Musculoskeletal Radiology

Mitz

UST Medicine & Surgery Radiology

3C ‘09

Skeletal Scintigraphy - normal

Musculoskeletal Radiology September 27, 2007

Dark areas à normal concentration of Tc will be seen

Essence: “Imaging modality approach” – makes use of several modalities à MULTIMODALITY APPROACH

Pathologic à ↑ activity: à either ↑ turnover or ↑ destruction à see Tc in those areas, abnormal

Main objective: To have a clear/specific choice that can image certain musculoskeletal disease that could yield to a single dx or a significant ddx

conc

Example of a bone scan in w/c the isotopes have preponderance to areas of the bone w/ increase activity such as the ends, since that’s where active bone growth occurs.

3 aspects 1. Imaging Modality - Plain x-ray - Nuclear imaging - CT - MRI 2. Clinical background – Hx & PE of px, particularly of musculoskeletal that is of concern 3. Laboratory data – to r/o or r/i certain disease Modalities X Plain radiograph – makes use of a plain film ▪ PA view ▪ Lateral Oblique ▪ The more views, the better

Computed Tomography Axial images Visualized cortex, marrow, soft tissues, vessels Sensitive for bone destruction Preop evaluation Staging X makes use of x-ray à topographic x-ray that is manipulated by computer X can be viewed on axial, coronal, or sagittal sections X Conventional CT X Helical CT X Multislice CT

cortex medulla

The advantage of CT: X Aside from axial, you will have an excellent visualization of bone itself, as well as cortex and marrow, and surrounding soft tissues, especially during times when contemplating limb salvaging, etc. X Usually used for staging, esp for bone & soft tissue tumors MRI Superior images Multiplanar Useful in joints, tumors, infection, bone infarcts, ischemic necrosis Exquisite marrow visualization

A normal image of knee joint This is a plain x-ray, one can note: Cortex - composed of the compact bone - seen in the periphery and usually seen as a very dense or white area, or strip in the periphery, esp noted from the metaphysic to the shaft of the bone Medulla - composed of cancellous bone/ bone marrow - contains the loose layer of the bone - contains the bone marrow Articular ends – near joint Epiphysis, metaphysic complex – usually seen near the joint Physis Soft tissues – surrounding soft tx, impt to interpret as a whole the bones and the joint that is being examined The cartilaginous plate or growth plate is the one producing osteophytes w/c is received by the metaphysis for promoting bone growth and lengthening Later on, as the individual approaches adulthood, the physis will ultimately fuse w/ the metaphysis and disappear. Skeletal Scintigraphy (“Nuclear Imaging” in plain simple terms) Tc99m / IV – radioisotope usually used - Purpose: settle on the areas of the bone that has ↑ activity Increased bone turnover / destruction – manifest as ↑ activity Normal growth plates *Any pathology may be detected by technetium scan Tumors Infection Fractures Arthritis Periostitis

ü show the same images ü have time in reformatting the images so you can see cross sections of different views

§ § § § § §

High field magnet coupled w/ radiofrequency Show excellently the soft tissues as well as bone marrow Bone is not paramagnetic à no signal on MRI, appear as black Signal → produced by bone marrow Any problem in bone itself à show changes in bone marrow That’s why in MR, if there is any changes in bone marrow, you can readily diagnosed that there is a bone problem even if it doesn’t have any signal on MR § Mainstay: evaluation of the joint (any joint in the human body) à better evaluated by MR § Joint pathology à MRI is the imaging modality of choice! (esp in sports injury, post traumatic injury) ü Although plain film or CT can be used to image joints ü May skip other imaging modalities

Ultrasound Visualize soft tissue & bony cortex Adjunctive procedure Useful in evaluating tendons, joints, soft tissues Narrow FOV (Field of View), segmental visualization or organ of interest Operator dependent

Very sensitive / less specific – still search for a cause amm

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Mitz

UST Medicine & Surgery Radiology

3C ‘09

▫ Occult œa fracture that is not seen on plain radiograph œPx has pain despite no fracture on plain film œw/ symptom but no finding œnext choice to dx à bone scintigraphy or nuclear imaging

Knee joint with prosthesis « use sound wave → doesn’t penetrate the bone, doesn’t image the bone « sound wave doesn’t penetrate through bone & prosthesis « just shows the prosthesis at the area of examination « Limited by size of the probe (only about 3-4 inches) à size of the image is limited (Narrow FOV) « For large/small tendon esp. digits, joints, soft tissue Contents: ☼ Trauma ☼ Tumors ☼ Infections ☼ Joint Disorders Traumatic bone injuries ♦ Fractures - General rule, plain radiograph is always indicated even at the slightest doubt of fracture or trauma - any discontinuity or deformity of the bone - especially in resilient bones of pediatric patients, in trauma, it will not literally break, but will be deformed…so it is still a fracture

¯ Occult fracture on the carpal bone

N – uniform uptake of Tc

ABN Concentrated Tc uptake

▫ Bone bruise œintracanalicular injury in the intracanalicular haversian portion of the cortex œUsually reflected in Bone marrow as a low intensity focus œIf there is a low signal area, coupled with hx of fracture in that area, consider a bone bruise œUsually dx by MR œCan’t be dx by CT or plain film

♦ Types of Fracture ▫ Complete © Transverse © Oblique © Spiral

low intensity focus BM

▫ Comminuted œmore than 2 fragments œbased on shape of 3rd fragment ü Butterfly – triangular ü Segmental – rectangular

Oblique fracture w/ angulation

▫ Incomplete © Greenstick – break on one side of cortex deformities © Buckle (torus) – secondary to twisting or buckling © Plastic – bending

greenstick fracture (ulna)

œDistal fracture of tibia œComminuted butterfly injury

▫ Avulsion / chip fracture œusually occurs in areas of the bones that are sites of either muscular or tendon attachment œjust a small fracture œbut may affect function of muscle or tendon (moderately or severely)

at the area of the greater tuberosity of the humerus

amm

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Mitz

UST Medicine & Surgery Radiology

3C ‘09

▫ Epiphyseal fractures ♥ Classify by Salter-Harris classification (1960) ♥ Pedia – epiphyseal line seen ♥ Normal ?

,Non union (or non-healing of the fracture) - Factors ü ↑ Age à less calcium à more osteoporotic bone ü Infection ü Vascular injury ü Improper fixation - Salient features (X-ray Findings) ü No callus bridging across fracture line ü Motion in stress radiographs ü Or formation of a pseudojoint (pseudoarthrosis)

Bone tumors

Type I Type II Type III Type IV Type V

limited to the entire epiphyseal line Epiphyseal line + portion of metaphysis (most common) Epiphyseal line + portion of epiphysis Epiphyseal line + epiphysis-metaphysic complex Modification of type 1 where injury is limited to one side of epiphyseal line, sparing the other side

Type I / V – significant if it involves a functioning joint – ex. ankle joint The injured portion of bone will not continue growing → affect joint function ▫ Pathologic ♥ usually secondary through an existing bone pathology - Bone tumor - Malignancy - Osteomyelitis - Multiple Myeloma ♥ existing bone pathology produces weakening of the cortex, producing injury ▫ Stress ♥ usually subjected to chronic stress ü Calcaneus ü Ribs ü Hips ♥ To demonstrate it → skeletal scintigraphy – note ↑activity in that area

Dense area at hips Healing "also monitored by plain film "Gauged by: evident visualization of CALLUS formation "Callus formation: ,Occurs in two stages ü 1st stage – not visualized radiographically ü 2nd stage – after 2-3 weeks from the time of injury, visualized radiographically, so follow up is done @ 2-3 weeks after injury ,If radiograph is done early, no evidence of callous formation "Types ,Union - Clinical – precedes radiographic evidence - Radiographic – appear 2/n 2 wks

Main goal: identify whether • Primary - relatively rare as compared to metastatic tumors • Metastatic – malignant - several organs gives metastatic process e.g. breast thyroid lung kidney prostate DDx – may mimic bone tumors, always think of these 3 • Infection • Metabolic • Dysplastic

Cortex Borders Soft tissues

Benign Intact Well defined No involvement

Malignant Disrupted Poorly defined With involvement

¤ Classification - based on cell origin, e.g. osteoid, cartilaginous, fibrous, myelogenous, metastatic, cystic ~Cartilaginous – usually occur near the joint • Osteochondroma - benign - coat hanger deformity - characterized by a cartilaginous cap → not usually seen in plain x ray but can be defined by CT - usually grows near the joint → bec of the muscular and tendon pull direction - Exostosis near the joint – in the metaphysic - Cortex is intact • Chondrosarcoma - malignant - disrupted cortex - ill defined borders - soft tissue involucrum ~Osseous • Osteoma - usually seen in the sinuses particularly frontal sinus - appears as sharply marginate lobulated dense mass - often times may block ostium passages of the sinuses → produce sinusitis • Osteosarcoma - calcifications extend in soft tissues, and margins of lesions are very much irregular, some soft of ill defined lesions - char as sunburst periosteal reaction w/ dense osteoed poorly defined cortical destruction and expansion - MRI show evidence of marrow replacement indicative of tumor infiltration - dense osteoid gives typical low signal - medullary cortices destroyed When you do limb salvaging procedures, CT or MRI done, take note that bone marrow, reflects lesion in bone→ the lesion extend well beyond the plain field... in this case, beyond the midshaft of the femur (middle image)

ü produce bridging of fractured fragments ü Signs of bone remodelling

- noted if there's bridging of callus bet fractured fragments - And disappearance of fracture line indicating endosteal callus

T2 shows high signal intensity mass bowing the quadriceps muscle Low signal intensity in the soft tissue mass also represents osteoid amm

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Mitz

UST Medicine & Surgery Radiology

3C ‘09

~Cystic • Simple bone cyst - benign - small, rounded, well defined, dark area on the bone itself • Giant Cell Tumor - premalignant (only about 2-3% go to malignancy) - expansile with septations - In the metaphysic of bone - Althought the margins are not that irregular, but you see some sort of cortical break, but it is still a benign lesion ~Myelogenous – tumors originating from bone marrow • Multiple myeloma – classic - presentation: punch out lytic lesions on the skull and long bones - always malignant - Lesions may coalesce when numerous - in contrast to histiocytosis x LS disease in w/c lesions don’t coalesce - whenever you tend to place MM in ddx, r/i or r/o MM by doing skull xray - almost always à skull is involved

æAcute osteomyelitis Ÿ Latent period = 10 to 12 days (will not be seen on film) Ÿ On this period, the best modality of choice would be nuclear medicine Ÿ Beyond latent period → plain film → see bone destruction Ÿ (in latent period) Pain, soft tissue swelling, etc æChronic osteomyelitis Ÿ Thickened cortex Ÿ Wavy outline Ÿ Obliterated medullary portion Ÿ Attempt of bone to seal of infection: ü Sequestrum – dark areas surrounding bone ü Involucrum

Joint abnormalities Periarticular bony structures – bone surrounding the joint space Joint space Soft tissues ~Metastastic - common site: vertebra (pedicles) - can either be lytic or blastic ü lytic – bone destruction ü blastic – bone formation - do also scintigraphy, in which conc of Tc can be seen with ↑ or ↓ bone destruction etc - in a single px, consider 4 organs: ü breast ü prostate ü lung ü renal ü thyroid

X Radiographic signs of Joint disease Abnormality in apposing bony margins Changes in width of joint space – most important • Narrowed – cartilage is destroyed • Widened – ↑ amount of synovial fluid in the joint space Subluxation Periarticular swelling – of soft tissues Infectious arthritis X Acute X Chronic X 2° to S. aureus or TB

Infections …Osteomyelitis áStaph aureus ~Routes Hematogenous Implantation Secondary ~There is a difference in vascular supply in children & adults áEarly lesions in pedia, start in metaphysis áEarly lesions in adult, start in epiphysis § Bec. Of the vascular supply § You should not consider infection if epiphysis is clear (adult) & vice versa

normal joint

widened joint (↑ synovial fluid in area)

narrowed joint → expect cartilaginous destruction already

Tuberculous arthritis X Hallmark: RAT BITE DEFORMITY on the sides X Or the periarticular bony structures X Pott’s disease → usually affect BODY of the vertebra

amm

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Mitz

UST Medicine & Surgery Radiology

3C ‘09

TB spondylitis X blood supply from the spine emanates from end plates X Spare disse space X That’s why there is… ü Destruction ü Anterior wedging ü Gibbus deformity X Rarely, TB will first involve entire vertebral body X Almost always affect the intervertebral disc X paravertebral abscess form

Degenerative joint disease ü Affects distal joint ü Weight bearing joint …secondary to wear and tear of joint (chronic) …Not inflammatory …In contrast to RA, the joint space is ASSYMETRICALLY narrowed Neuropathic arthropathies § Hallmark: Fragmented, disorganized joints (compared to other side) †Leprosy †Tabes dorsalis †Diabetes Metabolic § Gout → 1st MTP ü Uric acid crystal deposits ü Pseudoarthropathy - Findings of bone will be seen after a long period of clinical symptoms, about 6 years or more, before there could be abn findings in bone - Px w/ ssx of gout for 2 years → no expected findings on x-ray - If joint space is intact → No cartilaginous destruction - Erosions on sides / periarticular margins - Classic finding of uric acid deposition in the tissues

Rheumatoid arthritis X Affects proximal joints of hand X Symmetrical – bilateral X Proximal Interphalangeal joints & carpal bones X Salient findings: ü Osteoporosis of periarticular bony structures ü Producing early synovial fluid tension and erosion

L → 1st metatarsointerphalangeal joint R → Ultrasound showing calcification of uric acid crystal deposits

Ann Mitzel Mata Fred Monteverde Cecil Ong

Erosion on radial side because of small joint capsule on radial side producing tension & fluid

X Can affect other portions: ü Hip joints – symmetrically narrowed ü Atlanto-axial joint – sublax Rheumatoid variants X Ankylosing spondylitis - Maybe RF (-) - Usually male in predominance - About 25-30 younger age group - Start centrally à that’s why central type of RA - Usually affects spine and sacroiliac joint - Bamboo spine deformity - Calcification of anterior and posterior spinal ligaments amm

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