Anatomy of Back

Back Pain:

2^nd most common complaint after 50-80% experience low back pain, prevalence in USA is 15-20%. 45-64 yr olds. 14% of new visits are for back pain.

Osteoporosis:

46% vertebral, 16% hips, 16% wrist. 28 million Americans affected (10 mil osteoporosis, 18 million low bone mass) about 1/9 prevalence.

Regions:

Cervical region = 7 vertebrae. @ C7→ Vertebra prominens
Thoracic region = 12
Lumbar region = 5
Sacral region = 5 vertebrae fused in development into one.
Coccygeal region = 2-4 fused.
Opening @ base = sacral hiatus→ has fatty tissue and filum terminale (made up of the pia mater). Filum is tethered to the coccyx. No nerve roots there, only fatty tissue + filum.

Curves:

Primary curve at thoracic region and at sacral region (curve outward)
Secondary curves at cervical region and lumbar region (curve inward)
As fetus, only have primary curves→ secondary curves evolve due to weight bearing as fetus grows and grows to 4 yr old.

Abnormal Curvature:

Kyphosis = accentuation of primary curvature (esp. thoracic) = “dowager’s hump” (hunchback)

Lordosis = accentuation of secondary curvature in lumbar region.

Lateral curve (off to one side) = scoliosis.

Typical Vertebra:

Anterior aspect = vertebral body. Varies in shape region to region. Going posterior→ pedicles (foot processes). Each have processes: 1. extending laterally = transverse processes. 2. lamina that come together and extend posteriorly to form the spinous process.
Pedicle + lamina form the vertebral arch. When connected to body, Body + arch = vertebral foramen.
Articular processes: 1. superior 2. inferior. Each has a “facet” → smooth area which allows each vertebra to connect to the one above / below it. Contribute to joints between vertebra.
On upper and lower edges of pedicle = notches: 1. superior vertebral notch 2. inferior verbetral notch. These line up with the notches above / below to form another foramen = intervertebral foramen à path for exit of spinal nerves.

Different regions have different shapes:

Shape / size of body
Path of processes
Changes in foramen

Cervical:

Small body, squared off.
Transverse process: shorter. Each has a hole = transverse foramen→ has vertebral artery running through it→ blood supply to deep neck, brain, spinal column.
Spinous process: 2 prongs = a “bifid” process. Spinous process not angle downward very much, just slightly.
Distinguishing characteristic = transverse foramen
Facets face superior / inferior. Has most mobility, has rotation / flexion / extension / lateral flexion (touch ear to shoulder)

Thoracic:

Larger body, heart shaped.
Transverse process: longer, each has facet for rib tubercle (articulation of ribs and vertebra).
Spinous process: raked in downward direction
Distinguishing characteristics = facets on transverse process / body for rib articulation.
Facets face front to back, thus, movement has some rotation

Lumbar:

Even larger body, bean shaped.
Transverse process: longer, no major features.
Spinous process: large (robust) and extend staight out posteriorly.
Distinguishing characteristic = do not have either of the other characteristics in C or T.
Movement restricted to flexion / extension (bending forward, straightening up)

Smooth areas = Facets, where 2 bones articulate.

Rough areas = on processes→ where muscle will attach to bone.

C1 = Atlas. C2 = Axis

C1:

Has no spinous process and no vertebral body
Articulates with skull
Has posterior tubercle.
Large superior articular facetà where articulation with skull takes place.

C2:

Process extends superiorly from body = Dens AKA Odontoid process. It came from C1 in development (originally was C1 body).
Dens articulates with C1 and is held in place by ligaments

Pathologies:

Spina Bifida:

Incomplete vertebral closure, occurs in 1^st month, vertebrae malformed or missing.
Open spinal lesion forms→ damage to nerves or spinal cord is permanent. May lead to paralysis of lower limbs / bladder & bowl problems / learning problems.
Require surgical repair after birth.
Major types: occulta = mildest, malformation covered by skin. Up to 24% of population.
Meningocele = herniation of meninges (but spinal cord normal
Myelomeningocole = herniation of spinal cord, most severe.

Scoliosis:

Usually after 10, more in girls. Most common = adolescent idiopathic scoliosis.
Painful scoliosis from tumors = osteoid osteoma.

Vertebral Column Ligaments

Anterior longitudinal ligament runs all the way along the length of the spinal column. Runs along anterior aspect of body.
On posterior aspect of vertebral body = posterior longitudinal ligament (inside the canal) = smaller.
Anterior and posterior longitudinal ligaments are only flanking the vertebral body.
From the tip of each spine to the adjacent spine = supraspinous ligament = from C7 to Sacrum.
Nuchal ligament runs above C7 to base of skull. Very large and prominent ligament.
Interspinous ligament– between spinous processes
Intertransverse ligaments– between transverse processes
Ligamentum Flavum = yellowish tint. Connects lamina to lamina for adjacent vertebra. Must go through this to do lumbar puncture. Contacts vertebral canal.

Atlantooccipital Joint ligaments:

Between C1 and occipital bone = broad ligament “posterior atlantooccipital membrane”→ covers space between C1 and O bone.
Moving anterior→ posterior longitudinal ligament expands at C1 / C2 to become Tectorial membrane→ attaches Occipital bone.
Moving anterior→ See Cruciform ligament (cross shaped). Formed from superior longitudinal ligament (attaches O bone) + inferior longitudinal ligament (attaches C2)
Transverse cruciform ligament of Atlas holds Dens in place (other part of cruciform).
Attached to Apex of Dens = apical ligament of Dens→attaches to Occipital bone.
Alar ligaments = pair of ligaments extending from Dens to Occipital bone. Limit the rotational movement of head.

Intervertebral Discs

Numbering: uses #’s of vertebra on either side, such as L3-4.
No disc between C1 and C2, only have solid bone Dens.
Disc: outer anulus = form fibrocartilage rings on outer portion, has vasculature. Thinner posteriorly.
Inner squishy nuclear part = nucleus pulposis. Is mucoid, 70-90% water, has reticular and collagen fibers, no vasculature.
The discs account for 25% of length of vertebral column. With increasing age, water content of disc decreases, leading to loss of height and loss of turgor (not as cushionyà potential rupture).
Spinal cord ends at L1-2 @ Conus Medullaris.
8 C spinal nerves for 7 vertebrae.
Discs will herniated in posterior / lateral direction. The posterior longitudinal ligament usually prevents rupture of disk in posterior direction, thus disc will rupture out to the side of it→ impinges nerves. Rupture of discs in thoracic region is very rare. Most common = lumbar region. The nerve root below the # Disc is affected. If L4-5 disc protrudes→ affects the L5 nerve root.
Obtunded: dull or blunted patient, can’t tell if they are in pain due to intoxication.

Vasculature:

Segmental medullary arteries supply spinal cord, radicular arteries do not.
Anastomosis = end to end connection between blood vessels (between the two vein plexuses)
At each region of spine, have blood supply sources.
Lumbar region: Lumbar arteries
Thoracic region: Intercostals arteries = between ribs
Cervical region: Vertebral arteries (branch of subclavian) and ascending cervical arteries (from costocervical trunk) and deep cervical arteries (from thyrocervical trunk).

Thoracic region: As intercostal artery passes, it sends a segmental spinal artery branch which goes into vertebral canal: branches into either

Radicular artery→ for dorsal root ganglia and dorsal / ventral roots from posterior / anterior branches. Goes right up to spinal cord but stops short.
Segmental medullary artery→ branches and supplies nerve roots and also onto spinal cord itself. Anterior / Posterior branches→ join with anterior spinal artery (one) and posterior spinal arteries (two), all 3 of which run along longitudinal length of spinal cord. Only a small portion of intercostals artery branches will become segmental medullary artieries by branching into the spinal cord arteries.

Great segmental medullary artery of Ademkiewicz:

Usually on left side
Arises in lower portion of thoracic region (T9-11)
Supplies the lower 2/3 of the spinal cord itself. Very important. Accidental ligation leads to post operation ischemia and paraplegia.

Venus plexus: 2

Internal venus plexus = inside the Vert. Column (has posterior / anterior sides)
External venus plexus = outside the Vert. Column (has posterior / anterior sides)

Joined by anastomoses→ union between inside and outside.

Muscles:

Extrinsic muscles: work on upper limb or respiration, do not move back itself. Innervated by branches of the ventral / anterior primary rami = named nerves (e.g. radial, ulnar). Connect upper limb to trunk and assist respiraton.

Superficial layer = (4) Trapezius, latissimus Dorsi, Rhomboid muscles (major / minor), levator scapulae
Deep layer = (2) serratus posterior muscles (superior / inferior)

Intrinsic muscles: move back or give postural support. Innervated by branches of the dorsal primary rami.

Superificial layer = (2) splenius muscles (capitis / cervicis)
Intermediate layer = (3) Erector Spinae (iliocostalis, longissimus, spinalis). All with common origin.
Deep layer = (3) Transversospinal (Spinalis thoracis, spinalis cervicis, semispinalis capitis)

Scapula:

Medial border = Vertebral border, runs next to vertebral column.
Lateral Border
Superior angle
Inferior angle
Along posterior aspect of scapula = ridge→ “spine” of the scapula. Extends laterally and becomes known as acromion (highest point of scapula).
Extending anteriorly = coracoid process “coracoid”.
On lateral side toward top = Glenoid Cavity, shallow, is point of attachment for shoulder joint.

Skull:

At midline, have external occipital protuberance. Small palpable bump.
Laterally on either side→superior nuchal lines = ridges on either side of external occipital protuberance.
Illiac crests = on hip bones, for attachment
Trapezius = has long origin. Starts at external occipital protuberance and superior nuchal line. Attaches to spinous processes all the way down to T12. Fibers extend out to spine of scapula and onto front of body to bind clavicle. Main function is to move upper limb.
Latissimus dorsi = attaches to iliac crest down onto the sacrum and also the spinous processes. Involved in moving the upper limb.
Rhomboids: Major and minor. Attached to spinous processes and extend inferiorly / laterally to vertebral border of scapula. Will move scapula toward spine.

- Major: origin T2-5 spines, insert posterior medial border of scapula
- Minor: origin ligamentum nuchae, C7,T1 inserts below levator scapulae on posterior medial border of scapula.

Levator Scapulae: Elevates scapula (shrugs). Origin: transverse processes of C Vertebrae, inserts at medial border of scapula.
Serratus posterior inferior: Origin = Spinous processes and supraspinous ligs of T11-L2. insertion = Post aspect of ribs 9-12. forced expiration.
Serratus posterior superior: Origin = Spinous processes and supraspinous ligs of C7-T2.
Insertion = Post aspect of ribs 2-5. forced inspiraton.

Intrinsic muscles of the back:

Splenius capitis: origin = Lower lig nuchae, spinous processes and supraspinous ligs T1-3.
Insertion = Lat occiput between sup and inf nuchal lines. Extend / rotate C spine.
Splenius Cervicis: beneath capitis. Origin = Spinous processes and supraspinous ligs of T3-6. Insertion = Post tubercles of transverse processes of C1-3. extend / rotate C spine.
Intermediate group: Erector spinae muscles. Will either laterally flex (one side) or extend (keep upright against gravity). Take origin from “common origin” in lumbar / sacrum region. Attaches to sacrum and iliac crest. Are all blended together at this point.

- illiocostalis = attaches ribs or transverse processes. 3 parts = lumborum, thoracis (both attach ribs) and cervicis (attaches transverse processes of vertebrae)
- longissimus: 3 parts= thoracis, cervicis, capitis. Origins for all = TVP, insertions: Thoracis = TVP / ribs, cervicis = TVP / AP, Capitis = Cranium.
- Spinalis: originates and attaches to spinous processes. Spinalis thoracis: O = SP, I = SP. Spinalis cervicis: O = nuchal lig. I = TVP / AP. Capitis: O = AP/TVP I = cranium.

Deep group: transversospinal muscles. Transverse processes to spinous processes.
semispinalis capitis muscle = large. Associated with greater occipital nerve, nearly as large as pencil.

Innervation:

Spinal nerve branches off into dorsal and ventral Rami.
Intrinsic muscles = innervated by Dorsal Rami.
Extrinsic muscles = innervated by ventral Rami. Dorsal pass through them, but do not innervate. Dorsal innervate skin of back as well. Ventral Rami innervate everything else as well (limbs etc).