Intrinsic healing capacity and tearing process of torn supraspinatus tendons: in situ hybridization study of alpha 1 (I) procollagen mRNA

Humeral head coverage in arthroscopic partial repair of massive rotator cuff tears improves functional outcomes: an analysis of influential factors

BACKGROUND

Although partial rotator cuff repair has shown good outcomes, differences in clinical outcomes remain concerns. This study was performed to determine whether patients with humeral head coverage would show better functional outcomes than patients without humeral head coverage and to identify the factors for humeral head coverage after arthroscopic partial repair of massive tears.

METHODS

We performed a retrospective study of 63 patients with massive rotator cuff tears who underwent arthroscopic partial repair between 2012 and 2018. Two to four margin convergences were first performed; then, the Mason-Allen technique was performed. The patients were divided into 2 groups: those with humeral head coverage (38 cases) and those without humeral head coverage (25 cases). The following factors were evaluated: age; sex; hypertension; diabetes; osteoporosis; preoperative and postoperative pseudoparalysis, visual analog scale (VAS) pain score, Constant score, acromiohumeral distance, and subacromial bony spur; and subscapularis tear and repair. Muscle atrophy and fatty degeneration were evaluated by magnetic resonance imaging preoperatively, and the integrity of the repaired cuff was evaluated by ultrasonography at a minimum of 2 years after surgery.

RESULTS

Compared with preoperative values, significant improvements in VAS pain scores (from 6.27 to 2.32 in patients with humeral head coverage and from 7.00 to 2.81 in those without humeral head coverage) and Constant scores (from 51.35 to 75.95 and from 44.62 to 69.81, respectively) were observed in both groups (P < .001). Statistical analysis revealed that postoperative VAS pain scores (2.32 vs. 2.81) and Constant scores (75.95 vs. 69.81) in patients with humeral head coverage were superior to those in patients without humeral head coverage (P = .044 and P = .003, respectively). The integrity of the repaired cuff was evaluated by ultrasonography, and partial tears were found in 4 of 37 patients with humeral head coverage and 2 of 26 patients without humeral head coverage (P = .816). Univariable logistic regression analysis revealed that age (P < .001), comorbidity (P = .005), symptom duration (P = .023), preoperative shoulder mobility (P < .001), maintained acromiohumeral distance (P = .006), subscapularis tear (P = .026), and less preoperative supraspinatus and infraspinatus muscle atrophy (P = .001 and P = .010, respectively) had significant correlations with humeral head coverage.

CONCLUSIONS

Overall satisfactory results were achieved in most patients regardless of high retear rates, but patients with partial repair covering the humeral head were associated with better outcomes than patients without humeral head coverage. Multivariable regression analysis revealed that age (<70 years, P = .003), capability of shoulder mobility (P = .005), maintenance of the acromiohumeral space (>7 mm, P = .016), and less atrophy of the rotator cuff muscles (P = .021) were favorable factors to achieve humeral head coverage during surgical partial repair of massive rotator cuff tears.

The Weekend Warrior: Common Shoulder and Elbow Injuries in the Recreational Athlete

"Weekend warriors" are recreational athletes who compress their physical activity into 1-2 weekly exercise sessions. These individuals are generally older than the conventionally discussed athlete, and can live otherwise sedentary lifestyles that contribute to limited opportunities for regular exercise. The combination of high-energy physical activity with relative deconditioning, as well as older age and a potential history of competitive athletic play, can predispose these weekend warriors to a plethora of sports injuries. The shoulder and elbow are dynamically involved in a multitude of common recreational sports, such as baseball, softball, tennis, golf, and volleyball, and forms of casual exercise, such as swimming or climbing. A lack of proper conditioning and supplemental training in weekend warriors, particularly in comparison to elite athletes in these respective sports, can contribute to the development of both acute and chronic conditions of the shoulder and elbow. Inconsistency in physical activity can minimize the prominence of symptoms, leading patients to delayed presentations with injuries that severely impact their ability to engage in their exercise of choice, and therefore remain active at all. This narrative review aims to present the etiology, presentation, and management of common shoulder and elbow injuries that may afflict this patient population. Prevention strategies will also be discussed.

Optimal Management of Partial Thickness Rotator Cuff Tears: Clinical Considerations and Practical Management

Partial thickness rotator cuff tears have been diagnosed with increased frequency due to heightened awareness and an improvement in diagnostic modalities. When >50% of the tendon thickness has ruptured, intra-tendinous strain of the residual tendon increases. Surgery is generally confined to patients who have failed non-operative measures and have persistent symptoms. The rationale for repairing partial thickness tears lies in their limited self-healing capacity, and propensity to enlarge over time and progress to a full thickness defect. Although tear debridement and acromioplasty can improve pain and function, tear progression can occur, in addition to worse results being noted in bursal-sided defects. Several surgical strategies have been recommended but there is a lack of evidence to advocate one form of treatment over another. The aim of this narrative review is to discuss the treatment options for partial thickness tears of the rotator cuff.

Healing of partial tear of the supraspinatus tendon after atelocollagen injection confirmed by MRI: A case report

RATIONALE

Recently, collagen therapy has been made available for treating rotator cuff tendon injuries. However, to our knowledge, there are no clinical studies objectively investigating the effect of collagen therapy.

PATIENT CONCERNS

A 53-year-old female patient visited our pain clinic because of pain in the right shoulder. Although she had never experienced trauma and had not overused her shoulder and arm, the patient showed limited range of motion with painful arc syndrome. Moreover, the Neer test and Hawkins-Kennedy test were positive with subacromial tenderness.

DIAGNOSES

The MRI findings revealed partial tears on the articular surface of the anterior supraspinatus tendon in the rotator cuff.

INTERVENTIONS

The patient was treated with injections of exogenous collagen at the site of the partial tear under ultrasound guidance.

OUTCOMES

Follow-up MRI after injection of collagen revealed healing of the previous partial rupture of the tendon without any complications. Moreover, the patient reported reduction in pain and improvement in the movement of her shoulder during the follow-up period.

LESSONS

In this report, we demonstrate healing of a partial tear of the supraspinatus tendon in the rotator cuff after injection of exogenous collagen, as confirmed by MRI.

A quantitative label-free analysis of the extracellular proteome of human supraspinatus tendon reveals damage to the pericellular and elastic fibre niches in torn and aged tissue

Tears of the human supraspinatus tendon are common and often cause painful and debilitating loss of function. Progressive failure of the tendon leading to structural abnormality and tearing is accompanied by numerous cellular and extra-cellular matrix (ECM) changes in the tendon tissue. This proteomics study aimed to compare torn and aged rotator cuff tissue to young and healthy tissue, and provide the first ECM inventory of human supraspinatus tendon generated using label-free quantitative LC-MS/MS. Employing two digestion protocols (trypsin and elastase), we analysed grain-sized tendon supraspinatus biopsies from older patients with torn tendons and from healthy, young controls. Our findings confirm measurable degradation of collagen fibrils and associated proteins in old and torn tendons, suggesting a significant loss of tissue organisation. A particularly marked reduction of cartilage oligomeric matrix protein (COMP) raises the possibility of using changes in levels of this glycoprotein as a marker of abnormal tissue, as previously suggested in horse models. Surprisingly, and despite using an elastase digestion for validation, elastin was not detected, suggesting that it is not highly abundant in human supraspinatus tendon as previously thought. Finally, we identified marked changes to the elastic fibre, fibrillin-rich niche and the pericellular matrix. Further investigation of these regions may yield other potential biomarkers and help to explain detrimental cellular processes associated with tendon ageing and tendinopathy.

Effects of lidocaine on torn rotator cuff tendons

We determined lidocaine's action on torn rotator cuff tendons in vitro and in vivo. For in vitro experiments, cell proliferation and viability assays were performed using tenocytes derived from human torn rotator cuff tendons. For in vivo experiments, acute rotator cuff tears were made on the supraspinatus tendons in the rats' bilateral shoulders; before closure, lidocaine was injected into the shoulder and saline into the contralateral shoulder (control). After sacrifice, the specimens underwent biomechanical testing or histological analysis at 24 h and at 2, 4, and 8 weeks after surgery. The extent of collagen organization and apoptosis were semi-quantitatively evaluated using collagen picrosirius red staining. Apoptosis was examined using TUNEL staining and electron microscopy. Cell proliferation decreased dose-dependently. After exposure to 0.1% lidocaine for 24 h, cell viability decreased. Two and 4 weeks after surgery, the ultimate load to failure decreased more in the lidocaine group than in the control group, with significantly reduced stiffness in the lidocaine group 2 weeks after surgery. Collagen organization significantly decreased in the lidocaine group by 4 weeks after surgery but returned to baseline at 8 weeks. TUNEL staining detected numerous apoptotic tenocytes at the torn tendon edge exposed to lidocaine 24 h after surgery; electron microscopy confirmed the condensed cell nuclei. These changes were not observed in controls. Lidocaine caused cytotoxicity to tenocytes under both conditions, decreased biomechanical properties, and induced apoptosis and delay of collagen organization in this model. Subacromial lidocaine injections in patients with rotator cuff tears should be performed carefully. © 2016 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 34:1620-1627, 2016.

Does application of moderately concentrated platelet-rich plasma improve clinical and structural outcome after arthroscopic repair of medium-sized to large rotator cuff tear? A randomized controlled trial

BACKGROUND

Platelet-rich plasma (PRP) has the potential to improve tendon-bone healing. The evidence is still controversial as to whether PRP application after repair of medium-sized to large cuff tears leads to superior structural and clinical outcome, especially after single-row repair.

METHODS

In a randomized study, 102 patients (PRP group, 52 patients; control group, 50 patients) with medium-sized and large degenerative posterosuperior tears were included for arthroscopic repair with a minimum follow-up of 2 years. Patients were evaluated with clinical scores (visual analog scale score, Constant-Murley score, University of California-Los Angeles score, and American Shoulder and Elbow Surgeons score) and ultrasound to assess retear and vascularity pattern of the cuff.

RESULTS

Visual analog scale scores were significantly lower in the PRP group than in controls at 1 month, 3 months, and 6 months but not later. Constant-Murley scores were significantly better in the PRP group compared with controls at 12 and 24 months, whereas University of California-Los Angeles scores were significantly higher in the PRP group at 6 and 12 months (P < .05). The American Shoulder and Elbow Surgeons score in both groups was comparable at all the times. At 24 months, retear in the PRP group (n = 2; 3.8%) was significantly lower than in the control group (n = 10; 20%; P = .01). The retear difference was significant only for large tears (PRP:control group, 1:6; P = .03). Doppler ultrasound examination showed significant vascularity in the PRP group repair site at 3 months postoperatively (P < .05) and in peribursal tissue until 12 months.

CONCLUSION

Application of moderately concentrated PRP improves clinical and structural outcome in large cuff tears. PRP also enhances vascularity around the repair site in the early phase.

Evidence of healing of partial-thickness rotator cuff tears following arthroscopic augmentation with a collagen implant: a 2-year MRI follow-up

BACKGROUND

partial-thickness rotator cuff tears frequently enlarge due to increased local strain and often progress to full-thickness tears. Studies suggest the addition of new tendinous tissue to injured cuff tendons would significantly decrease peak strain, possibly protecting against tear progression. The aim of this study was to assess the ability of a highly-porous collagen implant to induce new tissue formation and limit tear progression when placed on the bursal surface of partial-thickness cuff tears.

METHODS

following arthroscopic subacromial decompression, the implant was attached to the bursal surface of the supraspinatus tendon in a prospective series of 13 consecutive patients with intermediate - (3-6 mm) to high-grade (>6 mm) partial - thickness cuff tears (5 articular, 3 bursal, 5 intra-substance). Tendon thickness, defect size, and tendon quality were evaluated using magnetic resonance imaging (MRI) preoperatively and at 3, 6, 12, and 24 months postoperatively. Clinical outcomes were assessed using the Constant and American Shoulder and Elbow Society scores at the same preoperative and follow-up times. All 13 patients completed all follow-up exams (mean length of follow-up 27.0 months, range 23.3-32.0); no patients were lost to follow-up.

RESULTS

the implant induced significant new tissue formation in all patients by 3 months (mean increase in tendon thickness 2.2 ± 0.26 mm). This tissue matured over time and became radiologically indistinguishable from the underlying tendon. The partial-thickness cuff tears showed consistent filling of the defects, with complete healing in 7 patients at 12 months, and a progressive improvement in tendon quality in the remaining patients. No tear progression was observed by MRI in any of the patients at 24 months. All clinical scores improved significantly over time. At 24 months, 12 of 13 patients (92%) had satisfactory or better results.

CONCLUSIONS

the results of this clinical study demonstrated the ability of a highly-porous collagen implant to induce new tendon-like tissue formation and create an environment conductive to the healing of partial-thickness cuff tears.

Effects of corticosteroids and hyaluronic acid on torn rotator cuff tendons in vitro and in rats

Corticosteroids (CS) or hyaluronic acid (HA) is used in subacromial injection for the conservative treatment of rotator cuff tears (RCT); this study addresses the question of how CS and HA affect the tendon tissue and fibroblasts in vitro and in rats. Cell proliferation assays were performed in human tendon fibroblasts from RCT. Rats underwent surgery to create RCT, and the surgical sites were injected with CS or HA. The rotator cuff tendons were subjected to biomechanical testing, microscopic and immunohistochemical analysis of proliferating cell nuclear antigen (PCNA), and ultrastructural analysis. Cell proliferation was significantly decreased with CS in vitro (p < 0.05). Maximal load of CS-treated tendons was significantly decreased compared with that of HA-treated tendons (p < 0.05), as well as PCNA(+) cells at 2 weeks (p < 0.05). Ultrastructural observations of the CS-treated rats detected apoptosis of tendon fibroblasts 24 h after surgery. Histological and biomechanical data 4 weeks after surgery were not significant among the three groups. Unlike HA, CS caused cell death, and inhibition of the proliferation of tendon fibroblasts, leading to a delay of tendon healing involved and a subsequent decrease of biomechanical strength at the surgical site.

Proteomics perspectives in rotator cuff research: a systematic review of gene expression and protein composition in human tendinopathy

BACKGROUND

Rotator cuff tendinopathy including tears is a cause of significant morbidity. The molecular pathogenesis of the disorder is largely unknown. This review aimed to present an overview of the literature on gene expression and protein composition in human rotator cuff tendinopathy and other tendinopathies, and to evaluate perspectives of proteomics--the comprehensive study of protein composition--in tendon research.

MATERIALS AND METHODS

We conducted a systematic search of the literature published between 1 January 1990 and 18 December 2012 in PubMed, Embase, and Web of Science. We included studies on objectively quantified differential gene expression and/or protein composition in human rotator cuff tendinopathy and other tendinopathies as compared to control tissue.

RESULTS

We identified 2199 studies, of which 54 were included; 25 studies focussed on rotator cuff or biceps tendinopathy. Most of the included studies quantified prespecified mRNA molecules and proteins using polymerase chain reactions and immunoassays, respectively. There was a tendency towards an increase of collagen I (11 of 15 studies) and III (13 of 14), metalloproteinase (MMP)-1 (6 of 12), -9 (7 of 7), -13 (4 of 7), tissue inhibitor of metalloproteinase (TIMP)-1 (4 of 7), and vascular endothelial growth factor (4 of 7), and a decrease in MMP-3 (10 of 12). Fourteen proteomics studies of tendon tissues/cells failed inclusion, mostly because they were conducted in animals or in vitro.

CONCLUSIONS

Based on methods, which only allowed simultaneous quantification of a limited number of prespecified mRNA molecules or proteins, several proteins appeared to be differentially expressed/represented in rotator cuff tendinopathy and other tendinopathies. No proteomics studies fulfilled our inclusion criteria, although proteomics technologies may be a way to identify protein profiles (including non-prespecified proteins) that characterise specific tendon disorders or stages of tendinopathy. Thus, our results suggested an untapped potential for proteomics in tendon research.

Rotator cuff tear: A detailed update

Rotator cuff tear has been a known entity for orthopaedic surgeons for more than two hundred years. Although the exact pathogenesis is controversial, a combination of intrinsic factors proposed by Codman and extrinsic factors theorized by Neer is likely responsible for most rotator cuff tears. Magnetic resonance imaging remains the gold standard for the diagnosis of rotator cuff tears, but the emergence of ultrasound has revolutionized the diagnostic capability. Even though mini-open rotator cuff repair is still commonly performed, and results are comparable to arthroscopic repair, all-arthroscopic repair of rotator cuff tear is now fast becoming a standard care for rotator cuff repair. Appropriate knowledge of pathology and healing pattern of cuff, strong and biological repair techniques, better suture anchors, and gradual rehabilitation of postcuff repair have led to good to excellent outcome after repair. As the healing of degenerative cuff tear remains unpredictable, the role of biological agents such as platelet-rich plasma and stem cells for postcuff repair augmentation is still under evaluation. The role of scaffolds in massive cuff tear is also being probed.

Biomechanical analysis of rotator cuff repairs with extracellular matrix graft augmentation

Despite advances in surgical techniques, 20% to 90% of rotator cuff (RTC) repairs fail. They tend to fail at the suture-tendon junction due to tension at the repair and gap formation prior to healing. This study evaluated the gap formation and ultimate tensile failure loads of a RTC repair with a decellularized human dermal allograft. Augmentation of a RTC repair with an extracellular matrix graft decreased gap formation and increased load to failure in a human RTC repair model.

Healing improvement after rotator cuff repair using gelatin-grafted poly(L-lactide) electrospun fibrous membranes

BACKGROUND

Rotator cuff tears (RCTs) are a common cause of shoulder pain and disability in middle and older age. Despite improvements in the understanding of this disease process and advances in surgical treatment, rotator cuff (RC) repair failure rates remain high. Insufficient healing capacity is likely the main factor for failure of reconstruction.

MATERIALS AND METHODS

We fabricated implantable biodegradable gelatin-grafted poly(L-lactide) (PLLA) fibrous membranes using electrospinning technology and evaluated them using in vitro cell proliferation assays. Then, we established chronic rat RCT models and randomly assigned rats into one of three groups. In group 1 (n = 48), the detached supraspinatus tendon was repaired to its anatomic footprint (transosseous repair). In groups 2 and 3, the rats underwent transosseous repair and were implanted with either pure PLLA membranes (n = 48) or gelatin-PLLA membranes (n = 48) to augment the repairs. The animals were killed at 2, 4, and 8 wk postoperatively, which was followed by histomorphometric and biomechanical evaluation.

RESULTS

Histologic observations revealed that gelatin-PLLA membranes have excellent biocompatibility and biodegradability. At 2, 4, and 8 wk postoperatively, the gelatin-PLLA membranes significantly increased the area of glycosaminoglycan staining at the tendon-bone interface compared with the control group (P < 0.05) and significantly improved collagen organization, as measured by birefringence under polarized light at the healing enthesis compared with the control and PLLA groups (P < 0.05). Biomechanical testing revealed that the gelatin-PLLA group had a greater ultimate load to failure and stiffness than the control group at 4 and 8 wk (P < 0.05). The gelatin-PLLA membranes had the highest stress of the healing enthesis.

CONCLUSIONS

Local application of gelatin-PLLA fibrous membranes to the healing tendon-bone interface after RC repair in a rat chronic RCT model was found to strengthen the healing enthesis, increase the area of fibrocartilage, and improve collagen organization compared with repair alone. Augmentation with gelatin-grafted PLLA may enhance healing after RC repair and might eventually lead to improvement of clinical surgical outcomes.

Diagnostic accuracy of clinical examination features for identifying large rotator cuff tears in primary health care

OBJECTIVES

Rotator cuff tears are a common and disabling complaint. The early diagnosis of medium and large size rotator cuff tears can enhance the prognosis of the patient. The aim of this study was to identify clinical features with the strongest ability to accurately predict the presence of a medium, large or multitendon (MLM) rotator cuff tear in a primary care cohort.

METHODS

Participants were consecutively recruited from primary health care practices (n = 203). All participants underwent a standardized history and physical examination, followed by a standardized X-ray series and diagnostic ultrasound scan. Clinical features associated with the presence of a MLM rotator cuff tear were identified (P<0.200), a logistic multiple regression model was derived for identifying a MLM rotator cuff tear and thereafter diagnostic accuracy was calculated.

RESULTS

A MLM rotator cuff tear was identified in 24 participants (11.8%). Constant pain and a painful arc in abduction were the strongest predictors of a MLM tear (adjusted odds ratio 3.04 and 13.97 respectively). Combinations of ten history and physical examination variables demonstrated highest levels of sensitivity when five or fewer were positive [100%, 95% confidence interval (CI): 0.86-1.00; negative likelihood ratio: 0.00, 95% CI: 0.00-0.28], and highest specificity when eight or more were positive (0.91, 95% CI: 0.86-0.95; positive likelihood ratio 4.66, 95% CI: 2.34-8.74).

DISCUSSION

Combinations of patient history and physical examination findings were able to accurately detect the presence of a MLM rotator cuff tear. These findings may aid the primary care clinician in more efficient and accurate identification of rotator cuff tears that may require further investigation or orthopedic consultation.

The effect of unloading on gene expression of healthy and injured rotator cuffs

Tendon unloading following rupture of one of the rotator cuff tendons can induce alterations in muscle physiology and tendon structure, which can subsequently affect reparability and healing potential. Yet little is known about the effects of muscle and tendon unloading on the molecular response of the rotator cuff. We determined the effect of mechanical unloading on gene expression and morphology of healthy supraspinatus tendons and muscles, and the same muscles after acute injury and repair. Mechanical unloading was achieved by tenotomy and/or botulinum toxin A (BTX) chemical denervation in a rat rotator cuff model of injury and repair. Gene expression profiles varied across regions of the muscle, with the greatest changes seen in the distal aspect of the muscle for most genes. Myogenic and adipogenic genes were upregulated in muscle when unloaded (tenotomy and BTX). Tendon injury, with and without repair, resulted in upregulation of fibrosis- and tendon-specific gene expression. The expression of scleraxis, a transcription factor necessary for tendon development, was upregulated in response to injury and repair. In summary, tendon detachment and repair had the greatest effect on tendon gene expression, while unloading had the greatest effect on muscle gene expression.

Increased matrix metalloprotease-3 gene expression in ruptured rotator cuff tendons is associated with postoperative tendon retear

PURPOSE

The role of matrix metalloproteases (MMPs) in ruptured rotator cuff tendons remains unknown. This study aimed to investigate the gene expression of MMPs in ruptured rotator cuff tendons and to compare their expression levels between patients with and without postoperative tendon retear.

METHODS

Twenty-four patients (a median age of 61 years: interquartile range, 55-66 years) with full-thickness rotator cuff tears were examined in this study. The marginal site of the ruptured tendon was harvested during surgery. The mRNA expression levels of collagen types I and III, MMP-1, MMP-3, MMP-7, MMP-9, MMP-13, tissue inhibitor of MMP (TIMP)-1, and TIMP-2 were analysed by real-time reverse transcription polymerase chain reaction. Postoperative retear was evaluated by magnetic resonance imaging at a minimum of 1 year following surgery.

RESULTS

The mRNA expression levels of MMP-3 and TIMP-1 in ruptured rotator cuff tendons were significantly increased in patients with postoperative retear (n = 6), compared with patients without retear (n = 18) (P = 0.04). For collagens, MMP-1, MMP-7, MMP-9, MMP-13, and TIMP-2, there were no significant differences in the mRNA expression levels in ruptured tendons between patients with and without retear.

CONCLUSIONS

These results suggest that, in addition to up-regulation of TIMP-1 gene expression, increased MMP-3 gene expression in ruptured rotator cuff tendons is associated with postoperative tendon retear. Thus, drug therapy specifically targeting MMP-3 after rotator cuff repair should be considered in the future.

Management of degenerative rotator cuff tears: a review and treatment strategy

The aim of this review was to present an over view of degenerative rotator cuff tears and a suggested management protocol based upon current evidence. Degenerative rotator cuff tears are common and are a major cause of pain and shoulder dysfunction. The management of these tears is controversial, as to whether they should be managed non-operatively or operatively. In addition when operative intervention is undertaken, there is question as to what technique of repair should be used. This review describes the epidemiology and natural history of degenerative rotator cuff tears. The management options, and the evidence to support these, are reviewed. We also present our preferred management protocol and method, if applicable, for surgical fixation of degenerative rotator cuff tears.

Collagen production at the edge of ruptured rotator cuff tendon is correlated with postoperative cuff integrity

PURPOSE

The purpose was to evaluate the correlation between messenger RNA (mRNA) expression of collagen at the edge of the ruptured rotator cuff tendon and postoperative cuff integrity.

METHODS

The edge of the ruptured tendon was sampled during open rotator cuff surgery in 12 patients with full-thickness rotator cuff tears (mean age, 58.2 years). The mean period from symptom onset was 9.3 months (range, 1 to 36 months), and the mean tear size was 4.1 cm. As controls, rotator cuff tendons with no gross rupture were taken from 5 fresh cadavers. Production of type I and type III collagen was examined by real-time reverse transcription polymerase chain reaction. By use of magnetic resonance imaging, postoperative cuff integrity was evaluated based on the classification of Sugaya et al. and then scored, ranging from 5 points for type I to 1 point for type V.

RESULTS

Looking at the mRNA of type I and type III collagen in tendons, we found that the expression of mRNA for both collagen types in ruptured tendons was significantly greater than in control tendons (P = .0462 for type I collagen and P = .0306 for type III collagen). Correlating the mRNA of type I and type III collagen with repaired cuff integrity on postoperative magnetic resonance imaging, we found a close relation between expression of mRNA for both collagen types and postoperative rotator cuff integrity (r = 0.63 [P = .038] for type I collagen and r = 0.626 [P = .03] for type III collagen). Furthermore, expression of type I collagen mRNA showed a significant inverse correlation with the period from symptom onset (r = -0.845, P < .0005).

CONCLUSIONS

This study showed that expression of mRNA for type I and type III collagen at the edge of the ruptured rotator cuff tendon was significantly correlated with postoperative cuff integrity and that mRNA expression for type I collagen was significantly associated with the period from symptom onset. These results may suggest that conservative treatment should not be prolonged if patients do not respond within a certain period.

LEVEL OF EVIDENCE

Level III, prognostic case-control study.

Results of surgical management of symptomatic shoulders with partial thickness tears of the rotator cuff

INTRODUCTION

The optimal management of partial thickness tears of the rotator cuff (PTRCT) is still controversial.

SOURCE OF DATA

A literature search, on PubMed, Cochrane and Google Scholar databases, identified 273 relevant abstracts of articles published in peer-reviewed journals. Twenty-three clinical studies reporting the outcomes of surgically treated patients affected by PTRCTs were selected.

AREAS OF AGREEMENT

The different repair approaches results in variable functional outcomes. The Coleman Methodology Score (CMS) used to asses the quality of the studies showed great heterogeneity in study design, the sample, pre- and post-operative diagnostic assessments and the score used to evaluate outcomes. The mean CMS value was 67.95 (ranging from 30 to 82).

AREAS OF CONTROVERSY

The heterogeneity of the treatment options and of the outcome assessment methods makes it difficult to compare the results of the different studies.

GROWING POINTS

There is a need to use standardized pre- and post-operative assessment methods and functional outcome scores. To improve the diagnosis and to choose the best treatment, it may be useful to measure the thickness of the rotator cuff to ascertain whether the size correlates with outcome.

CONCLUSION

There is a lack of scientifically based guidelines, probably a result of the relatively low levels of evidence of the studies. There is a need for adequately powered randomized clinical trials, using standard diagnostic assessment, common and validated scoring system comparing reported outcomes and duration of follow-up greater than 2 years.

An analytical model for rotator cuff repairs

BACKGROUND

Currently, natural and synthetic scaffolds are being explored as augmentation devices for rotator cuff repair. When used in this manner, these devices are believed to offer some degree of load sharing; however, no studies have quantified this effect. Furthermore, the manner in which loads on an augmented rotator cuff repair are distributed among the various components of the repair is not known, nor is the relative biomechanical importance of each component. The objectives of this study are to (1) develop quasi-static analytical models of simplified rotator cuff repairs, (2) validate the models, and (3) predict the degree of load sharing provided by an augmentation scaffold.

METHODS

The individual components of the repair constructs were modeled as non-linear springs, and the model equations were formulated based on the physics of springs in series and parallel. The model was validated and used to predict the degree of load sharing provided by a scaffold. Parametric sensitivity analysis was used to identify which of the component(s)/parameter(s) most influenced the mechanical behavior of the augmented repair models.

FINDINGS

The validated models predict that load will be distributed approximately 70-80% to the tendon repair and approximately 20-30% to the augmentation component. The sensitivity analysis suggests that the greatest improvements in the force carrying capacity of a tendon repair may be achieved by improving the properties of the bone-suture-tendon interface. Future studies will perform parametric simulation to illustrate the manner in which changes to the individual components of the repair, representing different surgical techniques and scaffold devices, may influence the biomechanics of the repair construct.

Improved time-zero biomechanical properties using poly-L-lactic acid graft augmentation in a cadaveric rotator cuff repair model

HYPOTHESIS

Rotator cuff repair failure rates range from 20% to 90%, and failure is believed to occur most commonly by sutures cutting through the tendon due to excessive tension at the repair site. This study was designed to determine whether application of a woven poly-L-lactic acid device (X-Repair; Synthasome, San Diego, CA) would improve the mechanical properties of rotator cuff repair in vitro.

MATERIALS AND METHODS

Eight pairs of human cadaveric shoulders were used to test augmented and non-augmented rotator cuff repairs. Initial stiffness, yield load, ultimate load, and failure mode were compared.

RESULTS

Yield load was 56% to 92% higher and ultimate load was 56% to 76% higher in augmented repairs. No increase in initial stiffness was found. Failure by sutures cutting through the tendon was reduced, occurring in 17 of 20 non-augmented repairs but only 7 of 20 augmented repairs.

CONCLUSIONS

Our data show that application of the X-Repair device significantly increased the yield load and ultimate load of rotator cuff repairs in a human cadaveric model and altered the failure mode but did not affect initial repair stiffness.

Effect of sodium hyaluronate treatment on rotator cuff lesions without complete tears: a randomized, double-blind, placebo-controlled study

HYPOTHESIS

A randomized, double-blind, placebo-controlled study of sodium hyaluronate (ARTZ Dispo) treatment was performed in 51 patients with rotator cuff lesions without complete tears. We hypothesized that ARTZ Dispo would render better results than the placebo.

MATERIALS AND METHODS

Twenty-five patients (ARTZ Dispo group) had injections of 25 mg/wk of sodium hyaluronate into the subacromial bursa for 5 consecutive weeks. Twenty-six patients (placebo group) were given 2.5 mL of normal saline solution with the same injection protocol as the ARTZ Dispo group. No significant difference in age, height, weight, gender, vocation, involved shoulder, duration of symptoms, baseline Constant score, or visual analog scale (VAS) score existed between the 2 groups.

RESULTS

The 2 groups did not significantly differ with regard to Constant scores, VAS scores, or global improvement assessments 1 week after injections. The ARTZ Dispo group had a better Constant score (P = .0095) and VAS score (P = .0018) than the placebo group 6 weeks after treatment. Patients in the placebo group were given 5 sodium hyaluronate injections, rather than placebo, after disclosure of the blind list, if they wished. Forty-one patients who underwent hyaluronate injection exhibited a significantly improved Constant score, from 64.0 +/- 11.7 at baseline to 88.9 +/- 10.4 (P < .0001), and a significantly improved VAS score, from 6.4 +/- 1.3 to 1.5 +/- 1.6 (P < .0001), at a mean follow-up of 33.1 months. No significant adverse effect was noted.

CONCLUSIONS

Subacromial injections of sodium hyaluronate are effective in treating rotator cuff lesions without complete tears.

Preclinical models for translating regenerative medicine therapies for rotator cuff repair

Despite improvements in the understanding of rotator cuff pathology and advances in surgical treatment options, repairs of chronic rotator cuff tears often re-tear or fail to heal after surgery. Hence, there is a critical need for new regenerative repair strategies that provide effective mechanical reinforcement of rotator cuff repair as well as stimulate and enhance the patient's intrinsic healing potential. This article will discuss and identify appropriate models for translating regenerative medicine therapies for rotator cuff repair. Animal models are an essential part of the research and development pathway; however, no one animal model reproduces all of the features of the human injury condition. The rat shoulder is considered the most appropriate model to investigate the initial safety, mechanism, and efficacy of biologic treatments aimed to enhance tendon-to-bone repair. Whereas large animal models are considered more appropriate to investigate the surgical methods, safety and efficacy of the mechanical-or combination biologic/mechanical-strategies are ultimately needed for treating human patients. The human cadaver shoulder model, performed using standard-of-care repair techniques, is considered the best for establishing the surgical techniques and mechanical efficacy of various repair strategies at time zero. While preclinical models provide a critical aspect of the translational pathway for engineered tissues, controlled clinical trials and postmarketing surveillance are also needed to define the efficacy, proper indications, and the method of application for each new regenerative medicine strategy.

Extracellular matrix scaffold devices for rotator cuff repair

Rotator cuff tears affect 40% or more of those over age 60, and the repair failure rate of large to massive tears ranges from 20 to 90%. High re-tear rates are a result of mechanical factors as well as biologic factors that may compromise the patients' intrinsic capacity to heal. Hence, there is a critical need for repair strategies that provide adequate strength as well as stimulate and enhance healing potential. Tissue engineering strategies to improve rotator cuff repair healing include the use of scaffolds, growth factors, cell seeding or a combination of these approaches. Scaffolds have been the most common strategy investigated to date. Despite the growing clinical use of scaffold devices for rotator cuff repair, there are numerous questions related to their indication, surgical application, safety, mechanism of action and efficacy that remain to be clarified or addressed. The purpose of this paper is to review the current basic science and clinical understanding of extracellular matrix scaffolds, which are currently the most widely used scaffolds for rotator cuff repair. Our review will emphasize the host immune response and scaffold remodeling, the mechanical and suture retention properties of ECMs and preclinical and clinical studies on the use of ECMs for rotator cuff repair. We will then discuss the implications of these data on the future directions for use of these scaffolds in tendon repair procedures.

Outcome of nonoperative treatment of symptomatic rotator cuff tears monitored by magnetic resonance imaging

BACKGROUND

Rotator cuff tears are very common, but little is known about the outcome of nonoperative treatment of symptomatic tears in terms of progression and the need for surgical intervention.

METHODS

Fifty-nine shoulders in fifty-four patients (thirty-three women and a mean age of 58.8 years) with rotator cuff tears on initial magnetic resonance imaging who had been managed nonoperatively were studied retrospectively. All had magnetic resonance imaging scans acquired six months or more after the initial study. The progression of the rotator cuff tears was associated with age, anatomical and associated parameters, follow-up time, and structural and other magnetic resonance imaging findings.

RESULTS

Baseline magnetic resonance imaging scans demonstrated thirty-three full-thickness tears, twenty-six partial-thickness tears, and four combined full-thickness and partial-thickness tears. Fifty-eight of the fifty-nine tears involved the supraspinatus tendon, and ten involved multiple tendons. Progression in tear size occurred more often among the patients who were followed more than eighteen months (thirteen [48%] of twenty-seven shoulders) compared with those who were followed for less than eighteen months (six [19%] of thirty-two shoulders). Five tears (one partial-thickness tear) decreased in size. More than half (52%; seventeen) of the thirty-three full-thickness tears increased in size compared with 8% (two) of the twenty-six partial-thickness tears (p = 0.0005). Only 17% (six) of the thirty-five tears in patients who were sixty years old or less deteriorated compared with 54% (thirteen) of the twenty-four tears in patients who were more than sixty years old (p = 0.007). No shoulder in a patient with a partial-thickness tear demonstrated supraspinatus atrophy, whereas 24% of those with a full-thickness tear demonstrated atrophy (p = 0.007). The proportion with an increase in tear size was significantly larger for shoulders with fatty infiltration than for those without it (p = 0.0089).

CONCLUSIONS

Factors that are associated with progression of a rotator cuff tear are an age of more than sixty years, a full-thickness tear, and fatty infiltration of the rotator cuff muscle(s). In the long-term follow-up of nonoperatively treated rotator cuff tears, magnetic resonance imaging can be used to monitor rotator cuff changes and guide patient management.

Rotator cuff repair augmentation in a canine model with use of a woven poly-L-lactide device

BACKGROUND

Despite advances in surgical treatment options, failure rates of rotator cuff repair have continued to range from 20% to 90%. Hence, there is a need for new repair strategies that provide effective mechanical reinforcement of rotator cuff repair as well as stimulate and enhance the intrinsic healing potential of the patient. The purpose of this study was to evaluate the extent to which augmentation of acute repair of rotator cuff tendons with a newly designed poly-L-lactide repair device would improve functional and biomechanical outcomes in a canine model.

METHODS

Eight adult, male mongrel dogs (25 to 30 kg) underwent bilateral shoulder surgery. One shoulder underwent tendon release and repair only, and the other was subjected to release and repair followed by augmentation with the repair device. At twelve weeks, tendon retraction, cross-sectional area, stiffness, and ultimate load of the repair site were measured. Augmented repairs underwent histologic assessment of biocompatibility. In addition, eight pairs of canine cadaver shoulders underwent infraspinatus injury and repair with and without device augmentation with use of identical surgical procedures and served as time-zero biomechanical controls. Eight unpaired, canine cadaver shoulders were included as normal biomechanical controls.

RESULTS

At time zero, repair augmentation significantly increased the ultimate load (23%) (p = 0.034) but not the stiffness of the canine infraspinatus tendon repair. At twelve weeks, the poly-L-lactide scaffold was observed to be histologically biocompatible, and augmented repairs demonstrated significantly less tendon retraction (p = 0.008) and significantly greater cross-sectional area (137%), stiffness (26%), and ultimate load (35%) than did repairs that had not been augmented (p < 0.001, p = 0.002, and p = 0.009, respectively).

CONCLUSIONS

While limiting but not eliminating tendon repair retraction, the augmentation device provided a tendon-bone bridge and scaffold for host tissue deposition and ingrowth, resulting in improved biomechanical function of the repair at twelve weeks.

Tendon-bone insertion repair and regeneration using polyglycolic acid sheet in the rabbit rotator cuff injury model

BACKGROUND

The quality of tendons has considerable limitations regarding torn rotator cuff tendons. Tissue-engineering techniques using a biodegradable scaffold offer potential alternatives for recreating a valid tendon-to-bone interface.

HYPOTHESIS

A polyglycolic acid (PGA) sheet could facilitate the regeneration of the rotator cuff tendon insertion in vivo.

STUDY DESIGN

Controlled laboratory study.

METHODS

An implant consisting of a PGA sheet, a rapidly absorbable material, was used to replace a completely resected infra-spinatus tendon insertion in 33 adult Japanese white rabbits. The contralateral infraspinatus tendon was replaced by poly-L-lactate-epsilon-caprolactone (PLC), a slowly absorbable material, by the same methods based on the results of the pilot study. Histological comparisons were made at 4, 8, and 16 weeks, and mechanical evaluations were performed at 4 and 16 weeks in both groups. Unrepaired defects were created in a control group.

RESULTS

In the control group, the rotator cuff defects were covered with thin fibrous membranes with many fibroblasts arranged in an irregular pattern. In the PLC group, some chondrocytes were seen in the tendon insertion; however, these were not arranged along the long axis for a 16-week period. In the PGA group, a well-arranged fibrocartilage layer could be found in the regenerated tendon insertions; however, these tendon insertions were mainly regenerated by type III collagen. In mechanical examinations, the PGA group had significantly higher values in the maximum failure load, tensile strength, and Young's modulus for the 4-week and 16-week periods. These 3 categories statistically improved from 4 to 16 weeks postoperatively in both groups except for the Young's modulus in the PGA group (E = 5.66 at 4 weeks to 5.53 at 16 weeks).

CONCLUSION

The PGA sheet scaffold material allows for tendon insertion regeneration with a fibrocartilage layer but displays mechanical properties inferior to those of the normal tendon in an animal model.

CLINICAL RELEVANCE

The PGA sheet represent a possible alternative scaffold material for tendon regeneration in rotator cuff repair.

Intra-articular partial-thickness rotator cuff tears: analysis of injured and repaired strain behavior

BACKGROUND

There are few biomechanical studies regarding partial-thickness rotator cuff tears and subsequent repair.

HYPOTHESIS

Partial-thickness intra-articular supraspinatus tendon tears increase articular-sided tendon strain as they increase in size. Repair of these tears will return strain to the intact state.

STUDY DESIGN

Controlled laboratory study.

METHODS

Twenty fresh-frozen human cadaveric shoulders were prepared by dissecting to the supraspinatus tendon and leaving the native footprint intact. The tendon footprint was measured with digital calipers and divided into thirds (anterior, middle, and posterior). The middle third was the area where a consistent partial tear was created based on the thickness of the specimens' particular footprint. Created were 25%, 50%, and 75% tears. Image analysis software and differential variable reluctance transducers strain gauges were used to measure strain. A 100 N load at 1 Hz for 30 cycles was conducted for glenohumeral angles of 45 degrees, 60 degrees, and 90 degrees. This was completed for the intact tendon, 25%, 50%, and 75% tears. Shoulders were then repaired using the in situ fixation method. The in situ method consisted of either a parachute anchor or metal corkscrew anchor. Eight shoulders were examined for load-to-failure testing with the Materials Testing System.

RESULTS

There was a significant difference (P < .05) in rotator cuff strain between the intact rotator cuff tendon and 50% and 75% partial-thickness tears. The cuff strain was returned to the intact state with repair. This was consistent for 3 different glenohumeral abduction angles and for all 3 intra-articular tendon areas. The bursal strain did not have any significant differences between groups.

CONCLUSION

Articular-sided tendon strain increases consistently across the supraspinatus tendon with greater partial tears. Repair returned strain close to the intact state.

CLINICAL RELEVANCE

This study may add credence to the clinical practice of repairing intra-articular partial-thickness rotator cuff tears greater than 50%.

Effects of hyaluronan on cell proliferation and mRNA expression of procollagens alpha 1 (I) and alpha 1 (III) in tendon-derived fibroblasts from patients with rotator cuff disease: an in vitro study

BACKGROUND

Hyaluronan (HA) improves postoperative recovery after flexor tendon surgery, preventing postoperative adhesion. However, its influence on the rotator cuff tendon after cuff repair has not yet been clarified in detail.

HYPOTHESIS

Hyaluronan is likely to modulate cell proliferation and mRNA expression of procollagens alpha1 (I) and alpha1 (III) in tendon-derived fibroblasts in patients with rotator cuff disease.

STUDY DESIGN

Controlled laboratory study.

METHODS

The study subjects were 10 patients with rotator cuff disease, with an average age of 62 years (range, 44-72). Various concentrations of HA (1.0-5.0 mg/mL) were added to monolayer-cultured tendon-derived fibroblasts from these patients. Hyaluronan binding and CD44 expression on the tendon-derived fibroblasts were evaluated by confocal microscopy using fluorescein-conjugated HA and antihuman CD44 antibody (OS/37). Cell proliferation was evaluated by recording changes in cell number. The levels of expression of procollagen alpha1 (I) and alpha1 (III) mRNA were measured by real-time reverse transcriptase polymerase chain reaction.

RESULTS

Immunofluorescence cytochemistry detected constitutive binding of HA and CD44 expression on the tendon-derived cells. Treatment with various concentrations of HA significantly inhibited cell proliferation and decreased the expression level of procollagen alpha1 (III) mRNA, but not that of procollagen alpha1 (I) mRNA, in the tendon-derived fibroblasts.

CONCLUSION

Hyaluronan modulates cell proliferation and the expression level of procollagen alpha1 (III) mRNA, but not that of pro-collagen alpha1 (I), in fibroblasts from patients with rotator cuff disease.

CLINICAL RELEVANCE

Postoperative use of exogenous HA may allow the healing of a repaired rotator cuff tendon with minimal adhesion.

Molecular effects of sodium hyaluronate on the healing of avian supracoracoid tendon tear: according to in situ hybridization and real-time polymerase chain reaction

Hyluronic acid (HA) on tissue healing has been controversial. We examined the molecular pharmacology of HA injection at the suture site in an acute model of supracoracoid tendon laceration using chickens, an injury of a nonweight-bearing joint considered similar to the human shoulder. Expression of mRNAs encoding alpha I (I) and alphaI (III) procollagens was localized using in situ hybridization (ISH). Intensities of mRNA expression for alpha I (I) and alpha I (III) procollagens, transforming growth factor-beta1 (TGF- beta1), basic fibroblast growth factor (bFGF), and insulin-like growth factor (IGF) were determined by quantitative reverse transcription-polymerase chain reaction (RT-PCR). Histologically, chickens with HA injection (HA group) showed early restoration of continuity at the laceration site than saline-injection controls (saline-injection group). By ISH, the expression rate of cells at the lesion site that contained alpha I (I) and alpha I (III) procollagen mRNAs were somewhat higher in the HA group than in the saline-injection group. By RT-PCR, the HA- and saline-injection groups showed no significant difference in expression of alpha I (I) and alpha I (III) procollagen mRNA between weeks 1 and 6. The saline -injection group exhibited significant decrease in TGF-beta1 expression between weeks 1 and 3, and in bFGF expression between weeks 1 and 2; however, the HA group showed no such decrease. As for IGF, no difference was appreciable in both groups between weeks 1 and 6. A single injection of HA could cause earlier restoration of continuity at the lacerated site of the supracoracoid tendon.

Assessment of the canine model of rotator cuff injury and repair

Animal shoulder models are used to systematically investigate the factors influencing rotator cuff injury and repair. Each model has advantages and disadvantages that must be considered in the context of the specific research questions being asked. This study evaluated the utility of the canine model for studies of acute, full-thickness rotator cuff tendon injury and repair. We found that time-zero failure load is dependent on the suture type and configuration used for repair. Acute, full-width tendon repairs fail anatomically within the first days after surgery in the canine model, regardless of suture type, suture configuration, or postoperative protocol. Robust scar tissue forms in the gap between the failed tendon end and the humerus, which can be visually, mechanically, and histologically misconstrued as tendon if an objective test of repair connectivity is not performed. We conclude that a full-width injury and repair model in the canine will provide a rigorous test of whether a new repair strategy or postoperative protocol, such as casting or temporary muscle paralysis, can maintain repair integrity in a high-load environment. Alternatively, a partial-width tendon injury model allows loads to be shared between the tendon repair and the remaining intact portion of the infraspinatus tendon and prohibits complete tendon retraction. Thus a partial-width injury in the canine may model the mechanical environment of many single tendon tears in the human injury condition and warrants further investigation.

Partial-thickness rotator cuff tears

Partial-thickness rotator cuff tears are not a single entity; rather, they represent a spectrum of disease states. Although often asymptomatic, they can be significantly disabling. Overhead throwing athletes with partial-thickness rotator cuff tears differ with respect to etiology, goals, and treatment from older, nonathlete patients with degenerative tears. Pathogenesis of degenerative partial-thickness tears is multifactorial, with evidence of intrinsic and extrinsic factors playing key roles. Diagnosis of partial-thickness rotator cuff tears should be based on the patient's symptoms together with magnetic resonance imaging studies. Conservative treatment is successful in most patients. Surgery generally is considered for patients with symptoms of sufficient duration and intensity. The role of acromioplasty has not been clearly delineated, but it should be considered when there is evidence of extrinsic causation for the partial-thickness rotator cuff tear.

Changes in rotator cuff muscle volume, fat content, and passive mechanics after chronic detachment in a canine model

BACKGROUND

Long-standing tears of the rotator cuff can lead to substantial and perhaps irreversible changes in the affected rotator cuff muscles. We developed a chronic rotator cuff tear in a canine model to investigate and quantify the time-related changes in passive mechanics, volume, and fat of the infraspinatus muscle. We hypothesized that infraspinatus muscle stiffness would increase, volume would decrease, and fat content would increase at twelve weeks following tendon detachment.

METHODS

The right infraspinatus tendon of eight adult mongrel dogs were surgically detached from the proximal part of the humerus. The uninvolved left shoulder served as a control. Muscle volume changes were quantified with use of magnetic resonance imaging. At twelve weeks, the passive mechanical properties of the chronically detached and control muscles were determined intraoperatively with use of a custom-designed device. Intramuscular fat was evaluated histologically at the time that the animals were killed.

RESULTS

After twelve weeks of detachment, the stiffness was significantly increased in the detached infraspinatus muscles relative to that in the controls (p < 0.0001). Magnetic resonance image analysis demonstrated that the detached muscle volumes decreased by an average of 32% in the first six weeks and remained constant thereafter. Intramuscular fat increased significantly in the detached muscles and to a greater extent in the lateral regions (p < 0.05).

CONCLUSIONS

The chronically detached muscle is not merely a smaller version of the original muscle but, rather, a different muscle. The detached muscle becomes stiffer, and the passive loads required to repair it can become excessive. A significant reduction in muscle volume occurs within days to weeks following tendon detachment (p < 0.0001). The nonuniformity of changes in muscle fat suggests that fat content should be used cautiously as an indicator of muscle quality.

Partial-thickness rotator cuff tears

Partial-thickness tears of the rotator cuff have been diagnosed with increased frequency because of a heightened awareness of the condition by clinicians and improved diagnostic methods. Research into the causes, natural history, and optimal treatment of this condition lags behind that of full-thickness tears. However, despite the limitations in the existing literature, there has emerged a consensus among shoulder experts that partial-thickness rotator cuff tears should be aggressively treated in the active athlete because of the unfavorable natural history of these lesions and success of accepted surgical algorithms. This review will provide an overview of the theories regarding the origins of partial-thickness rotator cuff tears, discuss the relative accuracy of accepted diagnostic techniques, and summarize the indications and methods of operative repair with an emphasis on the results of various treatment approaches.

Matrix molecule mRNA levels in the bursa and rotator cuff of patients with full-thickness rotator cuff tears

PURPOSE

The purpose of this study was to evaluate at the mRNA level a subset of extracellular matrix molecules relevant during healing and remodeling of rotator cuff tears.

TYPE OF STUDY

Controlled laboratory study.

METHODS

Bursal and rotator cuff tissue from the margin of the rotator cuff tear were harvested from 10 patients (mean age, 57.5 +/- 7.3 years) undergoing surgical repair of full-thickness rotator cuff tears. There were six male and four female patients with a mean duration of symptoms of 14.6 months (range, 2 to 60 months). The mean tear size was 4.4 cm. In addition, tissue was obtained from 6 cadaveric specimens with no gross evidence of rotator cuff tearing. Reverse transcription polymerase chain reaction (RT-PCR) was performed for type I, II, and III collagen, biglycan, decorin, and aggrecan, and normalized to the housekeeping gene GAPDH.

RESULTS

RT-PCR showed that both the bursa and rotator cuff margin had increased mRNA levels for type I and type III collagen in patients with full-thickness rotator cuff tears when compared with normal cadaveric controls. In addition, there was a significant decrease in decorin mRNA levels and an increase in aggrecan mRNA levels in the rotator cuff margin of torn rotator cuff tendons when compared with normal cadaveric controls.

CONCLUSIONS

These results suggest that both the bursa and rotator cuff margin of patients with rotator cuff tears are actively remodeling after injury and that both tissues may potentially contribute to the healing process following repair.

CLINICAL RELEVANCE

These findings may help clinicians determine what aspects of the repair process can be manipulated to affect optimal ruptured tendon repair.

Supraspinatus tendon composition remains altered long after tendon detachment

Most rotator cuff surgery is performed on chronic tears, but changes in the composition of chronically torn tendons remain poorly understood. In this study we surgically created supraspinatus tears in the rat and analyzed the composition of the tendon over time using immunohistochemistry. We found that collagen types I and XII were greatly increased initially after injury and then decreased with time. Collagen type III was detected and persisted in the scar for months. Decorin and biglycan were increased initially and then decreased, although decorin remained elevated from normal for months after injury. Aggrecan and collagen type II were detected in small amounts after detachment, which was associated with the expression of sulfated glycosaminoglycans. These alterations were similar to those seen in human studies. As the quality of the tendon is an important factor in repair, these findings may partially explain why chronic tears heal differently than acute tears.

Supraspinatus tendon organizational and mechanical properties in a chronic rotator cuff tear animal model

Rotator cuff tears of the shoulder are a common cause of pain and disability. The successful repair of rotator cuff tendon tears depends on the time from onset of injury to the time of surgical repair. However, the effect of time from injury to repair remains poorly understood. A rat model was used to investigate the supraspinatus tendon organizational and mechanical property changes that occur with time post-injury to understand the natural injury response in the absence of repair. It was hypothesized that increased time post-injury would result in increased detrimental changes to tendon organizational and mechanical properties. Tendons were detached at the insertion on the humerus without repair and the quantitative organizational and mechanical properties were analyzed at 1, 2, 4, 8, and 16 weeks post-detachment. Tendon detachment resulted in a dramatic decrease in mechanical properties initially followed by a progressive increase with time. The quantitative collagen fiber orientation results provided corroborating support to the mechanical property data. Based on similarities in histology and mechanical properties to rotator cuff tears in humans, the animal model presented here is promising for future investigations of the tendon's natural injury response in the absence of repair.

Comparison of surgical outcome between bursal and articular partial thickness rotator cuff tears

Surgical outcomes after arthroscopic subacromial decompression and debridement in bursal and articular partial thickness rotator cuff tears with a tear depth of < 50% were compared. Twenty-four articular and 13 bursal partial thickness rotator cuff tears were evaluated for pain relief and functional recovery. At 6 months postoperatively, the average pain score decreased from 6.2 to 1.7 in patients with articular tears and from 7.1 to 0.9 in patients with bursal tears. Although pain relief and functional recovery were excellent in both groups, the results were better in patients with bursal partial thickness rotator cuff tears at 6 months postoperatively.

Muscle cell-mediated gene delivery to the rotator cuff

Rotator cuff lesions are one of the most common causes of upper extremity disability. Surgical therapy addresses mostly the extrinsic etiology, but not intrinsic factors such as aging, structural changes, low vascularity, and inflammatory processes. In this study, genetically engineered, highly purified muscle-derived cells (MDCs) were characterized and injected into the supraspinatus tendons of nude rats. The injected cells were monitored for 3 weeks. In vitro, the engineered, highly purified MDCs do not express vimentin; 98% of them are positive for the beta-galactosidase marker gene, and 99% hybridize with the specific pancentromeric mouse probe. beta-Galactosidase marker gene expression of the injected cells was detected up to 21 days. From day 7 after injection, the cell nuclei became spindle shaped, cells were integrated into the tendon collagen bundles, and the cells showed differentiation into vimentin-expressing fibroblastic cells. The results indicate that the rotator cuff tendon matrix and its original cellular components modulated the injected MDCs toward a fibroblastic phenotype. The compatibility and ability of MDCs to differentiate into other cell lineages, such as fibroblasts, might have high potential utility in tissue-engineering applications for tendon healing. This approach facilitates the application of muscle-derived progenitor cells and ex vivo gene therapy for the treatment of rotator cuff lesions.

MRI-negative rotator cuff tears

We report two cases of rotator cuff tear in which the T(2)-weighted MRI signal was negative at the first examination, but positive by the second examination without any changes in symptoms. Many authors have reported on correlations between the MRI and operative findings of rotator cuff tears. However, MRI findings, history of symptoms and operative findings in our patients suggest that there was a discrepancy between symptoms and MRI findings dependent on the period from the injury. Operative findings also indicate that intratendinous tears might have occurred first in these patients then progressed to partial or full thickness tears over time. We concluded that physicians should keep rotator cuff pathology in mind even in patients whose MRI findings are negative but symptoms of rotator cuff tear persist.

Healing of full-thickness tears of avian supracoracoid tendons: in situ hybridization of alpha1(I) and alpha1(III) procollagen mRNA

Although clinically significant, much remains unknown about the healing of the torn rotator cuff tendon, because of unavailability of appropriate animal model. The human supraspinatus tendon faces the subacromial bursa superiorly, and the joint capsule inferiorly, while the digital flexor tendon is surrounded by the synovium. We hypothesized that the supraspinatus tendon heals by the process which is different from that observed with digital flexor tendons, in which epitenon cells migrate into the torn portion circumferentially. The avian supracoracoid tendon was adopted for this experiment because of its similarity to the human supraspinatus tendon. We developed a full-thickness tendon laceration followed by primary suture. The objective of this study was to detect localization of the responsible cells for repair of the tendon. We examined the process using histology and in situ hybridization. Starting at week 1 the peritendon cells of the bursal side proliferated and migrated into the laceration site. At week 6, the tendon stumps were continuous with new connective tissue. High-level expression of procollagen mRNA in the proliferating peritendon cells on the bursal side demonstrates to contribute to the reparative process, which progressed to the joint side. This mode of repair is different from that of the digital flexor tendon.

Vascular endothelial growth factor (VEGF) expression in the subacromial bursa is increased in patients with impingement syndrome

Vascular endothelial growth factor (VEGF), which is known to be an angiogenetic factor, plays an important role in the inflammation of synovial tissue. To investigate the relationships between VEGF and clinical symptoms in rotator cuff disease, VEGF expression was examined using RT-PCR and immunohistochemical analysis in 50 patients with this disease (26 with full-thickness cuff tear, 12 with partial-thickness tear, and 12 with subacromial bursitis). VEGF mRNA expression was detected in 40 out of 50 patients by RT-PCR. VEGF mRNA expression was found more frequently in the patients with motion pain (39 out of 41) than in those without motion pain (1 out of 9) with statistical significance (Fisher's test, P < 0.001). Thirty-one out of 33 patients with synovial proliferation showed VEGF mRNA expression, whereas the expression of this transcript was found in 9 out of 17 patients without synovial proliferation. This association with synovial proliferation was also significant (Fisher's test, P = 0.0013). Thirty out of 41 patients with motion pain had synovial proliferation but 3 out of 9 patients without motion pain had synovial proliferation. In all these 30 patients with both motion pain and synovial proliferation, VEGF mRNA expression was detected. This association between motion pain and synovial proliferation was also significant (Fisher's test, P < 0.05). The mean vessel count and area in subacromial bursa expressing VEGF was significantly higher than in those without VEGF (Mann Whitney's U test, P < 0.01). These results suggested that VEGF expression is associated with vascularity, synovial proliferation and shoulder motion pain in the rotator cuff disease.