The apophysis of the proximal 5th metatarsal lies laterally and is oriented longitudinally parallel to the shaft.
Apophysis of the fifth metatarsal base appears on plain radiographs at age 12 for boys and 10 for girls. Fusion of the apophysis to the metatarsal base usually occurs within the fol...
This is a basic article for medical students and other non-radiologists
Appendicular films are x-rays taken of the bones and joints of the arms and legs. I've used this term to separate the x-rays taken as part of an assessment of non-acute disease from trauma films which represent x-rays taken...
The appendicular skeleton is the portion of the bony skeleton that includes and supports the limbs (the appendages). It includes the pectoral girdle and the bony pelvis, connected to the axial skeleton centrally and is composed of 126 bones in total.
Appendicular bones form from cartilage, by ...
The apple core sign has been used to describe the circumferential erosion of the femoral neck seen in synovial chondromatosis. Although this is the most common process that may lead to an apple core erosion of the femoral neck, this has also been observed with:
pigmented villonodular synovitis
The arcade of Frohse (pronounced "\ Frəʊs \" to rhyme with "crows") is also known as the supinator arch.
The arcade is formed by a fibrous band between the two heads of the supinator muscle. The deep branch of the radial nerve passes beneath the arcade accompanied by vessels known as the leash ...
The arcuate foramen (foramen arcuale atlantis, ponticulus posticus or posterior ponticle, or Kimerle anomaly) is a frequently encountered normal variant of the atlas and is easily appreciated on a lateral plain film of the cranio-cervical junction.
It develops by calcification of the posterior ...
The arcuate ligament is part of the posterolateral ligamentous complex of the knee that is variably present, being found in ~65% (range 47.9-71%) of knees. It is a Y-shaped thickening of the posterolateral capsule, which arises from the fibular styloid and divides into two limbs:
medial limb: c...
The arcuate line is located at roughly one-third of the distance from the pubic crest to the umbilicus. It is the demarcation where the internal oblique and transversus abdominis aponeuroses of the rectus sheath start to pass anteriorly to the rectus abdominis muscle, leaving only the transversa...
The arcuate sign is often a subtle but important finding on knee x-rays and represents an avulsion fracture of the proximal fibula at the site of insertion of the arcuate ligament complex, and is usually associated with cruciate ligament injury (~90% of cases) 2. The fracture fragment is attache...
The arm is part of the upper limb below the pectoral girdle and above the forearm, comprising the humerus.
The elbow joint is inferior and the glenohumeral joint is superior. Arm flexion, extension, abduction, adduction, internal rotation and external rotation occur at the shoulder.
Arnold-Hilgartner classification is a plain radiograph grading system for haemophilic arthropathy of the knee 1,2:
stage 0: normal joint
stage I: no skeletal abnormalities, soft-tissue swelling is present
stage II: osteoporosis and overgrowth of the epiphysis, no cysts, no narrowing of the ca...
Arrested pneumatisation of the skull base is an anatomical variant that most commonly occurs in association with the sphenoid sinus. It is known that the sphenoid bones undergo early fatty marrow conversion antecedent to normal pneumatisation. However, for unclear reasons, some individuals exper...
Arthrofibrosis is a complication of injury or trauma to a joint. It can also be iatrogenic e.g. post knee surgeries. It consists of excessive scar tissue formation within the joint capsule, resulting in pain, stiffness, and swelling, that are greater than expected in the given clinical scenario....
Arthrogryposis (multiplex congenita) is a clinical or imaging descriptor that denotes congenital non-progressive joint contractures involving two or more body regions.
It is thought to occur in approximately 1:3000-10,000 live births 6,8.
It can result from a number o...
An easy to remember mnemonic for the causes of articular cartilage calcification is:
W: Wilson disease
The articularis cubiti is a muscle in the posterior compartment of the arm:
origin: posterior surface of the distal humerus
insertion: posterior surface of the elbow joint capsule
innervation: radial nerve
action: tenses the posterior elbow joint capsule during elbow extension
The articularis genu is a small flat muscle of the anterior knee. During knee extension it acts to tighten the synovial membrane superiorly thereby preventing impingement of the synovial folds between the femur and the patella.
origin: anterior distal femoral shaft
insertion: knee joi...
Aseptic loosening is considered relatively common complication of hip joint replacements. It is usually considered a long-term complication and is often considered as the most common complication 3.
Aseptic loosening can occur as a result of inadequate initial fixation, mechanical lo...
The American Spinal Injury Association (ASIA) was developed by the American Spinal Injury Association in 2006, and at the time of writing (July 2016), remains the most widely used scale.
This scale is part of the ASIA spinal cord injury classification. It divides spinal cord injuries into 5 cat...
Asphyxiating thoracic dysplasia, also known as Jeune syndrome, is a type of rare short limb skeletal dysplasia, which is primarily characterised by a constricted long narrow thoracic cavity, cystic renal dysplasia and characteristic skeletal features. It is also sometimes classified as one of th...
Atelosteogenesis (AO) refers to a group of lethal skeletal dysplasias.
atelosteogenesis type I
atelosteogenesis type II
atelosteogenesis type III 4
Athletic pubalgia refers to pain around the pubic symphysis and can have different causes, including what has become known as sports hernia or sportman's hernia and osteitis pubis.
Athletic pubalgia is a clinical syndrome of chronic lower pelvic and groin pain, usually encountered in athletes. ...
Atlanto-axial subluxation is a disorder of C1-C2 causing impairment in rotation of the neck. The anterior facet of C1 is fixed on the facet of C2. It may be associated with dislocation of the lateral mass of C1 on C2.
Down syndrome (20%)
Atlanto-occipital assimilation is the fusion of the atlas (C1) to the occiput and is one of the transitional vertebrae.
Atlanto-occipital assimilation occurs in approximately 0.5% (range 0.25-1%) of the population 2-4.
It is typically asymptomatic but sym...
Atlanto-occipital dissociation injuries are severe and include both atlanto-occipital dislocations and atlanto-occipital subluxations.
The tectorial membrane and alar ligaments provide most of the stability to the atlanto-occipital joint, and injury to these ligaments results in inst...
The atlas is the first cervical vertebra, commonly called C1. It is an atypical cervical vertebra with unique features. It articulates with the dens of the axis and the occiput, respectively allowing rotation of the head, and flexion, extension and lateral flexion of the head. Unlike the rest o...
Atraumatic fractures, as the name suggests, occur with no trauma or minimal trauma that would not normally be expected to result in a fracture 1. They can be:
atypical fractures, e.g. bisphosphonate-related proximal femoral fractures
Of the cervical vertebrae, the atlas (C1), axis (C2) and vertebra prominens (C7) are considered atypical cervical vertebrae.
The atlas (C1) lacks a body or spinous process. It has an anterior and posterior arches with lateral masses. Its superior articular surfaces articulate with the occiput a...
Atypical fibroxanthomas are well-circumscribed mesenchymal skin tumours that mainly manifest in the head and neck
Atypical fibroxanthomas are rapidly growing tumours associated with excessive sun exposure, i.e. UV exposure, and usually occur in elderly patients. There is also an a...
Of the five lumbar vertebrae, L5 is considered atypical due to its shape. The remaining lumbar vertebrae are largely typical.
For a basic anatomic description of the structure a generic vertebra, see vertebrae.
Owing to their features, the first, eleventh and twelfth ribs are considered atypical ribs.
Of all ribs, the first is the strongest, broadest and most curved. Ribs eleven and twelve are unique, among other reasons, by not being attached to the sternum.
T1 and T9 - T12 are considered atypical thoracic vertebrae. T1 bears some resemblance to low cervical vertebrae. T9 has no inferior demifacet. T10 often, but not always, shares features with T11 and T12.
For a basic anatomic description of the structure a generic vertebra, see vertebrae.
Autosomal dominant osteopetrosis is the less severe type of osteopetrosis and should be considered and compared with the other subtype autosomal recessive osteopetrosis. The autosomal dominant (AD) type is less severe than its autosomal recessive (AR) mate. Hence, it is also given the name "beni...
Infantile autosomal recessive osteopetrosis is a subtype of osteopetrosis, a bone disease of dysfunctional osteoclasts that results in the overgrowth of bone. It is a more severe form that tends to present earlier. Hence, it is referred to as "infantile" and "malignant" compared to its autosomal...
Avascular necrosis (AVN), or more correctly osteonecrosis, is a generic term referring to the ischaemic death of the constituents of bone. AVN has a wide variety of causes and can affect nearly any bone in the body. Most sites of involvement have an eponym associated with avascular necrosis of t...
Mnemonics for the causes of avascular necrosis (AVN) or more correctly osteonecrosis:
Most common causes:
T: trauma (e.g. femoral neck fracture, hip dislocation, scaphoid fracture, slipped capital femoral epiphysis 2)
A: alcohol abu...
Avascular necrosis of the hip is more common than other sites, presumably due to a combination of precarious blood supply and high loading when standing.
The most common presenting symptom is a pain in the region of affected hip, thigh, groin, and buttock. Although few p...
Aviator astragalus is an antiquated reference to a pattern of isolated fracture/dislocation injury of the talus. Fractures included under this name include compression fractures of the talar neck, fractures of the body, posterior process or fracture dislocation injuries. The talar neck is the mo...
An aviator fracture is a coronal-plane fracture of the neck of the talus resulting from forced dorsiflexion of ankle. It is the second most common talar fracture, after talar dome fractures.
In 20% of cases a fracture of the medial malleolus is also present 1.
These fractures are at risk of av...
Avulsion fracture of the 5th metatarsal styloid, also known as a pseudo-Jones fracture or a dancer fracture, is one of the more common foot avulsion injuries and accounts for over 90% of fractures of the base of the 5th metatarsal.
Despite what should be a simple entity, controversy exists, as ...
Avulsion fractures of the knee are numerous due to the many ligaments and tendons inserting around this joint. They include 1:
anterior cruciate ligament avulsion fracture
posterior cruciate ligament avulsion fracture
avulsion of the medial collateral ligament
origin of MCL avulsion fracture...
Avulsion injuries or fractures occur where the joint capsule, ligament, tendon or muscle attachment site is pulled off from the bone, usually taking a fragment of cortical bone. There are numerous sites at which these occur. Being familiar with them is important as subacute/chronic injuries can ...
The axial skeleton is the central portion of the bony skeleton comprising the head, neck and trunk (80 bones in total). It has many functions including housing and protecting the central nervous system as well as the organs of the chest, abdomen and pelvis. It enables movement and supports the u...
The axilla is a space located between the upper limb and the neck and thorax, which permits the passage of the major neurovascular structures.
The axilla is pyramidal in shape with its apex opening superiorly into the base of the neck between the subclavius muscle, first rib and ...
The axillary nerve is one of five terminal branches of the brachial plexus, supplying motor and sensory branches to the shoulder.
origin: posterior cord of the brachial plexus
course: passes out of axilla through the quadrangular space to the upper arm
major branches: superior later...
The axis is the second cervical vertebra, commonly called C2. It is an atypical cervical vertebra with unique features and important relations that make it easily recognisable. Its most prominent feature is the odontoid process, which is embryologically the body of the atlas (C1) 1,2. It plays a...
Baastrup syndrome (also referred to as kissing spines) results from adjacent spinous processes in the lumbar spine rubbing against each other and resulting in hypertrophy and sclerosis with focal midline pain and tenderness relieved by flexion and aggravated by extension.
Babcock triangle is a relatively radiolucent triangular area seen in the subcapital region of the femoral neck on an anteroposterior radiograph of the hip. In this region, the trabeculae are loosely arranged and surrounded by more radiodense normal bony trabeculae groups. It may be the initial s...
Bacillary angiomatosis is an infective complication in those with the acquired immunodeficiency syndrome (AIDS) 3. Amongst other widespread multi-organ manifestations, the infection causes skin lesions which can be similar to those of Kaposi sarcoma.
Characterised by a non-neoplastic...
The Bado classification is one of the more widely used classifications for Monteggia fracture-dislocations and mainly focuses on the radial component. Four types are recognised and are generally based on the principle that the direction in which the apex of the ulnar fracture points is the same ...
Baker cysts, or popliteal cysts, are fluid-filled distended synovial-lined lesions arising in the popliteal fossa between the medial head of the gastrocnemius and the semimembranosus tendons via a communication with the knee joint. They are usually located at or below the joint line.
A ball and socket ankle joint is a variant affecting the ankle where there is a rounded or spherical configuration to the talar dome with the corresponding concavity of the tibial plafond. The distal fibula may or may not be involved.
The aetiology has been debated with two theories ...
Ball and socket joints are a type of synovial joint where the spheroid articular surface of one bone sits within a cup-like depression of another bone.
The ball and socket configuration allows for movement with 3 degrees of freedom, which is more than any other type of synovial joint...
Bamboo spine is a radiographic feature seen in ankylosing spondylitis that occurs as a result of vertebral body fusion by marginal syndesmophytes. It is often accompanied by fusion of the posterior vertebral elements as well.
A bamboo spine typically involves the thoracolumbar and/or lumbosacr...
A banana fracture refers to a complete, horizontally oriented pathological fracture seen in deformed bones affected by Paget disease. This term is often used to describe incremental fractures that occur in Paget disease as well, which represent a type of insufficiency fracture.
The former of th...
Bankart lesions are injuries specifically at the anteroinferior aspect of the glenoid labral complex, and represent a common complication of anterior shoulder dislocation. They are frequently seen in association with a Hill-Sachs lesion.
Strictly speaking, a "Bankart lesion" refer...
Bannayan–Riley–Ruvalcaba syndrome (BRRS or BRR syndrome) is a very rare autosomal dominant hamartomatous disorder caused by a mutation in the PTEN gene. It is considered in the family of hamartomatous polyposis syndrome.
There are no formal diagnostic criteria for this disease, but characterist...
Bannayan-Zonana syndrome is a rare hamartomatous disorder.
Inheritance is by autosomal dominant transmission with few reported sporadic cases. Male predominance is reported. 1
Bannayan-Zonana syndrome characterised by :
Barton fractures are fractures of the distal radius. It is also sometimes termed the dorsal type Barton fracture to distinguish it from the volar type or reverse Barton fracture.
Barton fractures extend through the dorsal aspect to the articular surface but not to the volar aspect. Therefore, i...
The base of the skull (or skull base) forms the floor of the cranial cavity and separates the brain from the structures of the neck and face.
The base of the skull is a bony diaphragm composed of a number of bones - from anterior to posterior:
Baumann angle, also known as the humeral-capitellar angle, is used for the evaluation of the displacement of paediatric supracondylar humeral fractures. It is measured on a frontal radiograph, with elbow in extension.
This angle is formed by the humeral axis and a straight line through the ep...
Baxter neuropathy is a nerve entrapment syndrome resulting from the compression of the inferior calcaneal nerve (Baxter nerve).
heel pain with maximal tenderness over the course of the inferior calcaneal nerve (on the plantar medial aspect of the foot and anterior to the ...
Bayonet deformity is a term used to describe the shape of the wrist in certain conditions:
hereditary multiple exostosis with pseudo-Madelung deformity
retarded bone growth of the distal ulna with outward bowing of the radius with distal radioulnar joint subluxation
Becker muscular dystrophy (BMD) is a dystrophinopathy that is considered to be a milder form of Duchenne muscular dystrophy.
It may be present in 3 to 6 per 100,000 male births. The condition is extremely rare in females due to its inheritance pattern, as discussed below.
Benign fibrous histiocytoma is closely related to fibroxanthoma of bone, is a rare lesion usually occurring in the skin where it is known as dermatofibroma.
Typically presents with pain, and most often in the third decade.
Only a few case reports have been pub...
Benign lytic bone lesions encompass a wide variety of entities. A useful starting point is the FEGNOMASHIC mnemonic.
This article is a stub, which means it needs more content. You can contribute to Radiopaedia too. Just register and click edit... every little bit helps.
A mnemonic to remember five benign lytic lesions that rarely occur in patients over 30 years of age.
S - simple bone cyst
C - chondroblastoma
A - aneurysmal bone cyst
N - non-ossifying fibroma
E - eosinophilic granuloma
In a patient older than 30 years of age th...
Benign notochordal cell tumours (BNCT) are vertebral lesions that are usually asymptomatic and discovered incidentally on imaging of the head or spine. As this is a poorly-recognised entity, it can often be confused with aggressive vertebral lesions, such as a chordoma, when it is seen on imagin...
A Bennett fracture is a fracture of the base of the thumb resulting from forced abduction of the first metacarpal. It is defined as an intra-articular two-part fracture of the base of the first metacarpal bone.
two piece fracture of the base of the thumb...
Bennett lesions of the shoulder, also called thrower's exostosis refers to the mineralisation of the posterior band of the inferior glenohumeral ligament.
The abnormality is more prevalent in overhead throwing athletes.
It is associated with posterior labral tears,...
Bent bone dysplasias are a class of dysplasia included in a 2010 classification of genetic skeletal disorders 1.
kyphomelic dysplasias, a diverse class, including
congenital bowing of the long bones
cartilage-hair hypoplasia (CHH; metaphyseal d...
Berndt and Harty classification is used for osteochondral lesions of the talus.
stage I: subchondral bone compression (marrow edema)
stage IIa: subchondral cyst
stage IIb: incomplete separation of fragment
stage III: complete separation but no displacement
Bernese osteotomy, also known also Ganz osteotomy, is an orthopaedic procedure involving osteotomy surrounding the acetabulum and subsequent angulation to improve coverage of the femoral head by the acetabulum. It is performed in the context of hip dysplasia. There is an osteotomy through the su...
Bertolotti syndrome refers to the association between lumbosacral transitional vertebrae (LSTV) and low back pain, and can be an important cause in young patients.
It is considered controversial and has been both supported and disputed since Mario Bertolotti first described it in 1917. Some st...
The beta angle is a measurement used in the ultrasonographic assessment of developmental dysplasia of the hip (DDH).
It is defined as the angle formed between the vertical cortex of the ilium and the triangular labral fibrocartilage (echogenic triangle) and thus reflects the femoral head cartil...
The biceps brachii muscle (also known simply as biceps) is a two-headed muscle in the anterior compartment of the arm that flexes at the elbow and supinates the forearm.
short head: coracoid process of the scapula
long head: supraglenoid tubercle of the scapula
A biceps brachii rupture can occur at either superior or inferior end but most commonly involves the long head at its proximal attachment to superior glenoid labrum.
The biceps tendon has a fibrous covering (the lacertus fibrosus) that can clinically feel similar to an intact tendon even though...
Biceps chondromalacia is an attritional lesion of the humeral head caused by repeated abrasion by the intra-articular segment of the long head of biceps tendon.
The long head of biceps brachii arises from the supraglenoid tubercle of the glenoid fossa and has an intra- and extra-arti...
The biceps femoris is one of the large muscles in the posterior compartment of the thigh and a component of the hamstrings. It has a long and a short head, each with different functions and innervation.
long head: medial facet of the ischial tuberosity
short head: lateral line...
Biceps pulley refers to a complex capsuloligamentous structure which provides stability and hold the long head of biceps tendon within the bicipital groove. It comprises of the coracohumeral ligament, superior glenohumeral ligament, and distal attachment of the subscapularis tendon.
Biceps pulley injuries can be challenging and difficult to diagnose. They can be missed during open and arthroscopic examination, and therefore have sometimes been referred to as a “hidden lesions”.
Anatomy of Biceps Pulley:
The biceps pulley or “sling” is a complex capsuloligamentous structur...
The bicipitoradial bursa is located between the distal biceps brachii tendon and the tuberosity of the radius. The bursa partially or completely wraps around the biceps tendon. It ensures frictionless motion between the biceps tendon and the proximal radius during pronation and supination of the...
Bicipitoradial bursitis refers to inflammation of the bicipitoradial bursa.
The bicipitoradial bursa surrounds the biceps tendon in supination. In pronation, the radial tuberosity rotates posteriorly, which compresses the bicipitoradial bursa between the biceps tendon and the radial cortex whi...
The median nerve may divide into two nerve bundles in
the distal forearm and appear as a bifid median nerve in the carpal tunnel. It has an incidence of ~3%.
The median nerve usually divides into two or three branches after exiting the distal edge of the transverse carpal ligament that covers...
Bifid or forked ribs are uncommon. They are thought to occur in ~0.2% of the population and there may be a female as well as right-sided predilection 2.
Usually asymptomatic, they may cause musculoskeletal pain or intercostal nerve entrapment. A bifid first rib is an unco...
The bifurcate ligament arises from the anterior process of the calcaneus as a single band and divides into calcaneocuboid (lateral) and calcaneonavicular (medial) parts forming a Y-shape.
A bilateral facet dislocation is an unstable flexion distraction type of dislocation of the cervical spine, often a result of buckling force. Occasionally, the bilateral facet dislocation has been named a 'doubly-locked' vertebral injury giving the impression of stability. However, due to comple...
Bilateral thinning of the parietal bones, also known as biparietal osteodystrophy, is an uncommon, slowly progressive acquired disease of middle-aged people with slight female predilection. It is typically an incidental finding.
The aetiology is unknown but is thought to be an age-r...
A bipartite medial cuneiform is an anatomical variant where there are two ossification centres involving the medial cuneiform. In many cases the overall shape of the medial cuneiform is conserved, although the size of the two combined bones is larger than that of a normal medial cuneiform.
A bipartite patella (two-part patella) is a patella with an unfused accessory ossification center at the superolateral aspect.
The superolateral accessory ossification center of the patella is usually present by 12 years of age and may persist into adult life. Prevalence of a bipa...
A bipartite scaphoid is a rare example of a divided carpus. There is controversy whether this condition is congenital (i.e. normal variant) or post-traumatic. Bipartite scaphoids may be unilateral or bilateral.
Diagnostic criteria have been proposed 3:
no history of traumatic injury
Birth fractures of the clavicle occur in 0.5-1% of vaginal deliveries and are the most frequent birth-related fracture. They are most commonly seen following normal, uncomplicated births but there is recognised increased incidence with high birth weight babies, forceps delivery and shoulder dyst...
Birth trauma relates to those conditions caused by both physical/mechanical and hypoxic injuries.
Birth trauma occurs in ~5 per 1000 births 2.