Inflammatory Conditions

G. M. Lingg, C. Schorn, W. Flaig, and U. Laumann

4 Inflammatory Conditions

Infectious Arthritis

Definition and General Pathology

Bacteria-induced articular damage

Hyperemia and proliferation of the synovial membrane with capsular thickening

Exudation with joint effusion and capsular and periarticular edema

Destruction of the synovial membrane, capsule, cartilage, and subchondral bone

Acute Infectious Arthritis

Pathology

Most frequent cause: Local corticosteroid injection with incidental contamination

Rare: Hematogenous spread of an infection (e.g., head-neck infection, dental abscesses)

Very rare: Local spread of an infection following external injuries

Also rare: Hematogenous spread of a prosthetic infection

Clinical Findings

Considerable painful soft-tissue swelling

Erythema and hyperthermia around the joint

Restricted motion

Elevated C-reactive protein and sedimentation rate, leukocytosis

Diagnostic Evaluation

Indications

Diagnosis and follow-up

Findings

Arthritic soft-tissue signs (often subtle):

– Depends on patient’s age, arthritis stage, and causes

– Added soft-tissue density of the joint cavity (effusion and synovial swelling)

– Periarticular edema

– Swelling with homogenization of the juxta-articular soft tissues

– Obliterated fat stripes

Collateral phenomenon:

– Patchy or band-like demineralization of the articulating subchondral bone at about two weeks after, for instance, local corticosteroid injection

Direct arthritic signs:

– Joint-space narrowing caused by infectious pannus with destruction of the cartilage

– Joint-space widening caused by effusion or empyema with capsular distension, especially in the growth period (rare in adults)

– After three to four weeks (without therapy), marginal bone destruction (bare areas) (Fig. 4.2)

– Later also central cystoid bone destruction

– Metaphyseal periosteal reaction

– After commencement of the antibiotic therapy, initially progression of the destruction, first marginally, then centrally

– Removal of debris over months, even if the process has subsided clinically and serologically

Assessment

Initial diagnosis and baseline for follow-up

Normal findings do not exclude the diagnosis of infectious arthritis

An abnormal finding is reasonably specific

Indications

Specific clinical questions

Procuring joint fluid and detection of organism

Diagnosis of rotator-cuff tear

Findings

Inflammatory synovial changes

Assessment

Largely replaced by sonography

(Caution: very operator dependent)

Indications

Suitable for follow-up, especially in children

Aspiration of joint fluid, synovial biopsy, for detection of organism

Diagnosis of rotator-cuff tear

Findings

Detection of effusion/empyema

Absent effusion virtually excludes bacterial infection

Detection of large osseous defects

Rotator-cuff tears and defects (inflammation-induced)

Assessment

More complementary than diagnostic

Suitable to guide the joint aspiration

Indications

Suspected multiple infectious foci

Undetermined location of an infection

Method

Three-phase bone scan

White blood cell (WBC) scan

Findings

Increased juxta-articular uptake in all three phases

In the late phase also increased uptake in the joint fluid

WBC scan superior for soft-tissue foci than for osseous foci

Assessment

Positive for days to weeks before the radiograph becomes positive

Bone scan sensitive but not specific

Goals of Imaging

Differential diagnosis between arthritis, tumor, and trauma

Diagnosis of the type of arthritis

Extent of the arthritis

Localization of the inflammatory process (intra-articularor periarticular, meta-physeal)

Extent of the soft-tissue involvement (subdeltoid, subpectoral, subtrapezoid soft-tissue abscesses along the biceps tendon)

Determination of any osseous involvement and its extent

Determination of the continuity or discontinuity of the rotator cuff

Possibly sonography-guided aspiration to confirm the diagnosis and to identify the causative organisms

Therapeutic Principles

Conservative

Emergency requiring early and aggressive therapy. Inpatient and interdisciplinary therapy! Conservative therapy alone is not sufficient.

Prevention of joint destruction and septic complications

Local cryotherapy, only short period of immobilization, early mobilization therapy

Intravenous antibiotic therapy after culture of the synovial fluid and antibiogram

Empirically until the result of the antibiogram is available, for example, Cefuroxime/Cefotaxime and Flucloxa cillin

Surgical

In the early stage with the rotator cuff still intact and osteomyelitis excluded:

Arthroscopy

Synovectomy

Irrigation and suction drain

Targeted antibiotics

In the late stage with abscess formation, associated osteomyelitis or torn rotator cuff:

Open revision, debridement

Possibly synovectomy

Insertion of PMMA (poly methylmethacrylate) beads

Systemic therapy with targeted antibiotics

Prosthetic infection:

Early stage: Local debridement, synovectomy, PMMA beads, systemic therapy with targeted antibiotics, prosthesis remains in place

Late stage: Revision with exchange of the prosthesis, possibly in two sessions with temporary interim prothesis (increased complication rate, salvage arthrodesis risk-prone)

Indications

Possibly used together with aspiration of effusion/empyema and synovial biopsy for determination of the organism

Delineation of the osseous structures, especially of any glenoid destruction

Suspicion for associated osteomyelitis to exclude any sequesters

Findings

Osseous destruction

Medullary extension (soft-tissue density occupying the marrow space)

Delineation of sequesters

Extension into surrounding soft tissues (intravenous contrast medium)

Assessment

Advisable for cases benefitting from a clear delineation of the extent of osseous destruction

To determine the extent of an advanced process if magnetic resonance imaging (MRI) is contraindicated

Indications

To determine the extent into the surrounding soft tissues and to delineate the articular findings (abscess cavities, fistulous tracts, etc.)

Method

Superficial or shoulder coil

Supine, arm parallel to the body and in neutral position

Sequences:

– Unenhanced paracoronal or axial T1-weighted spin-echo (SE) or gradient-echo (GE) sequence

– Unenhanced paracoronal T2-weighted short time to inversion recovery (STIR) or axial T2-weighted turbo spin-echo (TSE) fast spin (FS) sequence

– Enhanced paracoronal or axial T1-weighted FS sequences

Findings

Effusion:

– T2-weighted image: hyperintense; unenhanced T1-weighted image: hypointense; enhanced fat-suppressed T1-weighted image: no enhancement in the early stage, faint enhancement possible in the late stage (diffusion across inflamed synovia)

– With high proportion of leukocytes/protein: unenhanced T1-weighted image: isointense to hyperintense

Synovitis (Fig. 4.1 a–c):

– Thickened synovial membrane and capsule

– Unenhanced T1-weighted image: intermediate; T2-weighted image: slightly hyperintense or intermediate; enhanced fat-suppressed T1-weighted image: enhancement (bone-marrow edema) (Fig. 4.1 a–c)

Bone-marrow edema:

– Subchondral bone-marrow edema, initially along articular margin, near the capsular insertion

– Later extensive irregular epiphyseal or epimetaphyseal bone-marrow edema (unenhanced T1-weighted image: loss of fat signal; T2-weighted image with fat suppression or STIR: hyperintense; enhanced T1-weighted image: variable enhancement

Cartilage and bone erosions, cystoid destruction (T1-weighted image: intermediate; T2-weighted image: hyperintense; enhanced T1-weighted image: enhancement (Fig. 4.2 d)

Periarticular extension:

– Abscesses, collection of pus (T1-weighted image: intermediate or slightly hyperintense; T2-weighted image: hyperintense; enhanced T1-weighted image: no early enhancement; enhancement in abscess membrane)

– Bursitis (effusion, synovitis)

– Involvement of muscle compartment

– Rotator-cuff lesion

Fig. 4.1 a–c Infectious arthritis

A 63-year-old female patient following several corticosteroid injections into the left shoulder. Afterwards increasing pain and restricted movement. Staphylococcus aureus was found in the aspirated fluid.

a Paracoronal T1-weighted SE image. Moderate joint effusion (arrow) and extensive effusion in the subacromial/subdeltoid bursa (arrowhead) as manifestation of inflammatory exudation. No detectable osseous erosions.

b Paracoronal T1-weighted SE image after administration of contrast medium, showing enhancement of the synovial membrane as manifestation of synovitis (arrows). No detectable osseous erosions.

c T2-weighted STIR image. Extensive joint effusion (arrow) and effusion in the subacromial/subdeltoid bursa (arrowhead). No noteworthy bone-marrow edema. No detectable osseous erosions. Status post rotator-cuff tear.

(Courtesy of Drs. B. Kormeier and K. Schwieren, Department of Radiology, St. Marien-Hospital Borken GmbH)

Fig. 4.2 a–d Infectious arthritis

A 90-year-old male patient with extensive empyema of the shoulder caused by Staphylococcus aureus. Source of infection unknown, most likely hematogenous spread.

a AP radiograph of the right shoulder. Small destructive foci at the upper glenoid margin (arrow).

b Paracoronal fat-saturated proton density-weighted TSE image. Complete destruction of the rotator cuff (arrowhead). Joint effusion. Effusion in the subdeltoid bursa. Bone-marrow edema. Lateral and medial marginal destruction of the humeral head (arrows).

c Axial T1-weighted SE image before administration of contrast medium. Hypointense effusion in the markedly distended subdeltoid bursa. Loss of the bone-marrow signal in the anterior and medial subchondral humeral head with adjacent erosion (arrowhead).

d Axial T1-weighted SE image after administration of contrast medium, same level as in c. Markedly distended subdeltoid bursa with marginal linear enhancement. Furthermore, linear enhancement of the anterior and posterior synovial membrane of the glenohumeral articulation (arrows) and bicipital tendon compartment. Subtle enhancement also adjacent to the humeral erosion.

(Courtesy of Drs. B. Kormeier and K. Schwieren, Department of Radiology, St. Marien-Hospital Borken GmbH)

Assessment

Superior imaging modality with high sensitivity for soft-tissue and bone infection

Not every bone-marrow edema in infectious arthritis corresponds to an accompanying osteomyelitis

Chronic Infectious Arthritis

Tuberculous Arthritis

Pathology

Initial focus in either subchondral bone marrow or synovial membrane (synovial type)

Special case: tuberculous arthritis arising from the subacromial bursa

Clinical Findings

More indolent chronic course

Patients form middle age onward

Mostly monoarticular, shoulder infrequently involved

Diagnostic Evaluation

Indications

Diagnosis and follow-up

Findings

Typical: minimal or no joint-space narrowing

Soft-tissue swelling

Severe demineralization of the juxta-articular bone

Initially marginal, later also large central osseous destruction (developing after several months, often only detectable on cross-sectional image)

Assessment

Normal radiographic finding does not exclude the diagnosis (delayed imaging manifestation)

Only in complex cases (Fig. 4.4a–c)

Fig. 4.3 a–e Rheumatoid arthritis

A 30-year-old female patient with clinical suspicion of rheumatoid arthritis. Differential diagnosis: Septic arthritis of the shoulder.

a AP radiograph of the shoulder. Joint-space narrowing. Subcapital periosteal reaction, extending along the humeral metaphysis (arrow). Destructive changes of the glenoid cavity and humeral head (arrowheads).

b Axial CT. Joint-space narrowing. Flat anteromedial erosion of the humeral head (arrow). Small anteromedial destruction of the glenoid cavity (arrowhead).

c Fat-saturated, proton density-weighted TSE image. Joint effusion in a distended joint cavity with protruding axillary recess and hyperintense intra-articular material (arrow). Patchy humeral and glenoid marrow edema. Major superolateral marginal destruction of the humeral head (arrowhead). Rotator-cuff tear.

d T1-weighted SE image before administration of contrast medium. Cartilage destruction. Loss of the subchondral humeral and glenoid fatty marrow signal, corresponding to areas of bone-marrow edema. Joint cavity and marginal destructive changes are filled with material of medium signal intensity (arrows).

e Axial T1-weighted SE image after administration of contrast medium. Considerable enhancement of the joint cavity and destructive changes, containing in part spherical and in part amorphous tissue structures (arrow). Furthermore, partially linear enhancement of the thickened synovial membrane (arrowhead). Typical manifestation of rheumatoid arthritis. Minimal subchondral enhancement.

(Courtesy of Drs. B. Kormeier and K. Schwieren, Department of Radiology, St. Marien-Hospital Borken GmbH)

Fig. 4.4 a–c Rheumatoid arthritis and concomitant tuberculous arthritis

Male patient with long-standing chronic polyarthritis with involvement of the shoulder, now complaining of increasing pain. Diagnosis confirmed by sonographically guided aspiration of the subdeltoid bursa.

a Sonography. Hypoechoic distension of the subdeltoid bursa containing occasional linear echoes.

b Axial T2-weighted MR image. Visualization of a strongly hyperintense effusion containing less hyperintense areas within the joint capsule and in anteriorly located subchondral bursa.

c Axial fat-suppressed T1-weighted image after administration of Gd-DTPA. The fluid shows low signal intensity and extends anteriorly to the anterior labrum. Large areas within the joint cavity show strong enhancement, corresponding to synovial tissue. It is not possible to differentiate between rheumatoid arthritis and tuberculous arthritis as the underlying cause of the synovitis, but rheumatoid arthritis appears more likely. Moreover, comparison with the T2-weighted image reveals no contrast enhancement anteriorly in the subcoracoid bursa, except for minimal rim enhancement, attributed to caseating granulomas.

(Courtesy of Prof. Dr. K. Bohndorf, Augsburg)

Rheumatoid Arthritis

Pathology

Proliferation of destructive pannus tissue

Frequently early destruction of the ligamentous support with tear of the capsule, rotator cuff, and bicipital tendon

Only later bone destruction: initially small marginal, later mostly deep erosions and cystoid changes in the superolateral aspect of the humeral head next to the major tuberosity

With progression, involvement of the anatomical neck with substantial destruction of the major tuberosity

Loss of joint space due to progressing cartilage destruction

Considerable flattening of the articular surfaces

Pressure erosions of the surgical neck medially due to grating of the inferior margin of the glenoid process

Positive rheumatoid factor test

Clinical Findings

Painful motion restriction, often noticed late due to the tendency of letting the hands rest

Late involvement of the shoulder in “classical” progression of rheumatoid arthritis

Primary manifestation of the gleno-humeral joint in “atypical” rheumatoid arthritis (usually older patients)

Further motion restriction due to rotator-cuff tear, possible subluxation

Accompanying subacromial/subdeltoid bursitis with considerable soft-tissue swelling

Diagnostic Evaluation

Indications

Diagnosis of shoulder involvement and follow-up

Findings (Figs. 4.5–4.8)

Close anatomical-pathological correlation corresponding to the described changes

Soft-tissue signs (appearing late in the shoulder):

– Added soft-tissue density (inflammatory swelling) but also soft-tissue loss (atrophy)

– Uniform appearance of the soft tissues

– Obliteration of the fat stripes, effusion

Collateral arthritic changes:

– Juxta-articular osteoporosis

Direct arthritic changes:

– Progressive joint-space narrowing

– Bone destruction, especially of the superolateral articular surface of the humeral head (Figs. 4.9 c, 4.10), up to the point of mutilation (Fig. 4.12)

– Increasing deformity and flattening of the head and glenoid process

– Pressure erosions on the surgical neck

– Elevation of the humeral head, possible subluxation due to torn rotator cuff, subacromial neoarticulation (Fig. 4.9)

– Secondary osteoarthritis (Fig. 4.10)

– Complicating osteonecrosis of the humeral head (Fig. 4.11)

Assessment

Especially in the shoulder joint, the inflammatory changes involve the ligamentous support structures early, often resulting in the radiographic underestimation of the damage

Indications/Assessment

No longer indicated, superseded by ultrasound (US) and magnetic resonance imaging (MRI)

Findings

Diagnosis of rotator cuff (extra-articular extension of contrast medium into the bursa)

Intra-articular spherical defects corresponding to pannus (Fig. 4.9)

Indications

Evaluation of rotator cuff, bicipital tendon, and bursa

Findings

Effusion, pannus, and orientational search for pannus destruction of the humeral head, especially during follow-up

Tear of the bicipital tendon and rotator cuff, bursitis (Fig. 4.7a, b)

Dynamic assessment of the joint function, possible contralateral comparison

Assessment

To be obtained before other cross-sectional images

Most important method for visualizing rotator cuff, bursa, and bicipital tendon

Indications

Rarely indicated, possibly visualizing the extent of osseous destruction

Findings

Joint effusion

Erosions, destruction (Fig. 4.11)

Assessment

Superior visualization of osseous destruction, especially in 2-D and 3-D reconstruction (Fig. 4.12)

Indications

Possibly assessment for stability and of the rotator cuff if US is inadequate

Investigational: Determining prognosis, monitoring therapy (Fig. 4.8) (so far primarily applied to the hand)

Method

As in infectious arthritis, possibly visualizing the cartilage (T1-weighted GE sequence)

Investigational: Time-activity pattern of enhancement, volumetric assessment of synovitis

Findings

Effusion in joint and bursae (T1 weighting: hypointense; T2 weighting: hyperintense; no early enhancement, possibly faint late enhancement secondary to diffusion across inflamed synovia)

Synovitis:

– Irregular thickening of the synovial membrane (T1 weighting: inter- mediate intensity; T2 weighting: intermediate intensity; enhanced T1 weighting: homogeneously hyperintense)

– Synovial proliferation/pannus of variable extent, possibly filling the entire joint cavity and osseous erosions with spherical soft-tissue lesions (Figs. 4.3 d–f, 4.6) (T1 weighting: intermediate intensity; T2 weighting: hyperintense; enhanced T1 weighting: homogeneous, strong enhancement = active; or T1 weighting: intermediate intensity; T2 weighting: heterogeneous, slightly hyperintense to intermediate hyperintense; enhanced T1 weighting: variable enhancement = less active; or T1 weighting: intermediate intensity; T2 weighting: intermediate intensity; enhanced T1 weighting: no enhancement = fibrous)

Marginal subchondral bone-marrow edema as precursor of osseous erosion (six months to two years before manifested erosions), no correlating radiographic findings (!)