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Concept: Scapula

169

Changes in muscle activities are commonly associated with shoulder impingement and theoretically caused by changes in motor program strategies. The purpose of this study was to assess for differences in latencies and deactivation times of scapular muscles between subjects with and without shoulder impingement. Twenty-five healthy subjects and 24 subjects with impingement symptoms were recruited. Glenohumeral kinematic data and myoelectric activities using surface electrodes from upper trapezius (UT), lower trapezius (LT), serratus anterior (SA) and anterior fibers of deltoid were collected as subjects raised and lowered their arm in response to a visual cue. Data were collected during unloaded, loaded and after repetitive arm raising motion conditions. The variables were analyzed using 2 or 3 way mixed model ANOVAs. Subjects with impingement demonstrated significantly earlier contraction of UT while raising in the unloaded condition and an earlier deactivation of SA across all conditions during lowering of the arm. All subjects exhibited an earlier activation and delayed deactivation of LT and SA in conditions with a weight held in hand. The subjects with impingement showed some significant differences to indicate possible differences in motor control strategies. Rehabilitation measures should consider appropriate training measures to improve movement patterns and muscle control.

Concepts: Muscle, Humerus, Shoulder, Deltoid muscle, Clavicle, Glenohumeral joint, Scapula, Serratus anterior muscle

169

INTRODUCTION: Although palsy of the long thoracic nerve is the classical pathogenesis of winging scapula, it may also be caused by osteochondroma. This rare etiopathology has previously been described in pediatric patients, but it is seldom observed in adults. CASE PRESENTATION: We describe three cases of static scapular winging with pain on movement. Case 1 is a Caucasian woman aged 35 years with a wing-like prominence of the medial margin of her right scapula due to an osteochondroma originating from the ventral omoplate. Histopathological evaluation after surgical resection confirmed the diagnosis. The postoperative course was unremarkable without signs of recurrence on examination at 2 years. Case 2 is a Caucasian woman aged 39 years with painful scapula alata and neuralgic pain projected along the left ribcage caused by an osteochondroma of the left scapula with contact to the 2nd and 3rd rib. Following surgical resection, the neuropathic pain continued, demanding neurolysis of the 3rd and 4th intercostal nerve after 8 months. The patient was free of symptoms 2 years after neurolysis. Case 3 is a Caucasian woman aged 48 years with scapular winging due to a large exostosis of the left ventral scapular surface with a broad cartilaginous cap and a large pseudobursa. Following exclusion of malignancy by an incisional biopsy, exostosis and pseudobursa were resected. The patient had an unremarkable postoperative course without signs of recurrence 1 year postoperatively. Based on these cases, we developed an algorithm for the diagnostic evaluation and therapeutic management of scapula alata due to osteochondroma. CONCLUSIONS: Orthopedic surgeons should be aware of this uncommon condition in the differential diagnosis of winged scapula not only in children, but also in adult patients.

Concepts: Medical terms, Pathology, Physician, Pain, Scapula, Serratus anterior muscle, Winged scapula, Long thoracic nerve

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The aims of this study were to determine the survival of anatomic total shoulder arthroplasty with uncemented metal-backed (MB) glenoid components with a polyethylene (PE) insert in primary osteoarthritis, to assess the reasons for revision surgery, and to identify patients and diagnostic factors that influence failure rates.

Concepts: Medicine, Physician, Osteoarthritis, Hip replacement, Shoulder, Failure rate, Shoulder replacement, Scapula

55

The effects of protein supplementation on muscle thickness and strength seem largely dependent on its composition. The current study aimed at comparing the impact of an oral supplementation with vegetable Pea protein (NUTRALYS®) vs. Whey protein and Placebo on biceps brachii muscle thickness and strength after a 12-week resistance training program.

Concepts: Clinical trial, Muscle, Biceps brachii muscle, Triceps brachii muscle, Placebo, Scapula, Biceps curl

36

The scapula functions as a bridge between the shoulder complex and the cervical spine and plays a very important role in providing both mobility and stability of the neck/shoulder region. The association between abnormal scapular positions and motions and glenohumeral joint pathology has been well established in the literature, whereas studies investigating the relationship between neck pain and scapular dysfunction have only recently begun to emerge. Although several authors have emphasised the relevance of restoring normal scapular kinematics through exercise and manual therapy techniques, overall scapular rehabilitation guidelines decent for both patients with shoulder pain as well as patients with neck problems are lacking. The purpose of this paper is to provide a science-based clinical reasoning algorithm with practical guidelines for the rehabilitation of scapular dyskinesis in patients with chronic complaints in the upper quadrant.

Concepts: Vertebral column, Shoulder, Cervical vertebrae, Glenohumeral joint, Scapula, Acromion

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PURPOSE: It is commonly stated that supraspinatus initiates abduction; however, there is no direct evidence to support this claim. Therefore, the aims of the present study were to determine whether supraspinatus initiates shoulder abduction by activating prior to movement and significantly earlier than other shoulder muscles and to determine if load or plane of movement influenced the recruitment timing of supraspinatus. METHODS: Electromyographic recordings were taken from seven shoulder muscles of fourteen volunteers during shoulder abduction in the coronal and scapular planes and a plane 30° anterior to the scapular plane, at 25%, 50% and 75% of maximum load. Initial activation timing of a muscle was determined as the time at which the average activation (over a 25ms moving window) was greater than three standard deviations above baseline measures. RESULTS: All muscles tested were activated prior to movement onset. Subscapularis was activated significantly later than supraspinatus, infraspinatus, deltoid and upper trapezius, while supraspinatus, infraspinatus, upper trapezius, lower trapezius, serratus anterior and deltoid all had similar initial activation times. The effects of load or plane of movement were not significant. CONCLUSIONS: Supraspinatus is recruited prior to movement of the humerus into abduction but not earlier than many other shoulder muscles, including infraspinatus, deltoid and axioscapular muscles. The common statement that supraspinatus initiates abduction is therefore, misleading.

Concepts: Humerus, Shoulder, Rotator cuff, Supraspinatus muscle, Deltoid muscle, Muscles of the upper limb, Scapula, Serratus anterior muscle

28

The deltoid is a fascinating muscle with a significant role in shoulder function. It is comprised of three distinct portions (anterior or clavicular, middle or acromial, and posterior or spinal) and acts mainly as an abductor of the shoulder and stabilizer of the humeral head. Deltoid tears are not infrequently associated with large or massive rotator cuff tears and may further jeopardize shoulder function. A variety of other pathologies may affect the deltoid muscle including enthesitis, calcific tendinitis, myositis, infection, tumors, and chronic avulsion injury. Contracture of the deltoid following repeated intramuscular injections could present with progressive abduction deformity and winging of the scapula. The deltoid muscle and its innervating axillary nerve may be injured during shoulder surgery, which may have disastrous functional consequences. Axillary neuropathies leading to deltoid muscle dysfunction include traumatic injuries, quadrilateral space and Parsonage-Turner syndromes, and cause denervation of the deltoid muscle. Finally, abnormalities of the deltoid may originate from nearby pathologies of subdeltoid bursa, acromion, and distal clavicle.

Concepts: Humerus, Shoulder, Rotator cuff, Deltoid muscle, Axillary nerve, Clavicle, Scapula, Acromion

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PURPOSE: This study compared the status of suture knots immediately after repair and after shoulder motion to evaluate the possibility of movement-induced knot migration to a location nearer the glenoid. METHODS: We included 10 shoulders from 5 cadavers in the study. After posterior capsulotomy, a Bankart lesion was created. A capsulolabral repair was then performed with 3 knot-tying suture anchors. All knots were positioned on the capsular side, far from the articular surface. After the repair was complete, a photograph was taken with a metal rod placed to reference absolute distance. After passive pendulum motion was applied, another photograph was taken. The length of the suture strand from the knot base to the anchor insertion site was measured during both the initial repair and post-motion periods. RESULTS: Initial distances were 4.83 ± 1.09 mm for the inferior knot, 4.70 ± 0.97 mm for the middle knot, and 3.84 ± 1.25 mm for the superior knot. After motion, the distances were 3.52 ± 1.21 mm (P = .01), 3.07 ± 0.81 mm (P < .001), and 2.69 ± 1.18 mm (P = .016), respectively. Additional observations showed changes in direction and security of the knot. The change in knot direction from an initial orientation facing the capsular side to a new orientation facing the glenoid was observed in 5 of 10 inferior, 7 of 10 middle, and 6 of 10 superior knots. In addition, knot loosening was noted for the last half-hitches in 4 inferior knots and 1 middle knot. CONCLUSIONS: Intentional placement of suture knots away from the joint surface was not maintained after motion at the shoulder. CLINICAL RELEVANCE: Movement-induced knot migration may be detrimental to articular cartilage in the event that a knot becomes interposed between the glenoid and humeral head.

Concepts: Bone, Skeletal system, Humerus, Knee, Shoulder, Distance, Glenoid labrum, Scapula

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Alterations in scapular muscle activity, including excess activation of the upper trapezius (UT) and onset latencies of the lower trapezius (LT) and serratus anterior (SA) muscles, are associated with abnormal scapular motion and shoulder impingement. Limited information exists on the reliability of neuromuscular activity to demonstrate the efficacy of interventions. The purpose of this study was to characterize the reproducibility of scapular muscle activity (mean activity, relative onset timing) over time and establish the minimal detectable change (MDC). Surface electromyography (sEMG) of the UT, LT, SA and anterior deltoid (AD) muscles in 16 adults were captured during an overhead lifting task in two sessions, one-week apart. sEMG data were also normalized to maximum isometric contraction and the relative onset and mean muscle activity during concentric and eccentric phases of the scapular muscles were calculated. Additionally, reliability of the absolute sEMG data during the lifting task and MVIC was evaluated. Both intrasession and intersession reliability of normalized and absolute mean scapular muscle activity, assessed with intraclass correlation coefficients (ICC), ranged from 0.62 to 0.99; MDC values were between 1.3% and 11.7% MVIC and 24 to 135mV absolute sEMG. Reliability of sEMG during MVIC was ICC=0.82-0.99, with the exception of intersession upper trapezius reliability (ICC=0.36). Within session reliability of muscle onset times was ICC=0.88-0.97, but between session reliability was lower with ICC=0.43-0.73; MDC were between 39 and 237ms. Small changes in scapular neuromuscular mean activity (>11.7% MVIC) can be interpreted as meaningful change, while change in muscle onset timing in light of specific processing parameters used in this study is more variable.

Concepts: Muscle, Electromyography, Muscle contraction, Shoulder, Neuromuscular disease, Clavicle, Scapula, Serratus anterior muscle

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Although mechanomyography (MMG) reflects local vibrations from contracting muscle fibers, it also includes bulk movement: deformation in global soft tissue around measuring points. To distinguish between them, we compared the multi-channel MMG of resting muscle, which dominantly reflected the bulk movement caused by arterial pulsations, to that of the contracting muscle. The MMG signals were measured at five points around the upper arms of 10 male subjects during resting and during isometric ramp contraction from 5% to 85% of maximal voluntary contraction (MVC) of the biceps brachii muscle. The characteristics of bulk movement were defined as the amplitude distribution and phase relation among the five MMG signals. The bulk movement characteristics during the rest state were not necessarily the same among the subjects. However, below 30Hz, each subject’s characteristics remained the same from the rest state (0% MVC) to the contracting state (80% MVC), at which the bulk movement mainly originates from muscle contraction activity. Results show that the MMG of the low frequency domain (<30Hz) includes bulk movement depending on the mechanical deformation characteristics of each subject's body, for a wide range of muscle contraction intensities.

Concepts: Muscle, Biceps brachii muscle, Triceps brachii muscle, Muscle contraction, Phase, Scapula, Biceps curl