The external oblique muscle (EOM) is one of the muscles that forms the anterior abdominal wall. Its free inferior border forms the inguinal ligament, and its aponeurotic part contributes to the anterior wall of the inguinal canal.
origin: outer surface of the shaft of the lower 8 ribs...
Extraskeletal chondrosarcomas make up only 2% of soft-tissue sarcomas and only 1% of all chondrosarcomas.
They tend to be of higher grade than run-of-the-mill conventional intramedullary chondrosarcomas, with the majority being of the myxoid (most common) or mesenchymal varieties 3...
Extraskeletal Ewing sarcoma (EES) is included in the Ewing sarcoma family of tumors (ESFT) along with Ewing sarcoma of bone, primitive neuroectodermal tumor (PNET), peripheral neuroepithelioma, and thoracopulmonary PNET (Askin tumour). When compared with Ewing sarcoma of bone, extraskeletal Ewin...
extraskeletal myxoid chondrosarcoma
pigmented villonodular synovitis (PVNS)
Extraskeletal osteosarcoma (ESOS) is a rare mesenchymal malignant tumour that occurs in the retroperitoneum and soft tissue of extremities without any attachment to bone.
ESOS in contrast to other subtypes of osteosarcoma occurs infrequently in individuals under 40 years of age, m...
The fabella is an accessory ossicle typically found in the lateral head of the gastrocnemius. It occurs in ~20% (range 10-30%) of the population 1.
The fabella can also be fibrocartilaginous in nature and is occasionally found in the medial head of the gastrocnemius. The fabella articulates wi...
Facet dislocation refers to anterior displacement of one vertebral body on another. Without a fracture, the only way anterior displacement can occur is by dislocation of the facets.
Facet dislocation can occur to varying degrees:
The injury usua...
The facet (or apophyseal or zygapophyseal) joints are the articulations of the posterior arch of the vertebrae and form part of the posterior column.
They are synovial-lined joints that have a fibrous capsule and connect the articular facets of the vertebrae. The superior facet ...
Facet joint capsules are the fibrous capsule that surround the vertebral facet or zygapophyseal joints. They are particularly thin and loose, attached to the margins of articular facets on adjoining articular processes. The capsules merge medially with the ligamentum flavum.
In the cervical re...
The facial muscles enable facial expression and serve as sphincters and dilators of the orifices of the face. These muscles differ from those of other regions in the body as there is no fascia deep to the skin of the face; many of the facial muscles insert directly into the skin 1.
Failed back syndrome refers to persistent leg and/or lumbar back pain after a surgical procedure. The pathophysiology of this syndrome is complex, as often the operation was technically successful.
Other names for failed back syndrome include failed back surgery syndrome, post-lam...
The fallen fragment sign refers to the presence of a bone fracture fragment resting dependently in a cystic bone lesion. This finding is said to be pathognomonic for a simple (unicameral) bone cyst following a pathological fracture. Although it has occasionally been reported with other cystic le...
Fall onto an outstretched hand (FOOSH) is a common mechanism for wrist-forearm fractures, in certain cases with involvement of elbow structures, particularly in children.
Some injuries that result from such a fall include:
Familial multiple lipomatosis (FML) is a hereditary syndrome of multiple encapsulated lipomas which are found on the trunk and extremities, with relative sparing of the head and shoulders.
It is clinically distinct from the similarly named multiple symmetric lipomatosis with which it is freque...
Fanconi anaemia (FA) is a rare disorder characterised by progressive bone marrow failure, various congenital abnormalities, and predisposition to malignancies (often acute myeloid leukaemia). It is considered the commonest type of inherited marrow failure syndrome 7.
The fascial tail sign is the linear extension along the fascia/muscular aponeurosis from a deeper tumour.
It appears as a tail and is best appreciated on MRI, classically seen in desmoid tumours as T2 hypointense bands that progressively enhance particularly on delayed ph...
Fascicular sign is a finding on T2-weighted MRI images that suggests a lesion of neurogenic origin. It is characterised by multiple small ring-like structures with peripheral hyperintensity representing the fascicular bundles within the nerves.
It is found in various neurogenic tumours, includi...
Fatco syndrome is a syndrome consisting of
tibial campomelia and
It is a syndrome of unknown genetic basis and inheritance with variable expressivity and penetrance.
Fuhrmann syndrome and Al-Awadi syndrome are said to be similar to FA...
Fatigue fractures are a type of stress fracture due to abnormal stresses on normal bone. They should not be confused with an insufficiency fracture, which occurs due to normal stresses on abnormal bone. Plain films typically demonstrate a linear sclerotic region. MRI is the most sensitive and sp...
In fat-pad impingement syndromes the aetiologies are different for each knee fat pad.
In anterior suprapatellar fat pad impingment syndrome the cause is usually due to either a developmental cause related to the anatomy of the extensor mechanism, or may be related to abnormal mechanics. In this...
The fat redistribution syndrome (or HIV lipodystrophy syndrome) is seen in a number of AIDS patients on HAART. It is characterised by typical changes in body fat distribution.
Features include :
hypertrophy in the neck fat pad (buffalo hump)
increased fat in the abdominal region (protease pau...
Faulty fetal packing, also known as congenital vault depression, is a congenital concave depression of the skull in a newborn.
Occurs in 1 in 10,000 births 1.
This appearance is due to external compression on the skull from 1,2:
fetal limb or twin
The FBI sign is an acronym referring to the components that form a lipohaemarthrosis. It stands for:
FCD may refer to:
focal cortical dysplasia (of the brain)
fibrous cortical defect (of the bone)
The radiographic features of a Charcot joint can be remembered by using the following mnemonic:
6 Ds of Charcot joint
increased Density (subchondral sclerosis)
Debris (intra-articular loose bodies)
The causes of Charcot arthrop...
Feingold syndrome is characterised by the combination of:
alimentary tract atresias especially oesophageal atresia
Felty syndrome comprises of the combination of:
rheumatoid arthritis (RA)
It is thought to occur in ~ 1% of patients with rheumatoid arthritis 2.
rheumatoid factor (RF): Over 95% of FS patients are positive 5
Femoral anteversion refers to the orientation of the femoral neck in relation to the femoral condyles at the level of the knee. In most cases, the femoral neck is oriented anteriorly as compared to the femoral condyles. In the case of posterior orientation, the term femoral retroversion is also ...
The femoral canal, or the medial compartment of the femoral sheath, is the inverted cone-shaped fascial space medial to the femoral vein within the upper femoral triangle. It is only 1-2 cm long and opens superiorly as the femoral ring. It serves two purposes:
allows the femoral vein to expand ...
Femoral hernias are a type of groin herniation and comprise of a protrusion of a peritoneal sac through the femoral ring into the femoral canal, posterior and inferior to the inguinal ligament. The sac may contain preperitoneal fat, omentum, small bowel, or other structures.
Neck of femur fractures (NOF) are common injuries sustained by older patients who are both more likely to have unsteadiness of gait and reduced bone mineral density, predisposing to fracture. Elderly osteoporotic women are at greatest risk.
It is anticipated that the total number ...
The femoral nerve is a large nerve arising from the lumbar plexus and one of two major nerves supplying the lower limb.
It arises from posterior divisions of L2-L4 roots of the lumbar plexus.
emerges from the lateral border of the psoas muscle to descend between ...
Femoral nerve neuropathy occurs when the femoral nerve is compressed as it passes under the inguinal ligament, anterior to iliopsoas.
Causes include surgery (hysterectomy, pelvic, hip, femoral artery catheterization, arterial bypass).
Mass effect from iliacus or iliopsoas may be visualised and...
The femoral ring is the superior opening of the femoral canal. Its boundaries are:
medial: lacunar ligament
anterior: medial part of the inguinal ligament
lateral: femoral vein within the intermediate compartment of the femoral sheath
posterior: pectineal ligament overlying the pectineus and...
The femoral sheath is the funnel-shaped fascial space that extends from the abdomen, inferior to the inguinal ligament, into the femoral triangle. It has variable length and terminates by blending in with the adventitia of the femoral vessels. It is formed from the transversalis and psoas fascia...
Femoral torsion analysis is used to assess the alignment of a femur post surgery. If one side has been operated on it can be compared to the non-operated side.
Superimpose axial images of:
the neck of femurs
Draw a line from the centre of the femoral h...
The femoral triangle is found in the anterior upper thigh.
The major boundaries can be recalled with the mnemonic SAIL 1,2:
lateral border: medial border of sartorius
medial border: medial border of adductor longus
superior border: inguinal ligament
A mnemonic for the boundaries of the femoral triangle is:
This should be easy to remember because the femoral triangle is shaped like a sail.
A: adductor longus
IL: inguinal ligament
Mnemonics to recall the order of the femoral vessels and nerve as they emerge from beneath the inguinal ligament into the femoral triangle are:
From lateral to medial:
N: femoral nerve
A: femoral artery
V: femoral vein
Femoro-acetabular impingement (FAI) refers to a clinical syndrome of painful, limited hip motion resulting from certain types of underlying morphological abnormalities in the femoral head/neck region and/or surrounding acetabulum. FAI can lead to early degenerative disease.
The femoroacetabular or hip joint is a large ball-and-socket synovial joint between the femoral head and the acetabulum.
articulation: ball and socket joint between the head of the femur and the acetabulum
ligaments: ischiofemoral, iliofemoral, pubofemoral and transverse acetabular li...
The femur (plural: femora) is the longest, most voluminous and strongest bone in the human body.
It is composed of the upper extremity, body and lower extremity and provides several muscular origins and insertions.
The upper extremity is composed of the head, neck, greater tr...
Femur sparing intrauterine growth restriction is considered by some authors as a particular type of intrauterine growth restriction (IUGR) 1. In this type, the femoral length is the only standard fetal biometric parameter unaffected while all others are reduced.
A femur x-ray, also known as femur series or femur radiograph, is a set of two x-rays performed of the entire femur. It is performed to look for evidence of injury (or pathology) affecting the humerus. It may be performed as a second test after a hip or knee x-ray has demonstrated a femoral frac...
Fetal rib fractures can be caused by certain skeletal dysplasias. These include:
osteogenesis imperfecta: type II - one of the classical causes of fetal rib fractures
achondrogenesis: type Ia - Houston-Harris sub type
Fibrodysplasia ossificans progressiva (FOP), previously known as myositis ossificans progressiva (MOP), is a rare, inherited disorder characterised by progressive fibrosis and ossification of muscles, tendons, fasciae, aponeuroses, and ligaments of multiple sites. It is disabling and ultimately ...
A fibrolipomatous hamartoma of the nerve (also known as a neural fibrolipoma) is a benign neoplasm of nerves, resulting from anomalous growth of fibroadipose tissue of the nerve sheath.
Fibrolipomatous hamartoma may be related to hypertrophy of mature fat and fibroblasts in the epine...
Fibromatosis refers to a wide range of soft tissue lesions that share an underlying histopathologic pattern of fibrous tissue proliferation. They can occur in a variety of anatomic sites (e.g. musculoskeletal, abdominopelvic, breast, etc.) and also vary in their behaviour, ranging from indolent/...
Fibromatosis colli is a rare form of infantile fibromatosis that occurs within the sternocleidomastoid muscle (SCM).
There may be a slight male predilection. It typically presents a few weeks after birth.
Presentation is usually with torticollis and is most...
Fibrosarcoma of the bone is a rare malignant bone tumor which may occur as a primary lesion, or secondarily after radiation treatment, dedifferentiation from other tumors 3 or pathologies such as Paget disease, bone infarction, or chronic osteomyelitis.
It is a distinct entity from...
Fibrous cortical defects (FCD) are benign bony lesions and are a type of fibroxanthoma, histologically identical to the larger non-ossifying fibroma (NOF).
Fibrous cortical defects typically occur in children (usually 2-15 years), and indeed are one of the most common benign bony ...
Fibrous dysplasia (FD) is a non-neoplastic tumour-like congenital process, manifested as a localised defect in osteoblastic differentiation and maturation, with the replacement of normal bone with large fibrous stroma and islands of immature woven bone. Fibrous dysplasia has a varied radiographi...
Fibrous joints are a type of joint where the bones are joined by strong fibrous tissue rich in collagen. These joints allow for very little movement (if any) and are often referred to as synarthroses.
cranial sutures between bones of the skull
gomphosis joints between teeth and alveo...
The differential for fibrous lesions is wide and includes:
osteofibrous dysplasia / adamantinoma
malignant fibrous histiocytoma / fibrosarcoma
Fibroxanthoma of bone is a confusing term that is sometimes used to encompass non-ossifying fibroma and fibrous cortical defect, and at other times synonymously with just non-ossifying fibromas. As non-ossifying fibroma and fibrous cortical defect are histologically the same, and differ only in ...
The fibula (plural: fibulae) is the smaller of the two bones of the leg. It is not directly involved in the transmission of weight but is important for ankle stability and acts as a source for numerous muscle attachments. It is commonly raised as a flap for reconstructive surgery.
Fibular hemimelia is a congenital lower limb anomaly characterised by partial or complete absence of fibula and includes a spectrum ranging from mild fibular hypoplasia to complete fibular aplasia 1.
Although rare in occurrence, it is the most common congenital absence of long bon...
The Ficat and Arlet classification uses a combination of plain radiographs, MRI, and clinical features to stage avascular necrosis of the femoral head.
plain radiograph: normal
clinical symptoms: nil
plain radiograph: normal or minor osteopenia
The Ficat classification of osteonecrosis is based on radiographic findings. In 1985 Dr Ficat published a modified version of his initial classification in 1980:
preclinical and preradiographic
diagnosis is suspected in one hip when the other has a definite disease - this is the stage...
The fifth lumbar vertebra (L5) is the largest of the five lumbar vertebrae and is considered an atypical vertebra due to its shape.
L5 is the largest, most inferior lumbar discovertebral unit in the vertebral column, and participates in forming the lumbar lordosis (from L1 to L5...
Filariasis refers to infection with nematodes (roundworms) of the family Filariodidea. There are three types of these thread-like filarial worms:
Wuchereria bancrofti: responsible for 90% of cases
Brugia malayi: causes most of the remainder of cases
B. timori: also causes the disease
It can ...
Finger clubbing, also called "drumstick fingers", is a common clinical sign in patients with heart or lung disease. The term is used to describe an enlargement of the distal phalanges of the fingers, giving them a drumstick or club-like appearance.
The underlying pathogenesis of fin...
Finger oblique view is a standard projection for radiographic assessment of the fingers. It is not required for follow-up studies for 'query Foreign Body' unless specifically requested.
patient is seated alongside the table (similar to a projection of hand)
from a pronated po...
Finger PA view is a standard projection for radiographic assessment of the fingers; it is one of three views of the finger series.
patient is seated alongside the table (similar to the projection of hand)
palmar aspect of pronated hand is placed over detector and extended fi...
The finger series is comprised, conventionally of a posteroanterior, oblique and a lateral view. The series examines in detail the distal, middle and proximal phalanx as well as the interphalangeal, metacarpophalangeal and carpometacarpal joints.
Note: the thumb (first digit) reviewed under th...
Finger lateral view is a standard projection for radiographic assessment of the fingers; it is one of three views of the finger series. it is divided into:
lateral index and middle fingers
lateral of ring and little fingers
Lateral of index and middle fingers
A mnemonic for finger tip lesions is:
G: glomus tumour
E: epidermoid/enchondroma/subungual exostosis
M: metastasis (almost exclusively lung)
The Finkelstein test is a clinical test used to assess the presence of De Quervain's tenosynovitis in people with wrist pain. It is perfomed by grasping the patients thumb and deviating the hand in the ulnar direction. If a sharp pain occurs along the distal radius this is considered to make de ...
The first metatarsal axis is represented by a line drawn down the longitudinal axis of the shaft of the first metatarsal. It can be drawn on lateral and DP radiographs and is used to measure the:
first metatarsal inclination angle
talo-first metatarsal angle
The first rib is the most superior of the twelve ribs. It is an atypical rib and is an important anatomical landmark and is one of the borders of the superior thoracic aperture.
Compared to a typical rib, the first rib is short and thick and it has a single articular f...
Fishtail deformity of the elbow is characterised by a contour abnormality of the distal humerus, which develops when the lateral trochlear ossification centres fails to develop or resorbs.
It is an uncommon complication usually following a distal humeral fracture in childhood. Whilst initially...
The term fish vertebra (also codfish vertebra) describes the biconcave appearance of vertebrae (especially lumbar vertebrae).
sickle cell disease
thalassemia major (rarely)
Flail chest or flail thoracic segment occurs when three or more contiguous ribs are fractured in two or more places. Clinically, a segment of only one or two ribs can act as a flail segment, hence there is some controversy between the clinical and radiological definitions.
Flare phenomenon or osteoblastic flare phenomenon refers to interval visualisation of lesions with a sclerotic rim around an initially lytic lesion or sclerosis of lesions previously undetected on radiograph or CT in the setting of follow-up of an oncological patient with other signs of partial ...
Flat bones are 1 of the 5 types of bones in the body and represent a group of bones (predominantly of the cranium) that have a relatively flat shape and form from intramembranous ossification.
The fleck sign is a small bony fragment seen in the Lisfranc space (between the base of the 1st and 2nd metatarsal) associated with avulsion of the Lisfranc ligament (at the base of the 2nd metatarsal). It is a very subtle, but important finding, since it predisposes to Lisfranc injury.
Flexion supracondylar humeral fractures account for only 2-4% of all supracondylar fractures 1. Unlike the much more common extension supracondylar fracture which are seen in children, flexion fractures are seen in older patients. They are usually the result of a fall directly onto a flexed elbo...
Flexion tear drop fractures are the most severe fracture of the cervical spine, often causing anterior cervical cord syndrome and quadriplegia.
It typically occurs from severe flexion and compression forces, most commonly at C5-6 (e.g. diving head first, motor vehicle coll...
Flexor carpi radialis (FCR) is a muscle found in the first layer of the anterior compartment of the forearm. It does not pass through the carpal tunnel, but rather by itself in a small separate tunnel between the superficial and deep layers of the flexor retinaculum along the scaphoid and trapez...
Flexor carpi ulnaris (FCU) is a muscle of the first layer of the anterior compartment of the forearm.
humeral head: medial epicondyle of the humerus
ulnar head: medial border of olecranon and posterior border of ulna
insertion: base of 5th metacarpal; hook of hamate, pisiform...
The flexor digiti minimi brevis muscle lies lateral to the abductor digiti minimi.
origin: hook of the hamate and flexor retinaculum
insertion: proximal phalanx of 5th digit
action: flexes 5th finger at metacarpophalangeal joint
arterial supply: ulnar artery
innervation: deep branc...
The flexor digiti minimi brevis muscle lies under the 5th metatarsal bone.
origin: base of metatarsal V and related sheath of fibularis longus tendon
insertion: lateral side of base of proximal phalanx of 5th toe
action: flexes 5th toe at metatarsophalangeal joint
arterial supply: l...
The flexor digitorum brevis muscle lies immediately superior to the plantar aponeurosis and inferior to the tendons of the flexor digitorum longus in the sole of the foot.
origin: medial process of calcaneal tuberosity and plantar aponeurosis
insertion: sides of plantar surface of mid...
The flexor digitorum longus (FDL) muscle is located on the tibial side of the leg within the deep posterior compartment of the leg. At its origin it is thin but as it descends, the muscle increases in size.
origin: medial side of posterior surface of the tibia
insertion: plantar surfa...
Flexor digitorum profundus (FDP) makes up the third layer of the anterior compartment of the forearm along with flexor pollicis longus. It passes through the carpal tunnel.
origin: proximal, anterior surface of ulna and adjacent interosseous membrane
insertion: volar surface of distal...
Flexor digitorum superficialis (FDS) is a muscle in the second (intermediate) layer of the anterior compartment of the forearm that splits into four tendons, passes under the flexor retinaculum and through the carpal tunnel, to insert into the middle phalanx of the 2nd-4th digits.
The flexor hallucis brevis muscle is one of the small muscles of the foot that is involved in flexion of the 1st toe. The hallux sesamoid bones are embedded within its tendon.
origin: plantar surface of cuboid
insertion: medial and lateral sesamoid bones of first metatarsal
The flexor hallucis longus (FHL) muscle is one of the muscles of the posterior deep compartment of the leg and along with flexor hallucis brevis, is involved in flexion of the great toe. Its tendon passes between the medial and lateral tubercles of the talus. It's tendon sheath may communicate w...
The flexor pollicis brevis muscle is distal to the abductor pollicis brevis.
origin: tubercle of the trapezium and flexor retinaculum
insertion: proximal phalanx of the thumb
action: flexes thumb at metacarpophalangeal joint
arterial supply: superficial palmar arch
Flexor pollicis longus (FPL) is one of the two muscles that make up the third layer of the anterior compartment of the forearm along with the flexor digitorum profundus. It is a deep muscle under abductor pollicis brevis muscle. It passes through the carpal tunnel.
The flexor retinaculum (also known as the transverse carpal ligament) is a rectangular-shaped fibrous band located at the ventral aspect of the wrist.
On the radial side, it attaches to the scaphoid tubercle and the ridge of the trapezium. On the ulnar side, it attaches to the pi...
Flexor retinaculum at the ankle is formed by reinforcement of the deep fascia of the leg by transverse collagen bundles and functions to prevent 'bowstringing' of tendons as they pass the tibiotalar joint. It forms the roof of the tarsal tunnel 1, 2.
medial malleolus of the tibia
The so-called flip-flop effect refers to a confusing MRI appearance of the skeletal system and subcutaneous tissues. It is seen in a variety of severe fat depletion conditions responsible for diffuse bone marrow serous atrophy and modification or loss of the subcutaneous fat.
Not to be confused...