Hypercholesterolemia increases supraspinatus tendon stiffness and elastic modulus across multiple species

Hyperlipidemia Induced Pathological Changes with no Effect in Biomechanical Properties in the Achilles Tendon of Young Swine

Hyperlipidemia is linked to atherosclerosis and various diseases. Its strong association with Achilles tendinopathies and xanthomas affects tendon properties through lipid deposition in tendon tissue. We examined the impact of hyperlipidemia on the biomechanical properties of the swine Achilles tendons. Swines were fed a high-cholesterol-high-fat diet to induce hyperlipidemia, and their Achilles tendons were collected and examined for biomechanical properties. The ultimate tensile strength, modulus of elasticity and viscoelastic properties did not exhibit significant differences between hyperlipidemic and control swines. H&E and pentachrome staining revealed extracellular matrix (ECM) disorganization and cellular infiltration in the hyperlipidemic swines, highlighting a marked difference between the control and hyperlipidemic groups. These results suggest hyperlipidemia in young swines alters the tendon composition and may contribute to weak biomechanical properties with time.

Biochemical and morpho-mechanical properties, and structural organization of rat tail tendon collagen in diet-induced obesity model

We have investigated the impact of obesity on the structural organization, morpho-mechanical properties of collagen fibers from rat tail tendon fascicles (RTTFs). Polarized Raman microspectroscopy showed that the collagen bands 855, 875, 938, and 960 cm-1 as well as those 1631 and 1660 cm-1 were affected by diet. Mechanical properties exhibited an increase in the yield strength from control (CTRL) to high fat (HF) diet (9.60 ± 1.71 and 13.09 ± 1.81 MPa) (p < 0.01) and ultimate tensile strength (13.12 ± 2.37 and 18.32 ± 2.83 MPa) (p < 0.05) with no significant change in the Young's Modulus. During mechanical, the band at 875 cm-1 exhibited the most relevant frequency shift (2 cm-1). The intensity of those at 855, 875, and 938 cm-1 in HF collagen displayed a comparable response to mechanical stress as compared to CTRL collagen with no significant diet-related changes in the Full Width at Half Maximum. Second harmonic generation technique revealed i) similar fiber straightness (0.963 ± 0.004 and 0.965 ± 0.003) and ii) significant changes in fibers diameter (1.48 ± 0.07 and 1.52 ± 0.08 μm) (p < 0.05) and length (22.06 ± 2.38 and 29.00 ± 3.76 μm) (p < 0.001) between CTRL and HF diet, respectively. The quantification of advanced glycation end products (AGEs) revealed an increase in both carboxymethyl-lysine and total fluorescence AGEs from CTRL to HF RTTFs.

Current Research on the Influence of Statin Treatment on Rotator Cuff Healing

Rotator cuff tears are a condition characterized by damage to the muscles and tendons that connect the scapula and humerus, which are responsible for shoulder rotation and arm lifting. Metabolic factors such as diabetes, thyroid disease, high cholesterol, vitamin D deficiency, obesity, and smoking have been associated with an increased risk of rotator cuff tears. Interestingly, patients with hyperlipidemia, a condition characterized by high levels of cholesterol and other fats in the blood, have been found to have a higher incidence of rotator cuff tears and breakdown of tendon matrix. As a result, statin therapy, which is commonly used to lower cholesterol levels in hyperlipidemia, has been explored as a potential treatment to improve clinical outcomes in rotator cuff tears. However, the results of preclinical and clinical studies on the effects of statins on tendon healing in rotator cuff tears are limited and not well-defined. Moreover, since hyperlipidemia and rotator cuff tears are more prevalent in older individuals, a literature review on the efficacy and safety of statin therapy in this population is needed.

Repeatability of computed tomography liver radiomic features in a nonhuman primate model of diet-induced steatosis

Purpose

We describe a method to identify repeatable liver computed tomography (CT) radiomic features, suitable for detection of steatosis, in nonhuman primates. Criteria used for feature selection exclude nonrepeatable features and may be useful to improve the performance and robustness of radiomics-based predictive models.

Approach

Six crab-eating macaques were equally assigned to two experimental groups, fed regular chow or an atherogenic diet. High-resolution CT images were acquired over several days for each macaque. First-order and second-order radiomic features were extracted from six regions in the liver parenchyma, either with or without liver-to-spleen intensity normalization from images reconstructed using either a standard (B-filter) or a bone-enhanced (D-filter) kernel. Intrasubject repeatability of each feature was assessed using a paired t -test for all scans and the minimum p -value was identified for each macaque. Repeatable features were defined as having a minimum p -value among all macaques above the significance level after Bonferroni's correction. Features showing a significant difference with respect to diet group were identified using a two-sample t -test.

Results

A list of repeatable features was generated for each type of image. The largest number of repeatable features was achieved from spleen-normalized D-filtered images, which also produced the largest number of second-order radiomic features that were repeatable and different between diet groups.

Conclusions

Repeatability depends on reconstruction kernel and normalization. Features were quantified and ranked based on their repeatability. Features to be excluded for more robust models were identified. Features that were repeatable but different between diet groups were also identified.

Hyperlipidemia Lowers the Biomechanical Properties of Rotator Cuff Tendon

Infraspinatus tendon is the most affected tendon of the rotator cuff, being an important posterior component of the shoulder joint. Hyperlipidemia is a predisposing factor in the progression of rotator cuff tears and retear. We studied the effect of hyperlipidemia on the biomechanical properties of rotator cuff tendons. The infraspinatus tendon of the rotator cuff from hyperlipidemic swine were collected and tested for ultimate tensile strength (UTS) and modulus of elasticity. Dynamic mechanical analysis was performed to examine viscoelastic properties. The findings revealed no significant difference in UTS but had significantly lower modulus of elasticity in the infraspinatus tendon of the hyperlipidemic group compared to the control group. Moreover, differences in the dynamic modulus, storage modulus, and loss modulus were not statistically significant between the hyperlipidemic and control swine. There was no difference in water content between the groups but the hyperlipidemic group had fatty infiltration aiding the initial decrease in mechanical properties. These findings suggest an association between fat deposition and early changes in the biomechanical properties of the tendons in the shoulder rotator cuff in hyperlipidemic state.

Effect of Aging on Tendon Biology, Biomechanics and Implications for Treatment Approaches

Tendon aging is associated with an increasing prevalence of tendon injuries and/or chronic tendon diseases, such as tendinopathy, which affects approximately 25% of the adult population. Aged tendons are often characterized by a reduction in the number and functionality of tendon stem/progenitor cells (TSPCs), fragmented or disorganized collagen bundles, and an increased deposition of glycosaminoglycans (GAGs), leading to pain, inflammation, and impaired mobility. Although the exact pathology is unknown, overuse and microtrauma from aging are thought to be major causative factors. Due to the hypovascular and hypocellular nature of the tendon microenvironment, healing of aged tendons and related injuries is difficult using current pain/inflammation and surgical management techniques. Therefore, there is a need for novel therapies, specifically cellular therapy such as cell rejuvenation, due to the decreased regenerative capacity during aging. To augment the therapeutic strategies for treating tendon-aging-associated diseases and injuries, a comprehensive understanding of tendon aging pathology is needed. This review summarizes age-related tendon changes, including cell behaviors, extracellular matrix (ECM) composition, biomechanical properties and healing capacity. Additionally, the impact of conventional treatments (diet, exercise, and surgery) is discussed, and recent advanced strategies (cell rejuvenation) are highlighted to address aged tendon healing. This review underscores the molecular and cellular linkages between aged tendon biomechanical properties and the healing response, and provides an overview of current and novel strategies for treating aged tendons. Understanding the underlying rationale for future basic and translational studies of tendon aging is crucial to the development of advanced therapeutics for tendon regeneration.

Pathological alterations in the expression status of rotator cuff tendon matrix components in hyperlipidemia

Hyperlipidemia is an important risk factor in the development and progression of tendon pathology, however its role in aggravating rotator cuff tendon injury (RCTI) is largely unknown. We aimed to assess the expression status of key extracellular matrix (ECM) components in the tendon tissues and tenocytes under hyperlipidemia. Shoulder rotator cuff (RC) tendon tissues harvested from the swine model of hyperlipidemia displayed alterations in histomorphometry and the expression status of major ECM component proteins including COL-I, COL-III, COL-IV, COL-V, COL-VI, MMP2, and MMP9. Similarly, the LDL- and oxLDL-challenged tenocytes displayed altered expression of the same proteins at both transcriptional and translational levels. In addition, the lipid uptake and cellular reactive oxygen radicals predominated in the lipid-challenged tenocytes compared to the control. Overall, the LDL-treated cells displayed predominant pathological alterations compared to the ox-LDL-treated cells. Further understanding regarding the underlying molecular mechanisms driving the tendon matrisome alteration and subsequent aggravated RCTI pathology in hyperlipidemia could open novel translational avenues in the management of RCTI.

Rotator Cuff Health, Pathology, and Repair in the Perspective of Hyperlipidemia

Rotator Cuff Injuries (RCI) are prevalent cause of shoulder pain affecting over 20% of the population in the USA. Surgical repair of the torn rotator cuff helps in relieving the pressure on the rotator cuff tendon and from symptoms, however tendon-to-bone healing after rotator cuff surgery still has a high failure rate. Hyperlipidemia has been strongly associated with RCI although the cellular and molecular mechanisms are largely unknown. The focus of this critical review is to further explore the role of hyperlipidemia in RCI and rotator cuff tissue repair to determine its implication as a risk factor for tears, repair, and retears. A literature review was conducted to elucidate the role of hyperlipidemia as an inflammatory mediator and catalyst for structural instability within the shoulder. The results from various studies were critically reviewed to summarize the relationship between hyperlipidemia and rotator cuff pathology. Hyperlipidemia induces LDL-particle entrapment within the dense regular collagen of rotator cuff tendons resulting in foam cell aggregation and macrophage recruitment. Subsequent inflammatory pathways including the JAK2/STAT3 pathway and NLRP3 inflammasome pathway led to persistent inflammation and Extracellular Matrix (ECM) degradation within the rotator cuff. While arthroscopic repair remains the most common treatment modality, nonsurgical treatment including statins, vitamin D, and targeting miRNA are also of therapeutic benefit. Hyperlipidemia interferes with arthroscopic repairs by inducing inflammation and stiffness within tendons and increases the risk of retears. Most notably, targeting underlying mechanisms influencing inflammation has large therapeutic value as a novel treatment strategy for the management of rotator cuff pathology.

A lipid metabolite lipidomics assay for prediction and severity evaluation of rotator cuff injury

Objective

Rotator cuff injury can be caused by local inflammation and fibrosis of musculotendinous cuff. Hypercholesterolemia can lead to physiological changes of rotator cuff that resemble rotator cuff injury. However, the relationship between lipid metabolism and rotator cuff injury and its potential pathological mechanism remain unclear. Herein, we aimed to investigate the correlation between the plasma lipidome, rotator cuff injury, and successive fatty infiltration pathology, and hoped to identify biomarkers for predicting higher risk or higher severity rotator cuff injury by assessing metabolic perturbations and dyslipidemia using lipidomics.

Methods

We quantitatively analyzed 60 lipids species of seven lipids classes and subclasses from 66 subjects using lipidomics. Subjects were divided into four groups: (1) normal rotator cuff with normal clinical routine serum lipid test results (NN group = 13); (2) normal rotator cuff with abnormal clinical routine serum lipid test results (NA group = 10); (3) rotator cuff tear with normal routine serum lipid test results (RN group = 30); (4) rotator cuff tear with abnormal routine serum lipid test results (RA group = 13). Independent-sample t-tests and Kruskal-Wallis tests were used to compare lipid metabolite levels in serum between different groups in patients with rotator cuff tears. The orthogonal partial least squares-discriminant analysis (OPLS-DA) model was used to verify the ability of five lysophosphatidylcholines (LPCs) to distinguish rotator cuff injuries. In the rotator cuff tear group, magnetic resonance imaging (MRI) was used to classify fatty infiltration according to Goutallier's classification. Kruskal-Wallis tests were used to analyze molecular differences between high-grade (grade 3–4) and low-grade (grade 0–2) fatty infiltration groups. Receiver operator characteristic (ROC) curves were drawn for each diagnostic method via different metabolites. The area under the curve (AUC), cutoff, specificity, sensitivity, and accuracy of each diagnostic criterion were calculated.

Results

Our results showed that some rotator cuff injury patients yielded unique lipidomic profiles. Based on Kruskal-Wallis tests, our results showed significant differences in three lipid molecules, 17:1 Lyso PI, 18:0–22:6 PE, and 18:3 (Cis) PC, among all four groups independent of clinical blood lipid levels. Also, independent of clinical blood lipid levels, two lipid molecules, 22:0 Lyso PC and 24:0 Lyso PC, were significantly different between the two groups based on Independent sample t-tests. Kruskal-Wallis test results showed that in the rotator cuff tear group, two metabolites (24:0 SM and 16:0 ceramide) differed between high-grade and low-grade fatty infiltration. The AUC values for 22:0 Lyso PC, 24:0 Lyso PC, 18:0–22:6 PE, 24:0 SM, and 16:0 ceramide were 0.6036, 0.6757, 0.6712, 0.8333, and 0.8981, respectively.

Conclusion

The results provide insight into how the metabolic mechanisms associated with dyslipidemia impact rotator cuff diseases. Five lipid molecules, 17:1 Lyso PI, 18:0–22:6 PE, 18:3 (Cis) PC, 22:0 Lyso PC, and 24:0 Lyso PC, were closely related to rotator cuff tear based on two statistical analysis methods, independent of clinical routine serum lipid test results, which indicates that lipidomics assays are more sensitive than conventional lipid tests, and more suitable for studying rotator cuff lipid metabolism. In addition, two lipid metabolites, 24:0 SM and 16:0 ceramide, are potentially useful for predicting fatty infiltration severity. Further research with a larger number of samples is needed to verify whether these two metabolites can serve as potential markers of severe fatty infiltration. The findings illuminate how metabolic mechanisms associated with dyslipidemia affect rotator cuff disease.

Dyslipidemia is associated with risk for rotator cuff repair failure: a systematic review and meta-analysis

Background

Lipid deposition secondary to dyslipidemia (DLD) is shown to have a significant impact on tendon pathology, including tendon elasticity, fatty infiltration, and healing properties. Rotator cuff repair is a common procedure, susceptible to influence from many tear-related and patient-related characteristics. The purpose of this study was to determine the relationship between DLD and rotator cuff repair outcomes with analysis of retear risk and function.

Methods

PubMed, Embase, and SPORTDiscus were searched for all English-language, peer-reviewed studies between 2000 and the present, which analyzed relationships between patient-related factors and outcomes of rotator cuff repair. Studies that explicitly examined the effect of DLD on rotator cuff repair outcomes were chosen for inclusion. Included studies were assessed for methodological quality, and data were extracted for meta-analysis.

Results

Of the 3087 titles, 424 were screened by abstract, and 67 were reviewed in full. Inclusion criteria were met by 11 studies. Of these studies, 5 studies assessed retear, 2 studies measured function, 3 studies reported both retear and function, and 1 study evaluated the risk of retear necessitating a revision surgery. The studies report no significant difference in functional outcomes. Meta-analysis revealed that DLD patients had a significantly higher risk of retear after primary rotator cuff repair (odds ratio 1.32, 95% confidence interval 1.06-1.64).

Conclusion

DLD leads to an increased risk of retear after rotator cuff repair, although function appears to be unimpaired. DLD should be considered among other risk factors when counseling patients regarding expected rotator cuff repair outcomes.

Is there a relation between plantar fasciitis and total cholesterol levels?

BACKGROUND

The main objective of this study is to investigate the relationship between hypercholesterolemia and Plantar Fasciitis (PF).

METHODS

The study includes patients who presented to the orthopedics outpatient clinic with heel pain and were diagnosed with PF. The control group was composed of patients who came to the orthopedics outpatient clinic, with complaints other than heel pain. The two groups were compared in terms of epidemiological data, total cholesterol (TC) levels, and hypercholesterolemia prevalence. We also performed an in-group analysis of PF patients in terms of age, sex, body mass index, and duration of symptoms.

RESULTS

There were 238 patients (mean age, 46.7) in the PF group and 240 patients (mean age, 47.9) in the control group. There was a significant difference between the PF group and the control group in TC levels (207.6 ± 47.5 versus 195.1 ± 30.1, p = 0.001). Hypercholesterolemia (TC level > 240 mg/dL) was found in 22.7% (n = 54) of the patients in the PF group whereas in the control group this rate was 10.8% (n = 26) (p < 0.001). It was seen that the TC levels were significantly higher in patients over the age of 45 in the PF group (p = 0.038). We also found that TC levels were higher in PF patients with symptoms for longer than a year (p = 0.026).

CONCLUSION

Significantly higher TC levels were found in PF patients in comparison with other orthopedic outpatients. Besides, being over the age of 45 and having a duration of symptoms longer than a year is associated with higher cholesterol levels for PF patients.

LEVEL OF CLINICAL EVIDENCE

4.

Risk factors affecting rotator cuff retear after arthroscopic repair: a meta-analysis and systematic review

BACKGROUND

Retear after arthroscopic rotator cuff repair (ARCR) consistently challenges medical staff and patients, and the incidence of retear after surgery is 10%-94%. The purpose of this study was to identify the risk factors that cause retear after ARCR and provide theoretical guidance for clinical intervention to reduce the occurrence of postoperative rotator cuff retear.

METHODS

The protocol for this meta-analysis was registered with PROSPERO (CRD42021225088). PubMed, Web of Science, and Embase were searched for observational studies on risk factors for rotator cuff retear after arthroscopic repair. Meta-analytical methods were used to determine the odds ratio or weighted mean difference of potential risk factors related to postoperative rotator cuff retear. Stata 15.1 was used to quantitatively evaluate the publication bias of the statistical results.

RESULTS

Fourteen studies from 6 countries with a total of 5693 patients were included. The meta-analysis revealed that the risk factors for retear after rotator cuff repair were age, body mass index, diabetes, subscapularis and infraspinatus fatty infiltration, symptom duration, bone mineral density, tear length, tear width, tear size area, amount of retraction, critical shoulder angle, acromiohumeral interval, distance from the musculotendinous junction to the glenoid, operative duration, biceps procedure, and postoperative University of California Los Angeles shoulder score.

CONCLUSION

These findings can help clinical medical staff identify patients who are prone to retear early after arthroscopic repair and develop targeted prevention and treatment strategies for modifiable risk factors, which are of great significance for reducing the occurrence of rotator cuff retear after ARCR.

The effects of cholesterol accumulation on Achilles tendon biomechanics: A cross-sectional study

Familial hypercholesterolemia, a common genetic metabolic disorder characterized by high cholesterol levels, is involved in the development of atherosclerosis and other preventable diseases. Familial hypercholesterolemia can also cause tendinous abnormalities, such as thickening and xanthoma (tendon lipid accumulation) in the Achilles, which may impede tendon biomechanics. The objective of this study was to investigate the effect of cholesterol accumulation on the biomechanical performance of Achilles tendons, in vivo. 16 participants (10 men, 6 women; 37±6 years) with familial hypercholesterolemia, diagnosed with tendon xanthoma, and 16 controls (10 men, 6 women; 36±7 years) underwent Achilles biomechanical assessment. Achilles biomechanical data was obtained during preferred pace, shod, walking by analysis of lower limb kinematics and kinetics utilizing 3D motion capture and an instrumented treadmill. Gastrocnemius medialis muscle-tendon junction displacement was imaged using ultrasonography. Achilles stiffness, hysteresis, strain and force were calculated from displacement-force data acquired during loading cycles, and tested for statistical differences using one-way ANOVA. Statistical parametric mapping was used to examine group differences in temporal data. Participants with familial hypercholesterolemia displayed lower Achilles stiffness compared to the control group (familial hypercholesterolemia group: 87±20 N/mm; controls: 111±18 N/mm; p = 0.001), which appeared to be linked to Achilles loading rate rather than an increased strain (FH: 5.27±1.2%; controls: 4.95±0.9%; p = 0.413). We found different Achilles loading patterns in the familial hypercholesterolemia group, which were traced to differences in the centre of pressure progression that affected ankle moment. This finding may indicate that individuals with familial hypercholesterolemia use different Achilles loading strategies. Participants with familial hypercholesterolemia also demonstrated significantly greater Achilles hysteresis than the control group (familial hypercholesterolemia: 57.5±7.3%; controls: 43.8±10%; p<0.001), suggesting that walking may require a greater metabolic cost. Our results indicate that cholesterol accumulation could contribute to reduced Achilles function, while potentially increasing the chance of injury.

Rotator Cuff Healing

The present article broadly addresses the aspects that interfere with the healing process of the rotator cuff. Life habits, such as smoking and alcoholism, are considered, systemic factors such as diabetes mellitus, hypertension, and obesity, as well as local factors, among which are those related to the pre, peri, and postoperative periods. From an extensive literature review, with the citation of 60 scientific articles from both Western and Eastern literature, the authors intend to deepen the theme by bringing to medical practice conducts based on new established concepts.

The Effect of Patient Characteristics and Comorbidities on the Rate of Revision Rotator Cuff Repair

PURPOSE

To describe the national rates of failed primary rotator cuff repair (RCR) requiring revision repair, using numerous patient characteristics previously defined in orthopaedic literature, including smoking history, diabetes mellitus (DM), hyperlipidemia (HLD), vitamin D deficiency, and osteoporosis to determine which factors independently affect the success of primary RCR.

METHODS

A combined public and private national insurance database was searched from 2007 to 2016 for all patients who underwent RCR. Current Procedural Terminology codes were used to identify RCRs. Laterality modifiers for the primary surgery were used to identify subsequent revision RCRs. All patients who did not have a linked laterality modifier for the RCR Current Procedural Terminology code were excluded from the study. Basic demographics were recorded. International Classification of Diseases Ninth Revision codes were used to identify patient characteristics including Charlson Comorbidity Index, smoking status, DM, obesity, HLD, vitamin D deficiency, and osteoporosis. Patient age categorized as <60, 60-69, 70-74, or 75+ years old. Dichotomous data were analyzed with χ² testing. Multivariable logistic regression was used to characterize independent associations with revision RCR.

RESULTS

Included in the study were 41,467 patients (41,844 shoulders, 52.7% male patients) who underwent primary arthroscopic RCR. Of all arthroscopic RCRs, 3072 patients (3463 shoulders, 53.5% male patients) underwent revision RCR (8.38%). In both primary and revision RCR, patients age 60 to 69 years were most prevalent, accounting for 38.4% and 37.6% of the cohorts, respectively. The average time from primary RCR to revision was 414.9 days (median 214.0 days). Increasing age and male sex (odds ratio [OR] 1.10, P = .019, 95% confidence interval [CI] 1.02-1.19) were significantly predictive of revision RCR. Of the remaining patient characteristics, smoking most strongly predicted revision RCR (OR 1.36, P < .001, CI 1.23-1.49). Obesity (OR 1.32, P < .001, CI 1.21-1.43), hyperlipidemia (OR 1.09, P = .032, CI 1.01-1.18), and vitamin D deficiency (OR 1.18, P < .001, CI 1.08-1.28) also increased risk of revision RCR significantly. DM was found to be protective against revision surgery (OR 0.84, P < .001, CI 0.76-0.92). Overall comorbidity burden as measured by the Charlson Comorbidity Index was not predictive of revision RCR.

CONCLUSIONS

Smoking, obesity, vitamin D deficiency, and HLD are shown to be independent risk factors for failure of primary RCR requiring revision RCR. However, despite the suggestions of previous studies, DM, osteoporosis, and overall comorbidity burden did not demonstrate independent associations in this study.

LEVEL OF EVIDENCE

IV, Case Series.

Factors Related to Symptomatic Failed Rotator Cuff Repair Leading to Revision Surgeries After Primary Arthroscopic Surgery

PURPOSE

To evaluate the clinical characteristics of patients with symptomatic failed rotator cuff repair who required revision surgeries and to identify clinical and radiologic factors related to the need for revision surgery.

METHODS

Ninety-eight patients who were diagnosed with rotator cuff retear within 2 years after primary arthroscopic surgery were included. Patients were divided into 2 groups: patients who underwent revision surgery within 2 years postoperatively (44 patients, group I) and patients who did not require additional treatment due to minimal discomfort during the same period (54 patients, group II). Demographic and radiographic factors related to cuff healing were analyzed. Univariate and multivariate analyses were performed to evaluate factors related to revision surgery.

RESULTS

Group I showed significantly inferior clinical outcomes at the time of revision compared to group II (American Shoulder and Elbow Surgeons score; 54.0 ± 12.1 vs 86.5 ± 12.2, Constant score; 65.2 ± 10.8 vs 84.0 ± 11.4, P < .001). Total cholesterol level (210.2 ± 40.0 vs 189.7 ± 39.1, P = .012), low-density lipoprotein level (130.7 ± 28.7 vs 115.5 ± 26.9, P = .008), and fatty infiltration of the infraspinatus (20.5% vs 3.7%, P = .011) were significantly greater in group I than in group II. On postoperative magnetic resonance imaging, retear of the infraspinatus tendon occurred significantly more frequently in group I (81.8%) than in group II (37.0%, P < .001). In group I, relative changes in anteroposterior (AP) (19.2 ± 37.8) and mediolateral retear size (29.6 ± 90.7) were significantly greater than in group II (AP; -39.5 ± 19.2, mediolateral; -29.2 ± 26.8, P < .001). Relative change in AP retear size was the most powerful independent predictor of symptomatic failed rotator cuff repair (odds ratio 1.19, confidence interval 1.08-1.31, P < .001).

CONCLUSIONS

Preoperative serum total cholesterol level, low-density lipoprotein levels, and fatty infiltration of the infraspinatus were significantly related to symptomatic failed rotator cuff repair. Relative change in AP retear size was the most powerful independent predictor of symptomatic failed rotator cuff repair.

LEVEL OF EVIDENCE

Level III, Case-control study.

Role of shear wave elastography in the evaluation of the treatment and prognosis of supraspinatus tendinitis

BACKGROUND

Supraspinatus tendinitis recurs easily after treatment. One of the main reasons is the lack of objective tools for the efficacy evaluation. Shear wave elastography (SWE) can quantitatively analyze the tissue elasticity of region of interest by measuring the Young’s modulus (YM) value.

AIM

To explore the role of SWE in the efficacy and prognostic evaluation of supraspinatus tendinitis.

METHODS

Eighty-seven patients with supraspinatus tendinitis treated in Jiading District Central Hospital Affiliated Shanghai University of Medicine and Health Sciences were recruited. Another 30 healthy volunteers were enrolled as the control group. The visual analogue scale (VAS) and Constant-Murley Score (CMS) were recorded before treatment. All participants were scanned by SWE scan, and the YM value of the region of interest were recorded. Spearman correlation analysis was performed on YM values with VAS and CMS. Univariate repeated measures analysis of variance was used to calculate the changing trend of VAS, CMS and SWE under different treatment courses. After treatment, the patients were further grouped based on who achieved significantly effective and curative treatment. The patients in the continued treatment group continued to receive treatment according to the YM value, and the remaining patients who stopped receiving treatment were included in the stopped treatment group. All patients were followed up for 1 year, and the difference in recurrence rates between the continued treatment group and the stopped treatment group were compared.

RESULTS

The SWE images of supraspinatus muscle in healthy volunteers were mainly blue, while those of patients with supraspinatus tendinitis showed regional red and green areas. The average YM value of the supraspinatus muscle in healthy volunteers was 26.12 ± 4.03 kPa. The average YM value of patients with supraspinatus muscle was greater than that of healthy volunteers (average YM = 60.61 ± 11.53 kPa, t = 26.344, P < 0.001). The YM value was positively correlated with VAS (r = 0.564, P < 0.001) and negatively correlated with CMS (r = -0.411, P < 0.001). The changes of VAS and CMS were the most obvious in course 1 and then decreased gradually. The degree of change in YM values was similar in different courses. After a 1-year follow-up, the cumulative relapse-free rate in the continued treatment group was 91.43%, which was significantly higher than that in the stopped treatment group (64.71%, X² = 7.379, P = 0.007).

CONCLUSION

SWE can objectively indicate the severity of supraspinatus tendinitis. Using the YM value as a criterion for curative effect may reduce the recurrence rate.

Analysis of mechanical properties of bones and tendons shows that modern hybrid rye can be introduced to corn-wheat based diet in broiler chickens as an alternative energy source irrespective of xylanase supplementation

This study focused on analyzing the effects of inclusion of modern hybrid rye to corn-wheat diet on mechanical properties of bones and tendons. A total of 224 broiler chickens were fed a diet without rye inclusion or a diet containing 15% of hybrid rye cv. Brasetto. The diets were either unsupplemented or supplemented with xylanase (minimum activity 1000 FXU/g, dose 200 mg/kg of feed). Each dietary group consisted of 56 birds. On day 42, selected chickens (n = 7 from each group) were slaughtered. Tibia were analyzed for mineralization, geometry, and biomechanical characteristics of bone mid-diaphysis. The mechanical properties of digital flexor III tendon were also assessed. Bone mineral density and bone ash percentage did not differ when both diets were given without xylanase. Enzyme supplementation increased bone mineral density (P < 0.01) in both dietary groups, whereas bone ash percentage (P < 0.01) increased only for corn-wheat diet. Rye inclusion had no effect on bone mid-shaft geometrical traits related to tibia weight-bearing capacity (cross-sectional area, cortical index, and mean relative wall thickness). Performed bending test showed no effect of hybrid rye inclusion on bone mechanical endurance. When xylanase was supplemented, bone length (P < 0.01) and weight (P < 0.05) decreased, whereas yield load (P < 0.01), stiffness (P < 0.05), Young modulus (P < 0.05), elastics stress (P < 0.01), and ultimate stress (P < 0.01) increased, irrespective of rye presence. The tendon tensile strain test showed that in corn-wheat diet enzyme supplementation positively influenced rupture force (P < 0.05) and tendon stiffness (P < 0.01). Xylanase supplementation increased the value of energy required to tendon rupture, irrespective of rye inclusion (P < 0.05). Study showed that modern hybrid rye varieties can be introduced to corn-wheat diets of broiler chickens in the aspect of animal welfare related to the development and homeostasis of musculoskeletal system, irrespective of xylanase supplementation. The enzyme addition positively affected biomechanical properties of bones and tendons.

Does glucocorticoid exposure explain the association between metabolic dysfunction and tendinopathy?

BACKGROUND

While metabolic health is acknowledged to affect connective tissue structure and function, the mechanisms are unclear. Glucocorticoids are present in almost every cell type throughout the body and control key physiological processes such as energy homeostasis, stress response, inflammatory and immune processes, and cardiovascular function. Glucocorticoid excess manifests as visceral adiposity, dyslipidaemia, insulin resistance, and type 2 diabetes. As these metabolic states are also associated with tendinopathy and tendon rupture, it may be that glucocorticoids excess is the link between metabolic health and tendinopathy.

OBJECTIVE

To synthesise current knowledge linking glucocorticoids exposure to tendon structure and function.

METHODS

Narrative literature review.

RESULTS

We provide an overview of endogenous glucocorticoid production, regulation, and signalling. Next we review the impact that oral glucocorticoid has on risk of tendon rupture and the effect that injected glucocorticoid has on resolution of symptoms. Then we highlight the clinical and mechanistic overlap between tendinopathy and glucocorticoid excess in the areas of visceral adiposity, dyslipidaemia, insulin resistance and type 2 diabetes. In these areas, we highlight the role of glucocorticoids and how these hormones might underpin the connection between metabolic health and tendon dysfunction.

CONCLUSIONS

There are several plausible pathways through which glucocorticoids might mediate the connection between metabolic health and tendinopathy.

Biomechanical Testing of Murine Tendons

Tendon disorders are common, affect people of all ages, and are often debilitating. Standard treatments, such as anti-inflammatory drugs, rehabilitation, and surgical repair, often fail. In order to define tendon function and demonstrate efficacy of new treatments, the mechanical properties of tendons from animal models must be accurately determined. Murine animal models are now widely used to study tendon disorders and evaluate novel treatments for tendinopathies; however, determining the mechanical properties of mouse tendons has been challenging. In this study, a new system was developed for tendon mechanical testing that includes 3D-printed fixtures that exactly match the anatomies of the humerus and calcaneus to mechanically test supraspinatus tendons and Achilles tendons, respectively. These fixtures were developed using 3D reconstructions of native bone anatomy, solid modeling, and additive manufacturing. The new approach eliminated artifactual gripping failures (e.g., failure at the growth plate failure rather than in the tendon), decreased overall testing time, and increased reproducibility. Furthermore, this new method is readily adaptable for testing other murine tendons and tendons from other animals.

The impact of cholesterol deposits on the fibrillar architecture of the Achilles tendon in a rabbit model of hypercholesterolemia

Background

Increased tendon pain and tendon damage is a significant complication related to hyperlipidemia. Unlike the well-established pathogenesis associated with increased serum concentrations of total cholesterol, triglycerides, and low-density lipoprotein in atherosclerotic cardiovascular disease, the role of hyperlipidemia in promoting tendon damage remains controversial and requires mechanistic clarity.

Methods

In this study, we analyzed the consequences of hypercholesterolemia on the integrity of the collagen-based architecture of the Achilles tendon. The Achilles tendons from rabbits fed with normal-cholesterol (nCH) and high-cholesterol (hCH) diets were analyzed. We studied the morphology of tendons, distribution of lipids within their collagen-rich milieu, the relative amounts of fibrillar collagen I and collagen III, and selected biomechanical parameters of the tendons at the macroscale and the nanoscale.

Results

Histological assays of hCH tendons and tenosynovium demonstrated hypercellular areas with increased numbers of macrophages infiltrating the tendon structure as compared to the nCH tendons. While Oil Red staining revealed lipid-rich deposits in the hCH tendons, hybridization of tendon tissue with the collagen hybridizing peptide (CHP) demonstrated damage to the collagen fibers. Fourier-transform infrared (FTIR) spectra showed the presence of distinct peaks consistent with the presence of cholesterol ester. Additionally, the hCH tendons displayed regions of poor collagen content that overlapped with lipid-rich regions. The hCH tendons had a substantial fourfold increase in the collage III to collagen I ratio as compared to the nCH tendons. Tendons from the hCH rabbits showed poor biomechanical characteristics in comparison with control. The biomechanical changes were evident at the macrolevel and the nanolevel of tendon structure.

Conclusions

Our findings support the hypothesis that hypercholesterolemia coincides with the weakening of the tendons. It is likely that the intimate contact between collagen fibrils and cholesterol deposits contributes to the weakening of the fibrillar structure of the tendons.

Is There a Relation Between Lateral Epicondylitis and Total Cholesterol Levels?

PURPOSE

To investigate whether high total cholesterol (TC) levels are associated with lateral epicondylitis (LE).

METHODS

We retrospectively reviewed all patients with LE who presented to our institution between 2011 and 2015. The inclusion criteria were a diagnosis of LE based on clinical history and physical examination findings and age between 40 and 55 years. For healthy controls, we obtained data from a national cohort (sixth Korean National Health and Nutrition Examination Survey) aged between 40 and 55 years. We compared TC levels between the groups, determined the incidence of hypercholesterolemia (TC level ≥ 240 mg/dL) according to the occurrence of LE, and calculated odds ratios for the occurrence of LE. We also evaluated whether cholesterol levels were associated with clinical findings of LE, such as pain level, onset age, symptom duration, and number of corticosteroid injections.

RESULTS

The study comprised 289 patients with LE (mean age, 47.9 years) and 1,077 healthy individuals (mean age, 47.7 years). TC levels were significantly higher in patients with LE than in healthy individuals (205.0 mg/dL vs 194.6 mg/dL, P < .001). The mean difference of 10.4 mg/dL was clinically meaningful because a change of 10 mg/dL with medical intervention is considered significant. The incidence of hypercholesterolemia was higher in LE patients than in healthy controls (16.6% vs 9.0%, P < .001). After adjustment for age, sex, body mass index, and glucose level, patients with hypercholesterolemia (TC level ≥ 240 mg/dL) were 2.47 (95% confidence interval, 1.65-3.70) times more likely to experience LE than those with normal cholesterol levels (<200 mg/dL). TC levels correlated with pain level, onset age, and number of corticosteroid injections.

CONCLUSIONS

A clinically meaningful difference in TC levels was found between LE patients and healthy controls. In addition, the incidence of hypercholesterolemia was higher in LE patients than in controls. The present findings suggest a potential association between high TC levels and LE.

LEVEL OF EVIDENCE

Level III, case-control study.

Sequential, but not Concurrent, Incubation of Cathepsin K and L with Type I Collagen Results in Extended Proteolysis

Degradation of extracellular matrix (ECM) during tendinopathy is, in part, mediated by the collagenolytic cathepsin K (catK) and cathepsin L (catL), with a temporal component to their activity. The objective of this study was to determine how catK and catL act in concert or in conflict to degrade collagen and tendon ECM during tissue degeneration. To do so, type I collagen gels or ECM extracted from apolipoprotein E deficient mouse Achilles tendons were incubated with catK and catL either concurrently or sequentially, incubating catK first, then catL after a delayed time period. Sequential incubation of catK then catL caused greater degradation of substrates over concurrent incubation, and of either cathepsin alone. Zymography showed there were reduced amounts of active enzymes when co-incubated, indicating that cannibalism, or protease-on-protease degradation between catK and catL was occurring, but incubation with ECM could distract from these interactions. CatK alone was sufficient to quickly degrade tendon ECM, but catL was not, requiring the presence of catK for degradation. Together, these data identify cooperative and conflicting actions of cathepsin mediated collagen matrix degradation by considering interactive effects of multiple proteases during tissue degeneration.

Load magnitude affects patellar tendon mechanical properties but not collagen or collagen cross-linking after long-term strength training in older adults

BACKGROUND

Regular loading of tendons may counteract the negative effects of aging. However, the influence of strength training loading magnitude on tendon mechanical properties and its relation to matrix collagen content and collagen cross-linking is sparsely described in older adults. The purpose of the present study was to compare the effects of moderate or high load resistance training on tendon matrix and its mechanical properties.

METHODS

Seventeen women and 19 men, age 62-70 years, were recruited and randomly allocated to 12 months of heavy load resistance training (HRT), moderate load resistance training (MRT) or control (CON). Pre- and post-intervention testing comprised isometric quadriceps strength test (IsoMVC), ultrasound based testing of in vivo patellar tendon (PT) mechanical properties, MRI-based measurement of PT cross-sectional area (CSA), PT biopsies for assessment of fibril morphology, collagen content, enzymatic cross-links, and tendon fluorescence as a measure of advanced glycation end-products (AGEs).

RESULTS

Thirty three participants completed the intervention and were included in the data analysis. IsoMVC increased more after HRT (+ 21%) than MRT (+ 8%) and CON (+ 7%) (p < 0.05). Tendon stiffness (p < 0.05) and Young's modulus (p = 0.05) were also differently affected by training load with a reduction in CON and MRT but not in HRT. PT-CSA increased equally after both MRT and HRT. Collagen content, fibril morphology, enzymatic cross-links, and tendon fluorescence were unaffected by training.

CONCLUSION

Despite equal improvements in tendon size after moderate and heavy load resistance training, only heavy. load training seemed to maintain tendon mechanical properties in old age. The effect of load magnitude on tendon biomechanics was unrelated to changes of major load bearing matrix components in the tendon core. The study is a sub-study of the LISA study, which was registered at http://clinicaltrials.gov (NCT02123641) April 25th 2014.

The Effect of Lipid Disorders on the Risk of Rotator Cuff Disease: A Systematic Review and Meta-Analysis

Background

Rotator cuff disease has a high prevalence and is associated with shoulder pain and disability. Dyslipidemia might be an intrinsic factor related to the development of the disease as it might increase tendon stiffness and result in tendon problems. The purposes of the present study were (1) to systematically review the association between lipid disorders and the risk of rotator cuff disease and (2) to provide physicians with guidance to prevent rotator cuff disease.

Methods

Six databases were searched through July 6, 2016: MEDLINE, Embase, CINAHL, Web of Science, SPORTDiscus, and the Cochrane Central Register of Controlled Trials. Eligible studies were assessed for risk of bias and strength of evidence. Meta-analysis was performed for the effect of dyslipidemia on the presence of rotator cuff disease, with the effect being expressed as an odds ratio. The overall effect was estimated, and heterogeneity across studies was expressed with the I² statistic. We used standard and contour-enhanced funnel plots as well as the Begg and Egger tests to check for publication bias.

Results

Three cross-sectional studies, 1 cohort study, and 3 case-control studies involving 505,852 participants were selected, with 6 of these studies being eligible for meta-analysis. The main-effect meta-analysis yielded a pooled odds ratio of 2.17 (95% confidence interval, 1.46 to 3.23; p < 0.001; I² = 82.4%), indicating a higher rate of rotator cuff disease in patients with dyslipidemia. The sensitivity analysis was not different from the main-effect analysis. Contour-enhanced funnel plots revealed the possibility of publication bias or other small-study effects.

Conclusions

We found that dyslipidemia was associated with high occurrence of rotator cuff disease. We recommend that physicians examine tendon conditions if their patients have severe dyslipidemia.

Level of Evidence

Prognostic Level IV. See Instructions for Authors for a complete description of levels of evidence.

The effects of hyperlipidemia on rotator cuff diseases: a systematic review

BACKGROUND

Rotator cuff disease is a common condition that causes shoulder pain and functional disability. Recent studies suggested that hyperlipidemia might be associated with the development of rotator cuff disease. The objective of this study was to explore the relationship of hyperlipidemia and rotator cuff diseases.

METHODS

A computerized search using relevant search terms was performed in the PubMed, EMBASE, and Cochrane Library databases, as well as a manual search of reference and citation lists of the included studies. Searches were limited to studies that explored the association of hyperlipidemia and rotator cuff diseases.

RESULTS

Sixteen studies were included in this systematic review. Ten of sixteen included studies suggested an association between dyslipidemia and rotator cuff diseases, while the other six studies did not find an association. Two studies demonstrated there were an association between statins and reduced risk of developing rotator cuff diseases or decreased incidence of revision after rotator cuff repair.

CONCLUSION

The current study suggested that there was an association between hyperlipidemia and rotator cuff diseases. Furthermore, current evidence suggested that use of statins could decrease the risk of developing rotator cuff diseases and the incidence of revision after rotator cuff repair. Future high-quality studies are highly needed to confirm these findings.

Tendon pathology in hypercholesterolaemia patients: Epidemiology, pathogenesis and management

Tendon pathology is a general term used to describe a group of musculoskeletal conditions related to tendons and surrounding structures. There is only limited evidence available regarding the exact aetiology and natural history of tendon pathology. In hypercholesterolaemia environments, lipids could accumulate within the extracellular matrix of the tendon and thus affect the mechanical properties of the tendon. Current evidence suggested that hypercholesterolaemia was an important risk factor in the development and progression of tendon pathology. The severity of hypercholesterolaemia was correlated with the severity of tendon pathology.

The translational potential of this article: Hypercholesterolaemia lead to the structural, inflammatory and mechanical changes in tendons, which predispose hypercholesterolaemia patients to a greater risk of tendon pathology. Measurements of serum cholesterol are suggested to be performed in patients presenting with tendon pathology. The strict control of hypercholesterolaemia would mitigate the development and progression of tendon pathology.

Lower tendon stiffness in very old compared with old individuals is unaffected by short-term resistance training of skeletal muscle

Aging negatively affects collagen-rich tissue, like tendons, but in vivo tendon mechanical properties and the influence of physical activity after the 8th decade of life remain to be determined. This study aimed to compare in vivo patellar tendon mechanical properties in moderately old (old) and very old adults and the effect of short-term resistance training. Twenty old (9 women, 11 men, >65 yr) and 30 very old (11 women, 19 men, >83 yr) adults were randomly allocated to heavy resistance training (HRT) or no training (CON) and underwent testing of in vivo patellar tendon (PT) mechanical properties and PT dimensions before and after a 3-mo intervention. Previous measurements of muscle properties, blood parameters, and physical activity level were included in the analysis. Data from 9 old HRT, 10 old CON, 14 very old CON, and 12 old HRT adults were analyzed. In addition to lower quadriceps muscle strength and cross-sectional area (CSA), we found lower PT stiffness and Young's modulus ( P < 0.001) and a trend toward the lower mid-portion PT-CSA ( P = 0.09) in very old compared with old subjects. Daily step count was also lower in very old subjects ( P < 0.001). Resistance training improved muscle strength and cross-sectional area equally in old and very old subjects ( P < 0.05) but did not affect PT mechanical properties or dimension. We conclude that PT material properties are reduced in very old age, and this may likely be explained by reduced physical activity. Three months of resistance training however, could not alter PT mechanical properties in very old individuals. NEW & NOTEWORTHY This research is the first to quantify in vivo tendon mechanical properties in a group of very old adults in their eighties. Patellar tendon stiffness was lower in very old (87 yr on average) compared with moderately old (68 yr on average) individuals. Reduced physical activity with aging may explain some of the loss in tendon stiffness, but regular heavy resistance training for 3 mo was not sufficient to change tendon mechanical properties.

The effect of lipid levels on patient-reported outcomes in patients with rotator cuff tears

Background

Lipid disorders could be associated with the prevalence and outcomes of rotator cuff diseases. This study aimed to learn how levels of various types of lipids influence the patient-reported outcomes of patients with rotator cuff tears (RCTs).

Methods

Data from a cohort study of 135 patients with RCTs were used. The outcome measures included Western Ontario Rotator Cuff (WORC) index, American Shoulder and Elbow Surgeons (ASES) standardized shoulder assessment form, Single Assessment Numeric Evaluation, visual analog scale for pain and satisfaction, and Veterans RAND 12-Item Health Survey (VR-12). Multivariable random-effects models were built to examine how total cholesterol, triglycerides, high-density lipoprotein (HDL), low-density lipoprotein, and ratio of total cholesterol to HDL influence each outcome, controlling for covariates.

Results

After adjusting for age, gender, surgery, smoking, and baseline outcome values, patients with triglycerides >150 mg/dL had significantly higher pain visual analog scale (β = 5.86; P = .017) and lower VR-12 physical component summary (β = −2.71; P = .002) scores. Patients with low HDL had significantly worse WORC (β = 132.26; P = .020) and ASES (β = −7.05; P = .005) scores, more pain (β = 6.69; P = .024), and less satisfaction (β = −6.53; P = .008). The ratio of total cholesterol to HDL was associated with worse WORC (β = 58.46; P = .006) and ASES scores (β = −2.74; P = .002), more pain (β = 4.49; P < .001), and worse VR-12 physical component summary score (β = −1.03; P = .017).

Conclusions

Dyslipidemia may decrease the improvement of patient-reported outcomes in patients undergoing treatment for RCTs; high triglycerides and low HDL may have the most impact.

Perioperative Serum Lipid Status and Statin Use Affect the Revision Surgery Rate After Arthroscopic Rotator Cuff Repair

BACKGROUND

Recent animal studies have demonstrated that hyperlipidemia is associated with poor tendon-bone healing after rotator cuff repair; however, these findings have not been substantiated in human studies.

PURPOSE

To examine any association between hyperlipidemia and the failure of arthroscopic rotator cuff repair requiring revision surgery and to investigate whether the use of statin lipid-lowering agents had any influence on observed associations.

STUDY DESIGN

Cohort study; Level of evidence, 3.

METHODS

From a national insurance database, patients who underwent arthroscopic rotator cuff repair with perioperative lipid levels (total cholesterol, low-density lipoprotein [LDL], and triglycerides) recorded were reviewed. For each lipid test, patients were stratified into normal, moderate, and high groups based on published standards. For the total cholesterol and LDL cohorts, a subgroup analysis of patients stratified by statin use was performed. The primary outcome measure was ipsilateral revision rotator cuff surgery, including revision repair or debridement. A logistic regression analysis controlling for patient demographics and comorbidities was utilized for comparison.

RESULTS

There were 30,638 patients included in the study. The rate of revision rotator cuff surgery was significantly increased in patients with moderate (odds ratio [OR], 1.20; 95% CI, 1.03-1.40; P = .022) and high total cholesterol levels (OR, 1.36; 95% CI, 1.10-1.55; P = .006) compared with patients with normal total cholesterol levels perioperatively. Within each of these groups, patients without statin use had significantly higher rates of revision surgery, while those with statin prescriptions did not. The absolute risk reduction for statin use ranged from 0.24% to 1.87% when stratified by the total cholesterol level, yielding a number needed to treat from 54 to 408 patients. The rate of revision surgery was significantly increased in patients with moderate (OR, 1.24; 95% CI, 1.10-1.41; P = .001) and high LDL levels (OR, 1.46; 95% CI, 1.08-1.99; P = .014) compared with patients with normal LDL levels perioperatively. Again, patients without statin prescriptions had significantly increased rates of revision surgery, whereas patients with statin use did not. The absolute risk reduction for statin use ranged from 0.26% to 1.89% when stratified by the LDL level, yielding a number needed to treat from 53 to 387 patients. There were no significant differences in the rates of revision rotator cuff surgery between patients with moderate and high triglyceride levels compared with patients with normal triglyceride levels.

CONCLUSION

The present study found a significant association between moderate and high perioperative total cholesterol and LDL levels and the rate of revision surgery after primary arthroscopic rotator cuff repair. Furthermore, the use of statin agents appeared to mitigate the need for revision rotator cuff repair. Further prospective studies are necessary to validate these preliminary findings and determine if better perioperative lipid control can improve clinical outcomes after arthroscopic rotator cuff repair.

What is the role of systemic conditions and options for manipulation of bone formation and bone resorption in rotator cuff tendon healing and repair?

Rotator cuff pathology is a significant cause of shoulder pain. Operative repair of rotator cuff is an established standard of care for these patient, however, failure of the procedure is common. Systemic conditions such as diabetes mellitus, hypocholesteremia, thyroid disease, and smoking significantly affect the outcomes of rotator cuff repair and have significant implications for the management of these patients. Diabetes mellitus has been proposed to damage tendons through non-enzymatic glycosylation of collagen with advanced glycation end product formation and impaired microcirculation. Hypocholesteremia may lead to fatty infiltration and subsequent pro-inflammatory degenerative enzymatic degeneration. Thyroid disease may disrupt tendon homeostasis through the alteration of collagen production and the accumulation of glycosaminoglycans. Lastly, smoking inhibits tendon healing through the induction of hypovascularity and hypoperfusion. Understanding of the implications these systemic conditions have on the outcomes is important in the management of rotator cuff disease.

Atorvastatin inhibits cholesterol-induced caspase-3 cleavage through down-regulation of p38 and up-regulation of Bcl-2 in the rat carotid artery

AIM

Atherosclerotic lesions in the carotid arteries lead to a broad range of cerebrovascular disorders such as vascular dementia and ischaemic stroke. Recent studies have verified the beneficial role of atorvastatin (AV) in atherosclerosis. Despite a large body of studies, the mechanisms underlying this effect have not been completely explained. In this study, several experiments were performed on atherosclerotic rat models to investigate the anti-inflammatory and anti-apoptotic effect of AV in the carotid artery.

METHODS

In this experimental study, 40 male Wistar rats (250 ± 25 g) were randomly divided into four groups: rats on a normal diet (ND; n = 10); a high-cholesterol diet (HD; n = 10); a high-cholesterol diet plus AV (HD + AV; n = 10) ; and the AV control group (AV; n = 10). Cleavage of caspase-3 protein, expression of B-cell lymphoma 2 (Bcl-2) as well as phosphorylation of p38 mitogen-activated protein kinase (MAPK) were determined by immunoblotting assay in the carotid artery homogenate. Plasma atherogenic indices, including total cholesterol (TC), high-density lipoprotein cholesterol (HDL-C) and low-density lipoprotein cholesterol (LDL-C) were measured by colorimetric assay at the end of the experiment. Plasma levels of oxidised LDL (oxLDL) were measured by sandwich enzyme-linked immunosorbent assay (ELISA).

RESULTS

After eight weeks of feeding with a high-cholesterol diet, an elevated level of oxLDL was observed in the plasma in the HD group compared with the ND group [214.42 ± 17.46 vs 69.13 ± 9.92 mg/dl (5.55 ± 0.45 vs 1.78 ± 0.26 mmol/l); p < 0.01]. AV administration significantly reduced oxLDL levels in the HD + AV compared to the HD group [126.52 ± 9.46 vs 214.42 ± 17.46 mg/dl (3.28 ± 0.25 vs 5.55 ± 0.45 mmol/l); p < 0.01]. Results also showed that compared with the HC group, the HC + AV group had lower levels of p38 phosphorylation (p < 0.05) and higher levels of Bcl-2 expression (p < 0.05). Lower levels of cleaved caspase-3 were observed in the HC + AV group in comparison with the HC group (p < 0.05).

CONCLUSIONS

The resultant data suggest that the anti-apoptotic effect of AV could be partially mediated by the pro-inflammatory protein p38 MAPK and the anti-apoptotic protein Bcl-2 in the rat carotid artery. Atorvastatin can therefore be considered a target drug in the prevention or development of atherosclerotic events.

Effect of simvastatin on rat supraspinatus tendon mechanical and histological properties in a diet-induced hypercholesterolemia model

Hypercholesterolemia is a common condition and is a risk factor for tendon rupture, specifically in the supraspinatus tendon. In the clinic, statins are commonly prescribed to lower cholesterol, but little information is available examining the effect of statin treatment on the musculoskeletal system. Therefore, the objective of this study was to determine the biomechanical and histological effects of statin treatment in a diet-induced hypercholesterolemia model. We hypothesized that hypercholesterolemic rats treated with statins would have improved tendon biomechanical and histological properties compared to hypercholesterolemic rats not receiving daily statin treatment. Thirty adult male Sprague-Dawley rats ate either high-cholesterol (HC) diet (n = 20) or normal chow (CTL, n = 10). After 6 months, a subset of HC rats began daily oral simvastatin dosing (HC+S) at 20 mg/kg. All rats were sacrificed after a total of 9 months (3 months of statin treatment) and evaluated for histology and mechanics. For mechanics, at the insertion region, HC+S group had increased tendon cross-sectional area decreased and modulus. No differences were noted in mechanical properties at the midsubstance. For histology, no differences were noted in the insertion region. In the midsubstance region, HC+S group had more spindle shaped cells. Our results suggest that 3 months of simvastatin treatment in a diet-induced hypercholesterolemia rat model alters some tendon mechanical and histological properties, although a strong conclusion in support of improved parameters cannot be drawn. Therefore, we conclude that simvastatin treatment does not negatively affect tendon properties. © 2016 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 34:2009-2015, 2016.

Influence of Hyperlipidemia on the Treatment of Supraspinatus Tendinopathy With or Without Tear

Objective

To investigate the influence of hyperlipidemia on the treatment of supraspinatus tendinopathy, with or without tear.

Methods

We retrospectively reviewed the data of patients with shoulder pain and patients with supraspinatus tendinopathy, with or without tear, were included in the study. Exclusion criteria were prior shoulder surgery, prior steroid injection, neurological diseases that could lead to shoulder pain, and use of lipid-lowering medication. According to the serum lipid profiles, patients were assigned to either the hyperlipidemia or non-hyperlipidemia group. By analyzing the numeric rating scale (NRS) before treatment, and at 2 weeks and 8 weeks after treatment, we compared the difference in treatment effect between the two groups.

Results

No significant baseline difference was found among the two groups for age, gender, body mass index, duration of pain, side of pain, range of motion of affected shoulder, or physical examination. On the repeated-measures analysis of variance, NRS scores significantly decreased with time for both groups (p<0.001). When analyzing the effect of time between the subjects factor, there was significant difference in the treatment effect between the two groups (p<0.001), namely NRS was less decreased in the hyperlipidemia group.

Conclusion

We found that hyperlipidemia may be an adversely affecting factor in the treatment of supraspinatus tendinopathy with or without tear.

Collagen V-heterozygous and -null supraspinatus tendons exhibit altered dynamic mechanical behaviour at multiple hierarchical scales

Tendons function using a unique set of mechanical properties governed by the extracellular matrix and its ability to respond to varied multi-axial loads. Reduction of collagen V expression, such as in classic Ehlers-Danlos syndrome, results in altered fibril morphology and altered macroscale mechanical function in both clinical and animal studies, yet the mechanism by which changes at the fibril level lead to macroscale functional changes has not yet been investigated. This study addresses this by defining the multiscale mechanical response of wild-type, collagen V-heterozygous and -null supraspinatus tendons. Tendons were subjected to mechanical testing and analysed for macroscale properties, as well as microscale (fibre re-alignment) and nanoscale (fibril deformation and sliding) responses. In many macroscale parameters, results showed a dose-dependent response with severely decreased properties in the null group. In addition, both heterozygous and null groups responded to load faster than in wild-type tendons via earlier fibre re-alignment and fibril stretch. However, the heterozygous group exhibited increased fibril sliding, while the null group exhibited no fibril sliding. These studies demonstrate that dynamic responses play an important role in determining overall function and that collagen V is a critical regulator in the development of these relationships.

Is higher serum cholesterol associated with altered tendon structure or tendon pain? A systematic review

Background

Tendon pain occurs in individuals with extreme cholesterol levels (familial hypercholesterolaemia). It is unclear whether the association with tendon pain is strong with less extreme elevations of cholesterol.

Objective

To determine whether lipid levels are associated with abnormal tendon structure or the presence of tendon pain.

Methods

We conducted a systematic review and meta-analysis. Relevant articles were found through an electronic search of 6 medical databases—MEDLINE, Cochrane, AMED, EMBASE, Web of Science and Scopus. We included all case–control or cross-sectional studies with data describing (1) lipid levels or use of lipid-lowering drugs and (2) tendon structure or tendon pain.

Results

17 studies (2612 participants) were eligible for inclusion in the review. People with altered tendon structure or tendon pain had significantly higher total cholesterol, low-density lipoprotein cholesterol and triglycerides, as well as lower high-density lipoprotein cholesterol; with mean difference values of 0.66, 1.00, 0.33, and −0.19 mmol/L, respectively.

Conclusions

The results of this review indicate that a relationship exists between an individual’s lipid profile and tendon health. However, further longitudinal studies are required to determine whether a cause and effect relationship exists between tendon structure and lipid levels. This could lead to advancement in the understanding of the pathoaetiology and thus treatment of tendinopathy.

Tensile properties of craniofacial tendons in the mature and aged zebrafish

The zebrafish Danio rerio is a powerful model for the study of development, regenerative biology, and human disease. However, the analysis of load-bearing tissues such as tendons and ligaments has been limited in this system. This is largely due to technical limitations that preclude accurate measurement of their mechanical properties. Here, we present a custom tensile testing system that applies nano-Newton scale forces to zebrafish tendons as small as 1 mm in length. Tendon properties were remarkably similar to mammalian tendons, including stress-strain nonlinearity and a linear modulus (515 ± 152 MPa) that aligned closely with mammalian data. Additionally, a simple exponential constitutive law used to describe tendon mechanics was successfully fit to zebrafish tendons; the associated material constants agreed with literature values for mammalian tendons. Finally, mature and aged zebrafish comparisons revealed a significant decline in mechanical function with age. Based on the exponential constitutive model, age-related changes were primarily caused by a reduction in nonlinearity (e.g., changes in collagen crimp or fiber recruitment). These findings demonstrate the utility of zebrafish as a model to study tendon biomechanics in health and disease. Moreover, these findings suggest that tendon mechanical behavior is highly conserved across vertebrates.

Accumulation of oxidized LDL in the tendon tissues of C57BL/6 or apolipoprotein E knock-out mice that consume a high fat diet: potential impact on tendon health

Objective

Clinical studies have suggested an association between dyslipidemia and tendon injuries or chronic tendon pain; the mechanisms underlying this association are not yet known. The objectives of this study were (1) to evaluate the impact of a high fat diet on the function of load-bearing tendons and on the distribution in tendons of oxidized low density lipoprotein (oxLDL), and (2) to examine the effect of oxLDL on tendon fibroblast proliferation and gene expression.

Methods

Gene expression (Mmp2, Tgfb1, Col1a1, Col3a1), fat content (Oil Red O staining), oxLDL levels (immunohistochemistry) and tendon biomechanical properties were examined in mice (C57Bl/6 or ApoE -/-) receiving a standard or a high fat diet. Human tendon fibroblast proliferation and gene expression (COL1A1, COL3A1, MMP2) were examined following oxLDL exposure.

Results

In both types of mice (C57Bl/6 or ApoE -/-), consumption of a high fat diet led to a marked increase in oxLDL deposition in the load-bearing extracellular matrix of the tendon. The consumption of a high fat diet also reduced the failure stress and load of the patellar tendon in both mouse types, and increased Mmp2 expression. ApoE -/- mice exhibited more pronounced reductions in tendon function than wild-type mice, and decreased expression of Col1a1 compared to wild type mice. Human tendon fibroblasts responded to oxLDL by increasing their proliferation and their mRNA levels of MMP2, while decreasing their mRNA levels for COL1A1 and COL3A1.

Conclusion

The consumption of a high fat diet resulted in deleterious changes in tendon function, and these changes may be explained in part by the effects of oxLDL, which induced a proliferative, matrix-degrading phenotype in human tenocytes.

Systemic stiffening of mouse tail tendon is related to dietary advanced glycation end products but not high-fat diet or cholesterol

Tendon pathology is related to metabolic disease and mechanical overloading, but the effect of metabolic disease on tendon mechanics is unknown. This study investigated the effect of diet and apolipoprotein E deficiency (ApoE(-/-)) on mechanical properties and advanced glycation end product (AGE) cross-linking of non-weight-bearing mouse tail tendons. Twenty ApoE(-/-) male mice were used as a model for hypercholesterolemia along with 26 wild-type (WT) mice. One-half of the mice from each group was fed a normal diet (ND) and the other half was fed a high-fat diet (HFD) to induce obesity. All were killed at 40 wk, and tail tendon fascicles were mechanically tested to failure and analyzed for AGEs. Diets were also analyzed for AGEs. ApoE(-/-) mice displayed a 14% increase in plateau modulus compared with WT mice (P < 0.05), whereas HFD mice displayed a 13% decrease in plateau modulus (P < 0.05) and a 12% decrease in total modulus (P < 0.05) compared with ND mice. Tail tendons of HFD mice had significantly lower concentrations of AGEs [carboxymethyllysine (CML): 26%, P < 0.0001; methylglyoxal-derived hydroimidazolone 1 (MG-H1): 15%, P < 0.005; pentosidine: 13%, P < 0.0005]. The HFD had ∼44-fold lower content of CML (P < 0.01), ∼29-fold lower content of carboxyethyllysine (P < 0.005), and ∼16-fold lower content of MG-H1 (P < 0.05) compared with ND. ApoE(-/-) increased, whereas HFD decreased mouse tail tendon stiffness. Dietary AGE content may be a crucial determinant for accumulation of AGE cross-links in tendons and for tissue compliance. The results demonstrate how systemic metabolic factors may influence tendon health.

The relationship between the mechanical properties of heel-pad and common clinical measures associated with foot ulcers in patients with diabetes

AIM

The present study aims at investigating the correlation between the mechanical properties of the heel-pad of people with type-2 diabetes and the clinical parameters used to monitor their health and ulceration risk.

METHODS

A new device for the in-vivo testing of plantar soft tissues was built and pilot-tested. This device consists of an ultrasound probe connected in series with a dynamometer. Loading is applied manually using a ball-screw actuator. A total of 35 volunteers with type-2 diabetes were recruited and the thickness, stiffness of their heel-pads as well as the energy absorbed during loading were assessed. The participants with diabetes also underwent blood tests and measurements of Ankle Brachial Index and Vibration Perception Threshold.

RESULTS

Pearson correlation analysis revealed strong correlations between triglycerides and heel-pad stiffness (r=0.675, N=27, p<0.001) and between triglycerides and energy (r=-0.598, N=27, p=0.002). A correlation of medium strength was found between Fasting Blood Sugar (FBS) and stiffness (r=0.408, N=29, p=0.043).

CONCLUSIONS

People with type-2 diabetes and high levels of triglycerides and FBS are more likely to have stiffer heel-pads. Increased stiffness could limit the tissues' ability to evenly distribute loads making them more vulnerable to trauma and ulceration.

Exploring the role of hypercholesterolemia in tendon health and repair

High cholesterol remains a significant healthcare problem, as more than 13% of adults in the U.S. are affected by hypercholesterolemia. The detrimental effects the disease has on cardiovascular health are well-documented, but the effects on the musculoskeletal system, and more specifically on tendons, have not been thoroughly examined. This paper provides an overview of work performed in our lab with various animal models to elucidate the relationship between high cholesterol and tendon biomechanical integrity and ability to heal. These studies highlight the complexity of relationships between multiple factors that influence tendon biomechanics, and it has offered a better understanding of the implications of high cholesterol on healthy and healing tendons.

The role of animal models in tendon research

Tendinopathy is a debilitating musculoskeletal condition which can cause significant pain and lead to complete rupture of the tendon, which often requires surgical repair. Due in part to the large spectrum of tendon pathologies, these disorders continue to be a clinical challenge. Animal models are often used in this field of research as they offer an attractive framework to examine the cascade of processes that occur throughout both tendon pathology and repair. This review discusses the structural, mechanical, and biological changes that occur throughout tendon pathology in animal models, as well as strategies for the improvement of tendon healing.

Cite this article: Bone Joint Res 2014;3:193–202.

Rat rotator cuff tendon-to-bone healing properties are adversely affected by hypercholesterolemia

BACKGROUND

Rotator cuff tendon tears represent a major component of reported orthopaedic injuries. In addition, more than one quarter of U.S. adults either currently have high cholesterol levels or have reduced their previously high cholesterol levels through the use of pharmaceuticals. Our clinical data have already linked hypercholesterolemia to full-thickness rotator cuff tears, and experimental data from our laboratory have shown effects on native tendon properties in multiple species. The objective of this study was to evaluate healing of supraspinatus tendons in our rat rotator cuff injury model. We hypothesized that tendon healing would be inferior in rats receiving a high-cholesterol diet for 6 months compared with those receiving standard chow.

METHODS

All animals were subjected to a unilateral supraspinatus detachment and repair surgery, with contralateral limbs serving as within-animal comparative data. Animals continued their respective diet courses, and their supraspinatus tendons were biomechanically or histologically evaluated at 2, 4, and 8 weeks postoperatively.

RESULTS

Biomechanical testing revealed a significant reduction in normalized stiffness in hypercholesterolemic rats compared with controls at 4 weeks after injury, whereas histologic analyses showed no significant differences in collagen organization, cellularity, or cell shape between groups.

CONCLUSION

On the basis of our findings, hypercholesterolemia may have a detrimental biomechanical effect on tendon healing in our rat rotator cuff injury and repair model.

LEVEL OF EVIDENCE

Basic science study, animal model.

Biomechanical and biochemical protective effect of low-level laser therapy for Achilles tendinitis

For three decades, low level laser therapy (LLLT) has been used for treatment of tendinitis as well as other musculoskeletal diseases. Nevertheless, the biological mechanisms involved remain not completely understood. In this work, the effects of LLLT and of the widely used nonsteroidal anti-inflammatory drug, diclofenac, have been compared in the case of collagenase-induced Achilles tendinitis. Wistar rats were treated with diclofenac or laser therapy. The tensile behavior of tendons was characterized through successive loading-unloading sequences. The method considered 11 characteristic parameters to describe the mechanical behavior. It was shown that during the acute inflammatory process of the tendon, the mechanical properties were significantly correlated to the high levels of MMP-3, MMP-9 and MMP-13 expression presented in a previous paper (Marcos, R.L., et al., 2012). The treatment by non-steroidal anti-inflammatory drugs such as diclofenac sodium produces a low protective effect and can affect the short-term biochemical and biomechanical properties. On the contrary, it is shown that LLLT exhibits the best results in terms of MMPs reduction and mechanical properties recovery. Thus, LLLT looks to be a promising and consistent treatment for tendinopathies.