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64 Cards in this Set

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Quadriceps Tendon Rupture
Tear of the anterior cruciate ligament and a nondisplaced lateral tibial plateau fracture

O'Donoghue's triad consists of an anterior cruciate ligament tear, medial collateral ligament as well as medial meniscal tear.
Lateral patellar dislocation

These MR images demonstrate the constellation of findings seen following relocation of a lateral patellar dislocation. Specifically, there is cortical disruption of the medial facet of the patella. In addition, a lateral femoral condylar bone bruise is identified. A joint effusion is also seen. Incidental note is made of a Baker's cyst.
Aneurysmal bone cyst

DIFF DX: Giant cell tumor, Chondroblastoma, Osteoblastoma, Fibrous dysplasia
ABC: long tubular bones and spine. -almost exclusively in the metaphysis. -Vertebral aneurysmal bone cysts generally arise in the posterior elements; however, may extend into the vertebral body.
Eccentric expansile lytic lesion Cortex thinned; however, maintained No periosteal reaction Respects the epiphysis
MR
Multiple cysts of different signal intensity representing different stages of blood by-products. Fluid-fluid levels from layering blood are not pathognomonic and can be seen in the other osseous lesion, i.e., giant cell tumor, simple bone cyst and chondroblastoma.
Pellegrini-Stieda disease

calcification or ossification of the medial collateral ligament at its insertion on the medial femoral condyle. This is a sequela of previous injury to the medial collateral ligament. It has been postulated that the calcification results from a knee sprain in which there is avulsion of the periosteum which subsequently ossifies or alternatively, the calcification may simply be calcification within a post traumatic hematoma
Fibroxanthoma

Fibroxanthoma (or benign fibrous histiocytoma) is similar to nonossifying fibroma. Its existence as a separate lesion from nonossifying fibroma is debated. Nearly all fibroxanthomas occur in patients older than 20 years of age. Many patients present with pain. In contraindication to nonossifying fibroma, fibroxanthoma is most common in the diaphysis or epiphysis of long bones as well as the sacrum and ilium. In addition, nonossifying fibroma nearly always manifests in patients under 20 years of age. The radiographic findings of fibroxanthoma are variable and generally nondiagnostic. They may resemble nonossifying fibroma, fibrous dysplasia, enchondroma, or eosinophilic granuloma. There have been reported cases of aggressive lesions with local spread and dissemination.
Secondary hyperparathyroidism related to renal osteodystrophy

The kidney is unable to hydroxylate vitamin D to form the active compound. This results in sustained hypocalcemia resulting in secondary hyperparathyroidism. Secondary hyperparathyroidism can also result from malabsorption of vitamin D, osteomalacia, and pseudohyperparathyroidism.
Secondary hyperparathyroidism results in bone resorption from the osteoclastic activity. Subperiosteal bone resorption is often found at the radial aspect of the phalanges of the hand. also occurs near articular surfaces, particularly at the acromioclavicular joint, sternoclavicular joint, and sacroiliac joints as well as the pubic symphysis. Brown tumors, which are lytic lesions, occur related to accumulation of fibrous tissue as well as giant cells. Bone sclerosis also occurs in secondary hyperparathyroidism at the superior and inferior end plates of the spine resulting in "Rugger Jersey" spine. The mechanism of bony sclerosis is not well estab
Volar intercalated segmental instability (VISI).

The lunate is tilted in a volar direction and the capitate is tilted dorsally. This results in scaphoid flexion and gives a scaphoidlunate angle measurement of 21° which is normally 30° - 60°. No fractures are shown
The three most common causes of carpal instability are scapholunate dissociation (rotary subluxation), dorsal intercalated segmental instability (DISI), and volar intercalated segmental instability (VISI) with scapholunate dissociation being most common
Simple (Solitary or Unicameral) Bone Cyst of Calcaneus

A centrally located radiolucent lesion with cortical thinning and mild osseous expansion is regarded as the radiographic hallmark. A thin sclerotic margin is a common finding. In the calcaneus, a cyst is a well-defined and radiolucent lesion, almost invariably occurring in the base of the calcaneal neck, just inferior to the anterior portion of the posterior facet.
The major differential diagnoses are a lipoma and thinning of the trabeculae (pseudotumor)
Lunotriquetral Coalition

Carpal coalition is a rather common, asymptomatic condition which may occur in association with a congenital syndrome but more commonly is an isolated finding. The syndromes in which carpal coalition has been described include arthrogryposis, Ellis-van Creveld syndrome, Holt-Oram syndrome, Turner's syndrome, among others. In addition, many carpal coalitions are familial. The most common site of coalition is between the lunate and triquetrum. It occurs most frequently in black males. Less common fusion anomalies include trapezium-trapezoid, capitate-hamate, and hamate-pisiform. The coalition may not be easily identifiable owing to the fact that many are incomplete. The majority, however, will demonstrate osseous fusions. Carpal coalition is secondary to a developmental abnormality. It is believed to be due to a delay in the natural programmed cell death leading to joint cavitation.
Erosive "inflammatory" osteoarthritis

In contradistinction to osteoarthritis, erosions are a common manifestation of erosive (inflammatory) osteoarthritis. The erosions most commonly begin in the central portion of the articulation which differs from the marginal erosions seen in rheumatoid arthritis. Central erosions are characteristic of erosive osteoarthritis. These are sharply marginated and located primarily within the interphalangeal joints. In severe cases, there may be bony ankylosis at the interphalangeal joints. Occasionally, erosive osteoarthritis may be mistaken for psoriatic arthritis. In contrast to erosive osteoarthritis, psoriasis demonstrates no osteophyte formation.
Bone infarct

Bone infarcts can be seen in many diseases including sickle cell disease, post-trauma, Gaucher's disease as well as in steroid use. Radiographic findings include patchy areas of lucency and sclerosis as well as bony collapse at articular surfaces.
Post-traumatic osteonecrosis involving the femoral head can be seen following a femoral neck fracture. Other common areas for post-traumatic osteonecrosis include the talus, scaphoid, humeral head as well as vertebral body.
Melorheostosis

Radiologic manifestations are most commonly limited to a single limb, although multiple limbs may on occasion be involved. Melorheostosis most commonly involves the lower extremity, and is rarely see in the skull, facial bones, and ribs. The findings most commonly consist of osseous excrescences extending along the length of a bone simulating the appearance of "candle wax" dripping down the side of a candle. In the carpal and tarsal bones, there may be more discrete rounded regions of bony sclerosis as well as adjacent soft tissue calcifications. Nucleide scintigraphy cases of melorheostosis demonstrate a region of increased nucleide uptake. MR imaging demonstrate regions of decreased signal intensity on all pulse sequences.
Aneurysmal bone cyst

The aneurysmal bone cyst is an unusual entity which is most likely the result of trauma or a tumor induced process. In approximately one third of cases, the pre-existing lesion can be identified. The most common of these pre-existing lesions are giant cell tumors which account for approximately one fourth of aneurysmal bone cysts. Other possible underlying etiologies include osteoblastomas, angiomas, and chondroblastomas. The vast majority of patients present with pain and/or swelling. Patients are most typically under the age of 20 with the vast majority of aneurysmal bone cysts presenting in patients under the age of 30. Greater than 50% of aneurysmal bone cysts occur in long bones with approximately 12 to 30% occurring in the spine. Aneurysmal bone cysts of the flat bones are uncommon, of which about 50% occur in the pelvis.
Osteopetrosis

The different forms of osteopetrosis are all characterized by failure of osteoclast to resorb bone, with resultant increase in the amount of bone
Osteopetrosis is generally subdivided into a precocious type (which is usually lethal), and a delayed type which may be relatively asymptomatic. The precocious type presents in infancy with the patient developing cranial nerve dysfunction, anemia, hepatosplenomegaly, and failure to thrive. The anemia is secondary to obliteration of the marrow cavity. Radiographs demonstrate diffuse osteosclerosis with uniformly dense vertebral bodies. Although called the lethal form of osteopetrosis, patients may actually live for a few years. The delayed form of osteopetrosis follows a somewhat more benign course. the vertebral endplate demonstrates markedly increased density giving the characteristic "sandwich" appearance.
Giant cell tumor with pathologic fracture

It is important to remember that the greater trochanter is an apophysis which is considered an epiphyseal equivalent for differential purposes. Given that the patient was 20 years old, the differential diagnosis of such a lesion includes: Giant cell tumor, chondroblastoma, eosinophilic granuloma and infection. The latter is less likely given the lack of any soft tissue mass.
In the older patient, differential considerations would include giant cell tumor, infection, malignant fibrous histiocytoma, plasmacytoma and metastases
Multiple hereditary exostoses.

This is an autosomal dominant disorder Changes in vertebral bodies can result in spinal cord compression. Other complications include growth disturbances, urinary or intestinal obstruction, and sarcomatous degeneration.
In this patient, it was possible to compare the present studies to those several years previous which showed no change.
Tillaux Fracture.

Anterior tubercle of the tibia avulses because of tension placed upon it by anteroinferior tibiofibular ligament. The mechanism of injury is external rotation of the foot. This fracture can be isolated or be seen with fractures of the malleoli. This fracture should not be confused with the juvenile Tillaux fracture which is a Salter-Harris type III fracture of the distal tibial epiphysis.
Blount's Disease

The differential for bow legging in infants include: 1) Mild rickets 2) A physiologic variant, found more frequently in black children 3) Blount's disease
Blount's disease is a progressive varus deformity of the lower extremity. It results from abnormal chondroepiphyseal growth on the medial side of the proximal tibial physis. This slowed and distorted growth of the medial physis causes a progressive bowing of the leg. Eventually, the lateral collateral and cruciate ligaments become less competent, such that the deformity is more severe on standing. The infantile form tends to be bilateral, while the childhood form is usually unilateral.
Treatment: Children can be treated by bracing, epiphyseal stapling, osteotomies, or in extreme cases, by intra-epiphyseal corrective realignment
Ankylosing Spondylitis

It is characterized by involvement of the sacroiliac joints, the spinal apophyseal joints, and the paravertebral soft tissues. Almost all patients are positive for HLA/B27 antigen. The blood rheumatoid factor is characteristically negative.
bamboo spine with universal syndesmophytosis. Subluxations rarely at the atlantoaxial joint may occur as in rheumatoid arthritis with similar serious potential. When the disease begins in adolescence or earlier it is referred to as juvenile ankylosing spondylitis, the mean age group in these individuals being ten to twelve years of age.
Infectious Tenosynovitis/Palmar Abscess

These images demonstrate foci of bright T2 signal surrounding the extensor carpi radialis brevis and longus tendons and minimal brightening surrounding the extensor pollicis longus tendon. Following the intravenous administration of gadolinium the area around the extensor pollicis longus tendon enhances as does the area immediately surrounding the extensor carpi tendons. Just medial to the extensor carpi tendons is a large fluid collection with rim enhancement. The overall appearance is consistent with synovial inflammation surrounding the tendons with a focal inflammatory fluid collection. A second rim enhancing fluid collection is present flexor carpi ulnaris muscle.
Monteggia Fracture-Dislocation (Type 1)

There are four types of these injuries: This is the Bado classification. Type I is a fracture of the proximal and middle thirds of the ulna with anterior angulation associated with an anterior dislocation of the radial head. Type II is a fracture of the proximal ulna with posterior angulation and posterior or posterolateral dislocation of the radial head. Type III is a fracture of the proximal ulna with lateral or anterolateral dislocation of the radial head. Type IV are fractures of both the proximal ends of the radius and ulna with an anterior dislocation of the radial head. This is the least common.
Synovial osteochondromatosis

multiple cartilaginous nodules within the synovium
almost always affects large joints. The most common affected joints are the knee, hip, elbow, and shoulder. Extra-articular locations are uncommon. Patients generally present with chronic pain, stiffness, and swelling. The symptoms are slowly progressive with the eventual development of secondary degenerative osteoarthritis. In approximately 5 to 30% of cases there may be no identifiable calcifications within the joint. Well defined bony erosions may be identified. The most common finding is multiple rounded calcified or ossified loose bodies within the expected position of the synovium. These rounded densities often have central lucencies. The densities are often uniform in size as well as distribution throughout the joint. There have been a few reported cases of malignant transformation to synovial chondrosarcoma.
Unilateral Locked Facet

excessive flexion and rotation.
It occurs most commonly at C5/6 or C6/7, but may occur at C3/4, C4/5, and C7/T1 with somewhat less frequency.
With excessive rotation and flexion of the cervical spine, the facet of the superior vertebra moves upward and forward over the articular pillar of the vertebral body below causing the subsequent anterior "locking" of the superior facet. With this unilateral locked facet, there will be anterolisthesis of the superior vertebral body on the inferior body of up to (but not greater than) 50% of the width of a vertebral body. The anterolisthesis is often the first clue to the diagnosis. A somewhat more specific sign is the "bow tie" appearance which is formed when the articular pillar of the superior vertebral body is projected at the anterior margin of the more caudal articular pillar. In addition, on the AP view, the spinous processes are displaced toward the affected side.
The unilateral locked facet is considered a rela
Neurofibroma

The target appearance of a soft tissue mass on T2 weighted images is reported to be unique to neurofibromas. The appearance reflects the histology with dense collagen and fibrous tissue centrally and myxoid material in the periphery. While areas of low signal on T2 weighted images may be seen within schwannomas this characteristic target appearance has not been reported. No other soft tissue masses exhibit this imaging characteristic.
Chrondrosarcoma

Chrondrosarcoma affects patients between the ages of 30 and 60 years with pain being the most common presentation. They may occur as primary bone tumors or develop from a pre-existing lesion such as an enchondroma. Pain is a distinguishing feature between enchondromas and chondrosarcomas.
Chondrosarcomas most commonly arise in the long bones, most frequently within the femur. Other locations include the ribs, vertebrae and scapula.
Radiographically, a large osteolytic lesion can be seen. Organized calcific rings may suggest a low-grade tumor. Alternatively, an irregular calcified matrix may suggest a high-grade chondrosarcoma.
Lymphoma

Radiographic findings include multiple osteolytic lesions with a permeative appearance.
The differential diagnosis of a permeative lesion can be organized by age group. Neuroblastoma can be seen in infants. In addition, eosinophilic granuloma, leukemia and lymphoma can be seen in children. Lymphoma, multiple myeloma and metastatic disease can be seen in adults
Lisfranc fracture/dislocation of the foot

The Lisfranc injury is lateral dislocation of the metatarsals in relation to the cuneiforms. There are two types of Lisfranc fracture dislocations:
homolateral type describes lateral dislocation of the metatarsals in relation to the cuneiforms.
divergent type is seen with lateral dislocation of the second through fifth metatarsals and medial dislocation of the first metatarsal.
Osteochondroma of the L-3 spinous process

Osteochondromas are most often located in the long tubular bone but may on occasion be located in other unusual places such as small bones of the hands or the spine. Vertebral osteochondromas predominate in posterior osseous elements. All osteochondromas have a direct communication with the cortex as well as narrow cavity. The majority of osteochondromas are solitary in nature, but there is a hereditary form in which patients have multiple exostoses
The tip of the osteochondroma is often covered by a cap composed of hyaline cartilage. In children and adolescents, in whom there is active bone or growth, the cap may be as thick as 3 cm. However, in adults, the cap may be entirely absent. In addition, if the cartilage cap is thicker than 1 cm. in an adult, the suspicion for malignant transformation into a chondrosarcoma should be raised.
In the presence of mechanically significant friction or impingement upon adjacent soft tissues, a bursa may f
Necrotizing Fasciitis

Necrotizing fasciitis is a life threatening infection of the deep fascia with rapid progression and a high incidence of mortality. Early diagnosis is essential. Hyperintense signal of the deep fascia on T2-weighted images with or without associated changes in the adjacent muscle is considered diagnostic for necrotizing fasciitis in the appropriate clinical scenario. However, these findings are not specific for the diagnosis. Necrotizing fasciitis is typically a clinical diagnosis. MR may be useful in questionable cases and may be useful for preoperative planning, especially when there is extensive chest or abdominal wall involvement.
Myositis ossificans

describes a reparative process whereby benign heterotopic ossification occurs in the soft tissues.
80% of cases are located in the arm or thigh. Hence, involvement of the foot in this case is somewhat unusual. At 2-6 weeks from onset, radiographs show flocular calcified density in soft tissues. By 6-8 weeks, the ossification is well-circumscribed.
To distinguish myositis ossificans from osteosarcoma, it is recommended that serial radiographs be obtained. Osteosarcoma typically is associated with the metaphyseal region and shows a pattern of ossification which progresses from the center of the soft tissue mass to the periphery. The reverse is true of myositis, which ossifies in a peripheral to central fashion. Also, myositis typically overlies the diaphysis.
Treatment of myositis ossificans involves a period of immobilization followed by a progressive exercise regimen to maximize joint motion. Surgery is indicated when lesions cause limitation of joint movement o
Askin tumor

Aside the possibility of Askin tumor, the differential diagnosis in case of aggressive rapidly growing chest wall mass could be an Ewing sarcoma a lymphoma, Osteosarcoma, Fibro sarcoma, Reticulum cell sarcoma, Histiocytosis X, Bone metastases, Sub acute or chronic osteomyelitis. traditional differential diagnosis of a large chest wall mass in an adult has included lymphoma, sarcoma, metastatic lesions and benign lesions such as eosinophilic granuloma
Primitive neuroectodermal tumors of the chest wall, also called "Askin tumors," are rare, highly malignant tumors that have traditionally been felt to occur only in the pediatric or young adult population. These tumors are often very large at the time of diagnosis. The most common manifestation of these tumors includes pain from mass effect, often of several months duration.
EG

Diff dx:
Healing fracture Lymphoma/leukemia Plasmacytoma Aneurismal bone cyst Ewing sarcoma Hemangioma Infection/osteomyelitis/abscess Chondorblastoma
Osteopoikilosis

Osteopoikilosis (osteopathia condensans disseminata, or “spotted bone disease”), like enostosis or osteopathia striata, is typically an autosomal dominant, asymptomatic disorder characterized by an abnormality in the endochondral bone maturation process. Osteopoikilosis results in numerous rounded or oval, 2-10mm enostoses that appear in childhood and persist throughout life.
Diagnosis is usually made radiographically. When metastatic disease is concern, a bone scan will confirm the diagnosis. Osteopoikilosis, unlike osseous metastases, does not cause abnormal radiotracer uptake.
Brodie`s Abscess

Osteomyelitis is usually due to haematogenous spread of infection to bone . Commonest in children and young adults , the metaphysis of a long bone is usually affected reflecting its rich blood supply . The tibia is the commonest site affected (1). In the immature skeleton the physeal plate acts as a barrier preventing the spread of infection to the epiphysis . In infants , blood vessels penetrate the physis (growth plate) allowing infection to extend into or primarily affect the epiphysis (2). An intraosseous or Brodie`s abscess is a complication of subacute osteomyelitis and typically is seen on radiographs as a central , well-defined metaphyseal lucency with surronding reactive sclerosis. The presence of a channel or tract connecting this lucency to the physis is characteristic (3). Cortical extension results in periostitis and involvement of the extra-osseous soft-tissues .
The differential diagnosis of Brodie`s abscess includes bone neoplasms including, particu
Acro-osteolysis in hyperparathyroidism

Diff dx:
Scleroderma (associated with soft calcifications)
Psoriatic arthritis, associated with nail and skin deformities
Hyperparathyroidism, other findings include sub-periosteal resorption along the radial side of the middle phalanges
Cleidocranial dysostosis
Pyknodysostosis, along with aplasia/hypoplasia of the distal digits and seen in children
Polyvinylchloride exposure, workers with history of exposure
Progeria, premature ageing
Hajdu-Cheney Syndrome (familial idiopathic acro-osteolysis), rare syndrome and may be unilateral
Frostbite
Neuropathic, secondary to diabetes, syringomyelia etc
Leprosy, Lesch-Nyhan syndrome, epidermolysis bullosa and various other causes have also been described.
The patient in this case, in addition to hypercalcaemia, had other changes of hyperparathyroidism secondary to a parathyroid adenoma: sub-periosteal resorption seen at the proximal tibia bilaterally (Fig. 2) and along the radial aspect of the
Galeazzi fracture-dislocation

DISLOCATION OF THE INFERIOR RADIO-ULNAR JOINT OCCURRING IN ASSOCIATION WITH A FRACTURE OF THE RADIUS (Syn. Galeazzi fracture-dislocation, Piedmont fracture, Reverse Monteggia fracture)
Classically, the shaft of the radius is fractured.
Most commonly, at the junction of middle and distal thirds of the radius; has a short oblique or transverse configuration.
Distal radial fragment is displaced in an ulnar direction.
Dislocation of ulna usually occurs in a distal, dorsal and medial direction.
There may be an associated fracture of the ulnar head or styloid process.
Mnemonic: MUGR
Rheumatoid arthritis of the hand and wrist 

This is a disorder of unknown etiology characterized by synovial inflammation, pannus formation, and then destruction of bone and cartilage.
Rheumatoid arthritis of the hand and wrist

This is a disorder of unknown etiology characterized by synovial inflammation, pannus formation, and then destruction of bone and cartilage.
Particle disease (silicon synovitis in this case) of right wrist, secondary to mechanical wear of the prosthetic lunate

Findings:
Homogeneous density of lunate without trabecular pattern.
Subchondral lucencies in carpal bones, distal radius and ulnar styloid.
Pancarpal joint space narrowing.
differential diagnosis of subchondral cysts in the carpal bones and associated joint space narrowing might include:
post-traumatic osteoarthritis (especially with an appropriate history of prior trauma)
calcium pyrophosphate deposition disease
inflammatory arthritis
rheumatoid arthritis
gout
particle disease
osteonecrosis
neuropathic joint (unusual site, especially without involvement of hand proper)
infection (possible, but unlikely to affect carpal bones as a group).
SEE next page!
The etiology in this case is actually inflammatory. Particulate silicone abraded from the prosthesis has caused a hypertrophic villous synovitis with a chronic foreign-body type inflammatory reaction. Th
Idiopathic tumoral calcinosis

Although its etiology is unknown, there is some evidence suggesting an inborn abnormality of phosphorus metabolism. In this condition, deposits of calcium salts occur in the extracapsular soft tissues around joints.

Differential Diagnosis of Soft Tissue Calcifications
Renal Osteodystrophy
Idiopathic Tumoral Calcinosis
Milk-alkali syndrome
consumption of large amts. Of antacid/vit.d
Hypervitaminosis D
Metastatic calcification (hyperparathyroidism and chronic renal disease)
Heterotopic ossification
Scleroderma
Usually thin calcifications of hands, feet
Dermatomyositis
Usually associated with fine, reticular calcifications
Cysticercosis

With parasitic infestations, the morphology of the calcifications can be quite specific. With cysticercosis, the classic findings are multiple elongated foci of calcification just about the shape and size of grains of rice. These "rice grain" calcifications are usually oriented along the direction of the muscle fibers.
Other parasites causing soft tissue calcification:
Dracunculiasis
Loa loa (African eye worm disease)
Echinococcus
Onchocerciasis (River blindness)
Filariasis
Paragonimiasis
Sarcosporidiosis
Armillifer armillatus
Schistosomiasis
What are the findings? What is your differential diagnosis? What study would you like to see next?
What are the findings? What is your differential diagnosis? What study would you like to see next?
The differential diagnosis for a solitary site of periosteal reaction includes the following entities:
fracture
osteomyelitis
arthritis
malignant bone tumors
eosinophilic granuloma
subperiosteal hemorrhage
venous stasis
However, this patient has periosteal reaction in two different bones. This should make one consider causes of generalized periosteal reaction, which is a somewhat shorter list:
arthritis
child abuse
multifocal osteomyelitis
hypertrophic pulmonary osteoarthropathy
venous stasis

Hypertrophic osteoarthropathy (HOA)

was first described in 1868, and represents a clinical syndrome of clubbing of the digits of the hands and feet, enlargement of the extremities secondary to periarticular and osseous proliferation, and painful and swollen joints. There are two main types of HOA: primary (idiopathic) and secondary. The primary form, also known as pachydermoperiostosis, is a fairly rare autosomal dominant disorder that only represents about 3 - 5 % of all cases of
Vertebra plana, C3, due to involvement by multiple myeloma

nice mnemonic for vertebra plana is "MELT", which stands for:
metastasis, multiple myeloma
eosinophilic granuloma
lymphoma
trauma, tuberculosis
Fibrous dysplasia

This radiographic appearance strongly suggests a benign lesion. Entities to consider would include a healing fibrous cortical defect and fibrous dysplasia. If the patient had already received chemotherapy for her breast carcinoma, one could also consider the possibility of a treated and healing metastasis
Rheumatoid arthritis with pannus formation eroding the dens anteriorly and disrupting the transverse ligament, with ensuing cervical instability at C1-C2. In going from extension to flexion the predental space widens from 3 mm to 8 mm
Spinal chordoma

Chordoma is a destructive bone tumour believed to arise from notochord cell rests, which are normally precursors of vertebrae and intervertebral dics. The usual clinical presentation is in males between the ages of 40 and 70 years. It is locally malignant with a strong tendency to recur after attempted excision. Metastatic spread is unusual. The lesions are slow growing and become apparent due to pressure symptoms, with or without localised pain. Approximately half of the lesions arise in the sacrum and/or coccyx, the others in the basioccipital and basisphenoid regions of the skull. A vertebral origin is found in only 15% of patients. Adjacent vertebrae may be involved.
When the lesion is located in the sacrum, plasmocytoma and giant cell tumour should be considered in the differential diagnosis. When the lesion is located in the basioccipital region, chondrosarcoma should be considered. Because of the possibility of the presence of chordoma in vertebral bodies, we suggest that it should be included in the differential diagnosis of osteolytic lesions of this area.
Ivory vertebra: non-Hodgkin's lymphoma

Solitary dense vertebrae, as well as in lymphoma, are also seen in osteoblastic metastases (prostate/breast), haemangioma (coarse trabecular pattern, vertical in orientation), Paget's disease (tends to involve the posterior elements as well as displaying expansion of the body), osteopetrosis, sickle cell anaemia, fluorosis, systemic mastocytosis, tuberculous infection, metastatic carcinoid tumour, osetoblastoma, osteosarcoma and even primary Ewing's sarcoma
Brown tumours simulating neoplasia

The commonest lesion showing fluid-fluid levels with haemorrhage on CT and/or MRI is primary or secondary ABC (1,2). The presence of fluid-fluid levels in an osseous lesion is not pathognomonic of a specific lesion (3). The association of fluid-fluid levels and brown tumours has recently been reported (4). Although not previously reported, it is not unexpected to find fluid-fluid levels in brown tumours since these tumours often contain haemorrhage (4).
Osteosarcoma of the pelvis in an 80 years old woman

Osteosarcomas are infrequently found in the pelvis and spine. Histologically it is pleomorphic. Two diagnostic features exist: a production of osteoid tissue and presence of alkaline phosphatase within the tumour cells. If cells of cartilage origin are present calcification may be a presenting feature. Our primary diagnosis in this case was chondrosarcoma. Osteosarcoma occurs in older age groups of patients usually associated with Paget’s disease or radiation therapy following treatment of another cancer. In our case there were no signs or history of Paget’s disease, fibrous dysplasia, radiation therapy or existence of osteoblastoma. Furthermore low grade osteosarcoma and parosteal osteosarcoma occur in an older patient population than conventional osteosarcoma.
Langerhans Cell Histiocytosis

Pathohistologically, it is characterized by a granulomatous proliferation of the reticulum cells at one or several sites in the reticuloendothelial system. The etiology is unknown. It is possibly related to prior infection. The disease may occur in the skeleton, spleen, thymus, lymph nodes and skin. There are three major manifestations of histiocytosis X: eosinophilic granuloma, Hand-Schüller-Christian disease and Letterer-Siwe disease. It is believed that these three disorders are expression of the same basic pathological process.
The imaging findings of skeletal histiocytosis resemble those of osteomyelitis, Ewing’s sarcoma, lymphoma or multiple myeloma.
Tuberculous arthritis of the knee

In most cases, the infection is monoarticular, but polyarticular localisation is also possible. The hip, knee and spine are most frequently affected. Immunosuppression (AIDS), corticosteroid therapy, trauma or alcohol abuse are well known predisposing factors. The diagnosis is difficult to obtain because the disease is rare, the radiographic signs are difficult to differentiate from other types of septic arthritis and the difficulty of growing Mycobacterium Tuberculo-sis. In the differential diagnosis, following diseases must be included : pigmented villonodular synovitis, idiopathic synovial osteochondromatosis, juvenile chronic arthritis, rheumatoid arthritis, gout, pyrophosphate arthropathy, seronegative spondylarthropathy, chondrolysis, chondral atrophy, osteoarthritis and haemofilia.
Osteoblastoma of the radius

most osteoblastomas localise in the arch of the vertebrae (pedicle, lamina, and spinous process) and sacrum [2]. A smaller number have a predilection for the shafts of long bones (upper extremity 7%, lower extremity 25%). An important feature that distinguishes osteoid osteoma from osteoblastoma is the size of the lesion. Osteoid osteoma is a small tumour, rarely exceeding 1 cm and is self-limiting. Osteoblastoma, however, is a large lesion (average 3.5 cm); it is rarely under 2 cm and may enlarge to 10 cm. As in cases of osteoid osteoma, local pain is a common manifestation of osteoblastoma [3], although generally it is mild. Accentuation of pain at night and its amelioration with salicylates are inconstant clinical features of osteoblastoma
Scleroderma With Acroosteolysis

The differential diagnosis is as follows: psoriasis, diabetes, hyperparathyroid, frostbite, sarcoidosis, leprosy, occupational exposures (polyvinyl chloride), post-traumatic and congenital (syndrome of Hajdu and Cheney).
Meniscal ossicle

Meniscal ossicles are rare
Etiology unknown: vestigial, trauma
Patients can be asymptomatic or have local pain and swelling
Location - most commonly found within the posterior horn of the medial meniscus
Radiographically, these ossicles often are mistaken for intra-articular loose bodies
MR demonstrates a corticated structure following marrow signal characteristics of all sequences
Arthroscopy can also diagnose the meniscal ossicle, which can appear as a swelling in the meniscus
If the patient is asymptomatic before the time of diagnosis, removal of the ossicle may not be indicated and normal function is possible with the ossicle retained
Neuromuscular arthropathy secondary to poliomyelitis

Marked joint space narrowing, extensive osteoporosis with thin tubular diaphyseal structures
osteoporosis is a profound effect of this disease. Its etiology is thought to be similar to that which follows muscular inactivity with long-standing immobilization
2 year old boy who refuses to bear weight
2 year old boy who refuses to bear weight
Septic arthritis, right hip, due to staphylococcus aureus

In a normal child this space should be fairly symmetrical between the right and left side. Indeed, if these measurements differ by as much as 1 mm, one should consider it to be abnormal. The differential diagnosis of such widening includes:
normal variant in ossification of femoral capital epiphyses
joint effusion from any cause
septic joint
hemarthrosis
other
Cleidocranial dysplasia.

autosomal dominant
affecting midline structures. If you painted a big, broad stripe down the midline with a paintbrush from skull to groin, you'd paint over a lot of structures involved with this syndrome
large head with delayed suture closure, Wormian bones, hypertelorism, a small face, dental dysplasia, hypoplasia or aplasia of the clavicles, a narrow pelvis, and several varieties of spinal abnormalities. Just about every other bone in the body may be involved as well, including the ossicles of the ear. Despite the midline tendency, the appendicular skeleton is also frequently involved.
Osteonecrosis, both humeral heads, due to steroids used to treat this patient's chronic leukemia
Osteopetrosis
Paget's disease, right proximal femur

No one really knows what the real cause of Paget's disease is, but the smart money is on a slow viral infection, since one can see virus-like bodies in the osteoclasts on electron micrography in these patients. Which virus? This is unknown, although these viral bodies are morphologically similar to those of measles virus or respiratory syncytial virus.
Paget's disease can be divided into 3 major phases: 1) lytic ; 2) mixed lytic-sclerotic; and 3) sclerotic phases
Metastatic renal cell carcinoma, proximal radius

Fibrous dysplasia: possible, but less likely in someone this old.
Enchondroma/Eosinophilic granuloma: Without any visible chondroid matrix, enchondroma would be a lot less likely. E.G. is unlikely in this age group.
Giant cell tumor: possible, especially extending to the joint space like this.
Non-ossifying fibroma: very unlikely in this age group. Also, they tend to be more eccentric than this.
Osteoblastoma: unlikely. They tend to occur mostly in the posterior elements of the spine.
Met/myeloma: very likely. Certain mets, like renal cell and thyroid carcinoma can be extremely expansile.
Aneurysmal bone cyst: possible, for same reason as giant cell tumor.
Simple Cyst: very unlikely. This patient is a bit old for a simple cyst, and this lucent lesion appears a bit too complex for a simple cyst.
Hyperparathyroidism/Hemangioma: possible.
Infection: unlikely.
Chondroblastoma: possible, for same reason as giant cell tumor.
Chronic, recurrent anterior dislocations of left shoulder, with Hill-Sachs deformity of humeral head and osseous Bankart lesion of anterioinferior glenoid rim.
Secondary osteoarthritis.
Giant cell tumor of the greater trochanter of the right femur

chondroblastoma, giant cell tumor, aneurysmal bone cysts, or infection. You might even consider these four entities to be the "four horsemen of the apophysis". The sharp boundaries of this lesion make infection unlikely. Chondroblastoma is relatively rare, so the most likely things in the differential are giant cell tumor and aneurysmal bone cyst. This case happens to be a giant cell tumor.
Enchondroma, left tibia

we are dealing with either an enchondroma or a low grade chondrosarcoma. The slice on the right shows some endosteal scalloping. This finding is a bit worrisome, since it is an indication that this lesion is a bit more aggressive than the average enchondroma, and makes low grade chondrosarcoma more likely. This latter finding is worrisome enough to make the surgeon consider a biopsy of the lesion.