Hitoshi Shitara

Prevalence and risk factors of a rotator cuff tear in the general population.

BACKGROUND Little information is available about the epidemiology of rotator cuff tears in a population-based study. The purpose of this study was to elucidate the true prevalence of rotator cuff tears regardless of the presence or absence of symptoms in the general population and to assess the relationship between tears and their backgrounds. MATERIAL AND METHODS A medical check-up was conducted for residents of a mountain village in Japan. The subjects consisted of 683 people (total of 1,366 shoulders), including 229 males and 454 females with a mean age of 57.9 years (range, 22-87). We examined their background factors, physical examinations and ultrasonographic examinations on both shoulders. RESULTS Rotator cuff tears were present in 20.7% and the prevalence increased with age. Thirty-six percent of the subjects with current symptoms had rotator cuff tears, while 16.9% of the subjects without symptoms also had rotator cuff tears. Rotator cuff tears in the general population were most commonly associated with elderly patients, males, affected the dominant arm, engaged in heavy labor, having a history of trauma, positive for impingement sign, showed lesser active forward elevation and weaker muscle strength in abduction and external rotation. A logistic regression analysis revealed the risk factors for a rotator cuff tear to be a history of trauma, dominant arm and age. CONCLUSION 20.7% of 1,366 shoulders had full-thickness rotator cuff tears in the general population. The risk factors for rotator cuff tear included a history of trauma, dominant arm and age. LEVEL OF EVIDENCE Level 3.

Time course and spatial distribution of fMRI signal changes during single-pulse transcranial magnetic stimulation to the primary motor cortex.

Simultaneous transcranial magnetic stimulation (TMS) and functional magnetic resonance imaging (fMRI) may advance the understanding of neurophysiological mechanisms of TMS. However, it remains unclear if TMS induces fMRI signal changes consistent with the standard hemodynamic response function (HRF) in both local and remote regions. To address this issue, we delivered single-pulse TMS to the left M1 during simultaneous recoding of electromyography and time-resolved fMRI in 36 healthy participants. First, we examined the time-course of fMRI signals during supra- and subthreshold single-pulse TMS in comparison with those during voluntary right hand movement and electrical stimulation to the right median nerve (MNS). All conditions yielded comparable time-courses of fMRI signals, showing that HRF would generally provide reasonable estimates for TMS-evoked activity in the motor areas. However, a clear undershoot following the signal peak was observed only during subthreshold TMS in the left M1, suggesting a small but meaningful difference between the locally and remotely TMS-evoked activities. Second, we compared the spatial distribution of activity across the conditions. Suprathreshold TMS-evoked activity overlapped not only with voluntary movement-related activity but also partially with MNS-induced activity, yielding overlapped areas of activity around the stimulated M1. The present study has provided the first experimental evidence that motor area activity during suprathreshold TMS likely includes activity for processing of muscle afferents. A method should be developed to control the effects of muscle afferents for fair interpretation of TMS-induced motor area activity during suprathreshold TMS to M1.

Movement and afferent representations in human motor areas: a simultaneous neuroimaging and transcranial magnetic/peripheral nerve-stimulation study

Neuroimaging combined with transcranial magnetic stimulation (TMS) to primary motor cortex (M1) is an emerging technique that can examine motor-system functionality through evoked activity. However, because sensory afferents from twitching muscles are widely represented in motor areas the amount of evoked activity directly resulting from TMS remains unclear. We delivered suprathreshold TMS to left M1 or gave electrical right median nerve stimulation (MNS) in 18 healthy volunteers while simultaneously conducting functional magnetic resonance imaging and monitoring with electromyography (EMG). We examined in detail the localization of TMS-, muscle afferent- and superficial afferent-induced activity in M1 subdivisions. Muscle afferent- and TMS-evoked activity occurred mainly in rostral M1, while superficial afferents generated a slightly different activation distribution. In 12 participants who yielded quantifiable EMG, differences in brain activity ascribed to differences in movement-size were adjusted using integrated information from the EMGs. Sensory components only explained 10–20% of the suprathreshold TMS-induced activity, indicating that locally and remotely evoked activity in motor areas mostly resulted from the recruitment of neural and synaptic activity. The present study appears to justify the use of fMRI combined with suprathreshold TMS to M1 for evoked motor network imaging.

The impact of faulty posture on rotator cuff tears with and without symptoms

HYPOTHESIS We hypothesized that the prevalence of rotator cuff tears would be higher among individuals with poor posture, regardless of the presence of symptoms. METHODS The study initially comprised 525 residents of a mountain village who participated in an annual health check. Participants completed a background questionnaire, and physical examinations were performed to evaluate shoulder function. Ultrasonographic examinations were also performed to identify rotator cuff tears, and participants were grouped according to the presence or absence of tears. Posture was classified by 2 observers into 4 types according to the classification of Kendall, as follows: ideal alignment, kyphotic-lordotic posture, flat-back posture, and sway-back posture. Univariate analyses were performed to compare differences in background characteristics between groups, then multivariate analysis was performed to identify those factors associated with rotator cuff tears. RESULTS Final analysis was performed for 379 participants (135 men, 244 women; mean age, 62.0 years; range, 31-94 years) showing the same posture classification from both observers. Of these, 93 (24.5%) showed rotator cuff tear in one shoulder and 45 (11.9%) showed tears in both. Prevalence of rotator cuff tears was 2.9% with ideal alignment, 65.8% with kyphotic-lordotic posture, 54.3% with flat-back posture, and 48.9% with sway-back posture. Logistic regression analysis identified increased age, abnormal posture, and past pain as factors associated with rotator cuff tears. CONCLUSIONS Postural abnormality represented an independent predictor of both symptomatic and asymptomatic rotator cuff tears. These results may help define preventive measures for rotator cuff tears and in design ing rehabilitation therapies for shoulder disease.

The morphologic change of the ulnar collateral ligament of elbow in high school baseball pitchers, with and without symptoms, by sonography

BACKGROUND Few reports in the literature relate morphologic changes of the ulnar collateral ligament (UCL) to prior elbow symptoms. This study used ultrasonography (US) to assess the ulnohumeral joint space width, with and without stress, and elucidate morphologic changes of the UCL of the elbow in high school pitchers with and without a history of elbow symptoms. METHODS Each of 122 high school baseball pitchers who underwent US of the medial aspect of both elbows completed a self-administered questionnaire related to the self-satisfaction score (0-100) for pitching performance and throwing-related elbow joint pain sustained during the prior 3 years. We conducted gravity stress US elbow examination with 30° of flexion with and without valgus stress. Comparisons of the UCL thickness and ulnohumeral joint space width, with and without valgus stress, were made among the 122 high school pitchers with and without a history of elbow symptoms. RESULTS Pitchers with an elbow symptom history exhibited a greater difference between the UCL thickness on the throwing side than those with no elbow symptom history (P = .0013). A negative significant association was found between UCL thickness on the pitching side and the self-evaluation score for pitching performance (r = -0.20, P = .04). CONCLUSIONS US assessment demonstrated that the UCL in the dominant side with elbow symptom history was thicker than that with no elbow symptom history. The UCL thickness might reflect the prior pitching condition of high school baseball pitchers.

Relationship Between Grip, Pinch Strengths and Anthropometric Variables, Types of Pitch Throwing Among Japanese High School Baseball Pitchers

Background: Grip and pinch strength are crucially important attributes and standard parameters related to the functional integrity of the hand. It seems significant to investigate normative data for grip and pinch strength of baseball players to evaluate their performance and condition. Nevertheless, few reports have explained the association between grip and pinch strength and anthropometric variables and types of pitch throwing for baseball pitchers. Objectives: The aim of this study was to measure and evaluate clinical normative data for grip and tip, key, palmar pinch strength and to assess the relationship between these data and anthropometric variables and types of pitch throwing among Japanese high-school baseball pitchers. Materials and Methods: One hundred-thirty three healthy high school baseball pitchers were examined and had completed a self-administered questionnaire including items related to age, hand dominance, throwing ratio of type of pitch. A digital dynamometer was used to measure grip strength and a pinch gauge to measure tip, key and palmer pinch in both dominant and nondominant side. Body composition was measured by the multi frequency segmental body composition analyzer. Results: Grip strength and tip and palmer pinch strength in dominant side were statistically greater than them in nondominant side (P < 0.05). There were significant associations between grip strength and height (r = 0.33, P < 0.001), body mass (r = 0.50, P < 0.001), BMI (r = 0.37, P < 0.001), muscle mass of upper extremity (r = 0.56, P < 0.001), fat free mass (r = 0.57, P < 0.001), fat mass (r = 0.22, P < 0.05) in dominant side. A stepwise multiple regression analysis revealed that fat free mass and tip, palmer, key pinch strength were predictors of grip strength in dominant side. No statistical significant correlations were found between the throwing ratio of types of pitches thrown and grip strength and tip, key, palmar pinch strength. Conclusions: Our result provides normative values and evidences for grip and pinch strengths in high school baseball pitchers.

A Clinical and Ultrasonographic Study of Risk Factors for Elbow Injury in Young Baseball Players

Purpose. To determine the risk factors for elbow injury and its association with glenohumeral internal rotation deficit among young baseball players. Methods. 229 baseball players aged 9 to 14 (mean, 11) years completed a self-administered questionnaire with items related to years of playing baseball, hours of training per weekday, days of training per week, and past and present experience of elbow pain. Two orthopaedic surgeons measured the range of motion of both shoulders and elbows. Another 2 orthopaedic surgeons performed ultrasonography to detect any elbow abnormality such as fragmentation of the medial epicondylar apophysis and osteochondritis dissecans of the capitellum. Using univariate and multivariable analyses, participants with or without elbow abnormality were compared to determine the risk factors for elbow abnormality. Results. Elbow abnormality was detected in 100 of the participants and comprised osteochondritis dissecans of the capitellum (n=18) and fragmentation of the medial epicondylar apophysis (n=82). Elbow abnormality was associated with being a pitcher, past and present experience of elbow pain, loss of elbow extension, and the side-to-side internal rotation difference. The 100 participants with elbow abnormality were stratified into symptomatic (n=57) or asymptomatic (n=43) of elbow pain. Those with elbow abnormality and elbow pain was associated with being a pitcher. Conclusion. Being a pitcher was a risk factor for both elbow abnormality and elbow pain. Nonetheless, 43% of baseball players with elbow abnormality were asymptomatic. The use of ultrasonography was effective in detecting elbow abnormality and enabling early treatment.

Compensatory hypertrophy of the teres minor muscle after large rotator cuff tear model in adult male rat

BACKGROUND Rotator cuff tear (RCT) is a common musculoskeletal disorder in the elderly. The large RCT is often irreparable due to the retraction and degeneration of the rotator cuff muscle. The integrity of the teres minor (TM) muscle is thought to affect postoperative functional recovery in some surgical treatments. Hypertrophy of the TM is found in some patients with large RCTs; however, the process underlying this hypertrophy is still unclear. The objective of this study was to determine if compensatory hypertrophy of the TM muscle occurs in a large RCT rat model. METHODS Twelve Wistar rats underwent transection of the suprascapular nerve and the supraspinatus and infraspinatus tendons in the left shoulder. The rats were euthanized 4 weeks after the surgery, and the cuff muscles were collected and weighed. The cross-sectional area and the involvement of Akt/mammalian target of rapamycin (mTOR) signaling were examined in the remaining TM muscle. RESULTS The weight and cross-sectional area of the TM muscle was higher in the operated-on side than in the control side. The phosphorylated Akt/Akt protein ratio was not significantly different between these sides. The phosphorylated-mTOR/mTOR protein ratio was significantly higher on the operated-on side. CONCLUSION Transection of the suprascapular nerve and the supraspinatus and infraspinatus tendons activates mTOR signaling in the TM muscle, which results in muscle hypertrophy. The Akt-signaling pathway may not be involved in this process. Nevertheless, activation of mTOR signaling in the TM muscle after RCT may be an effective therapeutic target of a large RCT.

The Neural Correlates of Shoulder Apprehension: A Functional MRI Study.

Although shoulder apprehension is an established clinical finding and is important for the prevention of shoulder dislocation, how this subjective perception is evoked remains unclear. We elucidated the functional neuroplasticity associated with apprehension in patients with recurrent anterior shoulder instability (RSI) using functional magnetic resonance imaging (fMRI). Twelve healthy volunteers and 14 patients with right-sided RSI performed a motor imagery task and a passive shoulder motion task. Brain activity was compared between healthy participants and those with RSI and was correlated with the apprehension intensity reported by participants after each task. Compared to healthy volunteers, participants with RSI exhibited decreased brain activity in the motor network, but increased activity in the hippocampus and amygdala. During the passive motion task, participants with RSI exhibited decreased activity in the left premotor and primary motor/somatosensory areas. Furthermore, brain activity was correlated with apprehension intensity in the left amygdala and left thalamus during the motor imagery task (memory-induced), while a correlation between apprehension intensity and brain activity was found in the left prefrontal cortex during the passive motion task (instability-induced). Our findings provide insight into the pathophysiology of RSI by identifying its associated neural alterations. We elucidated that shoulder apprehension was induced by two different factors, namely instability and memory.

Possible involvement of IGF‐1 signaling on compensatory growth of the infraspinatus muscle induced by the supraspinatus tendon detachment of rat shoulder

A rotator cuff tear (RCT) is a common musculoskeletal disorder among elderly people. RCT is often treated conservatively for functional compensation by the remaining muscles. However, the mode of such compensation after RCT has not yet been fully understood. Here, we used the RCT rat model to investigate the compensatory process in the remaining muscles. The involvement of insulin‐like growth factor 1 (IGF‐1)/Akt signaling which potentially contributes to the muscle growth was also examined. The RCT made by transecting the supraspinatus (SSP) tendon resulted in atrophy of the SSP muscle. The remaining infraspinatus (ISP) muscle weight increased rapidly after a transient decrease (3 days), which could be induced by posttraumatic immobilization. The IGF‐1 mRNA levels increased transiently at 7 days followed by a gradual increase thereafter in the ISP muscle, and those of IGF‐1 receptor mRNA significantly increased after 3 days. IGF‐1 protein levels biphasically increased (3 and 14 days), then gradually decreased thereafter. The IGF‐1 protein levels tended to show a negative correlation with IGF‐1 mRNA levels. These levels also showed a negative correlation with the ISP muscle weight, indicating that the increase in IGF‐1 secretion may contribute to the ISP muscle growth. The pAkt/Akt protein ratio decreased transiently by 14 days, but recovered later. The IGF‐1 protein levels were negatively correlated with the pAkt/Akt ratio. These results indicate that transection of the SSP tendon activates IGF‐1/Akt signaling in the remaining ISP muscle for structural compensation. Thus, the remaining muscles after RCT can be a target for rehabilitation through the activation of IGF‐1/Akt signaling.