Biceps detachment decreases joint damage in a rotator cuff tear rat model

A biomechanical study on the effect of long head of biceps tenotomy on supraspinatus load and humeral head position during shoulder abduction

INTRODUCTION

The purpose of this study was to determine the effect of biceps tendon tenotomy on the load of the supraspinatus tendon/muscle complex during abduction of the arm from 0° to 15°.

METHODS

Eleven fresh frozen human cadaver shoulders (6 males, 5 females, age ranged 44-88 years, mean upper extremity weight 2.96 ± 0.56 kg) were included. The specimens were sequentially mounted onto a custom-made fixture attached to a pulley system and load cell. The pulley system was used to pull the supraspinatus tendon/muscle complex along its fiber directions to abduct the arm to 15°. Abduction angles were recorded with a digital inclinometer. Two conditions were tested: (1) long head biceps tendon (LHBT) intact and in normal anatomical position; (2) LHBT cut within the bicipital groove. Qualitative visual inspection of humeral head displacement during abduction was also included. Descriptive statistics were calculated. The Shapiro-Wilk test was used to establish normal data distribution, and the paired t-test was used to compare the 2 conditions.

RESULTS

For the intact condition (LHBT intact), the mean load was 45.71 ± 21.04 N. For the biceps tenotomy test, the load measured 41.37 ± 23.43 N. These differences were not significant (P = .1480). In the tenotomy condition, the humeral head initially displaced inferior, and with initiation of abduction, the humeral head translated superior to its normal position.

CONCLUSION

The results suggest that the LHBT has no critical role with initial abduction of the arm. Furthermore, the LHBT does not appear to increase loads required for the supraspinatus muscle/tendon complex to perform the same action of abduction.

Arthroscopic Tenotomy of the Long Head of the Biceps Tendon and Section of the Anterior Joint Capsule Produce Moderate Osteoarthritic Changes in an Experimental Sheep Model

Osteoarthritis (OA) of the glenohumeral (GH) joint is a common cause of shoulder pain, resulting in considerable invalidity. Unfortunately, the study of its pathogenesis is challenging. Models of OA are necessary to identify specific targets for therapy and to be able to interfere with the development and evolution of OA. This study aims to assess the effect of an arthroscopic tenotomy of the long head of the biceps tendon (LHBT) and section of the anterior glenohumeral joint capsule on the ovine glenohumeral joint. In addition, the authors aim to validate and evaluate the reliability of a modified semi-quantitative MRI score to assess joint degeneration in a sheep’s shoulder. Eight skeletally mature sheep received an arthroscopic tenotomy of the LHBT and section of the anterior joint capsule and were euthanized four months after surgery. All animals tolerated the surgery well, and no complication was recorded for six weeks. Moderate degenerative changes to the ovine shoulder joint were found on MRI and histological evaluation. The arthroscopic tenotomy of the LHBT and the anterior glenohumeral joint capsule section caused moderate degenerative changes to the ovine shoulder joint.

Lose-Dose Administration of Dexamethasone Is Beneficial in Preventing Secondary Tendon Damage in a Stress-Deprived Joint Injury Explant Model

Secondary joint damage is the process by which a single injury can lead to detrimental changes in adjacent tissue structures, typically through the spread of inflammatory responses. We recently developed an in vitro model of secondary joint damage using a murine rotator cuff explant system, in which injuries to muscle and bone cause massive cell death in otherwise uninjured tendon. The purpose of the present study was to test the ability cytokine-targeted and broad-spectrum therapeutics to prevent cell death and tissue degeneration associated with secondary joint damage. We treated injured bone-tendon-muscle explants with either interleukin-1 receptor antagonist, etanercept, or dexamethasone (DEX) for up to 7 days in culture. Only the low-dose DEX treatment was able to prevent cell death and tissue degeneration. We then identified a critical window between 24 and 72 h following injury for maximal benefit of DEX treatment through timed administration experiments. Finally, we performed two tendon-only explant studies to identify mechanistic effects on tendon health. Interestingly, DEX did not prevent cell death and degeneration in a model of cytokine-induced damage, suggesting other targets of DEX activity. Future studies will aim to identify factors in joint inflammation that may be targeted by DEX treatment, as well as to investigate novel delivery strategies. Statement of clinical significance: Overall, this work demonstrates beneficial effects of DEX administration on preventing tenocyte death and extracellular matrix degeneration in an explant model of secondary joint damage, supporting the clinical use of low-dose glucocorticoids for short-term treatment of joint inflammation. © 2019 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 38:139-149, 2020.

Allogenic Tendon-Autologous Cartilage Cells Transplantation Enhances Adhesive/Growth Ability and Promotes Chondrogenesis in a Rabbit Model of Glenoid Labrum Damage

Background

Glenoid labrum injury of the shoulder commonly occurs in athletes, especially those who perform throwing motions. This study investigated the effects of the established allogenic tendon-autologous cartilage cells reconstruction approach in a rabbit model of glenoid labrum damage.

Material/Methods

The allogenic tendons were isolated and extracted using the chemical extraction method. Cartilage cells were isolated from New Zealand rabbits and identified by detecting type II collagenase. The allogenic tendon-autologous cartilage cells were transplanted to the damaged glenoid labrum. HE staining was used to observe inflammatory cells, Masson staining was used to observe muscle fibers, and scanning electron microscopy (SEM) was used to assess antigenicity of tendon tissues. PSA and AB staining were used to examine neutral protein mucopolysaccharide and acidic protein mucopolysaccharide, respectively. We assessed cartilage cell growth in autologous cartilage cells combined with allogenic tendon transplanted tissues.

Results

Allogenic tendons were well prepared using chemical extraction method due to use of HE staining, Masson staining, and SEM. TGF-β1 treatment induced cartilage cell formation and triggered expression of acidic and neutral protein mucopolysaccharides. HE staining, Masson staining, PAS staining, and AB staining methods showed that autologous cartilage cells combined with allogenic tendon transplanted tissues had better growth of cartilage cells.

Conclusions

This study establishes the allogenic tendon-autologous cartilage cells reconstruction and transplantation approach and illustrated higher adhesive ability and growth ability, and better chondrogenesis in a rabbit model of glenoid labrum damage.

Does bicep pathology affect rotator cuff repair outcomes?

INTRODUCTION

Rotator cuff (RC) tears are common and a frequent cause of dysfunction in the shoulder, especially with progression of age. Biceps pathology occurs concomitantly and its relationship with RC tears has been well described. However, the study of biceps intervention affecting outcomes of RC repair is limited. We aim to study the effect of biceps tenotomy in RC repair after matching for cuff tear size.

METHODS

We collected data of 24 consecutive patients undergoing RC repair and biceps tenotomy and matched them with patients undergoing RC repair only ( n = 24). The groups were matched for age, RC tear size, and presence of subscapularis tears. All patients of this study underwent RC repair under a single surgeon. Patient demographics and outcome measures in the form of range of motion (ROM) pain scores and validated shoulder scores (Constant shoulder score, Oxford score, and University of California Los Angeles shoulder score) were collected preoperative and at predetermined fixed intervals up to 2 years postoperatively. We then compared the two groups using a mixed analysis of variance design so as to identify any possible differences.

RESULTS

Patients from both groups demonstrated significant improvement in ROM, lower pain scores, and improvement in functional outcomes ( p < 0.05). Patients with biceps intervention demonstrated equivalent outcomes postoperatively up to 2 years with no statistical differences ( p > 0.05).

CONCLUSION

Arthoscopic RC repair is an effective intervention for improving ROM, reducing pain, and improving function. Concomitant biceps procedure did not negatively impede recovery or affect outcomes.

Biceps Detachment Preserves Joint Function in a Chronic Massive Rotator Cuff Tear Rat Model

BACKGROUND

Lesions of the long head of the biceps tendon are often associated with massive rotator cuff tears (MRCTs), and biceps tenotomy is frequently performed for pain relief and functional reservation. However, the efficacy and safety of biceps tenotomy regarding the effects on the surrounding tissues in chronic MRCT are unclear.

HYPOTHESIS

Biceps tenotomy would result in improved mechanical and histological properties of the intact subscapularis tendon and improved in vivo shoulder function while not compromising glenoid cartilage properties.

STUDY DESIGN

Controlled laboratory study.

METHODS

Right supraspinatus and infraspinatus tendons were detached in 25 male Sprague-Dawley rats, followed by 4 weeks of cage activity to create a chronic MRCT condition. Animals were randomly divided into 2 groups and received either biceps tenotomy (n = 11) or sham surgery (n = 14) and were sacrificed 4 weeks thereafter. Forelimb gait and ground-reaction forces were recorded 1 day before the tendon detachment (baseline), 1 day before the surgical intervention (biceps tenotomy or sham), and 3, 7, 10, 14, 21, and 28 days after the intervention to assess in vivo shoulder joint function. The subscapularis tendon and glenoid cartilage were randomly allocated for mechanical testing or histologic assessment after the sacrifice.

RESULTS

Compared with sham surgery, biceps tenotomy partially restored the in vivo shoulder joint function, with several gait and ground-reaction force parameters returning closer to preinjury baseline values at 4 weeks. With biceps tenotomy, mechanical properties of the subscapularis tendons were improved, while mechanical properties and histological Mankin scores of the glenoid cartilage were not diminished when compared with the sham group.

CONCLUSION

Biceps tenotomy in the presence of chronic MRCT partially preserves overall shoulder function and potentially restores subscapularis tendon health without causing detrimental effects to joint cartilage. This laboratory study adds to the growing literature regarding the protective effects of biceps tenotomy on the shoulder joint in a chronic MRCT model.

CLINICAL RELEVANCE

This study provides important basic science evidence supporting the use of biceps tenotomy in patients with massive rotator cuff tears.

Primary and Secondary Consequences of Rotator Cuff Injury on Joint Stabilizing Tissues in the Shoulder

Rotator cuff tears (RCTs) are one of the primary causes of shoulder pain and dysfunction in the upper extremity accounting over 4.5 million physician visits per year with 250,000 rotator cuff repairs being performed annually in the U.S. While the tear is often considered an injury to a specific tendon/tendons and consequently treated as such, there are secondary effects of RCTs that may have significant consequences for shoulder function. Specifically, RCTs have been shown to affect the joint cartilage, bone, the ligaments, as well as the remaining intact tendons of the shoulder joint. Injuries associated with the upper extremities account for the largest percent of workplace injuries. Unfortunately, the variable success rate related to RCTs motivates the need for a better understanding of the biomechanical consequences associated with the shoulder injuries. Understanding the timing of the injury and the secondary anatomic consequences that are likely to have occurred are also of great importance in treatment planning because the approach to the treatment algorithm is influenced by the functional and anatomic state of the rotator cuff and the shoulder complex in general. In this review, we summarized the contribution of RCTs to joint stability in terms of both primary (injured tendon) and secondary (remaining tissues) consequences including anatomic changes in the tissues surrounding the affected tendon/tendons. The mechanical basis of normal shoulder joint function depends on the balance between active muscle forces and passive stabilization from the joint surfaces, capsular ligaments, and labrum. Evaluating the role of all tissues working together as a system for maintaining joint stability during function is important to understand the effects of RCT, specifically in the working population, and may provide insight into root causes of shoulder injury.

Biceps tenotomy in the presence of a supraspinatus tear alters the adjacent intact tendons and glenoid cartilage

A rotator cuff tear is a common injury in athletes and workers who repeatedly perform overhead movements, and it is not uncommon for this demographic to return to activity shortly after treatment. A biceps tenotomy is often performed in the presence of a rotator cuff tear to help reduce pain and improve joint function. However, the effect of this procedure on the surrounding tissues in the glenohumeral joint is unknown. Therefore, the purpose of this study was to investigate the effect of a biceps tenotomy in the presence of a supraspinatus rotator cuff tear followed by overuse activity on ambulatory function and mechanical and histologic properties of the remaining rotator cuff tendons and glenoid cartilage. 46 rats underwent 4weeks of overuse activity to create a tendinopathic condition, then were randomized into two groups: unilateral detachment of the supraspinatus tendon or detachment of the supraspinatus and long head of the biceps tendons. Ambulatory measurements were performed throughout the 8weeks prior to euthanasia, followed by analysis of the properties of the remaining intact tendons and glenoid cartilage. Results demonstrate that shoulder function was not effected in the biceps tenotomy group. However, the intact tendons and glenoid cartilage showed altered mechanical and histologic properties. This study provides evidence from an animal model that does not support the use of tenotomy in the presence of a supraspinatus tendon rotator cuff tear, and provides a framework for physicians to better prescribe long-term treatment strategies for patients.

Effect of overuse-induced tendinopathy on tendon healing in a rat supraspinatus repair model

Supraspinatus tears often result in the setting of chronic tendinopathy. However, the typical repair model utilizes an acute injury. In recognition of that distinction, our laboratory developed an overuse animal model; however it is unclear whether induced overuse is necessary in the repair model. We studied the repair properties of overuse-induced tendons compared to normal tendons. We hypothesized that histological and mechanical properties would not be altered between the overuse-induced and normal tendons 1 and 4 weeks after repair. Thirty-one adult male Sprague-Dawley rats were subjected to either overuse or cage activity for 4 weeks prior to bilateral supraspinatus tendon repair surgery. Rats were sacrificed at 1 and 4 weeks post-surgery and evaluated for histology and mechanics. Results at 1 week showed no clear histologic changes, but increased inflammatory protein expression in overuse tendons. At 4 weeks, percent relaxation was slightly increased in the overuse group. No other alterations in mechanics or histology were observed. Our results suggest that the effects of the surgical injury overshadow the changes evoked by overuse. Because clinically relevant mechanical parameters were not altered in the overuse group, we conclude that when examining tendons 4 weeks after repair in the classic rat supraspinatus model, inducing overuse prior to surgery is likely to be unnecessary.

Ground reaction forces are more sensitive gait measures than temporal parameters in rodents following rotator cuff injury

Gait analysis is a quantitative, non-invasive technique that can be used to investigate functional changes in animal models of musculoskeletal disease. Changes in ground reaction forces following injury have been observed that coincide with differences in tissue mechanical and histological properties during healing. However, measurement of these kinetic gait parameters can be laborious compared to the simpler and less time-consuming analysis of temporal gait parameters alone. We compared the sensitivity of temporal and kinetic gait parameters in detecting functional changes following rotator cuff injury in rats. Although these parameters were strongly correlated, temporal measures were unable to detect greater than 50% of the functional gait differences between injured and uninjured animals identified simultaneously by ground reaction forces. Regression analysis was used to predict ground reaction forces from temporal parameters. This model improved the ability of temporal parameters to identify known functional changes, but only when these differences were large in magnitude (i.e., between injured vs. uninjured animals, but not between different post-operative treatments). The results of this study suggest that ground reaction forces are more sensitive measures of limb/joint function than temporal parameters following rotator cuff injury in rats. Therefore, although gait analysis systems without force plates are typically efficient and easy to use, they may be most appropriate for use when major functional changes are expected.

Rotator cuff biology and biomechanics: a review of normal and pathological conditions

The glenohumeral joint is a complex anatomic structure commonly affected by injury such as tendinopathy and rotator cuff tears. This review presents an up-to-date overview of research on tendon biology and structure, shoulder joint motion and stability, tendon healing, and current and potential future repair strategies. Recent studies have provided information demonstrating the serious impact on uninjured tissues after a rotator cuff tear or other cause of altered shoulder joint mechanics. Another major focus of recent research is biological augmentation of rotator cuff repair with the goal of successfully reinstating normal tendon-to-bone structure. To effectively treat shoulder pathologies, clinicians need to understand normal tendon biology, the healing process and environment, and whole shoulder stability and function.

Effect of isolated hyperglycemia on native mechanical and biologic shoulder joint properties in a rat model

Recently, diabetes has been linked to rotator cuff disease and adhesive capsulitis, conditions with increased stiffness and inflammation. Unfortunately, limited research exists examining how hyperglycemia affects the native shoulder (tendon and capsule) properties. Therefore, the objectives of this study were to compare shoulder joint mechanics, tendon properties (mechanics and immunohistochemistry), and capsule of healthy control and hyperglycemic rats 8 weeks following induction of hyperglycemia with a submaximal dose of streptozotocin (STZ). Eighteen rats were injected with STZ to induce hyperglycemia or citrate buffer (control) and underwent normal cage activity for 8 weeks. Passive joint mechanics demonstrated significantly less external rotation in the hyperglycemic group compared to controls, with no other group differences. Tendon mechanical properties (stiffness and modulus) were not significantly different between groups at both the insertion site and mid-substance. Immunohistochemistry staining of the tendon and capsule demonstrated significantly increased interleukin 1-beta (IL1-β) and advanced glycated end-products (AGE) staining localized to the insertion and mid-substance of the tendon but not the capsule. In addition, tumor necrosis factor alpha (TNF-α) staining was significantly increased in the superior capsule but not the supraspinatus tendon. This study demonstrates that isolated hypergylcemia does not diminish shoulder mechanical properties but does induce a chronic inflammatory response.

Intra-articular tibiofemoral injection of a nonsteroidal anti-inflammatory drug has no detrimental effects on joint mechanics in a rat model

Administration of intra-articular medications, including corticosteroids and analgesics, is common clinical practice for knee pathology and dysfunction. Non-steroidal anti-inflammatory drugs (NSAIDs) are another category of medication commonly prescribed for their analgesic and anti-inflammatory properties. Recent studies demonstrated the efficacy of injectable NSAIDs in the treatment of intra-articular pathology and postoperative analgesia. However, little data exist regarding the safety of intra-articular injection, despite the increase in its application. Therefore, we investigated the effects of intra-articular NSAID injection on articular cartilage, the anterior cruciate ligament (ACL), and joint function in the rat. Sixty-four Sprague-Dawley rats were divided into either saline (SAL) or ketorolac (NSAID) tibiofemoral single injection treatment groups. Animals were euthanized at 2, 7, 28, and 84 days post-injection for histological and mechanical analyses. Additionally, a subset of animals underwent longitudinal ambulatory evaluation to determine joint functional properties. We hypothesized that intra-articular ketorolac injection would result in no detrimental mechanical, histological, or functional changes. No differences were reported between the NSAID and SAL groups in any of the parameters measured at any time point, demonstrating the potential safety of intra-articular NSAID administration. Therefore, NSAID injection could be further considered for clinical application in humans.