bony variation

Question 1

what is the axial skeleton formed from?

Answer 1

the sclerotome component of somites

Question 2

in the thorax what forms the ribs?

Answer 2

the costal processes elongates to form the ribs that articulate w/ the vertebral bodies and transverse processes

Question 3

how does alteration in the number and orientation of ribs arise?

Answer 3

alteration in the standard pattern of development

Question 4

changes in the axial skeleton are assoc w/ altered expression of which gene?

Answer 4

Hox gene

Question 5

what is the most common rib anomaly?

Answer 5

the presence of an additional rib at the base of the neck (C7) aka cervical supernumerary rib

Question 6

what causes cervical ribs?

Answer 6

the signalling intended to elongate the costal process of T1 also affecting C7

Question 7

why is the true incidence of cervical ribs unknown?

Answer 7

because they are often v small and so go unnoticed

Question 8

what are the symptoms of cervical ribs?

Answer 8

ofte asymptomatic

can cause compression of the brachial plexus and subclavian vessels (thoracic outlet syndrome is seen in ~10% of pts w/ cervical ribs)

Question 9

what is an inter thoracic rib?

Answer 9

the rib does not form part of the thoracic cage but instead lies inside it

Question 10

what is the incidence of interthoracic ribs?

Answer 10

very rare - only 40 cases reported in the literature since 1947

Question 11

how many types of inter thoracic ribs are there and what is this based on?

Answer 11

4 types

based on the position and orientation (Kamans et al 2006)

Question 12

what are the 3 potential causes of inter thoracic ribs?

Answer 12

thoracic super numerary rib
local depression of a rib
supernumerary varian of a bifid rib

Question 13

what are the symptoms of inter thoracic ribs?

Answer 13

often asymptomatic
can cause pain if attached to the diaphragmatic pleura

Question 14

what is the management for inter thoracic ribs?

Answer 14

no treatment needed if not causing any issues

Question 15

how do vertebrae develop?

Answer 15

sclerotome component of somites > condense around the notochord > resegmentation > vertebral body

Question 16

how is the vertebral arch formed?

Answer 16

from the vertebral body, cells migrate towards the spinal cord to form the vertebral arch

Question 17

how does vertebral body variation arise?

Answer 17

disruption of the migration and development of the sclerotome cells

Question 18

what is a limbus vertebrae?

Answer 18

when a fragment of the nucleus pulpous herniates through the ring of surrounding tissue before fragmentation has occurs

Question 19

what does limbus vertebrae create?

Answer 19

an ossified fragment at the superior edge of the vertebral body

Question 20

what can limbus vertebrae be confused w/?

Answer 20

fracture of the superior endplate

Question 21

what condition is limbus vertebrae closely related to?

Answer 21

schmorls nodes

Question 22

how does segmentation failure occur and what does this lead to?

Answer 22

occurs when the IV disc does not develop fully, leading to partially fused vertebrae w/ an incomplete disc space

Question 23

what can segmentation failure be confused w/?

Answer 23

inflammatory spondylits

Question 24

how does butterfly vertebrae arise?

Answer 24

the notochord persists and so the two halves of the vertebrae do not fuse and the vertebral body is formed in two halves

Question 25

how does unfused spinous process arise?

Answer 25

failure in fusion of the neural arch leading to a true bony gap in the spinous process

Question 26

what can arise from unfused spinous process and why?

Answer 26

CNS abnormalities because the backbone that protects the spinal cord is not complete and so the spinal cord can get damaged

Question 27

what is unfused spinous process often confused w/?

Answer 27

fracture

Question 28

what causes enlargement of the spinous process?

Answer 28

spinous process hyperplasia (enlargement of the spinous process due to an increase in cell number)

Question 29

what can spinous process enlargement be confused w/?

Answer 29

a spinal mass

Question 30

name 3 other variations in the vertebrae

Answer 30

accessory tubercles presence of foramina vertebrae fused together

Question 31

what is the prevalence of supernumerary ribs in the lumbar region?

Answer 31

<2%

Question 32

what are the symptoms of lumbar supernumerary ribs?

Answer 32

asymptomatic because they do not cause any compression issues therefore usually an incidental finding

Question 33

what is major impact limb variation?

Answer 33

entire bone / part of the bone missing

Question 34

give an example of major limb variation

Answer 34

radial deficiency and ulnar deficiency

Question 35

how do major changes the limb arise?

Answer 35

early development patterns being altered

Question 36

how do minor impact changes to the limb present?

Answer 36

usually silent because they cause little functional affect

Question 37

give 2 examples of bony changes in the limb that can lead to misdiagnosis

Answer 37

accessory bones in the feet are quite common and can be mistaken for tumours sesamoid bones inside tendons are quite common and occur in response to stress on the tendon

Question 38

what are the implications of bony overgrowth of foramina, formation of bony tunnels or spurs?

Answer 38

may compress neurovasculature

Question 39

where is the most reported bony spur located and what can this cause clinically?

Answer 39

most reported bony spur is on the distal end of the humerus can cause compression of the median nerve and / or brachial artery

Question 40

what are the findings of Kazanci et al (2012)?

Answer 40

C6 unilateral hyperplasia of the lamina and schisis of the spinous process in a 20y/o pt who presented following a car accident w/ no funcitnal issues from the hyperplasia the hyperplasia was differentiated from a traumatic lesion using CT and MRI

Question 41

apart from the spinous process where else in the head and neck has hyperplasia been reported?

Answer 41

the styloid process

Question 42

what can cause further elongation of the spinous process?

Answer 42

ossification of the stylohyoid ligament

Question 43

what is the risk of styloid process hyperplasia?

Answer 43

it can compress the pharynx and make swallowing difficult

Question 44

what are the clinical implications of fusion of the atlas to the base of the skull?

Answer 44

no movement between the skull and C1 can alter the course of the vertebral artery and C1 spinal nerve and may compress them

Question 45

what are the findings of Ma et al (2012) in their study regarding the pterion?

Answer 45

investigation of the pterion and middle meningeal artery found that the pterion was not the thinnest part in 70% of pts the middle meningeal artery was enclosed in a bony tunnel in one third of patients the middle meningeal artery did not pass close to the pterion