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PubMedDate not supplied

Effects of simulated scapular protraction on anterior glenohumeral stability.

We evaluated the effect of simulated scapular protraction on anterior glenohumeral translation and in situ inferior glenohumeral ligament strain. Five fresh-frozen cadaveric glenohumeral joints were tested in the position of apprehension while simulating scapular protraction using a custom translation testing device and a differential variable reluctance transducer. The results showed a statistically significant decrease in anterior glenohumeral translation as the scapula was increasingly rotated to simulate 20 degrees of scapular protraction. With 15 N of thorax-based, anteriorly directed load, the mean anterior translation was 6.3 +/- 1.6 mm (mean +/- SEM). With 10 degrees of simulated scapular protraction, translation decreased to 4.1 +/- 1.0 mm; with 20 degrees of simulated scapular protraction, it decreased further to 2.5 +/- 0.5 mm. For each of the other anteriorly directed loads, translations also decreased when 20 degrees of scapular protraction was simulated. Concurrently for each of the anteriorly directed loads, there was increased in situ strain of the anterior band of the inferior glenohumeral ligament with increased simulated scapular protraction. These results suggest that repetitive or chronic protraction of the scapula may result in excessive strain and, ultimately, insufficiency in the anterior band of the inferior glenohumeral ligament.

Biomechanical Phenomena↗
PubMed1979

Suprascapular entrapment neuropathy: a clinical, anatomical, and comparative study. Part 2: anatomical study.

Two hundred eleven adult scapulae were examined and quantitative data pertaining to the dimensions of the suprascapular notch were obtained. Six types of suprascapular notch were observed. Transitions tended to occur between Types II, III, and IV. A classification function was developed utilizing the measured values of the dimensions of the suprascapular notch, which might help in assigning the scapulae to these transitional types. Dissections of the suprascapular area were performed in 15 cadavers. Static and dynamic relationships of the suprascapular nerve to the suprascapular foramen were examined.

Adult↗
PubMed2006

Multiple roles of mesenchymal beta-catenin during murine limb patterning.

Recently canonical Wnt signaling in the ectoderm has been shown to be required for maintenance of the apical ectodermal ridge (AER) and for dorsoventral signaling. Using conditional gain- and loss-of-function beta-catenin alleles, we have studied the role of mesenchymal beta-catenin activity during limb development. Here, we show that loss of beta-catenin results in limb truncations due to a defect in AER maintenance. Stabilization of beta-catenin also results in truncated limbs, caused by a premature regression of the AER. Concomitantly, in these limbs, the expression of Bmp2, Bmp4 and Bmp7, and of the Bmp target genes Msx1, Msx2 and gremlin, is expanded in the mesenchyme. Furthermore, we found that the expression of Lmx1b, a gene exclusively expressed in the dorsal limb mesenchyme and involved in dorsoventral patterning, is reduced upon loss of beta-catenin activity and is expanded ventrally in gain-of-function limbs. However, the known ectodermal regulators Wnt7a and engrailed 1 are expressed normally. This suggests that Lmx1b is also regulated, in part, by a beta-catenin-mediated Wnt signal, independent of the non-canoncial Wnt7a signaling pathway. In addition, loss of beta-catenin results in a severe agenesis of the scapula. Concurrently, the expression of two genes, Pax1 and Emx2, which have been implicated in scapula development, is lost in beta-catenin loss-of-function limbs; however, only Emx2 is upregulated in gain-of-function limbs. Mesenchymal beta-catenin activity is therefore required for AER maintenance, and for normal expression of Lmx1b and Emx2.

Alleles↗
PubMed1978

Thoracoscapular fusion for facioscapulohumeral dystrophy.

Eleven thoracoscapular fusion operations have been done on six patients. The indication is symptomatic winging of the scapula caused by thoracoscapular muscle paresis with intact function in the deltoid. This situation almost exclusively occurs in facioscapulohumeral dystrophy. The operation is successful in achieving stability of the scapula and in greatly improving function and cosmesis. Although the course of this type of muscular dystrophy is variable, the benefits of operation have not deteriorated with progression of the disease over a maximum follow-up period of twenty-three years.

Adolescent↗
PubMed1985

Anterior capsular redundancy of the shoulder: congenital or traumatic? An embryological study.

A study of the attachment of the joint capsule to the scapula, and of the shape of the humeral head, has been carried out in 52 fetal and embryonic shoulders. In 77% of cases the anterior capsule was attached to the labrum or close to it; in the remaining 23% it was inserted into the neck of the scapula, so creating a pouch. In all 52 specimens the humeral head was spherical. It was concluded that the pouched and redundant anterior capsule sometimes seen during surgery for recurrent dislocation of the shoulder, may not be traumatic in origin, but could be a developmental variant.

Humans↗
PubMed1997

Perturbation of BMP signaling in somitogenesis resulted in vertebral and rib malformations in the axial skeletal formation.

Axial skeletons such as vertebrae, ribs, and scapulae develop from the embryonic somitic mesoderm through interactions with neural tube/notochord and skin ectoderm. Bone morphogenetic proteins (BMPs) seem to play important roles in these tissue interactions; however, the relationship between BMP signaling and the early development of axial skeletons is poorly understood. In this report, we investigated possible roles of BMP signaling in axial skeletal formation. First, we describe the expression patterns of BMP4 and type I receptors for BMP during somitogenesis in chick embryos based on whole mount in situ hybridization. Next, the effects of BMP on axial skeletal morphogenesis were investigated by implantation of BMP proteins into the dorsal mesoderm at the time of somitogenesis. Transcripts for both BMP4 ligand and its receptors are expressed in the dorsal ectoderm and mesoderm. Implantation of BMP4 and BMP2 into the dorsal regions of embryos result in subsequent anomalies of vertebrae, ribs, and scapulae. The effects of BMP implantation on the skeleton are shown to be dependent upon the somitic stage. Vertebral anomalies are restricted to the dorsolateral elements of the vertebrae and specifically observed after BMP implantation into embryonic day 2 (E2) embryos, but not E3 embryos. These results indicate that implantation of BMP into the dorsal part of embryos where endogenous BMP ligand and BMP receptors are expressed perturbs BMP signaling and causes axial skeletal malformations. The findings presented here suggest that BMP signaling may be involved in the early developmental process of the axial skeleton.

Amino Acid Sequence↗
PubMed1993

Bulk effect of rotator cuff on inferior glenohumeral stability as function of scapular inclination angle: a cadaver study.

Eleven fresh cadaver shoulders were studied to determine the static contribution (bulk effect) of the rotator cuff on inferior glenohumeral stability provided by scapular inclination. All musculature, including the rotator cuff, was removed. The position of the humerus relative to the scapula was recorded using an electromagnetic tracking device under conditions of no force and 1.5 kg of inferior translation force applied to the humerus, with the arm in the hanging position (sulcus test) and then in 90 degrees abduction (Abduction-Inferior Stability test = ABIS test), with the scapula inclined referable to the vertical line at -15 degrees, 0 degrees, 15 degrees and 30 degrees in the sulcus test and at 15 degrees, 30 degrees, 45 degrees and 60 degrees in the ABIS test. In the sulcus test without load, all shoulders dislocated at scapular inclination angles of -15 degrees and 0 degrees, whereas no shoulders dislocated at 30 degrees. The angle of scapular inclination had a significant effect on humeral head positions (p < 0.0001), with the head position at -15 degrees and 0 degree being lower than at 15 degrees, which was lower than at 30 degrees. In the ABIS test, none of the shoulders dislocated, although the effect of the angle of scapular inclination was significant (p < 0.0001), with the position of the humeral head being higher at 15 degrees than at other angles of inclination. Comparison of these data and previously reported data with the cuff intact showed no significant effect of rotator cuff removal on humeral head position and displacement in both tests. Therefore, we conclude that the static condition of the rotator cuff has no significant effect on the stabilizing function of scapular inclination. The stabilizing mechanism of scapular inclination seems to be associated with the bony configuration and/or anatomy and biomechanical properties of the superior capsuloligamentous structures.

Adult↗
PubMed1995

Posture in patients with shoulder overuse injuries and healthy individuals.

Assessment of posture is an integral component of patient evaluation with shoulder overuse injuries. However, the professional literature contains relatively few studies that have assessed the relationship between posture, function, and injury. The purpose of this study was to determine the relationship and differences in postural variables within and between subjects with overuse injuries to the shoulder of healthy subjects. Thirty patient subjects and 30 healthy subjects matched for age and gender were recruited. Scapular protraction and rotation, forward head position, midthoracic curvature, and passive humeral elevation in the plane of the scapula were measured randomly in standing. All measurement techniques were standardized and validated. Intrarater and interrater reliability for all clinical measures were established before data collection. Forward head position was significantly greater (p < .001) in the patient group than the healthy group; humeral elevation was significantly greater (p < .001) in the healthy group than in the patient group and in the uninvolved shoulders (p < .01) than the involved shoulders within the patient group. Scapular protraction, rotation, midthoracic curvature, and scapular symmetry were not significantly different between groups. Scapula protraction and rotation were significantly related (p < .05) in the patient group. No other postural variables were related. Conclusions regarding the influence of posture to shoulder injury are inconclusive based on several confounding variables that may have affected the outcome.

Adolescent↗
PubMed1996

Three-dimensional scapular orientation and muscle activity at selected positions of humeral elevation.

Abnormal scapular kinematics and associated muscle function presumably contribute to shoulder pain and pathology. An understanding of scapular kinematic and electromyographic profiles in asymptomatic individuals can provide a basis for evaluation of pathology. The purpose of this study was to describe normal three-dimensional scapular orientation and associated muscle activity during humeral elevation. Twenty-five asymptomatic subjects, 19-37 years old, were evaluated. Digitized coordinate data and surface electromyographic signals from the trapezius (upper and lower), levator scapulae, and serratus anterior were collected at static positions of 0, 90, and 140 degrees of humeral elevation in the scapular plane. The scapula demonstrated a pattern of progressive upward rotation, decreased internal rotation, and movement from an anteriorly to a posteriorly tipped position as humeral elevation angle increased. Electromyographic activity of all muscles studied increased with increased humeral elevation angles. Differences between mean values at all elevation angles for all variables were significant (p < .05), except for the lower trapezius between the 90 and 140 degrees humeral angles. The results of this study suggest assessment of scapular tipping and internal rotation as well as upward rotation may be necessary to understand pathologies of the shoulder that are related to abnormal scapular kinematics.

Adolescent↗
PubMed1997

An objective measurement technique for posterior scapular displacement.

Contemporary shoulder rehabilitation programs emphasize scapular control in the treatment of shoulder pathology. In addition, scapular winging and scapular tipping are often cited as key components to both the evaluative and rehabilitative phase of treatment. However, the lack of objective measurement procedures makes clinical evaluation of these phenomena difficult. The purpose of this project was to develop a reliable technique to quantify posterior scapular displacement (direction of scapular movement for winging and/or tipping). Forty healthy subjects (21 males, 19 females) who reported no current shoulder pain participated in this study. A measurement instrument was designed to quantify, to the nearest whole degree of motion, the posterior displacement of the inferior angle of the scapula from the posterior thorax. Subjects' scapulae were each measured two times without holding weight (unweighted position) and two times while the subjects held 10% of their body weight (weighted position). During all trials, two testers were blinded from the measurement readings. Intraclass correlation coefficients (ICC) were calculated based on a repeated measure analysis of variance to determine intertester and intratester reliability. The standard error of measurement (SEM) was used to determine the measurement error. Intratester within-day reliability ICCs ranged from 0.97 to 0.98, and SEM ranged from 0.6 to 1.1 degrees. Intertester within-day reliability ICCs ranged from 0.92 to 0.97, and SEM ranged between 1.1 and 1.7 degrees. None of the calculated p values for intratester and intertester reliability were statistically significant (p < 0.05). We conclude that this measurement technique is a reliable method to quantify posterior scapular displacement. Further research utilizing this measurement technique is recommended.

Adult↗
PubMed1998

Scapular avulsion fracture of a high school wrestler.

This case study details a rare injury managed conservatively with aggressive therapy with early return to competition. A 17-year-old high school wrestler suffered indirect trauma to the right upper extremity. The patient was forced to the mat where he felt pain in the posterior aspect of his shoulder and was point tender over the inferior pole of his right scapula. Radiographs reveal an avulsion fracture at the inferior angle of the scapula. Aggressive therapy included modalities to control inflammation and muscle guarding in addition to early scapular mobility. Maintenance of glenohumeral motion and upper extremity strengthening was started within a week. The patient was able to wrestle in the state tournament 3 weeks after initial injury. At the 6-month follow-up, the patient had no clinical tenderness, full range of motion, and no motor deficits. The outcome resulted in clinical and radiological healing of the fracture and no functional deficits.

Adolescent↗
PubMed2004

Comparing the function of the upper and lower parts of the serratus anterior muscle using surface electromyography.

STUDY DESIGN: Prospective single-group repeated-measures design. OBJECTIVE: To use electromyographic (EMG) analysis during muscle testing to determine if there is a difference in function of the upper and lower parts of the serratus anterior (SA) muscle. BACKGROUND: The SA muscle is a very important scapular protractor and upward rotator. Authors have anatomically described the muscle as being divided into 2 or 3 parts, and have suggested that the upper part is more suited for protraction and the lower part for upward rotation of the scapula. METHODS AND MEASURES: Surface electrodes recorded EMG activity of the upper and lower parts of the SA muscle during 9 different muscle tests in 29 healthy subjects. RESULTS: Three muscle tests demonstrated significantly greater (P<.05) EMG activity in the lower part of the SA as compared to the upper part. There was no significant difference in the EMG activity of the upper and lower parts of the SA when the other 6 muscle tests were analyzed. CONCLUSION: When upward rotation was the primary position of the scapula during the muscle tests, the lower part of the SA was activated to a greater degree than the upper part. Muscle tests with maximum scapular protraction with varying degrees of upward rotation produced EMG activity with no significant difference when comparing the upper and lower parts of the SA. This information may be helpful for clinicians when muscle testing and developing exercise programs for the SA muscle.

Adult↗
PubMed2006

Scapulothoracic and glenohumeral kinematics following an external rotation fatigue protocol.

STUDY DESIGN: Repeated-measures experimental design. OBJECTIVE: To determine the effects of shoulder external rotator muscle fatigue on 3-dimensional scapulothoracic and glenohumeral kinematics. BACKGROUND: The external rotator muscles of the shoulder are important for normal shoulder function. Impaired performance of these muscles has been observed in subjects with impingement syndrome and it is possible that external rotator muscle fatigue leads to altered kinematics of the shoulder girdle. METHODS AND MEASURES: Twenty subjects without a history of shoulder pathology participated in this study. Three-dimensional scapulothoracic and glenohumeral kinematics were determined from electromagnetic sensors attached to the scapula, humerus, and thorax. Surface electromyographic (EMG) data were collected from the upper and lower trapezius, serratus anterior, anterior and posterior deltoid, and infraspinatus muscles. Median power frequency (MPF) values were derived from the raw EMG data and were used to indicate the degree of local muscle fatigue. Kinematic and EMG measures were collected prior to and immediately following the performance of a shoulder external rotation fatigue protocol. RESULTS: After completing the fatigue protocol subjects demonstrated less external rotation of the humerus. Additionally, they had less posterior tilt of the scapula in the beginning phase of arm elevation, and more scapular upward rotation and clavicular retraction in the mid ranges of arm elevation. CONCLUSIONS: Performance of an external rotation fatigue protocol results in altered scapulothoracic and glenohumeral kinematics. Further studies are needed to investigate the effects of external rotator muscle fatigue on scapulothoracic and glenohumeral kinematics in subjects with shoulder pathology.

Adolescent↗
PubMed1986

Pedicled scapular apophysis transplantation. Growing grafts studied in dogs.

Twenty-eight immature dogs, divided into three groups, have been studied to determine the possibilities of pedicled epiphyseal transplantation from a rarely used donor site area, the scapula. One group of 8 immature dogs were studied anatomically using India ink and Batson's compound injection methods. We identified the vascular pattern of the diaphyseal portion of the graft, consisting of the lateral crest or border of the scapula. In two groups of 10 immature dogs, this area was used as a pedicled island graft to rebuild the semiresected or totally resected proximal humerus. There were marked differences between these two groups on the basis of morphologic, histologic, histochemical and electron microscopic aspects of the samples. Preservation of normal growth appeared to be directly related to the compressive forces applied to the graft. Preservation of the cartilage was also related to the biomechanical situation; fibrocartilage and signs of arthrosis were noted 1 year after the operation in several animals whose humeri had been fully subjected to normal stresses. Both the diaphyseal and epiphyseal areas had increased one- to fivefold in volume, but longitudinal growth was markedly deficient.

Animals↗
PubMed2004

The MRI features and treatment of scapulothoracic bursitis: report of four cases.

Among cases of soft tissue tumours arising between the inferior angle of the scapula and thoracic wall, scapulothoracic bursitis has rarely been reported. All the reported cases were surgically treated and there have been no reports about the results of conservative treatment observed for a long period. Therefore, we retrospectively evaluated the clinical findings, magnetic resonance imaging (MRI) features, and treatment procedures in order to elucidate the differential diagnosis for, and efficacy of, conservative treatment. The patients were those who consulted our department of orthopedic surgery from 1994 to 1998 with complaints of thoracic back tumours. The patients were 2 men and 2 women whose ages ranged from 46 to 66 years. The tumour locations, MRI findings and treatments were evaluated. The cysts appeared in the inferior angle of the scapula with the shoulder flexed and adducted. There was neither pain nor tenderness, local heat nor redness. The cysts were elastic hard, fluctuating, and less mobile and the margins were well circumscribed by palpation. The diameters were from 6 x 6 cm to 20 x 15 cm. On MR imaging, the cysts were located between the serratus anterior muscle and the chest wall. Slightly high signal intensity on T1WI, high on T2WI and fluid-fluid levels were seen in the cysts in three cases. For the treatment, in one case we performed multiple aspirations until a reduction appeared to occur. The average aspirated contents of the cyst were 100 mL to 200 mL and were bloody-serous. In two cases no special treatments were employed, and in one case the tumour was surgically removed because it was unresponsive to aspiration. In the three cases with conservative treatment, the follow-up time was 8, 9 and 25 months, respectively. The tumours had disappeared in all cases at the time of the final follow-up. High signal intensities on T1 and T2 weighted images, and fluid-fluid level on T2 weighted images were very useful MRI features for the diagnosis of scapulothoracic bursitis. Our observations indicate that conservative treatment can be successful and surgery is not necessary except for cases with pain, excessive friction, or dysfunction.

Adult↗
PubMed1991

Lateral parascapular extrapleural approach to the upper thoracic spine.

The upper thoracic vertebrae are difficult to approach surgically because of the narrowing of the thoracic inlet, the proximity of the brachial plexus, and the parascapular shoulder musculature. A novel lateral parascapular extrapleural approach to the upper thoracic vertebrae is described. The parascapular shoulder musculature (trapezius, levator scapulae, and rhomboid muscles) is reflected off the spinous processes to the scapula as a musculocutaneous flap, preserving the neurovascular supply. The paraspinal musculature is mobilized and retracted, and the upper dorsal ribs are removed with caution to avoid injury to the C-8 and T-1 nerve roots. The rami communicantes are transected, and the sympathetic chain is displaced anterolaterally. The T2-4 vertebrae can be approached unobstructed. The T-1 nerve root obstructs posterolateral access to the T-1 vertebra, necessitating an inferolateral approach underneath the T-1 nerve root axilla. Four patients with compressive myelopathy from upper thoracic vertebral metastases underwent neural decompression, vertebral reconstruction, and posterior spinal fixation with this approach. Their postoperative neurological status was either unchanged or improved. Complications included radiographic pleural effusion and superficial wound dehiscence; one patient required posterior spinal reinstrumentation for progressive kyphosis. One patient developed pneumonia 7 days postoperatively which was unresponsive to appropriate treatment. It is believed that the anatomical limitations to this region have been overcome, and that excellent exposure of the T1-4 vertebrae for neural decompression and vertebral reconstruction can be performed safely. A major advantage is that posterior spinal fixation can be carried out simultaneously.

Female↗
PubMed2005

Surgical anatomy of the dorsal scapular nerve.

OBJECT: There is a paucity of literature regarding the surgical anatomy of the dorsal scapular nerve (DSN). The aim of this study was to elucidate the relationship of this nerve to surrounding anatomical structures. METHODS: Ten formalin-fixed human cadavers (20 sides) were dissected, and measurements made between the DSN and related structures. The nerve pierced the middle scalene muscle at a mean distance of 3 cm from its origin from the cervical spine and was more or less centrally located at this exit site. It lay a mean distance of 1.5 cm medial to the vertebral border of the scapula between the serratus posterior superior, posterior scalene, and levator scapulae muscles. It was found to have a mean distance of 2.5 cm medial to the spinal accessory nerve as it traveled on the anterior border of the trapezius muscle. The nerve intertwined the dorsal scapular artery in all specimens and was found along the anterior border of the rhomboid muscles. On 19 sides the DSN originated solely from the C-5 spinal nerve, and on one side it arose from the C-5 and C-6 spinal nerves. CONCLUSIONS: Knowledge of the anatomy of the DSN will aid the surgeon who wishes to explore and decompress this structure.

Accessory Nerve↗
PubMed2003

Toward standardized procedures for recording and describing 3-D shoulder movements.

Movements of the human upper extremity are difficult to measure, due to the specific structure of the limb. All arm movements are a combination of movements of the humerus relative to a moveable base: the scapula. Measurement of movements is, however, strongly hampered by the fact that the scapular movement is difficult to track when skin-based landmarks are used. A second complicating factor is the fact that a skin-based proximal landmark on the humerus is difficult to define, which directly affects attempts to describe accurately the movements of that segment. To solve these problems, special measurement procedures have been developed, which include the identification of landmarks for the scapula and the humerus and recording procedures for segment movements or the estimation of landmarks. Also, a definition of the three-dimensional description of motion is presented. These measurement procedures have now been applied in several experiments and have been proven to be successful.

Biomechanical Phenomena↗