musculoskeletal radiology

UST Medicine & Surgery MitzRadiology 3C ‘09

amm 1 of 5

cortex

medulla

ü show the same images ü have time in reformatting the images so

you can see cross sections of different views

Musculoskeletal RadiologySeptember 27, 2007

Essence:“Imaging modality approach” – makes use of several modalities à MULTI-MODALITY APPROACH

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

3 aspects1. 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

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 jointEpiphysis, metaphysic complex – usually seen near the jointPhysisSoft tissues – surrounding soft tx, impt to interpret as a whole thebones 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 ↑ activityNormal growth plates

*Any pathology may be detected by technetium scanTumorsInfectionFracturesArthritisPeriostitis

Very sensitive / less specific – still search for a cause

Skeletal Scintigraphy - normal

Dark areasà normal concentration of Tc will be seen

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

Computed TomographyAxial imagesVisualized cortex,marrow, soft tissues, vesselsSensitive for bone destructionPreop evaluationStaging

X makes use of x-ray à topographic x-ray that is manipulated by computerX can be viewed on axial, coronal, or sagittal sections

X Conventional CTX Helical CTX Multislice CT

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

MRISuperior imagesMultiplanarUseful in joints, tumors, infection, bone infarcts, ischemic necrosisExquisite marrow visualization

♣ High field magnet coupled w/ radiofrequency♣ Show excellently the soft tissues as well as bone marrow♣ Bone is not paramagneticà 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

UltrasoundVisualize soft tissue & bony cortexAdjunctive procedureUseful in evaluating tendons, joints, soft tissuesNarrow FOV (Field of View), segmental visualization or organ of interestOperator dependent


amm 2 of 5

Oblique fracture w/ angulation

deformities

greenstick fracture (ulna)

N – uniform uptake of Tc

ABN -Concentrated

Tc uptake

¯ Occult fracture on the carpal bone

low intensity focus BM

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

♦ Types of Fracture▫ Complete

© Transverse©Oblique © Spiral

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

▫ Occult �a fracture that is not seen on plain radiograph�Px has pain despite no fracture on plain film�w/ symptom but no finding�next choice to dx à bone scintigraphy or nuclear imaging

▫ Bone bruise � intracanalicular injury in the intracanalicular haversian

portion of the cortex�Usually reflected in Bone marrow as a low intensity focus�If there is a low signal area, coupled with hx of fracture in

that area, consider a bone bruise�Usually dx by MR�Can’t be dx by CT or plain film

▫ Comminuted �more than 2 fragments�based on shape of 3rd fragment

ü Butterfly – triangularü Segmental – rectangular

�Distal fracture of tibia�Comminuted butterfly

injury

▫ Avulsion / chip fracture �usually occurs in areas of the bones that are sites of either

muscular or tendon attachment� just a small fracture�but may affect function of muscle or tendon (moderately or

severely)

at the area of the greater tuberosity of thehumerus


amm 3 of 5

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

Type I limited to the entire epiphyseal lineType II Epiphyseal line + portion of metaphysis (most common)Type III Epiphyseal line + portion of epiphysisType IV Epiphyseal line + epiphysis-metaphysic complexType V 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 jointThe 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 Calcaneusü Ribsü 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 stagesü 1st stage – not visualized radiographicallyü 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

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

callus

,Non union (or non-healing of the fracture)- Factors

ü ↑ Age à less calcium à more osteoporotic boneü Infectionü Vascular injuryü Improper fixation

- Salient features (X-ray Findings)ü No callus bridging across fracture lineü Motion in stress radiographsü Or formation of a pseudojoint (pseudoarthrosis)

Bone tumors

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

Benign MalignantCortex Intact DisruptedBorders Well defined Poorly definedSoft tissues No involvement 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)

T2 shows high signal intensity mass bowing the quadriceps muscleLow signal intensity in the soft tissue mass also represents osteoid

ü produce bridging of fractured fragments

ü Signs of bone remodelling


amm 4 of 5

narrowed joint → expect cartilaginous destruction already

~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 alwaysà skull is involved

~Metastastic- common site: vertebra (pedicles)- can either be lytic or blastic

ü lytic – bone destructionü 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 prostateü lungü renalü thyroid

Infections

�OsteomyelitisáStaph aureus

~RoutesHematogenousImplantationSecondary

~There is a difference in vascular supply in children & adultsáEarly lesions in pedia, start in metaphysisáEarly lesions in adult, start in epiphysis

§ Bec. Of the vascular supply§ You should not consider infection if epiphysis is clear

(adult) & vice versa

æAcute osteomyelitis� Latent period = 10 to 12 days (will not be seen on film)� On this period, the best modality of choice would be

nuclear medicine� Beyond latent period → plain film → see bone destruction� (in latent period) Pain, soft tissue swelling, etc

æChronic osteomyelitis� Thickened cortex� Wavy outline� Obliterated medullary portion� Attempt of bone to seal of infection:

ü Sequestrum – dark areas surrounding boneü Involucrum

Joint abnormalitiesPeriarticular bony structures – bone surrounding the joint spaceJoint spaceSoft tissues

X Radiographic signs of Joint diseaseAbnormality in apposing bony marginsChanges in width of joint space – most important

• Narrowed – cartilage is destroyed• Widened – ↑ amount of synovial fluid in the joint space

SubluxationPeriarticular swelling – of soft tissues

Infectious arthritisX AcuteX ChronicX 2° to S. aureus or TB

normal joint widened joint (↑ synovial fluid in area)

Tuberculous arthritisX Hallmark: RAT BITE DEFORMITY on the sidesX Or the periarticular bony structuresX Pott’s disease → usually affect BODY of the vertebra


amm 5 of 5

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

TB spondylitisX blood supply from the spine emanates from end platesX Spare disse spaceX That’s why there is…

ü Destructionü Anterior wedging ü Gibbus deformity

X Rarely, TB will first involve entire vertebral bodyX Almost always affect the intervertebral discX paravertebral abscess form

Rheumatoid arthritisX Affects proximal joints of handX Symmetrical – bilateralX Proximal Interphalangeal joints & carpal bonesX Salient findings:

ü Osteoporosis of periarticular bony structures ü Producing early synovial fluid tension and erosion

X Can affect other portions:ü Hip joints – symmetrically narrowedü Atlanto-axial joint – sublax

Rheumatoid variantsX 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

Degenerative joint diseaseü Affects distal jointü 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 depositsü 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

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

Ann Mitzel MataFred Monteverde

Cecil Ong

musculoskeletal radiology

Documents