Articles

Articles are a collaborative effort to provide a single canonical page on all topics relevant to the practice of radiology. As such, articles are written and edited by countless contributing members over a period of time. A global group of dedicated editors oversee accuracy, consulting with expert advisers, and constantly reviewing additions.

2,616 results found
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Angiolipoma

Angiolipomas (also sometimes known as haemangiolipomas, vascular lipomas, and fibromyolipomas) are rare soft tissue tumours composed of mature adipocytes and vessels. They can occur essentially anywhere and can be subclassified into infiltrating and non-infiltrating variants 1.  Please refer to...
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Angiosarcoma (bone)

Angiosarcoma of bone is a malignant vascular tumour of bone. These are rare and account for less than 1% of malignant bone tumours. The majority of these tumours arising in bone are primary; however, a tiny percentage is either radiation-induced or associated with bone infarction Epidemiology ...
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Angle of the longitudinal arch (foot)

The angle of the longitudinal arch is one of the angles drawn on the weightbearing lateral foot radiograph. The angle is formed between the calcaneal inclination axis and a line drawn along the inferior edge of the 5th metatarsal. The normal angle is 150-170°. In pes cavus, as the height of th...
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Anisotropy

Anisotropy is an artefact encountered in ultrasound, notably in muscles and tendons during a musculoskeletal ultrasound. In musculoskeletal applications, the artefact may prompt an incorrect diagnosis of tendinosis or tendon tear. When the ultrasound beam is incident on a fibrillar structure as...
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Ankle (AP view)

Ankle AP view is part of a three view series of the distal tibia, distal fibula, proximal talus and proximal metatarsals. Patient position the patient may be supine or sitting upright with their leg straighten on the table the foot is in dorsiflexion the toes will be pointing directly toward...
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Ankle (lateral view)

Ankle lateral view is part of a three view ankle series; this projection is used to assess the distal tibia and fibula, talus, navicular, cuboid, the base of the 5th metatarsal and calcaneus. Patient position patient is in a lateral recumbent position on the table the lateral aspect of the kn...
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Ankle (mortise view)

Ankle AP mortise view is part of a three view series of the distal tibia, distal fibula, talus and proximal metatarsals. It is the most pertinent projection for assessing the articulation of the tibial plafond and two malleoli with the talar dome, otherwise known as the mortise joint of the ankl...
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Ankle fractures

Ankle fractures account for ~10% of fractures encountered in trauma, preceded only in incidence by proximal femoral fractures in the lower limb. They have a bimodal presentation, involving young males and older females. Ankle injuries play a major part in post multitrauma functional impairment t...
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Ankle joint

The ankle joint forms the articulation between the foot and the leg. It is a primary hinge synovial joint lined with hyaline cartilage. Gross anatomy The ankle joint is comprised of the tibia, fibula, talus, and calcaneus as well as the supporting ligaments, muscles and neurovascular bundles. ...
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Ankle radiograph (checklist)

The ankle radiograph checklist is just one of the many pathology checklists that can be used when reporting to ensure that you always actively exclude pathology that is commonly missed; this is particularly helpful in the examination setting, e.g. the FRCR 2B rapid-reporting. Radiograph The ma...
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Ankle series

The ankle series is comprised of an anteroposterior (AP), mortise and lateral radiograph. The series is often used in emergency departments to evaluate the distal tibia, distal fibula, and the talus; forming the ankle joint. See approach to an ankle series. Indications Ankle radiographs are p...
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Ankle teardrop sign

Ankle teardrop sign is one of the radiological signs of an ankle joint effusion. It represents the presence of fluid in the inferior part of the anterior compartment of ankle. Pathology Aetiology trauma gout rheumatoid arthritis synovitis infectious arthritis Radiographic appearance Pla...
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Ankle x-ray (summary)

An ankle x-ray, also known as ankle series or ankle radiograph, is a set of two x-rays of the ankle joint. It is performed to look for evidence of injury (or pathology) affecting the ankle, often after trauma. Reference article This is a summary article. For more information, you can read a mo...
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Ankylosing spondylitis

Ankylosing spondylitis (less commonly known as Bechterew disease and Marie Strümpell disease) is a seronegative spondyloarthropathy, which, as the name suggests, results in fusion (ankylosis) of the spine and sacroiliac (SI) joints, although involvement is also seen in large and small joints. E...
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Ankylosing spondylitis: thoracic manifestations

Thoracic manifestations of ankylosing spondylitis can be varied. For a general discussion of the condition refer to the parent article on ankylosing spondylitis. It can affect the tracheobronchial tree and the lung parenchyma, and the disease spectrum includes: upper lobe fibrocystic changes ...
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Annular fissure

Annular fissures are a degenerative deficiency of one or more layers that make up the annulus fibrosus of the intervertebral disc.  Terminology Many authors prefer the term annular fissure over annular tear, as the latter seems to imply acute injury 1,2. In the setting of severe trauma with di...
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Annulus fibrosus

The annulus fibrosus surrounds the nucleus polposus and together they form the intervertebral disc. Gross anatomy The annulus comprises 15 to 20 collagenous (type I) laminae which run obliquely from the edge of one vertebra down to the edge of the vertebra below. The direction of the fibres al...
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Anteater nose sign (foot)

The anteater nose sign refers to an anterior tubular elongation of the superior calcaneus which approaches or overlaps the navicular on a lateral radiograph of the foot. This fancifully resembles the nose of an anteater and is indicative of calcaneonavicular coalition 1,2.  History and etymolog...
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Anterior abdominal wall

The anterior abdominal wall forms the anterior limit of the abdominal viscera and is defined superiorly by the xiphoid process of the sternum and costal cartilages and inferiorly by the iliac crest and pubic bones of the pelvis. Gross anatomy The anterior abdominal wall has seven layers (from ...
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Anterior angulation of the coccyx

Anterior angulation of the coccyx may be a normal variant but poses a diagnostic challenge for those considering coccygeal trauma. Classification Four types of coccyx have been described: type I: the coccyx is curved slightly forward, with its apex pointing caudally (~70%) type II: the coccy...
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Anterior ankle impingement syndrome

Anterior ankle impingement (AAI) syndrome is the result of chronic repetitive trauma with impingement of the anterior tibia against the talus. Clinical presentation Clinical features of anterior ankle impingement syndrome include painful and limited dorsiflexion and anterior joint line swellin...
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Anterior ankle tendons (mnemonic)

A mnemonic that refers to the order of the ankle tendons that pass under the flexor retinaculum of the ankle running from medial to lateral is: Tom Hates Dick Mnemonic T: tibialis anterior H: extensor hallucis longus D: extensor digitorum longus History and etymology The phrase Tom, Dick...
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Anterior compartment of the arm

The anterior compartment of the arm is one of the two compartments of the arm. A sheath of deep fascia surrounds the arm, the brachial fascia. Two intermuscular septa (medial and lateral) extend from it to attach to the humerus at the medial condylar ridge and lateral supracondylar ridge, respe...
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Anterior compartment of the forearm

The forearm is divided into the anterior compartment and the posterior compartment by the deep fascia, lateral intermuscular septum and the interosseous membrane between the ulna and radius.  Muscles The eight muscles located in the anterior compartment of the forearm can be divided into three...
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Anterior compartment of the leg

The anterior compartment of the leg is one of the four compartments in the leg between the knee and foot. Muscles within this compartment primarily produce ankle dorsiflexion and toe extension. The leg is separated into anterior, lateral, superficial posterior and deep posterior compartments by...
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Anterior compartment of the thigh

The anterior compartment of the thigh is one of the three compartments in the thigh. Muscles within this compartment primarily produce hip flexion and knee extension. The thigh is separated into anterior, posterior and medial (adductor) compartments by intermuscular septa and surrounded by the ...
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Anterior cruciate ligament

Anterior cruciate ligament (ACL) is one of the two cruciate ligaments that stabilise the knee joint.  Gross anatomy The ACL arises from the anteromedial aspect of the intercondylar area on the tibial plateau and passes upwards and backwards to attach to the posteromedial aspect of the lateral ...
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Anterior cruciate ligament avulsion fracture

Anterior cruciate ligament (ACL) avulsion fractures or tibial eminence avulsion fractures are a type of avulsion fracture of the knee. This typically involves separation of the tibial attachment of the ACL to variable degrees. Separation at the femoral attachment is rare 5. Epidemiology It is ...
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Anterior cruciate ligament ganglion cyst

Anterior cruciate ligament (ACL) ganglion cysts, commonly referred to simply as ACL cysts, along with ganglion cysts arising from the alar folds that cover the infrapatellar fat pad, make up the vast majority of intra-articular ganglion cysts of the knee. Epidemiology Anterior cruciate ligamen...
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Anterior cruciate ligament mucoid degeneration

Anterior cruciate ligament (ACL) mucoid degeneration, along with tears and anterior cruciate ligament ganglion cysts, is a relatively common cause of increased signal within the anterior cruciate ligament (ACL). The appearance can mimic acute or chronic interstitial partial tears of the ACL. Ho...
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Anterior cruciate ligament tear

Anterior cruciate ligament (ACL) tears are the most common knee ligament injury encountered in radiology practice. Pathology The ACL is the most commonly disrupted ligament of the knee, especially in athletes who participate in sports that involve rapid starting, stopping, and pivoting (e.g. s...
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Anterior dislocation of the hip

Anterior hip dislocation is much less common than a posterior hip dislocation. It constitutes for only 5-18% of all hip dislocations. Pathology While the posterior dislocation is often associated with fractures, the anterior dislocation is mostly an isolated injury 1. Subtypes It can be clas...
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Anterior glenolabral injuries

Anterior glenolabral injuries are common in the setting of anterior shoulder dislocation and comprise a number of closely related entities. Bankart lesion bony Bankart lesion anterior labroligamentous periosteal sleeve avulsion (ALPSA) Perthes lesion glenolabral articular disruption (GLAD) ...
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Anterior hip pain

Causes of anterior hip pain include: osteoarthritis synovitis including pigmented villonodular synovitis (PVNS) synovial osteochondromatosis inflammatory arthropathy (e.g. rheumatoid arthritis) iliopsoas bursitis ganglion cyst synovial cyst muscle tear malignancy inguinal adenopathy ...
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Anterior humeral circumflex artery

The anterior humeral circumflex artery is a vessel arising from the axillary artery at the proximal part of the arm. It is smaller in size relative to the posterior humeral circumflex artery.  Summary origin: branch of the axillary artery at the proximal part of the arm location: proximal arm...
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Anterior humeral line

The anterior humeral line is key to demonstrating normal elbow alignment and should be used whenever reading a paediatric elbow radiograph to exclude a subtle supracondylar fracture. The rule A line drawn down the anterior surface of the humerus should intersect the middle third of the capitel...
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Anterior inferior iliac spine

The anterior inferior iliac spine (AIIS) is bony prominence on the anterior border of the ilium forming the superior border of the acetabulum. Attachments include the Iliacus, origin of straight head of the rectus femoris, and also the the proximal ileofemoral ligament (Y-ligament or ligament o...
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Anterior inferior iliac spine avulsion injury

Anterior inferior iliac spine (AIIS) avulsion injuries are one of the six main types of pelvic apophyseal avulsion fractures.  Epidemiology As with many pelvic avulsion injuries, they most often occur in adolescents (mostly between the ages 14-17). There is a slight male predilection and they ...
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Anterior interosseous nerve

The anterior interosseous nerve also known as the volar interosseous nerve arises from the median nerve in the forearm, and supplies the flexor pollicis longus, pronator quadratus and the lateral portion of flexor digitorum profundus. Gross anatomy Origin The anterior interosseous nerve conti...
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Anterior interosseous nerve syndrome

Anterior interosseous nerve syndrome (AINS), also known as Kiloh-Nevin syndrome, is one of three common median nerve entrapment syndromes; the other two being pronator teres syndrome and the far more common carpal tunnel syndrome. Epidemiology AINS is a rare entrapment syndrome, with comparati...
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Anterior knee fat pads

There are three anterior knee fat pads 1: infrapatellar fat pad (of Hoffa) fills the space between the patella ligament and the anterior intercondylar area of the tibia 2 posterior suprapatellar (prefemoral or supratrochlear) fat pad anterior suprapatellar (quadriceps) fat pad fills the spa...
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Anterior knee pain

Anterior knee pain is common with a variety of causes including: patella fracture osteoarthritis inflammatory and depositional arthritis bursitis around the knee patellofemoral maltracking excessive lateral pressure syndrome (ELPS) patellar cartilage defect patellofemoral chondromalacia ...
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Anterior labroligamentous periosteal sleeve avulsion lesion

An anterior labroligamentous periosteal sleeve avulsion (ALPSA) lesion is similar to a Bankart lesion, in that it too is usually due to anterior shoulder dislocation and involves the anterior inferior labrum.  Unlike the Bankart lesion in which the labrum and glenoid periosteum is avulsed from ...
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Anterior lateral malleolar artery

The anterior lateral malleolar artery is the counterpart to the anterior medial malleolar artery, supplies the lateral aspect of the ankle.  Gross anatomy Origin and course branch of anterior tibial artery runs posterior to the tendons of extensor digitorum longus and fibularis tertius to th...
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Anterior longitudinal ligament

The anterior longitudinal ligament (ALL) arises from the anteroinferior basilar portion of occipital bone, traverses the entire length of the spine, and ends on the anteriosuperior portion of the sacrum. The ALL runs along the anterior surface of the vertebral bodies (firmly united to the perio...
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Anterior medial malleolar artery

Anterior medial malleolar artery is the counterpart to the anterior lateral malleolar artery, and supplies the medial aspect of the ankle. Gross anatomy Origin and course branch of anterior tibial artery arises approximately 5 cm proximal to the ankle passes posterior to the tendons of exte...
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Anterior shoulder capsular insertion

The anterior capsular insertion, unlike the posterior aspect of the shoulder joint capsule which has a constant scapular attachment along the margins of the glenoid labrum, inserts a variable distance from the labrum. The capsular insertions are classified as follows: type I: at or very near t...
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Anterior shoulder dislocation

Anterior shoulder dislocation is by far the commonest type of dislocation and usually results from forced abduction, external rotation and extension 1.  Epidemiology Broadly speaking, anterior shoulder dislocations occur in a bimodal age distribution. The first, and by far the more prevalent a...
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Anterior subluxation of cervical spine

Anterior subluxation of cervical spine (also known as hyperflexion sprain) is a ligamentous injury to the cervical spine. Clinical presentation Patient presents with neck pain. There may be symptoms due to spinal cord oedema. Pathology It results from ligamentous injury, however, there may b...
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Anterior superior iliac spine

The anterior superior iliac spine is an important bony surface landmark and is the prominence is the most anterior part of the ilium. It can be palpated at the lateral end of the inguinal fold. Attachments include the inguinal ligament, tensor fasciae latae and sartorius. Clinically, as an easi...
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Anterior superior iliac spine avulsion injury

Anterior superior iliac spine (ASIS) avulsion injuries typically occur in athletes during forceful muscular contraction. ASIS is the site of attachment for sartorius and tensor fascia latae muscles.  Pathology ASIS avulsion, like other pelvic avulsion injuries, is a stable fracture. Treatment...
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Anterior talofibular ligament

The anterior talofibular ligament (ATFL) is part of the lateral collateral ligament complex of the ankle. Its role is to stabilise the talus. It is also the weakest of the lateral collateral ankle ligaments.  Gross anatomy The ATFL is an intra-capsular flat two-banded ligament that arises from...
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Anterior talofibular ligament injury

Anterior talofibular ligament (ATFL) injury is the most common of the ligament injuries that can occur as part of the lateral ligament complex injuries 2. The injuries can comprise either soft tissue tears, avulsion fractures or both. Pathology ATFL injuries typically occur with an inversion i...
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Anterior tibial translocation sign

The anterior tibial translocation sign or anterior drawer sign (a.k.a. anterior translation of tibia) is seen in cases of complete rupture of the anterior cruciate ligament, and refers to anterior translocation (anterior tibial subluxation) of the tibia relative to the femur of more than 7 mm 1. 
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Anterior tibial vein

The anterior tibial veins, continuations of the venae comitantes of the dorsalis pedis artery, leave the anterior compartment between the tibia and fibula and pass through the proximal end of the interosseous membrane. They unite with the posterior tibial veins to form the popliteal vein at the ...
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Anterolateral ligament of the knee

The anterolateral ligament of the knee (ALL) is a ligament that is thought to aid with rotational stability of the knee joint. Some think that its presence (or reconstruction) may result in better outcomes from ACL stabilisation surgery 2. The ligament has also been implied in Segond fractures 3...
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Anterolisthesis

The term anterolisthesis refers to anterior displacement (forward slip) of vertebral body relative to one below.
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Antibiotic beads

Implanted antibiotic beads are a form of microbiological treatment inserted during orthopaedic procedures to aid with the treatment of chronic infection. They are also used as a local treatment for osteomyelitis. The beads are radiopaque, thus lending themselves to visualisation on all imaging ...
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AO classification of proximal humeral fractures

The AO classification of proximal humeral fractures, along with the Neer classification, is one of the most frequently used systems for classifying proximal humeral fractures.  The AO classification divides proximal humeral fractures into three groups, A, B and C, each with subgroups, and place...
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Apert syndrome

Apert syndrome (also known as type I acrocephalosyndactyly) is a syndrome that is predominantly characterised by skull and limb malformations. Epidemiology The estimated incidence is at 1:65-80,000 pregnancies. Pathology Thought to occur from a defect on the fibroblast growth factor receptor...
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Apophyseal avulsion fractures of the pelvis and hip

Apophyseal avulsion fractures of the pelvis and hip are relatively common among physically active adolescents and young adults. Epidemiology Pelvic and hip apophyseal injuries typically occur in the 14 to 25 year age range. Kicking sports, such as soccer, and gymnastics are frequently to blame...
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Apophysis

The apophysis (pl: apophyses) is a normal bony outgrowth that arises from a separate ossification centre and fuses with the bone in course of time. The apophysis is a site of tendon or ligament attachment, as compared to the epiphysis which contributes to a joint. When unfused, they can easily ...
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Apophysis of the proximal 5th metatarsal

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...
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Appendicular films (early clinical)

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...
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Appendicular skeleton

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 ...
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Apple core sign (femur)

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 ...
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Arcade of Frohse

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 ...
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Arcuate foramen

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 ...
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Arcuate ligament

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...
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Arcuate line

The arcuate line is situated 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 transvers...
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Arcuate sign (knee)

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...
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Arm

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. See humer...
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Arnold-Hilgartner classification of haemophilic arthropathy

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...
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Arrested pneumatisation of the skull base

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...
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Arthrogryposis

Arthrogryposis (multiplex congenita) is a clinical or imaging descriptor that denotes congenital non-progressive joint contractures involving two or more body regions.  Epidemiology It is thought to occur in approximately 1:3000-10,000 live births 6,8. Pathology It can result from a number o...
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Articular cartilage calcification (mnemonic)

An easy to remember mnemonic for the causes of articular cartilage calcification is: HOGWASH Mnemonic H: hyperparathyroidism O: ochronosis G: gout W: Wilson disease A: arthritis S: pseudogout H: haemochromatosis
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Articularis cubiti

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
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Articularis genu muscle

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. Summary origin: anterior distal femoral shaft insertion: knee joi...
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Aseptic loosening of hip joint replacements

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. Pathology Aseptic loosening can occur as a result of inadequate initial fixation, mechanical lo...
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ASIA impairment scale for spinal injury

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...
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Asphyxiating thoracic dysplasia

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...
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Atelosteogenesis

Atelosteogenesis (AO) refers to a group of lethal skeletal dysplasias. Pathology Sub types atelosteogenesis type I atelosteogenesis type II atelosteogenesis type III 4
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Athletic pubalgia

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. ...
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Atlanto-axial subluxation

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. Pathology Aetiology congenital os odontoideum Down syndrome (20%) Morqui...
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Atlanto-occipital assimilation

Atlanto-occipital assimilation is the fusion of the atlas (C1) to the occiput and is one of the transitional vertebrae.  Epidemiology Atlanto-occipital assimilation occurs in ~0.5% (range 0.25-1%) of the population 2-4.  Clinical presentation Atlanto-occipital is typically asymptomatic but s...
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Atlanto-occipital dissociation injuries

Atlanto-occipital dissociation (AOD) injuries are severe and include both atlanto-occipital dislocations and atlanto-occipital subluxations. Pathology The tectorial membrane and alar ligaments provide the most stability to the atlanto-occipital joint, and injury to these ligaments results in i...
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Atlas (C1)

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...
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Atypical cervical vertebrae

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...
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Atypical lumbar vertebrae

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.
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Atypical ribs

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.
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Atypical thoracic vertebrae

T1 and T9 to T12 are considered atypical 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.
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Autosomal dominant osteopetrosis

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 "ben...
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Autosomal recessive osteopetrosis

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...

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