Infraspinous Fossa Research Articles

The effects of hypermuscularity on shoulder morphology in myostatin-deficient mice

Mechanical loads, particularly those generated by skeletal muscle, play a significant role in determining long-bone shape and strength, but it is less clear how these loads influence the morphology of flat bones like the scapula. While scapular morphology has been shown to vary with locomotor mode in mammals, this study seeks to better understand whether genetically modified muscle size can influence scapular shape in the absence of significant locomotor differences. The soft- and hard-tissue morphological characteristics were examined in 11 hypermuscular, mutant (myostatin-deficient), 20 heterozygote, and 15 wild-type mouse shoulders. Body mass did not significantly differ among the genotype groups, but homozygous mutant and heterozygote mice had significantly larger shoulder muscles than wild-type mice. Mutant mice also differed significantly from the wild-type controls in several aspects of scapular size and shape, including glenohumeral joint orientation, total scapular length, superior border length, and supraspinous and infraspinous fossa length. Conversely, several traits describing superoinferior scapular breadth measures (e.g. total breadth and dorsal scapular fossa breadth) did not significantly differ between mutant and wild-type mice. Since the intrinsic musculature of the scapula is oriented in a mediolateral fashion, it follows that mediolaterally configured hard-tissue features like scapular length were most distinct among genotype groups. As had been noted previously with long bones, this study demonstrates that genetically enhanced muscle size has marked effects on the morphological characteristics of the shoulder.

Anatomical basis of the vascular risk related to the circumflex scapular artery during posterior approach to the scapula

The vasculature and anastomosis around the scapula is extremely intricate making surgical treatment complicated. We aimed to determine the "at risk area" for the circumflex scapular artery and its anastomosis with the suprascapular artery during posterior approach to the scapula. Sixteen shoulders from eight embalmed adult cadavers were dissected through posterior approach to the scapula to study the relationship of the circumflex scapular artery and its anastomosis with the suprascapular artery to bony landmarks of the posterior scapula. Three measurements were obtained: from inferior glenoid rim to the point of the bony groove of the circumflex scapular artery; from the posterior glenoid rim to the spinoglenoid notch; and from the spinoglenoid notch to the circumflex scapular artery. The circumflex scapular was identified at a distance of 2.9 cm from the inferior glenoid rim and at a distance of 4.6 cm from the spinoglenoid notch, as it winds around the lateral border of the scapula to enter the infraspinous fossa. The suprascapular neurovascular bundle was identified at the spinoglenoid notch 1.8 cm from the posterior glenoid rim. We were able to identify the relationship of the circumflex scapular artery to the anatomic landmarks of the scapula and to define the "at risk area" for the ascending branch of the circumflex scapular artery and its anastomosis with the suprascapular artery. We believe our anatomical study may aid in the avoidance of vascular complications during internal fixation of scapular fractures.

Functional categorization of the individual morphology of the scapula

The morphologic variations of the shoulder blade have not yet been evaluated in clinical medicine. We observed that subjects with less standard shapes of the shoulder blade often suffer from musculo-skeletal shoulder syndromes with concurrent intrinsic impingement syndromes or, more precisely, partial-thickness rotator cuff tears. This experience became a basis for an experiment, in which we categorized individual phenotypes of the shoulder blade. A clinically useful finding of the presented study is a tool for predicting patients at risk for manifestations of impingement syndrome and also for prediction of easy or complicated restoration of neuromuscular stabilization of the shoulder. Lower functional potential of the external rotator muscles of the shoulder is in close relation to the individual shape of the shoulder blade, for the most part with the cranio-caudal dimension of the infraspinous fossa.

Use of autologous scapula for cranioplasty: cadaveric feasibility study

Replacement sources for calvarial defects include synthetic materials, donor grafts, and autologous bones such as ribs or split-thickness calvarial cranioplasty. When these sources are not available or are inadequate, other structures or sites would be desirable. However, and to our knowledge, the scapula has not been explored as a potential source for calvarial reconstruction. Therefore, the following study was performed to verify the utility of this bone for cranioplasty. Six adult (mean age 71 years) cadavers (four formalin-fixed and two fresh specimens) were used in this study. In the prone position, an incision was made over the midpart of the infraspinous fossa. Soft tissues were then removed from the anterior and posterior aspects of the scapula in this region avoiding the glenohumeral articulation superiorly. Previously made cranial defects were then filled using available scapula as a bony replacement. An average of 9 x 12 x 7 cm of scapula was available for harvest inferior to the glenohumeral joint. Lateral and medial borders of the scapula were found to have a mean thickness of 9 mm. No obvious injury to surrounding vessels or nerves was found using this procedure and good coverage of calvarial defects was afforded by this bony replacement. Such a bony substitute as autologous scapula might be of utility when other replacements are not available or are of a limited size. Examples of such a use would include patients in whom a hemispheric bone flap is lost. Following clinical confirmation, the neurosurgeon may wish to consider the scapula as an alternative site for bone harvest for cranioplasty as this was a feasible technique in the cadaver.

Postcranial anatomy of Haldanodon exspectatus (Mammalia, Docodonta) from the Late Jurassic (Kimmeridgian) of Portugal and its bearing for mammalian evolution

The postcranium of the Late Jurassic docodont Haldanodon exspectatus Kuhne & Krusat, 1972 is represented by a partial skeleton and isolated bones of other individuals from the Late Jurassic (Kimmeridgian) of the Guimarota coal mine in Portugal. Haldanodon exhibits adaptations for a fossorial lifestyle such as stout and short limb bones and humeri with greatly expanded distal joints and strong deltopectoral crests. Short first and second phalanges and moderately curved and laterally compressed terminal phalanges with lateral grooves suggest that Haldanodon was a scratch-digger. The dorso-ventrally elongated, triangular scapula has a convex transverse profile with strongly laterally reflected anterior and posterior scapula margins, enclosing a deep trough-like ‘infraspinous fossa’. A supraspinous fossa is not developed. The saddle-shaped glenoid facet is mainly formed by the coracoid and orientated antero-ventrally indicating a sprawling gait. No epiphyses were detected and the wide size range of humerus and femur possibly indicate a lifelong growth. Haldanodon is more derived than Morganucodon by complete reduction of the procoracoid, absence of the procoracoid foramen, and a peg-like coracoid. It shares with monotremes a postscapular fossa that is absent in Morganucodon . A PAUP analysis based on 280 cranio-dental and postcranial characters corroborated the position of Haldanodon above morganucodontids and below Hadrocodium . © 2005 The Linnean Society of London, Zoological Journal of the Linnean Society , 2005, 145 , 219‐248.

Unusual Metastasis of Malignant Aortic Body Tumor to <i>Multiple</i> Bones in a Dog

Unusual metastasis of malignant aortic body tumor to multiple bones was detected in a 5-year-old female English Setter dog. Radiographs exhibited an abnormal mass in the base of heart and osteolytic lesions in the bodies of T11 and L2 vertebrates, body of right femur, right proximal humoral epiphysis and infraspinous fossa near to the neck of right scapula. At necropsy, multiple tumor masses of various sizes were observed also in the bones as well as the heart base and tracheobronchial lymph node. Tumor masses of L2 and T11 protruded into the vertebral canal and compressed corresponding sites of spinal cord, leading to paraplegia. Histopathologically, the tumor cells, arranged in sheets or nests, were polyhedral, lightly eosinophilic, finely granular cytoplasm with mostly round to oval nucleus and had scattered bizarre giant cells. Ultrastructural study revealed the characteristic findings that tumor cells contained a large number of small, electron-dense, membrane-limited secretory granules in cytoplasm. This is thought to be an extremely rare case having multiple bone metastases of a malignant aortic body tumor.

Load transfer across the scapula during humeral abduction

Stress analysis in the individual parts of the scapula under normal physiological conditions is necessary to understand the load transfer mechanism, its relation with morphology of bone and to analyse the deviations in stress patterns due to implantation of the glenoid. The purpose of this study was to obtain stress distribution in the scapula during abduction of the arm and to obtain a qualitative estimate of the function of coracoacromial ligament. An accurate three-dimensional (3D) finite element (FE) model of the natural scapula has been developed for this purpose, using computed tomography data and shell-solid modelling approach. The model was experimentally validated. A musculoskeletal shoulder model of forces that calculates all muscle, ligament and joint reaction forces, in six load cases (30–180°) during unloaded humeral abduction was used as applied loading conditions for the 3D FE model. High tensile and compressive stresses (15–60 MPa) were generated in the thick bony ridges of the scapula, like the scapular spine, lateral border, glenoid and acromion. High compressive stresses (45–58 MPa) were evoked in the glenoid and at the connection of glenoid-scapular spine-infraspinous fossa. The stresses in the infraspinous fossa and supraspinous fossa were low (0.05–15 MPa). These results indicated that the transfer of major muscle and joint reaction take place predominantly through the thick bony ridges, whereas the fossa area act more as attachment sites of large muscles. During humeral abduction, coracoacromial ligament was stretched, and presumably will be under tension.

Load transfer across the scapula during humeral abduction

Stress analysis in the individual parts of the scapula under normal physiological conditions is necessary to understand the load transfer mechanism, its relation with morphology of bone and to analyse the deviations in stress patterns due to implantation of the glenoid. The purpose of this study was to obtain stress distribution in the scapula during abduction of the arm and to obtain a qualitative estimate of the function of coracoacromial ligament. An accurate three-dimensional (3D) finite element (FE) model of the natural scapula has been developed for this purpose, using computed tomography data and shell-solid modelling approach. The model was experimentally validated. A musculoskeletal shoulder model of forces that calculates all muscle, ligament and joint reaction forces, in six load cases (30–180°) during unloaded humeral abduction was used as applied loading conditions for the 3D FE model. High tensile and compressive stresses (15–60 MPa) were generated in the thick bony ridges of the scapula, like the scapular spine, lateral border, glenoid and acromion. High compressive stresses (45–58 MPa) were evoked in the glenoid and at the connection of glenoid-scapular spine-infraspinous fossa. The stresses in the infraspinous fossa and supraspinous fossa were low (0.05–15 MPa). These results indicated that the transfer of major muscle and joint reaction take place predominantly through the thick bony ridges, whereas the fossa area act more as attachment sites of large muscles. During humeral abduction, coracoacromial ligament was stretched, and presumably will be under tension.

Ontogenesis of the scapula in marsupial mammals, with special emphasis on perinatal stages of didelphids and remarks on the origin of the therian scapula.

The development of the scapula was studied in embryonic and postnatal specimens of Monodelphis domestica and perinatal specimens of Philander opossum, Caluromys philander, and Sminthopsis virginiae using histological sections and 3D reconstructions. Additionally, macerated skeletons of postnatal M. domestica were examined. This study focused on the detachment of the scapulocoracoid from the sternum and on the acquisition of a supraspinous fossa, a supraspinatus muscle, and a scapular spine, all these events associated with the origin of the therian shoulder girdle. In none of the specimens is there a continuity of the cartilaginous scapulocoracoid with the sternum, even though the structures are in close proximity, especially in S. virginiae. At birth, the first rib laterally presents a pronounced boss that probably contacts the humerus during certain movements. Only the acromial portion of the scapular spine, which originates from the anterior margin of the scapular blade, is preformed in cartilage. The other portion is formed by appositional bone ("Zuwachsknochen"), which expands from the perichondral ossification of the scapula into an intermuscular aponeurosis between the supra- and infraspinous muscles. This intermuscular aponeurosis inserts more or less in the middle of the lateral surface of the developing scapula. Thus, the floor of the supraspinous fossa is present from the beginning of scapular development, simultaneously with the infraspinous fossa. The homology of the therian spine with the anterior border of the sauropsid and monotreme scapula is questioned. We consider the dorsal portion (as opposed to the ventral or acromial portion) of the scapular spine a neomorphic structure of therian mammals.

Ontogenetic data and the evolutionary origin of the mammalian scapula.

One of the most useful diagnostic therian features is the division of the lateral surface of the scapula into two fossae separated by a scapular spine. A new model to describe this evolutionary innovation based on ontogenetic data is provided, consistent with information provided by recent fossil discoveries. The development of the scapula in three didelphid and one dasyurid marsupials using histological sections was studied. Only the ventral, acromial portion of the scapular spine, which originates from the anterior margin of the scapular blade, is preformed in cartilage. The major dorsal portion is formed at a later stage by appositional bone, which expands from the perichondral ossification of the scapula into an intermuscular aponeurosis between the supra-and infraspinatus muscles. This intermuscular aponeurosis inserts more or less in the middle of the lateral surface of the developing scapula. Thus, the floor of the supraspinous fossa is already present at the beginning of scapular development, simultaneous with the infraspinous fossa. The portion of the scapular spine that is situated dorsal to the acromial process is hypothesized to be a neomorphic structure of therians. The dorsal portion of the scapular spine evolved as additional attachment for powerful supraspinatus and infraspinatus muscles meeting near the middle of the lateral scapula.

Scapula form and biomechanics in gorillas.

Gorillas are generating renewed interest as mounting evidence from field and molecular studies strongly suggests the western lowland (Gorilla gorilla gorilla) and eastern mountain (Gorilla gorilla beringei) gorillas are considerably more distinct than has previously been accepted. Schultz (1927, 1930, 1934) was one of the earliest investigators to document morphological differences between the two groups, noting differences in pedal, limb and scapular morphology. These differences led Schultz to conclude that while lowland gorillas retained some features suited to an arboreal habitat, the mountain gorilla had evolved into a specialized terrestrial quadruped. In particular, he noted that mountain gorillas exhibited lower values for the scapular index, higher values for ratios of infraspinous fossa vs. scapula length and spine length vs. scapula length and variability in the extent of curvature of the vertebral border. However, Schultz' observations were based upon small sample sizes of mostly adult specimens. This study extends Schultz' preliminary work by assessing, with appreciably larger sample sizes, patterns of relative growth of the scapula in these two subspecies of Gorilla. Scapula measurements were obtained for ontogenetic series of G.g. gorilla (n = 366) and G. g. beringei (n = 43). Statistical analyses reveal mountain gorillas exhibit significantly (P < 0.05) greater spine lengths and scapula breadths and smaller scapula lengths than lowland gorillas of comparable superior border lengths. However, at comparable body weights, mountain gorillas exhibit significantly shorter spines and superior borders than lowland gorillas. These differences in scapula proportions are evaluated in the context of biomechanical predictions regarding scapula form and locomotion.

Effects of ontogeny and sexual dimorphism on scapula morphology in the mountain gorilla (Gorilla gorilla beringei).

Scapular measurements were obtained from growth series of the sexually dimorphic mountain gorilla (Gorilla gorilla beringei). Juveniles, subadults, and adults were compared to determine if scapula morphology varies with age. Analyses reveal significant (P < 0.05) differences in scapula form for shape ratios of length vs. breadth, length vs. infraspinous fossa length, and length vs. spine length. Males and females were also compared to determine if sexual dimorphism in scapula morphology is a consequence of differential extension of common patterns of relative growth. Analyses reveal that scapula proportions are ontogenetically scaled. Data indicate that male scapulae grow at a faster rate and for a longer duration than females. Results of comparisons of males and females suggest that unique adaptations to different ecological niches have not evolved between the sexes despite sexual differences in frequency of patterns of locomotor behavior. By contrast, age-related variation in scapula morphology may be linked to differences in locomotor behavior during ontogeny.

Infraspinatus muscle-splitting incision in posterior shoulder surgery. An anatomic and electromyographic study.

Standard posterior shoulder surgical approaches include infraspinatus tendon detachment and infraspinatus-teres minor interval development. Cadaveric and clinical investigation of a new infraspinatus-splitting approach to the posterior glenohumeral joint was undertaken to assess efficacy in providing exposure, preserving tendon attachment, and avoiding neurologic compromise. Infraspinatus musculotendinous and neural anatomy was examined in 20 cadavers. Four patients with posterior shoulder instability underwent posterior capsulorrhaphy through this infraspinatus-splitting approach, followed by electrodiagnostic testing. Infraspinatus muscle was bipennate in all specimens, the tendinous interval an average 14 mm inferior to the scapular spine at the glenoid rim. The infraspinatus-splitting interval bisected the posterior glenoid rim at its midpoint, whereas the infraspinatusteres minor interval crossed the glenoid rim's lower quarter. The suprascapular nerve provided sole innervation to the infraspinatus muscle in all specimens, entering the infraspinous fossa at the notch as a single trunk 22 mm medial to the glenoid rim. Minimum branching variability was observed. Electrodiagnostic testing showed no evidence of axonal damage or muscle denervation in either infraspinatus pennate bundle. Limiting infraspinatus-splitting dissection medially to 1.5 cm from the posterior glenoid rim prevents damage to any interval-crossing suprascapular nerve branches. Posterior shoulder surgery through a horizontal, longitudinal infraspinatus tendon-splitting approach provides excellent exposure of posterior capsule, labrum, and glenoid, without requiring tendon detachment or causing neurologic compromise.

Muscular attachments along the medial border of the scapula.

The authors described in this report the mode of attachments of muscles along the medial border of the scapula, as seen in sixty adult Indians. The levator scapulae, rhomboideus major and minor muscles comprise of double folds at the scapular end. The posterior folds of the levator scapulae and the rhomboideus minor muscles were attached to the dorsal surface of the medial border of the bone opposite the supraspinous fossa and the root of the spine respectively, while their anterior flaps gained attachment on the costal surface of the border at the level of the root of the scapular spine. The latter muscle reached much lower than the former. The rhomboideus major muscle was attached on the medial border of the scapula opposite the infraspinous fossa and could be traced to the dorsal surface of the bone just above the inferior angle. All the three muscles overlapped the costal surface of the serratus anterior fascia for about three centimeters. The fasciae of the muscles merged with each other along a straight line joining the free margins of their costal flaps. The serratus anterior muscle surrounds the superior and inferior angles of the scapula and is thus attached to both the surfaces of the bone at these sites.

Reparo à origem (Insertio scapularis) do M. teres minor em bovinos

The bovine’s teres minor muscle was dissected in 32 thoracic limbs in order to study its origin (Insertio scapularis). Its arises from the inferior limit of the proximal fourth to the middle of the caudal border of the scapula and from two oblique muscular imprinties of the infraspinous fossa. Sex, age and breed seem not to influence the anatomical disposition of the teres minor muscle.

Reparo à origem (Insertio scapularis) do M. teres minor no cavalo

The horse's teres minor muscle was dissected in 26 thoracic limbs in order to study its origin (insertio scapularis). It arises from the middle proximal fourth of the caudal border of the scapula and from an oblique muscular imprint of the infraspinous fossa. The second origin, in line and continuous with the first, reaches the level of the scapular neck. Sex, age and breed seems not to influence the anatomical disposition of the teres minor muscle.

Repair of Injured Bones in Muskrat and Striped Skunk

While processing specimens in the collection of mammals at the University of Museum of Natural History, I noted injuries to bones of two muskrats, Ondatra zibethicus, and a striped skunk, Mephitis mephitis. One of the muskrats, an adult of unknown sex (KU 6624), was obtained in eastern Kansas on 23 November 1927, and was given to the Museum by C. W. Ogle. In this specimen the right scapula (Fig. 1) has a truncated infraspinous fossa and a roughened projection along the axilliary border The remainder of the skeleton is normal. Application of the head of the right humerus to the fossa for its reception indicated that locomotion was unimpeded. The second muskrat, an adult male (KU 72880), was obtained by J. R. Alcorn on 21 February 1957, 10 miles north-northeast of Stillwater, Churchill Co., Nevada. From a recessed area on the ventral surface of the left side of the mandible three openings into a cavity that contained an abscess are visible (Fig. 2). Another opening of comparable size is situated in a pit on the medial side of the bone five millimeters below the alveolar lip for the first molar. The jaw is swollen ventrally. A cut or a bite inflicted by another animal possibly exposed the dentary to infiltrating bacteria, which attacked the bone tissue. The skunk, an adult male (KU 91400), was taken by A. B. Mickey on 1 December 1948 at Laramie, Albany Co., Wyoming. An irregular bridge of bone connects the zygomatic arch with the postorbital process