This document discusses osteomyelitis, an infection of bone tissue. It defines osteomyelitis and describes the epidemiology, sources of infection, pathogenesis, clinical features, investigations and treatment of both acute and chronic osteomyelitis. Acute osteomyelitis is usually caused by Staphylococcus aureus spreading via the bloodstream and commonly affects the long bones of children and the vertebrae, feet and pelvis of adults. Investigations include blood tests, imaging like x-rays, CT and MRI, and bone biopsy for culture and sensitivity testing. Treatment involves antibiotics, analgesia, splinting, drainage of pus if needed, and follow up to monitor for recurrence.

1. OSTEOMYELITISACUTE OSSTEOMYELITISCHRONIC OSTEOMYELITIS

2. OSTEOMYELITISDEFINITION : inflammation of the boneOsteo= bone, myelitis= inflammation of the marrowBone becomes infected either throughhaematogenous spread of organisms, or, secondary to a contiguous focus of infection. (invasion from a skin puncture, operation or open fracture)Contiguous-focus osteomyelitis:bone infection with relatively normal vascularity and bone infection with generalized vascular insufficiency (eg: diabetic foot) Acute or chronic.

3. Anatomy of the bone

4. EPIDEMIOLOGYOsteomyelitis affects about 2 in 10,000 people.In childrenlong bones In adults vertebrae, feet, and the pelvisRisk factors are  recent trauma  diabetes  Hemodialysis IV drug abuse  People who had splenectomy.

5. SOURCES OF INFECTIONSINFECTION OF ADJACENT JOINT/SOFT TISSUEEXTENSION TO THE BONEPENETRATING WOUND, OPEN FRACTURE, SURGERY TRAUMATIC AND IATROGHENIC IMPLANTATIONSKIN ABRASION, BOIL, SEPTIC TOOTH HEMATOGENOUS SPREAD OF ORGANISMIMPLANTED AT BONE

6. ACUTE HEMATOGENOUS OMPATHOGENESISBloodstream is invaded, perhaps from minor skin abrasion or boil or in the newborn from an infected umbilical cordIn adults  source of infection – arterial line or dirty needle and syringe

7. MICROBIAL INVASIONOrganism usually settles in the metaphysis possibly because of –  highly vascular hairpin arrangement of capillaries slows down the rate of blood flow (sluggish blood flow) has relatively fewer phagocytic cells than the physis or diaphysis thin cortex

8. Foci of osteomyelitisEpiphysisTerminal branches of metaphyseal artery form loops at growth plate and enter irregular afferent venous sinusoid. Blood flow slowed and turbulent, predispose to bacterial seeding plus, lining cell have little/no phagocytic action made it favourable for bacteria.Looped capillaryVenous sinusoidMetaphyseal artery

9. MICROBIAL INVASION1)TRIGGER ACUTE INFLAMMATIONVascular congestion

10. Fluid exudation

11. PMN leukocyte infiltrationINCREASE INTRAOSSEOUS PRESSURE intense pain and obstruction of blood flow

12. 2)SUPPURATION(2ND DAY)Pus appears in the medulla and spread along Volkmann’s canals and elevate periosteum to forms a sub-periosteal abscess then spread along shaft• The pus can spread from here back into the bone, into an adjacent joint or into the soft tissues.Growth plateperiosteumIn infants, infxn often extends into epiphysis and thence into the joint. In older children the physis is a barrier to direct spread but where metaphysis is partly intracapsular (e.g. hip, shoulder, or elbow) pus may discharge through periosteum into the joint.

13. 3)NECROSIS (END OF WEEK)Rising intraosseouspressure, vascular stasis, infective thrombosis and periostealstripping compromise the blood supply to the bone resulting in bone death and formation of a sequestrum.sequestrum4)NEW BONE FORMATIONAt 10-14 days new bone forms from the deep layer of the stripped periosteum. With time, new bone thickens to form involucrum enclosing infected tissue and sequestra.involucrumMedullary cavity

14. 5)RESOLUTIONif infection is controlled and intraosseous pressure released, the bone will healIf infection persist, pus may discharge through perforation in involucrum and track by sinus to the skin surface. The condition is now established as a chronic osteomyelitis

15. Over 90% of acute osteomyelitis cases are caused by Staphylococcus aureusbut Streptococcus pyogenesandHaemophilusinfluenzaemay also cause acute infection of the bone although infection with Haemophilusinflenzae is rare following the widespread use of the Hib vaccine. Pseudomonas aeruginosais often isolated from intravenous drug abusers with vertebral osteomyelitis.Aetiological agents

16. ACUTE HEMATOGENOUS OM

17. CLINICAL FEATURESIn child, presented withpain, malaise and fever

18. H/o preceding skin lesion, injury, sore throat

19. Limb is held still

20. Restricted joint movement

21. Local redness, swelling, warmth and edema- presence of pus

22. In infant,Fails to thrive, drowsy and irritable

23. h/o birth difficulties or umbilical artery cathetherization

24. Metaphyseal tenderness and resistance to joint movement

25. Look for other sites – multiple infectionsIn adult, commonest site of hematogenous spread is spine – backache, mild fever

26. INVESTIGATIONBLOODFBC – leucocytosisESR AND CRP – elevated (CRP is a measurement of the acute phase response and is especially useful in monitoring the course of treatment of acute osteomyelitis because it normalizes much sooner than the ESR.)Blood C&SASPIRATION AND BIOPSY  aspiration of pus from subperiosteal abscess or the adjacent joint  send for bacteriological examination and sensitivity to antibiotics

28. IMAGING1)Plain Radiograph or tomography (changes may lag by 10-14 days) Early changes soft tissue swelling, blurring of fat plane and periosteal reaction Intermediate changes bone destruction (ill defined lytic lesion)CloacaOsteopeniaLate Changes Sequestrum formation Involucrum and bony sclerosis

30. 2. Nuclear medicineBone scan – can be confirmed earlier (48 hours)Technitium 99m-labeled phosphonateGalium 67-labeled citrateIndium-labeled leucocyteIncreased uptake of tracer in bone scans and white cell scans. High sensitivity but other processes such as arthritis and soft tissue infection can appear similar. (lower specificity)

31. Acute OsteomyelitisBone scanRadiograph of kneeIncreased uptake of radiopharmaceutical in the right femur just above the knee joint. Plain film reveals a large lytic area

32. Acute OsteomyelitisBone Scan of the footBone scans, both anterior (A) and lateral (B), showing the accumulation of radioactive tracer at the right ankle (arrow). This focal accumulation is characteristic of osteomyelitis.