Osteomyelitis and Infectious Arthritis. Gelow, 2/04 - OHSU Home

Osteomyelitis Osteomyelitis and and

Infectious ArthritisInfectious Arthritis

Jill GelowJill Gelow

Radiology Elective Radiology Elective

February, 2004February, 2004

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Osteomyelitis Osteomyelitis

Common clinical problemCommon clinical problem Defined as a progressive infection of the Defined as a progressive infection of the

bone that results in inflammatory destruction bone that results in inflammatory destruction of the bone, bone necrosis and new bone of the bone, bone necrosis and new bone formationformation

Classification by pathogenesis and Classification by pathogenesis and chronicitychronicity

Early diagnosis is difficultEarly diagnosis is difficult Delay in diagnosis leads to decreased cure Delay in diagnosis leads to decreased cure

rates and increased rates of complication and rates and increased rates of complication and morbiditymorbidity

Classification of OsteomyelitisClassification of Osteomyelitis

PathogenesisPathogenesis» Hematogenous (most common cause in kids)Hematogenous (most common cause in kids)

In children: tubular bonesIn children: tubular bones In adults: spine, pelvis and small bonesIn adults: spine, pelvis and small bones

» Spread from adjacent soft tissue infectionSpread from adjacent soft tissue infection Ex: decubitus ulcers, diabetic foot ulcersEx: decubitus ulcers, diabetic foot ulcers

» Direct inoculationDirect inoculation Ex: Trauma or surgeryEx: Trauma or surgery

ChronicityChronicity» AcuteAcute» SubacuteSubacute» ChronicChronic

Progression to subacute or chronic disease depends on timing of dx and tx, comorbid conditions, immune status etc.

Acute OsteoAcute Osteo Sub-Acute OsteoSub-Acute Osteo Chronic OsteoChronic OsteoBegins with marrow Begins with marrow edema, cellular infiltration edema, cellular infiltration and vascular engorgementand vascular engorgement

May progress to necrosis May progress to necrosis and abscess formationand abscess formation

Spread within the Spread within the intramedullary cavity intramedullary cavity extension through cortex extension through cortex by Havers and Volkman’s by Havers and Volkman’s canals canals subperiosteal subperiosteal space space periosteum periosteum soft tissues soft tissues

Rupture of joint space Rupture of joint space septic arthritisseptic arthritis

Occurs in abnormal bone Occurs in abnormal bone or after inadequate or after inadequate antibioticsantibiotics

Localized pyogenic Localized pyogenic processprocess

Commonly appears as a Commonly appears as a well-defined osteolytic well-defined osteolytic metaphyseal lesion metaphyseal lesion (Brodie’s abscess) with a (Brodie’s abscess) with a sclerotic margin that fades sclerotic margin that fades peripherally (fuzzy peripherally (fuzzy sclerotic margin)sclerotic margin)

S. aureus is most common S. aureus is most common pathogenpathogen

Occurs after inadequate tx or in Occurs after inadequate tx or in pts with altered immunitypts with altered immunity

Distinguishing feature is Distinguishing feature is necrotic bone surrounded by necrotic bone surrounded by granulation tissuegranulation tissue

Interruption of blood supply Interruption of blood supply necrosis necrosis devitalized bone devitalized bone fragments (sequestra)fragments (sequestra)

A thick sheath of new periosteal A thick sheath of new periosteal bone can develop around the bone can develop around the sequestra (involucrum)sequestra (involucrum)

Fistula tract formation Fistula tract formation

Sharp interface between normal Sharp interface between normal and diseased marrowand diseased marrow

Imaging of OsteomyelitisImaging of OsteomyelitisConventional RadiographyConventional Radiography

CTCT

MRIMRI

Nuclear Medicine StudiesNuclear Medicine Studies

UltrasoundUltrasoundClick Here to

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Conventional RadiographyConventional Radiography Modality of choice for initial evaluationModality of choice for initial evaluation

AdvantagesAdvantages InexpensiveInexpensive Exclude other conditionsExclude other conditions May help guide further work-upMay help guide further work-up

DisadvantagesDisadvantages Often normal for the first 10 to 21 days of infectionOften normal for the first 10 to 21 days of infection Sensitivity: 43-75%Sensitivity: 43-75% Specificity: 75-83%Specificity: 75-83%

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Conventional Radiograph FindingsConventional Radiograph Findings

Earliest finding Earliest finding deep soft tissue swelling deep soft tissue swelling Active infection for 1-2 weeks Active infection for 1-2 weeks bone destruction bone destruction

and periosteal reactionand periosteal reaction

Localized osteoporosis Localized osteoporosis

Pathologic fracturePathologic fracture

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Click the ‘i’ to learn about periosteal reaction

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http://www.rad.washington.edu/mskbook/periostealreaction.html

Plain Film of Osteomyelitis Plain Film of Osteomyelitis

Plain radiograph of the tibia and fibula in a 14 y/o patient demonstrating a pathologic fracture of the proximal fibula with periosteal reaction and erosion of the cortical bone secondary to subacute osteomyelitis

CT ImagingCT Imaging

Not part of routine work-up Not part of routine work-up use limited use limited to specific circumstancesto specific circumstances

Used to evaluate areas with focal exam Used to evaluate areas with focal exam findings and negative plane filmsfindings and negative plane films

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CT of OsteomyelitisCT of Osteomyelitis

Chronic osteomyelitis of the tibia in a 57 y/o man. ‘A’ and ‘B’ are axial CT’s of the tibia-fibula showing hypertrophic expanded new bone (involucrum( around

the central dead bones (sequestra). Note the cortical break anteriorly at the fistula tract (cloaca).

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CT Imaging ContinuedCT Imaging Continued

Advantages:Advantages: Best method to detect small foci of intraosseous gas, areas Best method to detect small foci of intraosseous gas, areas

of cortical erosion or destruction, tiny foreign bodies, of cortical erosion or destruction, tiny foreign bodies, involucrum and sequestration formationinvolucrum and sequestration formation

Good for evaluation of chronic osteomyelitis: cortical Good for evaluation of chronic osteomyelitis: cortical thickening, sclerosis, fistula drainingthickening, sclerosis, fistula draining

Good for identifying abnormalities that must be fixed at Good for identifying abnormalities that must be fixed at surgery (sequestra, involucra, fistula)surgery (sequestra, involucra, fistula)

Can be used to guide aspirations and bone biopsiesCan be used to guide aspirations and bone biopsies

DisadvantagesDisadvantages Sensitivity and specificity not clearly establishedSensitivity and specificity not clearly established Lower sensitivity than MRILower sensitivity than MRI Limited assessment of bony parts with metalic implants Limited assessment of bony parts with metalic implants

due to beam hardening artifactdue to beam hardening artifactClick

MRI ImagingMRI Imaging Widely used for the evaluation of

osteomyelitis

Generally uses: T1 and T2 weighted images STIR or fat-saturated spin echo T2 weighted sequences

(STIR is more sensitive but less specific for dx osteomyelitis than spin echo)

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MRI ContinuedMRI Continued AdvantagesAdvantages

Extremely sensitive in the early detection of osteomyelitisExtremely sensitive in the early detection of osteomyelitis– Provides excellent contrast between abnormal and normal Provides excellent contrast between abnormal and normal

bone marrowbone marrow– Sensitivity reported to be between 82% to 100%Sensitivity reported to be between 82% to 100%– Specificity reported between 75% to 96%Specificity reported between 75% to 96%– Compared to CT, improved soft-tissue contrast resolution, Compared to CT, improved soft-tissue contrast resolution,

no beam hardening effect and multiplanar abilityno beam hardening effect and multiplanar ability

DisadvantagesDisadvantages CostCost Bone marrow findings of osteomyelitis on MRI are nonspecific. Bone marrow findings of osteomyelitis on MRI are nonspecific.

Interpretation often based on clinical setting.Interpretation often based on clinical setting.– Similar findings can be seen in bone contusion, Similar findings can be seen in bone contusion,

osteonecrosis, metastasis and other noninfectious osteonecrosis, metastasis and other noninfectious inflammatory and metabolic conditions of boneinflammatory and metabolic conditions of bone

Can be difficult to differentiate healed osteo from active diseaseCan be difficult to differentiate healed osteo from active disease

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Acute MRI FindingsAcute MRI Findings Marrow abnormalitiesMarrow abnormalities

– T1 ImagesT1 Images Edema and exudates in the medullary space produce an ill- Edema and exudates in the medullary space produce an ill-

defined low signal intensitydefined low signal intensity

– T2 Images, STIR, fat suppressed sequencesT2 Images, STIR, fat suppressed sequences T1 low signal intensity areas change to high signal intensityT1 low signal intensity areas change to high signal intensity

– Ill-defined interface between normal & abnormal Ill-defined interface between normal & abnormal marrowmarrow

Surrounding soft tissuesSurrounding soft tissues Abnormal with ill-defined planesAbnormal with ill-defined planes

CortexCortex– No thickening No thickening – Subperiosteal fluid collectionsSubperiosteal fluid collections

Low signal intensity on T1Low signal intensity on T1 Intermediate to high signal on T2 and fat-suppressedIntermediate to high signal on T2 and fat-suppressed

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MRI of Acute OsteomyelitisMRI of Acute Osteomyelitis

15 y/o with knee pain and acute osteomyelitis. Coronal T1 image shows low signal intensity in the proximal epiphysis extending through the growth plate into the metaphysis of the tibia.

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Subacute MRI FindingsSubacute MRI Findings

Brodie’s abscess Brodie’s abscess – ((intraosseous abscess, internal wall covered by granulation tissue)intraosseous abscess, internal wall covered by granulation tissue)

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16 y/o with Brodie’s abscess. T1 weighted image of the knee (A) demonstrates the double line effect, a focal area of low signal with alternating bands of high and low signal. Axial T2 weighted image of the proximal tibia at the same level (B) demonstrates a region of high-intensity surrounded by alternating bands of low signal and high signal.

Subacute osteo is often confused Subacute osteo is often confused with tumor (osteosarcoma, Ewing)with tumor (osteosarcoma, Ewing)

Chronic MRI FindingsChronic MRI Findings In both subacute and chronic osteomyelitis, a In both subacute and chronic osteomyelitis, a

peripheral area of low-signal intensity (the rim peripheral area of low-signal intensity (the rim sign) on all pulse sequences is visualized. sign) on all pulse sequences is visualized. Corresponds to fibrous change or reactive bones.Corresponds to fibrous change or reactive bones.

Reported in 93% of patients with chronic osteomyelitis and in less Reported in 93% of patients with chronic osteomyelitis and in less than 1% of patients with acute.than 1% of patients with acute.

Usual appearance of high T2 signal in marrow may Usual appearance of high T2 signal in marrow may be absent. Instead, there are areas of be absent. Instead, there are areas of devascularized fibrotic scaring which are low devascularized fibrotic scaring which are low intensity signal onT1 and T2 images.intensity signal onT1 and T2 images.

Predominant bone sclerosis with cortical thickening Predominant bone sclerosis with cortical thickening Sinus tracts, sequestra, soft tissue abscessesSinus tracts, sequestra, soft tissue abscesses Sharp interface between normal and abnormal Sharp interface between normal and abnormal

marrowmarrow Click Here

Sensitivity and Specificity of MRI in OsteomyelitisSensitivity and Specificity of MRI in Osteomyelitis**Adapted from Restrepo et al, 2003Adapted from Restrepo et al, 2003

ReferenceReference Sensitivity%Sensitivity% Specificity%Specificity% LocationLocation

Modic, 1986Modic, 1986 9696 9292 SpineSpine

Unger,1988Unger,1988 9292 9696 MultipleMultiple

Yuh, 1989Yuh, 1989 100100 8989 FootFoot

Wang, 1990Wang, 1990 9999 8181 FootFoot

Erdman, 1991Erdman, 1991 9898 7575 MultipleMultiple

Zynamon,1991Zynamon,1991 100100 7878 FootFoot

Weinstein,1993Weinstein,1993 100100 8989 MultipleMultiple

Morrison, 1995Morrison, 1995 8282 8080 FootFoot

Mazur, 1995Mazur, 1995 9797 9292 MultipleMultiple

Morrison,1998Morrison,1998 84-9684-96 78-8878-88 FootFoot

Haung, 1998Haung, 1998 9898 8989 Hips/PelvisHips/Pelvis

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Three types of study are predominantly used:Three types of study are predominantly used: Bone ScanBone Scan Gallium ScanGallium Scan White Blood Cell ScanWhite Blood Cell Scan

General AdvantagesGeneral Advantages Can image patients with prostheses without interferenceCan image patients with prostheses without interference Easier for pediatric patients (pts usually don’t need sedation)Easier for pediatric patients (pts usually don’t need sedation) Multiple foci of disease can be demonstratedMultiple foci of disease can be demonstrated Sensitivity and Specificity similar to MRISensitivity and Specificity similar to MRI

General DisadvantagesGeneral Disadvantages Limited spatial resolutionLimited spatial resolution Less ability to delineate complex anatomyLess ability to delineate complex anatomy Circulatory compromise can interfere with studyCirculatory compromise can interfere with study

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Bone ScanBone Scan 3-phase bone scan performed after injection of methylene 3-phase bone scan performed after injection of methylene

diphosphonate (MDP)diphosphonate (MDP) Immediate, 15 minute and 3-4 hour images are obtained.Immediate, 15 minute and 3-4 hour images are obtained. Abnormal findings for osteo include:Abnormal findings for osteo include:

Increased flow activityIncreased flow activity Blood pool activityBlood pool activity Positive uptake on 3 hour imagesPositive uptake on 3 hour images

High sensitivity for osteomyelitisHigh sensitivity for osteomyelitis Sensitivity 73 to 100%Sensitivity 73 to 100%

Specificity for osteo decreases when other conditions are Specificity for osteo decreases when other conditions are simultaneously present simultaneously present recent trauma, surgery or diabetes recent trauma, surgery or diabetes

Specificity: 73% to 79% but as low as 38% with complicating Specificity: 73% to 79% but as low as 38% with complicating conditionsconditions

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Bone Scan Image

Bone Scan ImageBone Scan Image

Patient with a history of puncture wound at the base of the thumb. Plain radiograph (A) of the hand is normal. Three phase bone scan (B–D) demonstrates increased flow of radiotracer to the soft tissues and increased uptake in the bone consistent with osteomyelitis involving the base of the first metacarpal bone.

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Gallium ScanGallium Scan

Imaging preformed 24 to 48 hours after Imaging preformed 24 to 48 hours after injection of Galliuminjection of Gallium

Relatively high sensitivityRelatively high sensitivity Sensitivity: 25% to 80%Sensitivity: 25% to 80%

Specificity similar to bone scanSpecificity similar to bone scan Occasional false positives from fractures, tumor uptakeOccasional false positives from fractures, tumor uptake Specificity: 67%Specificity: 67%

Image quality may not be as good as the Image quality may not be as good as the bone scan and it takes longerbone scan and it takes longer

Marked excretion through the GI tractMarked excretion through the GI tract

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White Blood Cell ScanWhite Blood Cell Scan Indium –labeled WBC or HMPAO-labeled WBCIndium –labeled WBC or HMPAO-labeled WBC Accumulation at sites of inflammationAccumulation at sites of inflammation Compared to HMPAO, the Indium-labeled has:Compared to HMPAO, the Indium-labeled has:

Higher radiation dose to ptHigher radiation dose to pt Takes 24 hours to performTakes 24 hours to perform Images with extensive noiseImages with extensive noise Sensitivity of 90%, Specificity of 78%Sensitivity of 90%, Specificity of 78%

Compared to Indium, the HMPAO-labeled has:Compared to Indium, the HMPAO-labeled has: Lower radiation dose to ptLower radiation dose to pt Same day study and resultSame day study and result Better image qualityBetter image quality Similar sensitivity and specificitySimilar sensitivity and specificity

Both types are superior to bone scan when imaging patients Both types are superior to bone scan when imaging patients with complicating conditionswith complicating conditions

Specificity increases to 80% to 90%Specificity increases to 80% to 90%

Difficult to distinguish between acute, chronic or partially Difficult to distinguish between acute, chronic or partially tx infectiontx infection

Image

Increased Specificity with WBC Scan Increased Specificity with WBC Scan Compared to Bone ScanCompared to Bone Scan

Patient with a history of trauma and possible osteomyelitis at the level of the right ankle. Bone scan (A) demonstrates increased uptake in the posterior calcaneus. White blood cell scan (B) is normal and excludes the possibility of osteomyelitis. The increased uptake on the bone scan could be explained from prior trauma.

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UltrasoundUltrasound Role in diagnosis of osteomyelitis is limitedRole in diagnosis of osteomyelitis is limited

Most useful for identifying fluid in joint or Most useful for identifying fluid in joint or extra-articular soft tissueextra-articular soft tissue

US findings consistent with osteomyelitis:US findings consistent with osteomyelitis: Fluid collection adjacent to bone without intervening soft Fluid collection adjacent to bone without intervening soft

tissuetissue Elevation of periosteum by more than 2 mmElevation of periosteum by more than 2 mm Thickening of the periosteumThickening of the periosteum

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Osteomyelitis in HIV/AIDSOsteomyelitis in HIV/AIDS

S. aureus is the most common pathogen S. aureus is the most common pathogen both in the general population and in both in the general population and in immunocompromised hostsimmunocompromised hosts

Pts with HIV are at increased risk for less Pts with HIV are at increased risk for less common organismscommon organisms

Including: Salmonella, Nocardia asteroides, gonococcus, Mycobacteria Including: Salmonella, Nocardia asteroides, gonococcus, Mycobacteria tuberculosis, Torulopsis glabrata, cryptococcus, candida, tuberculosis, Torulopsis glabrata, cryptococcus, candida, cytomegaloviruscytomegalovirus

Osteomyelitis SummaryOsteomyelitis Summary Diagnosis of acute osteomyelitis is challenging.Diagnosis of acute osteomyelitis is challenging.

Acute, subacute and chronic osteomyelitis can Acute, subacute and chronic osteomyelitis can often be distinguished through imaging.often be distinguished through imaging.

Diagnosis can be made with plain radiograph, Diagnosis can be made with plain radiograph, MRI or nuclear medicine study.MRI or nuclear medicine study.

CT and ultrasound may be useful adjuvant CT and ultrasound may be useful adjuvant imaging modalities.imaging modalities.

Infectious ArthritisInfectious Arthritis

Infectious arthritis can generally be divided into two Infectious arthritis can generally be divided into two categories:categories:

– Pyogenic or septic arthritisPyogenic or septic arthritis

Most commonly caused by Most commonly caused by Staphylococcus aureus, Neisseria gonorrhea, Klebsiella pneumoniae, Candida albicans, and Serratia marcescens

– Non-pyogenic arthritis

Most commonly caused by tuberculosis or fungal infections including actinomycosis, cryptococcosis, actinomycosis, cryptococcosis, coccidioidomycosis,histoplasmosis, and sporotrichosiscoccidioidomycosis,histoplasmosis, and sporotrichosis

Pathogenesis of Pathogenesis of Infectious ArthritisInfectious Arthritis

Infectious agents can enter the joint space in several Infectious agents can enter the joint space in several waysways

– Direct invasion of the synovial membraneDirect invasion of the synovial membrane Penetrating woundPenetrating wound Post-surgical following joint replacementPost-surgical following joint replacement

– Infection of adjacent soft tissueInfection of adjacent soft tissue

– Hematogenous spread from a blood borne infectionHematogenous spread from a blood borne infection

– Spread from a focus of osteomyelitis in adjacent boneSpread from a focus of osteomyelitis in adjacent bone

Imaging of Infectious ArthritisImaging of Infectious Arthritis

Conventional RadiographyConventional Radiography

ArthrographyArthrography

UltrasoundUltrasound


CTCT

MRIMRI

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Conventional Radiography for Conventional Radiography for Infectious ArthritisInfectious Arthritis

Modality of choice for initial evaluation of Modality of choice for initial evaluation of suspected joint infectionssuspected joint infections

Diagnosis can be made when characteristic findings are presentDiagnosis can be made when characteristic findings are present

Early plain film findings:Early plain film findings: Periarticular osteoporosisPeriarticular osteoporosis Soft tissue swellingSoft tissue swelling Joint effusionJoint effusion Joint space lossJoint space loss

Later plain film findings:Later plain film findings: Periosteal reactionPeriosteal reaction Marginal and central erosions and destruction of subchondral boneMarginal and central erosions and destruction of subchondral bone Subluxation or dislocationSubluxation or dislocation Intra-articular bony ankylosisIntra-articular bony ankylosis

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Conventional Radiography Conventional Radiography ContinuedContinued

Gas formation within the joint capsule can be Gas formation within the joint capsule can be seen with infection by:seen with infection by:

E coli, Serratia, Clostridium perfringensE coli, Serratia, Clostridium perfringens

In patients with hip or knee joint In patients with hip or knee joint arthroplasties the infected joint reveals:arthroplasties the infected joint reveals:

Joint fluidJoint fluid Loosening of the prosthesis componentsLoosening of the prosthesis components Bone erosion around the prosthesisBone erosion around the prosthesis

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Plain Film of Septic ArthritisPlain Film of Septic ArthritisA: AP film shows erosion around tibial component and loosening of the prosthesis. Note also osteolytic changes at lateral and medial femoral condyles. B: Lateral shows fullness of suprapatellar bursa caused by large joint fluid. Note lucencies and bone resorptions around femoral and tibial components. Examination of the aspirated fluid revealed Staphylococcus aureus.

57-year-old man with cellulitis and septic arthritis of the metatarsophalangeal joint of the fifth toe. Note destruction of the joint and gas formation in the soft tissues. The aspiration biopsy revealed Clostridium perfringens.

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ArthrographyArthrography Used only in conjunction with joint aspirationUsed only in conjunction with joint aspiration Joint aspiration is the most effective procedure for Joint aspiration is the most effective procedure for

diagnosis of infectious arthritisdiagnosis of infectious arthritis Provides synovial fluid for diagnosisProvides synovial fluid for diagnosis Relieves joint pressure cause by accumulation of fluid/ pusRelieves joint pressure cause by accumulation of fluid/ pus

Injection of contrast into the joint confirms needle Injection of contrast into the joint confirms needle placementplacement

Radiographs obtained after contrast may reveal:Radiographs obtained after contrast may reveal: Destruction of the articular cartilageDestruction of the articular cartilage Hypertrophic alterations to the synoviumHypertrophic alterations to the synovium Irregular or contracted joint capsule in chronic infectionIrregular or contracted joint capsule in chronic infection


Arthrography ImageArthrography Image

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A 53-year-old man with infectious arthritis of the right hip joint. A: A radiograph demonstrates narrowing of the joint and articular erosions. B: An arthrogram was performed mainly to obtain fluid for bacteriologic examination, which revealed Staphylococcus aureus. The imaging study shows destruction of articular cartilage and hypertrophic changes of the synovium.

Ultrasound for Infectious Ultrasound for Infectious ArthritisArthritis

Alone, US is unable to confirm the Alone, US is unable to confirm the diagnosis of septic arthritisdiagnosis of septic arthritis

However, US is a very sensitive modality However, US is a very sensitive modality for demonstrating joint effusionfor demonstrating joint effusion

May be effective in guiding needle May be effective in guiding needle aspiration of jointaspiration of joint

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Nuclear Medicine Studies for Nuclear Medicine Studies for Infectious ArthritisInfectious Arthritis

Most rapid method for determination of the site Most rapid method for determination of the site and distribution of joint infectionand distribution of joint infection

Scintigraphy studies are sensitive indicators of Scintigraphy studies are sensitive indicators of altered osteoblastic activityaltered osteoblastic activity

Limited by:Limited by: Poor specificity Poor specificity Inability to accurately delineate complex anatomyInability to accurately delineate complex anatomy Local disturbances in vascular perfusion, clearance rate, Local disturbances in vascular perfusion, clearance rate,

permeability and chemical bindingpermeability and chemical binding

3- or 4- phase bone scan with T99m MDP is the 3- or 4- phase bone scan with T99m MDP is the most commonly used nuc med study most commonly used nuc med study

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Bone Scan for Infectious ArthritisBone Scan for Infectious Arthritis

3-phase T99 MDP Bone Scan findings3-phase T99 MDP Bone Scan findings

– Increased blood flow adjacent to the jointIncreased blood flow adjacent to the joint– Prominent activity on blood pool images on both sides Prominent activity on blood pool images on both sides

of the affected areaof the affected area

A fourth phase (delayed 24 hour imaging) shows:A fourth phase (delayed 24 hour imaging) shows:

– Diminution of activityDiminution of activity– This is in contrast to osteomyelitis which invariably has This is in contrast to osteomyelitis which invariably has

increased activity on delayed imagesincreased activity on delayed images


Bone Scan ImageBone Scan Image Click Here

Tc99m-MDP bone scan including blood pool image (upper left corner) and 4-hour delay images (lower and upper right corner) shows markedly increased uptake of radionuclide tracer at interphalangeal joint with osteomyelitis of proximal and distal phalanges of the left great toe. RT = right; LT = left; HR = hour.

CT for Infectious ArthritisCT for Infectious Arthritis Not standard for evaluation of joint infections but Not standard for evaluation of joint infections but

can be used to guide complex joint aspirationscan be used to guide complex joint aspirations When used, CT findings include:When used, CT findings include:

Water density fluid in the joint space and associated irregularity and Water density fluid in the joint space and associated irregularity and narrowing of the jointnarrowing of the joint

Soft tissue swellingSoft tissue swelling Articular erosion and subchondral bone destructionArticular erosion and subchondral bone destruction

Effective in dx early infectious arthritis:Effective in dx early infectious arthritis: Synovial thickeningSynovial thickening Small joint effusionSmall joint effusion

Can identify air bubbles in infections caused by gas Can identify air bubbles in infections caused by gas forming organismsforming organisms

Caution b/c air bubbles can also represent a degenerative process in Caution b/c air bubbles can also represent a degenerative process in SI and facet joints and are also common after hip dislocationSI and facet joints and are also common after hip dislocation

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MRI for Infectious ArthritisMRI for Infectious Arthritis

Not commonly used for imaging suspected septic Not commonly used for imaging suspected septic arthritis as dx can readily be confirmed with less arthritis as dx can readily be confirmed with less expensive modalitiesexpensive modalities

Advantages:Advantages: Extremely sensitive for detection of infectious arthritis Extremely sensitive for detection of infectious arthritis More specific for infectious arthritis than conventional More specific for infectious arthritis than conventional

radiography or CTradiography or CT Can provide images in any placeCan provide images in any place

DisadvantagesDisadvantages ExpensiveExpensive Not needed to establish diagnosisNot needed to establish diagnosis

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MR Findings in Infectious ArthritisMR Findings in Infectious Arthritis Early Stages of Infection:Early Stages of Infection:

T2 images reveal distention of joint capsule by nonspecific high-T2 images reveal distention of joint capsule by nonspecific high-intensity fluidintensity fluid

Later Stages of Infection:Later Stages of Infection:

Can detect joint effusion, cartilage destruction, narrowing of joint Can detect joint effusion, cartilage destruction, narrowing of joint and cellulitis around jointand cellulitis around joint

MRI can readily detect extension of the infectious process into MRI can readily detect extension of the infectious process into adjacent bone marrow and the transition to osteomyelitisadjacent bone marrow and the transition to osteomyelitis

T2 images reveal infected fluid and blood in the joint of T2 images reveal infected fluid and blood in the joint of inhomogeneous intermediate signal intensity inhomogeneous intermediate signal intensity

T2 images also reveal an area of signal hyperintensity in the soft T2 images also reveal an area of signal hyperintensity in the soft tissue around the affected jointtissue around the affected joint

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Infectious Arthritis in HIV/AIDSInfectious Arthritis in HIV/AIDS Relatively uncommon in the HIV populationRelatively uncommon in the HIV population

Most frequently seen in IVDU or hemophiliacsMost frequently seen in IVDU or hemophiliacs

Most common pathogens include:Most common pathogens include:– S aureus, Neisseria gonorrhoeae, M tuberculosis and Candida S aureus, Neisseria gonorrhoeae, M tuberculosis and Candida

albicansalbicans

Clinical presentation in most often monoarticular with Clinical presentation in most often monoarticular with the hip joint most commonly affectedthe hip joint most commonly affected– The sternoclavicular and sacroiliacs are also commonly The sternoclavicular and sacroiliacs are also commonly

involved in IVDUinvolved in IVDU

Infectious Arthritis SummaryInfectious Arthritis Summary

Conventional radiography and joint aspiration are Conventional radiography and joint aspiration are the mainstays of infectious arthritis diagnosisthe mainstays of infectious arthritis diagnosis

Arthrography and less commonly CT or Arthrography and less commonly CT or Ultrasound may play a role in guiding joint Ultrasound may play a role in guiding joint aspirationaspiration

MRI has little role in the dx of infection arthritis MRI has little role in the dx of infection arthritis but may be used to evaluate for complications, but may be used to evaluate for complications, particularly osteomyelitisparticularly osteomyelitis

Case ExampleCase Example

42-year-old Male with 42-year-old Male with

AIDS and Right Groin PainAIDS and Right Groin Pain

Chief ComplaintChief Complaint

Right groin/hip pain for one-Right groin/hip pain for one-monthmonth

Increasing right thigh Increasing right thigh “weakness”“weakness”

History of Present IllnessHistory of Present Illness R groin pain x 1 month PTA R groin pain x 1 month PTA

Progressively worsened, resulting in subjective R Progressively worsened, resulting in subjective R thigh weakness and recent confinement to bed thigh weakness and recent confinement to bed

Associated R thigh swelling. No redness, induration Associated R thigh swelling. No redness, induration or rash.or rash.

No hx of traumaNo hx of trauma

ROS neg except for intermittent N/V and weight ROS neg except for intermittent N/V and weight loss (not quantified)loss (not quantified)

HPI Continued…HPI Continued… ER visit 3 weeks PTA for right groin/hip ER visit 3 weeks PTA for right groin/hip

pain and swellingpain and swelling

Pt afebrile, VSS. PE was noted to reveal mild swelling of Pt afebrile, VSS. PE was noted to reveal mild swelling of R posterior thigh with no erythema or rashR posterior thigh with no erythema or rash

Labs showed WBC of 4.2 and ESR of 109Labs showed WBC of 4.2 and ESR of 109

US of R thigh showed nonocclusive right popliteal DVTUS of R thigh showed nonocclusive right popliteal DVT

Sx attributed to DVT Sx attributed to DVT Rx Warfarin Rx Warfarin

Past Medical HistoryPast Medical History

HIV; dx 18 years agoHIV; dx 18 years ago Hep C (prior Hep A and B)Hep C (prior Hep A and B) Espohageal candidasis; fluconazole resistantEspohageal candidasis; fluconazole resistant

Tx with IV caspofunginTx with IV caspofungin Pt with PICC at time of admission, placed ~ 6 wks PTAPt with PICC at time of admission, placed ~ 6 wks PTA

Cutaneous T-Cell LymphomaCutaneous T-Cell Lymphoma Adrenal InsufficiencyAdrenal Insufficiency Non-occlusive popliteal DVT, as aboveNon-occlusive popliteal DVT, as above Hx IVDUHx IVDU

MedicationsMedications

AntiretroviralsAntiretrovirals Azithromyin: 1200 mg po q weekAzithromyin: 1200 mg po q week Dapsone: 100mg po q dDapsone: 100mg po q d Prednisone: 5 po q am, 25 po q qhPrednisone: 5 po q am, 25 po q qh Florinef: 0.1 mg po q dFlorinef: 0.1 mg po q d Methadone: 20 mg po TIDMethadone: 20 mg po TID Propranolol: 20 mg po BIDPropranolol: 20 mg po BID Doxepin: 100 mg po q hsDoxepin: 100 mg po q hs Neurontin: 900 mg po TID, prnNeurontin: 900 mg po TID, prn WarfarinWarfarin

Physical ExaminationPhysical Examination

Afebrile, VSSAfebrile, VSS No focal neurological deficitsNo focal neurological deficits Exam of right groin and hip tender with Exam of right groin and hip tender with

limited range of motion secondary to pain limited range of motion secondary to pain but otherwise unremarkablebut otherwise unremarkable

What is included in your What is included in your differential dx of right groin/hip differential dx of right groin/hip

pain in this pt with AIDS?pain in this pt with AIDS?

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Evaluation of R Groin Pain in 42 y/o Evaluation of R Groin Pain in 42 y/o Male with AIDS and PICCMale with AIDS and PICC

CBC, Chem 7, INRCBC, Chem 7, INR

ESRESR

X-Ray Right Hip X-Ray Right Hip

X-Ray PelvisX-Ray Pelvis

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Results

Differential DiagnosisDifferential Diagnosis Most LikelyMost Likely

– Infection- osteomyelitis, pyomyositis, septic arthritisInfection- osteomyelitis, pyomyositis, septic arthritis Opportunistic infections including TB/FungalOpportunistic infections including TB/Fungal Catheter related infection due to indwelling PICCCatheter related infection due to indwelling PICC

Less LikelyLess Likely– NeurologicNeurologic

AIDS related neuropathy or radiculopathyAIDS related neuropathy or radiculopathy

– VascularVascular Recurrent DVTRecurrent DVT

– RheumatologicRheumatologic Non-infectious arthritisNon-infectious arthritisinflammatory, crystal deposition, DJDinflammatory, crystal deposition, DJD

– TraumaTrauma Hip/pelvic fxHip/pelvic fx

– MalignancyMalignancy Primary or metastatic lesion of R hip +/- pathologic fracturePrimary or metastatic lesion of R hip +/- pathologic fracture

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CBC, Chem 7, INRCBC, Chem 7, INR

5.89.0

24.5117

MCV: 98.1

PMN: 79

Mono: 10

Lymph: 7

Eos: 1

INR: 1.82

129

4.4

100

26

9.0

0.876

Ca: 8.0

Mg: 2.0

Phos: 3.2


ESRESR

Admit Labs: 111Admit Labs: 111 ED visit 3 weeks PTA: 109ED visit 3 weeks PTA: 109



This plain film is classic for septic arthritis. Further imaging is not necessary for the diagnosis. However, other imaging modalities can be used to guide aspiration and evaluate the extent of the presumed associated osteomyelitis.

Report: Report: Right Hip and Pelvis X-RayRight Hip and Pelvis X-Ray

FINDINGS: “There is almost complete loss of the right hip FINDINGS: “There is almost complete loss of the right hip joint space diffusely. There is a broad loss in definition of joint space diffusely. There is a broad loss in definition of the subchondral bone plate of both the femoral head and the subchondral bone plate of both the femoral head and acetabulum with moderate periarticular osteoporosis. acetabulum with moderate periarticular osteoporosis. There is no fragmentation or fracture. There are no soft There is no fragmentation or fracture. There are no soft tissue gas collections. Other than the periarticular tissue gas collections. Other than the periarticular abnormalities, there is not any frank bone destruction.” abnormalities, there is not any frank bone destruction.”

IMPRESSION: “Radiographic findings of the right hip are IMPRESSION: “Radiographic findings of the right hip are consistent with septic arthritis. Joint aspiration is consistent with septic arthritis. Joint aspiration is recommended.”recommended.”


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Based on the Imaging Results….Based on the Imaging Results….

The right hip joint was aspirated under The right hip joint was aspirated under fluoroscopic guidancefluoroscopic guidance

Images

Synovial Fluid Analysis Click Here After Viewing

Results

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Report: Right Hip Aspiration Report: Right Hip Aspiration with Fluoroscopic Guidancewith Fluoroscopic Guidance

PROCEDURE: “The overlying site was prepped and draped PROCEDURE: “The overlying site was prepped and draped in a sterile fashion and infiltrated with 1% xylocaine local in a sterile fashion and infiltrated with 1% xylocaine local anesthetic. A 22-gauge needle was advanced into the joint. anesthetic. A 22-gauge needle was advanced into the joint. There was very thick hemarthrosis. Approximately 3.5 cc There was very thick hemarthrosis. Approximately 3.5 cc of fluid was aspirated. The right hip joint was irrigated of fluid was aspirated. The right hip joint was irrigated with 20 cc of sterile saline with no return. After irrigation with 20 cc of sterile saline with no return. After irrigation with an additional 10 cc a return of almost 18 cc of the with an additional 10 cc a return of almost 18 cc of the irrigant was obtained which was mixed with blood. There irrigant was obtained which was mixed with blood. There was no gross purulence. Intra-articular position was was no gross purulence. Intra-articular position was confirmed by a small test injection of approximately 3 cc confirmed by a small test injection of approximately 3 cc of Hypaque-60.”of Hypaque-60.”

IMPRESSION: “Distended joint with hemarthrosis and IMPRESSION: “Distended joint with hemarthrosis and radiographic findings consistent with septic arthritis.”radiographic findings consistent with septic arthritis.”

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Synovial Fluid AnalysisSynovial Fluid Analysis Cell Count Cell Count

WBC: 15,889WBC: 15,889

– PMN: 95 PMN: 95

– Lymph: 3Lymph: 3

– Mono: 2Mono: 2

– Macrophage: 1Macrophage: 1 RBC: 265,556RBC: 265,556

Gram StainGram Stain 4+ WBC4+ WBC 2+ Gram Positive Cocci2+ Gram Positive Cocci

CultureCulture Methacillin Sensitive Staph AureusMethacillin Sensitive Staph Aureus

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An MRI of the Pelvis was An MRI of the Pelvis was Obtained to Further Evaluate for Obtained to Further Evaluate for

OsteomyelitisOsteomyelitis

Select MRI Images

MRI Report

Click Here to Continue Caveat

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Coronal Stir Image of Pelvis

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Axial

Mid TE

Coronal

T1

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Report: MRI PelvisReport: MRI PelvisFINDINGS: “There is marked abnormality of the right hip with severe right hip FINDINGS: “There is marked abnormality of the right hip with severe right hip

joint space narrowing, ill definition of the subchondral bone plate of the right joint space narrowing, ill definition of the subchondral bone plate of the right femoral head and of the acetabulum. Extensive signal abnormality is noted femoral head and of the acetabulum. Extensive signal abnormality is noted within the right acetabulum, right femoral head and neck which is within the right acetabulum, right femoral head and neck which is heterogeneously low signal intensity on the T1-weighted images and heterogeneously low signal intensity on the T1-weighted images and heterogeneously high-signal intensity on the mid-TE fat-suppressed images heterogeneously high-signal intensity on the mid-TE fat-suppressed images and STIR images. These abnormal signal intensity foci enhance intensely and STIR images. These abnormal signal intensity foci enhance intensely with contrast and are most consistent with osteomyelitis of the right with contrast and are most consistent with osteomyelitis of the right acetabulum and right femoral head and neck, in the setting of septic arthritis. acetabulum and right femoral head and neck, in the setting of septic arthritis. In addition, a large joint effusion is noted at the right hip which appears In addition, a large joint effusion is noted at the right hip which appears loculated and there is also thick enhancement at the margin of the hip joint, loculated and there is also thick enhancement at the margin of the hip joint, indicating synovitis, an expected finding with septic arthritis. Extensive signal indicating synovitis, an expected finding with septic arthritis. Extensive signal abnormality, comprising low signal intensity on the T1-weighted images and abnormality, comprising low signal intensity on the T1-weighted images and increased signal intensity on the fluid-sensitive sequences are seen within the increased signal intensity on the fluid-sensitive sequences are seen within the right gluteus minimus, right obturator internus and externus and right right gluteus minimus, right obturator internus and externus and right piriformis. Abnormal signal intensity is also noted within the right gluteus piriformis. Abnormal signal intensity is also noted within the right gluteus

maximus and within the right adductor muscles.”maximus and within the right adductor muscles.”

CaveatCaveat

Obtaining an MRI at this time will not Obtaining an MRI at this time will not likely change this patient’s initial treatment likely change this patient’s initial treatment plan.plan.

Septic Arthritis was confirmed by plain film Septic Arthritis was confirmed by plain film and joint aspiration and the pt is presumed and joint aspiration and the pt is presumed to have osteomyelitis.to have osteomyelitis.

MRI can help determine chronicity of MRI can help determine chronicity of disease and extent of disease.disease and extent of disease.

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DiagnosisDiagnosis

Based on the above findings a diagnosis of Based on the above findings a diagnosis of MSSA osteomyelitis and associated septic MSSA osteomyelitis and associated septic arthritis was madearthritis was made

What was the likely source of the infection?


Source of Infection?Source of Infection?

Most LikelyMost Likely– Continued IVDUContinued IVDU

Less LikelyLess Likely– PICC line infection seeding hipPICC line infection seeding hip

Blood Culture from PICC did grow Blood Culture from PICC did grow MSSAMSSA

Culture of PICC tip also grew MSSACulture of PICC tip also grew MSSA


Treatment PlanTreatment Plan

Developed in consultation with orthopedics and Developed in consultation with orthopedics and infectious diseaseinfectious disease

PICC removedPICC removed

Six weeks IV nafcillin (new PICC placed prior to d/c)Six weeks IV nafcillin (new PICC placed prior to d/c)

F/u in six weeksF/u in six weeks

If no evidence of continued infection proceed to If no evidence of continued infection proceed to total hip arthroplastytotal hip arthroplasty

ReferencesReferences

Bureau NJ, Cardinal E. Imaging of musculoskelatal and spinal Bureau NJ, Cardinal E. Imaging of musculoskelatal and spinal infections in AIDS. Rad Clin NA. 2001; 39infections in AIDS. Rad Clin NA. 2001; 39

Greenspan A, Tehranzadeh J. Imaging of musculoskelatal and soft Greenspan A, Tehranzadeh J. Imaging of musculoskelatal and soft tissue infections: Imaging of infectious arthritis. Rad Clin N Am. 2001; tissue infections: Imaging of infectious arthritis. Rad Clin N Am. 2001; 39.39.

Karchevsky M, Schweitzer ME, Morrison WB, Parellada JA. MRI Karchevsky M, Schweitzer ME, Morrison WB, Parellada JA. MRI findings of septic arthritis and associated osteomyelitis in adults. AJR. findings of septic arthritis and associated osteomyelitis in adults. AJR. 2004; 182: 119-122.2004; 182: 119-122.

May DA, Disler D, Jones EA, Balkissoon AA, Manaster BJ. Abnormal May DA, Disler D, Jones EA, Balkissoon AA, Manaster BJ. Abnormal signal intensity in sjkelatal muscle at MR imaging: Patterns, pearls, and signal intensity in sjkelatal muscle at MR imaging: Patterns, pearls, and pitfalls.Radiographics. 2000; 20: S295-315.pitfalls.Radiographics. 2000; 20: S295-315.

Restrepo CS, Gimenez CR, McCarthy KM. Imaging of osteomyelitis Restrepo CS, Gimenez CR, McCarthy KM. Imaging of osteomyelitis and musculoskelatal soft tissue infections: Current concepts. Rhem Dis and musculoskelatal soft tissue infections: Current concepts. Rhem Dis Clin NA. 2003; 29Clin NA. 2003; 29

Tehranzadeh J, Wong E, Wang F, Sadighpour M. Imaging of Tehranzadeh J, Wong E, Wang F, Sadighpour M. Imaging of Osteomyelitis in the mature skeleton. Rad Clin NA. 2001; 39Osteomyelitis in the mature skeleton. Rad Clin NA. 2001; 39

Ghiorzi T, Mackowiak P. Diagnosis of osteomyelitis. UptoDate. 2004.Ghiorzi T, Mackowiak P. Diagnosis of osteomyelitis. UptoDate. 2004.

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