Infectious Disease of Bone

Jeffrey R. Thompson, D.C. DACBRAssoc. Prof. Diag. ImagingTexas Chiropractic College

General concepts• Osteomyelitis = infection of bone• Septic Arthritis = specifically involves joint• Pyogenic and granulomatous infectious agents

both may occur• Staphylococcus is most common agent

– Others include strep, tuberculosis, brucella, coccoidiomycosis, syphilis.

• Mechanism of infection typically hematogenous– Direct extension from soft tissue or direct

implantation from puncture wound or surgery

Acute Pyogenic Osteomyelitis• Etiology: most common is staphylococcus• Age: most common age infant – 12 yrs• Clincal- child

– Elevated WBC with 80% PMN’s– Fever, chills– Local pain, swelling

• Clinical- adult– Often chronic before detection

• WBC count and fever not as dramatic until later

– More common to involve joints in adults than children

Bone infection - imaging• Plain film– Significant “latent” period = no

change!– Appendicular skeleton 7-10 days– Spine 2 – 4 weeks!– Negative plain film does not rule out infection!

• Radionuclide bone scan– Technetium most (often used)– Gallium citrate– Indium (esp. for soft tissue infection)

• MR very sensitive to bone and/or soft tissue changes

Bone infection – x-ray

• Metaphyseal area typically first area involved– Sluggish blood flow and “end” arterioles present

• Soft tissue swelling and blurring of fascial plane lines early (difficult to detect)

• Permeative or motheaten bone destruction– chronic bone abscess geographic

• Reactive sclerosis of adjacent bone common• Periosteal reaction typically parallel

– More periostitis in children than adult– Laminated pattern may develop more chronically

Osteomyelitis• In the child, infection

will typically not cross the physeal plate

• Periostitis is marked• Involucrum = shell of

periosteal new bone around infected bone

• Sequestrum = island of (dead) bone surrounded by infected bone Unremarkable AP shoulder.

Two weeks later….

Acute osteomyelitis• Note sparing of epiphysis despite extensive involvement of

metaphysis and shaft

Acute osteomyelitis• Earliest plain film finding is soft

tissue swelling (June 28) 2 weeks later (Aug 11)

Acute osteomyelitis• Parallel periostitis and permeative

bone destruction Progression

Acute osteomyelitis• Parallel periostitis and permeative

bone destruction With treatment

Chronic Osteomyelitis• Characterized by prominent reactive sclerosis

superimposed on evidence of bone destruction.• Irregular cortical outline and “bone expansion”

common due to chronic periostitis/new bone formation.

• Brodies Abscess = A localized focus of chronic bone infection.– May mimic osteoid osteoma both clinically and

radiographically, although the nidus may be bigger.– Geographic lucency with reactive sclerosis.

Chronic Osteomyelitis of Garre• Osteomyelitis characterized by dense sclerosis/hypertrophic

change and little to no destruction = Garre’s Osteomyelitis

Chronic Osteomyelitis

• Areas of isolated bone abscess

• Can produce laminated periostealrx’n (arrowheads at top of slide)

Brodies Abscess

Two different cases

Brodies AbscessNote the track-like pattern of the radiolucency affecting the metaphysis

Septic Arthritis• Pyogenic or granulomatous etiologies possible

– 50-80% of skeletal tuberculosis affects joints• Rapid joint destruction possible; early dx needed!

– Consider infection in any patient with acute onset of monoarthritic pain and swelling without a probable etiology

– Joint aspiration is definitive for dx of infection and also useful in d/dx of crystal deposition arthropathy

• Elevated ESR, rubor, calor, dolor, etc.

Septic Arthritis• Age: most common < age 30, but range is wide• Staph aureus is most common, but TB, strep,

gonorrhea, brucellosis, etc. may also cause• Large joints (hip and knee) are common sites for

TB joint infection• TB may mimic radiographic appearance of RA in

a joint (but does not show RA distribution)

Septic Arthritis• Spine is common site • IVD space narrowing and

indistinct endplates on both sides

• Pott’s disease = spinal tuberculosis– Chronic TB often shows

Ca++ paraspinal– Fusion of bodies maybe

• Vertebral body collapse = kyphosis

Lateral next slide….

Septic Arthritis• Indistinct endplates on

lateral and oblique

Spine TB

Spine TBParavertebral soft tissue calcifications consistent with granulomatous infection- TB

• Marked thoracic gibbus formation from chronic TB of the spine

Chronic TB spineChronic TB with dramatic kyphosis of spine

Note the soft tissue calcification, consistent with paravertebral TB abscess

Infectious discitisInitial film 55yr male One month after facet injection for pain

Septic Arthritis• Sacroiliac joint infection may mimic appearance of Reactive

arthritis, Psoriatic, RA, etc.• SI joint location more common in IV drug users than individuals

infected under other circumstances

Septic Arthritis

Note the asymmetry of the acetabulae due to subtle loss of cortical margin at lateral margin of roof. Next slide shows progression…

Septic Arthritis

1 month later 2 months later 1 year later

TB of the hip

Chronic infection may result in bony ankylosis of the joint

Age 10 yrs

Age 13 yrs Age 14 yrs

Septic ArthritisNote the rapid, symmetrical loss of joint space over 2 week period

Osteomyelitis - Complications include

• Cloaca = A draining sinus may develop in soft tissues thru the skin to expelled necrotic tissue

• Marjolin’s ulcer = at the site of a chronic cloaca, squamous cell carcinoma may develop due to chronic inflammation

Hydatid Disease - Echinococcosis• A parasitic infection, usually transmitted to

humans by dogs (intermediate host) that have consumed entrails of infected sheep (definitive host).

• Infection of humans occurs through oral contamination; ova penetrate gut and enter blood stream– Most filtered out in vascular beds of liver (75%), lung

(15%) or spleen, where most hydatid cysts are found– Only about 1% of all hydatid disease is skeletal

Hydatid Disease of bone• Sites: Spine and pelvis

are most common• X-ray

– Expansile, “bubbly”appearance

– Mimics neoplasm• Giant Cell• Plasmacytoma• ABC • chordoma

Cysticercosis• Larval stage of parasite taenia solium (pork tapeworm) may be

deposited in subcutaneous tissue, muscles and various organs• Foreign-body response occurs when larvae die

Cysticercosis• Cigar-shaped calcifications are characteristic (up to 23mm long)