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MUSCULOSKELETAL RADIOLOGY

Dr. Aoife Mc Erlean, Specialist Registrar in Radiology, Department of Radiology, Beaumont Hospital

Basic anatomy

Imaging modalities

Trauma

Metabolic bone disease

Arthritis

Neoplastic disease

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BASIC ANATOMY

Bone Bone is a rigid form of connective tissue which forms most of the skeleton and is the main supporting tissue of the body. Like all other living tissues it is dynamic and has its own arterial supply and venous and lymphatic drainage. In addition to being affected by many pathological processes, bone can also remodel itself according to different stressors- for example it may atrophy in a paralysed limb or become absorbed (e.g. in mandible following tooth extraction). The structure of a typical bone consists of three main parts: 1. Spongy (cancellous) /trabecular bone which occupies the centre of each bone

and may contain a central medullary or marrow cavity (long bones) or an air space (e.g. maxillary sinus)

2. Compact / cortical bone dense and forms the outer shell of each bone,

surrounding the central mass of spongy bone. 3. Periosteum is the fibrous connective tissue membrane which invests all bones.

The blood supply to the cortical bone comes from the periosteal arteries. A nutrient artery passes obliquely through the compact bone near the centre of the bone and supplies the cancellous bone and the bone marrow. (Figure 2)

The different parts of bone can be easily distinguished on radiographs. (Figure 1)

Figure 1

Cortical bone

Cancellous bone

Medullary cavity

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Development of bone Bones develop from mesenchyme (embryonic connective tissue). The mesenchyme model of a bone can undergo one of two methods of ossification. Membranous bone formation direct ossification, where mesenchyme becomes bone (intramembranous ossification) Endochondral bone formation mesenchyme is first converted into cartilage and then later becomes ossified by intracartilagenous ossification The long bones can be divided into a number of different parts. (Figure 3) Diaphysis -body of the long bone,

-formed from a primary ossification centre during embryonic development Metaphysis -part of the diaphysis near the epiphysis Epiphysis -end of the long bone,

-formed from a secondary ossification centre after birth

Nutrient vessel

Figure 2 Radiograph of a long bone demonstrating the site of the nutrient artery, which is visible as a linear lucency. It is important not to mistake this for a fracture

Figure 3

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The diaphysis grows in length by proliferation of cartilage at the metaphysis. In order for bones to grow in length, the bone formed from the diaphysis does not fuse with the bone formed from the epiphysis until adult size is reached. The epiphyseal plate (growth plate) is a plate of cartilage that intervenes between the diaphysis and epiphysis during the growth phase of bone. The epiphyseal cartilagenous plates are eventually replaced by bone when the diaphysis and metaphysis fuse. The bone formed at this site is particularly dense and on a radiograph it is recognisable as an epiphyseal line. Bone Marrow In adults there are two types of bone marrow which occupy the medullary (marrow) cavity

Red marrow active in haematopoiesis Yellow marrow- relatively inert and eventually becomes replaced by fat

Types of bones The skeleton can be divided into: Axial skeleton skull, vertebrae, ribs and sternum Appendicular skeleton- (limb bones) - femur, humerus etc. Bones can be classified as:

Long bones Short bones- occur in the foot and wrist Flat bones- often serve a protective function sternum , bones of the skull Sesamoid bones- round or oval nodules that develop in certain tendons (e.g. the

patella develops in the lower part of the quadriceps tendon called the patellar tendon). They protect the tendon from excessive wear.

Accessory bones common in the foot, and often occur where multiple ossification centres for a particular bone fail to fuse. It is important not to confuse them with fracture fragments

Vertebral body

Pedicle

Spinous process

Intervertebral disk space

Figure 4 Radiographic anatomy of a normal lumbar vertebra

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Cuneiforms

Navicular Cuboid

Talus

1st MT 2nd MT

3rd MT

4th MT

5th MT

Middle phalanx

Proximal phalanx

Distal phalanx

Figure 5 Normal radiographic anatomy of the foot MT metatarsal bone

P

H

C

TM

TQ L

U

TZ

SC

R

1st MC

2nd MC

3rdMC 4

th MC

5th MC

Figure 6 Radiograph of the carpal bones R radius U ulna SC scaphoid L lunate TQ triquetral P pisiform H hamate C capitate TZ trapezoid TM trapezium MC metacarpal

Calcaneus

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Joints Classification of joints

1. Fibrous joints Bones are united by fibrous tissue (synarthrosis). Examples: Interosseous membranes e.g. tibia and fibula, radius and ulna Skull sutures Gomphosis joint between tooth and bone

2. Cartilagenous joints Bones are united by hyaline cartilage or a combination of fibrous tissue and cartilage (fibrocartilage)

Primary cartilagenous joints (synchondroses)

Bones are united by hyaline cartilage Examples: Epiphyseal growth plate First costosternal joint

Secondary cartilagenous joints (symphyses)

The articulating surface of the bones is covered by hyaline cartilage and the bones are joined by fibrous tissue +/- fibrocartilage. Examples: Pubic symphysis Intervertebral disks Manubriosternal joint

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3. Synovial joints Synovial joints have a number of distinguishing features (figure 7)

Joint cavity containing synovial fluid Hyaline articular cartilage Articular capsule consisting of an inner synovial membrane and outer fibrous

capsule, which is usually re-inforced by accessory ligaments Synovial joints allow a wide range of motion and are classified according to their axes of movement, e.g. ball and socket joint (hip/glenohumeral joint), hinge joint (knee/elbow), plane joint (acromioclavicular joint), pivot joint (atlantoaxial joint) Examples:Appendicular skeleton Facet joints of spine Apophyseal joints of cervical spine Atlantoaxial joint Lower 2/3 of sacro-iliac joint Acromioclavicular joint

Figure 7 A typical synovial joint

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IMAGING TECHNIQUES There are many different ways to image the musculoskeletal system. The chosen technique depends usually on the clinical information provided by the referring doctor and on the suspected diagnosis. If a muscular injury is suspected, plain radiographs would not be sufficient, whereas an ultrasound or MR imaging may be more appropriate. On the other hand a series of plain radiographs is adequate to outrule a fracture in most situations. Some common imaging modalities include: Plain radiographs Ultrasound Computed tomography (CT) Magnetic resonance (MR) Nuclear medicine 1. Plain radiographs Basic principles of X-ray image formation A highly penetrating beam of x-rays pass through the patient. These x-rays are absorbed by the parts of the body according to the tissue density, thus creating an image made up of different densities. Dense tissues (e.g. cortical bone or calcified renal stones) stop more x-rays than less dense tissues such as muscle or fat. Therefore dense substances are termed radiopaque and less dense substances are radiolucent. (Table 1) Most radiolucent Most radiopaque

Air fat Water/soft tissues Cancellous bone Cortical bone

Least radiodense Most radiodense

Radiograph appearance (see figure 8) Black image Grey image White image

Table 1

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Figure 8 Lateral radiograph of a normal adult elbow demonstrating the densities of the different types of tissue

Common indications

Trauma- suspected bony injury Arthritis assessment Suspected bony pathology- tumour etc.

Ft pad

Soft tissues Cortical bone

Fat pad Cancellous bone

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2. Ultrasound Ultrasound is an imaging modality that uses high frequency sound waves to create an image. It does not involve ionising radiation. It is useful for imaging solid organs and soft tissues, including tendons, muscles and superficial masses. Sound waves do not penetrate bone so ultrasound plays no role in the assessment of adult bones. Common indications

Rotator cuff injury assessment Suspected Achilles tendon rupture Bakers cyst diagnosis Children assessment of congenital hip dysplasia

B A Figure 9 Ultrasound of the Achilles tendon A ultrasound image of a normal Achilles tendon demonstrating the

longitudinal tendon fibres B swollen disorganised tendon fibres consistent with complete rupture

of the Achilles tendon

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3. CT Computed tomography is most commonly used in the trauma situation. Although plain radiographs remain the cornerstone of basic trauma assessments, CT is often required to diagnose intra-abdominal/intracranial injuries prior to exploratory surgery. Modern technology and new software packages also enable 3D reconstruction of complex trauma which allows better surgical planning.

Figure 10 fracture of lateral tibial plateau A AP radiograph of knee showing an impacted

fracture of the lateral tibial plateau B Saggittal CT reconstruction images showing

the extent of the fracture C Axial CT images

B

A

C

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4. MR Magnetic resonance creates images of the tissues from the response of the magnetic moments of protons in the body to different magnetic fields. It provides superb soft tissue imaging and is therefore widely used in musculoskeletal radiology. MR can be used to assess bones, muscles, tendons and joints. It also does not involve ionising radiation. Common indications

Shoulder injuries- rotator cuff tears, loose bodies Knee- evaluating meniscal injuries Spine suspected spinal cord compression

-assessing disc disease

5. Nuclear medicine Nuclear medicine is different to other forms of radiology as it involves injecting a radio-isotope intravenously and then the patient is scanned using a gamma-camera which detects the emitted gamma rays from the body and creates an image. The specific radio-isotope used depends on the organ being imaged. In an isotope bone scan the radio-isotope is preferentially taken up by the bony skeleton. Areas of increased activity either due to inflammation, infection or malignancy will appear as focal hot spots. Common indications

Suspected bony metastases (Fig.64) Osteomyelitis Pagets disease (Fig.47)

P F

T M

Me

Figure 11 MR knee Saggittal image of a knee demonstrating the excellent soft tissue detail of MR imaging P patella F femur T tibia M muscles Me meniscus

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FRACTURES Imaging fractures When there is clinical suspicion of a fracture, it is standard practice to obtain at least two views, usually at 900 to each other. Description There is a standard method of describing the radiographic appearance of a fracture, thus allowing consistent reporting and precise communication between radiologists and orthopaedic or trauma specialists. Site

Divide the shaft of long bone into thirds- proximal, middle or distal Use anatomical landmarks for description

Pattern of fracture Simple fracture- no fragments

Describe the direction of the fracture line transverse at 900 to the long axis of bone oblique- at angle less than 900 to long axis of bone spiral curving and twisting along bone

Comminuted fracture more than two fragments Impaction- one fragment is driven into the other

Position/alignment Always expressed in relation to the position of the distal fragment If there is a deformity present you need to describe it under the following headings Displacement - medial, lateral, posterior or anterior Angulation - indicate the direction of tilt of the distal fragment

- medial, lateral, anterior or posterior Rotation - internal or external Distracted/separated fragments

Adjacent joints Normal Intra-articular extension of fracture line Dislocation Subluxation

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Figure 12 Different fracture patterns

Figure 13 spiral and transverse fracture of the tibia

Transverse fracture

Spiral fracture

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Fracture healing A healing fracture undergoes a number of phases, which can be seen on radiographs (Figure 14) Inflammatory phase - torn periosteum

- haemorrhage and clot in fracture line - inflammatory reaction

Reparative phase - granulation tissue replaces clot - callus formation

Remodelling phase - callus is gradually replaced by compact and cancellous bone

A B

Figure 14 A: acute undisplaced fracture of mid tibia

B: fracture healing with callus formation

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Specific fracture types Salter- Harris fracture classification This particular type of fracture occurs through the epiphyseal growth plate and therefore only happens in the paediatric population Salter and Harris have described five different types of epiphyseal fracture (figure 15) Type 1 -fracture is restricted to the growth plate Type 2 -fracture of growth plate involving part of adjacent metaphysis Type 3 -fracture of growth plate involving part of adjacent epiphysis Type 4 -fracture of growth plate involving both metaphysis and epiphysis* Type 5 -impaction fracture of entire growth plate* * Type 4 and 5 are clinically the most important as they can result in premature fusion of the growth plate with consequent limb shortening

Figure 15 Salter-Harris classification of epiphyseal plate fractures Image courtesy of the Medical Journal of Australia

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Figure 16 Grade 2 Salter Harris fracture of proximal phalanx

Figure 19 Grade 5 Salter Harris fracture of distal tibia

Figure 18 Grade 4 Salter Harris fracture of distal tibia

Figure 17 Grade 3 Salter Harris fracture of distal tibia

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Pathological fractures This type of fracture occurs through underlying diseased bone, for example through a bony metastasis. (Figure 20)

Avulsion fractures The fracture fragment is pulled away from bone at the site of a tendon or ligament insertion, commonly at tuberosities. (Figure 21)

Figure 20 Pathological fracture of the mid-shaft of the humerus. Multiple lytic metastases can be seen in the underlying bone.

Figure 21 Avulsion fracture of the medial epicondyle of the humerus

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Some common fractures Upper limb

Figure 22 Scaphoid fracture This is clinically an important fracture because very often the fracture will not be visible on the initial radiograph. If there is a high clinical suspicion of a fracture (e.g. anatomical snuff-box tenderness), a follow-up radiograph should be performed 10-14 days after the injury. If a scaphoid fracture is not diagnosed, avascular necrosis of the bone can occur with longterm sequelae.

Figure 23 Colles fracture Fracture of the distal radius with dorsal angulation. It commonly occurs after a fall on an out-stretched hand. Note that it is important to obtain two radiographic views (AP- anteroposterior, and lateral) in order to fully assess the fracture.

AP wrist radiograph Lateral wrist radiograph

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Figure 24 Bennetts fracture Fracture dislocation of the base of first metacarpal

Figure 25 Boxers fracture Fracture of the fifth metacarpal neck. This type of hand injury usually occurs following a punching incident (e.g. boxing fight).

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Lower limb

Figure 26 radiograph of the pelvis demonstrating a normal left hip and a fracture of the neck of the right femur.

Figure 27 lateral radiograph of the knee showing a comminuted fracture of the patella

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Figure 28 Comminuted fracture of the tibial plateau. There is an associated lipohaemarthrosis of the knee joint which is visible on the lateral radiograph of the knee as a fat-fluid level. When this sign is present, there is always high index of suspicion of an underlying fracture, even if it is not definitely seen. The lipohaemarthrosis is only visible when a horizontal x-ray beam is used for the radiograph. It is therefore vital in the setting of trauma to the knee to perform a horizontal beam lateral view of the joint.

fat

fluid

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Figure 29 trimalleolar ankle fracture This is a complex injury with fractures of the medial, lateral and posterior malleoli. Compare with the normal ankle in figure 30

Figure 30 AP radiograph of a normal ankle. MM medial malleolus LM lateral malleolus TL talus T tibia F fibula

MM LM

TL

T F

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Skull

Figure 31 Depressed skull fracture

Figure 32 Linear skull fracture

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Spine

Cervical spine QUIZ DESCRIBING FRACTURES Cervical spine assessment in the trauma situation

1. Adequate radiographs must be taken in order to assess the cervical spine correctly Lateral radiograph including C1 to the upper aspect of T1 AP radiograph open-mouth or peg view, which is an AP radiograph taken through the patients open mouth to demonstrate the odontoid peg

2. All 7 cervical vertebrae must be entirely visualised. If the entire cervical spine is not adequately visualised, additional views e.g. swimmers view or a CT should be performed

3. Evaluate the vertebral alignment on the lateral radiograph (figure 33), looking

particularly for step-offs. The five lines in figure 33 should be traced out.

1 2 3

4 5

Figure 33 Vertebral alignment 1 pre-vertebral soft tissue 2 anterior spinal line 3 posterior spinal line 4 spinolaminar line 5 spinous process line

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A B

Figure 35 CT of cervical spine Image A- axial CT image of C2 vertebrae showing a fracture through the body of C2 Image B- saggittal reconstruction demonstrating the same fracture in a different plane

Figure 34 Lateral C-spine radiograph of a patient who was involved in a road traffic accident. Check the vertebral alignment. There is a step off in the posterior spinal line between C2 and C3. The patient was also tender in this region on clinical examination and therefore he then had a CT scan of his upper cervical spine (figure 35)

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Lumbar spine

Figure 36 Traumatic compression fracture of a mid lumbar vertebral body.

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Miscellaneous Trauma Shoulder dislocation

Figure 37 Anterior shoulder dislocation This is a Y-view radiograph of the shoulder. The head of the humerus (H) is displaced anterior to the glenoid fossa (G). It is important to always look for associated injuries such as an underlying fracture. Approximately 90% of shoulder dislocations are anterior while only 10% are posterior.

Figure 38 Complications of fractures are important clinically. This radiograph demonstrates a rib fracture (circle) and an associated pneumothorax (arrowheads).

H

G

scapula

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Key points

At least two radiographic views required usually at 900 to eachother Describe fractures under the following headings

-site -pattern of fracture simple/comminuted/impacted

Key points

At least two radiographic views required usually at 900 to each other Describe fractures under the following headings

-site -pattern of fracture simple/comminuted/impacted -position/alignment displacement/angulation -adjacent joints

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METABOLIC BONE DISEASE As we have seen, bone is a dynamic tissue. It is constantly being absorbed and replaced by new bone. The two main cells involved in bone turnover are osteoblasts (forms new bone) and osteoclasts (resorb bone). Therefore a number of different conditions which alter bone metabolism and disturb this equilibrium may result in altered bone structure. These conditions have characteristic radiological appearances which we will review in this section. Excess new bone formation results in osteosclerosis (increased radiodensity) while too little bone formation causes osteopaenia (decreased radiodensity). Osteoporosis In osteoporosis the bone density is reduced. There are many causes, but by far the commonest is primary osteoporosis which occurs in post-menopausal women and in the elderly population. Diagnosis Quantitative measurement of bone density is carried out using a DEXA (dual-energy x-ray absorptiometry) scan. Radiographic features Osteopaenia decreased

radiodensity Decrease in number and thickness of

bony trabeculae Vertebral body compression

fractures - biconcave codfish appearance - true wedge compression

Pathological fractures

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Osteomalacia Abnormal mineralization of bone in adults is called osteomalacia and in children is called rickets. In the past, dietary vitamin D deficiency was the commonest cause however renal disorders are probably more common today. Radiographic appearance

Identical appearance to osteoporosis Loosers zones or pseudofractures (rare)

Cortical stress fractures filled with poorly mineralised osteoid Common sites include scapula, inner margin of femoral neck and in the pelvis

Figure 39 Lumbar spine radiograph showing wedge compression vertebral fractures due to osteoporosis

Figure 40 Loosers zones

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Renal osteodystrophy Patients with chronic renal failure develop a variety of metabolic bone disorders including osteomalacia and secondary hyperparathyroidism, which are grouped under the umbrella term of renal osteodystrophy. Radiographic appearances

1. Osteomalacia- as described before

2. Secondary hyperparathyroidism

Subperiosteal bone resorption Common sites include -radial aspect of middle phalanges of hand -medial aspect of proximal tibia -sacro-iliac joints

Figure 41 Subperiosteal resorption of the radial aspect of the middle phalanges

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Diffuse osteosclerosis - most commonly manifest as rugger-jersey spine

Figure 42 Rugger-jersey spine sclerosis adjacent to the vertebral body endplates

Vertebral body Sclerotic end plate of body Intervertebral disk space

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Browns tumours

- cystic lesions which can appear lytic, expansile and quite aggressive - occur in almost any bone - nearly always associated with sub-periosteal bone resorption

Figure 43 Lytic lesion in proximal right femur in a patient with chronic renal failure

Figure 44 Browns tumour of the proximal tibia

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Pagets disease Pagets disease is a chronic disorder characterised by excessive osteoclastic bone resorption followed by disordered osteoblastic activity resulting in the formation of new bone that is structurally abnormal and weak. Diagnosis Biochemical Radiological Radiographic appearances 1. Plain radiographs

Localised bony expansion most common in the pelvis Osteosclerosis thickening of the cortex Osteolytic changes Bowing of long bones Skull cotton-wool type appearance mixed lytic/sclerotic

- narrowing of neural foramina in the base of skull hearing loss

Figure 45 the right hemi-pelvis is expanded and thickened. The trabecular pattern is more prominent and coarsened. This patient has Pagets disease of the right hemi-pelvis. Compare these changes with the normal pelvis in figure 46.

Figure 46 AP radiograph of a normal pelvis

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2. Radionuclide bone scan Usually hot lesions

Figure 47 Isotope bone scan The entire left humerus is expanded and hot (i.e. increased radio-isotope uptake) when compared to the right humerus. The distal right femur is also hot. This patient has Pagets disease.

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ARTHRITIS Types Degenerative arthritis

-Osteoarthritis

Inflammatory arthritis -Rheumatoid arthritis -Seronegative

spondylarthropathies

Metabolic arthritis -Gout -Calcium pyrophosphate

deposition disease

Miscellaneous -Septic arthritis/osteomyelitis -Neuropathic/Charcots joint

Describing arthritis on radiographs It is important to use a systematic approach when looking at radiographs. Many rheumatological diseases have characteristic radiographic appearances, so through careful review of the radiographs an appropriate differential diagnosis can be obtained. 1. Pattern of Joint involvement -identify the specific joints involved -is the process a mono-arthritis (involving a single joint) or is it polyarthritis (multiple joints affected? -distribution of involved joints- symmetrical (e.g. small joints of both hands are involved) or asymmetrical (e.g. only one knee is affected) 2. Specific joint changes -joint space- is there narrowing? -articular surfaces- are erosions present? -peri-articular changes- e.g. osteoporosis, subchondral sclerosis -new bone formation- e.g. osteophytes -deformity- e.g. swan-neck deformity in rheumatoid arthritis 3. Surrounding structures -soft-tissue swelling 4. Extra-articular features -look for a pleural effusion or the changes of interstitial lung disease or on chest radiograph

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Degenerative Joint Disease - Osteoarthritis Disease is characterised by progressive loss of articular cartilage, which results in

peri-articular bony changes. Not a systemic disorder Two types

Primary OA- due to abnormal mechanical forces on normal joints so-called wear and tear arthritis - age-related Secondary OA - normal mechanical forces on an abnormal joint

- aetiologies trauma -congenital hip dysplasia -haemochromatosis -acromegaly

Joint distribution Hands: distal interphalangeal (DIP) Heberedens nodes proximal interphalangeal (PIP) - Bouchards nodes first carpometacarpal joint Lower limb: hip

knee first metatarsophalangeal (MTP)

Spine: facet joints *Commonly spared joints: metacarpophalangeal (MCP), wrist, elbow, shoulder, ankle Radiographic appearances

Asymmetric joint space narrowing Subchondral sclerosis Subchondral cysts (geodes) Osteophytes Normal soft tissues Localised osteoporosis around joint is not a feature

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Figure 48 Osteoarthritis of the right hip with evidence of geodes, joint space narrowing and subchondral sclerosis. Compare these changes with the normal pelvis in figure 38.

geode

Subchondral sclerosis

Figure 49 Osteoarthritis of both hands. Note the changes (osteophytes, joint space narrowing) predominantly involve the distal interphalangeal joints (DIP) Heberedens nodes (H) and the proximal interphalangeal joints (PIP) - Bouchards nodes (B)

B

H

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Inflammatory arthritis

Rheumatoid arthritis chronic symmetrical polyarthropathy of unknown aetiology systemic disorder females>males disease of the synovium - synovium becomes infiltrated by chronic inflammatory cells

- inflamed synovium then proliferates as pannus, which grows over the articular cartilage and destroys the cartilage and underlying bone, resulting in erosions

Joint distribution Upper limb Hands: MCP joints ulnar deviation Boutonnire deformity- hyperextension of DIP, flexion of PIP Swan-neck deformity- hyperextension of PIP, flexion of DIP Subluxation of carpal bones Shoulder Lower limb Hip Feet

Spine Atlantoaxial subluxation Erosions of odontoid peg

Radiological appearances

Symmetrical joint space narrowing Peri-articular osteoporosis Marginal erosions Subchondral cysts (geodes) Soft tissue swelling Proximal and bilateral symmetric changes in hands

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Figure 50 A, B Rheumatoid arthritis of the hands There are symmetrical bilateral changes involving the metacarpophalangeal and proximal interphalangeal joints. Note the peri-articular erosions (E). On the oblique radiograph the MCP joints are dislocated.

A AP radiograph

B - Oblique radiograph

E

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Extra-articular manifestations It is very easy to focus on the joint abnormalities when assessing patients with rheumatoid arthritis. However it is important not to forget that it is a systemic disorder with many extra-articular features that are visible on radiographs. Chest radiograph Pleural effusion Pulmonary nodules Interstitial fibrosis lower lobes Pericardial effusion Pericarditis

Caplans syndrome -pneumoconiosis,

-RA, -pulmonary nodules

Abdominal imaging (ultrasound/CT) Splenomegaly

Figure 51 Severe Rheumatoid arthritis of the hands Marked destruction and deformity of the MCP joints bilaterally. Note the z deformity of the right thumb

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Seronegative spondylarthropathies This refers to a group of inflammatory arthropathies that are rheumatoid factor negative and are associated with HLA-B27. Ankylosing Spondylitis Disorder primarily of the spine which presents usually with the insidious onset of

lower back pain Males>>> females Onset 15-30 years Radiographic appearances Sacro-iliac joints

-bilateral symmetrical involvement -erosions sclerosis ankylosis/fusion (early) (late)

Spine (thoraco-lumbar)

-loss of lumbar lordosis -vertebral body squaring -syndesmophytes- calcification of outer part of the annulus fibrosus - bamboo spine fusion of the spine and ossification of the spinal ligaments (late feature)

Proximal monoarthritis of large joints hips> shoulder Enthesopathy- inflammation at the sites where a tendon inserts onto bone

-Achilles tendonitis -plantar fasciitis

Extra-articular features Ankylosing spondylitis is a multi-system disorder so some patients will have extra-articular manifestations that may be visible on radiographs. Chest radiographs Pulmonary fibrosis- apical

Abdominal imaging Inflammatory bowel disease

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Figure 52 Ankylosing spondylitis AP and lateral radiographs of the lumbosacral spine, demonstrating ossification of the spinal ligaments and syndesmophytes formation (arrows). There is also fusion of both sacro-iliac joints (arrowheads).

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Enteropathic arthropathies Patients with inflammatory bowel disease (ulcerative colitis or Crohns disease) may develop arthritis. The activity of the arthritis parallels that of the bowel disease. It often mimics ankylosing spondylitis. Bilateral symmetric sacro-ileitis is a feature as is spinal ankylosis as seen in ankylosing spondylitis. Reiters Syndrome Clinical triad:

Urethritis/cervicitis Conjunctivitis Arthritis

Develops following an episode of either nongonococcal urethritis or after gastroenteritis

Radiographic features Distal lower limb predominantly

-erosive arthropathy, often begins in the feet Bilateral sacroilitis

- less common than in ankylosing spondylitis and often asymmetric Enthesopathy plantar fasciitis, calcaneal spur formation Psoriatic arthritis Occurs in approximately 5% of patients with psoriasis In 90% patients the skin changes precede the arthritis Several types of arthritis

-asymmetrical oligoarthritis of small joints of the hand -symmetrical polyarthritis similar to rheumatoid arthritis -arthritis mutilans aggressive form with destruction of small bones of hands/feet -spondyloarthropathy of sacro-iliac joints and spine often asymmetric as opposed to ankylosing spondylitis -polyarthritis predominantly involving DIPs

Radiographic features Predominantly affects the hands Erosions , which can be quite aggressive Soft-tissue swelling of entire digit sausage digit Loss of joint space Pencil-in-cup deformities Resorption of terminal tufts of digits Bone density preserved Sacroilitis

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Figure 54 Psoriatic hands with showing pencil-in-cup deformities (circles)

E

Figure 53 Psoriatic arthropathy with evidence of resorption of the distal tufts of the digits (circle) and peri-articular erosions (E)

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Metabolic arthritis

Key points Describe radiographic changes of arthritis under the following headings Joints -identify the specific joints involved

-mono-arthritis/polyarthritis -joint distribution- symmetrical/asymmetrical

Specific changes -joint space- -articular surfaces -peri-articular changes -new bone formation -deformity Surrounding structures -soft-tissue swelling Extra-articular features

Osteoarthritis Rheumatoid arthritis

Radiological appearance Asymmetric joint space

narrowing Subchondral sclerosis Osteophytes Normal soft tissues Localised osteoporosis

around joint is not a feature

Symmetrical joint space

narrowing Marginal erosions Soft tissue swelling Proximal and bilateral

symmetric changes in hands Peri-articular osteoporosis

Common features Subchondral cysts (geodes)

Joint distribution Weight bearing large joints Hands: DIPs, PIPs

Hands : MCPs,

Not systemic Systemic disorder

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Gout Recurrent episodes of arthritis secondary to the deposition of sodium urate crystals in

and around joints. Causes

-uric acid under excretion e.g. chronic renal failure, drugs (thiazide diuretics) -uric acid overproduction- e.g. chemotherapy, myeloproliferative disorders

Uric acid crystals are bi-refringent under polarised light Radiographic appearances Metatarsophalangeal joint of the hallux is typically involved (podagra) Well defined erosions with sclerotic margins or overhanging edges Joint space is preserved Focal soft-tissue swellings - tophi

Figure 55 Gout There are multiple erosions with overhanging edges (arrowheads) with soft tissue tophus formation (arrow).

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Calcium pyrophosphate deposition disease Disorder of unknown aetiology but is associated with other diseases such as

haemochromatosis, gout and primary hyperparathyroidism Calcium pyrophosphate is deposited in articular cartilage and peri-articular tissues This crystal deposition causes

-chondrocalcinosis- calcification of cartilage -arthropathy caused by calcium pyrophosphate crystals eroding the cartilage and is radiologically similar to osteoarthritis except in its pattern of distribution

The acute symptomatic attacks of synovitis are called pseudogout

Figure 56 Gout Erosions and tophi affecting the joints of the hallux

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Radiographic appearance chondrocalcinosis - hyaline cartilage: knee - fibrocartilage: menisci, glenoid and acetabular labra, symphysis pubis arthropathy similar to osteoarthritis except in pattern of distribution Upper limb Shoulder Elbow radiocarpal joint MCP joints

Lower limb patellofemoral joint of the knee with no involvement of medial/lateral compartments

subchondral cysts

Figure 57 CPPD Chondrocalcinosis of the lateral meniscus (arrowhead).

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Septic arthritis usually due to haematogenous spread to the synovium and the joint Diagnosis is by joint aspiration not radiology Radiographic findings Plain film Joint effusion Juxtaarticular osteoporosis

Bone scan If osteomyelitis is suspected

Osteomyelitis Infection of bone Can occur at any site Radiographic appearance Wide variety of appearances Plain films Periosteal reaction

-thin and linear -thick and ill-defined

Bone destruction -lytic lesion with or without a sclerotic margin -moth-eaten appearance

Bone scan Hot spot MRI Variety of appearances

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Neuropathic or Charcots joint Primary loss of sensation in a joint resulting in arthropathy and joint destruction Joint distribution can be useful in indicating an aetiology

Diabetes mellitus foot Syringomyelia upper limb: shoulder, elbow, wrist Tabes dorsalis (syphilis) lower limb: knee, hip, ankle Myelomeningocele (spina bifida) ankle

Radiographic appearances Joint destruction - severe Dislocation varies in severity Heterotopic new bone- soft tissue calcification adjacent to the joint

Figure 58 This radiograph of the distal foot of a patient with a long history of poorly controlled diabetes mellitus, shows marked destruction of the first and fifth MTP joints. These findings are consistent with neuropathic joints.

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NEOPLASMS

Primary Secondary Multiple Myeloma Osteosarcoma Ewings sarcoma Chondrosarcoma

Metastases

Primary bone tumours Rare Most tumours occur at specific ages Multiple Myeloma Commonest primary bone tumour Malignant clonal proliferation of plasma cells in the bone marrow which produce

monoclonal immunoglobulins (paraproteins) Age > 40 years, peak age of presentation 60 years Radiographic features Multiple well defined lytic lesions Usually involves the axial skeleton

-skull -ribs -spine -pelvis

Radiological diagnosis is based on a skeletal survey - plain radiographs of the entire skeleton

Bone scan will often be normal

Figure 59 Multiple lytic lesions in the skull due to multiple myeloma

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Osteogenic sarcoma Second commonest primary bone tumour Age

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Figures 61&62 Osteosarcoma Sagittal (left) and axial (below) post contrast MRI scans shows the destructive bone lesion with a large soft tissue component (arrowhead) extending to the suprapatellar fat pad and posteriorly towards the neurovascular bundle (arrow). Note the normal left femur, thigh and neurovascular bundle on the axial images. MRI shows the extent of the tumour and is helpful in planning surgery with a view to limb salvage.

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Ewings sarcoma Malignant tumour of undifferentiated mesenchymal cells (primitive neuroectodermal

cells) Age 5-15years Radiological appearances Most commonly occur in diaphysis of lower limb Aggressive tumour Osteolytic lesion with cortical erosion onion-skin type periostitis Associated soft tissue mass Metastases (usually lung) are present in approximately 30% at diagnosis Chondrosarcoma Malignant cartilage producing tumour Majority are low-grade Age >40 years Radiological appearance Lytic destructive mass Snow-flake type calcification Metaphysis of long bones, especially the femur

Figure 63 Chondrosarcoma A destructive partially lytic lesion is seen in the proximal femur.

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Secondary bone tumours Metastases Spread of metastases is usually haematogenous More common than primary bone tumours Variable appearance Pathological fractures are common

Figure 64 Anterior and posterior views of a radionuclide bone scan demonstrating multiple hot spots (black arrows) due to widespread metastases. This patient also has Pagets disease of the right femur (white arrows).

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Aetiology

Radiographic features Lytic metastases

Sclerotic metastases

Breast Prostate Kidney Breast Thyroid Lung Rare Hodgkins disease Carcinoid Neuroblastoma

Adults Male Female

Children

Prostate Breast Neuroblastoma

Lung Lung Leukaemia

Kidney Kidney Lymphoma

Thyroid Thyroid Medulloblastoma

Wilms tumour

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Figure 65 ivory vertebrae sclerotic metastases secondary to prostate cancer in the lumbar vertebral bodies

Figure 66 Sclerotic metastases in the right hemi-pelvis. Compare with the normal pelvis (figure 46).

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Figure 67 Lytic metastasis in the proximal tibia due to renal cell cancer

Figure 68 Axial CT image of the lytic metastasis seen in figure

T

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Key points Metastases are more common than primary bone tumours Malignant tumours and patients age

Age

1-30 years Ewings sarcoma Osteosarcoma

>40 years Metastases Multiple Myeloma Chondrosarcoma

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ACKNOWLEDGEMENTS Images courtesy of M.J.Lee, J.OCallaghan, C.Shortt, K.Abdulla, B.Hogan and S.Looby, Department of Radiology, Beaumont Hospital.