S diagnosed with frozen shoulder from October 2009 to April 2013. Patients with diabetes, thyroid disease, or previous shoulder surgery or trauma were excluded. The control group comprised 900 age and sex-matched persons with normal shoulder function who visited our health promotion center for general check-ups during the same period. We calculated the odds ratios and 95% confidence intervals to identify any association between serum lipid level and primary frozen shoulder, using conditional logistic regression analysis. We evaluated continuous data on the serum levels of total cholesterol, calculated low-density lipoprotein, measured low-density lipoprotein, high-density lipoprotein, triglyceride, and non-high-density lipoprotein cholesterol. We also evaluated categorical data on hyper-cholesterolemia, hyper-low-density lipoproteinemia (calculated and measured), hyper-high-density lipoproteinemia, hyper-triglyceridemia, and hyper-non-high-density lipoprotein cholesterolemia. Results: Univariate analysis of the continuous data showed total cholesterol (odds ratio, 1.010 [95% confidence interval, 1.006 to 1.013]; p < 0.001), calculated low-density lipoprotein (odds ratio, 1.008 [95% confidence interval, 1.004 to 1.012]; p < 0.001), measured low-density lipoprotein (odds ratio, 1.007 [95% confidence interval, 1.003 to 1.011]; p = 0.001), high-density lipoprotein (odds ratio, 1.015 [95% confidence interval, 1.006 to 1.024]; p = 0.001), and non-high-density lipoprotein cholesterol (odds ratio, 1.007 [95% confidence interval, 1.004 to 1.011]; p < 0.001) to be significantly associated with primary frozen shoulder. Univariate analysis of categorical values showed hyper-cholesterolemia (odds ratio, 1.789 [95% confidence interval, 1.366 to 2.343]; p < 0.001), calculated hyper-low-density lipoproteinemia (odds ratio, 1.609 [95% confidence interval, 1.210 to 2.138]; p = 0.001), measured hyper-low-density lipoproteinemia (odds ratio, 1.643 [95% confidence interval, 1.190 to 2.269]; p = 0.003), hyper-high-density lipoproteinemia (odds ratio, 1.440 [95% confidence interval, 1.062 to 1.953]; p = 0.019), and hyper-non-high-density lipoprotein cholesterolemia (odds ratio, 1.645 [95% confidence interval, 1.259 to 2.151]; p < 0.001) to be significantly associated with primary frozen shoulder. Conclusions: We conclude that hypercholesterolemia and inflammatory lipoproteinemias, particularly hyper-low-density lipoproteinemia and hyper-non-high-density lipoprotein cholesterolemia, have a significant association with primary frozen shoulder. Further research is needed to evaluate whether a non-optimal serum lipid level is a cause, a related co-factor, or a result of primary frozen shoulder. Level of Evidence: Prognostic Level III. See Instructions for Authors for a complete description of levels of evidence....

Background: Certain metabolic factors have been proposed as risk factors for a posterosuperior rotator cuff tear. Although metabolic syndrome is of increasing concern in industrialized societies, little information exists regarding its association with posterosuperior rotator cuff tears. The purpose of this study was to determine the risk factors for an atraumatic posterosuperior rotator cuff tear, including metabolic factors and metabolic syndrome. Methods: This study involved 634 subjects (634 shoulders) drawn from a cohort of rural residents. Posterosuperior rotator cuff tear diagnoses were based on magnetic resonance imaging (MRI) findings. Logistic regression analysis was used to determine the odds ratios (ORs) and 95% confidence intervals (CIs) for various demographic, physical, and social factors, including age, sex, dominant-side involvement, body mass index (BMI), and participation in manual labor; the comorbidities of diabetes, hypertension, dyslipidemia, thyroid dysfunction, ipsilateral carpal tunnel syndrome, and metabolic syndrome; and the serum metabolic parameters of serum lipid profile, glycosylated hemoglobin A1c, and level of thyroid hormone. Two multivariable analyses were performed: the first excluded metabolic syndrome while including diabetes, hypertension, BMI, and hypo-high-density lipoproteinemia (hypo-HDLemia), and the second included metabolic syndrome while excluding the formerly included variables. Results: Age, BMI, waist circumference, dominant-side involvement, manual labor, diabetes, hypertension, metabolic syndrome, ipsilateral carpel tunnel syndrome, HDL (high-density lipoprotein), and hypo-HDLemia were significantly associated with posterosuperior rotator cuff tears in univariate analyses (p ≤ 0.035). In the first multivariable analysis, age (OR. 1.86 [95% CI, 1.47 to 2.35]), BMI (OR, 1.09 [95% CI, 1.02 to 1.18]), dominant-side involvement (OR, 2.04 [95% CI, 1.38 to 3.01]), manual labor (OR, 9.48 [95% CI, 5.13 to 17.51]), diabetes (OR, 3.38 [95% CI, 1.98 to 5.77]), and hypo-HDLemia (OR, 2.07 [95% CI, 1.30 to 3.29]) were significantly associated with posterosuperior rotator cuff tears (p ≤ 0.019). In the second multivariable analysis, age (OR, 1.85 [95% CI, 1.48 to 2.31]), dominant-side involvement (OR, 1.83 [95% CI, 1.26 to 2.67]), manual labor (OR, 7.71 [95% CI, 4.33 to 13.73]), and metabolic syndrome (OR, 1.98 [95% CI, 1.35 to 2.91]) were significantly associated with posterosuperior rotator cuff tears (p ≤ 0.002). Conclusions: The metabolic factors of diabetes, BMI, hypo-HDLemia, and metabolic syndrome were significant independent factors associated with the development of posterosuperior rotator cuff tears. Level of Evidence: Prognostic Level III. See Instructions for Authors for a complete description of levels of evidence.

Concern has recently arisen over the safety of local anesthetics used on human tissues. Aminoamide local anesthetics have cytotoxic effects on human rotator cuff tenofibroblasts. Controlled laboratory study. Cultured human rotator cuff tenofibroblasts were divided into control, phosphate buffered saline (PBS), and local anesthetic study groups; the PBS study group was further subdivided by pH level (pH 7.4, 6.0, and 4.4). The 6 local anesthetic subgroups (0.2% and 0.75% ropivacaine, 0.25% and 0.5% bupivacaine, and 1% and 2% lidocaine) were also studied at 10% dilutions of their original concentrations. Exposure times were 5, 10, 20, 40, or 60 minutes for the higher concentrations and 2, 6, 12, 24, 48, or 72 hours for the lower concentrations. Cell viability was evaluated through live, apoptotic, and necrotic cell rates using the annexin V–propidium iodide double-staining method. Intracellular reactive oxygen species (ROS) and the activity of mitogen-activated protein kinases (MAPKs) and caspase-3/7 were investigated. The control and PBS groups showed no significant differences in cell viability (P > .999). In the local anesthetic study groups, cell viability decreased significantly with increases in anesthetic concentrations (P < .001) and exposure times (P < .001), with the exception of the lidocaine subgroups, where this effect was masked by the very high cytotoxicity of even low concentrations. Among the studied local anesthetic subgroups, 0.2% ropivacaine was the least toxic. The levels of intracellular ROS of each local anesthetic subgroup also increased significantly (P < .05). The studied local anesthetics showed increases in the phosphorylation of extracellular signal–regulated kinase 1/2 (ERK1/2), c-Jun N-terminal kinase (JNK), and p38 as well as in levels of caspase-3/7 activity (P < .001). The cytotoxicity of the anesthetics studied to tenofibroblasts is dependent on exposure time and concentration. Of the evaluated anesthetics, ropivacaine is the least toxic in the clinically used concentration. The studied anesthetics induce tenofibroblast cell death, mediated by the increased production of ROS, by the increased activation of ERK1/2, JNK, and p38 and by the activation of caspase-3/7. This study identified the cytotoxic mechanisms of aminoamide local anesthetics acting on rotator cuff tenofibroblasts. The greatest margin of safety was found in lower anesthetic concentrations in general and more specifically in the use of ropivacaine.

Metabolic factors have been linked to tendinopathies, yet few studies have investigated the association between metabolic factors and lateral epicondylitis. To evaluate risk factors for lateral epicondylitis, including several metabolic factors. Case-control study; Level of evidence, 3. We evaluated 1 elbow in each of 937 volunteers from a rural region that employs many agricultural laborers. Each participant received a questionnaire, physical examinations, blood tests, simple radiographic evaluations of both elbows, magnetic resonance imaging of bilateral shoulders, and an electrophysiological study of bilateral upper extremities. Lateral epicondylitis was diagnosed using 3 criteria: (1) pain at the lateral aspect of the elbow, (2) point tenderness over the lateral epicondyle, and (3) pain during resistive wrist dorsiflexion with the elbow in full extension. Multivariable logistic regression analysis was used to calculate the odds ratios (ORs) and 95% CIs for various demographic, physical, and social factors, including age, sex, waist circumference, dominant-side involvement, smoking habit, alcohol intake, and participation in manual labor; the comorbidities of diabetes, hypertension, thyroid dysfunction, metabolic syndrome, ipsilateral biceps tendon injury, ipsilateral rotator cuff tear, and ipsilateral carpal tunnel syndrome; and the serologic parameters of serum lipid profile, glycosylated hemoglobin A1c, level of thyroid hormone, and high-sensitivity C-reactive protein. The prevalence of lateral epicondylitis was 26.1% (245/937 participants). According to the multivariable logistic regression analysis, female sex (OR, 2.47; 95% CI, 1.78-3.43), dominant-side involvement (OR, 3.21; 95% CI, 2.24-4.60), manual labor (OR, 2.25; 95% CI, 1.48-3.43), and ipsilateral rotator cuff tear (OR, 2.77; 95% CI, 1.96-3.91) were significantly associated with lateral epicondylitis (P < .001 for all). No metabolic factors were significantly associated with lateral epicondylitis. Female sex, dominant-side involvement, manual labor, and ipsilateral rotator cuff tear were found to be risk factors for lateral epicondylitis. The study results suggest that overuse activity is more strongly associated with lateral epicondylitis than are metabolic factors.

Degeneration of the rotator cuff tendon, which involves apoptosis of the tenofibroblasts, is one of the most common shoulder problems that can lead eventually to a full‐thickness rotator cuff tendon tear. The current authors evaluated both the ability of anthocyanins, which are powerful antioxidants, to reduce apoptosis in oxidation‐stressed rotator cuff tenofibroblasts, and the molecular mechanism for this antiapoptotic action. Anthocyanins demonstrated a dose‐dependent ability to inhibit H₂O₂‐induced apoptosis in cultured tenofibroblasts, as assessed by MTT assay and FACS analysis. H₂O₂ increased the phosphorylation of extracellular regulated kinase1/2 (ERK1/2) and of c‐Jun N‐terminal kinase (JNK) and the production of reactive oxygen species (ROS). In contrast, treatment with anthocyanins decreased this activation of ERK1/2 and JNK, as confirmed by Western blot analysis, and reduced the production of ROS, as verified by fluorescent microscopic and FACS analyses. These findings suggest that anthocyanins, by suppressing JNK, ERK1/2, and intracellular ROS production, have a concentration‐dependent antiapoptotic effect on rotator cuff tenofibroblasts exposed to an oxidative stressor, and may have therapeutic potential. © 2010 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 28:1162–1169, 2010