Movin and Bonar scores assess the same characteristics of tendon histology

Augmentation of the medial collateral ligament using suture tape reduces the recurrence after corrective surgery for severe hallux valgus

BACKGROUND

The severity of hallux valgus (HV) deformity is associated with recurrence after corrective surgery because of the degenerative change of the medial capsule including the medial collateral ligament (MCL) at the metatarsophalangeal joint. This study aimed to assess the effectiveness of the MCL augmentation using a suture tape anchor of the recurrence of HV and to evaluate the histological changes of the medial joint capsule in HV patients.

METHODS

Thirty-four feet with severe hallux valgus were included and divided into 2 groups. Seventeen feet had the MCL reconstruction using suture tape anchor with a combination of the corrective osteotomy as the suture tape group (mean age, 64.0 years), and other seventeen feet had the corrective osteotomy without MCL reconstruction as the control group (mean age, 62.0 years). HV angle (HVA) and intermetatarsal angle (IMA) on the weight-bearing radiograms and the Japanese Society for Surgery of the Foot (JSSF) score in both groups were compared at the final follow-up. The medial capsule was harvested from other 20 feet with HV and the relationship between the severity of HV and the histological findings was analyzed.

RESULTS

HVA, IMA, and JSSF scores in both groups were significantly improved from preoperatively to the final follow-up (P < 0.01). At the final follow-up, HVA in the suture tape group (9.2°) was significantly smaller than that in the control (15.4°) (P < 0.01). There were no significant differences in the IMA and the JSSF score at the final follow-up between both groups. Histological scores in HV with ≥40° HVA was significantly worse than those in <40°.

CONCLUSION

The medial joint capsule in severe HV deformity showed the degenerative change and the MCL reconstruction using suture tape combined with osteotomy provides a strong medial constraint to prevent the recurrence of the deformity in severe hallux valgus.

LEVEL OF CLINICAL EVIDENCE

3.

Achilles tendon assessment on quantitative MRI: Sources of variability and relationships to tendinopathy

Quantitative MRI (qMRI) measures are useful in assessing musculoskeletal tissues, but application to tendon has been limited. The purposes of this study were to optimize, identify sources of variability, and establish reproducibility of qMRI to assess Achilles tendon. Additionally, preliminarily estimates of effect of tendon pathology on qMRI metrics and structure-function relationships between qMRI measures and ankle performance were examined. T1, T1ρ, T2, and T2* maps of the Achilles tendon were obtained using a 3T MRI scanner. In participants with asymptomatic tendons (n = 21), MRI procedures were repeated twice, and region of interest selection was performed by three raters. Variance decomposition and reproducibility statistics were completed. To estimate the effect of pathology, qMRI measures from individuals with asymptomatic tendons were compared to qMRI measures from a pilot group of individuals with Achilles tendinopathy (n = 7). Relationships between qMRI and ankle performance measures were assessed. Between-participant variation accounted for the majority of variability (46.7%-64.0%) in all qMRI measures except T2*. ICCs met or exceeded 0.7 for all qMRI measures when averaged across raters or scans. Relaxation times were significantly longer in tendinopathic tendons (mean (SD) T1: 977.8 (208.6) ms, T1ρ: 35.4 (7.1) ms, T2: 42.8 (7.9) ms, T2*: 14.1 (7.6) ms, n = 7) compared to asymptomatic control tendons (T1: 691.7 (32.4) ms, T1ρ: 24.0 (3.6) ms, T2: 24.4 (7.5) ms, T2*: 9.5 (3.4) ms, n = 21) (p < 0.011 for all comparisons). T1 related to functional performance measures in symptomatic and asymptomatic groups. Study findings suggest that qMRI is reliable to assess the Achilles tendon. qMRI quantitatively assesses the presence of tendon pathology and relates to functional performance outcomes, supporting the utility of incorporating qMRI in research and clinic.

Blood flow restriction training does not negatively alter the mechanical strength or histomorphology of uninjured equine superficial digital flexor tendons

BACKGROUND

Low load exercise training with blood flow restriction (BFR) has become increasingly used by human physical therapists to prescribe controlled exercise following orthopaedic injury; its effects on the equine superficial digital flexor tendon (SDFT), however, are unknown.

OBJECTIVE

To investigate outcomes of pressure specific BFR walking exercise on uninjured equine SDFT biomechanics and histomorphology.

STUDY DESIGN

Controlled in vivo experiment.

METHODS

Four forelimbs of four horses were exposed to 40 BFR-walk sessions (10-min interval walking) on a treadmill over a 56-day study period with their contralateral forelimbs serving as untreated controls. Similarly, four forelimbs of four control horses were exposed to 40 sham cuff walk sessions. On study Day 56, all horses (n = 8) were humanely euthanised and forelimb SDFTs underwent non-destructive biomechanical testing and corresponding histomorphological analysis. Significance in biomechanical parameters between treatment groups was analysed using a mixed-effects ANOVA with Tukey's post-hoc tests.

RESULTS

Statistically significant differences in SDFT stiffness for both first (p = 0.02) and last cycles (p = 0.03) were appreciated within the BFR treated group only, with BFR exposed forelimbs being significantly stiffer than the contralateral unexposed forelimbs. When normalised to cross-sectional area, no significant differences were appreciated among treatment groups in elastic modulus for the first (p = 0.5) or last cycles (p = 0.4). No histological differences were appreciated among treatment groups according to Bonar, Movin, or musculotendinous junction evaluation criteria.

MAIN LIMITATIONS

Short-term comparisons were performed in a small sample population without correlation to performance outcome measures. Optimal occlusion percentages and walk protocols remain unknown.

CONCLUSIONS

This study demonstrated no negative impact of BFR on mechanical strength of the equine SDFT; however, evidence suggests that BFR results in increased tendon stiffness based on biomechanical testing and subsequent calculations. No consistent detrimental histomorphological changes were seen.

Antioxidant and anti-inflammatory injectable hydrogel microspheres for in situ treatment of tendinopathy

Tendinopathy is a common disorder that causes local dysfunction and reduces quality of life. Recent research has indicated that alterations in the inflammatory microenvironment play a vital role in the pathogenesis of tendinopathy. Herein, injectable methacrylate gelatin (GelMA) microspheres (GM) were fabricated and loaded with heparin-dopamine conjugate (HDC) and hepatocyte growth factor (HGF). GM@HDC@HGF were designed to balance the inflammatory microenvironment by inhibiting oxidative stress and inflammation, thereby regulating extracellular matrix (ECM) metabolism and halting tendon degeneration. Combining growth factors with heparin was expected to improve the encapsulation rate and maintain the long-term efficacy of HGF. In addition, the catechol groups on dopamine have adhesion and antioxidant properties, allowing potential attachment at the injured site, and better function synergized with HGF. GM@HDC@HGF injected in situ in rat Achilles tendinopathy (AT) models significantly down-regulated oxidative stress and inflammation, and ameliorated ECM degradation. In conclusion, the multifunctional platform developed presents a promising alternative for the treatment of tendinopathy.

Histopathological and histomorphometric investigation of the effects of different irrigation solutions on Achilles tendon healing in rats

OBJECTIVES

This study aimed to examine the effect of irrigation fluids containing povidone-iodine (PVP-I), rifampicin (RF), and chlorhexidine gluconate (CHG) used during surgery on healing on a rat Achilles tendon model.

MATERIALS AND METHODS

Twenty-eight male Sprague-Dawley rats (range, 300 to 400 g) were used in the experiment carried out between November 2022 and December 2022. The rats were divided into PVP-I, RF, CHG, and control groups, with seven rats in each group. Following the tenotomy and repair of the right Achilles tendon, the surgical site was irrigated using PVP-I, RF, CHG, or normal saline (the control group) for 2 min. All rats were sacrificed on the 21st postoperative day. The samples were evaluated histomorphometrically using the scoring system modified by Svensson, Soslowsky, and Cook and histopathologically using the Bonar and Movin classifications.

RESULTS

The RF group gave better results in all three scoring systems compared to the control, PVP-I, and CHG groups (p=0.008, p=0.002, and p=0.006, respectively). Cellularity, rounding, and tenocyte morphology showed a significant difference in favor of the RF group (p=0.004). While the distribution of ground substance glycosaminoglycans showed a significant difference in favor of the RF group, there was no significant difference among the other groups (p=0.22).

CONCLUSION

Irrigation solutions containing PVP-I, RF, or CHG show no negative effect on Achilles tendon healing. Moreover, the findings suggest that RF irrigation can accelerate the healing process.

Dynamic Tensile Stress Promotes Regeneration of Achilles Tendon in a Panda Rope Bridge Technique Mice Model

Regeneration of ruptured Achilles tendon remains a clinical challenge owing to its limited regenerative capacity. Dynamic tensile stress plays a positive role in the regeneration of tendon, although the specific underlying mechanisms remain unclear. In this study, the Achilles tendon defect-regeneration model was created in male C57BL/6 mice aged 8 weeks. The animals were randomly assigned to four groups-repair, non-repair, repair with fixation, and non-repair with fixation. The repair group and repair with fixation group adopted the panda rope bridge technique (PRBT) repair method. Our results demonstrated the presence of more densely aligned and mature collagen fibers, as well as more tendon-related makers, in the repair group at both 2- and 4-week post-surgery. Furthermore, the biomechanical strength of the regenerated tendon in the repair group was highly improved. Most importantly, the expressions of integrin αv and its downstream and the phosphorylation levels of FAK and ERK were remarkably higher in the repair group than in the other groups. Furthermore, blocking FAK or ERK with selective inhibitors PF573228 and U0126 resulted in obvious adverse effects on the histological structure of the regenerated Achilles tendon. In summary, this study demonstrated that dynamic tensile stress based on the PRBT could effectively promote the regeneration of the Achilles tendon, suggesting that dynamic tensile stress enhances the cell proliferation and tenogenic differentiation via the activation of the integrin/FAK/ERK signaling pathway.

Investigation of the effects of subacromial bursal tissue preservation and microfracture procedure on healing after rotator cuff repair in a rat model

INTRODUCTION

The aim of this study is to compare the preservation of bursal tissue and microfracture techniques and to examine the effectiveness of the combination of the two methods in rotator cuff tear healing in the rat shoulder.

HYPOTHESIS

Bursal tissue preservation combined with microfracture is more effective in the rotator cuff repair.

MATERIALS AND METHODS

Twenty-three male Sprague-Dawley rats were randomly divided into two groups. The bursal tissue was preserved in group 1 (n=11) and excised in group 2 (n=12). Groups were categorized into subgroups as L (left) and R (right) based on the shoulder side receiving microfracture (L received microfracture, R did not). Histopathological examination was performed using modified Bonar Score System.

RESULTS

Cell morphology grades of group 1 were lower than group 2 (p<0.05). In terms of collagen measurements, the grade of group 1L (bursa preservation+microfracture) was lower than groups 1R, 2L, and 2R, and the grade of group 1R was lower than groups 2L and 2R. Cellularity grades of group 2 were higher than group 1 (p<0.05). Extracellular matrix grades of group 1 were lower than group 2 (p<0.05). The overall grades were lower in group 1 than in group 2 (p<0.05).

DISCUSSION

Combined treatment of bursal tissue preservation and microfracture was the most efficient method as determined by healing findings in histopathological specimens. Preservation of bursal tissue was a more effective option in tendon healing than performing only microfracture.

LEVEL OF PROOF

II, animal research.

Aging and injury affect nuclear shape heterogeneity in tendon

Tissue level properties are commonly studied using histological stains assessed with qualitative scoring methods. As qualitative evaluation is typically insensitive, quantitative analysis provides additional information about pathological mechanisms, but cannot capture structural heterogeneity across cell subpopulations. However, molecular analyses of cell and nuclear behavior have identified that cell and more recently also nuclear shape are highly associated with cell function and malfunction. This study combined a Visually Aided Morpho-Phenotyping Image Recognition analysis that automatically segments cells based on their shape with an added capacity to further discriminate between cells in certain protein-rich extracellular matrix regions. We used tendon as a model system given the enormous changes in organization and cell and nuclear shape they undergo during aging and injury. Our results uncover that multiple shape modes of nuclei exist during maturity and aging in rat tendon and that distinct subgroups of cell nuclei shapes exist in proteoglycan-rich regions during aging. With injury, several immunomarkers (αSMA, CD31, CD146) were associated with more rounded shape modes. In human tendons, the cell nuclei at sites of injury were found to be more rounded relative to uninjured tissues. To conclude, the tendon tissue changes occurring during aging and injury could be associated with a variation in cell nuclear morphology and the appearance of various region-specific subpopulations. Thus, the methodologies developed allow for a deeper understanding of cell heterogeneity during tendon aging and injury and may be extended to study further clinical applications.

Histological and immunohistochemical guide to tendon tissue

Tendons are unique dense connective tissues with discrete zones having specific structure and function. They are juxtaposed with other tissues (e.g., bone, muscle, and fat) with different compositional, structural, and mechanical properties. Additionally, tendon properties change drastically with growth and development, disease, aging, and injury. Consequently, there are unique challenges to performing high quality histological assessment of this tissue. To address this need, histological assessment was one of the breakout session topics at the 2022 Orthopaedic Research Society (ORS) Tendon Conference hosted at the University of Pennsylvania. The purpose of the breakout session was to discuss needs from members of the ORS Tendon Section related to histological procedures, data presentation, knowledge dissemination, and guidelines for future work. Therefore, this review provides a brief overview of the outcomes of this discussion and provides a set of guidelines, based on the perspectives from our laboratories, for histological assessment to assist researchers in their quest to utilize these techniques to enhance the outcomes and interpretations of their studies.

Growth factors in the treatment of Achilles tendon injury

Achilles tendon (AT) injury is one of the most common tendon injuries, especially in athletes, the elderly, and working-age people. In AT injury, the biomechanical properties of the tendon are severely affected, leading to abnormal function. In recent years, many efforts have been underway to develop effective treatments for AT injuries to enable patients to return to sports faster. For instance, several new techniques for tissue-engineered biological augmentation for tendon healing, growth factors (GFs), gene therapy, and mesenchymal stem cells were introduced. Increasing evidence has suggested that GFs can reduce inflammation, promote extracellular matrix production, and accelerate AT repair. In this review, we highlighted some recent investigations regarding the role of GFs, such as transforming GF-β(TGF-β), bone morphogenetic proteins (BMP), fibroblast GF (FGF), vascular endothelial GF (VEGF), platelet-derived GF (PDGF), and insulin-like GF (IGF), in tendon healing. In addition, we summarized the clinical trials and animal experiments on the efficacy of GFs in AT repair. We also highlighted the advantages and disadvantages of the different isoforms of TGF-β and BMPs, including GFs combined with stem cells, scaffolds, or other GFs. The strategies discussed in this review are currently in the early stages of development. It is noteworthy that although these emerging technologies may potentially develop into substantial clinical treatment options for AT injury, definitive conclusions on the use of these techniques for routine management of tendon ailments could not be drawn due to the lack of data.

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.

An immunohistochemical and biomechanical evaluation of the effect of fat graft on tendon healing

AIM

To investigate the efficacy of fat grafting in primary tendon healing through immunohistochemical and biomechanical examinations.

MATERIAL AND METHOD

The study material comprised a total of 10 male Sprague-Dawley rats, each approximately 10 weeks old. All 10 rats were operated on bilaterally. The right Achilles tendon in all the animals was defined as the study group. The tendon was cut and then repaired, and then fat graft was applied to the repair area. The left Achilles tendon of all the rats constituted the control group. The tendon was cut and repaired with no further application. After 4 weeks, the rats were euthanised and samples were taken from the tendons for immunohistochemical and biomechanical examinations.

RESULTS

In the biomechanical evaluations, no statistically significant difference was determined between the groups in respect of peak load and stiffness values (p: .068, p: .089, respectively). In the histopathological evaluation, the tenocyte value of the study group was superior to that of the control group (p: .04). No statistically significant differences were determined between the groups in respect of the other histopathological parameters. In the immunohistochemical evaluations, the type I collagen and TGF values of the study group were found to be higher than those of the control group (p: .011, p: .012, respectively).

CONCLUSION

Compared to stem cell applications, the use of fat grafting is clinically easy to apply, has low costs, and has been shown to contribute to tendon healing at an immunohistochemical level with increased collagen and TGF beta values.

Rotator cuff degeneration and healing after rotator cuff repair

Rotator cuff tear is a common shoulder injury that compromises both function and quality of life. Despite the prevalence of the injury and advancements in repair techniques, a significant percentage of these repairs fail. This review aims to explore the multifactorial reasons behind this failure, including the degenerative nature of the rotator cuff tendon, inherent and extrinsic factors, and the role of hypoxia in tissue degeneration. Additionally, it elucidates potential strategies for improving healing outcomes.

Association of Severe Histological Degeneration of the Torn Supraspinatus Tendon and Retear After Arthroscopic Repair of Full-Thickness Rotator Cuff Tears Using the Suture Bridge Technique

BACKGROUND

Previous studies have demonstrated several prognostic factors for retear after arthroscopic rotator cuff repair (ARCR). However, studies that histologically evaluate the quality of the torn rotator cuff (RC) tendon and its association with postoperative outcomes are limited.

PURPOSE

To investigate factors associated with retear after ARCR using the suture bridge (SB) technique, including the degree of histological degeneration of the RC tendon edge.

STUDY DESIGN

Case-control study; Level of evidence, 3.

METHODS

The authors retrospectively evaluated 187 patients who underwent ARCR for full-thickness tears using the SB technique; intraoperative biopsy samples were taken to assess the degree of histological degeneration using the Bonar score. The cohort was divided into healed (n = 165) and retear (n = 22) groups according to magnetic resonance imaging results obtained ≥6 months postoperatively. The evaluation included preoperative patient data (age, sex, symptom duration, trauma history, history of heavy manual work, smoking habit, hypertension, diabetes mellitus, and hyperlipidemia) and radiological data (Hamada classification, Patte classification, Goutallier classification, and global fatty degeneration index [GFDI]). Additionally, intraoperative data (anteroposterior tear size, Lafosse classification for concomitant subscapularis tendon tear, and long head of biceps injury) and preoperative and postoperative clinical findings (active range of motion, University of California, Los Angeles [UCLA], score) were evaluated.

RESULTS

The retear rate was 11.8%. The retear group had a higher percentage of men (P = .031), higher Bonar score (P < .001), higher mean GFDI value (P = .002), higher rate of tear retraction degree (P = .010), and larger anteroposterior tear size (P = .020) than the healed group. The retear group had lower postoperative internal rotation (P = .031) and lower UCLA score (P < .001). Multivariate logistic regression analysis with a stepwise variable selection revealed anteroposterior tear size (odds ratio [OR], 2.4; 95% CI, 1.3-4.5; P = .004) and Bonar score (OR, 1.7; 95% CI, 1.3-2.4; P < .001) as independent predictors for a retear.

CONCLUSION

The results indicate that end-stage severe tendon degeneration might affect retear. Therefore, further investigation on the progression mechanisms of tendon degeneration and development of methods to assess degenerative tissue might improve clinical outcomes after ARCR.

Association of Coracoacromial Ligament Degeneration With Rotator Cuff Tear Patterns and Retear Rate

Background

Coracoacromial ligament (CAL) degeneration is thought to be a factor in external impingement in bursal-sided rotator cuff tears, but CAL release is associated with adverse effects.

Purpose

To investigate the association between CAL degeneration and the patterns of massive rotator cuff tears using multiple modalities and to assess the effect of CAL degeneration on supraspinatus tendon retear rates.

Study Design

Cohort study; Level of evidence, 2.

Methods

The authors prospectively recruited 44 patients who had undergone arthroscopic rotator cuff repair without acromioplasty or CAL release. Preoperative radiographs and magnetic resonance imaging (MRI) scans were reviewed to determine acromial morphology and CAL thickness, respectively. Rotator cuff tears were categorized as isolated supraspinatus or massive (involvement of ≥2 tendons), with massive tears categorized using the Collin classification. Acromial degeneration was analyzed using the Copeland-Levy classification. The CAL was biopsied intraoperatively and histologically analyzed using the Bonar score. At 6-month follow-up, the integrity of the repaired supraspinatus tendon was analyzed on MRI using the Sugaya classification. Finally, the associations among CAL degeneration, rotator cuff tear pattern, and arthroscopic grading were investigated.

Results

Patients with Collin type B rotator cuff tear had significantly higher CAL Bonar scores than those with Collin type A or isolated supraspinatus tears (10.0 vs 6.8 and 3.4; P = .03 and P < .001, respectively). Patients with a degenerative acromial undersurface of Copeland-Levy stage 2 or 3 had CALs with significantly higher Bonar scores than those with an intact acromial undersurface (8.4 and 8.2 vs 3.5; P = .034 and P = .027, respectively). The CAL Bonar scores of patients with different stages of the 6-month postoperative Sugaya classification were comparable (6.5, 7.2, 8.0, and 7.8 for stages 1, 2, 3, and 4, respectively; P = .751).

Conclusion

CAL degeneration was more severe in anterosuperior-type massive rotator cuff tears. Interestingly, even without acromioplasty, the severity of CAL degeneration did not affect the retear rate of the supraspinatus tendon.

Parishin A-loaded mesoporous silica nanoparticles modulate macrophage polarization to attenuate tendinopathy

Macrophages are involved mainly in the balance between inflammation and tenogenesis during the healing process of tendinopathy. However, etiological therapeutic strategies to efficiently treat tendinopathy by modulating macrophage state are still lacking. In this study, we find that a small molecule compound Parishin-A (PA) isolated from Gastrodia elata could promote anti-inflammatory M2 macrophage polarization by inhibiting gene transcription and protein phosphorylation of signal transducers and activators of transcription 1. Local injection or sustained delivery of PA by mesoporous silica nanoparticles (MSNs) could almost recover the native tendon's dense parallel-aligned collagen matrix in collagenase-induced tendinopathy by modulating macrophage-mediated immune microenvironment and preventing heterotopic ossification. Especially, MSNs decrease doses of PA, frequency of injection and yield preferable therapeutic effects. Mechanistically, intervention with PA could indirectly inhibit activation of mammalian target of rapamycin to repress chondrogenic and osteogenic differentiation of tendon stem/progenitor cells by influencing macrophage inflammatory cytokine secretion. Together, pharmacological intervention with a natural small-molecule compound to modulate macrophage status appears to be a promising strategy for tendinopathy treatment.

Effect of PARP-1 Inhibition on Rotator Cuff Healing: A Feasibility Study Using Veliparib in a Rat Model of Acute Rotator Cuff Repair

BACKGROUND

PARP-1 (poly[ADP-ribose]) was shown to influence the inflammatory response after rotator cuff tear, leading to fibrosis, muscular atrophy, and fatty infiltration in mouse rotator cuff degeneration. So far, it is not known how PARP-1 influences enthesis healing after rotator cuff tear repair.

HYPOTHESIS/PURPOSE

This study aimed to examine the feasibility of oral PARP-1 inhibition and investigate its influence on rat supraspinatus enthesis and muscle healing after rotator cuff repair. The hypothesis was that oral PARP-1 inhibition would improve enthesis healing after acute rotator cuff repair in a rat model.

STUDY DESIGN

Controlled laboratory study.

METHODS

In 24 Sprague-Dawley rats, the supraspinatus tendon was sharply detached and immediately repaired with a single transosseous suture. The rats were randomly allocated into 2 groups, with the rats in the inhibitor group receiving veliparib with a target dose of 12.5 mg/kg/d via drinking water during the postoperative recovery period. The animals were sacrificed 8 weeks after surgery. For the analysis, macroscopic, biomechanical, and histologic methods were used.

RESULTS

Oral veliparib was safe for the rats, with no adverse effects observed. In total, the inhibitor group had a significantly better histologic grading of the enthesis with less scar tissue formation. The macroscopic cross-sectional area of the supraspinatus muscles was 10.5% higher (P = .034) in the inhibitor group, which was in agreement with an 8.7% higher microscopic muscle fiber diameter on histologic sections (P < .0001). There were no statistically significant differences in the biomechanical properties between the groups.

CONCLUSION

This study is the first to investigate the influence of PARP-1 inhibition on healing enthesis. On the basis of these findings, we conclude that oral veliparib, which was previously shown to inhibit PARP-1 effectively, is safe to apply and has beneficial effects on morphologic enthesis healing and muscle fiber size.

CLINICAL RELEVANCE

Modulating the inflammatory response through PARP-1 inhibition during the postoperative healing period is a promising approach to improve enthesis healing and reduce rotator cuff retearing. With substances already approved by the Food and Drug Administration, PARP-1 inhibition bears high potential for future translation into clinical application.

Large extracellular vesicles secreted by human iPSC-derived MSCs ameliorate tendinopathy via regulating macrophage heterogeneity

Tendinopathy is a common musculoskeletal disorder which results in chronic pain and reduced performance. The therapeutic effect of stem cell derived-small extracellular vesicles (sEVs) for tendinopathy has been validated in recent years. However, whether large extracellular vesicles (lEVs), another subset of extracellular vesicles, possesses the ability for the improvement of tendinopathy remains unknown. Here, we showed that lEVs secreted from iPSC-derived MSCs (iMSC-lEVs) significantly mitigated pain derived from tendinopathy in rats. Immunohistochemical analysis showed that iMSC-lEVs regulated the heterogeneity of infiltrated macrophages and several inflammatory cytokines in rat tendon tissue. Meanwhile, in vitro experiments revealed that the M1 pro-inflammatory macrophages were repolarized towards M2 anti-inflammatory macrophages by iMSC-lEVs, and this effect was mediated by regulating p38 MAPK pathway. Moreover, liquid chromatography-tandem mass spectrometry analysis identified 2208 proteins encapsulated in iMSC-lEVs, including 134 new-found proteins beyond current Vesiclepedia database. By bioinformatics and Western blot analyses, we showed that DUSP2 and DUSP3, the negative regulator of p38 phosphorylation, were enriched in iMSC-lEVs and could be transported to macrophages. Further, the immunomodulatory effect of iMSC-lEVs on macrophages was validated in explant tendon tissue from tendinopathy patients. Taken together, our results demonstrate that iMSC-lEVs could reduce inflammation in tendinopathy by regulating macrophage heterogeneity, which is mediated via the p38 MAPK pathway by delivery of DUSP2 and DUSP3, and might be a promising candidate for tendinopathy therapy.

•

iMSC-lEVs significantly ameliorate tendinopathy both in a rat model and explant tendon tissue from human patient.

•

iMSC-lEVs modulate macrophages polarization via p38 MAPK signaling pathway.

•

Proteomics analysis of iMSC-lEVs discovers a new set of 134 proteins beyond current Vesiclepedia Database.

•

The p38 MAPK signaling pathway-mediated macrophage repolarization was partly regulated by the delivery of DUSP2 and DUSP3.

•

The immunoregulatory function of iMSC-lEVs are similar with iMSC-sEVs.

Bioactive glass-elicited stem cell-derived extracellular vesicles regulate M2 macrophage polarization and angiogenesis to improve tendon regeneration and functional recovery

Effective countermeasures for tendon injury remains unsatisfactory. Mesenchymal stem cell-derived extracellular vesicles (MSC-EVs)-based therapy via regulation of Mφ-mediated angiogenesis has emerged as a promising strategy for tissue regeneration. Still, approaches to tailor the functions of EVs to treat tendon injuries have been limited. We reported a novel strategy by applying MSC-EVs boosted with bioactive glasses (BG). BG-elicited EVs (EV_B) showed up-regulation of medicinal miRNAs, including miR-199b-3p and miR-125a-5p, which play a pivotal role in M2 Mφ-mediated angiogenesis. EV_B accelerated angiogenesis via the reprogrammed anti-inflammatory M2 Mφs compared with naïve MSC-EVs (EV_N). In rodent Achilles tendon rupture model, EV_B local administration activated anti-inflammatory responses via M2 polarization and led to a spatial correlation between M2 Mφs and newly formed blood vessels. Our results showed that EV_B outperformed EV_N in promoting tenogenesis and in reducing detrimental morphological changes without causing heterotopic ossification. Biomechanical test revealed that EV_B significantly improved ultimate load, stiffness, and tensile modulus of the repaired tendon, along with a positive correlation between M2/M1 ratio and biomechanical properties. On the basis of the boosted nature to reprogram regenerative microenvironment, EV_B holds considerable potential to be developed as a next-generation therapeutic modality for enhancing functional regeneration to achieve satisfying tendon regeneration.

Decellularized Bovine Pericardial Patch Loaded With Mesenchymal Stromal Cells Enhance the Mechanical Strength and Biological Healing of Large-to-Massive Rotator Cuff Tear in a Rat Model

PURPOSE

The purpose of this study was to determine whether the addition of decellularized bovine pericardial patch loaded with mesenchymal stromal cells enhanced bone-to-tendon healing and improved the biomechanical strength of large-to-massive rotator cuff tears in a small animal model.

METHODS

Adipose-derived mesenchymal stromal cells (MSCs) from rat inguinal fat were isolated, cultured, and loaded onto decellularized bovine pericardium patches. To simulate large-to-massive tears, rats were managed with free cage activity for 6 weeks after tear creation. A total of 18 rats were randomly allocated to repair-only (control), repair with pericardial patch augmentation (patch), or repair with MSC loaded pericardial patch augmentation (patch-MSC). Each group had 6 rats (one shoulder of each rat was used for histological evaluation and another for biomechanical evaluation). MSCs seeded on the pericardial patches were traced on four shoulders from 2 other rats at 4 weeks after surgery. Histological evaluation for bone-to-tendon healing and biomechanical testing was carried out at 8 weeks after repair.

RESULTS

MSCs tagged with a green fluorescent protein were observed in the repair site 4 weeks after the repair. One shoulder each in the control and patch groups showed complete discontinuity between the bone and tendon. One shoulder in the control group showed attenuation with only a tenuous connection. Fibrocartilage and tidemark formation at the bone-to-tendon interface (P = .002) and collagen fiber density (P = .040) and orientation (P = .003) were better in the patch-MSC group than in the control or patch group. Load-to-failure in the patch-MSC and patch groups was higher than that in the control group (P = .001 and .009, respectively).

CONCLUSION

Decellularized bovine pericardial patches loaded with adipose-derived and cultured mesenchymal stromal cells enhanced healing in terms of both histology and mechanical strength at 8 weeks following rotator cuff repair in a rat model.

CLINICAL RELEVANCE

Large-to-massive rotator tears need a strategy to prevent retear and enhance healing. The addition of decellularized bovine pericardial patch loaded with MSCs can enhance bone-to-tendon healing and improve biomechanical healing of large-to-massive rotator cuff tears following repair.

Quantification method to objectively evaluate the fibrous structural status of tendons based on polarization-sensitive OCT

Histological analysis is widely used to evaluate injured tendons; however, it has the limitation of being semi-quantitative. Hence, we developed a quantification method to objectively evaluate the fibrous structure of tendons, exhibiting the optical property of birefringence, using polarization-sensitive optical coherence tomography (PS-OCT). We used a partial-rupture rat model in which the middle 0.75 cm of the Achilles tendon was cut with a blade. Rats were sacrificed at 2, 4 or 6 weeks after the injury, and PS-OCT and histological analyzes were performed. The PS-OCT phase retardation images and score well represented the structural changes of the injured tendon according to the wound healing state. Therefore, the proposed novel quantification method using PS-OCT can be used to evaluate the fibrous structural status of tendons.

Platelet-rich Plasma in the Management of Shoulder Disorders: Basic Science and Implications Beyond the Rotator Cuff

Platelet-rich plasma (PRP) is an autologous mixture produced by centrifugal separation of whole blood. Understanding the clinical efficacy of PRP remains a challenge in the field of sports medicine, including the treatment of various shoulder conditions. Animal studies have examined the biologic actions of PRP on the rotator cuff tendon and shoulder capsule. Human studies have reported the outcomes of PRP in the management of subacromial impingement syndrome, rotator cuff tears, frozen shoulder, and glenohumeral osteoarthritis. These studies highlight the role of PRP in the nonsurgical management of these conditions and its utilization in the perioperative setting to augment tissue healing and optimize the surgical outcomes. The role of PRP as an adjunct therapy in patients undergoing rotator cuff repair has been in the spotlight during the last decade; however, a limited number of studies have examined the role of PRP in the management of non-rotator cuff shoulder conditions. This article aims to provide an overview of the biologic actions of PRP on shoulder tissues and to summarize the outcomes of PRP injection in patients with rotator cuff and non-rotator cuff disease of the shoulder. We sought to organize the existing literature and to provide recommendations on the use of PRP in various shoulder conditions, based on the existing evidence.

Feasibility of Neovessel Embolization in a Large Animal Model of Tendinopathy: Safety and Efficacy of Various Embolization Agents

Targeting neovessels in chronic tendinopathies has emerged as a new therapeutic approach and several embolization agents have been reported. The aim of this study was to investigate the feasibility of embolization with different agents in a porcine model of patellar tendinopathy and evaluate their safety and efficacy. Eight 3-month-old male piglets underwent percutaneous injection of collagenase type I to induce patellar tendinopathies (n = 16 tendons). They were divided into four groups (2 piglets, 4 tendons/group): the control group, 50–100 µm microspheres group, 100–300 µm microspheres group, and the Imipenem/Cilastatin (IMP/CS) group. Angiography and embolization were performed for each patellar tendon on day 7 (D7). The neovessels were evaluated visually with an angiography on day 14. The pathological analysis assessed the efficacy (Bonar score, number of neovessels/mm²) and safety (off-target persistent cutaneous ischemic modifications and presence of off-target embolization agents). The technical success was 92%, with a failed embolization for one tendon due to an arterial dissection. Neoangiogenesis was significantly less important in the embolized groups compared to the control group angiographies (p = 0.04) but not with respect to histology (Bonar score p = 0.15, neovessels p = 0.07). Off-target cutaneous embolization was more frequently depicted in the histology of the 50–100 µm microspheres group (p = 0.02). Embolization of this animal model with induced patellar tendinopathy was technically feasible with different agents and allowed assessing the safety and efficacy of neovessel destruction. Particles smaller than 100 µm seemed to be associated with more complications.

Quantitative analysis of tendon histopathology using digital pathology in rat models with Achilles tendon injury

Although digital image analysis methods that quantify histopathologic features have emerged, no validated quantitative methods are available to evaluate tendon injury. This study aimed to propose and validate a quantitative analysis method to identify the histopathologic features of tendon injuries. The histopathologic features of two Achilles tendon injury models (a partial full-thickness defect model and a collagenase injection model) using Sprague-Dawley rats were evaluated by semiquantitative grading and a quantitative analysis method using a digital pathology software at weeks 1 and 4 after tendon injury (six tendons per group at each time point). The outcome variables between tendon injury models and between time points were compared, and the correlation between semiquantitative scores and the results of the quantitative analysis was investigated. The proposed analysis method quantified the severity of the histopathological features after tendon injury. Quantitative analysis differentiated the cell morphology between tendon injury models and time points better than semiquantitative scoring. The results from quantitative measurements correlated significantly with the semiquantitative scores. The proposed quantitative method can be effective in evaluating the histopathology of tendon injuries.

Morphofunctional reorganization of plantar aponeurosis in experimental modeling of fasciopathy by synthetic analogue of prostaglandin E1

Foundation. Chronic plantar fasciopathic pain syndrome is a pathology that significantly affects the quality of life of patients of all age categories. Insufficient knowledge of the etiological and pathogenetic factors in the development of fasciopathies explains the multiplicity, and sometimes inconsistency, of conservative and surgical treatment regimens. The choice of the optimal variant of therapeutic or surgical intervention may be associated with experimental modeling of fasciopathies and the study of the dynamics of the pathological process.The aim. To study the morphological changes in structures identical to the human plantar aponeurosis in experimental modeling of fasciopathy in animals.Research methods. The material for the study was fragments of the tendonaponeurotic complex of the foot of laboratory animals (control group: animals with the introduction of physiological sodium chloride solution (n = 12); main group: animals with the introduction of alprostadil (n = 12)). The methods of light microscopy (staining with alcian and toluidine blue, according to Van Gieson, Weigert – Van Gieson and Picro-Mallory) and morphometry were used.Results and discussion. As a result of the study, it was found that the four-fold administration of alprostadil had a significant effect on the structure of the dense fibrous connective tissue of the plantar foot of laboratory animals. The mechanisms of damage (edema, microhemorrhages, infiltration by lymphocytes, plasmocytes and leukocytes, dystrophy by the type of mucoid and fibrinoid swelling, delamination and rupture of collagen fibers), adaptation and regeneration (the appearance of a large number of activated fibrocytes, fibroblasts, microvessels, neoplasm of collagen fibers) were activated. All this together led to spatial focal histotopographic changes, consisting in an increase in the cellular composition of connective tissue structures against the background of a noticeable violation of their spatial orientation.Conclusion. Modeling of fasciopathy using alprostadil was accompanied by the appearance of mosaic reversible and irreversible heteromorphic and heterochronous changes in all connective tissue aponeurotic structures. Such histotopographic changes should be considered as one of the reasons for the clinical manifestations of plantar fasciopathies, causing functional insufficiency and explaining the clinical recurrent nature of the pathological process.

Extracellular Vesicles Delivered by Injectable Collagen Promote Bone-Tendon Interface Healing and Prevent Fatty Degeneration of Rotator Cuff Muscle

PURPOSE

This study aimed (1) to confirm the maintenance of the extracellular vesicles (EVs) delivered via injectable collagen at the application site, and (2) to evaluate the effect of EVs derived from the human umbilical cord-derived mesenchymal stem cells and loaded in an injectable collagen gel after rotator cuff repair (RCR).

METHODS

Rabbits (n = 20) were assigned to normal (N), repair-only (R), and those administered with injectable collagen after repair (RC), and EV-laden injectable collagen after repair (RCE) groups. The EVs isolated by ultra-centrifugation from the human umbilical cord-derived mesenchymal stem cells spent medium were mixed with collagen and administered accordingly. After 12 weeks, the rabbits were sacrificed to evaluate the healing of the bone-to-tendon junction and the fatty degeneration of muscle. Histomorphometric scoring for bone-tendon interface, fatty infiltration (%), and biomechanical tests were performed. Separately, groups of 3 rabbits were assigned to 3 different time points to evaluate maintenance of green fluorescence-labeled EVs with injectable collagen via tracking on the bursal side of the rotator cuff (3 groups: 3 days, 2, and 4 weeks).

RESULTS

The EVs delivered by injectable collagen remained until 4 weeks at the bursal side of the cuff tissue. The RCE group showed a significantly greater histomorphometric total score (P < .001, and P = .013, respectively) and significantly lower fatty degeneration than the RC and R groups (P = .001, and P = .013, respectively). The biomechanical tests revealed significant growing trends in load-to-failure and stiffness (P = .002, and P = .013, respectively), in the R, RC, RCE, and N groups.

CONCLUSIONS

EVs mounted in injectable collagen remained at the repair site for at least 4 weeks after application. Furthermore, they effectively promote bone-to-tendon healing via collagen maturation in bone-tendon interface and preventing fatty degeneration of rotator muscle after RCR as compared with collagen-only or repair-only groups.

CLINICAL RELEVANCE

The combination of collagen with EVs significantly promotes rotator cuff healing demonstrating potential clinical application during partial rotator cuff tear or after RCR.

Injectable bioactive glass/sodium alginate hydrogel with immunomodulatory and angiogenic properties for enhanced tendon healing

Tendon healing is a complex process involving inflammation, proliferation, and remodeling, eventually achieving a state of hypocellularity and hypovascularity. Currently, few treatments can satisfactorily restore the structure and function of native tendon. Bioactive glass (BG) has been shown to possess immunomodulatory and angiogenic properties. In this study, we investigated whether an injectable hydrogel fabricated of BG and sodium alginate (SA) could be applied to enhance tenogenesis following suture repair of injured tendon. We demonstrated that BG/SA hydrogel significantly accelerated tenogenesis without inducing heterotopic ossification based on histological analysis. The therapeutic effect could attribute to increased angiogenesis and M1 to M2 phenotypic switch of macrophages within 7 days post-surgery. Morphological characterization demonstrated that BG/SA hydrogel partially reverted the pathological changes of Achilles tendon, including increased length and cross-sectional area (CSA). Finally, biomechanical test showed that BG/SA hydrogel significantly improved ultimate load, failure stress, and tensile modulus of the repaired tendon. In conclusion, administration of an injectable BG/SA hydrogel can be a novel and promising therapeutic approach to augment Achilles tendon healing in conjunction with surgical intervention.

A Biomechanical Analysis of Peroneus Brevis Split Lesions, Repair, and Partial Resection

BACKGROUND

Peroneus brevis tendon tears are associated with chronic ankle pain and instability following sprain injuries. The aim of this study is to elucidate the biomechanical changes induced by a peroneus brevis split and surgical treatment by tubularizing suture or partial resection.

METHODS

Nine human lower leg specimens were biomechanically tested. Preexisting tendon pathology was ruled out by magnetic resonance imaging and histology. Specimens were subjected to sequential testing of 4 conditions of the peroneus brevis tendon: (1) native, (2) longitudinal lesion, (3) tubularizing suture, and (4) 50% resection. The outcome parameters were the tendon stiffness (N/mm) and the length variation of the split portion at 5 N load.

RESULTS

The median specimen age at death was 55.8 years (range 50-64 years). The longitudinal tendon split led to an elongation by 1.21 ± 1.15 mm, which was significantly reduced by tubularizing suture to 0.24 ± 0.97 mm (P = .021). Furthermore, 50% resection of the tendon elongated it by a mean 2.45 ± 1.9 mm (P = .01) and significantly reduced its stiffness compared to the intact condition (4.7 ± 1.17 N/mm, P = .024) and sutured condition (4.76 ± 1.04 N/mm, P = .011).

CONCLUSION

Longitudinal split and 50% resection of the peroneus brevis tendon led to elongation and loss of tendon stiffness. These properties were improved by tubularizing suture. The significance of these changes in the clinical setting needs further investigation.

CLINICAL RELEVANCE

Tubularizing suture of a peroneus brevis split can restore biomechanical properties to almost native condition, potentially aiding ankle stability in symptomatic cases. A split lesion and partial resection of the tendon showed reduced stiffness and increased elongation.

Mechanical and strain behaviour of human Achilles tendon during in vitro testing to failure

The Achilles tendon is the strongest tendon in the human body but its mechanical behaviour during failure has been little studied and the basis of its high tensile strength has not been elucidated in detail. In the present study, healthy, human, Achilles tendons were loaded to failure in an anatomically authentic fashion while the local deformation and strains were studied in real time, with very high precision, using digital image correlation (DIC). The values determined for the strength of the Achilles tendon were at the high end of those reported in the literature, consistent with the absence of a pre-existing tendinopathy in the samples, as determined by careful gross inspection and histology. Early in the loading cycle, the proximal region of the tendon accumulated high lateral strains while longitudinal strains remained low. However, immediately before rupture, the mid-substance of the Achilles tendon, its weakest part, started to show high longitudinal strains. These new insights advance the understanding of the mechanical behaviour of tendons as they are stretched to failure.

Stem cell sheet interpositioned between the tendon and bone would be better for healing than stem cell sheet overlaid above the tendon-to-bone junction in rotator cuff repair of rats

Background

Although stem cells might enhance natural enthesis healing in surgical rotator cuff repair, not much attention has been given to the delivery and location of delivering stem cells. The purpose of this study to know where to locate those stem cells during repair.

Methods

Animal model of chronic rotator cuff tear was created in 24 rats. Adipose-derived stem cells were engineered as a sheet and transplanted 1) between a torn tendon and humerus (interposition group) or 2) over a repaired tendon-to-bone junction (overlay group) at the time of surgical repair. Tracking of stem cells with overexpression of green fluorescent protein (GFP) were carried out at the time of sacrifice in additional 4 shoulders in each group. Histological and Biomechanical evaluation was performed to compare the differences in tendon-to-bone healing.

Results

Histology showed increased fibrocartilage, a clear boundary at the mineralized fibrocartilage, abundant collagen type III, and higher total scores, especially in the interposition group. GFP-overexpression was observed at the transplanted site at 2 weeks after repair. Although two groups where stem cell sheets applied showed higher load to failure than the repair-only group, the load to failure was not different between the interposition and overlay group.

Conclusion

In the chronic rotator cuff repair model, stem cell sheets enhanced regeneration of the tendon-to-bone junction. This regeneration was effective when the stem cell sheet was interpositioned at the tendon-to-bone interface.

Level of evidence

Basic Science Study; In Vivo Animal Model; Histology and Biomechanics.

Advances in Microscopic Studies of Tendinopathy: Literature Review and Current Trends, with Special Reference to Neovascularization Process

Tendinopathy is a process of chaotic extracellular matrix remodeling followed by increased secretion of enzymes and mediators of inflammation. The histopathological assessment of tendinous tissue is crucial to formulate the diagnosis and establish the severity of tendon degeneration. Nevertheless, the microscopic analysis of tendinous tissue features is often challenging. In this review, we aimed to compare the most popular scales used in tendon pathology assessment and reevaluate the role of the neovascularization process. The following scores were evaluated: the Bonar score, the Movin score, the Astrom and Rausing Score, and the Soslowsky score. Moreover, the role of neovascularization in tendon degeneration was reassessed. The Bonar system is the most commonly used in tendon pathology. According to the literature, hematoxylin and eosin with additional Alcian Blue staining seems to provide satisfactory results. Furthermore, two observers experienced in musculoskeletal pathology are sufficient for tendinopathy microscopic evaluation. The control, due to similar and typical alterations in tendinous tissue, is not necessary. Neovascularization plays an ambiguous role in tendon disorders. The neovascularization process is crucial in the tendon healing process. On the other hand, it is also an important component of the degeneration of tendinous tissue when the regeneration is incomplete and insufficient. The microscopic analysis of tendinous tissue features is often challenging. The assessment of tendinous tissue using the Bonar system is the most universal. The neovascularization variable in tendinopathy scoring systems should be reconsidered due to discrepancies in studies.

Histopathology of long head of biceps tendon removed during tenodesis demonstrates degenerative histopathology and not inflammatory changes

Background

The aim of this study is to describe and quantitatively analyze the histopathology of proximal long head biceps (LHB) tendinopathy in patients who have undergone LHB tenodesis. The hypothesis is that severe histopathologic changes of the LHB tendon (LHBT) will most likely be reflected with improved postoperative clinical outcomes.

Methods

The study included patients with isolated LHB tendinopathy or LHB tendinopathy associated with concomitant shoulder pathologies. All had failed conservative treatment (12 months) and had a positive pain response (> 50% reduction) pre-operatively after LHB tendon injection with local anesthetic. All underwent biceps tenodesis procedure between 2008 and 2014. Tendon specimens were collected and histologically analyzed with the semi-quantitative Bonar scoring system. Minimum follow-up time was 1 year. A subset of patients was retrospectively reviewed postoperatively and evaluated employing visual analogue score (VAS), short form survey (SF-12), American Shoulder and Elbow Surgeon (ASES) score, Disability of Arm, Shoulder and Hand (DASH) score, and Oxford Shoulder Score (OSS) and postoperative return to work status.

Results

Forty-five biceps tendon specimens were obtained from 44 patients (mean age 50 ± 9.6 years). Histopathological analyses demonstrated advanced degenerative changes with myxoid degeneration and marked collagen disorganization. Minimal inflammation was identified. There were no regional differences in histopathological changes. Clinical outcomes did not correlate significantly with severity of histopathologic changes.

Conclusions

This study confirms that LHBT specimens in patients undergoing tenodesis demonstrate with the use of the Bonar score histopathologic changes of chronic degeneration and not inflammation. The correct histopathologic terminology for this process is LHB tendinosis. The histopathological changes appear uniform throughout the entire length of the LHBT which may inform the nature of the procedure performed.

Investigating the histological and structural properties of tendon gel as an artificial biomaterial using the film model method in rabbits

Purpose

This study aimed to evaluate the properties of tendon gel by investigating the histological and structural differences among tendon gels under different preservation periods using a rabbit model.

Methods

Forty mature female rabbits were divided into four groups, each containing ten rabbits, on the basis of in-vivo preservation periods of tendon gels (3, 5, 10, and 15 days). We created the Achilles tendon rupture models using the film model method to obtain tendon gels. Tensile stress was applied to the tendon gel to promote maturation. Histological and structural evaluations of the tendon gel were performed before and after applying the tensile force, and the results obtained from the four groups were compared.

Results

Although the day-3 and day-5 tendon gels before applying tensile stress were histologically more immature than the day-10 and day-15 gels, type I collagen fibers equivalent to those of normal tendons were observed in all groups after the tensile process. Based on the surface and molecular structural evaluations, the day-3 tendon gels after the tensile process were molecularly cross-linked, and thick collagen fibers similar to those present in normal tendons were observed. Structural maturation observed in the day-3 tendon gels caused by traction was hardly observed in the day-5, -10, and -15 tendon gels.

Conclusions

The day-3 tendon gel had the highest regenerative potential to become a normal tendon by applying a traction force.

Supplementary Information

The online version contains supplementary material available at 10.1186/s40634-021-00434-y.

Modelling gluteus medius tendon degeneration and repair in a large animal model

INTRODUCTION

Gluteus medius tendon tears often occur in the context of chronic tendinopathy and remain a difficult clinical problem. Surgical repair is challenging as it is often delayed and performed in degenerative tendons. No animal model currently exists to mimic the delayed repair of tendinopathic gluteus medius tears. The aims of this study were to develop a chronic model of gluteus medius tendinopathy and tear and then compare this model to an acute gluteus medius tear and repair.

MATERIALS AND METHODS

Six gluteus medius muscles were dissected and examined in mature sheep to confirm anatomical similarity to the human counterpart. Ten separate adult sheep underwent tendon detachment, followed by relook and histological sampling at 6 and 16 weeks to assess the extent of tendon degeneration. Six adult sheep underwent tendon repair at 6 weeks and were later assessed for healing of the tendon and compared to a further four adult sheep who underwent an acute tendon detachment and repair procedure.

RESULTS

The sheep gluteus medius muscle consisted of three compartments, the anterior, middle and posterior. All compartments inserted via the common tendon on the superolateral aspect of the greater trochanter. At both 6 and 16 weeks, there was significant tendinopathic changes on histology compared to controls as assessed by modified Movin's score (p = 0.018, p = 0.047) but no difference between the 6- and 16-week groups (p = 0.25). There were significant differences between delayed and acute repair in both histological appearance (p = 0.025) and biomechanical properties (p = 0.019), with acute repair superior in both.

CONCLUSIONS

Tendon detachment for 6 weeks is sufficient to produce histological changes similar to chronic tendinopathy and repair of this degenerative tendon results in significantly poorer healing when compared to an acute repair model. Animal models for gluteus medius tears should use a delayed repair model to improve clinical validity.

No differences in histopathological degenerative changes found in acute, trauma-related rotator cuff tears compared with chronic, nontraumatic tears

PURPOSE

Acute trauma-related rotator cuff tears are believed to have better healing potential than chronic tears due to less degenerative changes of the tendons. However, the histopathological condition of tendons from trauma-related tears is not well investigated. The purpose of this study was to explore specific histopathological features in tendons from acute trauma-related full-thickness rotator cuff tears and to compare them to findings in tendons from nontraumatic, chronic tears.

METHODS

In a prospective cohort study, 62 previously asymptomatic patients [14 women, median age 61 years (range 42-75)] with trauma-related full-thickness rotator cuff tears were consecutively included. Arthroscopic repair was performed within 30 (median, IQR 25-37) days after the injury. During surgery, tissue biopsies were harvested from the supraspinatus tendons in 53 (86%) of the patients. In addition, similar biopsies were harvested from 10 patients undergoing surgery for chronic tears without history of trauma. All tissue samples were examined by a well-experienced pathologist under light microscope. Tendon degeneration was determined using the Bonar score whereas immunostaining was used for proliferation (Ki67), inflammation (CD45), apoptosis (p53) and haemosiderin staining to study traces of bleeding.

RESULTS

The median (IQR) Bonar score for the acute trauma-related biopsies was 10.5 (7.5-14.5) compared to 11 (5-12.8) for the control group with no statistically significant difference between the groups. No statistically significant between-group difference was found for the inflammatory index whereas tendons from patients with trauma-related full-thickness rotator cuff tears had statistically significantly higher apoptosis [3.1 (0.5-8.9) vs. 0.1 (0-1.5), p = 0.003] and proliferation [4.0 (1.8-6.9) vs. 0.4 (0-2.0), p = 0.001) indices than those undergoing surgery for chronic tears. Positive haemosiderin staining was found in 34% of tissue samples from patients with trauma-related tears compared to 10% in the control group (n.s).

CONCLUSION

This study suggests that there is no difference with regard to degenerative changes between supraspinatus tendons harvested from patients with acute, trauma-related rotator cuff tears and patients with nontraumatic, chronic tears.

LEVEL OF EVIDENCE

II.

Mesenchymal Stem Cells From a Hypoxic Culture Can Improve Rotator Cuff Tear Repair

A rotator cuff tear is an age-related common cause of pain and disability. Studies including our previously published ones have demonstrated that mesenchymal stem cells cultured under hypoxic conditions [hypoxic multipotent stromal cells (MSCs)] facilitate the retention of transplanted cells and promote wound healing. However, there are very few, if any, reports targeting the punctured supraspinatus tendons to create more or equally serous wounds as age-related tears of rotator cuff. It remains to be determined whether transplantation of bone-marrow-derived hypoxic MSCs into the punctured supraspinatus tendon improves tendon repair and, when combined with ultrasound-guided delivery, could be used for future clinical applications. In this study, we used a total of 33 Sprague-Dawley rats in different groups for normal no-punched control, hypoxic MSC treatment, nontreated vehicle control, and MSC preparation, and then evaluated treatment outcomes by biomechanical testing and histological analysis. We found that the ultimate failure load of the hypoxic MSC-treated group was close to that of the normal tendon and significantly greater than that of the nontreated vehicle control group. In vivo tracking of cells labeled with superparamagnetic iron oxide (SPIO) nanoparticles revealed an enhanced retention of transplanted cells at the tear site. Our study demonstrates that hypoxic MSCs improve rotator cuff tear repair in a rat model.

Collagenase-Induced Patellar Tendinopathy with Neovascularization: First Results towards a Piglet Model of Musculoskeletal Embolization

Background: Therapeutic strategies targeting neovessels responsible for musculoskeletal chronic pain have emerged, including neovessels embolization. Our study aimed to develop a large animal model of patellar tendinopathy with neovascularization. Methods: Nine 3-month-old male piglets (18 patellar tendons) received percutaneous injections of increasing doses of collagenase (0 to 50 mg) at day 0 (D0). Tendinopathy was evaluated by ultrasound (D7 and D14). Neovascularization was evaluated visually and on angiographies. Bonar score was used for histological analysis (D14). Correlations were evaluated using Spearman’s rank (Rs) test. Results: Research protocol was well tolerated. All tendons were enlarged with a median increase of 31.58% [25–40.28] at D7 (p = 0.244) at D7 and 57.52% [48.41–91.45] at D14 (p = 0.065). Tendons with collagenase injection had more hypoechoic changes, with one tendon rupture (p = 0.012). Neovascularization was reported above 5 mg collagenase (p < 0.01) at D7 and D14 with dose-related neovessels induction (Rs = 0.8, p < 0.001). The Bonar score increased above 5 mg collagenase, correlated with the dose (Rs = 0.666, p = 0.003). Conclusions: The study shows the feasibility, safety and reproducibility of this new large animal model of patellar tendinopathy with neovascularization after collagenase injection. It will allow studying new treatments on direct embolization of neovessels by endovascular approach.

CTRP3 exacerbates tendinopathy by dysregulating tendon stem cell differentiation and altering extracellular matrix composition

Tendinopathy, the most common disorder affecting tendons, is characterized by chronic disorganization of the tendon matrix, which leads to tendon tear and rupture. The goal was to identify a rational molecular target whose blockade can serve as a potential therapeutic intervention for tendinopathy. We identified C1q/TNF-related protein-3 (CTRP3) as a markedly up-regulated cytokine in human and rodent tendinopathy. Overexpression of CTRP3 enhanced the progression of tendinopathy by accumulating cartilaginous proteoglycans and degenerating collagenous fibers in the mouse tendon, whereas CTRP3 knockdown suppressed the tendinopathy pathogenesis. Functional blockade of CTRP3 using a neutralizing antibody ameliorated overuse-induced tendinopathy of the Achilles and rotator cuff tendons. Mechanistically, CTRP3 elicited a transcriptomic pattern that stimulates abnormal differentiation of tendon stem/progenitor cells and ectopic chondrification as an effect linked to activation of Akt signaling. Collectively, we reveal an essential role for CTRP3 in tendinopathy and propose a potential therapeutic strategy for the treatment of tendinopathy.

First immunohistochemical evidence of human tendon repair following stem cell injection: A case report and review of literature

BACKGROUND

Current clinical treatment options for symptomatic, partial-thickness rotator cuff tear (sPTRCT) offer only limited potential for true tissue healing and improvement of clinical results. In animal models, injections of adult stem cells isolated from adipose tissue into tendon injuries evidenced histological regeneration of tendon tissue. However, it is unclear whether such beneficial effects could also be observed in a human tendon treated with fresh, uncultured, autologous, adipose derived regenerative cells (UA-ADRCs). A specific challenge in this regard is that UA-ADRCs cannot be labeled and, thus, not unequivocally identified in the host tissue. Therefore, histological regeneration of injured human tendons after injection of UA-ADRCs must be assessed using comprehensive, immunohistochemical and microscopic analysis of biopsies taken from the treated tendon a few weeks after injection of UA-ADRCs.

CASE SUMMARY

A 66-year-old patient suffered from sPTRCT affecting the right supraspinatus and infraspinatus tendon, caused by a bicycle accident. On day 18 post injury [day 16 post magnetic resonance imaging (MRI) examination] approximately 100 g of abdominal adipose tissue was harvested by liposuction, from which approximately 75 × 10⁶ UA-ADRCs were isolated within 2 h. Then, UA-ADRCs were injected (controlled by biplanar X-ray imaging) adjacent to the injured supraspinatus tendon immediately after isolation. Despite fast clinical recovery, a follow-up MRI examination 2.5 mo post treatment indicated the need for open revision of the injured infraspinatus tendon, which had not been treated with UA-ADRCs. During this operation, a biopsy was taken from the supraspinatus tendon at the position of the injury. A comprehensive, immunohistochemical and microscopic analysis of the biopsy (comprising 13 antibodies) was indicative of newly formed tendon tissue.

CONCLUSION

Injection of UA-ADRCs can result in regeneration of injured human tendons by formation of new tendon tissue.

Effects of focused continuous pulsed electromagnetic field therapy on early tendon-to-bone healing

Aims

Rotator cuff (RC) tears are common musculoskeletal injuries which often require surgical intervention. Noninvasive pulsed electromagnetic field (PEMF) devices have been approved for treatment of long-bone fracture nonunions and as an adjunct to lumbar and cervical spine fusion surgery. This study aimed to assess the effect of continuous PEMF on postoperative RC healing in a rat RC repair model.

Methods

A total of 30 Wistar rats underwent acute bilateral supraspinatus tear and repair. A miniaturized electromagnetic device (MED) was implanted at the right shoulder and generated focused PEMF therapy. The animals’ left shoulders served as controls. Biomechanical, histological, and bone properties were assessed at three and six weeks.

Results

Extension of the tendon from preload to the maximum load to failure was significantly better in the PEMF-treated shoulders at three weeks compared to controls (p = 0.038). The percentage strain was significantly higher in the PEMF group at both timepoints (p = 0.037). Collagen organization was significantly better (p = 0.034) as was tissue mineral density in the PEMF-treated group at three weeks (p = 0.028). Tendon immunohistochemistry revealed a prominent increase in type I collagen at the repair site at three weeks following continuous PEMF treatment compared with controls. None of the other tested parameters differed between the groups.

Conclusion

MED-generated PEMF may enhance early postoperative tendon-to-bone healing in an acute rat supraspinatus detachment and repair model. Superior biomechanical elasticity parameters together with better collagen organization suggest improved RC healing.

Cite this article: Bone Joint Res 2021;10(5):298–306.

The Bonar Score in the Histopathological Assessment of Tendinopathy and Its Clinical Relevance-A Systematic Review

This study aimed to perform a comprehensive systematic review, which reports the role of the Bonar score in the histopathological assessment of tendinopathy and its clinical relevance. To identify all of the studies that reported relevant information on the Bonar scoring system and tendinopathy, an extensive search of the major and the most significant electronic databases (PubMed, Cochrane Central, ScienceDirect, SciELO, Web of Science) was performed. A systematic review of the literature was conducted according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. The extracted data included—year of study, geographical location, type of the study, radiological modifications, gender, number of patients, region of tendinopathy, mean age, control group, characteristics of the Bonar score and alterations in the scale, mean Bonar score, number of investigators, area of tendon investigation, clinical and radiological implications. An extensive search of the databases and other sources yielded a total of 807 articles. Eighteen papers were finally included in this systematic review, and of these, 13 original papers included the clinical and radiological implications of tendinopathy. Radiological evaluation was present in eight studies (both magnetic resonance imaging (MRI) and ultrasound (US)). The clinical implications were more frequent and present in 10 studies. Using the Bonar score, it is easy to quantify the pathological changes in tendinous tissue. However, its connection with clinical and radiological evaluation is much more complicated. Based on the current state of knowledge, we concluded that the neovascularization variable in the Bonar system should be reconsidered. Ideally, the microscopic assessment score should follow the established classification scale with the radiological and clinical agreement and should have a prognostic value.

Photobiomodulation therapy increases collagen II after tendon experimental injury

A tendon is a mechanosensitive tissue that transmits muscle-derived forces to bones. Photobiomodulation (PBM), also known as low-level laser therapy (LLLT), has been used in therapeutic approaches in tendon lesions, but uncertainties regarding its mechanisms of action have prevented its widespread use. We investigated the response of PBM therapy in experimental lesions of the Achilles tendon in rats. Thirty adult male Wistar rats weighing 250 to 300 g were surgically submitted to bilateral partial transverse section of the Achilles tendon. The right tendon was treated with PBM, whereas the left tendon served as a control. On the third postoperative day, the rats were divided into three experimental groups consisting of ten rats each, which were treated with PBM (Konf, Aculas - HB 750), 780 nm and 80 mW for 20 seconds, three times/week for 7, 14 and 28 days. The rats were sacrificed at the end of the therapeutic time period. The Sca-1 was examined by immunohistochemistry and histomorphometry, and COLA1, COLA2 and COLA3 gene expression was examined by qRT-PCR. COLA2 gene expression was higher in PBM treated tendons than in the control group. The histomorphometric analysis coincided with increased number of mesenchymal cells, characterized by Sca-1 expression in the lesion region (p<0.001). PBM effectively interferes in tendon tissue repair after injury by stimulating mesenchymal cell proliferation and the synthesis of collagen type II, which is suggested to provide structural support to the interstitial tissues during the healing process of the Achilles tendon. Further studies are needed to confirm the role of PBM in tendon healing.

Relationship between long head of the biceps tendon histopathology and long-term functional results in smokers. A time to reevaluate the Bonar score?

Aim

The purpose of this study was to investigate whether there is an association between smoking, the extent of the degeneration process in the biceps tendinopathy, including cells and extracellular matrix (ECM) alterations, and long-term surgical results.

Methods

This study comprised 40 consecutive patients admitted for shoulder arthroscopy due to symptomatic biceps tendinopathy and classified into three groups based on smoking status: active smokers, former smokers, and non-smokers. According to the classical Bonar score criteria, the histopathologic evaluation of the harvested intra-articular portion of the tendon was done. The follow-up examination was based on the American Shoulder and Elbow Surgeons Score (ASES).

Results

A cohort of 32 patients was enrolled in the final follow-up examination; mean 37.56 months. Histopathological evaluation according to the classical Bonar score revealed degeneration of the tendinous tissue in each group but there was no correlation between the extent of degeneration, smoking indexes and the ASES. After revision of Bonar scale within the vascularity criterion, we found a correlation between the extent of degeneration of tendinous tissue, smoking data, ASES score, and the severity of rotator cuff injury.

Conclusion

In this paper, we indicate the ambiguous role of the neovascularization in the biceps tendinopathy, and it was used for modification of the classical Bonar score. Consequently, recalculated, modified Bonar score was correlated positively with smoking indexes and functional outcomes. Furthermore, the morphological alterations of rotator cuff tendons also correlated positively with the extent of biceps tendon degeneration, measured according to the modified scoring system.

The expression of substance P and calcitonin gene-related peptide is associated with the severity of tendon degeneration in lateral epicondylitis

BACKGROUND

In this study, we investigated whether substance P (SP) or calcitonin gene-related peptide (CGRP) expression is associated with tendon degeneration in patients with lateral epicondylitis.

METHODS

Twenty-nine patients who underwent surgical treatment for lateral epicondylitis were enrolled in the final analyses. Extensor carpi radialis brevis tendon origins were harvested for histological analysis.

RESULTS

SP and CGRP immunostaining were negative in healthy tendons but positive in degenerative tendons; moreover, their immunoreactivity increased with degeneration severity. Univariate analysis indicated that variables such as the preoperative visual analog scale (VAS) score or SP or CGRP expression levels were significantly associated with the Movin score. However, multivariate analysis revealed that only higher SP and/or CGRP signals were associated with higher Movin scores. Elevations in SP or CGRP expression were also linked with significantly severe preoperative VAS scores.

CONCLUSION

We demonstrated that tendon degeneration severity is associated with increased SP and CGRP expression in the biopsy samples of lateral epicondylitis.

Subacromial bursal preservation can enhance rotator cuff tendon regeneration: a comparative rat supraspinatus tendon defect model study

BACKGROUND

The role of subacromial bursa in rotator cuff surgery is unknown. This study aimed to assess the subacromial bursa's role in the healing of supraspinatus tendon injury in a rat model.

METHODS

Twenty-three male Sprague-Dawley rats (9 weeks old; weight, approximately 296 g) were used in this study. Three rats used as biomechanical study controls were killed at 12 weeks of age. A supraspinatus tendon defect was made bilaterally in 20 rats, whereas an additional subacromial bursa sectioning was performed on the left side. Six rats were killed for biomechanical testing and 4 were killed for histologic observation at 3 and 9 weeks, respectively.

RESULTS

The regenerated tendon in the bursal preservation group showed significantly superior biomechanical properties in maximum load to failure at 3 and 9 weeks and stiffness at 9 weeks after surgery compared with the bursal removal group. The modified Bonar scale scores showed better regenerated supraspinatus tendons in the bursal preservation group.

CONCLUSION

The present study found that the subacromial bursa plays an important role in rotator cuff regeneration in this rat supraspinatus injury model. Extensive bursectomy of the subacromial bursa may not be recommended in rotator cuff repair surgery, though future in vivo human studies are needed to confirm these observations.

Histopathological and immunohistochemical investigation of the local and systemic effects of tranexamic acid on the healing of the Achilles tendon in rats

OBJECTIVES

This study aims to compare the effects of systemic and local applications of tranexamic acid (TXA) on tendon healing using a rat Achilles tendon injury model.

PATIENTS AND METHODS

Thirty-six adult male albino Wistar rats (aging 3-4 months; weighing 350 to 400 g) were used in this study conducted between December 2019 and January 2020. The Achilles tendon was performed bilateral tenotomy and surgically repaired. Postoperatively, 1 mL of TXA was administered to each leg locally in the local group, whereas 2 mL of TXA was intraperitoneally administered in the systemic group. The control group was left untreated. Half of the rats were sacrificed on Day 15 and the other half on Day 30. Tendon healing was evaluated with the Bonar and the Movin scoring systems and immunohistochemical methods.

RESULTS

The systemic group had the highest Bonar and Movin scores on Day 15. All groups exhibited tendon healing on Day 30, with no significant differences among the groups. The tenocyte morphology was found to be more impaired in both TXA groups on Day 30 (p=0.013). Ground substance scores were lower in the systemic group on Day 30 (p=0.028). The fiber structure and arrangement scores were higher in the systemic group on Day 15 (p=0.007 and p=0.032). Immunohistochemical analyses showed that galectin-3 values exhibited a significant difference in all groups on Day 30 (p=0.020). In all groups, it was determined that type I collagen values showed an increasing trend on Day 30, compared to the values on Day 15, whereas type III collagen values showed a decreasing trend.

CONCLUSION

Our results demonstrated that local and systemic use of TXA does not impair tendon healing. Although advanced studies are needed, our study suggests that TXA application reduces the development of fibrosis.

Sustained Exposure of Substance P Causes Tendinopathy

Recently, neuromediators such as substance P (SP) have been found to be important factors in tendon homeostasis. Some studies have found SP to be the cause of inflammation and tendinopathy, whereas others have determined it to be a critical component of tendon healing. As demonstrated by these conflicting findings, the effects of SP on tendinopathy remain unclear. In this study, we hypothesized that the duration of SP exposure determines its effect on the tendons, with repetitive long-term exposure leading to the development of tendinopathy. First, we verified the changes in gene and protein expression using in vitro tenocytes with 10-day exposure to SP. SP and SP + Run groups were injected with SP in their Achilles tendon every other day for 14 days. Achilles tendons were then harvested for biomechanical testing and histological processing. Notably, tendinopathic changes with decreased tensile strength, as observed in the Positive Control, were observed in the Achilles in the SP group compared to the Negative Control. Subsequent histological analysis, including Alcian blue staining, also revealed alterations in the Achilles tendon, which were generally consistent with the findings of tendinopathy in SP and SP + Run groups. Immunohistochemical analysis revealed increased expression of SP in the SP group, similar to the Positive Control. In general, the SP + Run group showed worse tendinopathic changes. These results suggest that sustained exposure to SP may be involved in the development of tendinopathy. Future research on inhibiting SP is warranted to target SP in the treatment of tendinopathy and may be beneficial to patients with tendinopathy.

Correlation between smoking and neovascularization in biceps tendinopathy: a functional preoperative and immunohistochemical study

Aims

The purpose of this study was to investigate whether smoking is associated with neovascularization in the tendinopathy of the long head of the biceps tendon (LHBT).

Methods

The study included 40 consecutive patients who underwent arthroscopic biceps tenotomy/tenodesis due to chronic biceps tendinopathy and divided into three groups: (1) non-smokers, (2) former smokers, (3) smokers. LHBT tissue samples were stained with H&E, Alcian blue and Trichrome staining. Immunohistochemical examination was performed using anti-CD31 and anti-CD34. The neovessel density score (NDS) was scored by Bonar criteria.

Results

The mean period of smoking was 15.50 years with an average number of 24 cigarettes/day in the former smokers and 21.69 years with an average number of 15 cigarettes/day in the active smokers. The mean NDS was 2.23/3 in non-smokers, whereas it was 1.60/3 in former smokers and 1.31/3 in active smokers. The mean American Shoulder and Elbow Surgeons score equaled 46 in never smoked patients, 43.60 in former smokers, and 41.46 in active smokers. In the patients with smoking history, the disorganized tendinous tissue islands were avascular and composed of compact acidic polysaccharides and mucopolysaccharides. We observed negative correlation between the NDS and the smoking indexes, including cigarettes per day (p = 0.0150), smoking years (p = 0.0140), pack-years (p = 0.0088).

Conclusion

In conclusion, the present study revealed that smoking impairs the vascularization of the biceps tendon in chronic tendinopathy. Clinically, we observed a negative correlation between smoking and neovascularization. Furthermore, there was no correlation between neovascularization and functional preoperative status.

Tendon Regeneration After Partial-Thickness Peroneus Longus Tendon Harvesting: Magnetic Resonance Imaging Evaluation and In Vivo Animal Study

BACKGROUND

In recent years, the use of the anterior half of the peroneus longus tendon (AHPLT) as an autograft source for ligament reconstruction has gained popularity. However, no reports are available regarding tendon regeneration after harvesting of the AHPLT.

HYPOTHESIS

When half of the tendon is preserved during tendon harvesting, the quality of the regenerated tendon is better than that of the regenerated tendon after full-thickness harvesting.

STUDY DESIGN

Case series; Level of evidence, 4; controlled laboratory study.

METHODS

A total of 21 patients who underwent AHPLT harvesting for lower extremity ligament reconstruction participated in the magnetic resonance imaging (MRI) study to evaluate tendon regeneration 1 year after the harvesting. An in vivo animal study was performed to compare the quality of the regenerated tendon after partial-thickness and full-thickness tendon harvesting. A total of 30 adult female Sprague-Dawley rats were allocated to 2 groups-15 rats underwent partial-thickness Achilles tendon harvesting (partial-thickness harvesting [PTH] group), and 15 rats underwent full-thickness Achilles tendon harvesting (full-thickness harvesting [FTH] group). The quality of the regenerated tendons was compared 180 days after tendon harvesting.

RESULTS

All 21 patients showed regeneration of the peroneus longus tendon (PLT) (homogeneously dark on both T1- and T2-weighted sequences). The cross-sectional area of the regenerated tendon divided by that of the preoperative tendon was 92.6% and 84.5% at 4 cm and 9 cm proximal to the tip of the distal fibula, respectively. In the animal study, the mean histologic score was better for the PTH group compared with the FTH group (9.17 ± 1.35 vs 14.72 ± 0.74; P < .001). The ultimate strength and the stiffness of the regenerated Achilles tendon were significantly higher for the PTH group compared with the FTH group (35.5 ± 8.3 vs 22.4 ± 8.3 N, P = .004; and 31.6 ± 7.7 vs 23.5 ± 4.8 N/mm, P = .016).

CONCLUSION

The PLT was found to regenerate after partial-thickness harvesting on MRI. In the animal study, the quality of the regenerated tendon when half of the tendon was preserved during tendon harvesting was better than that after full-thickness tendon harvesting.

Intraoperative and In Vitro Classification of Subacromial Bursal Tissue

PURPOSE

To classify subacromial bursal tissue using intraoperative and in vitro characteristics from specimens harvested during arthroscopic shoulder surgery.

METHODS

Subacromial bursa was harvested over the rotator cuff from 48 patients (57 ± 10 years) undergoing arthroscopic shoulder surgery. Specimens were characterized intraoperatively by location (over rotator cuff tendon or muscle), tissue quality (percent of either fatty or fibrous infiltration), and vascularity before complete debridement. Nucleated cell counts were determined after 3 weeks incubation and histological sections were reviewed for degree of fatty infiltration and vascularity. Mesenchymal stem cell surface markers were counted via flow cytometry (n = 3) and cellular migration was observed using a fluoroscopic assay (n = 3).

RESULTS

Intraoperatively, muscle bursa was found most often to have >50% fatty infiltration (n = 39), whereas tendon bursa showed majority fibrous tissue (n = 32). Cellular proliferation did not significantly differ according to intraoperative tissue quality. Intraoperative vascularity was associated with greater proliferation for highly vascular samples (P = 0.023). Tendon bursa demonstrated significantly greater proliferation potential than muscle bursa (P = 0.00015). Histologic assessment of fatty infiltration was moderately correlated with gross tissue fattiness (ρ = -0.626, P = 7.14 × 10^-11). Flow cytometry showed that 90% to 100% of bursal cells were positive for MSC surface markers. Peak cellular migration rates occurred between 18 and 30 hours' incubation.

CONCLUSIONS

Intraoperative and in vitro subacromial bursa characteristics were not found to reliably correlate with the degree of cellular proliferation. However, the anatomic location of subacromial bursa was consistently predictive of increased proliferation potential. Bursa-derived nucleated cells were confirmed to include mesenchymal stem cells with migratory potential.

CLINICAL RELEVANCE

The anatomic distinction between muscle and tendon bursa provides a simple classification for predicting cellular activity.