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Youth athletes are known to be at high risk of musculoskeletal (MSK) injuries. Children in developed countries are increasingly adopting a sedentary lifestyle. Although some risk factors related to sports activities have been reported, the effect of lifestyle (i.e. screen time behaviour) on MSK pain in youth athletes is not well known. This study aimed to examine the association of game playing and TV viewing with MSK pain among youth athletes. A self-administered questionnaire was mailed to youth athletes belonging to the Miyagi Amateur Sports Association. The final study population included 6,143 youth athletes (male, 71.1%; age range, 6-15 years). Multiple logistic regression analysis was used to examine the association of game playing and TV viewing behaviour with MSK pain. The point prevalence of MSK pain was 25.5%. The longest category of game playing time (≥3 h) was significantly associated with MSK pain as compared with the shortest category (<1 h) (odds ratio, 1.39; 95% confidence interval, 1.12-1.73, p = 0.003). There was no significant association between TV viewing time and MSK pain. These results suggest that game playing time might be an associated factor for MSK pain among youth athletes. [ABSTRACT FROM AUTHOR]

ABSTRACT Elastic fibers and proteoglycans are major components of the extracellular matrix and their changes have been reported in some pathological conditions. Further, recent studies have indicated that some glycosaminoglycans and proteoglycans inhibit elastic fiber assembly. The purpose of this study was to investigate changes of the elastic fibers and proteoglycans in the ligamentum flavum and analyze their relationships to thickening of the ligamentum flavum from lumbar spinal canal stenosis (LSCS). Ligamentum flavum samples were collected from 20 patients with LSCS (thickened flavum group) and 10 patients with lumbar disc herniation (non-thickened flavum group) as a control. Elastica-Masson staining and alcian blue staining were used to compare the relationship between the changes in the elastic fibers and proteoglycans. Gene and protein expressions of the elastic fibers and proteoglycans were analyzed by quantitative reverse transcription polymerase chain reaction and immunohistochemistry. Histological changes indicated that proteoglycans mainly increased on the dorsal side of the ligamentum flavum in accordance with the decreased elastic fibers in the thickened flavum group. The gene and protein expressions of fibrillin-2 and DANCE were significantly lower and decorin, lumican, osteoglycin, and versican were significantly higher in the thickened flavum group. Our study shows that elastic fibers decrease and proteoglycans increase in the thickened ligamentum flavum. Decreased gene expression of elastogenesis and disrupted elastic fiber assembly caused by increased proteoglycans may lead to a loss of elasticity in the thickened ligamentum flavum. Decreased elasticity may cause buckling of the tissue, which leads to thickening of the ligamentum flavum. © 2015 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 34:1241-1247, 2016. [ABSTRACT FROM AUTHOR]

Background: The Simple Shoulder Test (SST) is a widely used patient-reported outcome assessment. The purpose of this study was to develop and validate a Japanese version of the SST (SST-Jp)., Methods: A two-stage observational study was conducted to validate the cross-cultural adaptation of the SST. A total of 100 patients with shoulder disorders completed the SST-Jp; the Disability of Arm, Shoulder, and Hand assessment; and the Medical Outcomes Short-Form 36 (SF-36) at an initial visit. Thirty-four of the patients repeated the SST-Jp one week after the first examination. The test-retest reliability was quantified using the interclass correlation coefficient, and Cronbach's alpha (α) was calculated to assess internal consistency. Construct validity was assessed using Spearman's rank correlation coefficient., Results: The internal consistency of the SST-Jp was very high (α = 0.826). The interclass correlation coefficient of the SST-Jp was also high (0.859). There was a strong, positive correlation between the Disability of Arm, Shoulder, and Hand and the SST-Jp (r = 0.717, P < .001). The SST-Jp was significantly correlated with most of the SF-36 subscales. The correlations of the SST-Jp with physical subscales of the SF-36 were stronger than those with the other subscales., Conclusions: The SST-Jp was found to be a valid and reliable measurement for shoulder joint pain and function assessment among the Japanese population., (© 2020 The Author(s).)

Context: Range of motion (ROM) in the glenohumeral joint decreases with age in healthy subjects; however, the underlying mechanism remains unclear. The process of aging of the joint capsule, including the coracohumeral ligament (CHL), could affect ROM limitation., Objective: This study investigated correlations between elasticity of the CHL, evaluated by means of shear-wave elastography, and age, side dominance, and ROM in healthy individuals., Design: Experimental study., Setting: Laboratory., Subjects: Eighty-four healthy volunteers (39 men and 45 women, mean age: 42.6 y) were included., Main Outcome Measures: Subjects were divided into 3 age groups: younger (20-39 y), middle (40-59 y), and older (≥60 y) age groups. With participants in the supine position, CHL elasticity in both shoulders was evaluated in both neutral and 30° external rotation, with arms at the sides. ROM, including forward flexion, lateral elevation, external rotation, 90° abduction with external rotation, and hand behind the back were measured with participants in the standing position., Results: The CHL elastic modulus was higher in the older group than in the younger group in the neutral (78.4 kPa [SD: 37.1] and 56.6 kPa [SD: 31.7], respectively) and 30° external rotation positions (135.5 kPa [SD: 63.5] and 71.4 kPa [SD: 32.2], respectively). Negative correlations were found between the CHL elastic modulus and ROM in terms of 30° external rotation and both external rotation (R = -.59, P = .02) and 90° abduction with external rotation (R = -.71, P = .003) in the older group, with correlation coefficients increasing with age., Conclusions: Significant correlations were identified between CHL elasticity and ROM in both external rotation and 90° abduction with external rotation with increasing age. Decreased CHL elasticity was strongly associated with decreased shoulder ROM in middle-aged and older individuals.

Skeletal muscle regeneration after injury is a complex process involving interactions between inflammatory microenvironments and satellite cells. Interleukin (IL)-1 is a key mediator of inflammatory responses and exerts pleiotropic impacts on various cell types. Thus, we aimed to investigate the role of IL-1 during skeletal muscle regeneration. We herein show that IL-1α/β-double knockout (IL-1KO) mice exhibit delayed muscle regeneration after cardiotoxin (CTX) injection, characterized by delayed infiltrations of immune cells accompanied by suppressed local production of proinflammatory factors including IL-6 and delayed increase of paired box 7 (PAX7)-positive satellite cells postinjury compared with those of wild-type (WT) mice. A series of in vitro experiments using satellite cells obtained from the IL-1KO mice unexpectedly revealed that IL-1KO myoblasts have impairments in terms of both proliferation and differentiation, both of which were reversed by exogenous IL-1β administration in culture. Intriguingly, the delay in myogenesis was not attributable to the myogenic transcriptional program since MyoD and myogenin were highly upregulated in IL-1KO cells, instead appearing, at least in part, to be due to dysregulation of cellular fusion events, possibly resulting from aberrant actin regulatory systems. We conclude that IL-1 plays a positive role in muscle regeneration by coordinating the initial interactions among inflammatory microenvironments and satellite cells. Our findings also provide compelling evidence that IL-1 is intimately engaged in regulating the fundamental function of myocytes.

Arthroscopic pancapsular release has been recommended for recalcitrant frozen shoulder, but regaining range of motion has not been sufficient compared with the unaffected side. There is no consensus about the reasons for these remaining restrictions in range of motion, but residual capsular or connective tissue must be considered a candidate. A thickened coracohumeral ligament at the rotator interval has been reported as one of the most specific manifestations of frozen shoulder. It covers wider portions of the subscapularis tendon, supraspinatus tendon, and infraspinatus tendon than previously reported. We describe an arthroscopic surgical technique for the release of the entire coracohumeral ligament including the subscapularis and supraspinatus portions and the release of the inferior and posterior parts of the glenohumeral ligament using the 7-o'clock portal. These procedures are essential and reliable methods to release the entire joint capsule to regain full range of motion for frozen shoulder.

Purpose: To elucidate preventive effects of high molecular weight hyaluronan (HMWHA) on the joint capsule of immobilized knees in rats., Materials and Methods: Unilateral knee joints of rats were immobilized with an internal fixator. Either 50 μl of HMWHA (Im-HA group) or 50 μl of saline (control group) was administered intra-articularly once a week after surgery. Sagittal sections were prepared from the medial midcondylar region of the knee joints and assessed by histological, histomorphometric, and immunohistochemical methods. Gene expressions related to inflammation, fibrotic conditions, and hypoxia were evaluated by quantitative reverse transcription polymerase chain reaction (qRT-PCR). Tissue elasticity of the capsule from both groups was examined using a scanning acoustic microscope (SAM)., Results: CD68 positive cells decreased in adhesion areas of the synovial membrane after 1 week in both groups. The length of the superficial layer in the synovial membrane of the Im-HA group was significantly longer than those in the control group over a period of 4 to 8 weeks with significantly small numbers of CD68 positive cells. The gene expressions of IL-6, IL-1β, TGF-β, CTGF, COL1a1, COL3a1, SPARC, and HIF1-α were significantly lower in the Im-HA group compared to those in the control group. The sound speed of the anterior and posterior synovial membrane increased significantly (a reduction in elasticity) in the control group compared to those in the Im-HA group during weeks 1 to 4., Conclusions: This study demonstrated that HMWHA injections suppressed inflammatory, fibrotic, and hypoxic conditions observed in the immobilized joint capsule.