Yoshiaki Itoigawa

Molecular mechanism of fatty degeneration in rotator cuff muscle with tendon rupture

Fatty degeneration often occurs in rotator cuff muscle with tendon rupture. However, the molecular mechanism underlying this change has not been fully clarified yet. We investigated the gene expression of Wnt10b and adipogenic marker gene, PPARγ and C/EBPα in C2C12 myogenic cell line under inhibition of Wnt10b by adipogenic induction medium, isobutylmethylxanthine, dexamethasone, and insulin (MDI). The role of Wnt‐signal was confirmed by adding Lithium chloride (LiCl), which mimics Wnt signaling to the cultured cell with MDI. We also assessed the expression profiles of same genes in the rat rotator cuff tear model in vivo. MDI induced Oil red‐O staining positive adipocytes and upregulated PPARγ and C/EBPα expression. LiCl inhibited adipogenic induction of MDI. Rotator cuff muscle with tendon rupture showed positive staining for Oil red‐O. Real‐time polymerase chain reaction analyses revealed decreased expression of Wnt10b followed by increased PPARγ and C/EBPα gene expression in the supraspinatus muscle. Fatty degeneration and its molecular events were remarkably seen in the distal one‐third of the detached supraspinatus muscle versus control. Wnt signaling may regulate adipogenic differentiation both in the myoblasts in vitro and the muscle in vivo. Our results indicate that the reduction of Wnt10b in muscle with a rotator cuff tear is a key signal in fatty degeneration of the muscle.

Anatomical and functional segments of the deltoid muscle

Previous studies showed that the insertion of the intramuscular tendons of the deltoid muscle formed three discrete lines. The purpose of the present study was to establish a new dividing method of the deltoid muscle into various anatomical segments based on the distribution of the intramuscular tendons with their insertions (anatomical study). We further hoped to clarify the relationship between the anatomical segments and their activity pattern assessed by positron emission tomography with [18F]‐2‐fluoro‐deoxyglucose (FDG–PET; PET study). Sixty cadaveric shoulders were investigated in the anatomical study. Three tendinous insertions of the deltoid muscle to the humerus were identified. Then, the intramuscular tendons were traced from their humeral insertions to the proximal muscular origins. The extent of each anatomical segment of the muscle including its origin and insertion was determined through careful dissection. Six healthy volunteers were examined using FDG–PET for the PET study. PET images were obtained after exercise of elevation in the scapular plane. On the PET images, margins of each anatomical segment of the deltoid muscle were determined using magnetic resonance images. Then, the standardized uptake value in each segment was calculated to quantify its activity. The anatomical study demonstrated that the deltoid muscle was divided into seven segments based on the distribution of its intramuscular tendons. The PET study revealed that the intake of FDG was not uniform in the deltoid muscle. The area with high FDG intake corresponded well to the individual muscular segments separated by the intramuscular tendons. We conclude that the deltoid muscle has seven anatomical segments, which seem to represent the functional units of this muscle.

Contribution of oxidative stress to the degeneration of rotator cuff entheses.

BACKGROUND Rotator cuff degeneration is one of the multiple factors that lead to rotator cuff tears; however, the precise mechanism of such degeneration still remains unclear. In this study, we investigated the supraspinatus tendon enthesis to clarify the link between rotator cuff degeneration and oxidative stress in antioxidant enzyme superoxide dismutase 1 (Sod1)-deficient mice (Sod1(-/-)). METHODS The supraspinatus tendon and humeral head were isolated and fixed to prepare histologic sections from wild-type and Sod1(-/-) male mice at 20 weeks of age. Hematoxylin-eosin staining was performed to assess the histomorphologic structure. To investigate the collagen fibers, we examined spatially aligned collagen fibers using a polarizing microscope and assessed the amount of collagen using immunohistochemical staining. To analyze the tissue elasticity, we measured the tissue acoustic properties using scanning acoustic microscopy. RESULTS The Sod1(-/-) mice showed histologic changes, such as a misaligned 4-layered structure and fragmented tidemark, in the enthesis. Sod1 loss also decreased the amount of brightly diffracted light and type I collagen, indicating collagen downregulation. The scanning acoustic microscopy analysis showed that the speed and attenuation of sound were increased in the nonmineralized fibrocartilage of the Sod1(-/-) mice, suggesting decreased mechanical properties in the supraspinatus enthesis. CONCLUSION Sod1 deficiency-induced degeneration is associated with impaired elasticity in the supraspinatus tendon enthesis, recapitulating human rotator cuff degeneration. These results suggest that intracellular oxidative stress contributes to the degeneration of rotator cuff entheses.

Is Protecting the Healing Ligament Beneficial After Immobilization in External Rotation for an Initial Shoulder Dislocation

Background: Immobilization in external rotation is one of the treatment options for an initial dislocation of the shoulder. However, it remains unclear how long it takes for a Bankart lesion to heal. Hypothesis: Protection of a healing Bankart lesion from stretching would promote the healing process and decrease the recurrence rate after an initial dislocation of the shoulder. Study Design: Randomized controlled trial; Level of evidence, 2. Methods: This was a multicenter, prospective randomized study. Between January 2005 and August 2009, 109 patients (71 male and 38 female; mean age, 30 years) with an initial traumatic dislocation of the shoulder were enrolled. After 3 weeks of immobilization in external rotation, a shoulder motion restriction band designed to avoid stretching the anteroinferior shoulder capsule was used for 0 weeks (36 patients), 3 weeks (37 patients), or 6 weeks (36 patients). After using the band, patients were allowed to use their shoulders freely, but they were advised to avoid vigorous sport activities for at least 3 months after the injury. Any recurrent dislocation and return to sports were assessed at 2-year follow-up. Results: Of 109 patients, 90 were followed up for 2 years. The compliance rates were 60% to 72% among the groups (P = .54). The recurrence rate of dislocation was 28% in the 0-week group, 33% in the 3-week group, and 32% in the 6-week group (P = .88) according to the intention-to-treat analysis, and they were a respective 24%, 28%, and 27% according to the per-protocol analysis (P = .95). Based on the sport activity level, the recurrence rates for patients involved in contact sports (7/15, 47%) and those involved in noncontact sports (19/51, 37%) were significantly higher than for those not involved in sport activities (2/24, 8.3%) (P = .0076). Among the 3 groups, there were no significant differences in the recurrence rates. There was no significant difference in the rate of return to sports (P = .39). Conclusion: No difference in the recurrence rate was seen with the use of a shoulder motion restriction band after 3 weeks of immobilization in external rotation after an initial dislocation of the shoulder.

Hypoxia induces adipogenic differentitation of myoblastic cell lines

Muscle atrophy usually accompanies fat accumulation in the muscle. In such atrophic conditions as back muscles of kyphotic spine and the rotator cuff muscles with torn tendons, blood flow might be diminished. It is known that hypoxia causes trans-differentiation of mesenchymal stem cells derived from bone marrow into adipocytes. However, it has not been elucidated yet if hypoxia turned myoblasts into adipocytes. We investigated adipogenesis in C2C12 and G8 murine myogenic cell line treated by hypoxia. Cells were also treated with the cocktail of insulin, dexamethasone and IBMX (MDI), which has been known to inhibit Wnt signaling and promote adipogenesis. Adipogenic differentiation was seen in both hypoxia and MDI. Adipogenic marker gene expression was assessed in C2C12. CCAAT/enhancer-binding protein (C/EBP) beta, alpha and peroxisome proliferator activating receptor (PPAR) gamma were increased by both hypoxia and MDI. The expression profile of Wnt10b was different between hypoxia and MDI. The mechanism for adipogenesis of myoblasts in hypoxia might be regulated by different mechanism than the modification of Wnt signaling.

Anatomy of the capsulolabral complex and rotator interval related to glenohumeral instability

AbstractThe glenohumeral joint with instability is a common diagnosis that often requires surgery. The aim of this review was to present an overview of the anatomy of the glenohumeral joint with emphasis on instability based on the current literature and to describe the detailed anatomy and anatomical variants of the glenohumeral joint associated with anterior and posterior shoulder instability. A review was performed using PubMed/MEDLINE using key words: Search terms were “glenohumeral”, “shoulder instability”, “cadaver”, “rotator interval”, “anatomy”, and “anatomical study”. During the last decade, the interest in both arthroscopic repair techniques and surgical anatomy of the glenohumeral ligament (superior, middle, and inferior), labrum, and rotator interval has increased. Understanding of the rotator interval and attachment of the inferior glenohumeral ligament on the glenoid or humeral head have evolved significantly. The knowledge of the detailed anatomy and anatomical variations is essential for the surgeon in order to understand the pathology, make a correct diagnosis of instability, and select proper treatment options. Proper understanding of anatomical variants can help us avoid misdiagnosis. Level of evidence V.

Application of shear wave elastography for the gastrocnemius medial head to tennis leg.

Muscle strain of the gastrocnemius medial head mainly occurs at the musculotendinous junction (MTJ), and stiffness is a risk factor. Shear wave elastography (SWE) measures elasticity by determining the propagation velocity. The aim of this study was to measure the elasticity of the normal muscle and aponeurosis in the MTJ of the gastrocnemius medial head using SWE, thus obtaining information relevant to muscle strain at this point. Forty‐one volunteers (82 legs) were recruited and the gastrocnemius medial heads were examined at four points: three on the aponeurosis, namely at the center of the MTJ (Central), 10 mm proximal to it (Proximal) and 10 mm distal to it (Distal); and at one on the muscle belly (Muscle). The measurements were compared among the points, between males and females, and between younger and middle‐aged subjects. Correlations between the elastic modulus and age were also examined. The elastic moduli at Proximal, Central, Distal, and Muscle were 2.82 ± 0.53 m/s, 3.43 ± 0.83 m/s, 4.83 ± 1.56 m/s, and 2.25 ± 0.43 m/s, respectively. These values differed significantly among the points of the aponeurosis, Distal having the highest modulus followed by Central. The elastic moduli were significantly greater in males than females at Distal and Muscle and in younger subjects than middle‐aged subjects at Muscle. No significant correlations between elastic modulus and age were observed for any point. SWE could be a feasible method for quantifying the elasticity of muscle and aponeurosis in the MTJ of the gastrocnemius medial head. Clin. Anat. 30:114–119, 2017.

Tackler’s head position relative to the ball carrier is highly correlated with head and neck injuries in rugby

Objectives To characterise the tackler’s head position during one-on-one tackling in rugby and to determine the incidence of head, neck and shoulder injuries through analysis of game videos, injury records and a questionnaire completed by the tacklers themselves. Methods We randomly selected 28 game videos featuring two university teams in competitions held in 2015 and 2016. Tackles were categorised according to tackler’s head position. The ‘pre-contact phase’ was defined; its duration and the number of steps taken by the ball carrier prior to a tackle were evaluated. Results In total, 3970 tackles, including 317 (8.0%) with the tackler’s head incorrectly positioned (ie, in front of the ball carrier) were examined. Thirty-two head, neck or shoulder injuries occurred for an injury incidence of 0.8% (32/3970). The incidence of injury in tackles with incorrect head positioning was 69.4/1000 tackles; the injury incidence with correct head positioning (ie, behind or to one side of the ball carrier) was 2.7/1000 tackles. Concussions, neck injuries, ‘stingers’ and nasal fractures occurred significantly more often during tackles with incorrect head positioning than during tackles with correct head positioning. Significantly fewer steps were taken before tackles with incorrect head positioning that resulted in injury than before tackles that did not result in injury. Conclusion Tackling with incorrect head position relative to the ball carrier resulted in a significantly higher incidence of concussions, neck injuries, stingers and nasal fractures than tackling with correct head position. Tackles with shorter duration and distance before contact resulted in more injuries.

Humeral head osteonecrosis in an adolescent amateur swimming athlete: a case report

Osteonecrosis of the humeral head in an adolescent without clear pathogenesis has not been reported in the literature. In this case report, we present such a case of humeral head osteonecrosis in a 15-year-old adolescent. The lesion was located at the subchondral area of the medial part of the humeral head with characteristic appearances on MRI. The shoulder was immobilized in a sling until the pain disappeared, and the patient was told to refrain any kind of sport activities. Bone remodeling was noted five months after the first visit, and it took 2 years for the lesion to be totally healed.

A new technique of surgical planning for anterior cruciate ligament reconstruction

There is currently no method to quantify the quality of the harvested graft before anterior cruciate ligament (ACL) reconstruction. The purpose of this study was to explore a method for measuring stiffness of the normal tendon of the semitendinosus muscle using shear wave elastography (SWE). Our investigation comprised two steps. First, we determined orientation of the semitendinosus tendon fibers in 20 lower legs of embalmed cadavers. Second, we investigated the feasibility of quantifying stiffness of the normal semitendinosus tendon by SWE in 24 subjects (48 legs: 24 male and 24 female subjects) in vivo. Measured values were compared between male and female subjects. The point at the intersection of the semitendinosus tendon with the axial section through the center of the patella mostly was the middle of the semitendinosus tendon in the cadavers. The SWE modulus in all of the subjects could be measured on this point in vivo. The SWE modulus of males and females were 474.0 ± 71.9 kPa and 396.9 ± 104.5 kPa, respectively. The SWE modulus of males was significantly larger than that of females (P < 0.01). This study demonstrates that stiffness of the tendon of the semitendinosus muscle can be measured by SWE. It also shows that tendon of the semitendinosus muscle in males is stiffer than in females. Clin. Anat. 31:404–408, 2018.