Emerging ideas: the effect of hypercholesterolemia on tendons

Novel application of in vivo microdialysis in a rat Achilles tendon acute injury model

Tendon injury and healing involve intricate changes to tissue metabolism, biology, and inflammation. Current techniques often require animal euthanasia or tissue destruction, limiting assessment of dynamic changes in tendon, including treatment response, disease development, rupture risk, and healing progression. Microdialysis, a minimally invasive technique, offers potential for longitudinal assessment, yet it has not been applied to rat tendon models. Therefore, the objective of this study is to adapt a novel application of an in vivo assay, microdialysis, using acute injury as a model for extreme disruption of the tendon homeostasis. We hypothesize that microdialysis will be able to detect measurable differences in the healing responses of acute injury with high specificity and sensitivity. Overall results suggest that microdialysis is a promising in vivo technique for longitudinal assessment for this system with strong correlations between extracellular fluid (ECF) and dialysate concentrations and reasonable recovery rates considering the limitations of this model. Strong positive correlations were found between dialysate and extracellular fluid (ECF) concentration for each target molecule of interest including metabolites, inflammatory mediators, and collagen synthesis and degradation byproducts. These results suggest that microdialysis is capable of detecting changes in tendon healing following acute tendon injury with high specificity and sensitivity. In summary, this is the first study to apply microdialysis to a rat tendon model and assess its efficacy as a direct measurement of tendon metabolism, biology, and inflammation.NEW & NOTEWORTHY This study adapts a novel application of microdialysis to rat tendon models, offering a minimally invasive avenue for longitudinal tendon assessment. Successfully detecting changes in tendon healing after acute injury, it showcases strong correlations between extracellular fluid and dialysate concentrations. The results highlight the potential of microdialysis as a direct measure of tendon metabolism, biology, and inflammation, bypassing the need for animal euthanasia and tissue destruction.

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.

Insertional Calcific Tendinopathy of the Achilles Tendon and Dysmetabolic Diseases: An Epidemiological Survey

OBJECTIVE

This study reports the incidence of insertional calcific tendinopathy (ICT) of the Achilles tendon in the general population and the percentage of symptomatic patients. The secondary aim is to ascertain whether ICT is associated with diabetes mellitus, thyroid disorders, obesity, and hypercholesterolemia. We hypothesized that metabolic diseases increase the risk of ICT of the Achilles tendon.

DESIGN

Prospective observational study (level III study).

SETTING

Orthopedic Outpatients Clinic and Emergency Department of Tor Vergata University Hospital, Rome, Italy.

PARTICIPANTS

Four hundred thirty-three subjects who met the inclusion criteria.

INTERVENTION METHODS

We collected the plain radiographs of the foot and ankle of patients who attended the hospital. Personal data were recorded [age, sex, and body mass index (BMI)], and comorbidities investigated (diabetes mellitus, hypothyroidism, hyperthyroidism, obesity, and hypercholesterolemia). Multivariate regression analyses were performed to study the predictors of the occurrence of Achilles ICT.

RESULTS

A total of 101 patients (23.3%) showed radiographic evidence of ICT, and 3% (13 patients) were symptomatic. Age [odds ratio (OR) 1.05], diabetes (OR 2.95), hypercholesterolemia (OR 2.27), and hypothyroidism (OR 3.32) were significantly associated with the presence of ICT of the Achilles tendon. Independent predictors of ICT were age, diabetes, hypercholesterolemia, and hypothyroidism. A BMI >30 was associated with a higher incidence of calcifications, and patients with 2 or more comorbidities had more than 10 times higher risk to develop ICT.

CONCLUSION

Insertional calcific tendinopathy of the Achilles tendon is common, but few patients are symptomatic. The incidence of ICT increases with age and is significantly higher in patients with diabetes mellitus and hypothyroidism.

Sonographic Assessment of Heel Pad Thickness in Patients With Poorly Controlled Diabetes

The aim was to compare the heel pad thickness (HPT) in diabetic patients with high biochemical parameters (fasting blood sugar [FBS], hemoglobin A1c [HbA1c], and lipid profile) with nondiabetic counterparts. A total of 438 subjects made up of 216 diabetics with high biochemical parameters (poorly controlled) and 222 apparently healthy subjects were recruited. The HPT, FBS level, HbA1c values and lipid profile, and duration of diabetes mellitus were assessed. Results showed that the mean HPT was 13.33 ± 1.29 mm in the control subjects and 16.79 ± 1.84 mm in diabetics. The HPT among diabetics differed significantly from the control group ( P < .05). The mean value of HbA1c in the control group was 5.4 ± 1.3 compared to diabetics with values of 8.53 ± 2.1. The values of HbA1c among diabetics were significantly higher than that of the control group ( P < .05). HPT had a significant linear relationship with HbA1c among the diabetic subjects ( r = 0.42, P < .05).

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.

EXERCISE THERAPY IN THE NON-OPERATIVE TREATMENT OF FULL-THICKNESS ROTATOR CUFF TEARS: A SYSTEMATIC REVIEW

BACKGROUND

Although commonly prescribed, the evidence to support exercises therapy (ET) and conservative management for the treatment of full-thickness rotator cuff tears (FTT) is equivocal.

PURPOSE

The purpose of this systematic review of the literature was to determine the current level of evidence available for ET in the treatment of FTT and to provide a formal Grading of Recommendations Assessment, Development and Evaluation (GRADE) Working Group of recommendation.

METHODS

Five databases were systematically searched to evaluate the effectiveness of ET for FTT. Inclusion criteria: experimental or observational studies of adults clinically diagnosed with FTT, or massive, or inoperable tears that contained a treatment group that received ET for FTT. Exclusion criteria included: history of surgical repair, concurrent significant trauma, neurological impairment, and level V studies. Articles were assessed for quality, the level of evidence (I - V) and GRADE of recommendation (A to F) was determined. Data extraction included: demographics, specific interventions, and outcomes.

RESULTS

One thousand, five-hundred and sixty-nine unique citations were identified, 35 studies were included: nine randomized controlled studies, six cohort studies, 15 case series and five case reports. There were 2010 shoulders in 1913 subjects with an average age of 64.2 years, 54% males, 73% of tears were > 1 cm and 37% were classified as massive. Based on studies that reported, >58% of tears were > 1 year and 73% were atraumatic. Of the non-operatively treated cohorts that reported the respective outcomes: 78% improved in pain (9/10 cohorts that reported statistically significant differences [stat-sig] p<0.05), 81% improved in ROM (14/14 cohorts that reported, met stat-sig), 85% improved in strength (7/8 cohorts that reported, met stat-sig), 84% improved in functional outcomes (17/17 cohorts that reported, met stat-sig). Dissatisfied outcomes occurred in 15% of patients, who then transitioned to surgery.

CONCLUSION

The current literature indicates GRADE B recommendation (moderate strength) to support the use of ET in the management of FTT. There is further need for well-designed randomized controlled trials.

LEVEL OF EVIDENCE

2a.

A service evaluation and improvement project: a three year systematic audit cycle of the physiotherapy treatment for Lateral Epicondylalgia

OBJECTIVES

To improve outcomes of physiotherapy treatment for patients with Lateral Epicondylalgia.

DESIGN

A systematic audit and quality improvement project over three phases, each of one year duration.

SETTING

Salford Royal NHS Foundation Trust Teaching Hospital Musculoskeletal Physiotherapy out-patients department.

PARTICIPANTS

n=182.

INTERVENTIONS

Phase one - individual discretion; Phase two - strengthening as a core treatment however individual discretion regarding prescription and implementation; Phase three - standardised protocol using high load isometric exercise, progressing on to slow combined concentric & eccentric strengthening.

MAIN OUTCOME MEASURES

Global Rating of Change Scale, Pain-free grip strength, Patient Rated Tennis Elbow Evaluation, Tampa Scale of Kinesophobia-11.

RESULTS

Phase three demonstrated a reduction in the average number of treatments by 42% whilst improving the number of responders to treatment by 8% compared to phase one. Complete cessation of non-evidence based treatments was also observed by phase three.

CONCLUSIONS

Strengthening should be a core treatment for LE. Load setting needs to be sufficient. In phase three of the audit a standardised tendon loading programme using patient specific high load isometric exercises into discomfort/pain demonstrated a higher percentage of responders compared to previous phases.

Micromechanical poroelastic finite element and shear-lag models of tendon predict large strain dependent Poisson's ratios and fluid expulsion under tensile loading

As tendons are loaded, they reduce in volume and exude fluid to the surrounding medium. Experimental studies have shown that tendon stretching results in a Poisson's ratio greater than 0.5, with a maximum value at small strains followed by a nonlinear decay. Here we present a computational model that attributes this macroscopic observation to the microscopic mechanism of the load transfer between fibrils under stretch. We develop a finite element model based on the mechanical role of the interfibrillar-linking elements, such as thin fibrils that bridge the aligned fibrils or macromolecules such as glycosaminoglycans (GAGs) in the interfibrillar sliding and verify it with a theoretical shear-lag model. We showed the existence of a previously unappreciated structure-function mechanism whereby the Poisson's ratio in tendon is affected by the strain applied and interfibrillar-linker properties, and together these features predict tendon volume shrinkage under tensile loading. During loading, the interfibrillar-linkers pulled fibrils toward each other and squeezed the matrix, leading to the Poisson's ratio larger than 0.5 and fluid expulsion. In addition, the rotation of the interfibrillar-linkers with respect to the fibrils at large strains caused a reduction in the volume shrinkage and eventual nonlinear decay in Poisson's ratio at large strains. Our model also predicts a fluid flow that has a radial pattern toward the surrounding medium, with the larger fluid velocities in proportion to the interfibrillar sliding.

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.

Tendinopathy in sport

CONTEXT

Tendinopathy is increasing in prevalence and accounts for a substantial part of all sports injuries and occupational disorders. Despite the magnitude of the disorder, high-quality scientific data on etiology and available treatments have been limited.

EVIDENCE ACQUISITION

The authors conducted a MEDLINE search on tendinopathy, or "tendonitis" or "tendinosis" or "epicondylitis" or "jumpers knee" from 1980 to 2011. The emphasis was placed on updates on epidemiology, etiology, and recent patient-oriented Level 1 literature.

RESULTS

Repetitive exposure in combination with recently discovered intrinsic factors, such as genetic variants of matrix proteins, and metabolic disorders is a risk factor for the development of tendinopathy. Recent findings demonstrate that tendinosis is characterized by a fibrotic, failed healing response associated with pathological vessel and sensory nerve ingrowth. This aberrant sensory nerve sprouting may partly explain increased pain signaling and partly, by release of neuronal mediators, contribute to the fibrotic alterations observed in tendinopathy. The initial nonoperative treatment should involve eccentric exercise, which should be the cornerstone (basis) of treatment of tendinopathy. Eccentric training combined with extracorporeal shockwave treatment has in some reports shown higher success rates compared to any therapies alone. Injection therapies (cortisone, sclerosing agents, blood products including platelet-rich plasma) may have short-term effects but have no proven long-term treatment effects or meta-analyses to support them. For epicondylitis, cortisone injections have demonstrated poorer long-time results than conservative physiotherapy. Today surgery is less indicated because of successful conservative therapies. New minioperative procedures that, via the endoscope, remove pathologic tissue or abnormal neoinnervation demonstrate promising results but need confirmation by Level 1 studies.

CONCLUSIONS

Novel targeted therapies are emerging, but multicenter trials are needed to confirm the results of exercise and mini-invasive treatments.

Tendon, tendon healing, hyperlipidemia and statins

Both hyperlipidemia and metabolic syndrome have adverse effect on tendon structure. Atorvastatin is most widely used antihyperlipidemic drug. Statins have adverse effects on the tendon. Many studies have analyzed the relationship between atorvastatin and skeletal muscles. Atorvastatin administered after the surgical repair of a ruptured tendon appears to affect revascularization, collagenization, inflammatory cell infiltration, and collagen construction. Therefore, further investigations on the effects of atorvastatin on tendon healing are needed.