Introduction to Bone Introduction to Bone AbnormalityAbnormality

Abnormal Contour, Size and Shape Abnormal Contour, Size and Shape

• Focal abnormalities make one think of a focal process.

• Generalized or diffuse abnormalities should suggest a more global process, such as a congenital dysplasia or a metabolic disorder

• Focal– fracture – surgery – infection – tumor

• Diffuse– dysplasia – metabolic

•

Young patient has a very subtle fracture of the distal radial metaphysis, known as a "torus" fracture.

                  

This patient has the syndrome of multiple hereditary This patient has the syndrome of multiple hereditary exostoses, a relatively common type of skeletal exostoses, a relatively common type of skeletal

dysplasia. Involvement is noted in thedysplasia. Involvement is noted in the distal femurs, and distal femurs, and both proximal and distal ends of both tibias and fibulas, both proximal and distal ends of both tibias and fibulas, as evidenced by bizarre enlargement of the metaphyses as evidenced by bizarre enlargement of the metaphyses

and numerous exostoses (arrows). and numerous exostoses (arrows).

                

Paget's disease,Paget's disease, involving the right hemipelvis and left involving the right hemipelvis and left

proximal femur. These two bones are enlarged with respect proximal femur. These two bones are enlarged with respect to their uninvolved contralateral counterparts -- this is best to their uninvolved contralateral counterparts -- this is best seen by comparing the enlarged right pubis (arrow) to the seen by comparing the enlarged right pubis (arrow) to the

uninvolved left pubisuninvolved left pubis

•

                                        

Alignment Alignment

• Joint alignment :– to start looking for abnormalities in the

musculoskeletal system. – With most joints, there are two surfaces that are

fairly congruent (i.e. similarly shaped) should be lined up with each other. Most of the joints in the extremities have a convex (ball) side and a concave (cup) side. To be in anatomic alignment, the "ball" should be in the "cup". If the ball is somewhere between the center of the cup and the rim of the cup, we call it subluxation.subluxation. If the ball is totally out of the cup, we call it a dislocation. dislocation.

Formal definitions Formal definitions

• SubluxationA displacement of a bone in relation to the apposing bone at the joint, resulting in a partial loss of continuity of the joint surfaces.

• DislocationA displacement of a bone in relation to the apposing bone at the joint, resulting in a complete loss of continuity of the joint surfaces.

• Diastasis A displacement of a bone in relation to the apposing bone in a slightly movable (e.g. sacroiliac) or synarthrodial joint (cranial sutures).

AP view : AP view :

lateral subluxation of the right lateral subluxation of the right patellapatella

Anterior dislocation

                             

                               

Cartilage Cartilage

• Can't really see cartilage on plain radiographs, but we can still use these films to infer a few rough ideas about how the cartilage is doing. Hyaline articular cartilage is what separates the bones in a synovial joint = the "joint space"

• Three findings: – decreased joint space – increased joint space – chondrocalcinosis

• The most common of these is decreased joint space, which usually implies some form of arthritis

Decreased Joint Space Decreased Joint Space

Joint space loss is not a terribly specific finding

Look for more specific findings such as: osteophytosis, erosions or chondrocalcinosis to

help figure out the type of arthritis.

The degree of joint space narrowing will help us to figure out just how bad the disorder is.

The joint space looks OK on a standard plain film series, one can't be sure that it is, in fact, OK.

The reason for this is that joint space narrowing may only be visible on a weight-bearing view of that joint.

• Statistically, the most likely arthropathy to cause joint space narrowing is:– osteoarthritis. – After that:

• , rheumatoid arthritis and calcium pyrophosphate deposition (CPPD) disease

• After that, well, almost any type of arthritis can eventually zap the cartilage, such as gout, psoriatic arthritis, septic arthritis, and others.

Marked joint space narrowing is noted in the superior Marked joint space narrowing is noted in the superior weight-bearing portion of the joint space in this patient with weight-bearing portion of the joint space in this patient with

osteoarthritis.osteoarthritis. Subchondral sclerosis and marked osteophytosis are also Subchondral sclerosis and marked osteophytosis are also

noted. noted.

                

• A widened joint space:– acromegaly – a large joint effusion.

• Chondrocalcinosis :– CPPD ( 95 %)– Hyperparathyroidism– Hemochromatosis.(less common)

Chondrocalcinosis (arrows) is noted in the hyaline Chondrocalcinosis (arrows) is noted in the hyaline articular cartilage and menisci of this patient with calcium articular cartilage and menisci of this patient with calcium

pyrophosphate deposition (CPPD) diseasepyrophosphate deposition (CPPD) disease

                             

Decreased Opacity (Lucency) Decreased Opacity (Lucency)

• Normal bone:– the clasts(remover) and blasts (creator) are more or less

in equilibrium, and new bone is formed at the same rate that old bone is reabsorbed.

– osteoclasts have the capability, when stimulated, of reabsorbing bone about 20 times faster than the osteoblasts can lay down new bone.

– The appearance of a diseased bone therefore depends to some extent on the aggressiveness of the disease process.

• With indolent processes, there may be time for the blasts to lay down some new bone, which will lead to increase opacity of the bone.

• In more aggressive process, however, the clasts have time to remove bone, but the blasts don't have enough time to lay down new bone in its place, will lead to decrease opacity (increased lucency) of the bone.

• Flavors of Lucency

• Lucent line• fracture

• Focal lucency• tumor • infection

• Diffuse lucency• drugs • endocrine / metabolic • tumor

• Lucent line – A linear lucency is the classic sign of a fracture.

              Focal lucency With focal lucencies, bone tumors and osteomyelitis are two of the top entities on the differential diagnosis

                                

white arrows, due to metastatic renal cell carcinoma. A pathologic fracture (black arrows) is noted through the medial margin of this lesion

Diffuse lucencyDiffuse lucency Osteoporosis is usually the most likely causeOsteoporosis is usually the most likely cause

Multiple myeloma can also present with diffuse osteopenia Multiple myeloma can also present with diffuse osteopenia without any focal lucent lesionswithout any focal lucent lesions

has a long history of rheumatoid arthritis treated with steroids

            

                   

               

osteoporosis, insufficiency fracture T6 &

L1vertebral body.

Increased Opacity (Sclerosis) Increased Opacity (Sclerosis)

Causes of Increased Opacity • Bone impaction or rotation

– fracture • Bone production

(reactive sclerosis)

– fracture• callus

– tumor• tumor bone formation or periosteal reaction

– Infection• Periosteal reaction

– osteoarthritis• subchondral sclerosis or osteophytosis

Bone impaction or rotationBone impaction or rotation

• The classic sign of a fracture is a lucent line.

• Other findings due to the fracture, such as increased opacity or cortical discontinuity.

                              

Focal area of increased opacity (white arrow) due to fracture impaction and fragment rotation

Fracture callusFracture callus

• Some fractures are so subtle that you may miss them altogether at first, and only diagnose them once they have started to heal due to the formation of fracture callus.

              

Obvious periosteal callus formation is seen along the medial margin of the metatarsal (arrows).

Reactive sclerosis due to tumorReactive sclerosis due to tumor

• more indolent process, osteoblasts activity may predominate, leading to reactive sclerosis (increased opacity). dense sclerosis of the S1 portion of the sacrum due to primary histiocytic lymphoma

• diffusely sclerotic metastasis are seen in the context of either a very indolent process (such as some cases of prostatic carcinoma) or a patient with diffusely lytic mets who has been successfully treated (with resultant healing and sclerosis of these metastatic deposits).

dense sclerosis of the S1 portion of the

sacrum due to primary

histiocytic lymphoma

                         

               

multiple sclerotic metastases (arrows) in the ilium and proximal femur due to prostatic carcinoma

Mixed lytic and sclerotic pattern seen The involved bony cortices are also quite thickened and the trabeculae are coarsened and thickened. This osseous enlargement is a feature that helps to distinguish Paget's disease from sclerotic metastases

Osteoporosis Osteoporosis

Definition:A condition with decreased skeletal mass characterized by

qualitatively normal but quantitatively deficient bone.

Radiographic Findings:– Increased radiolucency of bone on

radiographs. A patient may also develop insufficiency fractures.

• Lateral thoracic spine in a patient with severe osteoporosis. The spine appears diffusely osteopenic, and an insufficiency fracture of one of the thoracic vertebral bodies is noted

                

OsteomalaciaOsteomalacia

• Definition

– A condition with decreased mineralization of bone associated with the presence of non-mineralized osteoid seams.

• Radiographic Findings:– The most common radiographic finding

is osteopenia, which may not be distinguishable from that seen with osteoporosis.

osteomalacia. osteomalacia.

• osteomalacia.

                            

Periosteal Reaction Periosteal Reaction Types of Periosteal ReactionTypes of Periosteal Reaction

• slow-growing processes, the periosteum has plenty of time to respond to the process. That is, it can produce new bone just as fast as the lesion is growing

• rapidly growing processes, the periosteum cannot produce new bone as fast as the lesion is growing. Therefore, rather than a solid pattern of new bone formation, we see an interrupted pattern.

patternpattern

• Sunburst or hair on end periosteal Reaction:– the lesion grows rapidly but steadily, the periosteum will not

have enough time to lay down even a thin shell of bone, and the pattern may appear quite different.

– the tiny fibers that connect the periosteum to the bone (Sharpey's fibers) become stretched out perpendicular to the bone.

• Codmans triangle:– Another pattern seen in rapidly growing processes .– This is a bit of a misnomer, since there really is not a complete

triangle. – only the edges of the raised periosteum will ossify. When this

little bit of ossification is seen tangentially on a radiograph, it forms a small angle with the surface of the bone, but not a complete triangle.

Significance of Type of Periosteal ReactionSignificance of Type of Periosteal Reaction

benign or agressivebenign or agressive

• Causes of Solid Periosteal Reaction:– Osteomyelitis– Benign neoplasms

• osteoid osteoma

– Eosinophilic granuloma– Hypertrophic osteoarthropathy– Deep venous thrombosis (lower extremity)– Trauma (healing fracture)

• Causes of Aggressive (Interrupted) Periosteal Reaction – Osteomyelitis– Malignant neoplasms

• osteosarcoma • chondrosarcoma • fibrosarcoma • lymphoma • leukemia • metastasis

– Trauma

Solid periosteal reaction suggests that this is a benign process.

aggressive solid periosteal reaction the lesion is growing

too fast for this to occur.

The Ring Bone Rule The Ring Bone Rule • What is a ring bone?

– shaped like a ring, such as the big ring formed by the iliac and pubic bones.

– Ring bone equivalent: dual bone systems in the body that behave like a ring bone.

The general form of the ring bone rule is: – If you find a fracture or dislocation in a ring

bone or ring bone equivalent, look for another fracture or dislocation in the ring.

Ring Bones & EquivalentsRing Bones & Equivalents • Ring Bones

– main pelvic ring – obturator rings of pelvis – mandible and skull – zygomatic arch – ribs, sternum and spine – each vertebra – foramina transversaria in C-spine

• Ring Bone Equivalents– radius / ulna– tibia / fibula

anterior &posterior fracture is in the right obturator ring &

the right side of the sacrum    avulsed the inferior ramus of his left obturator ring

compare the sacral foraminal lines on one side with those on the other. Normally, these

lines are smooth and

arcuate.

Soft Tissue Soft Tissue

• swelling

• gas :– seen with penetrating injuries, following

surgery, and with soft tissue infections due to gas-forming organisms

• calcification

• Mass :– usually be due to a hematoma, an abscess,

or a tumor

New Imaging Paradigm New Imaging Paradigm

• The newer algorithm starts off a lot like the old one --:– If the initial plain films are positive for fracture :

-cast the patient for 6 - 8 weeks . – If the initial plain films are negative for fracture:

• undergo a special limited MR screening exam.• If MR is negative, then they are treated for pain, but not

casted. • If MR is positive for a scaphoid fracture, the patient is casted

as usual for 6 - 8 weeks.• If MR shows an occult fracture elsewhere, such as in the

distal radius, the wrist is casted, but the cast is removed once the patient's symptoms have abated

MR more sensitiveMR more sensitive

• MR can immediately demonstrate the bone marrow edema and hemorrhage that accompanies a fracture.

• Visualization of a fracture by MR does not require that the fracture be displaced, as it does with plain films.

                               

AP radiograph was initially read as negative for fracture.

                               

     

                              

     

A scaphoid fracture

• AP radiograph with

snuffbox tenderness high signal intensity

                      

    

                          

     

Arthritis Arthritis • Rule 1 :Sutton's Law -- go where the

money is. – This is the most powerful rule. It allows you to give

a differential diagnosis that will contain a patient's diagnosis in over 90 % of the arthritis cases you will ever see: in most practices are one of the following three entities:

• Osteoarthitis• Rheumatoid arthritis• CPPD arthropathy

Rule 2: Look for the hallmark Rule 2: Look for the hallmark finding firstfinding first

• there is a specific finding for each of the three main types of arthritis :

Type of Arthritis Hallmark Finding

osteoarthritis osteophytosis

rheumatoid A erosions

CPPD arthropathychondrocalcinosis

• Other findings:– , such as joint space narrowing,– subchondral cyst formation,– subchondral sclerosis, – etc. are indeed important, but not for

purposes of diagnosis. – They help indicate the severity of a

patient's disease, but don't tell you much about what they do have.

Osteoarthritis Osteoarthritis Degenerative alterations in a synovial joint.Degenerative alterations in a synovial joint.

• The hallmark finding is the osteophyte.

• Other findings : joint space narrowing, subchondral sclerosis, and subchondral cyst formation

                                           

     

                    

    

R A R A An inflammatory arthropathy of unknown etiology, characterized by An inflammatory arthropathy of unknown etiology, characterized by

synovial inflammation, pannus formation and erosion formation.synovial inflammation, pannus formation and erosion formation. • The classic finding

– is the marginal bony erosion, usually occurring first along the periarticular "bare" areas (intraarticular bone not covered by cartilage).

– One may also see subchondral cyst formation, juxtaarticular osteopenia, joint space narrowing, and occasionally, ankylosis.

Calcium Pyrophosphate Dihydrate (CPPD) Calcium Pyrophosphate Dihydrate (CPPD) Deposition DiseaseDeposition Disease

definitiondefinition• An idiopathic arthropathy characterized

by :– chondrocalcinosis (deposition of CPPD

crystals in the hyaline articular cartilage or in fibrocartilage):

• at the microscopic level.• If sufficient deposition of this material, can see it on

a radiograph.

Radiographic FindingsRadiographic Findings

• Chondrocalcinosis is the hallmark finding for this entity.

• While some patients have no other findings and are asymptomatic.

• Others may develop a significant secondary osteoarthritis.

• A few patients develop a very severe and destructive arthropathy that resembles a Charcot joint in its severity

Demons of the Musculoskeletal SystemDemons of the Musculoskeletal System

• Fracture, dislocation,subluxation.• Arthritis:

– OA, RA, CPPD

• Metabolic:– Osteoporotic,Osteomalacia, Paget

• Osteomyelitis• Neoplasia

– Metastasis,myeloma– Benign

• Osteonecrosis.

OsteomalaciaOsteomalacia

• Definition:– decreased mineralization of bone associated with

the presence of non-mineralized osteoid seams. .Radiographic finding is :

osteopenia, which may not be distinguishable from that seen with osteoporosis. Some patients may exhibit "Looser" zones (a.k.a "pseudofractures"), which are lucent zones in the cortical bone which represent radiographically visible osteoid seams

Paget's DiseasePaget's Disease

A condition of unknown cause affecting about 3 % of the population over 40 years of age. It is characterized by excessive and abnormal remodeling of bone.

Radiologic finding:Enlargement of an affected bone,

increased opacity of the involved bone,

disorganized and coarsened trabecular pattern

                                         

     

                    

    

OsteomyelitisOsteomyelitis

• Infection of the marrow space of a bone • Radiographic Findings

The earliest finding may be osteopenia. Periosteal reaction may occur adjacent to the involved bone.

osseous destruction may occur, followed by pathological fracture.

may also spread to an adjacent joint.

Loss of a subchondral line in a joint or evidence of bone destruction on both sides of a joint are strong signs for a septic joint.

OsteonecrosisOsteonecrosis

• Death of a portion of a bone (a.k.a. aseptic necrosis, avascular necrosis or bone infarct). This is multifactorial, with the most common cause being steroid use.

• Radiographic Finding:– Initially, the infarcted bone appears normal. – After several months, the infarcted bone may appear somewhat

smudged and slightly sclerotic.– With time, a zone of sclerosis forms along the border between

normal and infarcted bone.– If the infarct is located adjacent to an articular surface,

subchondral collapse may eventually occur, secondary to cumulative microfractures in dead bone, which is incapable of self-repair like living bone