Anatomy review – the torso, lower limbs and feet

Chapter 3 Anatomy review – the torso, lower limbs and feet

CHAPTER CONTENTS

Thoracic cage 78

Vertebral column 81

Pelvic girdle 83

Hip joint 86

Knee joint 89

Ankle joint and foot 90

THORACIC CAGE

BONES AND JOINTS

The walls of the thoracic cage comprise the thoracic vertebral column posteriorly and the sternum anteriorly, with the ribs and costal cartilages ranged between (Fig. 3.1).

Figure 3.1 A Joints of the thorax. B Movements of the sternum during respiration (seen laterally).

Reproduced with permission from Palastanga et al (2002).

The sternum comprises three distinct parts: the body with the manubrium attached superiorly and the xiphoid process attached inferiorly. It connects with the ribs through the flexible hyaline costal cartilages.

The costal cartilages of the first to the seventh ribs articulate with the sternum itself. The cartilages of the eighth, ninth and tenth ribs are inserted into the seventh costal cartilage so as to join the sternum. The cartilages of the eleventh and twelfth so-called ‘floating ribs’ are just caps on their anterior ends. These cartilages act to increase the flexibility of the anterior thoracic cage, particularly in the lower region where the cartilages of the eighth, ninth and tenth ribs merge and attach to the costal cartilage of the seventh rib, as described above.

MOVEMENTS OF THE RIBS, COSTAL CARTILAGES AND STERNUM

Main joints of the thoracic cage

The thoracic intervertebral joints and the articulations between the ribs and the vertebral column lie posteriorly, whilst anteriorly are the manubriosternal and xiphisternal joints, the sternocostal joints between the costal cartilages of the first to the seventh ribs and the sternum, and the interchondral joints between the tips of the cartilages of the eighth to the tenth ribs and their successive proximal cartilages.

The thoracic vertebral articulations include secondary cartilaginous joints and synovial joints, and the articulations between the ribs and the bodies and transverse processes of the thoracic vertebrae at both the costovertebral and costotransverse joints.

The costovertebral joints are formed by the two facets on each side of the head of the rib articulating with the sides of two adjacent thoracic vertebral bodies, and the costotransverse joints are formed by the tubercle of the rib articulating with the transverse process of its adjacent vertebra.

Joint movement

A limited range of movement is possible at both the costovertebral and costotransverse joints, but they allow only small gliding and twisting motions during inspiration and expiration. However, because of the length of the ribs these small posterior joint movements are amplified into much greater excursions in the lateral and anterior areas of the chest wall during breathing.

The manubriosternal and xiphisternal joints are secondary cartilaginous joints between the body of the sternum, manubrium and xiphoid process. Both allow a small range of movement during breathing.

The sternocostal joints lie between the costal cartilages of the first to the seventh ribs and the sternum. The first sternocostal joint is a primary cartilaginous joint that prevents significant movement between the rib and the sternum. The other six joints are synovial joints that allow gliding motions between the articular surfaces of the costal cartilages and the sternum required during breathing.

The eighth and ninth interchondral joints are synovial and allow small gliding motions for increased rib mobility, while the tenth interchondral joint, being fibrous, is relatively fixed.

The movements of the ribs, sternum and diaphragm increase and decrease the volume of the thoracic cage to produce the breathing cycle.

During inspiration, the upper ribs move their anterior ends upwards, the manubriosternal joint bends slightly allowing the sternal body to move forwards and upwards with the upper ribs, the lower ribs move outwards and upwards and the diaphragm moves downwards. This increases the dimensions of the thoracic cage and its enclosed lungs. The subatmospheric pressure thereby created between the thoracic cavity and the atmosphere causes air to be drawn into the lungs.

During passive expiration the ribs and sternum descend, and the diaphragm relaxes and ascends, returning the thoracic cage and the lungs to their normal size. This revives the pressure gradient between the lungs and the outside environment and air is expelled from the lungs.

‘Pump’ and ‘bucket handle’ rib action

During breathing the second to the fifth ribs move up and down with almost no lateral displacement and their action is considered to be like a pump drawing water from a well, a so-called ‘pump’ action.

In contrast, the anterior ends of the eighth to the tenth ribs shift laterally as they move up and down towards the horizontal, and their action is considered to be more like raising a handle from the side of a bucket, a so-called ‘bucket handle’ action.

Whilst the intermediate ribs (the sixth and seventh) demonstrate both ‘pump’ and ‘bucket handle’ actions, the first, eleventh and twelfth ribs are not that involved in increasing the volume of the thoracic cage.

MUSCLES INVOLVED IN BREATHING

Inspiration	Expiration
Diaphragm	Transversus abdominis
Scalenes	Internal obliques
Intercostals	External obliques
Levatores costarum	Latissimus dorsi
Serratus posterior superior	Transversus thoracis
	Subcostals
	Serratus posterior inferior

Inspiration

The diaphragm is a dome-shaped musculotendinous leaf separating the thoracic and abdominal cavities (Fig. 3.2). It has several major points of origin around its circumference: the xiphoid process; the deep surfaces and cartilages of the seventh to the twelfth ribs; the lumbar vertebrae via the ‘right crus’ and ‘left crus’, ligaments that arise from the bodies of the lumbar vertebrae L1–L3 and L1–L2, respectively; and the arcuate ligaments that attach to the lumbar vertebrae.

Figure 3.2 A The left levatores costarum, and the right serratus posterior superior and inferior muscles, posterior view. B The left transversus thoracis muscle on the inner surface of the thoracic cage.

Reproduced with permission from Palastanga et al (2002).

Its insertion is unlike that of any other muscle as it does not attach to bone but to its own central tendon, a strong, interlacing arrangement of fibrous tissue. The central tendon contains an opening to transmit the vena cava and there are other openings for the descending aorta and the oesophagus.

In normal breathing the dome-shaped diaphragm contracts and its central tendon descends to increase the capacity of the thoracic cage and produce inspiration. It then relaxes and controls the rate at which air is expelled from the recoiling lungs during expiration.

In forced expiration as occurs during coughing and sneezing, the abdominal muscles contract and increase intra-abdominal pressure as the diaphragm relaxes. This pushes the abdominal contents against the diaphragm, thereby increasing its upward displacement as it ascends. This increase in its upward motion further reduces lung volume and forces air from the lungs.

The external, internal and innermost intercostal muscles lie between adjacent ribs in three separate layers. Although there is controversy about the active role of these muscles during breathing (some of the external intercostal muscles possibly assist elevation of the rib below), together they help to maintain the tone and integrity of the intercostal spaces and chest wall during breathing.

Levatores costarum are short, strong muscles lying on each side of the spine between the seventh cervical and eleventh thoracic vertebrae. They attach superiorly to the transverse process of one vertebra and inferiorly to the upper border of a rib one or two levels below. They assist rib elevation during breathing and can also help to produce rotation and lateral flexion of the spine.

Serratus posterior superior lies deep to the rhomboids and the muscle fibres attach diagonally from the sides of the spinous processes of the seventh cervical, first, second and third thoracic vertebrae to the second, third, fourth and fifth ribs, respectively. It assists rib elevation during breathing.

Expiration

Transversus thoracis lies behind the sternum and ribs in the anterior thoracic wall. The muscle fibres originate from the posterior surface of the xiphoid process and lower region of the sternum and run superolaterally to attach to costal cartilages of the second to the sixth ribs. When transversus thoracis contracts, it pulls on the costal cartilages and lowers those ribs to assist expiration.

The subcostals are muscle slips found mainly in the thoracic region lying between the ribs across two intercostal spaces. They assist in lowering the ribs and producing expiration.

‘Serratus posterior inferior lies deep to latissimus dorsi, arising from the spinous processes T11, T12, L1 and L2 and their supraspinous ligaments via the thoracolumbar fascia. It helps to pull the lower four ribs downwards and backwards’ (Palastanga et al 2002, p. 483).

The muscles of the anterior abdominal wall are very important during breathing as they act with the diaphragm to alter the volume and internal pressures of the thoracic and abdominal cavities.

In normal breathing

During inspiration the abdominal muscles relax and reduce intra-abdominal pressure, allowing the diaphragm to lower as it contracts.

During expiration the abdominal muscles passively contract and increase intra-abdominal pressure, assisting the diaphragm’s upwards motion as it relaxes.

In forced expiration

The abdominal muscles actively contract and further increase intra-abdominal pressure as the diaphragm relaxes. This pushes the abdominal contents against the diaphragm, increasing its upward displacement as it ascends. This in turn increases intrathoracic pressure that forcefully compresses and deflates the lungs.

Forced expiration, and breath holding that activates the abdominal muscles whilst anchoring the diaphragm, both have a stabilizing and protective effect on the spine, and these breathing patterns may be used unconsciously to prepare for or during heavy lifting or similar strenuous activities.

VERTEBRAL COLUMN

See anatomical body charts on page xii.

BONES AND JOINTS

The vertebral column comprises 24 mobile vertebrae: 7 cervical, 12 thoracic and 5 lumbar; and 9 fused vertebrae; 5 in the sacral region forming the sacrum and 4 in the coccygeal region forming the coccyx.

The intervertebral joints occur from between the first and second cervical vertebrae, called the atlas and axis, respectively, to the lumbosacral junction between the fifth lumbar and first sacral vertebrae, the latter forming the base of the triangular sacral bone. Finally, the sacrococcygeal joint links the fifth sacral vertebra at the apex of the sacral bone with the coccyx. The joint between the skull and the first cervical vertebra (the atlas) is called the atlanto-occipital joint and that between the atlas and the second cervical vertebra (the axis) is called the atlantoaxial joint. These two specialized cervical vertebral joints are designed to allow the head to nod and to turn from side to side.

The intervertebral discs separating the vertebrae account for approximately one-quarter of the length of the vertebral column and function as shock absorbers during everyday activities, particularly walking and running.

The adult vertebral column has four curvatures: anterior convexities in the cervical and lumbar regions called lordoses and anterior concavities in the thoracic and sacrococcygeal regions called kyphoses. These curves, together with the intervertebral discs, give the vertebral column its pliancy, and an ability to absorb axial compressive forces and thereby provide a flexible support for the trunk.

MOVEMENTS OF THE VERTEBRAL COLUMN AND THE MAIN MUSCLES INVOLVED

Cervical spine

Flexion and extension

The total range of movement in the lower cervical region is about 25 degrees of flexion and 85 degrees of extension, and the least mobile joint is between the last cervical and first thoracic vertebrae.

To control flexion from the upright position, the postvertebral neck muscles (trapezius, splenius capitis, longissimus capitis, semispinalis capitis) and most of the small suboccipital muscles act bilaterally against the weight of the head.

To flex the head from the supine position the sternocleido-mastoid, longus capitis and the short muscles between the atlas and occiput (the suboccipital muscles) contract bilaterally.

The atlanto-occipital joint between the occipital condyles of the skull and the first cervical vertebra allows a total range of approximately 20 degrees of movement. Flexion and extension, together with a slight rotational motion, occur as the occipital condyles slide on the lateral masses of the atlas; full rotation occurs at the atlantoaxial joint.

Lateral flexion, rotation and circumduction

Lateral flexion of the neck is initiated by muscle action on that side and is then limited by the opposing articular facets, intervertebral disc compression and the flexibility of the contralateral cervical facet joint capsules.

Lateral flexion at the atlanto-occipital joint is limited to some 8 degrees and occurs as the occipital condyles move against the atlas. The axis moves against the third cervical vertebra so that the atlantoaxial joint is not specifically involved in lateral flexion.

In the lower cervical region the total range of movement is about 40 degrees of lateral flexion to each side and this is accompanied by a slight degree of rotation towards the flexed side. This occurs as the shape and orientation of the cervical articular facets prevent pure lateral flexion.

In rotation the skull and first cervical vertebra move as one unit and, with the head beginning erect, approximately 15 degrees of movement to each side may be achieved. As the head turns, it nods slightly on top of the spine and the chin drops minimally. This adjustment occurs as a result of the oblique orientation of the lateral joint surfaces and the slight convexity of the facets on the axis. If the head is tilted slightly backwards and away from the motion as the head turns, the range of rotation may be increased. The suboccipital sterno-cleido-mastoid and trapezius muscles produce rotation.

Circumduction combines flexion, extension, lateral flexion and rotation, and involves the whole array of deep and superficial neck muscles.

Thoracic spine

Flexion and extension

In the thoracic spine the total range of movement is between 50 and 70 degrees. Overall the thoracic spine is more mobile in flexion, as extension is limited by the impact of the articular and spinous processes between adjacent vertebrae as well as the tension in the anterior longitudinal ligament. Also, flexion is much freer in the lower thoracic spine due to the length and comparative flexibility of the lower ribs.

The postvertebral muscles pay out bilaterally so as to control flexion from the upright position; from the supine position the muscles of the anterior abdominal wall – in particular, rectus abdominis and the obliques – bring about flexion.

The anterior abdominal wall muscles control extension from the upright position; from the supine position extension occurs through postvertebral muscle action.

Psoas major and the anterior abdominal wall muscles control extension from the upright position whilst the postvertebral muscles produce extension from the prone position.

Lumbar spine

Flexion and extension

The lumbar spine is relatively free in flexion, its total range of movement being approximately 55 degrees. In extension the range of movement is approximately 30 degrees.

Flexion from the upright position is controlled by the postvertebral muscles on both sides being limited by tension in the posterior part of the intervertebral disc, the posterior longitudinal ligament, the ligamenta flava, and the inter- and supraspinous ligaments.

From the supine position the concentric bilateral actions of psoas major and the muscles of the anterior abdominal wall – in particular, rectus abdominis and the obliques – produce flexion.

Psoas major and the anterior abdominal wall muscles control extension from the upright position; from the prone position the postvertebral muscles, assisted by quadratus lumborum contracting bilaterally, produce it. Quadratus lumborum also assists lateral stability as the lumbar spine extends (Palastanga et al 2002, p. 512).

Thoracic and lumbar spine

Lateral flexion and rotation

The ranges of motion in both the thoracic and lumbar spine, as in the cervical spine, vary greatly between individuals and change with age, the ranges of motion being greatest in childhood and adolescence and possibly reducing by as much as 50% by the time an adult reaches 30 years of age.

Lateral flexion is greatest when in the upright position and is reduced when the normal curves of the spine are diminished (as when sitting) or reversed (as in spine flexion and extension). In addition, spine mobility in rotation is compromised and possibly lost when the normal spinal curves are reversed as in spine extension.

Lateral flexion is initiated by the concentric muscle action of anterior abdominal wall muscles and the quadratus lumborum on the side of flexion, and then controlled by the eccentric muscle action of those same muscles on the opposite side. The eccentric muscle action of the opposing side begins at about 10 degrees of lateral flexion.

The spinal muscles can also produce lateral flexion, erector spinae contracting unilaterally to produce lateral flexion with rotation to the side of the contraction and multifidus producing lateral flexion as well as extension and rotation at all levels of the vertebral column. Additionally, intertransversarii found in the cervical and lumbar regions can contract unilaterally to produce lateral flexion on the side of the contraction; however, both intertransversarii and multifidus act more importantly as stabilizers of the vertebral column during lateral flexion.

Thoracic spine

The lower half of the thoracic spine is more mobile in lateral flexion than the upper half and the total range of movement is between 20 and 25 degrees to each side. As in the cervical spine, lateral flexion is associated with rotation and for each degree of lateral flexion there is approximately one degree of vertebral rotation away from the side flexion motion, i.e. the spinous processes turn towards the concavity of the curve. During lateral flexion the ribcage modifies accordingly as the movement increases, becoming expanded on the elevated side and contracted on the opposite side.

In the thoracic spine the shapes of the vertebral bodies and their alignment to form a gentle posterior thoracic curve allow rotation to occur. The ranges of rotational motion are reduced and possibly lost when the curve is increased as in an exaggerated thoracic kyphosis or reversed as in thoracic spine extension.

The thoracic spine has an approximate range of 35 degrees to each side, the movement being comparatively free between the sixth and ninth thoracic vertebrae and comparatively limited towards the pectoral and pelvic girdles.

The muscles of the anterior abdominal wall largely produce thoracic spine rotation, in particular the oblique abdominal muscles. When the left internal obliques and the right external obliques contract together, the trunk rotates to the left.

Semispinalis, along with the muscles of the anterior abdominal wall, produces trunk rotation; when one side contracts, the trunk rotates to the opposite side.

Multifidus and the rotators can also produce rotation in the thoracic region but their most important role is one of stabilizing the vertebral segments through their lengthening and shortening as required to stabilize adjacent vertebrae.

Lumbar spine

The total range of lateral flexion in the adult spine is between 20 and 30 degrees to each side, possibly half of that available in the spine of a prepubescent child. However, as lateral flexion and rotation occur concurrently, and rotation is restricted by the shape and orientation of the lumbar facet joints, lateral flexion in the lumbar spine is limited throughout the total age range and even more so at the lumbosacral joint where rotation is normally minimal. However, rotation may become freer with increasing lumbar flexion, and this can be a feature of spinal dysfunction that leads to lumbar vertebral disc prolapse.

Both side flexion and rotation in the lumbar spine are prevented in lumbar extension due to the closely packed orientation of lumbar facet joints.

PELVIC GIRDLE

BONES AND JOINTS

The pelvic girdle, like the pectoral girdle, comprises three bones: the ilium, ischium and pubis that together form an innominate bone on each side. The left and right innominate bones then articulate anteriorly at the symphysis pubis and posteriorly with the sacrum at the left and right sacroiliac joints, so completing the bony pelvis.

The sacrum, comprising the five fused sacral vertebrae, is roughly triangular in shape with the base, formed by the first sacral vertebra, articulating with the fifth lumbar vertebra at the lumbosacral junction. The coccyx, comprising four fused coccygeal vertebrae, articulates with the fifth sacral vertebra, the apex of the triangular sacrum, at the sacrococcygeal joint.

The pelvis supports and protects the pelvic viscera, supports and transfers the body weight through the vertebral column to the lower limbs, and provides joint movement that assists correct lower limb function, as well as providing attachments for muscles. In the female, it also provides support for the birth canal.

The sacroiliac joints between the ilium and sacrum are united and stabilized by powerful ligaments in and around the joints. The orientation of the joints’ surfaces allows slight gliding and rotary movements during everyday activity.

In addition, the sacrum itself undergoes some 5 degrees of forward rotation independent of the ilium when the body moves from erect to supine. This sacral mobility is increased during pregnancy, and during childbirth there is a complex sacral movement that is analogous with nodding of the head.

The lumbosacral junction between the last lumbar vertebra and first sacral segment is part of the vertebral column and is potentially its weakest link. This is due to the incline of the superior sacral surface and the tendency for the fifth lumbar vertebra to slide on it and move downwards and forwards. However, this movement is prevented by the arrangement of the overlapping bony articular processes of the adjacent fifth lumbar and first sacral vertebrae, together with the strong ligamentous attachments that fix and stabilize the joint. Normal lumbosacral joint movements are flexion, extension and lateral flexion, and the degree of movement available varies from person to person and depends on age.

In children between the ages of 2 and 13 years the lumbosacral joint is very mobile and provides up to 75% of the total range of flexion and extension of the lumbar spine. However, this mobility reduces during puberty and adulthood so that by 35 years of age the average range of flexion and extension available is approximately 18 degrees and this reduces further as people age. Lumbosacral mobility in lateral flexion is considerably less than in flexion and extension, being approximately 7 degrees in children, 1 degree in mature adults and absent in the elderly.

The sacrococcygeal joint between the last sacral and first coccygeal segments allows passive flexion and extension during defecation and childbirth. This mobility is frequently lost by old age as degenerative changes fuse and eliminate the joint.

Only gold members can continue reading. Log In or Register to continue

Related

Stay updated, free articles. Join our Telegram channel

Tags: Teaching Pilates for Postural Faults Illness and Injury a pract

Sep 12, 2016 | Posted by admin in MANUAL THERAPIST | Comments Off

Full access? Get Clinical Tree

Get Clinical Tree app for offline access

Get Clinical Tree app for offline access