The calcaneal inclination angle (also known as the calcaneal pitch) is drawn on a weightbearing lateral foot radiograph between the calcaneal inclination axis and the supporting horizontal surface.
It is a measurement that reflects the height of the foot framework, but is affected by abnormal p...
The calcaneal inclination axis is drawn between the most inferior portion of the calcaneal tuberosity and the most distal and inferior point of the calcaneus at the calcaneocuboid joint on a weightbearing lateral foot radiograph.
It can be used to draw the calcaneal inclination angle.
A mnemonic for calcaneal lesions is:
B: bone cyst (unicameral)
I: intraosseous lipoma
G: ganglion (intraosseous)
G: giant cell tumor
The calcaneal tendon, commonly known as the Achilles tendon, is the strongest and largest tendon of the human body. It is also one of the commonest tendons to become injured due to its high biomechanical load but poor vascularity 2.
The calcaneal tendon forms by the merging of fi...
Avulsion fractures of the calcaneal tuberosity are rare, accounting for only 3% of all calcaneal fractures.
There are three mechanisms of action 4:
fall during plantarflexion
feet fixed on the ground with sudden muscular contraction
There is a s...
Calcaneal vascular remnant is a benign finding that may be seen on MRI of ankle and can be misinterpreted as an alarming bone lesion. It is typically located at the insertion site of sinus tarsi ligaments (cervical and interosseous ligaments).
The focus of signal alteration is believed to be pr...
The calcaneofibular ligament (CFL) is the middle ligament of the lateral collateral ligament complex of the ankle and stabilises both the ankle and subtalar joints.
The CFL is an extracapsular round cord measuring 20-25 mm long x 6-8 mm width. Its origin is distal to the anterior...
Calcaneonavicular coalition is one of the two most common subtypes of tarsal coalition, the other being talocalcaneal coalition. As with any coalition it may be osseous (synostosis), cartilaginous (synchondrosis) or fibrous (syndesmosis).
This type of coalition is more ea...
The calcaneus, also referred to as the calcaneum, is the largest tarsal bone and the major bone in the hindfoot. It articulates with the talus superiorly and the cuboid anteriorly and shares a joint space with the talonavicular joint, appropriately called the talocalcaneonavicular joint. The cal...
Calcaneus axial view is part of the two view calcaneus series, this projection is best used to asses the talocalcaneal joint and plantar aspects of the calcaneus. The axial view has a diagnostic sensitivity of 87% for calcaneus fractures 1.
patient is supine or seated with th...
Calcaneus lateral view is part of the two view calcaneus series; this projection is used to assess the calcaneus, talocrural, talonavicular and talocalcaneal joint.
the patient is in a lateral recumbent position on the table
the lateral aspect of the knee and ankle joint shou...
The calcaneus series is comprised of a lateral and axial (plantodorsal) projection. The calcaneus is the most commonly fractured tarsal bone accounting for ~60% of all tarsal fractures 1. This series provides a two view investigation of the calcaneus alongside the talar articulations and talocal...
This is a basic article for medical students and other non-radiologists
A calcaneus x-ray, also known as calcaneus series or calcaneus radiograph, is a set of two x-rays of the calcaneus. It is performed to look for evidence of injury (or pathology) affecting the leg, often after trauma.
The calcar femorale is a normal ridge of dense bone that originates from the postero-medial endosteal surface of the proximal femoral shaft, near the lesser trochanter. It is vertical in orientation, and the ridge projects laterally toward the greater trochanter. This ridge of bone provides mech...
Calcific bursitis is the result of deposition calcium hydroxyapatite crystals. It is closely related to calcific tendinitis, and many authors refer to them as being the same condition.
Calcific myonecrosis refers to a rare post-traumatic phenomenon. It characterized by latent formation of a dystrophic calcified mass occurring almost exclusively in the lower limb (it has been occasionally reported at other sites 5).
Plain radiographs typicall...
Calcific tendinitis (or calcific tendonitis) is a self-limiting condition due to deposition of calcium hydroxyapatite within tendons, usually of the rotator cuff. It is a common presentation of the hydroxyapatite crystal deposition disease (HADD).
Typically this condition affects...
Calcific tendinitis of the longus colli muscles is an inflammatory/granulomatous response to the deposition of calcium hydroxyapatite crystals in the tendons of the longus colli muscle.
This condition typically occurs in adults in middle age (20-50 years of age) with a slight pred...
Calcified intra-articular lesions have a relatively limited differential, including:
impaction fracture fragments
intraarticular avulsion fractures
Calcinosis circumscripta is a condition involving calcium deposition in the subcutaneous tissues, muscles and fascia. It is considered a localised form of calcinosis cutis universalis most often seen in the hands and feet.
Patients present with firm white dermal papules, ...
Calcinosis universalis is a condition characterized by long bands or sheets of symmetrical subcutaneous calcification.
It usually presents <20 years of age, and is more common in women.
palpable calcific plaques in subcutaneous or deeper tissue
fatigue, muscle pain, and...
Calcium pyrophosphate dihydrate disease (CPPD disease), also known as pyrophosphate arthropathy or pseudogout, is defined by the co-occurrence of arthritis with evidence of CPPD deposition within the articular cartilage.
The terminology regarding CPPD disease has been confusing, w...
Calvarial thinning can result from many causes. They include:
craniofacial syndromes 1
focal calvarial thinning
Camptocormia (bent spine syndrome or cyphose hystérique) is a rare syndrome characterized by involuntary flexion of the thoracolumbar spine with weight-bearing which reduces when laying down, and is due to isolated atrophy of the paraspinal muscles.
In a small case series (n=16), ...
Camptodactyly is a clinical or imaging descriptive term where there is a flexion contracture (usually congenital). Classically this occurs at the proximal interphalangeal joint of the little finger of the hand, although any finger may be affected.
Prevalence ~1%; one-third unilate...
Camptodactyly arthropathy coxa vara pericarditis (CACP) syndrome is a rare condition principally characterized by
congenital or early-onset camptodactyly and childhood-onset non-inflammatory arthropathy
coxa vara deformity or other dysplasia associated with progressive hip disease
Camptomelic dwarfism, also known as camptomalic dysplasia, is a rare form of skeletal dysplasia.
Camptomelic dwarfism is rare with an estimated incidence of ~1:200,000 births.
Diagnosis is usually readily made at birth or with antenatal ultrasound. It is...
Camurati-Engelmann disease (CED), also known as progressive diaphyseal dysplasia (PDD), is a rare autosomal dominant sclerosing bone dysplasia. It begins in childhood and follows a progressive course.
Common symptoms include extremity pain, muscle weakness, cranial nerve ...
Canadian C-spine rules are a set of guidelines that help a clinician decide if cervical spine imaging is not appropriate for a trauma patient in the emergency department. The patient must be alert and stable.
There are three rules:
is there any high-risk factor present that requires cervical s...
The capitate, also known as the os magnum, is the largest of the carpal bones and sits at the center of the distal carpal row. A distinctive head shaped bone, it has a protected position in the carpus.
The capitate sits in a proximo-distal direction with a waist that...
Capito-hamate coalition is the second most common type of carpal coalition and represents congenital fusion of the capitate and the hamate. It represents ~5% of all carpal fusions 1 and is associated with Apert syndrome 2.
The capitolunate angle is the angle between the long axis of the capitate and the mid axis of the lunate on the sagittal imaging of the wrist. In a normal situation it should be less than 30o in the resting (neutral) position.
The angle is increased in carpal instability such as with a dorsal i...
There is variation in the relationship between the glenoid labrum and the anterior shoulder joint capsule. This has been divided into three types:
Type 1: capsule inserts into the labrum proper
Type 2: capsule inserts into the base of the labrum, or within 1cm of the base
Type 3: capsule inse...
Carcinogens are substances known to cause cancer. They include:
Nasopharynx / nasal passage
ionising radiation (not technically a substance)
polyaromatic hydrocarbons (PAH)
The carotid tubercle is a commonly used term referring to the paired anterior tubercles of the transverse processes of the sixth cervical vertebrae 1. The carotid tubercle serves as an important landmark with respect to performing regional anesthesia such as a brachial plexus and cervical plexus...
Carpal angle is defined by two intersecting lines, one in contact with the proximal surface of the scaphoid and the lunate and the other line through proximal margins of the the triquetrum and the lunate. Its normal value is between 130° and 137°.
It is increased in (> 139°)
Carpal bone fractures comprise a range of different fractures which carry varying outcomes. They can involve one or a combination of carpal bones and also be part of fracture-dislocations.
Individual fractures include
scaphoid fracture: 50-80%
lunate fracture: 3.9%
triquetral fracture: ~18%
The carpal bones are the eight bones of the wrist that form the articulation of the forearm with the hand. They can be divided in two rows:
The names and order of these bones can be rememb...
Mnemonics of the carpal bones are numerous and useful for memorising the order and location of the bones. They usually describe the position of the carpal bones from lateral to medial in the proximal row and then the distal row:
Sam Likes To Push The Toy Car Hard
She Looks Too Pretty Try To Ca...
The carpal boss is a hypertrophied bony protuberance on the dorsal surfaces of the base of the second or third metacarpals, near the capitate and trapezium. It may be bilateral.
The condition may represent one or more of:
degenerative osteophyte formation
os styloideum (an accessor...
Carpal coalition refers to fusion of two or more carpal bones, and although the most commonly involved bones are the lunate and triquetrum, most combinations of adjacent bones can be found to be coalesced.
The estimated prevalence is ~0.1% in Caucasian Americans and ~1.5% in Afri...
Carpal height is used to diagnose and assess the severity of carpal collapse. It is defined as the distance between the base of third metacarpal and the subchondral bony cortex of the distal radius. But due to variations between individuals, it is more appropriate to calculate the carpal height ...
The carpal tunnel is a fibro-osseous canal that acts as a passageway from the forearm to the anterior hand. It is found in the anterior wrist.
superficial border (roof): flexor retinaculum
deep border (floor): carpal bones
The carpal tunnel contains the fo...
Carpal tunnel syndrome results from compression of the median nerve within the carpal tunnel. It is a cause of significant disability and is one of three common median nerve entrapment syndromes, the other two being anterior interosseous nerve syndrome and pronator teres syndrome.
Carpal tunnel syndrome results from compression of the median nerve within the carpal tunnel. Its causes are numerous and varied.
A useful mnemonic to remember the causes is:
D: diabetes mellitus
Carpenter syndrome, also called acrocephalopolysyndactyly type II (ACPS type II) is an extremely rare autosomal recessive congenital disorder
It is characterized by number of features which include:
kleeblattschädel (cloverleaf ...
Carpometacarpal (CMC) joint dislocations are uncommon dislocations of the hand.
There is a strong younger male predominance. These injuries account for less than 1% of hand injuries 4 and are more common in the dominant hand.
Carrying angle is a small degree of cubitus valgus, formed between the axis of a radially deviated forearm and the axis of the humerus. It helps the arms to swing without hitting the hips while walking.
Normally it is 5-15o away from the body or 165-175o towards the body.
A decreased carrying ...
Cartilage interface sign, also referred to as double cortex sign, refers to the sonographic presence of a thin markedly hyperechoic line at the interface between the normally hypoechoic hyaline articular cartilage of the humeral head and an abnormally hypoechoic supraspinatus tendon. This arises...
Cartilaginous joints are a type of joint where the bones are entirely joined by cartilage, either hyaline cartilage or fibrocartilage. These joints generally allow more movement than fibrous joints but less movement than synovial joints.
Primary cartilaginous joint
These cartilaginous joints...
The differential for cartilagenous lesions includes:
The cases featured in these video lectures are specifically selected to teach important concepts in radiology over a broad range of topics. The tutorials vary in difficulty from basic to advanced. For maximum learning, try the cases for yourself in Radiopaedia quiz mode first.
We love this ser...
The Castellvi classification is used for lumbosacral transitional vertebra (LSTV):
type I: enlarged and dysplastic transverse process (at least 19 mm)
type II: pseudoarticulation of the transverse process and sacrum with incomplete lumbarisation/sacralisation; en...
The Caton-Deschamps index is a ratio that is used in everyday practice as well as in research to measure patellar height and allows the diagnosis of patella alta and patella baja.
The Caton-Deschamps index is the ratio between the distance between the lower pole of the pa...
The Catterall classification is based on radiographic appearances of the epiphysis and metaphysis visible in osteonecrosis of the femoral head:
bone absorption changes visible in the anterior aspect of the epiphysis of femoral head
changes are visible best in frog leg lateral view
There are several important causes of an abnormal lunate signal on MRI, the most frequent causes being Kienbock disease (25%), ulnar impaction syndrome (25%) and intraosseous ganglia (20%).1 Appreciation of the pattern of bone signal change can often allow the correct diagnosis to be made.
A useful mnemonic for remembering the causes of cone-shaped epiphysis is:
A: achondroplasia, acrodysostosis
B: Beckwith-Wiedemann syndrome
C: chondroplasia punctata, Cockayne syndrome, conorenal syndrome, cleidocranial dysplasia, cartilage-hair hypoplasia
A mnemonic for remembering the symmetric vs asymmetric causes of sacroiliitis is:
P: psoriatic arthritis
A: ankylosing spondylitis
I: inflammatory bowel disease related
R: reactive (e.g. Reiter syndrome)
The outside letters P & R (letters are far apart) are the asymmetric ca...
Cavernous venous malformation, also traditionally referred to as a cavernous hemangioma (despite it not being a tumor) or cavernomas, are non-neoplastic slow flow venous malformations found in many parts of the body.
Despite the ubiquity of use of the traditional terms cavernoma, ...
Celery stalk metaphysis refers to a plain film appearance of the metaphyses in a number of conditions characterized by longitudinally aligned linear bands of sclerosis. They are seen in:
congenital cytomegalovirus (CMV)
The celery stalk sign is a term given to the appearance of the anterior cruciate ligament which has undergone mucoid degeneration and has been likened to that of a celery stalk. Its low signal longitudinal fibers are separated from each other by higher signal mucinous material, best appreciated ...
Cellulitis (more specifically referred to as superficial cellulitis) is an acute infection of the dermis and subcutaneous tissues. It results in pain, erythema, edema, and warmth. Since the epidermis is not involved, cellulitis is not transmitted by person-to-person contact.
Cenani-Lenz syndactyly (CLS) is a very syndrome primarily characterized by:
syndactyly/oligodactly: syndactyly is often complete and gives a spoon hand type appearance
It carries an autosomal recessive inheritance.
It was first described...
The central sacral vertical line (CSVL) is used in the assessment of spinal scoliosis.
It is a line constructed on frontal films of the spine and pelvis to measure coronal balance, drawn as follows:
a line connecting the top of the iliac crests is drawn
a second line is drawn perpendicular t...
Cerclage wire refers to a type of orthopedic fixation/stabilisation wire placed to approximate fractured bone fragments.
full - 360° circumferential wire used in diaphysis segments of long bones
hemicerclage - wire is placed through one of the main fractured bone fragments, as used in t...
Cerebrotendinous xanthomatosis is an autosomal recessive lipid storage disorder caused by defects in sterol-27-hydroxylase enzyme in bile acid synthesis. This leads to early cataract formation, atherosclerosis, hypercholesterolemia, and tendinous xanthomas.
Cervical canal stenosis can be acquired (e.g. trauma, discs, and ossification of the posterior longitudinal ligament) or congenital. It refers to narrowing of the spinal canal, nerve root canals, or intervertebral foramina of the cervical spine.
normal AP diameter is ~17 ...
Cervical degenerative disease can be graded using a very old but reliable classification given by Kellgren et al. It is based on findings on a lateral cervical spine radiograph although it can also be applied to MRI evaluation of spine.
The key parameters are osteophyte formation, intervertebra...
The cervical ligament attaches to the calcaneus and talus. It is lateral to the tarsal sinus and medial to the attachment of extensor digitorum brevis. It is taut in inversion.
Cervical ribs are supernumerary or accessory ribs arising from the seventh cervical vertebra. They occur in ~0.5% of the population, are usually bilateral, but often asymmetric 2, and are more common in females.
Although cervical ribs are usually asymptomatic, they are the most important anato...
The cervical spine is the upper part of the spine extending from the skull base to the thorax at the level of the first vertebra with a rib attached to it. It normally consists of seven vertebrae. Its main function is to support the skull and maintain the relative positions of the brain and spin...
The AP oblique cervical spine projections are supplementary views to the standard AP, odontoid and lateral c-spine series. It can be taken either as an anterior oblique or posterior oblique projection.
patient is standing erect with either the left or right posterior side clos...
Cervical spine flexion-extension lateral views are specialized projections of the cervical spine often requested to assess for spinal stability.
Cervical spine flexion-extension lateral views should not be performed on trauma patients without strict instructions of a qualified clinician.
A floating pillar, also referred as pedicolaminar fracture-separation injury, is characterized by fractures through the pedicle and lamina of a cervical spine vertebrae creating a free-floating articular pillar fragment. It is an unstable cervical spine fracture that results from hyperflexion–la...
There are several cervical spine fracture classification systems:
Anderson and D'Alonzo classification (odontoid fracture)
Roy-Camille classification (odontoid fracture)
Levine and Edwards classification (for traumatic injuries to axis)
Allen and Ferguson classification (subaxial spine injur...
Cervical spine fractures can occur secondary to exaggerated flexion or extension, or because of direct trauma or axial loading.
The cervical spine is susceptible to injury because it is highly mobile with relatively small vertebral bodies and supports the head which is both heavy and...
The closed mouth odontoid AP view (Fuchs view) is a nonangled AP radiograph of C1 and C2. This view focuses primarily on the odontoid process. The standard Fuchs view should not be used in a trauma setting and the modified Fuchs view may be used instead.
supine or erect
Cervical spine injuries can involve the cervical vertebral column, intervertebral discs and cervical spine ligaments, and/or cervical spinal cord. The cervical spine accounts for ~50% of all spinal injuries.
5-10% of patients with blunt trauma have a cervical spine injury 1.
Cervical spine lateral view is a lateral projection of the cervical spine. It is often performed in the setting of trauma.
As technology advances, computed tomography (CT) has replaced this projection, yet there remain many institutions (especially in rural areas) where CT is not readily availa...
Cervical spine ligaments ordered from anterior to posterior include:
anterior longitudinal ligament (ALL)
anterior atlanto-occipital membrane
alar ligaments (paired)
cruciate ligament of the atlas
longitudinal band: joins the body of the axis to the foramen magnum
The odontoid or 'peg' projection is an AP projection of C1 (atlas) and C2 (axis).
patient positioned erect in AP position unless trauma the patient will be supine
patient’s shoulders should be at equal distances from the image receptor to avoid rotation, the head facing strai...
The PA oblique cervical spine projections are supplementary views to the standard AP, Odontoid and lateral c-spine series. It can be taken either as an anterior oblique or posterior oblique projection. This projection can be used to visualize the intervertebral foramina.
The term cervical stenosis can refer to:
stenosis of the uterine cervix
bony cervical canal stenosis (cervical spinal stenosis)
Chalk stick, also known as carrot stick fractures, are fractures of the fused spine, classically seen in ankylosing spondylitis.
Some authors define the chalk stick fracture as a fracture through a Pagetoid long bone (see Paget disease) 3.
They usually occur through the...
Chamberlain line is a line joining the back of hard palate with the opisthion on a lateral view of the craniocervical junction.
It helps to recognize basilar invagination which is said to be present if the tip of the dens is >3 mm above this line.
McGregor developed a modificatio...
The champagne glass pelvis is a helpful sign in achondroplasia in which the iliac blades are flattened, giving rise to a pelvic inlet that resembles a champagne glass. The acetabular angles are flattened (horizontal) and the sacrosciatic notch is small.
Chance fractures, also referred to as seatbelt fractures, are flexion-distraction type injuries of the spine that extend to involve all three spinal columns. These are unstable injuries and have a high association with intra-abdominal injuries.
They tend to occur from a fl...
Charcot joint, also known as a neuropathic joint or Charcot (neuro/osteo)arthropathy, refers to a progressive degenerative/destructive joint disorder in patients with abnormal pain sensation and proprioception.
In modern Western societies by far the most common cause of Charcot jo...
The causes of a Charcot joint can be remembered, using a mnemonic - with a little poetic license - as they (all) start with the letter S.
s: sugar (diabetes)
s: steroid use
s: spinal cord injury
s: spina bifida
s: scaly disease (l...
Chauffeur fractures (also known as Hutchinson fractures or backfire fractures) are intra-articular fractures of the radial styloid process. The radial styloid is within the fracture fragment, although the fragment can vary markedly in size.
These injuries are sustained eit...
The Chauveaux–Liet angle (CL angle) is represented by the difference between the angle of verticalization (α) and morphologic angle (β) of the calcaneus (CL angle = α − β).
Angle α is the calcaneal pitch angle or angle of verticalization of calcaneus described as the intersection of the baselin...
The Cheerio sign has been described as a sign seen in a type III superior labral anterior posterior tear (SLAP lesion) of the glenoid labrum. In the cheerio sign, a rounded core of soft tissue is surrounded by a rim of contrast material and gas.
SLAP type III is the bucket handle tear of the s...
Chest wall lipomas are benign fat containing thoracic lesion.
While they can occur at any age, they typically occur in older patients who are 50-70 years of age, and they are most frequent in those with increased an increased body mass index.
They are well-circumscrib...