Osteomyelitis: Pathophysiology  Treatment Decisions

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Introduction. 350,000 long bone fxs/yrInfection risk varies:Type I open 10/1,000 infectionsType III open up to 25%. Cost Analysis. InfectionIncrease cost16-21% / ptIncrease hosp stay36-50% / ptTotal Cost ? $ 271 million/yr. Definition. Group of conditionspresence of bacteria

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Osteomyelitis: Pathophysiology Treatment Decisions

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1. Osteomyelitis: Pathophysiology & Treatment Decisions Clifford B. Jones, MD Clinical Assistant Professor, Michigan State University Orthopaedic Associates of Grand Rapids, Grand Rapids, MI Created March 2004

2. Introduction 350,000 long bone fxs/yr Infection risk varies: Type I open – 10/1,000 infections Type III open – up to 25%

3. Cost Analysis Infection Increase cost 16-21% / pt Increase hosp stay 36-50% / pt Total Cost ? $ 271 million/yr

4. 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

5. Why Destruction of Bone Matrix? Proteolytic enzymes Hyperemia Osteoclasts

7. Inflammation Time Table

8. Principles of Treatment Clinical Staging Characterize disease Characterize host Match treatment options to patient Staged reconstruction Appropriate antibiotic coverage Delayed return for osseous reconstruction

9. 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

10. May Classification

11. Pathogenesis Waldvogel, 1971 Hematogenous Contiguous focus of infection Direct inoculation

12. Cierney & Mader Class.

13. Anatomic Classification (Cierny-Mader) 1985

14. Classification Break-Down Medullary Endosteal nidus, minimal soft tissue involvement, ? Sinus tract Superficial Localized to surface of bone, usually 2° to soft tissue defect Localized Localized sequestra, usually associated sinus tract Bone structurally stable s/p excision Diffuse Permeative process, combination of I/II/III, Commonly unstable s/p excision

15. Physiologic Classification (Cierny-Mader, 1985) A-Host: Good immune system & delivery B-Host: Compromised host BL: locally compromised BS: systemically compromised BC: combined C-Host: Requires suppressive or no Tx Minimal disability Treatment required to eliminate disease worse than disease, not a surgical candidate

16. Host Alteration (optimization) Patient education Nutrition No tobacco (including “snuff”) Preoperative antibiotics Perioperative antibiotics Address compromised areas Local Systemic ( fine tune chronic disease)

17. Clinical Staging (Cierny-Mader, 1985) Anatomic Type + Clinical Stage Physiologic Class Example: IV BS tibial osteomyelitis = diffuse tibial lesion in a systemically compromised host

18. Types of Pathophysiology Acute/Hematogenous Chronic/Nonhematogenous

19. Acute/Hematogenous Anatomy (Hobo) Sharp twist in metaphyseal capillaries Stasis (Trueta) Decreased flow in capillaries & veins Combination (Morrissy) Trauma & Bacteria

20. Acute/Hematogenous Progression of Disease Cell death 2° to bacterial exotoxins bacterial culture medium worsens condition ? vacularity, leukocytosis, edema Pressure w/in rigid osseous container Pain, swelling, erythema Potential for septic arthritis (knee, hip, shoulder)

21. Possible Clinical Findings *Signs and symptoms variable None Pain Tenderness Fever HA Nausea/Vomiting Erythema Swelling Sinus Tract Drainage Limp Fluctuence

22. 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

23. 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

24. Radiographs Early – negative changes usually delayed (10-21 days)

25. Radiographs Soft Tissue Swelling, obscured soft tissue planes, haziness Osseous Hyperemia, demineralization Lysis (when > 40% resorbed) Periosteal reaction Sclerosis (late)

26. Radionucleotide Imaging 99M Tc 67Ga 111In WBC

27. 99M Tc Action binds to hydroxyapetite crystals Osteoblastic activity Demineralized bone Immature collagen

28. 99M Tc 3 Phase Bone Scan Radionucleotide angiogram Immediate post injection blood pool 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

29. Cellulitis

30. Osteomyelitis

31. 99M Tc: False Positive DM foot disorders Septic arthritis Inflammatory bone disease Adjacent to pressure sores

32. 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

33. 67Ga Exudation of in vivo labeled serum protein Transferrin, haptoglobin, albumin Results 81% sensitivity, 69% specificity Schauwecker, 1992 Combination with Tc ? sensitivity, but ? specificity

34. 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

35. MRI No radiation Good soft tissue imaging Imaging: TI dark T2 Bright/Mixed

36. T1 bright T2 dark

37. T1 bright T2 dark

38. MRI Acute: ? marrow fat ? granulation tissue H2O Chronic: thickened cortex Low signal on all scans Cellulitis: no marrow changes

39. MRI Results Schauwecker, 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

40. CT Imaging Image cortical and cancellous bone Evaluate osseous adequacy of debridement

41. 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

42. Acute/Hematogenous

43. Changing Bacterial Pathogens

44. Antibiotics Changing sensitivities Newer oral agents Consult Infectious Disease Colleague for recommendations regarding specifics of dosage, route of administration, and duration

45. Local Antibiotic Delivery PMMA beads staged reconstruction retained Cancellous bone graft Biodegradable bead Deliver antibiotic without need for removal

46. Dead Space Management Free tissue transfer Rotational tissue transfer Cancellous bone grafting PMMA beads Acute shortening Bone transport Trabecular metal

47. Long Bone Segmental Defect Free vascularized bone Fibula-pro-tibia Massive cancellous autograft Acute shortening/lengthening Single-level bone transport Double-level bone transport

48. Ilizarov External Fixator Wound stabilization Limb stabilization Acute shortening/lengthening Correction of deformity Static fixation Bone transportation

49. Examples

50. 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

51. Example 1

52. Example 1 Debridement of all non-viable bone with laser doppler Defect filled with antibiotic PMMA 6 wks antibiotics

53. Example 1, at 6 wks Removal Abx beads Bone grafting Lateral arm flap Infection eradication

54. 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

55. Example 2 Debridement Hardware remains Antibiotic beads

56. Example 2 Gastrocnemeus flap, STSG

57. Example 2 At 6 weeks Remove Abx beads Bone grafting Healed wound and fracture

58. 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

59. Example 3

60. Example 3

61. Example 3 Antibiotic beads Latissimus Flap STSG

62. Example 3 Removal Abx beads at 6 wks No bone graft – low demand patient Disease free at 8 years

63. 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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