Subcapital fracture is the most common type of intracapsular neck of femur fracture. The fracture line extends through the junction of the head and neck of femur.
Although many classifications are proposed Garden classification and Pauwel classification are generally followed fr...
The subchondral bone plate is composed of two layers that separate articular cartilage from the marrow-containing cancellous bone. The superficial layer consists of calcified cartilage, which is separated by the cement line (tidemark) from the deep layer of compact cortical bone 1-3.
A mnemonic for the causes of subchondral cysts is:
R: rheumatoid arthritis
S: synovial-based tumors
A subchondral fracture is a fracture of the trabecular cancellous bone just beneath the subchondral bone plate without disruption of the articular surface 1.
Subchondral insufficiency fractures are more common in elderly women 1,4,6. Subchondral fractures due to trauma can occur a...
A subchondral insufficiency fracture refers to a type of stress fracture that occurs below the chondral surface on a weight-bearing surface of a bone.
They tend to occur when normal physiological forces are repeatedly applied to an area of bone.
Typical sites include
Subchondral insufficiency fracture of the knee (SIF/SIFK) are stress fractures in the femoral condyles or tibial plateau that occur in the absence of acute trauma, typically affecting older adults.
The entity subsumes that previously known as spontaneous osteonecrosis of the knee (...
The subclavian nerve, also known as the nerve to subclavius, is an anterior branch from the C5 and C6 roots of the brachial plexus, and supplies the subclavius muscle.
The subclavian nerve is a small branch from the upper trunk of the brachial plexus that arises from the ...
The subclavian trunks are small short paired lymphatic trunks, each one draining its respective upper limb, and formed from efferent lymphatics draining from the apical (subclavicular) subgroup of the axillary nodes.
In turn the subclavian trunks pass through the cervicoaxillary canal and drain...
The subclavius muscle is a small triangular muscle of the pectoral region which depresses the shoulder.
origin: 1st costochondral joint
insertion: subclavian groove on the inferior aspect of the clavicle
innervation: nerve to subclavius
arterial supply: clavicular branch of the thor...
Subclavius posticus muscle is an accessory muscle in the root of the neck, lying between the subclavius muscle and the inferior belly of omohyoid. It has an incidence of ~ 7.5% 2,4.
origin: first costal cartilage
insertion: superior margin of scapula
nerve supply: nerve to subclavius...
The subcoracoid bursa is located anterior to subscapularis and beneath the coracoid process and extends caudal to the conjoined tendons of coracobrachialis and short head of biceps brachii. Fluid in the subcoracoid bursa does not normally communicate with the glenohumeral joint but may communica...
Subcoracoid impingement is an unusual form of shoulder impingement, and results from narrowing of the coracohumeral interval (space between the tip of the coracoid and the humerus). Narrowing is typically seen in the setting of prior rotator cuff repair, but occasionally also results from congen...
The subcoracoid triangle sign refers to the obliteration of the fat triangle between the coracohumeral ligament (superiorly), coracoid process / coracobrachialis (anterosuperiorly) and glenohumeral joint capsule (posteroinferiorly). It is considered a specific but not sensitive sign for adhesive...
A subcutaneous abscess is a manifestation of a spectrum of soft tissue skin infection which includes cellulitis and necrotizing fasciitis. It is a form of abscess which lies within the dermis and subdermal cutaneous layers. Along with dental abscesses, subcutaneous abscesses are the most common ...
The subcutaneous calcaneal bursa, also referred to as retroachilleal bursa or superficial retrocalcaneal bursa is located between the calcaneal tendon and the skin.
It is distinct from the retrocalcaneal bursa, which is located between the calcaneal tendon and the posterior angle of the calcan...
Subcutaneous calcification can be associated with a number of disorders. The list includes:
basal cell nevus syndrome
as a manifestation of systemic lupus erythematosus
Subcutaneous glucose monitors are becoming increasingly common in the monitoring and management of glucose for diabetics.
The majority of these are unlikely to impact routine imaging but are important to consider in MRI.
In the UK, the commonest device available on prescription is the FreeStyl...
Subcutaneous rheumatoid nodules are the most common extra-articular manifestation of rheumatoid arthritis, occurring in up to 40% of patients. They are universally associated with a positive rheumatoid factor (RF) 1.
The size of the nodules varies from 2 mm to 5 cm; they are firm, non-tender, ...
Subgaleal lipomas are benign adipose-containing tumors that occur between the periosteum and the galeal aponeurosis of the scalp.
They comprise 2% of all lipomas. They are more common in middle-aged patients and have a male predilection
Subgaleal lipomas pr...
A sublabral foramen or hole is simply separation of the labrum from the underlying glenoid. It is a labral variant of no clinical significance and can be confused with a SLAP lesion.
Sublabral foramen are located anterosuperiorly and can extend down to but not below the 3 o'clock position, whi...
Subluxed facet joint is the mildest form of facet dislocation in which the ligamentous injury leads to partial uncovering of facet joint (c.f. complete uncovering in perched facet). This results in mild anterior displacement of one vertebral body on another (anterolisthesis).
The suboccipital muscle group contains four paired muscles, three of which pairs belong to the suboccipital triangle. These muscles all lie below the occipital bone and are responsible for postural support of the head, as well as extension, lateral flexion and rotation. As these muscles are smal...
The suboccipital triangles are a paired triangular-shaped space formed by the configuration of three paired muscles in the posterior neck between the occipital bone, C1 and C2.
The suboccipital triangle has an inferomedial pointing apex (pointing towards the nuchal ligament) form...
Subperiosteal bone resorption is the most consistent and specific finding of hyperparathyroidism and is virtually pathognomonic of the condition.
While the terminal tufts of the phalanges are the most commonly involved bones, many others are involved:
tufts of the distal...
The subscapularis muscle is one of the four muscles that make up the rotator cuff, the others being: supraspinatus, infraspinatus and teres minor.
origin: subscapular fossa of the scapula
insertion: lesser tubercle of the humerus
some fibers also extend to the greater tubercle and bi...
The subscapularis recess, also known as the superior subscapularis recess or subscapularis bursa, is a normal extension of the glenohumeral joint capsule in between the superior and middle glenohumeral ligaments.
On sagittal oblique sequences and when distended with ...
Subspine impingement of the hip is a type of extra-articular hip impingement, also known as anterior inferior iliac spine impingement. This condition occurs when a low-lying or enlarged anterior inferior iliac spine contacts the femoral neck with hip flexion. Presenting symptoms of this conditio...
Subtalar arthritis refers to arthritis affecting the subtalar joint.
trauma: fractures (e.g. prior calcaneal fracture)
infection: septic arthritis
deposition disease: gout, pseudogout
tibialis posterior tendon dysfunction
Subtalar dislocations is the simultaneous dislocation of the talonavicular and talocalcaneal joints, without tibiotalar or talar neck fractures 1.
Subtalar dislocations comprise 1-2% of all dislocations.
Subtalar dislocations are often associated with high e...
The subtalar joint may refer to one or two articulations:
the anatomic subtalar joint, i.e. talocalcaneal joint
the clinical subtalar joint, i.e. talocalcaneal and talonavicular joints
Please see the main articles for further descriptions of the separate joints.
Subungual exostoses are benign osteocartilaginous tumors that occur beneath the nail bed.
These lesions are most commonly found in children and young adolescents 1,2.
Although they can be found beneath any nail, they most commonly affect the big (first) t...
The sulcus angle is formed by the trochlear opening of the knee, measuring the angle between the medial and lateral facets. Classically described in axial x-rays of the knee performed at 30-45º of flexion (skyline view), it is valuable in both CT and MR studies.
Its normal value...
Sunburst appearance is a type of periosteal reaction giving the appearance of a sunburst secondary to an aggressive periostitis. It should not be confused with the sunburst sign of meningioma vascularity.
The sunburst appearance occurs when the lesion grows too fast and the periosteum does not...
Superficial bursae are those bursae that are located superficial to the fibrous fascia. They form in the months to years following birth, as a result of direct pressure or friction 1. An example is the olecranon bursa.
In contrast, deep bursae are located deep in the fibrous fascia.
The superficial circumflex iliac artery is the smallest cutaneous branch of the common femoral artery. It contributes to the arterial supply of the anterolateral abdominal wall and groin.
origin: common femoral artery
course: pierces the fascia lata lateral to the saphenous opening an...
The superficial epigastric artery is a small cutaneous branch of the common femoral artery which contributes to the arterial supply of the anterior abdominal wall below the umbilicus.
origin: common femoral artery, approximately 1 cm below the inguinal ligament
course: passes superior...
The superficial inguinal lymph nodes (often shortened to superficial inguinal nodes) form a subgroup of the inguinal lymph nodes and are located in the superficial fascia of the upper thigh near the inguinal ligament and great saphenous vein.
They number around ten, although a range of 5-17 nod...
The superficial peroneal (fibular) nerve is one of two terminal branches of the common peroneal nerve.
origin: arises as a terminal branch of the common peroneal nerve in the lateral compartment of the leg
course: passes between peroneus longus muscle and the fibula proximally and per...
The superficial posterior 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 plantarflexion as all 3 muscles form the Achilles tendon. Of the two posterior compartments, the superficial compartment ...
The superficial posterior tibiotalar ligament (SPTTL) is the most posteriorly located superficial component of the four superficial components of the deltoid ligament 1-3.
The superficial posterior tibiotalar ligament is located superficial to the deep posterior tibiotalar ligame...
The superficial radial nerve, also known as the superficial branch of the radial nerve, is a sensory cutaneous nerve that arises from the radial nerve. It supplies the skin on the dorsum of the hand as well as providing articular branches to joints in the hand.
As a branc...
The superior gemellus muscle is a small triangular muscle in the gluteal region that together with the inferior gemellus and obturator internus muscles form the tricipital (three headed) triceps coxae which occupies the space between the piriformis muscle (superiorly) and quadratus femoris muscl...
The superior gluteal nerve is formed from posterior divisions of L4, L5 and S1 nerve roots of the sacral plexus. The nerve supplies branches to the gluteus minimus and medius muscles and terminates by innervating the tensor fasciae latae muscle.
The superior gluteal nerve...
Superior labral anterior posterior (SLAP) tears are injuries of the glenoid labrum, and can often be confused with a sublabral sulcus on MRI.
SLAP tears involve the superior glenoid labrum, where the long head of biceps tendon inserts. Unlike Bankart lesions and ALPSA lesions, they ...
The superior lumbar triangle, also known as the triangle of Grynfeltt-Lesshaft, is one of the locations for a lumbar hernia. It is not to be confused with the adjacent inferior lumbar triangle (of Petit).
medially: the quadratus lumborum muscle
superiorly: twelfth r...
Superior peroneal retinaculum injuries refer to a spectrum of acute and chronic injuries to the superior peroneal retinaculum in the ankle. They are one of the causes of lateral ankle pain and instability.
One method of grading is the Oden's classification 1,7 which...
The superior tibiofibular joint is a synovial joint between the superior aspects of the tibia and fibula and is one of the multiple sites of cartilaginous and fibrous articulation carrying the name of the tibiofibular joint.
fibula: flat facet of fibular head
The superior sublabral sulcus is a normal variant of the superior sublabral recess, which is normally present at the attachment of the biceps tendon to the glenoid labrum.
The superior sublabral sulcus has been described as being shallow or deep and may be continuous with a sublabral foramen if...
Supernumerary ribs occur most commonly as a cervical rib arising from C7 or a lumbar rib arising from L1. In extremely rare situations, there can be sacral, coccygeal, intrathoracic, or aberrant lumbar ribs 3. Rarely supernumerary ribs (cervical and lumbar ribs aside) have been found as 'normal'...
Superscan is intense symmetric activity in the bones with diminished renal and soft tissue activity on a Tc99m diphosphonate bone scan.
This appearance can result from a range of etiological factors:
diffuse metastatic disease
transitional cell c...
The supinator muscle is, as its name suggests, a supinator of the forearm. It is located in the deep layer of the posterior compartment of the forearm and together with brachialis, forms the floor of the cubital fossa.
origin: posterior proximal shaft of ulna; lateral epicondyle of hum...
A supra-acetabular fossa, also known as pseudodefect of acetabular cartilage, is an anatomic variant whereby a focal defect is evident within the subchondral bone of the acetabular roof. It is seen in as many as 10% of hips and is typically located at the 12 o'clock position both in the coronal ...
The supraclavicular foramen is a normal variant and typically found as an incidental finding on radiographs. It occurs in ~4% (range 2-6%) of the population.
Supraclavicular foramen appear as an osseous tunnel or tunnels, with the most typical position at the superior aspect of the junction of...
This is a basic article for medical students and other non-radiologists
Supracondylar fractures are the commonest fracture at the elbow in pediatric patients. They result from force applied across the elbow, usually following a fall. The supracondylar region is the weakest point in the developi...
Supracondylar humeral fractures, often simply referred to as supracondylar fractures, are a classic pediatric injury which requires vigilance as imaging findings can be subtle.
Simple supracondylar fractures are typically seen in younger children, and are uncommon in adults; 90% a...
A supracondylar spur, supracondylar process, supratrochlear spur, or avian spur of the distal anteromedial humeral cortex is an anatomical variant present in ~1% 1,2 of the population.
The supracondylar spur is typically located on the anteromedial humeral cortex, 5 cm proximal ...
The supraorbital foramen or notch is the small opening at the central edge of the superior orbital margin in the frontal bone just below the superciliary arches that transmits the supra-orbital nerve, artery and vein.
It is lateral to the supratrochlear foramen, where the supratrochlear nerve, ...
The supraorbital ridge, also known as the supraorbital margin or superciliary arch is the superior margin of the bony orbit. Part of the frontal bone, the supraorbital ridge contains the supraorbital foramen (or notch). The corrugator supercilii muscles arise from the medial end of the supraorbi...
The suprapatellar bursa, also known as the suprapatellar recess or suprapatellar pouch, is one of several bursae of the knee. It is located proximal to the knee joint, between the prefemoral and suprapatellar fat pads. As with all bursae, its purpose is to reduce friction between moving structur...
Suprapubic cartilaginous cysts (SPCC) are rare cystic lesions arising from the symphysis pubis thought to be degenerative in origin. They have also been called retropubic or subpubic cysts.
In the small number of cases in the literature, all bar one patient, have been female. The ...
The suprascapular nerve is the only branch of the upper trunk (C5 and C6) of the brachial plexus, supplying the supraspinatus and infraspinatus muscles and sensation to the acromioclavicular and glenohumeral joints.
The suprascapular nerve arises from the upper trunk of t...
Suprascapular neuropathy or suprascapular nerve entrapment occurs if the suprascapular nerve is compressed as it passes through the suprascapular notch or spinoglenoid notch.
Non-specific posterior shoulder pain and weakness.
masses (e.g. ganglion c...
The suprascapular notch is located on the superior aspect of the scapula, at the scapula's anterolateral aspect.
The suprascapular notch separates the superior border of the scapula from the anterior coracoid process.
Relations and/or boundaries
The suprascapular nerve passes ...
The supraspinatus muscle is one of the four muscles that make up the rotator cuff, the others being: infraspinatus, teres minor, and subscapularis.
origin: supraspinous fossa of the scapula
insertion: superior facet of the greater tubercle of the humerus
innervation: suprascapular ne...
Suprasternal tubercle is a sternal normal variant which forms when a suprasternal ossicle fuses with the manubrium 1. It can be unilateral or bilateral. It usually appears as triangular or pyramidal bony projection in continuity with the superior margin of manubrium. It is better depicted in cor...
The supratrochlear foramen is the small opening at the medial edge of the superior orbital margin in the frontal bone that transmitts the supratrochlear nerve, artery and vein. When incomplete, it forms a notch. It is variably present, and when absent the neurovascular bundle will simple exit th...
The sural nerve is a sensory nerve of the lower limb formed by the union of sural branch of the tibial nerve and the communicating sural branch of the common fibular nerve supplying sensation to the lower lateral aspect of the calf and foot.
It travels within subcutaneous tissue ...
Suspected physical abuse (SPA), also known as non-accidental injury (NAI) or inflicted injury, in infants and young children represents both ethical and legal challenges to treating physicians.
Radiologists may be the first clinical staff to suspect non-accidental injuries when confronted with ...
The sustentaculum tali is a horizontal shelf that arises from the anteromedial portion of the calcaneus. The superior surface is concave and articulates with the middle calcaneal surface of the talus. The inferior surface has a groove for the tendon of flexor hallucis longus.
There are many sutures of the skull, which are where skull bones meet. In general, sutures don't fuse until brain growth is complete, therefore allowing the skull to increase in size with the developing brain.
Sutures are fibrous joints with the periosteum externally and outer la...
Swan neck deformity is a deformity of the digits that consists of:
hyperextension of the proximal interphalangeal (PIP) joints
compensatory flexion of the distal interphalangeal (DIP) joints
Swan neck deformity is seen in 3,4:
rheumatoid arthritis (classical association)
The Swischuk line is helpful in differentiating pathological anterior displacement of the cervical spine from physiological displacement, termed pseudosubluxation.
the line is drawn from anterior aspect of posterior arch of C1 to anterior aspect of posterior arch of C3
There are a large number of causes for a symmetrical periosteal reaction 1,2:
chronic venous insufficiency
physiologic periostitis, most common cause before 6 months old
juvenile idiopathic arthritis
Symphalangism refers to ankylosis of the interphalangeal joints (i.e. fusion of the phalanges) in either the toes or the fingers. Less commonly, the metacarpophalangeal joints may be affected.
One study reports symphalangism of the fifth toe in ~55% (range 40-75%) of the populatio...
Symphyseal cleft injections (symphysography) are performed as both diagnostic and therapeutic measures for patients with (suspected) osteitis pubis, usually under CT or fluoroscopy.
suspected or confirmed osteitis pubis
factors to be considered as per any muscu...
Symphyses (singular: symphysis) are secondary cartilaginous joints composed of fibrocartilage (and hence also known as fibrocartilaginous joints). They are considered amphiarthroses, meaning that they allow only slight movement and are all found at the skeletal midline.
Synarthroses are a functional class of joint that permit very little or no movement under normal conditions.
fibrous joints such as cranial sutures
synchondroses (primary cartilaginous joints) such as growth plates
Synchondroses (singular: synchondrosis) are primary cartilaginous joints mainly found in the developing skeleton, but a few also persist in the mature skeleton as normal structures or as variants.
Synchondroses are cartilaginous unions between bone composed entirely of hyaline cartil...
Syndactyly (plural: syndactylies) refers to a congenital fusion of two or more digits. It may be confined to soft tissue (soft tissue syndactyly/simple syndactyly) or may involve bone (bony syndactyly/complex syndactyly).
The overall estimated incidence is at ~1 per 2,500 to 5,000...
Syndesmophytes are calcifications or heterotopic ossifications inside a spinal ligament or of the annulus fibrosus. They are seen in only a limited number of conditions including:
They can be classified as...
Syndesmoses (singular: syndesmosis) are a type of fibrous joint where strong collagen rich connective tissue holds two portions of bone together allowing very little movement. They consist of an interosseous membrane and ligamentous thickenings.
distal tibiofibular syndesmosis
Synovial chondromatosis (osteochondromatosis or synovial chondrometaplasia) also known as Reichel syndrome, is a disorder characterized by loose cartilaginous bodies which may, or may not be calcified or ossified.
It is classified under two main types:
primary synovial chondromatosis: predomin...
Synovial chondrosarcoma refers to a very rare malignant cartilaginous neoplasm arising from the synovium.
There can be a wide spectrum in age of presentation from from 25-75 years of age. A slight male predilection may be present.
It can either as a primary lesion (p...
Synovial cysts are para-articular fluid-filled sacs or pouch-like structures containing synovial fluid and lined by synovial membrane. They can occur around virtually every synovial joint in the body and also around tendon sheaths and bursae. Communication with the adjacent joint may or may not ...
Synovial enhancement is an imaging feature typically observed on MRI imaging. It can occur in various forms and can be focal or diffuse.
transient synovitis of the hip
tuberculous septic arthritis...
Synovial hemangiomas are rare benign vascular malformations that occur in relation to the joint. It is sometimes considered a subtype of soft tissue hemangiomas.
The lesions typically present in children and young adults. Occasionally patients can have recurrent haemarthroses 8.
Synovial joints are a type of joint with an articular capsule, consisting of an outer fibrous layer and an inner synovial membrane, which surrounds a fluid-filled synovial cavity. The articulating surfaces are covered by hyaline cartilage, designed to slide with little friction and to absorb com...
Synovial plicae are folds of synovium, thought to represent embryologic remnants. They are common, present in ~90% of arthroscopies 3.
They have been implicated in anterior knee pain and possibly in chondromalacia patellae although their role remains controversial 1,3.
Synovial sarcomas are relatively common intermediate-to-high grade malignant soft tissue tumors, often with an initial indolent course, affecting young patients, and most commonly involving the soft tissue surrounding the knees.
Synovial sarcomas typically present in adolescents a...
Synovitis refers to any of inflammatory process that affecting the synovium of joints or structures lined with synovium. It can take many morphological forms and occur from many etiologies. It may not necessarily be infective.
Specific sub types
infective synovitis / infectious syno...
Syphilis is the result of infection with the gram negative spirochete Treponema pallidum, subspecies pallidum. It results in a heterogeneous spectrum of disease with many systems that can potentially be involved, which are discussed separately.
Despite the discovery of penicillin...
Systemic lupus erythematosus (SLE) is a complex autoimmune disease with multisystem involvement. Although abnormalities in almost every aspect of the immune system have been found, the key defect is thought to result from a loss of self-tolerance to autoantigens.
There is a strong...
Musculoskeletal manifestations in patients with systemic lupus erythematosus are common and often symptomatic. Characteristic manifestations are seen in approximately 80% of patients, but many less characteristic manifestations are important to be aware of. Multiple different presenting complain...