs) represent a major clinical concern because they show highly compromised healing capacity.

PURPOSE

To evaluate the efficacy of using a 3-dimensional (3D) bioprinted scaffold with human umbilical cord blood (hUCB)-mesenchymal stem cells (MSCs) for regeneration of chronic FTRCTs in a rabbit model.

STUDY DESIGN

Controlled laboratory study.

METHODS

A total of 32 rabbits were randomly assigned to 4 treatment groups (n = 8 per group) at 6 weeks after a 5-mm FTRCT was created on the supraspinatus tendon. Group 1 (G1-SAL) was transplanted with normal saline. Group 2 (G2-MSC) was transplanted with hUCB-MSCs (0.2 mL, 1 × 10⁶) into FTRCTs. Group 3 (G3-3D) was transplanted with a 3D bioprinted construct without MSCs, and group 4 (G4-3D+MSC) was transplanted with a 3D bioprinted construct containing hUCB-MSCs (0.2 mL, 1 × 10⁶ cells) into FTRCTs. All 32 rabbits were euthanized at 4 weeks after treatment. Examination of gross morphologic changes and histologic results was performed on all rabbits after sacrifice. Motion analysis was also performed before and after treatment.

RESULTS

In G4-3D+MSC, newly regenerated collagen type 1 fibers, walking distance, fast walking time, and mean walking speed were greater than those in G2-MSC based on histochemical and motion analyses. In addition, when compared with G3-3D, G4-3D+MSC showed more prominent regenerated tendon fibers and better parameters of motion analysis. However, there was no significant difference in gross tear size among G2-MSC, G3-3D, and G4-3D+MSC, although these groups showed significant decreases in tear size as compared with the control group (G1-SAL).

CONCLUSION

Findings of this study show that a tissue engineering strategy based on a 3D bioprinted scaffold filled with hUCB-MSCs can improve the microenvironment for regenerative processes of FTRCT without any surgical repair.

CLINICAL RELEVANCE

In the case of rotator cuff tear, the cell loss of the external MSCs can be increased by exposure to synovial fluid. Therefore, a 3D bioprinted scaffold in combination with MSCs without surgical repair may be effective in increasing cell retention in FTRCT.

Repair of Rotator Cuff Tendon Defects in Aged Rats Using a Growth Factor Injectable Gel Scaffold

PURPOSE

To determine if the tendon-specific crosslinking gelatin (Col-Tgel) impregnated with growth factors promotes tendon healing at the bone interface and in a tendon window model.

METHODS

Two different Col-Tgel formulations were first tested in vitro by evaluating cell morphology and tendogenic differentiation. After the optimum formulation was determined, the gel was mixed with either transforming growth factor-β3 (TGF-β3) or growth differentiation factor-7 (GDF-7) growth factor and prepared for injections. Window defects were induced in 12 animals, which were randomized into the following treatments: (1) sham, (2) empty Col-Tgel, (3) Col-Tgel containing TGF-β3, or (4) Col-Tgel containing GDF-7. Based on these results, the sham, empty Col-Tgel, and Col-Tgel containing TGF-β3 were applied to the supraspinatus repair interface. Tendons were analyzed biomechanically and histologically using hematoxylin and eosin and Masson's trichrome staining.

RESULTS

In the window defect model, histologic scores were the best in rats treated with TGF-β3 containing Col-Tgel, followed by the empty Col-Tgel scaffold, and finally the sham control. The GDF-7 Col-Tgel was not further tested because occasional ectopic cartilage and bone formation was found in the prior window defect model. In the supraspinatus repair model, there was no statistical difference (P > .05) in the biomechanical strength among the 3 treatment groups, but load-to-failure ratio improved when TGF-β3 was added to the scaffold, suggesting improved tendon healing.

CONCLUSIONS

This pilot study evaluated the performance of an injectable gel tendon graft in a population of retired breeder rats. The results suggest that Col-Tgel containing TGF-β3 may be a useful adjunctive treatment for surgical repair of full-thickness rotator cuff tears. Histologic and biomechanical scores suggest that Col-Tgel containing TGF-β3 promotes tendon healing.

CLINICAL RELEVANCE

The results of this study suggest that shoulders injected with Col-Tgel may be a useful adjunctive treatment for repair of rotator cuff tears.

Regenerative effects of mesenchymal stem cells by dosage in a chronic rotator cuff tendon tear in a rabbit model

Aim: We investigated the therapeutic effects and optimal dose of human umbilical cord blood (UCB)-derived mesenchymal stem cell (MSC) injection in a chronic full-thickness rotator cuff tendon tear. Methods: Rabbits (n = 30) were allocated into three groups (normal saline, G1-Sal; 1 × 10⁶ cells UCB-MSC, G2-Low; 2 × 10⁶ cells UCB-MSC, G3-High). Injections were done into the chronic full-thickness rotator cuff tendon tear 6 weeks after a full-thickness tendon tear of the subscapularis was created. Gross & histologic evaluation and motion analysis was done at pre and 4 weeks post-injection. Results: There were no significant differences in tear size and motion analysis parameters 4 weeks after injection between G2-Low and G3-High. Conclusion: The benefits of UCB-MSCs are not dose-dependent in a rabbit model.

Visualizing the Fate of Intra-Articular Injected Mesenchymal Stem Cells In Vivo in the Second Near-Infrared Window for the Effective Treatment of Supraspinatus Tendon Tears

Mesenchymal stem cells (MSCs) are capable of exerting strong therapeutic potential for the treatment of supraspinatus tendon tear. However, MSC therapy remains underutilized and perhaps underrated due to the limited evidence of dynamic visualization of cellular behavior in vivo. Here, second near-infrared fluorescence imaging with biocompatible PbS quantum dots (QDs) provides a cellular migration map and information on the biodistribution and clearance processes of three densities of intra-articularly injected, labeled MSCs to treat supraspinatus tendon tear in mice. Intra-articular injection avoids entrapment of MSCs by filter organs and reduces the QD-induced organ toxicity. Notably, the MSCs share a similar migration direction, but the moderate density group is somewhat more efficient, showing the longest residence time and highest cell retention rate around the footprint during the repair stage. Furthermore, quantitative kinetic investigation demonstrates that labeled MSCs are cleared by feces and urine. Histomorphometric analysis demonstrates that the moderate density group achieves maximum therapeutic effect and labeled MSCs do not induce any injury or inflammation to major organs, which suggests that administration of too many or few MSCs may decrease their effectiveness. Such an imaging approach provides spatiotemporal evidence for response to MSC therapy in vivo, facilitating the optimization of MSC therapy.

Tenogenic differentiation protocol in xenogenic-free media enhances tendon-related marker expression in ASCs

Adipose-derived stem cells (ASCs) are multipotent and immune-privileged mesenchymal cells, making them ideal candidates for therapeutic purposes to manage tendon disorders. Providing safe and regulated cell therapy products to patients requires adherence to good manufacturing practices. To this aim we investigated the in vitro tenogenic differentiation potential of ASCs using a chemically defined serum-free medium (SF) or a xenogenic-free human pooled platelet lysate medium (hPL) suitable for cell therapy and both supplemented with CTGF, TGFβ-3, BMP-12 and ascorbic acid (AA) soluble factors. Human ASCs were isolated from 4 healthy donors and they were inducted to differentiate until 14 days in both hPL and SF tenogenic media (hPL-TENO and SF-TENO). Cell viability and immunophenotype profile were analysed to evaluate mesenchymal stem cell (MSC) characteristics in both xenogenic-free media. Moreover, the expression of stemness and tendon-related markers upon cell differentiation by RT-PCR, protein staining and cytofluorimetric analysis were also performed. Our results showed the two xenogenic-free media well support cell viability of ASCs and maintain their MSC nature as demonstrated by their typical immunophenototype profile and by the expression of NANOG, OCT4 and Ki67 genes. Moreover, both hPL-TENO and SF-TENO expressed significant high levels of the tendon-related genes SCX, COL1A1, COL3A1, COMP, MMP3 and MMP13 already at early time points in comparison to the respective controls. Significant up-regulations in scleraxis, collagen and tenomodulin proteins were also demonstrated at in both differentiated SF and hPL ASCs. In conclusion, we demonstrated firstly the feasibility of both serum and xenogenic-free media tested to culture ASCs moving forward the GMP-compliant approaches for clinical scale expansion of human MSCs needed for therapeutical application of stem cells. Moreover, a combination of CTGF, BMP-12, TGFβ3 and AA factors strongly and rapidly induce human ASCs to differentiate into tenocyte-like cells.

The effect of autologous platelet rich plasma on tenocytes of the human rotator cuff

Background

Platelet rich plasma (PRP) is widely used in rotator cuff repairs but its effect on the healing process is unclear. Several cell culture studies on the effect of allogenic PRP have reported promising results but are not transferable to clinical practice.

The aim of the present study is to assess the possible effect of autologous PRP on rotator cuff tendon cells. The amount of growth factors involved with tendon-bone healing (PDGF-AB, IGF-1, TGF-β1, BMP-7 and -12) is quantified.

Methods

Rotator cuff tissue samples were obtained from (n = 24) patients grouped by age (>/< 65 years) and sex into four groups and cells were isolated and characterized. Later, autologous PRP preparations were obtained and the effect was analyzed by means of cell proliferation, collagen I synthesis and expression of collagen I and III. Furthermore, the PRPs were quantified for growth factor content by means of platelet-derived growth factor (PDGF-AB), insulin-like growth factor (IGF-1), transforming growth factor (TGF-β1), as well as bone morphogenetic protein (BMP) -7 and − 12.

Results

Cell proliferation and absolute synthesis of collagen I were positively affected by PRP exposure compared to controls (p < 0.05), but expression and relative synthesis of collagen I (normalized to cell proliferation) were significantly reduced.

PRP contained high amounts of IGF-1 and lower levels of TGF-β1 and PDGF-AB. The amounts of BMP-7 and -12 were below the detection limits.

Conclusions

PRP is a source of growth factors such involved with tendon-bone healing. PRP had an anabolic effect on the human rotator cuff tenocytes of the same individual in vitro by means of cell proliferation and absolute, but not relative collagen I synthesis.

These results encourage further studies on clinical outcomes with more comparable standards in terms of preparation and application methods.

Level of evidence

Controlled laboratory study.

Bioinformatics analysis of differentially expressed genes in rotator cuff tear patients using microarray data

Background

Rotator cuff tear (RCT) is a common shoulder disorder in the elderly. Muscle atrophy, denervation and fatty infiltration exert secondary injuries on torn rotator cuff muscles. It has been reported that satellite cells (SCs) play roles in pathogenic process and regenerative capacity of human RCT via regulating of target genes. This study aims to complement the differentially expressed genes (DEGs) of SCs that regulated between the torn supraspinatus (SSP) samples and intact subscapularis (SSC) samples, identify their functions and molecular pathways.

Methods

The gene expression profile GSE93661 was downloaded and bioinformatics analysis was made.

Results

Five hundred fifty one DEGs totally were identified. Among them, 272 DEGs were overexpressed, and the remaining 279 DEGs were underexpressed. Gene ontology (GO) and pathway enrichment analysis of target genes were performed. We furthermore identified some relevant core genes using gene–gene interaction network analysis such as GNG13, GCG, NOTCH1, BCL2, NMUR2, PMCH, FFAR1, AVPR2, GNA14, and KALRN, that may contribute to the understanding of the molecular mechanisms of secondary injuries in RCT. We also discovered that GNG13/calcium signaling pathway is highly correlated with the denervation atrophy pathological process of RCT.

Conclusion

These genes and pathways provide a new perspective for revealing the underlying pathological mechanisms and therapy strategy of RCT.

Therapeutic Effects of Umbilical Cord Blood-Derived Mesenchymal Stem Cells Combined with Polydeoxyribonucleotides on Full-Thickness Rotator Cuff Tendon Tear in a Rabbit Model

While therapies using mesenchymal stem cells (MSCs) to treat rotator cuff tendon tear (RCTT) have yielded some promising preliminary results, MSCs therapy has not yet completely regenerated full-thickness RCTT (FTRCTT). It has recently been reported that polydeoxyribonucleotide (PDRN) is effective in the treatment of chronic rotator cuff disease. We hypothesized that local injection of human umbilical cord blood-derived (UCB)–MSCs with PDRN would be more effective in regenerating tendon tear than UCB-MSCs alone. The purpose of this study was to evaluate the effects of UCB–MSCs combined with different doses of PDRN on the regeneration of RCTT in a chronic RCTT model by using a rabbit model. New Zealand white rabbits (n = 24) with FTRCTT were allocated randomly into three groups (8 rabbits per group). Three different injectants (G1-S, 0.2 mL UCB-MSCs; G2-P1, 0.2 mL UCB-MSCs with one injection of 0.2 mL PDRN; G3-P4, 0.2 mL UCB-MSCs, and four injections of 0.2 mL PDRN per week) were injected into FTRCTT under US-guidance. After the rabbits were euthanized, we evaluated ross morphological and histological change. Motion analysis was also performed. There were significant differences in gross morphological changes between before, and at 4 weeks after injection, in all three groups, but no differences were found among the three groups. Masson’s trichrome (MT) or anti-type 1 collagen antibody (COL-1)-positive cell densities in G2-P1 and G3-P4 were improved significantly compared with those in G1-S, but showed no significant difference between G2-P1 and G3-P4. On motion analysis, walking distance and fast walking time in G2-P1 and G3-P4 were significantly longer/higher than those in G1-S, but showed no significant differences between G2-P1 and G3-P4. These results demonstrated that there was no significant difference in the gross morphologic change of tendon tear between UCB-MSCs only and combination with PDRN injection in rabbit model of chronic traumatic FTRCTT. Furthermore, there were no significant differences in the regenerative effects between high and low doses of (0.8 and 0.2) mL of PDRN.

Effects of Allogenic Dermal Fibroblasts on Rotator Cuff Healing in a Rabbit Model of Chronic Tear

BACKGROUND

The failure of rotator cuffs to heal after repair is an unresolved surgical issue. There have been substantial efforts, including the use of biological supplements, to enhance tendon healing. Dermal fibroblasts are a good candidate for tendon tissue engineering because they are similar to the tenocytes used for collagen synthesis. In addition, they are easily accessible because autologous dermal fibroblasts can be obtained from individual skin without major skin defects and allogenic dermal fibroblasts (ADFs) have already been commercialized in the field of skin engineering.

PURPOSE

To determine the effects of dermal fibroblasts on tendon-to-bone healing in a rabbit model of a chronic rotator cuff tear.

STUDY DESIGN

Controlled laboratory study.

METHODS

A total of 33 rabbits were randomly allocated into 3 groups (n = 11 each). Supraspinatus tendons were detached and left for 6 weeks to establish a chronic rotator tear model. Torn tendons were repaired in a transosseous manner with the injection of 5 × 10⁶ ADFs with fibrin in group A, fibrin only in group B, and saline only in group C. At 12 weeks after repair, the mechanical test and histological evaluation were performed.

RESULTS

Seven rabbits died before the evaluation (1 in group A, 2 in group B, 4 in group C). In the final evaluation, the mean ± SD load to failure was 48.1 ± 13.3 N/kg for group A, 34.5 ± 8.9 N/kg for group B, and 31.1 ± 8.3 N/kg for group C, and group A showed significantly higher load-to-failure values than the other groups ( P = .011). The midsubstance tear rate, which presented stronger tendon-to-bone healing than insertional tear, was 50.0% in group A, 22.2% in group B, 28.6% in group C, but the differences were not statistically significant ( P = .413). In the histological evaluation, group A showed greater collagen fiber continuity and better orientation than the other groups.

CONCLUSION

This controlled laboratory study verified, on the basis of biomechanics and histology, the potential for the use of ADFs in rotator cuff healing. The current results suggest a new biological supplement to increase the rate of rotator cuff healing.

CLINICAL RELEVANCE

The most important finding of this study was the potential for a new biological supplement to enhance rotator cuff healing-a continuing challenge.

Treatment of Full-Thickness Rotator Cuff Tendon Tear Using Umbilical Cord Blood-Derived Mesenchymal Stem Cells and Polydeoxyribonucleotides in a Rabbit Model

Objective

The aim of this study was to investigate regenerative effects of ultrasound- (US-) guided injection with human umbilical cord blood-derived mesenchymal stem cells (UCB-MSCs) and/or polydeoxyribonucleotide (PDRN) injection in a chronic traumatic full-thickness rotator cuff tendon tear (FTRCTT) in a rabbit model.

Methods

Rabbits (n = 32) were allocated into 4 groups. After a 5 mm sized FTRCTT just proximal to the insertion site on the subscapularis tendon was created by excision, the wound was immediately covered by a silicone tube to prevent natural healing. After 6 weeks, 4 injectants (0.2 mL normal saline, G1-SAL; 0.2 mL PDRN, G2-PDRN; 0.2 mL UCB-MSCs, G3-MSC; and 0.2 mL UCB-MSCs with 0.2 ml PDRN, G4-MSC + PDRN) were injected into the FTRCTT under US guidance. We evaluated gross morphologic changes on all rabbits after sacrifice. Masson's trichrome, anti-type 1 collagen antibody, bromodeoxyuridine, proliferating cell nuclear antigen, vascular endothelial growth factor, and platelet endothelial cell adhesion molecule stain were performed to evaluate histological changes. Motion analysis was also performed.

Results

The gross morphologic mean tendon tear size in G3-MSC and G4-MSC + PDRN was significantly smaller than that in G1-SAL and G2-PDRN (p < 0.05). However, there were no significant differences in the tendon tear size between G3-MSC and G4-MSC + PDRN. In G4-MSC + PDRN, newly regenerated collagen type 1 fibers, proliferating cell activity, angiogenesis, walking distance, fast walking time, and mean walking speed were greater than those in the other three groups on histological examination and motion analysis.

Conclusions

Coinjection of UCB-MSCs and PDRN was more effective than UCB-MSC injection alone in histological and motion analysis in a rabbit model of chronic traumatic FTRCTT. However, there was no significant difference in gross morphologic change of tendon tear between UCB-MSCs with/without PDRN injection. The results of this study regarding the combination of UCB-MSCs and PDRN are worth additional investigations.

Arthroscopic Rotator Cuff Repair With Graft Augmentation of 3-Dimensional Biological Collagen for Moderate to Large Tears: A Randomized Controlled Study

BACKGROUND

Due to the highly organized tissue and avascular nature of the rotator cuff, rotator cuff tears have limited ability to heal after the tendon is reinserted directly on the greater tubercle of the humerus. Consequently, retears are among the most common complications after rotator cuff repair. Augmentation of rotator cuff repairs with patches has been an active area of research in recent years to reduce retear rate.

HYPOTHESIS

Graft augmentation with 3D collagen could prevent retears of the repaired tendon and improve tendon-bone healing in moderate to large rotator cuff tears.

STUDY DESIGN

Randomized controlled study; Level of evidence, 2.

METHODS

A prospective, randomized controlled study was performed in a consecutive series of 112 patients age 50 to 85 years who underwent rotator cuff repair with the suture-bridge technique (58 patients, control group) or the suture-bridge technique augmented with 3-dimensional (3D) collagen (54 patients, study group). All patients were followed for 28.2 months (range, 24-36 months). Visual analog scale score for pain, University of California Los Angeles (UCLA) shoulder score, and Constant score were determined. Magnetic resonance imaging was performed pre- and postoperatively (at a minimum of 24 months) to evaluate the integrity of the rotator cuff and the retear rate of the repaired tendon. Three patients in each group had biopsies at nearly 24 months after surgery with histological assessment and transmission electron microscopy.

RESULTS

A total of 104 patients completed the final follow-up. At the 12-month follow-up, the UCLA shoulder score was 28.1 ± 1.9 in the study group, which was significantly better than that in the control group (26.9 ± 2.1, P = .002). The Constant score was also significantly better in the study group (87.1 ± 3.2) than in the control group (84.9 ± 4.2, P = .003). However, at the final follow-up, no significant differences were found in the UCLA shoulder scores (29.4 ± 1.9 in the control group and 30.0 ± 1.6 in the study group, P = .052) or Constant scores (89.9 ± 3.2 in the control group and 90.8 ± 3.5 in the study group, P = .18). In terms of structural integrity, more patients in the study group had a favorable type I retear grade (18/51) than in the control group (10/53) ( P = .06). The postoperative retear rate was 34.0% in the control group and 13.7% in the study group, thus indicating a significantly lower retear rate in the study group ( P = .02). Biopsy specimens of the tendon-bone interface in 6 patients revealed more bone formation and more aligned fibers with larger diameters in the study group than in the control group. No intraoperative or postoperative complications were noted in either group.

CONCLUSION

3D collagen augmentation could provide effective treatment of moderate to large rotator cuff tears, providing substantial functional improvement, and could reduce the retear rate. This technique could also promote new tendon-bone formation, thus exerting a prominent effect on tendon-bone healing.

Rotator cuff tendon-to-bone healing at 12 months after patch grafting of acellular dermal matrix in an animal model

There is no report to investigate the histology and biomechanical strength of remodeled tendon-to-bone junction more than 6 months after patch grafting with acellular dermal matrix (ADM) on rotator cuff defect. We investigated those 12 months after surgery and hypothesized that a new native enthesis is not regenerated and the biomechanical strength is inferior to normal control. Adult male Sprague-Dawley rats underwent ADM patch grafting for the rotator cuff defect. Quantitative histological analysis, immunohistochemical analysis for collagen type I and III, and biomechanical testing were performed 12 months after surgery. The controls were unoperated age-matched rats. In the grafted rats, the collagen arrangement was more irregular and the fibrocartilage layer was smaller at the tendon-bone interface than in the controls although dense collagen fibers in the remodeled tendon were observed; the number of chondrocytes, the percentage of chondrocytes aligned in rows, and the area of the fibrocartilage layer were significantly smaller than in the control group (p = 0.0252, 0.0039, and 0.0252, respectively). Grafted specimens showed significantly lower collagen organization in the midsubstance and tendon-bone interface than the controls (p = 0.0252 and 0.0374, respectively). Immunohistochemical analysis demonstrated that the remodeled tendon fibers were stained more strongly for type III than type I. At 12 months postoperatively, the ultimate load to failure was significantly lower in the graft group than normal control (p = 0.0026); that was 47.8% of normal controls. 12 months after rotator cuff patch grafting with ADM, the formation of a new enthesis grossly resembled the native structure but there was poor cellular organization and the biomechanical strength of remodeled tendon-to-bone was only 48% of normal controls. Advances in tissue engineering and postoperative rehabilitation are needed to promote the healing process after rotator cuff patch grafting.

Boosting tendon repair: interplay of cells, growth factors and scaffold-free and gel-based carriers

Background

Tendons are dense connective tissues and critical components for the integrity and function of the musculoskeletal system. Tendons connect bone to muscle and transmit forces on which locomotion entirely depends. Due to trauma, overuse and age-related degeneration, many people suffer from acute or chronic tendon injuries. Owing to their hypovascularity and hypocellularity, tendinopathies remain a substantial challenge for both clinicians and researchers. Surgical treatment includes suture or transplantation of autograft, allograft or xenograft, and these serve as the most common technique for rescuing tendon injuries. However, the therapeutic efficacies are limited by drawbacks including inevitable donor site morbidity, poor graft integration, adhesion formations and high rates of recurrent tearing. This review summarizes the literature of the past 10 y concerning scaffold-free and gel-based approaches for treating tendon injuries, with emphasis on specific advantages of such modes of application, as well as the obtained results regarding in vitro and in vivo tenogenesis.

Results

The search was focused on publications released after 2006 and 83 articles have been analysed. The main results are summarizing and discussing the clear advantages of scaffold-free and hydrogels carriers that can be functionalized with cells alone or in combination with growth factors.

Conclusion

The improved understanding of tissue resident adult stem cells has made a significant progress in recent years as well as strategies to steer their fate toward tendon lineage, with the help of growth factors, have been identified. The field of tendon tissue engineering is exploring diverse models spanning from hard scaffolds to gel-based and scaffold-free approaches seeking easier cell delivery and integration in the site of injury. Still, the field needs to consider a multifactorial approach that is based on the combination and fine-tuning of chemical and biomechanical stimuli. Taken together, tendon tissue engineering has now excellent foundations and enters the period of precision and translation to models with clinical relevance on which better treatment options of tendon injuries can be shaped up.

Impaired contractile function of the supraspinatus in the acute period following a rotator cuff tear

Background

Rotator cuff (RTC) tears are a common clinical problem resulting in adverse changes to the muscle, but there is limited information comparing histopathology to contractile function. This study assessed supraspinatus force and susceptibility to injury in the rat model of RTC tear, and compared these functional changes to histopathology of the muscle.

Methods

Unilateral RTC tears were induced in male rats via tenotomy of the supraspinatus and infraspinatus. Maximal tetanic force and susceptibility to injury of the supraspinatus muscle were measured in vivo at day 2 and day 15 after tenotomy. Supraspinatus muscles were weighed and harvested for histologic analysis of the neuromuscular junction (NMJ), intramuscular lipid, and collagen.

Results

Tenotomy resulted in eventual atrophy and weakness. Despite no loss in muscle mass at day 2 there was a 30% reduction in contractile force, and a decrease in NMJ continuity and size. Reduced force persisted at day 15, a time point when muscle atrophy was evident but NMJ morphology was restored. At day 15, torn muscles had decreased collagen-packing density and were also more susceptible to contraction-induced injury.

Conclusion

Muscle size and histopathology are not direct indicators of overall RTC contractile health. Changes in NMJ morphology and collagen organization were associated with changes in contractile function and thus may play a role in response to injury. Although our findings are limited to the acute phase after a RTC tear, the most salient finding is that RTC tenotomy results in increased susceptibility to injury of the supraspinatus.

Platelet-Rich Plasma Derived Growth Factors Contribute to Stem Cell Differentiation in Musculoskeletal Regeneration

Stem cell treatment and platelet-rich plasma (PRP) therapy are two significant issues in regenerative medicine. Stem cells such as bone marrow mesenchymal stem cells, adipose-derived stem cells and periodontal ligament stem cells can be successfully applied in the field of tissue regeneration. PRP, a natural product isolated from whole blood, can secrete multiple growth factors (GFs) for regulating physiological activities. These GFs can stimulate proliferation and differentiation of different stem cells in injury models. Therefore, combination of both agents receives wide expectations in regenerative medicine, especially in bone, cartilage and tendon repair. In this review, we thoroughly discussed the interaction and underlying mechanisms of PRP derived GFs with stem cells, and assessed their functions in cell differentiation for musculoskeletal regeneration.

Enhancement of rotator cuff tendon-bone healing with fibroblast growth factor 2 impregnated in gelatin hydrogel sheets in a rabbit model

BACKGROUND

Application of fibroblast growth factor 2 (FGF-2) may improve the healing response after rotator cuff (RC) surgical repair. This study aimed to determine whether FGF-2-impregnated gelatin hydrogel sheet (GHS) incorporation into the bony trough on the greater tuberosity facilitates healing after RC surgical repair in rabbits.

METHODS

We assigned 120 adult male Japanese white rabbits treated with unilateral surgery for supraspinatus tendon repair into the following groups: suture-only group (suture); suture and GHS with phosphate-buffered saline (carrier); suture and GHS with 3 µg of FGF-2 (F3); and suture and GHS with 30 µg of FGF-2 (F30). The effect of FGF-2 was assessed using histologic, biomechanical, and microcomputed tomography evaluations at 2, 6, and 12 weeks.

RESULTS

At 12 weeks, loose fibrovascular tissues emerged at the repair site in the suture and carrier groups and dense tendon-like tissues in the F3 and F30 groups, which demonstrated significantly higher ultimate load-to-failure and stress-to-failure at 12 weeks than that in the suture and carrier groups. Microcomputed tomography imaging showed ectopic calcification formation in some specimens from each group. Appearances or frequencies were similar among groups. The histologic and biomechanical effects of FGF-2 on RC healing were obvious at ≥6 weeks postoperatively.

CONCLUSION

FGF-2-impregnated GHS incorporation into the bony trough on the greater tuberosity before RC surgical repair is feasible and results in histologic and biomechanical improvements during RC healing in rabbits. No detrimental effect on ectopic calcification was observed.

Dual growth factor-immobilized asymmetrically porous membrane for bone-to-tendon interface regeneration on rat patellar tendon avulsion model

Insufficient repair of the bone-to-tendon interface (BTI) with structural/compositional gradients has been a significant challenge in orthopedics. In this study, dual growth factor (platelet-derived growth factor-BB [PDGF-BB] and bone morphogenetic protein-2 [BMP-2])-immobilized polycaprolactone (PCL)/Pluronic F127 asymmetrically porous membrane was fabricated to estimate its feasibility as a potential strategy for effective regeneration of BTI injury. The growth factors immobilized (via heparin-intermediated interactions) on the membrane were continuously released for up to ∼80% of the initial loading amount after 5 weeks without a significant initial burst. From the in vivo animal study using a rat patellar tendon avulsion model, it was observed that the PDGF-BB/BMP-2-immobilized membrane accelerates the regeneration of the BTI injury, probably because of the continuous release of both growth factors (biological stimuli) and their complementary effect to create a multiphasic structure (bone, fibrocartilage, and tendon) like a native structure, as well as the role of the asymmetrically porous membrane as a physical barrier (nanopore side; prevention of fibrous tissue invasion into the defect site) and scaffold (micropore side; guidance for tissue regeneration). © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 106A: 115-125, 2018.

Local rhBMP-12 on an Absorbable Collagen Sponge as an Adjuvant Therapy for Rotator Cuff Repair-A Phase 1, Randomized, Standard of Care Control, Multicenter Study: Part 2-A Pilot Study of Functional Recovery and Structural Outcomes

BACKGROUND

The high failure rate of rotator cuff repairs requires the development of methods to enhance healing at the tendon-bone junction of the repair site.

PURPOSE

To assess functional recovery and structural outcomes in detail after implanting recombinant human bone morphogenetic protein-12 (rhBMP-12)/absorbable collagen sponge (ACS) as adjuvant treatment during open rotator cuff repair in patients over a 1-year postoperative follow-up.

STUDY DESIGN

Randomized controlled trial; Level of evidence, 2.

METHODS

A total of 20 patients were randomized into 2 groups, rhBMP-12/ACS and standard-of-care (SOC) control, with 16 and 4 patients, respectively. The patients underwent open repair of a rotator cuff tear at least 2 to 4 cm wide; in the rhBMP-12/ACS group, this was augmented with a bioscaffold containing rhBMP-12. Follow-up assessments were conducted with a 100-mm visual analog scale (VAS) for pain and active and passive ranges of motion (ROMs) including forward flexion, elevation in the scapular plane, abduction, and external rotation at 12, 16, 26, 39, and 52 weeks after surgery; isometric strength in scapular abduction and external rotation at 16, 26, 39, and 52 weeks; and magnetic resonance imaging (MRI) at 12 and 52 weeks.

RESULTS

The mean VAS score decreased from 37.9 mm preoperatively to 13.8 mm at week 52, and ROM and isometric strength recovered at week 52 in the rhBMP-12/ACS group. The mean VAS score decreased from 48.3 mm preoperatively to 1.5 mm at week 52, and ROM (excluding external rotation) and isometric strength recovered by week 52 in the SOC control group. Of the 16 patients in the rhBMP-12/ACS group, 14 showed an intact repair at week 12; the MRI scans of the other 2 patients could not be evaluated because of artifacts. In the SOC control group, 1 patient showed repair failure. At week 52, 14 repairs in the rhBMP-12/ACS group and 2 repairs with available MRI scans in the SOC control group remained intact.

CONCLUSION

Functional recovery and structural outcomes in patients in whom rhBMP-12/ACS was used as adjuvant therapy in rotator cuff repair justify conducting future, larger, multicenter, prospective studies.

REGISTRATION

NCT00936559, NCT01122498 (ClinicalTrials.gov identifier).

Effect of Footprint Preparation on Tendon-to-Bone Healing: A Histologic and Biomechanical Study in a Rat Rotator Cuff Repair Model

PURPOSE

To compare the histologic and biomechanical effects of 3 different footprint preparations for repair of tendon-to-bone insertions and to assess the behavior of bone marrow-derived cells in each method of insertion repair.

METHODS

We randomized 81 male Sprague-Dawley rats and green fluorescent protein-bone marrow chimeric rats into 3 groups. In group A, we performed rotator cuff repair after separating the supraspinatus tendon from the greater tuberosity and removing the residual tendon tissue. In group B, we also drilled 3 holes into the footprint. The native fibrocartilage was preserved in groups A and B. In group C, we excavated the footprint until the cancellous bone was exposed. Histologic repair of the tendon-to-bone insertion, behavior of the bone marrow-derived cells, and ultimate force to failure were examined postoperatively.

RESULTS

The areas of metachromasia in groups A, B, and C were 0.033 ± 0.019, 0.089 ± 0.022, and 0.002 ± 0.001 mm²/mm², respectively, at 4 weeks and 0.029 ± 0.022, 0.090 ± 0.039, and 0.003 ± 0.001 mm²/mm², respectively, at 8 weeks. At 4 and 8 weeks postoperatively, significantly higher cartilage matrix production was observed in group B than in group C (4 weeks, P = .002; 8 weeks, P < .001). In green fluorescent protein-bone marrow chimeric rats in group B, bone marrow-derived chondrogenic cells infiltrated the fibrocartilage layer. Ultimate force to failure was significantly higher in group B (19.7 ± 3.4 N) than in group C (16.7 ± 2.0 N) at 8 weeks (P = .031).

CONCLUSIONS

Drilling into the footprint and preserving the fibrocartilage improved the quality of repair tissue and biomechanical strength at the tendon-to-bone insertion after rotator cuff repair in an animal model.

CLINICAL RELEVANCE

Drilling into the footprint and preserving the fibrocartilage can enhance repair of tendon-to-bone insertions. This method may be clinically useful in rotator cuff repair.

Biomaterials based strategies for rotator cuff repair

Tearing of the rotator cuff commonly occurs as among one of the most frequently experienced tendon disorders. While treatment typically involves surgical repair, failure rates to achieve or sustain healing range from 20 to 90%. The insufficient capacity to recover damaged tendon to heal to the bone, especially at the enthesis, is primarily responsible for the failure rates reported. Various types of biomaterials with special structures have been developed to improve tendon-bone healing and tendon regeneration, and have received considerable attention for replacement, reconstruction, or reinforcement of tendon defects. In this review, we first give a brief introduction of the anatomy of the rotator cuff and then discuss various design strategies to augment rotator cuff repair. Furthermore, we highlight current biomaterials used for repair and their clinical applications as well as the limitations in the literature. We conclude this article with challenges and future directions in designing more advanced biomaterials for augmentation of rotator cuff repair.