Osteomyelitis:Pathophysiology &

Treatment Decisions

Clifford B. Jones, MDClinical Assistant Professor, Michigan State University

Orthopaedic Associates of Grand Rapids, Grand Rapids, MI

Introduction

• 350,000 long bone fxs/yr• Infection risk varies:

– Type I open – 10/1,000 infections– Type III open – up to 25%

Cost Analysis

• Infection– Increase cost 16-21% / pt– Increase hosp stay 36-50% / pt

• Total Cost $ 271 million/yr

Definition

• Group of conditions• “…presence of bacteria & an inflammatory

response causing progressive destruction of bone.”– Fears, RL, et al, 1998

• “…suppurative process in bone caused by a pyogenic organism”– Pelligrini, VD, et al, 1996

Why Destruction of Bone Matrix?

• Proteolytic enzymes• Hyperemia• Osteoclasts

Inflammation Time Table

Principles of Treatment

• Clinical Staging– Characterize disease– Characterize host

• Match treatment options to patient• Staged reconstruction• Appropriate antibiotic coverage• Delayed return for osseous reconstruction

Classification

• Waldvogel, 1971– Classification based on pathogenesis

• May, 1989– 5 parts, post-traumatic tibial osteomyelitis

• Cierny & Mader, 1985– 4 factors affecting outcome– Host, site, extent of necrosis, degree of

impairment

May Classification

PathogenesisWaldvogel, 1971

1. Hematogenous2. Contiguous focus of infection3. Direct inoculation

Cierney & Mader Class.

AnatomicClassification

(Cierny-Mader)1985

Classification Break-DownI. Medullary

• Endosteal nidus, minimal soft tissue involvement, ? Sinus tract

II. Superficial• Localized to surface of bone, usually 2° to soft tissue defect

III. Localized• Localized sequestra, usually associated sinus tract • Bone structurally stable s/p excision

IV. Diffuse• Permeative process, combination of I/II/III, • Commonly unstable s/p excision

Physiologic Classification(Cierny-Mader, 1985)

A-Host: Good immune system & delivery

B-Host: Compromised hostBL: locally compromisedBS: systemically compromisedBC: combined

C-Host: Requires suppressive or no TxMinimal disabilityTreatment required to eliminate disease worse than disease, not

a surgical candidate

Host Alteration(optimization)

• Patient education• Nutrition• No tobacco (including “snuff”)• Preoperative antibiotics• Perioperative antibiotics• Address compromised areas

– Local– Systemic ( fine tune chronic disease)

Clinical Staging(Cierny-Mader, 1985)

Anatomic Type + Clinical StagePhysiologic Class

Example: IV BS tibial osteomyelitis = diffuse tibial lesion in a systemically compromised host

Types of Pathophysiology

• Acute/Hematogenous• Chronic/Nonhematogenous

Acute/Hematogenous

• Anatomy (Hobo)– Sharp twist in metaphyseal capillaries

• Stasis (Trueta)– Decreased flow in capillaries & veins

• Combination (Morrissy)– Trauma & Bacteria

Acute/HematogenousProgression of Disease

• Cell death 2° to bacterial exotoxins bacterial culture medium worsens condition

vacularity, leukocytosis, edema Pressure w/in rigid osseous container Pain, swelling, erythemaPotential for septic arthritis (knee, hip, shoulder)

Possible Clinical Findings *Signs and symptoms variable

• None• Pain• Tenderness• Fever• HA• Nausea/Vomiting

• Erythema• Swelling• Sinus Tract• Drainage• Limp• Fluctuence

Clinical Findings

• Must have high index of suspicion• Inappropriate use of antimicrobials

– obscure signs and symptoms • Must obtain diagnosis quickly

– If appropriate treatment started < 72°:• Decrease incidence of chronic osteomyelitis• Decrease destruction of bone

Laboratory Data• Acute (Morrey BF, OCNA, 1975)

WBC (25% of time)– Abnormal differential, Left Shift (65%)– Blood Culture

• 50% positive• Chronic

– Mild anemia, – Elevated WESR, C-reactive protein– Possible leukocytosis with L shift– Blood Culture – usually negative

Radiographs

• Early – negative– changes usually delayed (10-21 days)

Radiographs

• Soft Tissue– Swelling, obscured soft tissue planes, haziness

• Osseous– Hyperemia, demineralization– Lysis (when > 40% resorbed)– Periosteal reaction– Sclerosis (late)

Radionucleotide Imaging

• 99M Tc

• 67Ga

• 111In WBC

99M Tc

• Action– binds to hydroxyapetite crystals

• Osteoblastic activity– Demineralized bone– Immature collagen

99M Tc• 3 Phase Bone Scan

1. Radionucleotide angiogram2. Immediate post injection blood pool3. Three hour: soft tissue, urinary excretion

• Diagnosis– Cellulitis: Phases 1 &2, no change 3– Osteomyelitis: Phases 1 & 2, focal 3

• Results: 94% sensitivity, 95% specificity– Rosenthal 1992, Schauwecker 1992

Cellulitis

Osteomyelitis

99M Tc: False Positive

• DM foot disorders• Septic arthritis• Inflammatory bone disease• Adjacent to pressure sores

99M Tc

• 4 Phase Bone Scan• New development• Action:

– Mature bone: uptake stops at 4 hr– Immature woven bone: cont’d uptake at 24 hr

• Problem: needs f/u imaging at 24 hr (compliance)• Gupta 1988, Israel 1987, Schauwecker 1992

67Ga

• Exudation of in vivo labeled serum protein– Transferrin, haptoglobin, albumin

• Results– 81% sensitivity, 69% specificity– Schauwecker, 1992

• Combination with Tc sensitivity, but specificity

111In WBC

• Used in combination (Seabold, 1989)– In/Tc: 88% accurate– Ga/Tc: 39% accurate

• Preparation problem rad dose to spleen, 18-24hr delay

• Spine (Whalen, Spine 1991)– 83% false negative – Recommended use of MRI

MRI

• No radiation• Good soft tissue imaging• Imaging:

– TI dark– T2 Bright/Mixed

T1 bright T2 dark

T1 bright T2 dark

MRI

• Acute: marrow fat granulation tissue H2O

• Chronic: thickened cortex– Low signal on all scans

• Cellulitis: no marrow changes

MRI ResultsSchauwecker, 1992

• Sensitivity 92-100%• Specificity 89-100%• Excellent for Spine (Modic, RCNA, 1986)

– Sens 96%, Spec 92%, Accuracy 94%• Evaluates soft tissue extension• Sinus tract formation

– Bright Tx from skin to bone

CT Imaging

• Image cortical and cancellous bone

• Evaluate osseous adequacy of debridement

Aspiration Biopsy

• Acute– Good, only 10-15% false negative

• Chronic– Sinus tract culture: 76% sens, 80% spec

• 70% with S aureus & Enterococcus• 30% Pseudomonas• Does not determine correct Abx

Acute/Hematogenous

Changing Bacterial Pathogens

Antibiotics

• Changing sensitivities• Newer oral agentsConsult Infectious Disease Colleague for

recommendations regarding specifics of dosage, route of administration, and duration

Local Antibiotic Delivery

• PMMA beads – staged reconstruction– retained

• Cancellous bone graft • Biodegradable bead

– Deliver antibiotic without need for removal

Dead Space Management

• Free tissue transfer• Rotational tissue transfer• Cancellous bone grafting• PMMA beads• Acute shortening• Bone transport• Trabecular metal

Long Bone Segmental Defect

• Free vascularized bone• Fibula-pro-tibia• Massive cancellous autograft• Acute shortening/lengthening• Single-level bone transport• Double-level bone transport

Ilizarov External Fixator

• Wound stabilization• Limb stabilization• Acute shortening/lengthening• Correction of deformity• Static fixation• Bone transportation

Examples

Example 1

• 54 yo Male• Post-operative Pseudomonas osteomyelitis• Refractory to HW removal & Ancef• Healthy, non-smoking• Cierny III A Host

Photos from M Swiontkowski

Example 1

•Dead Space

•Calcaneal defect

Example 1

• Debridement of all non-viable bone with laser doppler

• Defect filled with antibiotic PMMA• 6 wks antibiotics

Example 1, at 6 wks

• Removal Abx beads• Bone grafting• Lateral arm flap• Infection eradication

Example 2

• 47 yo Male, smoker• Presentation 2 months s/p ORIF closed proximal

tibia fx• Draining wound• Exposed HW• Cierny III BC Host

• Photos from M Swiontkowski

Example 2

• Debridement• Hardware remains• Antibiotic beads

Exposed plate

Example 2

• Gastrocnemeus flap, STSG

Example 2

• At 6 weeks• Remove Abx beads• Bone grafting• Healed wound and fracture

Example 3

• At 5 yo, tibial osteomyelitis• Partially treated• At 62 yo, presentation to MD• Chronic draining tibial osteomyelitis• Cierny III BC Host

• Photos from M Swiontkowski

Example 3

•Sinus tracts

•Chronic skin changes

Example 3•I&D to normal bleeding bone with laser doppler

•Bx – negative for cancer

Example 3

• Antibiotic beads• Latissimus Flap• STSG

Example 3

• Removal Abx beads at 6 wks• No bone graft – low demand

patient• Disease free at 8 years

Conclusion

• Prevention best• High suspicion• Early intervention• Obtain deep

cultures• Aggressive

debridement

• Appropriate Abx• Early coverage• Stabilize

appropriate sites• Strive for function

and cure

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