bony variation Flashcards
what is the axial skeleton formed from?
the sclerotome component of somites
in the thorax what forms the ribs?
the costal processes elongates to form the ribs that articulate w/ the vertebral bodies and transverse processes
how does alteration in the number and orientation of ribs arise?
alteration in the standard pattern of development
changes in the axial skeleton are assoc w/ altered expression of which gene?
Hox gene
what is the most common rib anomaly?
the presence of an additional rib at the base of the neck (C7) aka cervical supernumerary rib
what causes cervical ribs?
the signalling intended to elongate the costal process of T1 also affecting C7
why is the true incidence of cervical ribs unknown?
because they are often v small and so go unnoticed
what are the symptoms of cervical ribs?
ofte asymptomatic
can cause compression of the brachial plexus and subclavian vessels (thoracic outlet syndrome is seen in ~10% of pts w/ cervical ribs)
what is an inter thoracic rib?
the rib does not form part of the thoracic cage but instead lies inside it
what is the incidence of interthoracic ribs?
very rare - only 40 cases reported in the literature since 1947
how many types of inter thoracic ribs are there and what is this based on?
4 types
based on the position and orientation (Kamans et al 2006)
what are the 3 potential causes of inter thoracic ribs?
thoracic super numerary rib
local depression of a rib
supernumerary varian of a bifid rib
what are the symptoms of inter thoracic ribs?
often asymptomatic
can cause pain if attached to the diaphragmatic pleura
what is the management for inter thoracic ribs?
no treatment needed if not causing any issues
how do vertebrae develop?
sclerotome component of somites > condense around the notochord > resegmentation > vertebral body
how is the vertebral arch formed?
from the vertebral body, cells migrate towards the spinal cord to form the vertebral arch
how does vertebral body variation arise?
disruption of the migration and development of the sclerotome cells
what is a limbus vertebrae?
when a fragment of the nucleus pulpous herniates through the ring of surrounding tissue before fragmentation has occurs
what does limbus vertebrae create?
an ossified fragment at the superior edge of the vertebral body
what can limbus vertebrae be confused w/?
fracture of the superior endplate
what condition is limbus vertebrae closely related to?
schmorls nodes
how does segmentation failure occur and what does this lead to?
occurs when the IV disc does not develop fully, leading to partially fused vertebrae w/ an incomplete disc space
what can segmentation failure be confused w/?
inflammatory spondylits
how does butterfly vertebrae arise?
the notochord persists and so the two halves of the vertebrae do not fuse and the vertebral body is formed in two halves
how does unfused spinous process arise?
failure in fusion of the neural arch leading to a true bony gap in the spinous process
what can arise from unfused spinous process and why?
CNS abnormalities because the backbone that protects the spinal cord is not complete and so the spinal cord can get damaged
what is unfused spinous process often confused w/?
fracture
what causes enlargement of the spinous process?
spinous process hyperplasia (enlargement of the spinous process due to an increase in cell number)
what can spinous process enlargement be confused w/?
a spinal mass
name 3 other variations in the vertebrae
accessory tubercles
presence of foramina
vertebrae fused together
what is the prevalence of supernumerary ribs in the lumbar region?
<2%
what are the symptoms of lumbar supernumerary ribs?
asymptomatic because they do not cause any compression issues
therefore usually an incidental finding
what is major impact limb variation?
entire bone / part of the bone missing
give an example of major limb variation
radial deficiency and ulnar deficiency
how do major changes the limb arise?
early development patterns being altered
how do minor impact changes to the limb present?
usually silent because they cause little functional affect
give 2 examples of bony changes in the limb that can lead to misdiagnosis
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
what are the implications of bony overgrowth of foramina, formation of bony tunnels or spurs?
may compress neurovasculature
where is the most reported bony spur located and what can this cause clinically?
most reported bony spur is on the distal end of the humerus
can cause compression of the median nerve and / or brachial artery
what are the findings of Kazanci et al (2012)?
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
apart from the spinous process where else in the head and neck has hyperplasia been reported?
the styloid process
what can cause further elongation of the spinous process?
ossification of the stylohyoid ligament
what is the risk of styloid process hyperplasia?
it can compress the pharynx and make swallowing difficult
what are the clinical implications of fusion of the atlas to the base of the skull?
no movement between the skull and C1
can alter the course of the vertebral artery and C1 spinal nerve and may compress them
what are the findings of Ma et al (2012) in their study regarding the pterion?
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
