Musculoskeletal Imaging

achondroplasia	Achondroplasia is an autosomal dominent anomaly that affects the cartilage growth and development. The individual is a short limbed dwarf with a relatively normal sized trunk, large head, frontal bossing, and a depressed nasal bridge. ULTRASOUND The diagnosis can be made by fetal ultrasound by progressive discordance between the femur length and biparietal diameter by age. The trident hand configuration can be seen if the fingers are fully extended. A skeletal survey is useful to confirm the diagnosis of achondroplasia. SKULL The skull is large, with a small narrow foramen magnum, and relatively small skull base. LIMBS Short wide tubular bones with metaphyseal cupping and flaring and irregular growth plates. Fibular overgrowth is present. The hand is broad with short metacarpals and phalanges, and a trident configuration. ‘Trident hand’: the fingers are all the same length and diverge into 2 pairs ‘Chevron’ deformity: V-shaped growth plate notches THORAX Short ribs with cupped anterior ends. VERTEBRAE A decreasing interpedicular distance within the lumbar spine (travelling caudally) short vertebral pedicles posterior vertebral body scalloping ‘Bullet-shaped’ vertebral bodies: with an anteroinferior anterior beak The vertebral bodies are short and flattened with relatively large intervertebral disk height, and there is congenitally narrowed spinal canal. Thoracolumbar gibbus in infancy. PELVIS ‘Tombstone’ appearance: squared small iliac wings with a small sciatic notch ‘Champagne glass’ pelvis: the pelvic inlet resembles a champagne glass flat acetabular roofs The iliac wings are small and squared,[5] with a narrow sciatic notch and horizontal acetabular roof. If the radiographic features are not classic, a search for a different diagnosis should be entertained. Because of the extremely deformed bone structure, people with achondroplasia are often "double jointed".
Acrocephalosyndactyly	Acrocephalosyndactyly = syndrome characterized by 1. increased height of skull vault due to generalized craniosynostosis (= acrocephaly, oxycephaly) 2. syndactyly of fingers / toes
Bayonet deformity (Madelung deformity)	Bayonet deformity (Madelung deformity) is a skeletal deformity of the wrist characterized by an acute angular configuration and palmar displacement of the proximal carpal row It is associated with Turner syndrome (10% of cases) and chondrodysplasia of the distal radial epiphysis, or Leri-Layani-Weill syndrome (dyschondrosteosis).
Bayonet fracture	Bayonet fracture is a configuration characterized by overlapping of fracture surfaces with resultant shortening
bone marrow edema	Earliest sign of osteonecrosis is bone marrow edema (nonspecific)
brachycephaly in osteogenesis imperfecta	Premature fusion of the coronal suture restricts anteroposterior skull growth and is followed by compensatory overgrowth of the sagittal suture laterally and lambdoid sutures caudally. The resultant skull deformity is referred to as brachycephaly (12) (Fig 2). The frontal fontanel is wider and remains open longer than normal
Bullet vertebra	Bullet vertebra indicates anterior beaks of the vertebral body and is seen in mucopolysaccharidosis (Morquio disease, Hurler disease) and achondroplasia
Cannonball	Cannonball metastases are one or more large, well-circumscribed metastatic nodules in the lungs that are classically seen in renal cell carcinoma but also can be seen in choriocarcinoma
cartilage interface sign	Shoulder ultrasound. Full-thickness tear: focal tendon defect/fluid; concave contour of bursal side of tendon; compressible tendon; cartilage interface sign (two parallel hyperechoic lines over humeral head)
Causes of Scalloping in Vertebral Bodies	Increased Intraspinal Pressure Intradural neoplasmsIntraspinal cysts Syringomyelia and hydromyelia Communicating hydrocephalus Dural Ectasia Marfan syndrome Ehlers-Danlos syndrome Neurofi bromatosis Bone Resorption Acromegaly Congenital Disorders Achondroplasia Morquio disease Hunter syndrome Osteogenesis imperfecta (tarda) Physiologic Scalloping
Cleft Palate (25%)	lack of fusion of mesenchymal masses of lateral palatine processes around 8th and 9th weeks MA Associated with: anomalies in 50% (most frequently clubfoot + polydactyly)
Cleidocranial Dysplasia	Cleidocranial dysplasia is an autosomal dominant syndrome affecting membranous bone. The locus for this dysplasia has been isolated to the short arm of chromosome 6. The abnormalities are caused by mutations in the CBFA1 gene, a transcription factor that activates osteoblastic differentiation (42). Cleidocranial dysplasia is characterized by widening of the fontanelles with broad lateral cranial diameter and multiple wormian bones along the lambdoid suture (Fig 14). The sutures and fontanelles close late. Associated skeletal anomalies include absent or hypoplastic clavicles, a widened pubic symphysis, multiple spinal anomalies, and hypoplastic middle and distal phalanges. Hearing loss occurs in 38% of those affected with cleidocranial dysplasia Anterior fontanelle has remained widely patent. Frontal (a) and lateral (b) skull radiographs show frontal bossing, brachycephaly, wide biparietal diameter, and wormian bones along the lambdoid sutures. Concomitant ossicular abnormalities required use of a hearing aid.
Complications of a fracture	Mal-union: failure to position a fracture correctly can result in abnormal alignment or mal-union, which may be unacceptable clinically. Delayed union: seek any systemic condition that may co-exist Non-union may result from: Poor alignment of the original fracture, with considerable seperation between the bone ends; A reactive sclerosis, with poor joining qualities; Ischemic necrosis; or Infection Diffuse osteoporosis: results from bone imobilisation by plaster casts. A severe form, Sudeck's atrophy, is accompanied by pain, soft tissue swelling and skin chnages.  Soft tissue damage: extensive traumatic damage may result in myositis ossificans. If blood vessel damage occurs, distal ischemic (Volkmann) contracture may result. ISchemic necrosis: Femoral head after subcapital fracture The humeral head The Scaphoid The changes in the ischemic bone, which may later collapse and fragment, detected on MR
Corner Sign	• Corner sign: metaphyseal fractures (Pelkan spurs)
crescent sign	OsteoneCrosis Stage III Plain film staging system (Ficat): translucent subcortical fracture line (crescent sign), flattening of femoral head
Dagger	Dagger has double-edged blade used for stabbing or thrusting The dagger sign is a single central radiodense line on frontal radiographs related to ossification of supraspinous and interspinous ligaments. Bony fusion of the adjacent lumbar vertebrae with syndesmophyte formation is characteristic for ankylosing spondylitis. In addition, there is a linear increased density running along the spinous processes
Dagger sign, trolley track sign	Dagger sign, trolley track sign: one or three dense lines along spine due to ossification of interspinous and supraspinous ligaments.
Double posterior cruciate ligament (PCL) sign and flipped meniscus sign	Bucket-handle: may become displaced or detached. There are characteristic signs by MRI: double posterior cruciate ligament (PCL) sign and flipped meniscus sign. The displaced fragment is typically seen within the intercondylar notch.
double-barrel sign	The double-barrel sign of simultaneous imaging of a portal vein branch and a second parallel tubular structure has been reported to be a highly accurate sign for intrahepatic biliary duct dilatation. Two parallel tubular structures may be identified within the substance of the liver in patients without intrahepatic bile duct dilatation when hepatic arteries are enlarged because of increased blood flow Sonogram shows double-barrel sign, which is simultaneous imaging of portal vein branch and parallel dilated intrahepatic biliary duct
Fallen fragment sign	Fallen fragment sign secondary to pathologic fracture is pathognomonic for UBC: fragment migrates to dependent portion of cyst.
Fat (marrow)-fluid (blood) interface sign (hemarthrosis) on cross-table lateral view	Fracture of the proximal tibia Fat (marrow)-fluid (blood) interface sign (hemarthrosis) on cross-table lateral view
Ghost sign	AP view: ghost sign (double-spinous process on C6-C7 caused by caudal displacement of the fractured tip of the spinous  process) Clay-shoveler's fracture
Hip dysplasias	Congenital dislocation of the hip: Girls, bilateral 25%. Acetabular dysplasia: increased acetabular angle, delayed femoral capital epiphysis, and lateral subluxation of the hip. Subluxation can pe partial. Look for dislocation contralaterally. Perthes' disease. Osteonecrosis of the proximal femoral capital epiphysis in Pethes disease may occur around the age of 6 years, boys, may be bilateral. Ischemic necrosis as a result of minor trauma to the blood supply. Deformity of the femoral head with premature osteoarthritis. Abnormality of the epipyseal plate and associated metaphysis.  Note the increased joint space. SUFE - Slipped upper femoral epiphysis: adolacent boys, ?related to growth spurts. Caused by posterior slip of the femoral capital epiphysis, 30% bilateral. The abnormal angulation of the femoral head in realtion to the femoral neck indicates a posterior slip.
Hole-within-a-hole sign	• Beveled-edge appearance may produce hole-within-a-hole sign (outer table is more destroyed than inner table; button sequestrum); best seen by CT. Eosinophilic granuloma (EG) Langerhans cell histiocytosis
lower-extremity bowing in children	lower-extremity bowing in children, including developmental bowing, congenital bowing, tibia vara (Blount disease) (Figs 1, 2), neurofibromatosis, osteogenesis imperfecta, rickets, camptomelic dysplasia, and achondroplasia
Madelung's deformity	Madelung's deformity: characteristic of premature fusion of the distal radius, with subsequent developmental abnormailites of the ulna and wrist (proximal carpal bones).
Mitten” polysyndactyly of soft tissues and bones	Apert’s syndrome
Morquio Syndrome MUCOPOLYSACCHARIDOSES (MORQUIO, HURLER, AND HUNTER SYNDROMES)	Morquio Syndrome.   A lateral plain film of the spine reveals a central beak or anterior bony projection off the vertebral bodies in this patient with Morquio syndrome. Hurler Syndrome.   A lateral plain film of the spine in this patient with Hurler syndrome shows an inferiorly placed bony projection extending anteriorly off the vertebral bodies Hurler Syndrome.   An anteroposterior plain film of the hand in this patient with Hurler syndrome shows a notch at the base of the fifth metacarpal, which is a characteristic finding in all of the mucopolysaccharidoses.
Mucopolysaccharidoses	Secondary to specific enzyme deficiencies Morquio-Brailsford syndrome Hurler syndrome or gargoylism: abnormal hook shaped vertebral body, fatal within the first 10 years. Abnormal trabecular pattern throughout the bones of the hand can also be seen.
Myositis Ossificans Progressiva	Myositis Ossificans Progressiva: rare, AD, formation of bone throughout muscle planes, ligaments, and soft tissue. The disease progresses from the upper thoracic spine, downwards and outwards, resulting inextensisve formation of bone around the thorax. The person dies of respiratory failure before reaching adulthood. No effective treatment of this condition. Fixation of the thoracic chage by extraosseous bone formation.
Neurofibromatosis	AD Skeletal changes 50% Pseudoarthroses, bowing deformaties, kyphoscoliosis with bowing of the posterior vertebral bodies Lateral cervical spine: abnormal development of the cervical spine, posterior scalloping of the vertebral bodies CXR: large neurofibroma in the apex
Osteonecrosis	• Early AVN: focal subchondral abnormalities (very specific) Dark band on T1W/bright band on T2W Double-line sign (T2W): bright inner band/dark outer band occurs later in disease process after the start of osseous repair • Late AVN: fibrosis of subchondral bone Dark on T1W and T2W images Femoral head collapse • Mitchell classification Class A (early disease): signal intensity analogous to fat (high on T1W and intermediate on T2W) Class B: signal intensity analogous to blood (high on T1W and T2W) Class C: signal intensity analogous to fluid (low on T1W and high on T2W) Class D (late disease): signal intensity analogous to fibrous tissue (low on T1W and T2W)
Patella baja (low patella)	Patella baja (low patella): this is associated with polio, juvenile chronic arthritis and achondroplasia
Patellar tooth sign	Patellar tooth sign (enthesopathy at the patellar attachment of the quadriceps tendon)
Pistol-grip deformity	MR image of pistol-grip deformity, which is abnormal flattening or convexity of usually concave femoral head–neck junction that causes cam type of femoroacetabular impingement secondary to a nonspherical femoral head impinging within the acetabulum It may be developmental or posttraumatic (e.g., as a result of slipped capital femoral epiphysis). With hip flexion, the nonspherical portion of the femoral neck impinges on the anterosuperior portion of the acetabulum. This causes primarily chondral injuries and leads to associated labral detachment
Platyspondyly generalisata Generalized Platyspondyly (Decreased Height of Vertebral Body)	Platyspondyly: flattened vertebral bodies associated with many hereditary systemic disorders (achondroplasia, spondyloepiphyseal dysplasia tarda, mucopolysaccharidosis, osteopetrosis, neurofibromatosis, osteogenesis imperfecta, thanatophoric dwarfism) disk spaces of normal height • Osteogenesis imperfecta • Dwarfism (thanatophoric, metatropic) • Morquio syndrome • Cushing syndrome
polydactyly	Associations: Bardet-Biedl syndrome, HIRSCHSPRUNG’S DISEASE, ELLIS–VAN CREVELD (CHONDROECTODERMAL DYSPLASIA) (GROUP 4), Frequently associated with: 1. Carpenter syndrome 2. Ellis-van Creveld syndrome 3. Meckel-Gruber syndrome 4. Polysyndactyly syndrome 5. Short rib-polydactyly syndrome 6. Trisomy 13 7. ASPHYXIATING THORACIC DYSPLASIA (JEUNE’S) (GROUP 4), 8. Smith-Lemli-Opitz syndrome Cleft Palate
Positive Fat Pad Sign and Sail sign	• Positive fat pad sign Anterior fat pad has the appearance of a sail (sail sign). A positive posterior fat pad is a good indicator of a fracture that is not normally seen. Radial head fractures
Prevertebral soft tissue swelling	Prevertebral soft tissue swelling (may be the only sign) Fractures of the odontoid process (dens)
rifle-barrel sign	Radiographs show rifle-barrel sign in pure posterior dislocation of shoulder, which can be recognized on frontal radiographs on basis of appearance of severely internally rotated humeral head described as resembling rifle barrel. In fact, it resembles smoothbore barrel because no rifling is seen on appearance of severely internally rotated humeral head. The rifle-barrel sign is radiographic recognition of the pure posterior dislocation of the shoulder on frontal radiographs on the basis of the appearance of the severely internally rotated humeral head described as resembling a rifle barrel [17]. Posterior shoulder dislocation is rare and reported to be unrecognized in as many as 50% of cases on radiographs. The relationship of the humeral head to the glenoid may appear normal on frontal radiographs of the shoulder. Radiographic recognition of the rare pure posterior dislocation of the shoulder on frontal radiographs Posterior shoulder dislocation is rare and reported to be unrecognized in as many as 50% of cases on radiographs. The relationship of the humeral head to the glenoid may appear normal on frontal radiographs of the shoulder. Radiographic recognition of the rare pure posterior dislocation of the shoulder on frontal radiographs depends on the appearance of a rifle-barrel sign. However, the rifle-barrel sign is in fact a misnomer. On Figure 7, smooth-bore and rifled barrels are shown. No rifling is seen on the appearance of the severely internally rotated humeral head
Saber-sheath trachea	Saber-sheath trachea indicates a trachea in which an increase is found in the outer posterior tracheal dimension with side-to-side narrowing involving the intrathoracic trachea (Fig. 8B). The coronal dimension is less than or equal to two thirds of the sagittal dimension. Usually, the extrathoracic trachea is normal. The cause for this shape could be secondary to expanded lung volume of upper lobes seen in patients with obstructive lung disease, which greatly restricts the potential side-to-side dimensions of the paratracheal mediastinum. This forces the trachea to remodel itself into a saber-sheath configuration in some patients with chronic obstructive pulmonary disease. This sign could also be secondary to deformity of tracheal cartilage or chronic injury. The saber-sheath trachea can simulate a mediastinal mass
Scimitar	Scimitar is slicing weapon with blade, modeled on lion’s claw. Distinctive curved blade ending with sharp point was capable of cutting off limbs or head of enemy in one stroke. Coronal reformatted CT shows scimitar syndrome, which is anomalous venous return from right lung with pulmonary veins draining to inferior vena cava and creating curvilinear density that has the shape of a scimitar on a chest radiograph. This anomalous pulmonary venous return can be either partial or total.
Sclerotic Bone diseases	Osteopetrosis (marble bone disease): Excessive increase in cortical bone thickness, reduction in the size of the medulla  and widespread sclerosis. Bone modelling deformaties. Osteopoikilosis: areas of sclerotic bone oftern seen around large joints, asymptomatic, diagnosed incidentally. Hand: widespread sclerotic, punctate areas of bone adjacent to joints are characteristic.
Sedimentation sign	CT may reveal cystic spaces with fluidfluid levels (sedimentation sign). Tumoral Calcinosis
Shiny corners:	Shiny corners: sclerosis at edges of endplates Ankylosing spondylitis (as)
Shoulder pad sign	Bulky soft tissue nodules (i.e., shoulder pad sign) Amyloid arthropathy
Spina Bifida	Spina Bifida failure of fusion of the posterior elements of the vertebral column. There is widening of the interpedicular distance. Neurological abnormality may result in abnormal development of the pelvis and lower limbs.
Spinal Stenosis	Spinal stenosis is defined as bony and soft tissue structures encroaching upon neural elements with resulting symptoms  Central Canal Stenosis. Simply noting whether the thecal sac is compressed or round will reliably determine central canal stenosis. Is it mild moderate or severe? Facet Hypertrophy Degenerative disease Facet Hypertrophy Ligment Flavum Hypertrophy on T2W Uncommon causes: bony overgrowth from Paget disease, achondroplasia, posttraumatic changes, and severe spondylolisthesis Neuroforaminal  Stenosis DJD of the facet with bony hypertrophy Less common: free disc fragments, postoperative scar, and from a lateral disc protrusion. Lateral recess  Stenosis Hypertrophy of the superior articular facet from DJD Other: disc fragments and post-operative scar can cause nerve root impingement. Facet Hypertrophy
Spinous process sign	Pseudospondylolisthesis (Fig. 5-22) Secondary to degenerative disk disease and/or apophyseal degenerative joint disease. Use spinous process sign to differentiate from true spondylolisthesis. In true spondylolisthesis, the spinous process stepoff is above the level of vertebral slip; whereas in pseudospondylolisthesis, the stepoff is below the level of the slip.
Syndactyly	Preaxial and postaxial polysyndactyly Apert syndrome, triploidy, Roberts syndrome Ipsilateral: Poland syndrome associated with ipsilateral syndactyly  ‘Mitten’ or ‘sock’ deformities: these are due to syndactyly (fused digits) of the hands and feet seen in DYSOTOSES (LOCALIZED DISORDERS WITH PREDOMINANT CRANIAL AND FACIAL INVOLVEMENT) Syndactyly = osseous ± cutaneous fusion of digits 1. Apert syndrome 2. Carpenter syndrome 3. Down syndrome 4. Neurofibromatosis 5. Poland syndrome 6. Others • Constriction band syndrome
Terry-Thomas sign and Ring sign	Scapholunate Dissociation (Stage 1) • Rupture of scaphoid ligaments • >3-mm gap between lunate and scaphoid (Terry-Thomas sign) • Ring sign on PA view secondary to rotary subluxation of scaphoid
Thanatophoric dwarfism ‘Telephone handle’ appearance of the long bones: this is due to metaphyseal flaring § ‘Cloverleaf skull’: this is due to lateral temporal bulging	Thanatophoric dwarfism  is the most common lethal skeletal dysplasia. Distinguishing features include small thorax, cloverleaf skull, large head, hydrocephalus, and polyhydramnios.  Short ribs with wide costochondral junctions ▶ severe platyspondyly ▶ horizontal acetabular roofs with medial spikes ▶ small sacroiliac notches ▶ marked shortness and bowing of the long bones ▶ irregular metaphyses ▶ short broad tubular bones in the hands and feet ▶ small scapulae
Trap door sign	Displacement of bone fragments into maxillary sinus (trap door sign) Pure Orbital Blow-out Fracture
Trident deformity	Trident deformity was described initially in achondroplastic dwarfism and in various chondrodysplasias. It is classically described as the second, third, and fourth fingers having the same length and third and fourth fingers that cannot be approximated. The resultant separation between the middle and ring fingers provides the trident appearance of the hand. The fourth and fifth fingers are parallel to each other. The hand is broad with short metacarpals and phalanges, and a trident configuration. Sometimes the trident deformity is described as the four last fingers having the same length and thus including the fifth finger in the abnormality. In this case the term “trident” is incorrect because trident implies the involvement of only three fingers. However, this description is almost universally used today in numerous publications. Trident acetabulum in asphyxiating thoracic dysplasia (Jeune syndrome) is seen as flat acetabular roofs with downward spikelike projections at the medial, lateral, and, sometimes, central aspects of the roofs
Trough sign	Trough sign (posterior dislocation) Linear impaction fracture of anterior humeral head • Trough sign: compression fracture of the anterior humeral surface, 15% (best seen on AP view with external rotation or axillary view)
tumbling-bullet sign	The appearance of a tumbling-bullet sign, a bullet falling freely within a fluid-filled posttraumatic bone lesion, indicates a unicameral bone cyst nature of the lesion. This is due to the same principle as a more frequently seen falling fragment sign in which a heavier object is able to move freely in a lighter environment.
Types of fracture	Comminuted: multiple bones are found at the fracture site Open (compound): a penetrating fracture, in which bone Is exposed to the air. Closed (simple): a fracture contained in the soft tissue Greenstick: only one side of the cortex is involved in the fracture; this type is common in children. Varus deformity: the proximal bone points laterally, with the distal fragment pointing medially (bow legged) Valgus deformity: the proximal bone points medially and the distal fragment points laterally (knocked-knee). Salter-Harris classification: refers to the fracture of long bones of children, in which the fracture involves the metaphysis, the epiphysis, and the epiphyseal line or growth plate. Premature fusion is a common complication of such fractures.
Ultrasound or MR (yo-yo sign)	Stener's lesion Occurs in a subset of patients with gamekeeper's thumb, when the ulnar collateral ligament is completely torn and displaced superficial and proximal to the adductor pollicis aponeurosis, preventing the UCL from returning to its  normal position. Detect with ultrasound or MR (yo-yo sign). Surgical lesion.
Wimberger's sign	Wimberger's sign: dense epiphyseal rim Wimberger's ring sign: circular, opaque radiologic shadow surrounding epiphyseal centers of ossification, which may result from bleeding Scurvy Deficiency of vitamin C (ascorbic acid) impairs the ability of connective tissue to produce collagen. Never occurs before 6 months of age because maternal stores are transmitted to fetus. Findings are most evident at sites of rapid bone growth (long bones). Rare. Radiographic Features (Fig. 5-137) Children • Generalized osteopenia • Dense metaphyseal line (Frankel) • Wimberger's sign: dense epiphyseal rim • Corner sign: metaphyseal fractures (Pelkan spurs) • Periosteal reaction (ossification) due to subperiosteal bleeding • Hemarthrosis: bleeding into joint Adults • Osteopenia and pathologic fractures Frankel's line: dense zone of provisional calcification Trümmerfeld zone : lucent metaphyseal band underlying Frankel's line Pelkan spur: metaphyseal spurs which result in cupping of the metaphysis
Wiskering	irregular bone growth at sites of tendinous insertions; ethesophytes, seen in DJD, DISH, and spondyloarthropathies
Y Sign	characteristic shape of thecal sac compression in lumbar epidural lipomatosis producing a stellate shape like a "Y"