Demonstration of the appearance of the paraspinal musculoligamentous structures of the cervical spine using ultrasound

The application of ultrasound in the imaging of the neck has primarily focussed on anterior structures (e.g., thyroid gland). Structures located on the posterior aspect of the neck have received little attention. This study illustrates the capability of modern ultrasound equipment in visualising the musculoligamentous structures of the neck, particularly the paraspinal musculature. Ten healthy adult volunteers (6 female; 4 male) underwent ultrasound examination of the cervical spine. A standardised technique for transducer placement was adopted and successive images of the neck of each subject were obtained. Spatial compound (extended field of view) images were obtained in subjects using one of two different ultrasound systems. Images of structures produced by ultrasound were compared to those achieved with magnetic resonance imaging in three subjects. Identification of key landmarks aided orientation and identification of structures. The internal architecture of the musculoligamentous structures of the cervical spine, especially the posterior neck muscles, was demonstrated well using ultrasound. Our study showed that modern ultrasound equipment is capable of producing clear images of the posterior cervical spine musculature and certain bony features.     

Magnetic resonance imaging study of cross-sectional area of the cervical extensor musculature in an asymptomatic cohort

Magnetic Resonance Imaging (MRI) can be regarded as the gold standard for muscle imaging; however there is little knowledge about in vivo morphometric features of neck extensor muscles in healthy subjects and how muscle size alters across vertebral segments. It is not known how body size and activity levels may influence neck muscle cross-sectional area (CSA) or if the muscles differ from left and right. The purpose of this study was to establish relative CSA (rCSA) data for the cervical extensor musculature with a reliable MRI measure in asymptomatic females within a defined age range and to determine if side-side and vertebral level differences exist. MRI of the cervical spine was performed on 42 asymptomatic female subjects within the age range of 18-45. The rCSA values for the cervical extensor muscles were measured from axial T1-weighted images. We found significant side-side rCSA differences for the rectus capitis posterior minor, major (P < 0.001), multifidus (P = 0.002), and the semispinalis cervicis/capitis (P = 0.001, P < 0.001). There were significant vertebral level differences in rCSA of the semispinalis cervicis/capitis, multifidus, splenius capitis, and upper trapezius (P < 0.001). Activity levels were shown to impact on the size of semispinalis cervicis (P = 0.027), semispinalis capitis (P = 0.003), and the splenius capitis (P = 0.004). In conclusion, measuring differences in neck extensor muscle rCSA with MRI in an asymptomatic population provides the basis for future study investigating relationships between muscular atrophy and symptoms in patients suffering from persistent neck pain. Clin.     

Scalenus muscles in macaque monkeys

The attachment and innervation of the scalenus muscles in both sides of two Japanese monkeys and a rhesus monkey were observed to discuss their morphological significance while comparing their findings in humans. The scalenus ventralis muscle in macaques had almost the same attachments as the scalenus anterior muscle in humans and was innervated by the cervical nerve branches, which were lower in spinal segment than in humans and had a close relationship with the branches to the intertransversus ventralis muscles. Furthermore, the scalenus ventralis muscle was penetrated by the phrenic nerve in all cases observed. The posterior part of the scalenus muscle in macaques (the scalenus dorsalis muscle) was divided into short (the scalenus dorsalis brevis) and long (the scalenus dorsalis longus) parts according to their attachments. The former was attached to the transverse processes of the lowest two cervical vertebrae and the first rib, whereas the latter was attached to the 3rd-5th ribs. It is notable that the scalenus dorsalis muscles in macaques were innervated by branches from the long thoracic nerve in addition to direct branches from the cervical nerve roots. In addition, the scalenus dorsalis longus was supplied by twigs from the lateral cutaneous branches of the 2nd and 3rd intercostal nerves. This indicates that the scalenus dorsalis muscles contain a muscular component derived from the upper limb girdle musculature, unlike the human scalenus muscles, which have been considered to belong to the cervical trunk muscles.     

Three muscles in the upper costovertebral region: Description and clinical anatomy

The aim of the study was to describe three small muscles in the upper costovertebral region that have close proximity to the ventral rami of the lower cervical and upper two thoracic spinal nerves. The study was performed using both anterior and posterior approaches to the costovertebral region. Twenty‐five human cadavers, 15 males and 10 females with a mean age of 50 years and with normal spines, constituted the material of the study. Dissection revealed the presence of three triangular muscles that extended from the transverse processes of the seventh cervical through second thoracic vertebrae to the upper borders of the necks of the first through third ribs, respectively. The second and third muscles are described and reported for the first time. The ventral rami of the lower cervical and upper two thoracic spinal nerves emerged through narrow gaps between the described muscles and the bodies of seventh cervical and upper two thoracic vertebrae, respectively. The lateral branch of the dorsal ramus of the corresponding spinal nerve issued posteriorly between the muscle and the articular capsule of the zygapophyseal joint. It then curved round the posterior aspect of the muscle and passed through the gap between the muscle and the levator costarum, after supplying them both. We suggest that these three muscles were suggested to share a common embryogenesis with the intertransverse muscles. In addition, this study suggests that the three muscles described herein could be one of the potential causes of thoracic outlet syndrome. Clin. Anat. 22:352–357, 2009. © 2009 Wiley‐Liss, Inc.     

Structural and functional anatomy of the neck musculature of the dog (Canis familiaris)

The morphometric properties and the anatomical relationships of the entire musculature of the canine cervical spine are reported herein. These data were obtained from the dissection of cadavers of six dogs. Total muscle length, muscle weight, fascicle length and angles of pennation were recorded for each muscle comprising the canine cervical spine. Based upon these properties, physiological cross-section area (PCSA) and architectural index were estimated. When scaled by whole body mass, the values of each of these parameters were found to be similar between all dogs. Muscles that course from the cranial neck to the shoulder girdle or the rib cage (e.g. brachiocephalicus and rhomboideus capitis) were found to have relatively long fascicles and low PCSA values and thus appear to be designed for rapid excursions. By contrast, muscles that primarily support the neck and shoulder against gravitational forces (e.g. serratus ventralis and trapezius) were found to have relatively high PCSA values and short fascicle lengths, and thus have the capacity to generate large forces. Differences of morphometry as well as nomenclature were found between the canine and human neck musculature. Nevertheless, many similarities exist; in particular, both species have similar muscles adapted to force generation or large excursions. We thus conclude that the canine neck may be used as a modelling tool for biomechanical investigations of the human cervical region as long as the differences listed are borne in mind.     

Insight into understanding the anatomical and clinical aspects of supernumerary rectus capitis posterior muscles

Rectus capitis posterior muscles are located in the suboccipital triangle and function in extension and lateral rotation of the head and neck. There are two of these muscles on each side: the rectus capitis posterior major and the rectus capitis posterior minor. This study describes the presence of a third suboccipital muscle in a 55-year-old cadaver. In addition to highlighting the possible relationship between these muscles and cervicogenic headaches or balance in an individual, we also relate this observation to similar musculature in the cat that have been shown to effect crucial functions.     

Cervical vertebral body growth and emergence of sexual dimorphism: a developmental study using computed tomography

The size and shape of human cervical vertebral bodies serve as a reference for measurement or treatment planning in multiple disciplines. It is therefore necessary to understand thoroughly the developmental changes in the cervical vertebrae in relation to the changing biomechanical demands on the neck during the first two decades of life. To delineate sex‐specific changes in human cervical vertebral bodies, 23 landmarks were placed in the midsagittal plane to define the boundaries of C2 to C7 in 123 (73 M; 50 F) computed tomography scans from individuals, ages 6 months to 19 years. Size was calculated as the geometric area, from which sex‐specific growth trend, rate, and type for each vertebral body were determined, as well as length measures of local deformation‐based morphometry vectors from the centroid to each landmark. Additionally, for each of the four pubertal‐staged age cohorts, sex‐specific vertebral body wireframes were superimposed using generalized Procrustes analysis to determine sex‐specific changes in form (size and shape) and shape alone. Our findings reveal that C2 was unique in achieving more of its adult size by 5 years, particularly in females. In contrast, C3–C7 had a second period of accelerated growth during puberty. The vertebrae of males and females were significantly different in size, particularly after puberty, when males had larger cervical vertebral bodies. Male growth outpaced female growth around age 10 years and persisted until around age 19–20 years, whereas females completed growth earlier, around age 17–18 years. The greatest shape differences between males and females occurred during puberty. Both sexes had similar growth in the superoinferior height, but males also displayed more growth in anteroposterior depth. Such prominent sex differences in size, shape, and form are likely the result of differences in growth rate and growth duration. Female vertebrae are thus not simply smaller versions of the male vertebrae. Additional research is needed to further quantify growth and help improve age‐ and sex‐specific guidance in clinical practice.     

Sonographic studies of human soleus and gastrocnemius muscle architecture: gender variability

The purpose of this study was to establish if there are gender differences in muscle architecture in relaxed human soleus and gastrocnemius muscles of normal, live subjects. Ultrasonography was used to measure fiber bundle length, muscle thickness, and angles of pennation in a total of ten predetermined sites in the medial and lateral heads of gastrocnemius and the anterior and posterior soleus in 19 males and 16 females. Percentage differences between males and females for each parameter were recorded. Gender differences were statistically analyzed using multivariate analysis of variance. In the gastrocnemius and soleus muscles of males and females the differences between the overall fiber bundle length, angle of pennation and muscle thickness were statistically significant (P < 0.05). Overall, females were found to have longer average muscle fiber bundle length and males thicker muscles and larger angles of pennation. The greatest percentage differences of the architectural parameters between males and females were in the posterior soleus: 13% difference in fiber length and 26% difference in angle of pennation in the midline of posterior soleus and 26% difference in muscle thickness of the lateral part of posterior soleus. No correlation was found between leg length and fiber length, angle of pennation or muscle thickness. Fiber length (decreased), angle of pennation (greater) and muscle thickness (greater) of most parts of the gastrocnemius and soleus muscles were significantly different in males and females. Leg length of males and females did not correlate to these architectural parameters. Accepted: 18 February 2000     

Kinematics of the freely moving head and neck in the alert cat

 In this study we examined connections between the moment-generating capacity of the neck muscles and their patterns of activation during voluntary head-tracking movements. Three cats lying prone were trained to produce sinusoidal (0.25 Hz) tracking movements of the head in the sagittal plane, and 22.5o and 45o away from the sagittal plane. Radio-opaque markers were placed in the cervical vertebrae, and intramuscular patch electrodes were implanted in five neck muscles, including biventer cervicis, complexus, splenius capitis, occipitoscapularis, and rectus capitis posterior major. Videofluoroscopic images of cervical vertebral motion and muscle electromyographic responses were simultaneously recorded. A three-dimensional biomechanical model was developed to estimate how muscle moment arms and force-generating capacities change during the head-tracking movement. Experimental results demonstrated that the head and vertebrae moved synchronously, but neither the muscle activation patterns nor vertebral movements were constant across trials. Analysis of the biomechanical model revealed that, in some cases, modification of muscle activation patterns was consistent with changes in muscle moment arms or force-generating potential. In other cases, however, changes in muscle activation patterns were observed without changes in muscle moment arms or force-generating potential. This suggests that the moment-generating potential of muscles is just one of the variables that influences which muscles the central nervous system will select to participate in a movement. Received: 27 August 1996 / Accepted: 18 December 1996     

Feedforward activity of the cervical flexor muscles during voluntary arm movements is delayed in chronic neck pain

The objective of this study was to compare onset of deep and superficial cervical flexor muscle activity during rapid, unilateral arm movements between ten patients with chronic neck pain and 12 control subjects. Deep cervical flexor (DCF) electromyographic activity (EMG) was recorded with custom electrodes inserted via the nose and fixed by suction to the posterior mucosa of the oropharynx. Surface electrodes were placed over the sternocleidomastoid (SCM) and anterior scalene (AS) muscles. While standing, subjects flexed and extended the right arm in response to a visual stimulus. For the control group, activation of DCF, SCM and AS muscles occurred less than 50 ms after the onset of deltoid activity, which is consistent with feedforward control of the neck during arm flexion and extension. When subjects with a history of neck pain flexed the arm, the onsets of DCF and contralateral SCM and AS muscles were significantly delayed (p<0.05). It is concluded that the delay in neck muscle activity associated with movement of the arm in patients with neck pain indicates a significant deficit in the automatic feedforward control of the cervical spine. As the deep cervical muscles are fundamentally important for support of the cervical lordosis and the cervical joints, change in the feedforward response may leave the cervical spine vulnerable to reactive forces from arm movement.     

Age dependent changes in cervical region of the spine according to data of nuclear magnetic tomography

Morphological characteristics of spine cervical region were studied in 132 patients (62 female and 70 male) aged 12-76 years using magnetic resonance tomography. The imaging was performed with the use of T1 and T2--weighting regimes. The study revealed sex- and age-dependent differences in the dimensions of cervical vertebrae. Height and sagittal dimensions of vertebral bodies were significantly smaller in females than in males. With advancing age the reduction in vertebral body height was more expressed in women, while the increase of vertebral body sagittal dimensions was similar in both males and females. The sagittal dimension of vertebral canal was correlated with sagittal dimension of vertebral body (r = 0.69) in males and with transverse dimension of vertebral body (r = 0.82) in females. The data obtained should be taken into consideration during evaluation of the state of bony structures of cervical vertebrae, intervertebral discs and in the diagnosis of pathological processes in the spine cervical region.     

Alterations in cervical muscle activity in functional and stressful tasks in female office workers with neck pain

This study determined differences between computer workers with varying levels of neck pain in terms of work stressors, employee strain, electromyography (EMG) amplitude and heart rate response to various tasks. Participants included 85 workers (33, no pain; 38, mild pain; 14, moderate pain) and 22 non-working controls. Work stressors evaluated were job demands, decision authority, and social support. Heart rate was recorded during three tasks: copy-typing, typing with superimposed stress and a colour word task. Measures included electromyography signals from the sternocleidomastoid (SCM), anterior scalene (AS), cervical extensor (CE) and upper trapezius (UT) muscles bilaterally. Results showed no difference between groups in work stressors or employee strain measures. Workers with and without pain had higher measured levels of EMG amplitude in SCM, AS and CE muscles during the tasks than controls (all P < 0.02). In workers with neck pain, the UT had difficulty in switching off on completion of tasks compared with controls and workers without pain. There was an increase in heart rate, perceived tension and pain and decrease in accuracy for all groups during the stressful tasks with symptomatic workers producing more typing errors than controls and workers without pain. These findings suggest an altered muscle recruitment pattern in the neck flexor and extensor muscles. Whether this is a consequence or source of the musculoskeletal disorder cannot be determined from this study. It is possible that workers currently without symptoms may be at risk of developing a musculoskeletal disorder.     

Association between cervical lordotic curvature and cervical muscle cross‐sectional area in patients with loss of cervical lordosis

Disruption of the cervical lordotic curve can cause undesirable symptoms such as neck pain, and cord compression. The purpose of this study was to investigate the biomechanics of loss of cervical lordosis by measuring the cross‐sectional area (CSA) of the cervical muscles using magnetic resonance imaging (MRI), and to determine the relationship between cervical lordosis angle and cervical muscle status. The cervical lordosis angle was measured on standing lateral plain radiography using the posterior tangent technique in patients who complained of neck pain. The CSAs of the cervical flexor muscles including the longus cervicis and longus capitis, the cervical extensor muscles including the splenius capitis and semispinalis capitis, and the sternocleidomastoid muscle, were measured at the maximum levels by axial T1‐weighted MRI. We compared neck muscle CSAs between the two groups, the correlation with cervical lordosis angle, and muscle status including CSA and imbalance. The CSA of the semispinalis capitis was significantly lower in the loss of cervical lordosis group, and the ratio of cervical flexor to extensor was significantly different between the two groups (P < 0.05). Partial correlation analysis revealed that the cervical lordotic angle was significantly positively correlated with the ratio of flexor to extensor muscle CSAs (P < 0.05). There is a significant relationship between cervical muscle imbalance, including extensor muscle weakness, and loss of cervical lordosis. An exercise program focusing on cervical extensor muscle strengthening and restoring the balance of flexor and extensor muscles is recommended for patients with loss of cervical lordosis. Clin. Anat. 31:710–715, 2018. © 2018 Wiley Periodicals, Inc.     

Sex difference in target seeking behavior of developing cremaster muscles and the resulting first visible sign of somatic sexual differentiation in marsupial mammals.

Cremaster muscles are present in both male and female developing and adult marsupial mammals. They are complex structures and composed of several distinct bundles of striated muscle fibers provided with: (1) a distinct and extensive innervation; (2) a distinct blood vascular supply; (3) a distinct tendineous origin on the anterosuperior iliac spine; and (4) distinct target structures. The muscles thus seem to be separate anatomical entities and not a part of one or more of the layers of the ventral abdominal wall musculature. Cremaster muscles in males are elongated, are larger than in females, and for the most part are a component of the funiculus spermaticus. They insert on the distal part of the tunica vaginalis. The distal parts of the muscles in females are flattened ("fan shaped") and insert over a broad area on the dorsal borders of the mammary glands. Muscles in males have no relation whatsoever to the male mammary glandular rudiments. Muscles in females are attached at the base of the uterine round ligament. The remarkable sex difference in target structures of marsupial cremaster muscles becomes noticeable during perinatal life when outgrowing muscles take a different path in males and females. The initial appearance of this sexually dimorphic trait precedes the sexual differentiation of the genital ducts and external genitalia. In fetal males, the cremaster muscles grow in the direction of the site where scrotal bulges initially appear in the subcutaneous layers and later on the inguinal skin surface. They also take the gubernacular core of the ventral abdominal wall and the attached peritoneal epithelium with them during this outgrowth process. Consequently, this results in the development of a slitlike evagination of the abdominal lumen as the primary step to development of the processus vaginalis, while the testis and adjacent mesonephros and its duct are still attached to the posterior abdominal wall. In fetal females, the outgrowing cremaster muscles pass along the gubernacular core and, subsequently, this structure develops further as the tip (attached to the tubo-uterine junction) of the intra-abdominally protruding and further developing uterine round ligament. The female cremaster muscles grow further into caudal direction to shape a dorsal border of the developing mammary glands. The early onset of this sexually dimorphic outgrowth of cremaster muscles indicates that the "classical hormones" of sexual differentiation (anti-Müllerian hormone [AMH] and steroidal androgens) are not involved in this process. It could thus depend on primary genetic control with male development associated with the male-limited activity of genes on the Y-chromosomes and female development as the default process. Alternatively, the process in males could be under the control of an as yet unidentified third fetal testicular hormone involved in sexual differentiation processes which must then show an unexpectely early (i.e., perinatal) onset of its secretion.     

A three-dimensional finite element model of the cervical spine: an investigation of whiplash injury

Very few finite element models of the cervical spine have been developed to investigate internal stress on the soft tissues under whiplash loading situation. In the present work, an approach was used to generate a finite element model of the head (C0), the vertebrae (C1–T1) and their soft tissues. The global acceleration and displacement, the neck injury criterion (NIC), segmental angulations and stress of soft tissues from the model were investigated and compared with published data under whiplash loading. The calculated acceleration and displacement agreed well with the volunteer experimental data. The peak NIC was lower than the proposed threshold. The cervical S- and C-shaped curves were predicted based on the rotational angles. The highest segmental angle and maximum stress of discs mainly occurred at C7–T1. Greater stress was located in the anterior and posterior regions of the discs. For the ligaments, peak stress was at anterior longitudinal ligaments. Each level of soft tissues experienced the greatest stress at the time of cervical S- and C-shaped curves. The cervical spine was likely at risk of hyperextension injuries during whiplash loading. The model included more anatomical details compared to previous studies and provided an understanding of whiplash injuries.     

Triceps brachii muscle demonstrating a fourth head

Variations of the triceps brachii muscle are apparently rare. We report an additional attachment site of the medial head of the triceps brachii found on the left side of a male cadaver. This head originated from the posterior aspect of the surgical neck of the humerus. Clinicians diagnosing or treating patients with weakness or pain of the posterior arm should consider anomalous muscles in this region that may result in neurovascular compression.     

Vertebral orientations and muscle activation patterns during controlled head movements in cats

The focus of these experiments was to determine the relationships between head movement, neck muscle activation patterns, and the positions and movements of the cervical vertebrae. One standing cat and one prone cat were trained to produce voluntary sinusoidal movements of the head in the sagittal plane. Video-opaque markers were placed on the cervical vertebrae, and intramuscular patch electrodes implanted in four muscles of the head and neck. Cinefluoroscopic images of cervical vertebral motion and electromyographic responses were simultaneously recorded. Analysis of the spinal movement revealed that the two cats used different strategies to keep their heads aligned with the tracker. In the standing cat, vertebral motion described a more circular arc, compared to a forward diagonal in the prone cat. Intervertebral motion was limited, but more acute angles appeared between the vertebrae of the prone lying than of the standing animal. Data revealed that the central nervous system could control several axes of motion to keep the cervical spine matched to the moving stimulus. Phase relations between the sinusoidal motion of the vertebral column, peak activation of the neck muscles, and that of the stimulus were examined, and several different control strategies were observed both between and within animals. The results suggest that the central nervous system engages in multiple strategies of musculo-skeletal coordination to achieve a single movement outcome.     

The musculature of the mouse tail is characterized by metameric arrangements of bicipital muscles

This is the first report, to our knowledge, of the full characterization of the musculature of the mouse tail. Bicipital muscles form a major part of the tail musculature. The tail tendons originate with fusiform muscle from the dorsal and ventral lumbo-sacro-coxal regions and are inserted into the coccygeal vertebrae (extrinsic muscles of the tail). Each coccygeal vertebra has short muscles that terminate on the adjacent vertebrae (intrinsic muscles of the tail). The short muscle and its corresponding tail tendon are joined, thereby forming a bicipital muscle that is inserted into the coccygeal process. A geographical correspondence is strictly maintained between the origin of the tendon in the lumbo-sacro-coxal region and the insertion of the bicipital muscle in the coccygeal vertebrae. In other words, the organization of the tail musculature is based upon repetitions of fusion between the extrinsic and intrinsic muscles at each coccygeal vertebral level. This design is referred to as the metameric arrangement of the bicipital muscles. The organization, arrangement and function of muscles in the tail have features in common with those muscles in the digits of the human extremities.     

Variety,sex and ontogenetic differences in the pelvic limb muscle architectural properties of leghorn chickens (Gallus gallus domesticus) and their links with locomotor performance

Leghorn (layer) chickens (Gallus gallus domesticus) differ in locomotor morphology and performance due to artificial selection for standard (large) and bantam (small) varieties, sexual dimorphisms and ontogenetic stage. Here, the hind limb skeletal muscle architectural properties of mature and juvenile standard breeds and mature bantams are compared and linked to measures of locomotor performance. Mature males possessed greater relative muscle physiological cross‐sectional areas (PCSAs) than their conspecific females, indicative of greater force‐generating capacity, and in line with their greater maximum sustainable speeds compared with females. Furthermore, some of the relative fascicle lengths of the pennate muscles were greater in mature males than in mature females, which may permit greater muscle contractibility. Immature standard leghorns, however, did not share the same dimorphisms as their mature forms. The differences in architectural properties between immature and mature standard males indicate that with the onset of male sexual maturity, concomitant with increasing muscle mass in males, the relative fascicle lengths of pennate muscles and the relative PCSAs of the parallel‐fibred muscles also increase. The age‐related differences in standard breed male muscle architecture are linked to the presence and absence of sex differences in maximum aerobic speeds. Males of bantam and standard varieties shared similar muscle proportions (% body mass), but exhibited intrinsic muscle differences with a tendency for greater force‐generating capabilities in bantams and greater contractile capabilities in standards. The metabolic costs associated with the longer fascicle lengths, together with more crouched limbs in standard than in bantam males may explain the lack of allometry in the minimum metabolic cost of transport between these birds of different size.