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Anatomical Snuffbox Anatomy and Significance

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The anatomical snuffbox is a triangular deepening on the dorsoradial aspect of the hand at the level of the carpal bones.

It is visible with ulnar deviation of the wrist and extension and abduction of the thumb.

The name snuffbox is derived because this depression was used as a means of placement for the inhalation of powdered tobacco.

The anatomical snuffbox is an anatomical landmark, to be specific a surface anatomy feature.

By knowing the extent and content of the box, a better differential diagnosis could be created when there is pain in this area.

For example, tenderness in the anatomical snuffbox after a FOOSH injury may indicate a scaphoid fracture.

The anatomical snuffbox is also known as radial fossa.

Structure of Anatomical Snuffbox

Anatomically, the tendon of extensor pollicis longus forms the posterior border.

The anterior border is formed by extensor pollicis brevis and the abductor pollicis longus.

Just to make perspective clear, the thumb is on the lateral side and little finger is on the medial side.

The styloid process of the radius forms the proximal border and the apex of the triangle formed by the anterior and posterior border forms the distal border.

Tendons of anatomical snuffbox
Image Credit: Teach Me Anatomy

The floor of the anatomical snuffbox is formed by the scaphoid bone and trapezium bone of the wrist, as well as the tendons of the muscle named the extensor carpi radialis longus and the muscle named the extensor carpi radialis brevis.

The radius and scaphoid articulate deep to the snuffbox to form the basis of the wrist joint.

The base of the first metacarpal bone can be palpated distally, and the styloid process of the radius can be palpated proximally.

Following structures are present within the anatomical snuffbox

  • Radial artery
  • Superficial branches of the radial nerve,
  • Cephalic vein.

Anatomical Variants

The variations noted are in the following structures

  • Multiple tendon slips of both the extensor pollicis longus and the abductor pollicis longus have been shown to have not only numerous tendon slips
  • Altered insertion points for both of the above tendons
  • Variations in the location of the cephalic vein and radial artery.
    • Could lead to inadvertent puncture

Clinical Significance

Scaphoid Fracture

The Scaphoid fractures are common after a patient falls onto an outstretched hand  [especially when it is pronated and in ulnar deviation].

Tenderness in snuffbox is considered as a hallmark of the scaphoid fractures.

In fact, all patients with snuff box tenderness should be subjected to x-rays to confirm or rule out the scaphoid fractures as the sign is suggestive but is not specific.

De Quervain tenosynovitis

This is tenosynovitis that affects the first dorsal extensor compartment which houses the abductor pollicis longus and extensor pollicis brevis. These muscles form the lateral border of the snuffbox.

The presentation and clinical examination of de Quervain disease are quite typical and the diagnosis is often made clinically.

Idiopathic Radial artery aneurysm in the Snuffbox

Radial artery aneurysms are extremely rare but may develop following radial trauma.

References

  • Thwin SS, Fazlin F, Than M. Multiple variations of the tendons of the anatomical snuffbox. Singapore Med J. 2014 Jan;55(1):37-40.
  • Robson AJ, See MS, Ellis H. Applied anatomy of the superficial branch of the radial nerve. Clin Anat. 2008 Jan;21(1):38-45.

Bone Spur or Osteophyte- Causes and Treatment

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A bone spur is a bony growth formed on a normal bone. In medical language, it is termed as an osteophyte. A bone spur is an extra bone and can cause symptoms due to pressure on adjacent tissues.

Bone spurs are also called osteochondral nodules, osteochondrophytes, and chondro-osteophytes.

Osteophyte is part of degenerative changes that occur with age.

How does Bone Spur Form?

An osteophyte is a fibrocartilage-capped bony outgrowth originating from precursor cells in the periosteum. The periosteum is a layer that lines the bone.

A bone spur is a response by the body to some sort of external stimulus. This repair response may lead to the formation of extra bone called spur.

The stimulus can be due to

  • Pressure from adjacent tissue
  • Rubbing or friction
  • Pull
  • Prolonged stress.
  • Aging process

An osteophyte develops when the remaining cartilage in a damaged joint attempts a repair after there is cartilage loss elsewhere in the joint.

It tends to form in the joint compartment where there has been cartilage loss.

This is an attempt by the body to stabilize the joint.

However, their formation pathway and factors involved are not completely understood.

It must be noted that osteophytes can also develop in the absence of explicit cartilage damage.

Traction on a surface could also lead to spur formation.

Sites of Bone Spur

  • Knees
  • Hips
  • Spine
  • Shoulder
  • Hand
  • Foot
  • Heel
  • Elbow [at extensor surface of elbow]

Spine, hip and knee are common where osteophytes are seen.

Osteophytes can be at the margin of the joint where they are called marginal osteophytes. These can develop at the periphery or margin of any joint.

The other types are called central osteophytes because of their deep location in joint.  These are mostly seen in the hip and knee.]

What are the Risk Factors for Osteophyte Formation

  • Increasing age
  • Joint injury
  • Poor posture
  • Genetics
  • Congenital skeletal abnormalities

Osteophytes are often signs of joint degeneration.

They are seen in different types of arthritis both inflammatory and degenerative. 

Clinical Presentation

The osteophyte itself is not painful. However, depending on the location and size, it may cause it may affect other structures, resulting in pain. In addition, the presence of osteophytes may merely indicate an underlying condition which leads to the symptoms.

For example, osteophytes in the spine are present in almost all the people but they do not specifically cause of back pain but other associated changes are.

Similarly, a bone spur in the heel does not cause pain in plantar fasciitis but the symptoms are often attributed to it, though wrongly when osteophyte is present.

In another example, while osteophytes is a telltale sign of knee osteoarthritis, the pain in the knee is usually due to other changes which are associated with the degenerative condition. But in some cases, osteophytes of the knee might cause pain as well.

Osteophytes may impinge on or stretch the adjacent structures and cause pain too.

For example, nerve impingement at the neuroforamen could cause radicular pain, numbness, burning, and paresthesiae [pins and needles] in the limb supplied by the affected spinal nerve.

If the motor root is affected, there could be muscle spasm or weakness of that part.

Thus all bone spurs are not symptomatic. Many people carry spurs along without ever knowing them.  The spur would cause symptom only when it presses on adjacent tissues.

It also must be highlighted that spurs are mostly found on radio imaging. They are not a diagnosis but mostly a radiological sign which is part of a bigger process.

A bone spur is usually visible on an X-ray. Most of them are however investigated only when they cause symptoms or they might be an incidental finding on an x-ray done for some other reason.

Treatment of Bone Spur

Again the treatment is aimed at the condition which has caused the spur and not the osteophyte itself.

The treatment should be restricted only to those which are symptomatic.

As most of the bone spurs or osteophytes are asymptomatic, most of them do not require the treatment.

Ideal treatment should address the cause that led to bone spurs, treat the symptoms caused by bone spurs and if needed [rarely] removal of bone spurs.

In some rare cases, the spur [for example olecranon spur] itself is a problem. In such cases, the treatment is directed at the spur only.

Following measures are generally applied in the treatment of bone spurs or osteophytes. The treatment needs to be individualized and all the measures may not be applicable in one patient.

  • Weight loss (especially when osteoarthritis or plantar fasciitis is the cause)
  • Stretching exercises of the affected area
  • Ultrasound or deep tissue massage
  • Rest and Ice compression
  • Nonsteroidal anti-inflammatory drugs
  • Orthotic braces/padding/footwear modification
  • Corticosteroid injection
  • Surgical removal

Pars interarticularis Anatomy and Significance

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What is Pars Interarticularis?

The Pars Interarticularis is a special region of the lamina between the superior and inferior articular processes. The term literally means part between the articulations in Latin language and is kind of bony bridge that joins these two upper and lower facets.

pars interarticularisThus one vertebral has two pars interarticularis.

Thus facet joints above are connected to the joints below in one vertebra through the pars interarticularis.

An isthmus is a narrow portion of land that joins two larger bodies of land. Pars interarticularis is considered isthmus between two facet joints.

Significance of Pars Interarticularis

Pars interarticularis may develop a stress fracture in young athletes. Defect in the pars could lead to spondylolisthesis

When we can see on x-ray in the lateral view, vertebra, L4. L5 and S1  face downward and forward as they form the lower end of the normal lordotic curve.

spondylolysis and spondylolisthesis
Spondylolysis and spondylolisthesis. Image credit: Open i

These two vertebrae bear the entire weight of the spine above.

The inferior facets prevent the sliding of lower vertebra forward by acting as a buttress. Thus L5 inferior facets act as a buttress to S1 slide and L4 inferior facets to L5 slide.

An analogy could be given that of door stops. Pars interarticularis joins these “door stops” to the upper structures of the vertebra(the pedicles).

This puts these structures under quite a significant load, especially under the impact.

Sports, jumping, and activities involving hyperextension of the spine [as in gymnasts] can cause overloading.

This could lead to stress fractures of pars interarticularis.

While stress fracture can heal with rest, the continued activity could lead to complete fracture and then nonunion which then becomes a cause for a forward slip of vertebra [no more doorstop effect]. The disc is not able to resist this as dis has poor shear strength.

The disc, under stress, stretches and tears paving a way for the unresisted forward slip.

The fractures normally occur on pars of both sides but occasionally can only on one side. A unilateral pars fracture causes the other, intact pars to bear all the stress and this eventually leads to fracture of that pars too.

Before the conclusion, I would like to mention a similar sounding term – spondylolysis. It means there is a break or fracture of the pars but no slip.

When the slip occurs, the term used is spondylolisthesis.

Pars fracture or spondylolisthesis could be discovered as an incidental finding when a child is evaluated for some other reason or could present as back pain that is aggravated by continued lumbar loading.

The diagnosis has to be radiologically confirmed though clinically it could be suspected in some cases.

Scottie Dog Sign and Collar Sign

Scotty dog sign on oblique view spine, shows intact pars interarticularis
Case courtesy of A.Prof Frank Gaillard, Radiopaedia.org. From the case rID: 7552

This sign suggests the normal appearance of the lumbar spine seen on oblique view x-ray. Following elements contribute to formation of Scottie dog with:

  • Transverse process forms the nose
  • Pedicle forms the eye
  • Inferior articular facet forms the front leg
  • Superior articular facet forms the ear
  • Pars interarticularis forms the neck of the dog.

In the presence of spondylolysis, the pars interarticularis, or the neck of the dog, shows a break or defect.

It looks like a collar around the neck and is called collar sign.

Some also call this a beheaded Scottish Terrier sign as the defect may be imagined for decapitation.

Foods for Healthy Bones- Sources and Requirement

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Doctor! What are foods for healthy bones? What should I eat so that I get strong bones and joints?

I received this question in my mail recently. Actually, it is an often asked question. Not only this, some people are interested in superfoods for healthy bones.

Well! Before we discuss the foods for healthy bones that make your bones strong, I wish to clarify about superfoods.

There are no superfoods for bone or other health aspects.

It is more of a marketing term to grab your attention.

See, the purpose and function of the food we eat is to provide nutrients. The body utilizes these nutrients to build and repair our body and thwart diseases.

There are five major groups of food

  • Proteins
  • Carbohydrates
  • Fats
  • Vitamins
  • Minerals

When each of nutrient group is present in our diet in an optimum and recommended amount, the diet is considered a balanced diet.

As a child grows, skeleton accumulates bone mass. The bones remain strong in adulthood and after that, the bone mass starts declining.

Therefore, the requirement of different nutrients varies with age. It could also vary with the type of physical exertion and targets. For example, bodybuilders require more proteins to build strong muscles.

foods for healthy bones

What are the Nutrients Needed for Bone Building and Metabolism?

Read about bone anatomy and physiology

Bones consist of two things- protein matrix and minerals. Calcium forms the main mineral content of the bone. Vitamin D3 plays a role in calcium metabolism. Most of the vitamin D is available naturally and is available to us by virtue of sunlight. Therefore, a healthy dose of sunshine should provide an adequate amount of vitamin D3. A body rich in vitamin D3 would utilize calcium better and thus have stronger bones.

When we advise foods for making your bone healthier, these foods are the ones which are rich in calcium. Here are the foods which are rich in calcium and are good for bone health. Calcium is the cornerstone of strong bones. 

Exercise also has got to play a role in building healthy bones. It has been found that bone mass is more in persons who exercise than who do not.

For supplying enough nutrients, a  healthy diet is essential to build strong bones as the child grows and in adulthood, it maintains the strength.

As we noted before, bone is composed of proteins and various minerals of which calcium is the major mass contributor. Other important minerals are magnesium, silicon,  boron,  copper, and manganese.

Vitamin D is the main vitamin required for extracting calcium from the diet [increases absorption of calcium in the gut] and sending calcium to bone from blood. Therefore, in deficiency of vitamin D, no amount of calcium-rich foods or supplements are going to help.

Vitamin C and K are also involved in bone metabolism.

Adult Dietary Requirements of Foods for Healthy Bones

  • Vitamin D – 600-800 IU
  • Calcium – 1000-1200 mg
  • Phosphorous – 700-4000 mg/day
  • Magnesium- 320-420 mg
  • Copper-0.9 mg
  • Zinc 8-11 mg
  • Manganese 1.8-2.3 mg
  • Vitamin K – 90-120 µgm
  • Vitamin C-75-90 mg

Recommended dietary allowance has not been established for silicon and boron. However, it is thought that silicon 40 mg and boron – 3 mg daily should be good enough for maintaining good bone health.

The requirement is generally more for children and teenagers.

With this background now we would come to different foods that would provide one or more nutrient of bone building.

Food Sources for Various Bone Nutrients

Vitamin D Foods

Vitamin D is normally synthesized in the skin on exposure to sunlight. Therefore, normally it is not required in the diet. But recently, an increased prevalence of vitamin D insufficiency has been reported in children as well as adults. This probably due to reduced exposure to sunlight.

Therefore, one should maintain proper sun exposure which could vary from 10-60 minutes a day several times a week.

The length of exposure would change with a skin complexion as darker people need more exposure than lighter.

Foods that supply vitamin D are

  • Fatty fish, like tuna, mackerel, and salmon
  • Beef liver
  • Cheese
  • Egg yolks

Apart from this, fortified foods like

Foods fortified with vitamin D, dairy products, orange juice, soy milk, and cereals etc.

Vitamin D supplements are also available.

Calcium Rich Foods

Milk

The biggest and most easily available calcium source is milk. A single 8-ounce cup of milk has 300 milligrams of calcium.

Yogurt and Cheese

A cup of yogurt has at least as much calcium as an 8-ounce cup of milk. And 1 ounce of Swiss cheese has nearly as much. These options are good for people who have milk intolerance or cannot drink milk for some other reason.

Sardines

Eating 3 ounces of canned sardines delivers a little more calcium than a cup of milk.

Vegetables

Calcium is plentiful in many vegetables. Dark leafy greens such as Chinese cabbage, collard, and turnip greens, offer a lot of calcium.

Soy Food

Half a cup of calcium-enriched tofu contains as much as 861 milligrams of calcium. Isoflavones which have been found to enhance bone density are also found in good quantities soy foods, such as tofu.

Salmon

They contain calcium as well as vitamin D, which assists in calcium absorption. They are also high in omega-3 fatty acids.

Nuts

Walnuts and flaxseeds are packed with omega-3 fatty acids. Peanuts and almonds contain potassium, which protects against the loss of calcium in the urine. Nuts also contain protein and other nutrients that play a supportive role in building strong bones.

Fortified Foods

Fortified foods are products that do not naturally contain calcium but have been enhanced with varying amounts of the essential mineral. Fortified juices and cereals are available and can be a good source of calcium. Check the nutritional label for the exact amount.

Calcium Supplements

Supplements are an easy way to boost your calcium intake, but some reports suggest you may not need them if you’re already getting enough calcium from food.

Dietary Sources of Phosphorous

Calcium combines with phosphates to deposit in the bone. Phosphorous is available in the diet in a number of the foods. Phosphorous deficiency is rare unless there is a metabolic issue.

Recommended allowance is 700mg/day and the maximum allowed limit is 4000 mg/day. Following are few phosphorous-rich foods

  • Poultry – chicken, turkey
  • Seeds
  • Seafood
  • Whole grains
  • Nuts
  • Meat

Magnesium Rich Foods

Magnesium is required in small quantity but is an essential mineral of bone. Following foods are rich sources of magnesium.

  • Almonds
  • Cashews
  • Peanuts
  • Raisins
  • Bran cereal
  • Kidney beans
  • Lentils
  • Potato skins
  • Brown rice,
  • Milk

Foods Sources of Silicon

It has been found that dietary more than 40 mg/day of silicon correlates with increased bone mineral density

Silicon is found in whole grains, green beans, cereals like barley and carrots. Some brands of mineral water may have orthosilicic acid. 

Beer is made from cereals and is a good source of silicon. It is thought that this deficiency is less in males due to beer drinking.

Foods that Provide Boron

Though exact mechanism is not clear, boron stabilizes and extends the half-life of vitamin D and estrogen. About 3 mg of boron per day is known to increase bone strength.

Prunes, raisins, dried apricots, or avocados are important sources.

Zinc Foods

Recommended daily allowance of zinc is 11 mg/day in men and for women is 8 mg/day. Often zinc is found in sufficient quantity in a routine diet but vegetarians may have a deficient diet. Main sources of zinc are 

  • Red meat
  • Poultry
  • Shellfish
  • Seeds and Nuts
  • Beans. 

Manganese Foods

Manganese is also found in sufficient quantities in food.

Recommended Daily Allowance is 1.8 mg/day for women and 2.3 mg/day for men.

Dietary sources of manganese are

  • Pineapples
  • Mollusks (Clams, Mussels)
  • Beans
  • Dark Chocolate
  • Cinnamon
  • Teat
  • Nuts
  • Cereals, nuts, pineapples, beans, mollusks (clams, oysters, mussels), dark chocolate, cinnamon, and tea.

Copper Dietary Source

Copper is recommended in a quantity of 0.9 mg/day. Copper too is widely available in foods including meats, nuts, grains, seafood, and cocoa. 

Vitamin K and Vit C Sources

Vitamin K is recommended in quantity 90 micrograms (women) and 120 micrograms (men).

Vitamin K is required for carboxylation of osteocalcin, a bone protein and its deficiency leads to osteopenia and increased fracture risk.

Mai dietary sources are

  • Collard greens
  • Spinach (fresh)
  • Kale,
  • Brussels sprouts
  • Iceberg lettuce
  • Prunes 

Vitamin C

Since its discovery as the nutrient whose deficiency led to scurvy, vitamin C has revealed many roles it plays in the body and now is one of the foods for healthy bones.

Vitamin C has been found essential for the formation of collagen and for fracture healing.

Also increased bone mineral density has been noted in postmenopausal women taking vitamin C supplements.

Vitamin C is recommended in the dosage of 75-90 mg per day. Citric fruits (orange, kiwi, lemon, guava, grapefruit), are the most important sources. Other sources are broccoli, cauliflower, Brussel sprouts, and capsicums.

Should Supplements Be used?

Use of supplements is based upon eating habits of the population. American data shows that there is a need for supplementation of Vit D, calcium, magnesium, silicon, vitamin K, and boron.

Supplements of the nutrients which are present adequately in the diet are not required. For example, phosphorous, copper and manganese and zinc.

However, the choice can be made on an individual basis.

References

  • Heany R. The vitamin D requirement in health and disease. J Steroid Biochem Mol Biol. 2005;97:13–9.
  • Vormann J. Magnesium nutrition and metabolism. Mol Aspects Med. 2003;24(1-3 ):27–37. 
  • Jugdaohsingh R. Silicon and bone health. J Nutr Health Aging. 2007;11:99–110. 
  • Bügel S. Vitamin K and bone health in adult humans. In: Litwack G, editor. Vitamins and Hormones: Vitamin K. London: Elsevier; 2008. pp. 393–416.
  • Newnham R. Essentiality of boron for healthy bones and joints. Environ Health Perspect. 1994;102S(S7 ):83–95S. 
  • Hall S, Greendale GA. The relation of dietary vitamin C intake to bone mineral density results from the PEPI study. Calcif Tissue Int. 1998;63(3 ):183–9. 
  • Maret W, Sandstead HH. Zinc requirements and the risks and benefits of zinc supplementation. J Trace Elem Med Biol. 2006;20:3–18. 

 

Axis or Second Cervical Vertebra [C2]

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Axis is the second vertebra of the spine and is also called C2 bone vertebra. It articulates with C1 or atlas vertebra above and C3 vertebra below.

The axis is an atypical cervical vertebra like atlas and vertebra prominens or C7 vertebra.

It forms a pivot for atlas to rotate providing greater range of motion that would have possible otherwise. The majority of the movement occurs around the dens and at the atlanto-axial joint.

Structure of Axis Vertebra

The components forming the axis can be divided into anterior and posterior

axis

 

Anterior components of the axis are composed of dens [a conical shape upright protrusion], body [attached superiorly to dens], the transverse process [with foramina transversarium], superior and inferior articular facets, pedicle, lamina [pedicle and lamina form posterior arch], and spinous process.

Dens is also known as odontoid process. It is a strong, tooth-like process projecting upwards from the body of axis.

Dens is unique to the axis and represent the body of the first cervical vertebra that fused with the body of the axis.

The dens articulates anteriorly with the anterior arch of the atlas, and posteriorly with the transverse ligament of the atlas. The ligament also holds the dens to the anterior arch.

Body of the axis – The superior surface is of the body is fused with the dens.

On each side, there is a large superior articular facet encroaching on the body.

The inferior surface has a prominent anterior margin which projects downwards. Anterior surface presents a median ridge on each side of which there are hollowed out impressions.

Vertebral arch is formed by pedicles and laminae.

C2 vertebra or axis from the side

Atlas and Axis Vertebrae
Image Credit: http://www.chiropractic-help.com/Atlanto-axial-joint-anatomy.html

Pedicles are thick and strong and anteriorly coalesce with body and margins of dens. They are superiorly covered by superior articular facets.

Inferior vertebral notch, placed in front of the inferior articular process, is deep but superior vertebral notch [placed on the upper border of the lamina, behind the superior articular process] is shallow.

Laminae are thick and strong.

Articular facets – Superior articular facet occupies the upper surfaces of the body and of the massive pedicle. It is a large, flat, circular facet which is directed upwards and laterally and has a lateral overhang till foramen transversarium. Superior articular facets form atlanto-axial joint with corresponding inferior facets from atlas.

Inferior articular facet lies posterior to the transverse process and is directed downwards and forwards to articulate with the 3rd cervical vertebra.

The transverse processes are very small and represent the true posterior tubercles only. The foramen transversarium is directed upwards and laterally.

The spinous process is large, thick and very strong. It has an inferior grove and tip is bifid.

Attachments

Dens

  • Apex- the apical ligament
  • On each side – alar ligaments.

Body

  • Anterior surface
    • longus colli insertion
    • Anterior longitudinal ligament
  • Posterior surface from below upwards
    • Posterior longitudinal ligament
    • Membrana tectoria
    • Vertical limb of the cruciate ligament.

Laminae

  • Ligamenta flava or yellow ligament.

Transverse process

  • Levator scapulae [tip]
  • Scalenus medius [anteriorly]
  • Splenius cervicis [posteriorly]
  • Intertransverse muscles- Upper and lower surfaces

Spinous process

  • Ligamentum nuchae
  • Semispinalis cervicis
  • Rectus capitis posterior major
  • Inferior oblique
  • Spinalis cervicis
  • Interspinalis
  • Multifidus.

Articulations

  • Atlanto axial joint with atlas  – superior articular facet with inferior articular facet of C1
  • Dens articulates with the posterior aspect of the anterior arch of C1
  • Joint between C2-C3 – inferior articular facet with superior articular facet of C3
  • intervertebral joint – Between C2/3 bodies with an intermediate disc intervertebral disc

Relations of Axis vertebra

Anteriorly

  • Anterior atlanto-axial membrane
  • Anterior longitudinal ligament

Posteriorly

  • Posterior atlanto-axial membrane
  • Ligamentum nuchae
  • Posterior to dens – apical ligament, cruciate ligament alar ligament

Laterally

  • Vertebral arteries and veins [traverse foramina transversarium and move laterally]

Supero-posteriorly

Sub-occipital triangle

Medially

  • Spinal cord within vertebral foramen
  • Basivertebral veins

Development of axis vertebra

Five primary and two secondary ossifications centers

  • Primary ossification centers
    • Vertebral arch – 2 centers, appear at the 7th or 8th week of life
    • Vertebral body – 1, appears at the 4th or 5th month of life
    • Dens -2 centers appear appears at the 6th month of life, fuse before birth forming a conical mass
  • Secondary ossification centers
    • Apex usually  appear from 5- 8 years of age and fuse at around the 12th year
    • Ossification and fusion of cartilaginous disc that initially separates the dens from the vertebral body.

 Clinical Significance

Hypoplasia and aplasia of odontoid process is rare but can occur. Os odontoideum was thought to be a congenital deformity earlier but presently it signifies old chldhood trauma that separates dens from body of axis.

Atlas or First Cervical Vertebra [C1]

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Atlas is the first cervical vertebra that sits just below the skull. It is also called C1 vertebra. Along with axis, the second vertebra and C7, it falls into the group of atypical cervical vertebrae.

Atypical because these have unique features.

Axis and C7 or vertebra prominens are discussed separately.

Atlas is unique in its shape. It articulates with the dens of the axis, a process of axis vertebra that projects superiorly and the occiput.

Articulation with axis allows rotation of the head whereas articulation with occiput assists in flexion, extension and lateral flexion of the head.

It is called the atlas after the mythological hero that bore the weight of celestial heavens on its shoulders.

Atlas can be identified by its ring shape. There is no vertebral body or spinous process.

Structure of Atlas

The atlas is composed of

  • Anterior arch marked by a median anterior tubercle on its anterior aspect. Its posterior surface bears an oval facet to articulate with the dens.
  • Posterior arch – Forms three-fifths of the ring. Posterior surface marked by median posterior tubercle.
  • Paired lateral masses
  • Paired transverse processes

It has no body. The dens of the axis sits where a body of a typical vertebra is.

The transverse atlantal ligament [it holds dens against anterior arch] divides its vertebral canal into anterior 1/3 and posterior 2/3 . Anterior portion is occupied by dens.

Spinal cord is present in the posterior portion.

Atlas

Anterior arch

It has the following important parts.

Anterior tubercle is present on the anterior aspect of the anterior arch.  It is the site of attachment of the anterior longitudinal ligament

Posterior facet for the dens is prsent on the posterior aspect of the anterior arch

Upper border and lower borders provides attachment to

  • Anterior atlanto-occipital membrane
  • Lateral parts of the anterior longitudinal ligament

Posterior arch

It forms 3/5th of the circumference of the ring.

Posteriorly, it bears posterior tubercle which is a rudimentary spinous process. it provides an attachment to the ligamentum nuchae.

Posterior to lateral mass, the superior surface of the posterior arch has grooves for C1 nerve and vertebral artery.

Superior border provides attachment to the posterior atlanto-occipital membrane and inferior border provides atachment to ligamentum flava or yellow ligament.

Lateral Mass

These are paired ovoid structures whose upper surface bears elongated concave articular facet directed upwards and medially. This articular facet articulates with the corresponding condyle to form an atlanto-occipital joint.

On the lower surface, there is an articular facet which is almost circular, flat and is directed downwards, medially and backwards.

It forms the atlantoaxial joint with axis vertebra.

The medial surface bears a small roughened tubercle for attaching transeverse ligament ad is also marked by a vascular foramen.

Transverse Process

It projects laterally from the lateral mass and is very long. In fact, it is longer than all of the transverse processes of the cervical vertebrae except C7. [ You can palpate by insinuating finger between the angle of mandible and mastoid process.]

It, by virtue of its length, acts as an effective lever for head rotation.

The transverse process is pierced by the foramen transversarium which harbors vertebral arteries.

Sometimes. a tubercle is present on the anterior aspect of the transverse process

Joints of Atlas

Atlas and Axis Vertebrae
Image Credit: http://www.chiropractic-help.com/Atlanto-axial-joint-anatomy.html

Atlanto-occipital joint

This is a synovial joint between the occipital condyle and superior facet of the lateral mass of the atlas.

The joint is covered by a capsule and allows for flexion, extension and lateral flexion.

It is innervated by C1 fibers.

Atlanto-axial Joint

Atlanto-axial joint is actually composed of two types of joints. One is medial atlantoaxial joint between dens and posterior aspect of anterior arch of the atlas. Another type is lateral atlantoaxial joint, present on either side, between inferior articular facet of the atlas and superior articular facet of the axis.

Median atlanto-axial joint

  • Synovial joint between the dens of the axis and the posterior aspect of the anterior arch of the atlas
  • Allowsthe rotation of the head.
  • The dens is held in place by the transverse ligament. there is a  bursa between the two.

Lateral atlanto-axial joint

  • Synovial joint between the inferior articular facet of the atlas and the superior articular facet of the axis
  • Allows the rotation of the head
  • Innervated by the C2 nerve

Attachments

  • The anterior tubercle
    • Anterior longitudinal ligament in the median plane
    • Upper oblique part of the longus colli muscle
  • Anterior arch
    • Upper border – Anterior atlanto-occipital membrane.
    • Lower border
      • Lateral fibers of the anterior longitudinal ligament.
      • Atlantoaxial ligament [ Provides tertiary support against ventral translation of the dens.]
  • The posterior tubercle
    • Ligamentum nuchae in the median plane
    • Origin to the rectus capitis posterior minor on each side
  • Posterior  arch
    • Groove on the superior surface occupied by the vertebral artery and C1 nerve.
    • Behind the groove attachment to the posterior atlanto-occipital membrane.
    • Lower border – Attachment to ligamenta flava.
  • Lateral mass
    • Tubercle on medial side gives attachment to the transverse ligament of the atlas.
    • The anterior surface – origin to the rectus capitis anterior
  • Transverse process
    • Origin to the rectus capitis lateralis (upper surface anteriorly)
    • Superior oblique (upper surface posteriorly)
    • Inferior oblique (lower surface of the tip)
    • Levator scapulae (lateral margin and lower border)
    • Splenius cervicis
    • Scalenus medius.

Thus following muscles are attached on the atlas

  • Longus colli
  • Splenius cervicis
  • Superior oblique
  • Inferior oblique
  • Rectus capitis posterior minor
  • Arcuate foramen is a normal variant of the atlas and develops by calcification of the posterior atlanto-occipital membrane. It is also known as foramen arcuale atlantis, ponticulus posticus or posterior ponticle, or Kimerle anomaly. Vertebral arteries pass through this foramen. It is seen in about 8% and is more common in females. It can be unilateral or bilateral, or complete or incomplete.
  • Two superior articular facets of the lateral masses anterior and posterior [instead of single]
  • Absent central part of the posterior arch
  • Partial or complete fusion with occiput or axis
  • Three centers – anterior ossification center, and paired lateral mass ossification centers. [week 7]
  • The paired lateral mass ossification centers extend to the posterior arch.
  • Unification at the posterior arch –  3-4 years
  • Anterior ossification center unites with the lateral mass ossification center at years 6-8.
  • Sometimes two anterior ossification centers present.

 

Vertebra Prominens or Seventh Cervical Vertebra [C7]

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Vertebra prominens is the common name for 7th cervical vertebra or C7, the largest and most inferior vertebra of the cervical region of the spine.

It is named because it has a large spinous process that protrudes posteriorly and can be felt prominently on palpation.

Vertebra prominens is easily recognized on palpation of the back of the neck from above downwards because of its palpation.

Cervical spine is formed by seven vertebras named as C1 to C7.  First vertebra is known as atlas and second as axis. Third to sixth cervical vertebra are typical in anatomical structure. But as the cervical spine approaches its end, its last vertebra or seventh cervical vertebra, C7 changes in shape.

[read more on cervical spine anatomy]

This vertebra prominens is used as a landmark in the clinical examination for numbering the vertebra during spine examination

c7.png

Structural Features

The transverse processes are comparatively large in size, the posterior root is larger than the anterior. The anterior tubercle is absent. The foramen transversarium is relatively small, sometimes double, or may be entirely absent.

The anterior root of the transverse process may sometimes be separate and form cervical rib.

The upper surface of transverse processes usually bears a shallow sulcus for the eighth spinal nerve.

The spinous process is thick, long and nearly horizontal going straight back. Unlike other cervical vertebrae, It is not bifid but ends in a tubercle.

C7 vertebra forms joints with C6 vertebra above and T1 vertebra below.

Attachments

  •  Tip of spinous process-
    • Ligamentum nuchae
    • Trapezius
    • Rhomboideus minor
    • Serratus posterior superior
    • Splenius capitis
    • Semispinalis thoracis
    • Spinalis cervicis
    • Interspinales
    • Multifidus.
  • Transverse process
    • Transmits only an accessory vertebral vein
  • Posterior tubercle
    • Suprapleural membrane
  • Lower border
    • Levator costarum.

Clinical significance

Anatomical Landmark

In most of the people, C7 is most prominent vertebra and is considered as a landmark in clinical examination of spine. This gives a landmark to count vertebrae above and downward.

But it must be borne in the mind that only 70% of people have C7 as most prominent. In the rest, either C6 or T1 can make the most prominent vertebra. Therefore, it introduces a chance of error in such cases.

Cervical Rib

Anterior root of the C7 vertebra can form the cervical rib. It could be asymptomatic in most of the people but can give rise to Thoracic outlet syndrome.

 

Anatomy of Cauda Equina

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The cauda equina is a structure within the lower end of the spinal column of most vertebrates, that consists of nerve roots and rootlets from above[from second lumbar to coccygeal nerve] which originate in the conus medullaris of the spinal cord.

Cauda equina is named so because it resembles horse’s tail.

In humans, the spinal cord stops growing in infancy but the bones of the spine continue growing. At the birth, the spinal cord ends at L3 level but in adults, it ends at about the level of the vertebra L1/L2. However, there is some variation in adults and the cord may end anywhere between vertebrae T12 to L3.

Individual spinal nerve roots arise from the spinal cord as they do closer to the head, but as the differential growth occurs the top end of the nerve stays attached to the spinal cord and the lower end of the nerve exits the spinal column at its proper level.

cauda-equina

This results in a “bundle”-like the structure of nerve fibers that extends caudally from the end of the spinal cord, gradually declining in number further down as individual pairs leave the spinal column.

At the base of the Cauda Equina, there are approximately 10 fiber pairs, 3-5 lumbar, 5 sacral, and the single coccygeal nerve.

All these roots and rootlets down the vertebral column give the appearance of a horse’s tail, which is the meaning of the Latin name cauda equina.

Cauda Equina Anterior View

Significance  of Cauda Equina

Spinal Tap

Cauda equina is the part of the spinal cord where a lumbar puncture is performed in order to obtain a sample of cerebrospinal fluid (CSF) for diagnostic purposes. Lumbar puncture.

It is commonly referred to as a “spinal tap” and is usually performed at the L3 or L4 intervertebral level. Cauda equina syndrome (CES) is a serious neurologic condition in which there is an acute loss of function of the neurologic elements (nerve roots) of the spinal canal below the termination (conus) of the spinal cord.

Cauda Equina Syndrome

Cauda equina syndrome is a characteristic pattern of weakness involving the spinal nerves that causes a motor weakness in the lower limb, urinary bladder weakness and typical sensory deficit in the perineal area.

Typical symptoms are back pain, pain radiating to lower limb [unilateral or bilateral],  saddle sensory anesthesia.

There would be bladder and bowel dysfunction too.

Typical and Atypical Thoracic Vertebra

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The typical thoracic vertebrae are seven in number and atypical thoracic vertebra are five in number.

Vertebra T2 to T8 are typical and rest of them are atypical.

Both typical and atypical thoracic vertebrae are discussed.

Typical Thoracic Vertebra

Thoracic Vertebra

body is heart shaped with roughly the same measurements from side to side and anteroposteiroly. On each side it bears 2 costal facets (demifacets). The superior costal facets are larger and placed on the upper border of the body near the pedicle. They articulate with the head of the numerically corresponding rib. The inferior costal facets are smaller and placed on the lower border in front of the inferior vertebral notch. They articulate with the next lower rib.

The vertebral foramen is comparatively small and circular.

The vertebral Arch

  • The pedicles are directed straight backwards. The superior vertebral notch is shallow, while the inferior vertebral notch is deep and conspicuous.
  • The laminae overlap each other from above.
  • The superior articular processes project upwards from the junction of the pedicles and laminae. The articular facets are flat and are directed backwards and a little laterally and upwards. This direction permits rotatory movements of the spine.
  • The inferior articular processes are fused to the laminae. Their articular facets are directed forwards and slightly downwards and medially.
  • The transverse processes are large, and are directed laterally and backwards from the junction of the pedicles and laminae. The anterior surface of each process bears a facet near its tip, for articulation with the tubercile of the corresponding rib. In the upper 6 vertebrae, the costal facets on the transverse processes are concave and face forwards and laterally. In others the facets are flat and face upwards, laterally and slightly forwards.
  • The spine is long, and is directed downwards and backwards. The 5th to 9th spines are the longest, more vertical and overlap each other. The upper and lower spines are less oblique in direction.

Attachments on a Typical Thoracic Spine Vertebra

  • The upper and lower borders of the body give attachment, in front and behind respectively, to the anterior and posterior longitudinal ligaments.
  • The upper borders and lower parts of the anterior surfaces of the laminae provide attachment to the ligamenta flava.
  • The transverse process gives attachment to (i) the lateral costotransverse ligament (at the tip); (ii) the superior costotransverse ligament (lower border); the inferior costotransverse ligament (anterior surface); (iv) the intertransverse muscles (to upper and lower borders); (v) the levator costae (posterior surface).
  • The spines give attachment to the supraspinous and interspinous ligaments. They also give attachment to several muscles including the trapezius, the rhomboids, the latissimus dorsi, the serrate posterior superior and inferior, and many deep muscles of the back.

Atypical Thoracic Vertebrae

First Thoracic Vertebra

  • The body resembles that of a cervical vertebra. It is broad and not heart shaped. Its upper surface is lipped laterally and beveled anteriorly. The superior costal facet on the body is complete. It articulates with the head of the first rib. The inferior costal facet is a “demifacet” for the second rib.
  • The spine is thick, long and nearly horizontal.
  • The superior vertebral notches are well marked, as in cervical vertebrae.

Ninth Thoracic Vertebra

It resembles a typical thoracic vertebra except that the body has only the superior costal facets (demifacets). The inferior costal facets are absent.

Tenth Thoracic Vertebra

It resembles a typical thoracic vertebra except that the body has a single complete superior costal facet on each side, extending on to the root of the pedicle.

Eleventh Thoracic Vertebrae

  • The body has a single large costal facet on each side, extending on to the upper part of the pedicle.
  • The transverse process is small and has no articular facet. Sometimes it is difficult to differentiate between vertebrae T10 and T11.

Twelfth Thoracic Vertebra

  • The shape of the body, pedicles, transverse processes and spine are similar to those of a lumbar vertebra. However, the body bears a single costal facet on each side, which lies more on the lower part of the pedicle than on the body.
  • The transverse process is small and has no facet, but has superior, inferior and lateral tubercles.
  • The inferior articular facets are lumbar in type and are directed laterally (everted), but the superior articular facets are thoracic in type.

Dorsal Scapular Nerve Entrapment Syndrome

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The dorsal scapular nerve entrapment is a relatively less common nerve entrapment that causes shoulder and arm pain. It is vulnerable during brachial plexus injections as the nerve passes through the middle scalene muscle.

Dorsal scapular nerve entrapment is uncommon and therefore frequently underrecognized cause of pain in shoulder and neck area.

The symptoms are easily mistaken for other problems.

Relevant Anatomy

Anatomy of Dorsal Scapular Nerve

Understanding anatomy of nerve is crucial for diagnosis dorsal scapular nerve entrapment
Nerves to scapula, Image credit: Musculoskeletal Key

The dorsal scapular nerve arises from the brachial plexus, usually from the cervical nerve C5. After leaving C5, it commonly pierces the middle scalene muscle and continues beneath the undersurface of levator scapulae and the rhomboids.

It provides motor innervation to the rhomboid muscles, which pull the scapula towards the spine and levator scapulae muscle, which elevates the scapula.

The course of the nerve is accompanied by one of two arteries: either the dorsal scapular artery that arises from the third part of the subclavian artery or deep branch of the transverse cervical artery [when the other artery is absent].

It is a branch of the thyrocervical trunk which is a branch of the first part of the subclavian artery,

The dorsal scapular nerve supplies the levator scapulae muscles,  the rhomboid major and minor muscles.

The rhomboids minor and major muscles connect the medial edge of the scapula to the spinal column. Both rhomboid muscles pull the scapula towards the midline (scapular adduction) and they also pull the scapula superiorly with downward rotation, function opposite to serratus anterior.

Anatomy of Rhomboids and Levator Scapulae

Rhomboids

rhomboids muscles origin and insertion

There are two rhomboids are two muscles – rhomboid major & rhomboid minor.
Rhomboid major originates from spinous Processes T2-T5 and inserted on to medial border of scapula from level of the spine to inferior angle

Rhomboid Minor originates from nuchal ligament and spinous Processes C7 & T1. It inserts on a triangular area of the medial end of the medial end of the scapular spine
Both the rhomboids lie deep to trapezius and form parallel bands that pass inferolaterally from the vertebrae to the medial border of the scapula. The two are often separated by a small space between but in some cases, one single blended muscle may be present.

Levator Scapulae

Levator scapulae muscle
It originates from the posterior tubercle of the first four transverse processes of cervical vertebrae and is inserted into medial border of the scapula extending from superior angle to junction of the spine and medial border of the scapula.

Causes of Dorsal Scapular Nerve Entrapment

  • Entrapment in scalenus medius muscle
  • Direct injury to the nerve
    • Severe C5 root lesion or avulsion.[Brachial plexus injuries]
    • Anterior shoulder dislocation
  • C5 radiculopathy has also been suggested as a causative factor.

[In overhead athletics, a muscle injury to rhomboids may cause rhomboids palsy leading to winging of the scapula and mimicking dorsal scapular nerve entrapement]

Clinical Presentation and Diagnosis

Injury/entrapment of dorsal scapular nerve causes weakness of the levator scapulae and the rhomboid muscles and results in a winging of the scapula.

[Scapular winging refers to the abnormal protrusion of scapula on patients back. It occurs because of paralysis of stabilizing muscles of the scapula. Serratus anterior and trapezius are common causes whereas rhomboids weakness is an uncommon cause.

The scapular winging in dorsal scapular nerve syndrome is not as severe as seen with serratus anterior muscle and trapezius.]

The usual complaint in dorsal scapular nerve entrapment is a history of the abnormal movement of the shoulder joint, and stiff joint. The patient may also complain of pain in the shoulder region.

On examination,  as noted before, there could be scapular winging. The scapula may become laterally displaced with an upward motion.

When asked to bring the scapulae together [adduct], the patient is not able to do so or the affected side is less adducted. Palpation of the contracted rhomboideus muscles would confirm the weakness.

When the patient is asked to move the arm forward on elevation will result in the medial border of the scapula being lifted and pulling on the inferior angle of this bone.

An electromyogram would help in confirmation of diagnosis.

MRI scan helps to diagnose roots avulsions.

Treatment of Dorsal Scapular Nerve Entrapment

Treatment usually is conservative which includes

  • Cervical stabilization
    • Cervical collar
    • Cervical traction
  • Muscle relaxants
  • NSAIDs
  • Physical therapy
    • Strengthening of the trapezius [middle trapezius provides compensation for loss of rhomboids]
  • Local steroid block for muscle

Surgery can be considered in severe cases that are unresponsive to conservative treatment.

The procedures are

  • Fascial sling operation
    • Two fascia lata grafts are used to connect the lower medial border of the scapula to the spinal muscles and the inferior angle of the scapula to the latissimus dorsi.
    • This anchors the scapula to the posterior thoracic wall, eliminating winging.
    • Grafts may stretch or fail with time
  • Neurolysis or nerve decompression
    • Suggested as last resort

References

  • Tubbs RS, Tyler-Kabara EC, Aikens AC, Martin JP, Weed LL, Salter EG, Oakes W. Surgical anatomy of the dorsal scapular nerve. J Neurosurg. 2005 May; 102(5):910-1.
  • Fisher MA, Gorelick PB. Entrapment neuropathies. Differential diagnosis and management. Postgrad Med. 1985 Jan; 77(1):160-74.
  • Jerosch J, Castro WH, Geske B, Damage of the long thoracic and dorsal scapular nerve after traumatic shoulder dislocation: case report and review of the literature.Acta Orthop Belg. 1990; 56(3-4):625-7.
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