Investigating the relationship between quantitative-based ultrasound and MRI estimations of rotator cuff fatty infiltration.

INTRODUCTION: Fatty infiltration (FI) of the rotator cuff has important clinical implications. Quantitatively estimating FI using ultrasound (US) has considerable benefits for assessing FI in a non-invasive, accessible manner. This research investigated whether FI of the supraspinatus (SS) and infraspinatus (IS), estimated using US was related to intramuscular fat fractions measured from magnetic resonance images (MRI). METHODS: Data from 12 healthy young adult participants were used for analysis. US images of the SS and IS were captured using multiple transducer placement techniques from which echogenicity of the muscle region was quantified. Shoulder MRI were captured from which SS and IS were manually segmented and intramuscular fat fractions calculated. Six upper limb strength exertions were performed, resisted by a hand dynamometer. RESULTS: IS and SS echogenicity explained a significant amount of variance in MRI fat fractions for certain body positions and transducer techniques. Echogenicity agreement was higher for IS than SS. Significant relationships were identified between strength exertions and both echogenicity and MRI muscle volume, but not MRI fat fraction. CONCLUSIONS: This research provides preliminary evidence showing that quantitative-based US methods can be used to estimate MRI calculated fat fractions for the rotator cuff.

Shoulder muscular activity in individuals with low back pain and spinal cord injury during seated manual load transfer tasks.

This study aimed to compare the activity of four shoulder muscles in individuals with low back pain (LBP), spinal cord injuries (SCI) and a control group, during one-handed load transfer trials. Nine individuals with minimum one-year of LBP, eleven with thoracic/lumbar SCI and nine healthy controls participated in this study. The activations of anterior deltoid, upper trapezius, infraspinatus and pectoralis major were recorded by surface EMG during one-handed transferring of a cylinder from a home shelve to six spatially distributed target shelves. The integrated EMG values were compared using repeated measure ANOVA. Both LBPs and SCIs had higher anterior deltoid activation and LBPs required more upper trapezius activation than controls (p < 0.05). The spatial position of the targets also significantly influenced demands for these two muscles. The anterior deltoid and upper trapezius in LBP and SCI individuals are under higher demand during occupational load transfer tasks. Practitioner Summary: This study aimed to compare the activation of four shoulder muscles in individuals with low back pain, spinal cord injuries and healthy condition. EMG analysis showed that the injured groups required more upper trapezius and anterior deltoid activation during load transfer tasks, which may predispose them to muscle overexertion.

Electromyographic activity in the shoulder musculature during resistance training exercises of the ipsilateral upper limb while wearing a shoulder orthosis.

BACKGROUND: Resistance training is usually postponed until 3 months after rotator cuff surgery to prevent the damaging effects of high muscle stress on the repaired tendon. After upper limb immobilization, noninjured muscles as well as the repaired muscles are affected by long-term inactivity. Exercises with minimal cuff activity may be appropriate in the early postoperative period, so we aimed to quantify the effect of resistance exercises on the muscle activity of a semi-immobilized upper limb. METHOD: Fifteen shoulder muscles of the dominant limb of 14 healthy subjects were evaluated by electromyography, with 11 surface electrodes and 4 fine-wire electrodes in the rotator cuff muscles. While wearing an orthosis, the subjects completed resistance tests including elbow and wrist flexion/extension with 3 loads, maximal squeezing, and shoulder adduction against 3 different foams. The peak activity of each muscle was normalized to maximal voluntary contraction (% MVC). RESULTS: Shoulder muscles were activated less than 20% MVC during elbow and wrist flexion/extension with 2-lb (907-g) and 4-lb (1814-g) loads. In the maximal squeezing test, rotator cuff activity exceeded 20% MVC in some cases. During shoulder adduction tests, subscapularis, latissimus dorsi, triceps, and pectoralis major had the highest activation levels; supraspinatus and infraspinatus were minimally activated. CONCLUSION: Supported elbow and wrist flexion/extension in the horizontal plane, with weights of up to 4 lb (1814 g), minimally activates the rotator cuff muscles while potentially preventing muscle disuse of other upper limb musculature. Resisted shoulder adduction cannot be considered safe for all rotator cuff injuries. LEVEL OF EVIDENCE: Basic science study, electromyography

Electromyographic activity in the immobilized shoulder musculature during ipsilateral elbow, wrist, and finger movements while wearing a shoulder orthosis.

BACKGROUND: Shoulder immobilization after rotator cuff surgery is usually prescribed to protect the repaired tendons; however, shoulder orthoses often also immobilize the elbow and wrist joints. There is insufficient evidence to support that elbow and wrist movements can affect repair integrity by highly activating the rotator cuff muscles. The aim of this study was to quantify the electromyographic activity of immobilized shoulder muscles during elbow, wrist, and finger movements. METHODS: Fifteen shoulder muscles of the dominant limb of 14 healthy subjects were evaluated by use of electromyography with 11 surface electrodes and 4 fine-wire electrodes in the rotator cuff muscles. While wearing a custom orthosis, the subjects completed tests involving elbow, wrist, and finger movements of the ipsilateral limb. The peak activity of each muscle was normalized to maximum voluntary contraction (percent MVC) and averaged across the subjects. RESULTS: Rotator cuff muscles were activated to less than 10% MVC in both slow and fast elbow flexions. The mean peak activations of all muscles during wrist and finger movements were less than 5% MVC. In daily activities such as writing, typing, clicking a computer mouse, and holding a box or bag, rotator cuff muscle activity did not exceed 11% MVC, but sudden movements such as grasping a bottle could show higher levels of activity, which in some individuals exceeded 20% MVC. CONCLUSION: Elbow, wrist, and finger movements could minimally activate the rotator cuff muscles when the shoulder is immobilized with an orthosis.

Investigating the reliability and validity of subacromial space measurements using ultrasound and MRI.

BACKGROUND: While ultrasound (US) measures of the subacromial space (SAS) have demonstrated excellent reliability, measurements are typically captured by experts with extensive ultrasound experience. Further, the agreement between US measured SAS width and other imaging modalities has not been explored. This research evaluated the agreement between SAS measures captured by novice and expert raters and between US and magnetic resonance imaging (MRI). This study also evaluated the effect of US transducer tilt on measured SAS. METHODS: Nine men and nine women participated in this study. US images were captured by a novice and expert with the participant in both seated and supine positions. An inclinometer was fixed to the US probe to measure transducer tilt. SAS width was measured in real time from freeze framed images. MRI images were captured, and the humerus and acromion manually segmented. The SAS width was measured using a custom algorithm. RESULTS: Intraclass correlation coefficients (ICCs) between novice and expert raters were 0.74 and 0.63 for seated and supine positions, respectively. Intra-rater agreement was high for both novice (ICC = 0.83-0.84) and expert (ICC ≥ 0.94) raters. Agreement between US and MRI was poor (ICC = 0.21-0.49) but linearly related. CONCLUSIONS: Moderate agreement between novice and expert raters was demonstrated, while the agreement between US and MRI was poor. High intra-rater reliability within each rater suggests that US measures of the SAS may be completed by a novice with introductory training.

Regional Electromyography of the Infraspinatus and Supraspinatus Muscles During Standing Isometric External Rotation Exercises.

BACKGROUND: Whole-muscle electromyography (EMG) data of the rotator cuff support external rotation (ER) strengthening exercises during shoulder rehabilitation. However, distinct neuroanatomic regions in the supraspinatus and infraspinatus exist. Differences in regional muscle activity occur during rehabilitation exercises, but little information is available for ER exertions. HYPOTHESIS: Regional infraspinatus and supraspinatus muscle activity during standing ER exertions will differ with posture and intensity. STUDY DESIGN: Descriptive laboratory study. LEVEL OF EVIDENCE: Level 5. METHODS: Twenty healthy individuals (12 men, 8 women) participated. Fine wire electrodes were inserted into 2 supraspinatus and 3 infraspinatus muscle regions. EMG data were recorded during standing isometric ER exertions at 2 intensities (maximal, submaximal) and in 7 postures defined by the angle (0°, 30°, 90°) and plane (abduction, scaption, flexion) of arm elevation. EMG data were normalized to maximum voluntary isometric contraction (% MVIC) to examine the influences of posture, intensity and their interaction on muscle activity. RESULTS: Superior infraspinatus activity was higher in 0° of elevation (50.9% ± 5.7% MVIC) versus 30° of flexion (37.4% ± 3.9% MVIC) at maximal intensity. Inferior infraspinatus activity was higher in 90° of scaption (max = 59.8% ± 2.8% MVIC, submax = 29.4% ± 1.9% MVIC) versus 0° of elevation (max = 42.3% ± 4.5% MVIC, submax = 22.4% ± 2.8% MVIC) (P = 0.02, P = 0.05, respectively). Anterior supraspinatus activity was highest in 90° of adbuction (max = 61.6% ± 3.1% MVIC; submax = 39.1% ± 3.8% MVIC) and lowest in 30° of flexion (max = 29.0% ± 3.4% MVIC, submax = 15.6% ± 1.7% MVIC) and 90° of flexion (max = 34.6% ± 2.4% MVIC, submax = 14.8% ± 1.9% MVIC). Posterior suprasptinatus activity was lowest in 0° of elevation (34.2% ± 3.0% MVIC), 30° of flexion (33.0% ± 3.6% MVIC) and highest in 90° of abduction (56.2% ± 4.1% MVIC) and 90° of scaption (46.7% ± 2.8% MVIC) (all Ps < 0.04). CONCLUSION: Regional infraspinatus and supraspinatus muscle activity differed with posture and intensity. Superior and middle infraspinatus muscle activities were similar across postures, but inferior infraspinatus activity was highest in 90° of arm elevation. Anterior and posterior supraspinatus activities were higher in the abduction and scaption planes, especially at 90° of elevation, as compared with the flexion plane. CLINICAL RELEVANCE: In shoulder rehabilitation of supraspinatus tendon injuries, ER exercises in the flexion plane challenge the whole infraspinatus muscle and require lower supraspinatus muscle activity.

Regional activation of supraspinatus and infraspinatus sub-regions during dynamic tasks performed with free weights.

Growing evidence supports the existence of distinct anatomical sub-regions within supraspinatus and infraspinatus, but only recently has attention turned to exploring their potential functional differences. Using indwelling fine-wire electromyography, muscle activity was investigated from these sub-regions in 15 participants (mean 34 yr, 170 cm, 71.9 kg) during dynamic external rotation (ER), abduction, flexion, and scaption tasks with and without free weights corresponding to 50% and 75% of the participant's five repetition maximum. Electromyography data were normalized to isometric and isokinetic maximal voluntary contractions and activation ratios for each sub-region compared. Differences in mean regional activation ratios for supraspinatus and infraspinatus varied by arm posture, but were not influenced by load. Relative activation of posterior supraspinatus was greater during an ER task performed in side lying compared to an ER task performed with 90° of humeral elevation in seated and prone postures. Relative activation of superior infraspinatus was greater during an ER task in prone and side lying postures compared to flexion and scaption. Similar results were found when comparing regional muscle activation ratios for infraspinatus between tasks regardless of normalization method employed. These findings may impact exercise selection in the non-operative management of rotator cuff tears.

Sub-regional activation of supraspinatus and infraspinatus muscles during activities of daily living is task dependent.

The supraspinatus and infraspinatus muscles each have multiple sub-regions that may activate differentially in activities of daily living. Awareness of these differential demands critically informs rehabilitation of rotator cuff muscle following injury, particularly if centered on recovering and strengthening the rotator cuff to perform daily tasks. This study quantified muscle activation of supraspinatus and infraspinatus sub-regions during the performance of six activities of daily living. Twenty-three participants (mean: 22.6 ± 2.6 years) completed the following tasks: opening a jar, reaching at shoulder height, overhead reaching, pouring water from a pitcher, eating with a spoon, and combing hair. Indwelling electromyography was collected from the anterior and posterior supraspinatus and superior, middle, and inferior infraspinatus. Tasks requiring high arm elevations (e.g. reaching at shoulder and overhead height) activated anterior supraspinatus between 21 and 28% MVC. The posterior supraspinatus consistently activated between 10 and 30% MVC across all tasks. All sub-regions of infraspinatus activated highly (between 18 and 25% MVC) in tasks requiring high arm elevations in flexion. These findings may be leveraged to define effective measures to increase rotator cuff function in daily tasks.

Activation of Supraspinatus and Infraspinatus Partitions and Periscapular Musculature During Rehabilitative Elastic Resistance Exercises.

OBJECTIVE: The purpose of this study was to quantify the activation of partitions within supraspinatus and infraspinatus and some periscapular muscles during four resistance exercises with elastic bands. DESIGN: Twenty-seven right-handed healthy volunteers (age, 22.5 ± 2.7 yrs) were recruited. Intramuscular electromyography from supraspinatus (anterior and posterior) and infraspinatus (superior and middle) and surface electromyography data from the upper, middle, and lower trapezius and serratus anterior were recorded during four elastic resistance exercises (Y, T, W, L). Kinematics were recorded synchronously. Electromyography values were presented as percentage of maximal voluntary isometric contraction and compared across exercises using analysis of variance. Muscle activation ratios were also calculated. RESULTS: The mean activations of all rotator cuff partitions were more than 40% maximal voluntary isometric contraction, except middle infraspinatus during the T exercise (29.3% maximal voluntary isometric contraction). Serratus anterior activity was significantly higher during the Y exercise (P < 0.008). Lower trapezius was activated more than 80% maximal voluntary isometric contraction in all four exercises with higher contributions compared with the upper trapezius. CONCLUSIONS: The investigated exercises induced moderate to high activation in supraspinatus and infraspinatus partitions and very high activation in lower trapezius. YTWL exercises are appropriate for strengthening of some rotator cuff and periscapular muscles and for late stages of shoulder rehabilitation.

Verification of intramuscular electromyography electrode placement for neuromuscular partitions of infraspinatus.

The infraspinatus muscle is composed of three neuromuscular partitions: superior, middle and inferior. Although methods for fine-wire EMG electrode insertion into these partitions have been developed and used, it has yet to be verified. The purpose of this cadaveric EMG needle placement study was to assess the accuracy and reproducibility of a protocol used to target the three partitions of infraspinatus. On seven shoulder specimens, two investigators inserted needles into each superior, middle and inferior partition according to a previously developed protocol. Each was blinded to the other's insertion sites. The specimens were dissected and the location of each needle was digitized and modeled in 3D. Of the 42 needles that were inserted, 32 were placed in the targeted partition. The highest accuracy rate occurred for the middle partition (100%), followed by the inferior (71.4%) and then the superior (57.1%). When the needles were not placed in the targeted partition, they were located in the neighboring partition within infraspinatus or the teres minor muscle. The current study showed the middle partition could be targeted accurately, whereas the superior and inferior partitions were more challenging. Ultrasound guidance may be necessary to ensure accurate placement into all parts of infraspinatus.

Arm posture influences on regional supraspinatus and infraspinatus activation in isometric arm elevation efforts.

This study aimed to evaluate the effect of arm posture on activation of the anterior and posterior regions of supraspinatus and the superior and middle regions of infraspinatus during resisted isometric arm elevations. Thirty-one healthy participants performed 18 isometric resistance exertions against a force cube in three elevation planes (flexion, scaption, abduction) and three elevation angles (30°, 90°, 150°) in maximal and sub-maximal resistance conditions. EMG data were obtained using four pairs of fine wire electrodes. The mean activation of each region and the activation ratios were compared across postures using ANOVAs. Supraspinatus anterior was significantly more active during abduction and scaption, and in higher elevation angles, while the posterior region showed similar activation levels across postures. Infraspinatus regions were more active during flexion with more relative activation of the infraspinatus superior at 90° flexion. The results suggest that regional activation of supraspinatus and infraspinatus should be considered for assessment and rehabilitation purposes. In any clinical setting where it is important to reduce the stress on the supraspinatus anterior, isometric flexion exercises performed with arm in low elevation angles could provide the opportunity to strengthen the posterior region of supraspinatus with limited stress on the anterior region. Beside external rotation exertions, resisted flexion tests may be useful for evaluation of infraspinatus regions.

Maximal voluntary isometric contraction tests for normalizing electromyographic data from different regions of supraspinatus and infraspinatus muscles: Identifying reliable combinations.

This study aimed to identify optimal sets of maximal voluntary isometric contractions (MVICs) for normalizing EMG data from anterior and posterior regions of the supraspinatus, and superior, middle and inferior regions of the infraspinatus. 31 right-handed young healthy individuals (15 males, 16 females) participated. EMG activity was obtained from two regions of supraspinatus and three regions of infraspinatus muscles via fine wire electrodes. Participants performed 15 MVIC tests against manual resistance. The EMG data were normalized to the maximum values. Optimal sets of MVIC combinations, defined as those which elicited >90% MVIC activation in the muscles of interest in >80% and >90% of the population, were obtained. EMG data from the inferior region of infraspinatus were removed from analysis due to technical problem. No single test achieved maximal activation of both regions of either the supraspinatus or infraspinatus. Instead, a combination of 6-8 MVICs were required to reach >90% MVIC activation in both parts of those muscles. In all regions of the rotator cuff muscles, the optimal combination was obtained with 8-10 MVICs. The proposed combinations can reduce inter-participant variability in generating maximal activation from different regions of the supraspinatus and infraspinatus muscles.

The effects of plane and arc of elevation on electromyography of shoulder musculature in patients with rotator cuff tears.

BACKGROUND: Arm elevations in different planes are commonly assessed in clinics and are included in rehabilitation protocols for patients with rotator cuff pathology. The aim of this study was to quantify the effect of plane and angle of elevation on shoulder muscles activity in patients with symptomatic rotator cuff tear to be used for rehabilitation purposes. METHODS: Eight symptomatic patients with rotator cuff tears were assessed by using EMG (11 surface and 2 fine wire electrodes) synchronized with a motion analysis. The subjects completed five elevations in full can position (arm externally rotated and thumb up) in frontal, scapular and sagittal planes. Muscle activity in three elevation arcs of 20° (from 0° to 60°) was presented as the percentage of mean activity. Data were analyzed by mixed linear models (α=0.003), and Tuckey Post-hoc comparisons for significant effects (α=0.05). FINDINGS: The effect of plane was significant for supraspinatus, middle trapezius, anterior, middle, and posterior deltoid, triceps, and pectoralis major (P<0.001). Supraspinatus was more active during abduction than scaption and flexion (P<0.05), and its activity did not increase significantly after 40° of elevation (P>0.05). Infraspinatus had similar activity pattern in the three planes of elevation (P>0.003) with increasing trend in accordance with the elevation angle. INTERPRETATION: In any rehabilitation protocol, if less activity of supraspinatus is desired, active arm elevation should be directed toward flexion and scaption and postponed abduction to prevent high level of activity in this muscle.

Clinical manifestations of the female athlete triad among some Iranian athletes.

PURPOSE: The study's purpose was to evaluate clinical manifestations of the female athlete triad among some elite Iranian athletes. METHODS: This cross-sectional study was conducted in three phases: 1) screening for menstrual irregularity (oligomenorrhea/amenorrhea) and/or stress fracture and weight-reducing drugs, 2) measurement of bone mineral density by dual-energy x-ray absorptiometry, and 3) a clinical interview to diagnose eating disorders. Phases 2 and 3 were conducted in athletes who reported menstrual irregularity and/or stress fracture and weight-reducing drugs. RESULTS: We evaluated a total of 786 athletes (94%) with a mean age of 21.1 ± 4.5 yr old. Seventy-two (9.2%) athletes reported menstrual irregularity, 11 (1.4%) of whom had polycystic ovary syndrome. Only three athletes (0.4%) had all three common clinical manifestations of the Triad (eating disorders, menstrual irregularity, and low bone mineral density). There was no association between these disorders and body mass index or type of sport. A total of 17 (2%) reported stress fracture, 14 of whom also reported a history of stress fracture without any menstrual irregularity. The athletes who competed in high-risk sports (endurance sports, weight class sports, and sports requiring a lean build) had significantly more stress fractures than those participating in other types (odds ratio = 3.35, 95% confidence interval = 1.22-9.15). CONCLUSIONS: Although the prevalences of clinical functional hypothalamic menstrual disorders and stress fracture were less than those reported in some other countries, athletes in the high-risk group had significantly more stress fractures than those in the low-risk group. Future studies should focus on screening, diagnosing, preventing, and treating all components of the newly defined Triad, especially in high-risk sports in Iran.

The relation between athletic sports and prevalence of amenorrhea and oligomenorrhea in Iranian female athletes.

BACKGROUND: In 1992, the concept of female athlete triad was introduced to describe the interrelated problems of amenorrhea, eating disorders and osteoporosis seen in female athletes. To gain a clearer picture of amenorrhea/oligomenorrhea in Iran, one of the main components of the female athlete triad, we therefore established this study on the prevalence of amenorrhea/oligomenorrhea in elite Iranian female athletes, also evaluating the risk factors of these disorders in the same population. METHODS: This study performed as a cross-sectional study. All elite Iranian female athletes of 34 sports federation, including female athletes in national teams and medalists of Tehran were invited to participate. A total of 788 (95% response rate) returned the questionnaires and were examined. Younger athletes under the age of menarche were excluded. Each athlete completed a self-administered questionnaire, which covered the following questions about participant's demographic information, athletic history, history of injuries and menstrual pattern. In order to diagnose the causes of amenorrhea/Oligomenorrhea including polycystic ovary syndrome(PCOS), participants with amenorrhea/Oligomenorrhea underwent further investigation. They were evaluated by following Para clinic investigation, and an ultrasonographic study of ovary. RESULTS: The age ranged from 13-37 (mean = 21.1, SD = 4.5). Seventy one (9.0%) individuals had amenorrhea/oligomenorrhea, among those, 11 (15.5%) had PCOS.There was also a positive association between amenorrhea/oligomenorrhea and the following: age under 20 OR; 2.67, 95%CI(1.47 - 4.85), weight class sports OR; 2.09, 95%CI(1.15 - 3.82), endurance sports OR; 2.89, 95%CI(1.22 - 6.84), late onset of menarche OR; 3.32 95%CI(1.04-10.51), and use of oral contraceptive pills OR; 6.17, 95%CI(3.00 - 12.69). Intensity of training sport or BMI were not risk factors. CONCLUSION: These findings support the previous findings in the literature that the prevalence of amenorrhea/oligomenorrhea is high in athletes. Furthermore, we provided the first report on the prevalence of PCOS in female athletes with amenorrhea/oligomenorrhea. Athletes would be greatly benefited by greater general awareness about the complications of amenorrhea/oligomenorrhea.To increase awareness of exercise-associated menstrual cycle irregularities, it is necessary to design complete and comprehensive education programs for female athletes, their parents, their coaches, and the relevant authorities.