Rodney A. Green

Gluteus medius: an intramuscular EMG investigation of anterior, middle and posterior segments during gait.

Previous electromyographic (EMG) studies of gluteus medius (GMed) have not accurately quantified the function of the three proposed structurally and functionally unique segments (anterior, middle and posterior). Therefore this study used anatomically verified locations for intramuscular electrode recordings in three segments of GMed to determine whether the segments are functionally independent. Bipolar fine wire electrodes were inserted into each segment of GMed in 15 healthy individuals. Participants completed a series of four walking trials, followed by maximum voluntary isometric contractions (MVICs) in five different positions. Temporal and amplitude variables for each segment were compared across the gait cycle using ANOVA. The relative contributions of each segment to the MVIC trials were compared with non-parametric tests. All segments showed a biphasic response during the stance phase of gait. There were no differences in amplitude variables (% MVIC) between segments, but the anterior segment had a later peak during both the first and second bursts.For the MVIC trials, there were significant differences in amplitude between segments in four of the five test positions. These data indicate that GMed is composed of three functionally independent segments. This study contributes to the theoretical understanding of the role of GMed.

Effect of overuse injury and the importance of training on the use of adjustable workstations by keyboard operators.

The introduction of adjustable workstations for keyboard operators has been widely recommended to eradicate constrained working postures leading to the development of musculoskeletal disorders. A questionnaire evaluating the use of adjustable workstations was analyzed for 514 keyboard operators. Anthropometric dimensions and workstation settings were measured for 15 operators. There was no difference between sufferers and nonsufferers of overuse injury on the basis of adjustability of their equipment. However, sufferers were less satisfied with their equipment and there was evidence that inappropriate postures were being adopted. The availability of adjustable equipment per se does not necessarily solve the problem. The design of the equipment must be based on suitable anthropometric data and operators must be trained in the correct use of the equipment. The results of this study indicate a perceived need for training and/or information on workstation adjustment among operators, with a preference for information that is supplied verbally, rather than in literature form.

Participation in Asynchronous Online Discussion Forums Does Improve Student Learning of Gross Anatomy.

Asynchronous online discussion forums are common in blended learning models and are popular with students. A previous report has suggested that participation in these forums may assist student learning in a gross anatomy subject but it was unclear as to whether more academically able students post more often or whether participation led to improved learning outcomes. This study used a path model to analyze the contribution of forum participation, previous academic ability, and student campus of enrolment to final marks in a multicampus gross anatomy course for physiotherapy students. The course has a substantial online learning management system (LMS) that incorporates asynchronous forums as a learning tool, particularly to answer learning objectives. Students were encouraged to post new threads and answer queries in threads started by others. The forums were moderated weekly by staff. Discussion forums were the most used feature of the LMS site with 31,920 hits. Forty‐eight percent of the students posted at least once with 186 threads initiated by students and a total of 608 posts. The total number of posts made a significant direct contribution to final mark (P = 0.008) as did previous academic ability (P = 0.002). Although campus did not contribute to final mark, there was a trend for students at the campus where the course coordinator was situated to post more often than those at the other campus (P = 0.073). These results indicate that asynchronous online discussion forums can be an effective tool for improving student learning outcomes as evidenced by final marks in gross anatomy teaching. Anat Sci Educ. 7: 71–76.

The stabilizing role of the rotator cuff at the shoulder--responses to external perturbations.

BACKGROUND The rotator cuff has been hypothesized as a dynamic stabilizer at the shoulder joint yet evidence supporting this role remains inconclusive. We aimed to investigate the activity levels and recruitment patterns between the rotator cuff and superficial shoulder muscles in response to external perturbations to provide insight into the stabilizing role of the rotator cuff. METHODS Surface and intramuscular electromyography (EMG) were used to measure timing of onset and level of activation (EMG amplitude as a percentage of maximum voluntary isometric contraction, % MVIC) of rotator cuff (supraspinatus, infraspinatus and subscapularis) and superficial muscles (anterior and posterior deltoid) on 19 healthy participants. Participants received expected and unexpected externally applied perturbations in directions of internal and external rotation at the glenohumeral joint. FINDINGS All three rotator cuff muscles demonstrated pre-activation in anticipation of the perturbation prior to their representative global synergists, anterior and posterior deltoid (P<0.05). Subscapularis and infraspinatus were activated prior to all other muscles during external rotation and internal rotation perturbation trials respectively (P<0.01). Direction specific activation levels were observed; subscapularis was moderately strongly active (37% MVIC) in response to an external rotation perturbation and infraspinatus was moderately active (28% MVIC) in response to an internal rotation perturbation. No muscle was activated >10% MVIC when not acting as the main muscle opposing the movement. INTERPRETATION The rotator cuff may function in part as a dynamic stabilizing unit of the shoulder demonstrating a feedforward muscle activation pattern. These results may assist in improving assessment and treatment of shoulder dysfunction.

Measurement of subacromial impingement of the rotator cuff.

OBJECTIVE Recent evidence suggests that shoulder impingement syndrome arises from primary rotator cuff pathology and may be related to the inability of the rotator cuff to prevent superior humeral head migration in shoulder elevation. Impingement involves compression of subacromial structures, including the rotator cuff. Previously, clinical tests have been shown to be inaccurate in diagnosing rotator cuff impingement. A lack of anatomical validity might explain the inaccuracy of these tests. This study aimed to clarify the anatomical basis of subacromial compression of the rotator cuff by analysing the compression forces generated and observing the structures impinged in a variety of shoulder positions. DESIGN This observational case series involved the dissection of nine embalmed cadaveric shoulders. METHOD Pressure transducers were placed deep to the coracoid process, coracoacromial ligament, the anterior acromion and the posterior acromion. Shoulders were moved into internal and external rotation from the positions of flexion, abduction and extension. At each position, pressure readings were recorded and structures being compressed observed visually. RESULTS Highest pressures were recorded in flexion/internal rotation at the coracoacromial ligament, in abduction/internal rotation at the coracoid process (both involving the rotator interval) and in abduction/internal rotation at the coracoacromial ligament (involving supraspinatus). Supraspinatus was also observed to be compressed in extension/external rotation (against the anterior acromion). Infraspinatus was compressed in extension/external rotation (against the posterior acromion), while subscapularis was compressed in flexion/internal rotation and flexion/external rotation (both against the coracoid process). CONCLUSION This study identifies shoulder positions likely to impinge particular rotator cuff tendons.

Verification of a standardized method for inserting intramuscular EMG electrodes into uniquely oriented segments of gluteus minimus and gluteus medius

Guidelines for assessing the function of gluteus minimus and gluteus medius with electromyography (EMG) traditionally offer one electrode placement site per muscle. However, anatomical studies suggest that there are two uniquely oriented segments within gluteus minimus (anterior and posterior), and three within gluteus medius (anterior, middle, and posterior) with potential for independent function. Assessment of these muscles with one electrode may therefore provide only a limited account of their role. Thus, the aim of this cadaveric study was to verify guidelines for placing intramuscular electrodes into two uniquely oriented segments of gluteus minimus, and three segments of gluteus medius. The guidelines were developed with reference to anatomical reports, cadaveric observation and real‐time ultrasound imaging in vivo. Five cadaveric gluteal regions were marked for intramuscular electrode insertions based on these guidelines. Intramuscular electrodes were inserted into the marked regions of gluteus minimus (2×) and gluteus medius (3×) with the aid of a 15 cm biopsy needle. Systematic dissection revealed that electrodes were successfully inserted into uniquely oriented segments of gluteus minimus and medius. The orientation of fascicles surrounding each electrode was also consistent with segmental descriptions in past anatomical research. The findings of this research suggest that the guidelines described may be used to assess the functional role of segments within gluteus minimus and medius in health and dysfunction using EMG. Finally, electromyographers intent on investigating the role of posterior gluteus minimus must be cautious of the superior gluteal neurovascular bundle. Clin. Anat., 2013.

The anatomical basis for clinical tests assessing musculoskeletal function of the shoulder

Abstract A large number of clinical tests have been reported to assess the musculoskeletal integrity of the shoulder; however, for some of these tests, diagnostic accuracy is poor. Poor diagnostic accuracy may be related to a lack of understanding of the anatomical basis of the test. We conducted a systematic review of the relevant literature to ascertain whether an anatomical basis had been established for 34 common clinical tests for shoulder pathology. Searching of electronic databases yielded 11 papers that had reported on the anatomical basis for a total of six of the 34 clinical tests. Four of these tests had evidence from more than one study of a valid anatomical basis, but only two tests provided consensus evidence that supported the anatomical basis provided by the test developer. The lack of evidence about the anatomical validity of common clinical tests for shoulder function may explain the poor diagnostic accuracy of many of these tests. Further research into anatomical validity of tests may assist in the development of clinical tests of musculoskeletal integrity with improved diagnostic accuracy.

Gluteus minimus: an intramuscular EMG investigation of anterior and posterior segments during gait.

Gluteus minimus is believed to consist of two structurally and functionally unique segments (anterior and posterior); however there is a lack of electromyography (EMG) research that attempts to verify current theoretical knowledge of this muscle. The purpose of this study was therefore to evaluate the function of gluteus minimus during gait, and to determine whether anterior and posterior segments are functionally independent. Bipolar fine wire intramuscular EMG electrodes were inserted into anterior and posterior gluteus minimus segments of fifteen healthy volunteers (9 males) according to previously verified guidelines. Participants completed a series of four walking trials, followed by maximum voluntary isometric contractions in five different positions. Temporal and amplitude variables for each segment were compared across the gait cycle with independent t-tests. The relative contribution of each segment to the maximum resisted trials was compared with Mann-Whitney U tests (α = 0.05). Anterior and posterior segments were contracting at different relative intensities for three of the five maximum resisted trials (effect size = 0.39 to 0.62, P < 0.037). The posterior segment was larger in EMG amplitude (peak and average) during the first 20% of the gait cycle (effect size = 0.96 to 1.03, P < 0.02), while the anterior segment peaked later in the stance phase (effect size = 0.83, P = 0.034). Gluteus minimus is therefore composed of functionally independent segments. These results build on contemporary theoretical knowledge and may signify hip stabilising roles for each segment across different phases of the gait cycle.

Technical application and the level of discomfort associated with an intramuscular electromyographic investigation into gluteus minimus and gluteus medius

Our current theoretical understanding of gluteus minimus (GMin) and gluteus medius (GMed) function is primarily based on cadaveric studies and biomechanical modelling. There is an absence of electromyographic (EMG) research that aims to verify this understanding, particularly in relation to the potentially unique functional roles of structurally distinct segments within GMin (anterior and posterior) and GMed (anterior, middle and posterior). The aim of this paper is to provide a comprehensive technical description for inserting intramuscular EMG electrodes into uniquely oriented segments of GMin and GMed; and to report the levels of discomfort associated with gluteal intramuscular electrode insertions. Fifteen healthy volunteers took part in a series of walking trials after intramuscular EMG electrodes were inserted into segments of GMin (×2) and GMed (×3) according to previously verified guidelines. Visual analogue scores following walking trials at comfortable and fast speed indicate that discomfort levels associated with these insertions were low (2.4±1.4 and 1.6±0.7 respectively). The technical descriptions and illustrations provided in this paper will allow trained intramuscular electromyographers to insert electrodes into these muscle segments with confidence.

Stabilizing characteristics of rotator cuff muscles: a systematic review.

Abstract Purpose: To systematically review the evidence in support of the purported function of the rotator cuff muscles as dynamic stabilizers of the glenohumeral joint. Methods: Electronic searches were conducted using AMED, CINAHL, Medline and SPORT Discus. Studies were required to include at least one characteristic of a stabilizer muscle. Quality analysis was completed by two assessors independently. Data were extracted for four main characteristics of stabilizer muscles: (1) moment arm length, (2) onset of muscle activity, (3) joint stiffness as measured by contribution of muscle activity to prevent joint translation, (4) co-contraction as demonstrated by electromyography muscle activity and co-activation ratio. Results: Twenty of the 1726 identified studies were selected for the review. Rotator cuff muscles can limit joint translation (five studies) and contribute to joint stiffness (one study), possess shorter moment arms in some movements (three studies), but show limited evidence for stabilizing characteristics of early onset (seven studies) and co-contraction (seven studies). Conclusion: The rotator cuff muscles exhibited some stabilization characteristics but not all. On the basis of our current low to moderate quality evidence, the most likely, but as yet unverified, stabilization role for the rotator cuff muscles appears to be limiting of translation in a direction-specific manner. Implications for Rehabilitation Diagnostic tests currently used are based largely on the assumption that the muscles of the rotator cuff can be individually recruited as prime movers. Our findings demonstrate the need for more research into the proposed stabilizing mechanisms of the rotator cuff muscles to increase diagnostic accuracy and more targeted shoulder rehabilitation programs. It may be that the rotator cuff muscles have a role in limiting glenohumeral joint translation which is not reflected in the current diagnostic tests and rehabilitation protocols. Further research is required to establish this stabilizing characteristic in living subjects. Knowledge of the contribution of rotator cuff muscle activation in limiting joint translation may be an important aspect in properly assessing and quantifying the proposed function of the rotator cuff muscles as dynamic stabilizers of the shoulder joint.