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PubMed2001

[Effect of muscle activity on the 3-dimensional movement pattern of the shoulder. Study with open MRI].

The objective of this study was to analyze the influence of shoulder muscle activity on the three-dimensional motion pattern of the shoulder girdle in the living. 14 healthy volunteers were investigated with an open MRI system at 60-120 degrees abduction--with and without activity of the shoulder abductors. The 3D motion pattern of the humerus, scapula, clavicle and M. supraspinatus were computed. Under muscle activity, the glenoid demonstrated a slightly reduced elevation at 60 degrees of abduction (20.5 degrees +/- 8.2 degrees vs. 23.1 degrees +/- 6.3 degrees; not significant), and at 120 degrees a significantly higher degree of rotation under muscle activity (43.3 degrees +/- 8.6 degrees vs. 36.1 degrees +/- 5.2 degrees; p < 0.01), whereas at 90 degrees no difference was observed. This caused a significant reduction of the scapulo-humeral rhythm at 120 degrees (2.6 vs. 1.5; p < 0.01), a significant increase of the supraspinatus angle (123.3 degrees +/- 6.7 degrees vs. 117.3 degrees +/- 6.5 degrees; p < 0.05) as well as a reduction of the supraspinato-humeral relationship (1.0 vs. 0.97). The study demonstrates that muscle activity leads to an alteration of shoulder girlde motion patterns at higher degrees of abduction, with increased rotation of the scapula, an altered spatial relationship between the supraspinatus and humerus.

Adult↗
PubMed1996

[Clinicoradiologic anatomy of the shoulder region].

Besides the skeletal elements, i.e., the clavicle, scapula and humerus, several muscles and soft tissues also participate in the construction of the human shoulder. These elements from and surround the shoulder girdle joints, which are the acromioclavicular and glenohumeral joint. Towards the trunk a connection is achieved by the sternoclavicular joint. Ossification of the clavicle, scapula and humerus begins within the 5th to 7th embryonic week. Around the age of 20 years ossification is completed. Parallel to this development and during adulthood, age-dependent changes take place in the composition and mixture of the bone marrow from red to yellow marrow. The shoulder girdle joints are constructed to permit a wide range of motion of the arm against the trunk. At the glenohumeral joint the spherical humeral head glides within the concave groove of the glenoid cavity. Stability is attained by the fibrocartilaginous glenoid labrum, which enlarges the articulating areas and the joint capsule with its strengthening ligaments. Variation of the joint capsule insertion, the glenoid labrum or the bony surfaces may predispose to luxation. Additional support to prevent luxation is obtained by the glenohumeral ligaments and the long biceps tendon. Active movement is provided by the superficial muscles and the rotator cuff muscles. Several bursae support free movement and decrease friction of the musculotendineous systems near the joint. Despite this complex construction several degenerative diseases can impair free movement of the human shoulder.

Acromioclavicular Joint↗
PubMed2005

Kinematic and muscle activity characteristics of multidirectional shoulder joint instability during elevation.

Alterations of shoulder motion have been suggested to be associated with shoulder disorders. The objective of this study was to perform a 3D motion analysis (kinematic and electromyographical) of skeletal elements and muscles of shoulder joint in patients with multidirectional instability. Fifteen patients with multidirectional instability and 15 normal controls were investigated during continuous elevation in the scapular plane. The spatial coordinates of 16 anatomical points of the shoulder to determine kinematical parameters were quantified by an ultrasound-based motion analyzer. The activities of 12 muscles were measured by surface electromyography. Kinematic characteristics of motion were identified by scapulothoracic, glenohumeral, and humeral elevation angles; range of angles; scapulothoracic and glenohumeral rhythm; scapulothoracis, glenohumeral, and scapuloglenoid ratios; and the relative displacement between the rotation centers of the humerus and the scapula. The electromyographical characteristics of motion were modeled by the on-off pattern of muscle activity. Significant alterations in kinematical parameters were observed between patients and asymptomatic volunteers. The anterior, posterior, and inferior dislocations of shoulders with multidirectional instability could be properly modeled by the relative displacement between the rotation centers of the scapula and humerus. The shorter activity by m. pectoralis maior and all three parts of m. deltoideus and longer activity by m. supraspinatus, m. biceps brachii, and m. infraspinatus assure the centralization of the glenuhumeral head of a shoulder with multidirectional instability.

Adult↗
PubMed1999

The lateral impaction of the shoulder.

17 patients had radiographic demonstration of injury to the clavicle, scapula and ribs from an impact delivered to the lateral shoulder. The study included 13 males and 4 females whose ages ranged from 18 to 83 years (average 45 years). Most injuries were sustained in falls or motor vehicle accidents. Analysis of these cases suggests a biomechanical hypothesis concerning the transmission of the impact forces within the shoulder girdle. According to this hypothesis, the impaction force applied to the lateral shoulder is transmitted from outside inward following two paths. The anterior and superior path passes through the acromio-clavicular joint, the clavicle, the costo-clavicular joint and the sterno-clavicular joint. The posterior and inferior path is transmitted within the gleno-humeral joint, the scapula and the scapulo-thoracic joint. Major impacting force is required to disrupt the anterior and posterior arches of the shoulder girdle. When both of these supporting structures are damaged, the patient is at risk for more serious injuries, including disruption of the thorax, shoulder joint, brachial plexus and neck.

Accidental Falls↗
PubMed2004

A three-dimensional model of the shoulder girdle. Forces developed in deltoid and supraspinatus muscles during abduction.

The aim of this study was to design a three-dimensional model of the human shoulder girdle. Fourteen muscles were modelled geometrically using robotics software (Solid Dynamics System). A static study in reverse dynamics allowed the forces developed in seven muscles to be studied, particularly in the deltoid and supraspinatus during abduction of the arm with the forearm bent at 90 degrees, the scapula being fixed. After optimization by Excel, this model allowed simultaneous curves of forces developed in every modelled muscular bundle to be obtained during various degrees of abduction of the arm from 0 degrees to 100 degrees, in the scapular plane. The analysis of supraspinatus and deltoid curves revealed an interesting chronology of action. The first muscle developed efforts estimated at 140 N, quickly relieved by the deltoid. It is also interesting to note that a constant action of supraspinatus was found throughout abduction of the arm. Clinical applications seem to be in simulation of muscular pathology of the shoulder girdle. This study is continuing by releasing the fixed scapula and by simulating muscle transfers proposed for massive ruptures of the rotator cuff.

Arm↗
PubMed1998

The anterior tilt of the acromion: radiographic evaluation and correlation with shoulder diseases.

The aim of this study was to test whether the anterior tilt of the acromion can be objectively evaluated on lateral radiographs, and whether there is a relation between this anatomical feature and the most common shoulder diseases. Lateral radiographs of 15 dried scapulas were performed in neutral position and with 5 degrees of caudal, cranial, anterior and posterior angulations. Two hundred and forty-three shoulders, both asymptomatic and affected by chronic and post-traumatic impingement, calcific tendinitis and instability, were examined by conventional radiography. The presence of rotator-cuff tears was investigated by sonography. A method was elaborated to obtain reproducible lateral radiographs and to determine the acromial tilt angle. Inter- and intraobserver and inter- and intraoperator variations in measurements were evaluated. Variations in tube angulation produced changes in tilt-angle values on dried scapulas. The average tilt angle for the chronic impingement and the instability groups were significantly different from the post-traumatic, calcific tendinitis and control groups. Rotator-cuff tears were significantly more frequent in the chronic impingement group and related to a more acute tilt angle. The inter- and intraobserver variability coefficients were 0.95 and 0.98, whereas the inter- and intraoperator variability coefficients were 0.94 and 0.96, respectively. Conventional radiography using fluoroscopy for positioning is a well-reproducible method for the evaluation of acromial tilt. There is a significant difference in tilt-angle values between some groups of subjects examined, but the lack of specificity limits the clinical importance of such measurement.

Acromion↗
PubMed1991

The muscle-sparing thoracotomy in infants and children.

Deformities of the chest wall, breast, shoulder girdle, and spine are well-documented sequelae of major thoracotomies that transect muscles, divide major motor nerves, resect ribs, or cause them to fuse. These deformities are probably aggravated by the growth process. This is why we make a plea for the routine use, in infants and children, of a muscle-sparing thoracotomy that will minimize these sequelae without sacrificing exposure. Major (lateral) thoracotomy by this technique involves these steps: (1) creating a transverse incision below the tip of the scapula, or a vertical axillary incision; (2) elevating the skin flaps to expose the muscles; (3) retracting the latissimus dorsi posteriorly; (4) retracting the serratus anterior and scapula superiorly; (5) disinserting the lower origins of the serratus if required only; (6) opening the desired intercostal space; (7) reapproximating the ribs without crowding, using a pericostal suture that is passed along the inferior rib subperiosteally, to avoid any compression on the neurovascular bundle; and (8) allowing the muscles to fall back into place, reattaching the serratus insertions as indicated. Lessened postoperative pain and improved respiratory function are additional benefits.

Child↗
PubMed1995

Effects of local muscle fatigue on three-dimensional scapulohumeral rhythm.

The relationship of scapulothoracic motion to glenohumeral motion, commonly referred to as the scapulohumeral rhythm, has been the subject of numerous investigations. The purpose of this study was to assess the effects of localized muscular fatigue on three-dimensional scapulothoracic motion and the resulting scapulohumeral rhythm during elevation of the humerus in the plane of the scapula. A six-degree-of-freedom digitizing system (Metrecom(TM)) was used to define scapular and trunk reference frames, and three-dimensional Eulerian angles were determined for scapular motion for 0-135 degrees of humeral elevation before and after fatigue of the upper and lower trapezius muscles. Local muscle fatigue was determined using spectral analysis of electromyographic signals for the upper and lower trapezius muscles. The results demonstrated an average of 22% decrease in the median frequencies of the muscles sampled following resistive exercise, suggesting a state of local muscle fatigue. Concomitant with the fatigue was a selective decrease in scapulothoracic motion about two of the three scapular axes. RELEVANCE: Occupational and recreational conditions often require repetitive overhead elevations of the arms, resulting in muscular fatigue and various pathologies. During repetitive arm elevations the scapulohumeral rhythm or synchronization between the humerus and the scapula is balanced to allow the most efficient elevation of the arm. A better understanding of this much-discussed scapulohumeral rhythm and the changes induced by muscular fatigue may provide insight into the pathomechanics associated with shoulder dysfunction.

Journal Article↗
PubMed1992

Surgical treatment of myeloma of bone.

33 patients treated operatively for plasma cell disease were analysed. There were 21 men and 12 women with an average age of 54 years. There was an undefined bone tumour in 23 cases, and a pathologic fracture in 10 cases. In only 6 cases was the diagnosis known before the operation. The primary tumour localisations were: vertebral column in 13, pelvis in 7, femur in 6, humerus in 2, rib in 1, tibia in 1, fibula in 1, scapula in 1 and olecranon in 1 case. 16 diagnostic biopsies were taken. Vertebral tumours were mainly evacuated or decompressed, combined with a stabilising procedure in 8 cases. A total of six endoprostheses, five to the femur and one to the humerus were performed. Two primarily wide resections, to the fibula and to the scapula were done. There were no locally recurring tumours during a mean follow-up time of 4 years and 2 months, and we conclude that operative and oncologic treatment is successful in providing the patient with a stable, pain-free locomotive system.

Adult↗
PubMed2006

Variations of the A. axillaris and the crural arteries in the same human individual--multiple repetitions of the mammalian plesiomorphic constellation of the arteries.

While dissecting the body of a 75-year-old female individual we observed "abnormal" patterns of the A. axillaris and the crural arteries which resembled the mammalian plesiomorphic constellation. In the right arm a large common trunk of the A. axillaris gave origin to the A. profunda brachii, the A. circumflexa humeri posterior, the A. circumflexa scapulae and the A. thoracodorsalis. In many other mammals including non-human primates, the Aa. circumflexae humeri and the A. circumflexa scapulae are connected via a third or fourth artery to a common trunk. Since the large common trunk mostly corresponded to the supply area of the A. axillaris, we consider it to be homologous to the distal part of the A. axillaris. In the left arm, except the A. circumflexa humeri posterior and the A. subscapularis which take off together, the other axillary branches showed the "normal" human pattern. In the right leg, the crural arteries exhibited the mammalian plesiomorphic constellation with an A. tibialis anterior ending in the crural extensor muscles, a rudimentary A. tibialis posterior, and a strongly developed A. peronea. In the left leg, the A. tibialis anterior supplied the Dorsum pedis and therefore represented the pattern normally seen in humans. However, in the left leg there also was a rudimentary A. tibialis posterior along with a prominent A. peronea.

Aged↗
PubMed2005

Suprascapular nerve block for shoulder arthroscopy.

The suprascapular nerve (SSN) originates from the C5 and C6 nerve roots and provides sensation for the posterior shoulder capsule, acromioclavicular joint, subacromial bursa, and coracoclavicular ligament. Blocking it provides pre-emptive anesthesia, decreased intraoperative pain, and postoperative pain relief in shoulder arthroscopy. Under general anesthesia, 25 mL of 0.5% bupivacaine is injected by a spinal needle placed 1 cm medial to the convergence of the spine and clavicle, angling toward the coracoid. At a depth of 3 to 4 cm, the needle strikes the scapula body. The surgeon probes with the needle anteriorly until the scapula is no longer felt, then moves the needle back posteriorly until the bone is felt again. This places the needle at the coracoid base in the supraspinatus fossa where the SSN curves around the coracoid and heads to the glenohumeral joint. At this point, the anesthetic is injected, "flooding" the SSN location. In addition to the SSN block, other pain-control procedures should be performed, including bupivacaine injection of all portals and an intra-articular injection of morphine sulfate at the end of the procedure. The SSN block is an effective technique and can reduce postoperative medication needs and allow earlier patient discharge from the surgery center.

Anesthetics, Local↗
PubMed2004

Normalization procedures using maximum voluntary isometric contractions for the serratus anterior and trapezius muscles during surface EMG analysis.

The serratus anterior and trapezius muscles are considered to be the only upward rotators of the scapula and are very important for normal shoulder function. A variety of methods have been used to produce a maximum voluntary isometric contraction (MVIC) of these muscles for normalization of EMG data. The purpose of this study was to quantify the surface EMG activity of the serratus anterior muscle and the upper, middle, and lower parts of the trapezius during 9 manual muscle tests performed with maximum effort in 30 subjects. It was found that no one muscle test produced a MVIC for all individuals. Therefore, to perform normalization within each subject, it is suggested that the 2 or 3 tests identified in this study that produce high levels of EMG activity for each muscle be performed. The scapular protraction muscle test that is often used to normalize data for the serratus anterior muscle produced relatively low levels of EMG activity and was not found to be an optimal test. Muscle tests in which an attempt was made to de-rotate the scapula from an upwardly rotated position produced much higher levels of EMG activity in the serratus anterior muscle.

Adult↗
PubMed2006

Metastatic squamous cell carcinoma in a cat.

A 7-year-old, spayed female Persian cat was referred for evaluation of progressive paraplegia. The cat was thin, cachectic and paraplegic on presentation. The survey radiographs showed a left caudal pulmonary lesion and lytic skeletal lesions at the right iliac crest and left distal scapula. Due to a poor prognosis for complete recovery, the owner opted for euthanasia. Post-mortem examination revealed bilaterally small and irregular kidneys, lysis of the left iliac crest and left distal scapula and a dilated left ventricular lumen with a thin interventricular septum. Histologically, all the lesions were determined to be squamous cell carcinoma. It appears that the origin or the primary site of the malignancy in this case is pulmonary as cardiac and skeletal tissues are primarily mesenchymal in origin and are less likely to develop a primary epithelial malignancy. To the best of our knowledge, there is no description of cardiac or skeletal metastatic squamous cell carcinoma in a cat.

Animals↗
PubMedDate not supplied

Use of three-dimensional computed tomography for the analysis of the glenoid anatomy.

Preoperative evaluation for a total shoulder arthroplasty includes 2-dimensional analysis of the glenoid through either standard radiographs or computed tomography (CT) images. Recent evidence suggests that these 2-dimensional images may actually misrepresent the 3-dimensional (3D) anatomy of the glenoid. Because 3D reconstructions of CT images allow 3D visualization and analysis of the scapula as a free body, we hypothesized that they can reflect the true anatomy of the glenoid more accurately. To test this hypothesis, we obtained various glenoid morphometric measurements from excised cadaveric scapulae as well as their respective 3D CT images. On average, the glenoid version angles measured from the 3D CT images were within 1.0 degrees +/- 0.7 degrees (mean +/- SD) of those from the actual specimen (95% confidence limit, <2.2 degrees for all observers). These measurements from the 3D CT images showed high interobserver and intraobserver reliability (interobserver and intraobserver correlation coefficients, 0.983 and 0.978, respectively). Similarly, measured glenoid surface width and length from the 3D CT images were within 1.8 +/- 1.2 mm and 1.4 +/- 1.1 mm, respectively, of those from the actual specimen. In addition, we were able to estimate the glenoid surface area as well as the glenoid vault volume from the 3D CT images. These values were 8.67 +/- 2.73 cm2 and 11.86 +/- 5.06 cm3, respectively. The mean glenoid vault volume with respect to its surface area was 1.35 +/- 0.24 cm3/cm2 (range, 1.06-1.91 cm3/cm2). These data suggest that 3D CT images can accurately reflect the true anatomy of the glenoid and that they can provide valuable information regarding the glenoid surface and vault. As such, 3D CT images may prove to be a useful tool during the preoperative evaluation for a total shoulder arthroplasty, particularly in patients with significant glenoid bone loss.

Anthropometry↗
PubMedDate not supplied

Grammont reverse prosthesis: design, rationale, and biomechanics.

Combined destruction of the rotator cuff and the glenohumeral joint may lead to a painful and pseudo-paralyzed shoulder. In this situation a nonconstrained shoulder prosthesis yields a limited functional result or may even be contraindicated. Previous constrained prostheses (ball-and-socket or reverse ball-and-socket designs) have failed because their center of rotation remained lateral to the scapula, which limited motion and produced excessive torque on the glenoid component, leading to early loosening. The reverse prosthesis designed by Paul Grammont, unlike any previous reverse ball-and-socket design, has introduced 2 major innovations that have led to its success: (1) a large glenoid hemisphere with no neck and (2) a small humeral cup almost horizontally oriented with a nonanatomic inclination of 155 degrees, covering less than half of the glenosphere. This design medializes and stabilizes the center of rotation, minimizes torque on the glenoid component, and helps in recruiting more fibers of the anterior and posterior deltoid to act as abductors. Furthermore, the humerus is lowered relative to the acromion, restoring and even increasing deltoid tension. The Grammont reverse prosthesis imposes a new biomechanical environment for the deltoid muscle to act, thus allowing it to compensate for the deficient rotator cuff muscles. The clinical experience does live up to the biomechanical concept: the reverse prosthesis restores active elevation above 90 degrees in patients with a cuff-deficient shoulder. However, external rotation often remains limited, particularly in patients with an absent or fat-infiltrated teres minor. Internal rotation is also rarely restored after a reverse prosthesis. Failure to restore sufficient tension in the deltoid may result in prosthetic instability. The design does appear to protect against early loosening of the glenoid component, but impingement of the humeral cup on the scapular neck can lead to scapular notching and polyethylene wear. This is a cause for concern, especially as the notch is often more extensive than can be explained by impingement alone. Bony lysis of the scapula may also be related to a polyethylene granuloma. Further follow-up is required to ensure that loosening does not become a problem in the long term, and it has been recommended to limit its use to elderly patients, arguably those aged over 70 years. Despite these concerns, the reverse prosthesis, based on the biomechanical Grammont concept, offers a true surgical option in several situations where only limited possibilities were previously available: cuff tear arthrosis, persistent shoulder pseudo-paralysis due to a massive and irreparable cuff tear, severe fracture sequelae, prosthetic revision in a cuff-deficient shoulder, and tumor surgery. Finally, surgeons must be aware that results are less predictable and complication/revision rates are higher in revision surgery.

Biomechanical Phenomena↗
PubMed2006

How to extend the elbow with a weak or paralyzed triceps: control of arm kinematics for aiming in C6-C7 quadriplegic patients.

This study aims to investigate how quadriplegic patients with a C6-C7 spinal lesion coordinate their upper limb to extend the elbow despite the paralysis or weakness of the triceps brachii, and what is the effect of a surgical musculotendinous transfer. For this purpose, aiming movements in a wide workspace were recorded in seven healthy subjects and in patients with incomplete (five cases) or complete (eight cases) triceps paralysis and after musculotendinous transfer (eight cases). We used four electromagnetic field sensors to quantify hand trajectory and to compute the angles describing the rotations at the scapula, glenohumeral joint, elbow and wrist (10 degrees of freedom). Extent and smoothness of the hand trajectories and hand velocity profiles were surprisingly similar between healthy subjects and quadriplegic patients. The reduction of elbow extension observed in patients was compensated by rotations distributed across several degrees of freedom including the scapula. Principal components analysis showed that the joint rotations could be summarized by an additive combination of two synergies, respectively orientating and stretching out the limb, which explained similar amounts of variance in healthy subjects and in patients. The participations of degrees of freedom in the synergies were roughly similar in the different groups of subjects, the main difference concerning scapular medial-lateral rotation, which seems to be critical in patients with a complete triceps paralysis. This demonstrates that elbow extension in quadriplegic patients is due to anticipated mechanical interaction coupling between upper limb segments. We propose that the persisting (incomplete paralysis) or restored (musculotendinous transfer) elbow extensor strength may act by stabilizing the elbow. This counterintuitive preservation of limb kinematics for horizontal aiming movements in quadriplegic patients despite the drastic changes in muscle action provoked by paralysis and/or by surgery strongly suggests that the motor system does not primarily control forces but the morphological aspects of movement, via joint rotation synergies.

Adult↗
PubMed2005

Ultrasonographic examination of important aspects of the bovine shoulder--physiological findings.

The left and right shoulder region of 19 healthy cattle and the left and right shoulders of six bovine cadavers were examined ultrasonographically using a 7.5 MHz linear and a 3.5 MHz convex transducer. The lateral shoulder muscles were successfully imaged in all cases; the joint space appeared as a funnel shaped interruption of the hyperechoic bone surfaces of the distal part of the scapula and the proximal and lateral part of the humeral head. In healthy cattle, the synovial cavities of the scapulohumeral joint, the bicipital bursa and the infraspinous bursa could not be clearly defined. After experimental filling with water, the synovial cavities could be differentiated as discrete anechoic zones. In this study, the normal ultrasonographic appearance of the soft tissue structures and bone surfaces of the scapula and proximal humerus is presented, providing basic reference data for the ultrasonographic evaluation of the bovine shoulder region.

Animals↗
PubMed2006

Postnatal allometry of the skeleton in Tupaia glis (Scandentia: Tupaiidae) and Galea musteloides (Rodentia: Caviidae)--a test of the three-segment limb hypothesis.

During the evolution of therian mammals, the two-segmented, sprawled tetrapod limbs were transformed into three-segmented limbs in parasagittal zig-zag configuration (three-segment limb hypothesis). As a consequence, the functional correspondence of limb segments has changed (now: scapula to thigh, upper arm to shank, fore arm plus hand to foot). Therefore, the scapula was taken into account in the current study of the postnatal growth of the postcranial skeleton in two small mammalian species (Tupaia glis, Galea musteloides). Comparisons were made between the functionally equivalent elements and not in the traditional way between serially homologous segments. This study presents a test of the three-segment limb hypothesis which predicts a greater ontogenetic congruence in the functionally equivalent elements in fore and hind limbs than in the serially homologous elements. A growth sequence, with decreasing regression coefficients from proximal to distal, was observed in both species under study. This proximo-distal growth sequence is assumed to be ancestral in the ontogeny of eutherian mammals. Different reproductive modes have evolved within eutherian mammals. To test the influence of different life histories on ontogenetic scaling during postnatal growth, one species with altricial juveniles (Tupaia glis) assumed to be the ancestral mode of development for eutherians and one species with derived, precocial young (Galea musteloides) were selected. The growth series covered postnatal development from the first successive steps with a lifted belly to the adult locomotory pattern; thus, functionally equivalent developmental stages were compared. The higher number of allometrically positive or isometrically growing segments in the altricial mammalian species was interpreted as a remnant of the fast growth period in the nest without great locomotor demands, and the clearly negative allometry in nearly all segments in the precocial young was interpreted as a response to the demand on early locomotor activity. Different life histories seem to have a strong influence on postnatal ontogenetic scaling; the effects of the developmental differences are still observable when comparing adults of the two species.

Aging↗