Bones

1. BONES

2. Normal skeletal system
 Bone is a type of connective tissue
 Inorganic component – calcuim hydroxyapatite
 Organic component – cells & protein of matrix

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Bone forming cells – osteoprogenitor
cells, osteoblasts & osteocytes
Osteoblasts – uninucleate, along new bone
forming surfaces, synthesise bone matrix
Osteoblasts surrounded by matrix - osteocytes

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Osteocytes – numerous, osteoblasts which get
incorporated into bone matrix during
synthesis, found within lacunae
Osteoclasts – large multinucleate cells, bone
resorption
Osteiod matrix – 90-95% of type I collagen

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Osteoblasts depositing collagen in random
weave – woven bone / orderly layered – lamellar
bone

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Cartilage lacks blood vessels, lymphatics &
nerves
2 components – cartilage matrix & chondrocytes
Cartilage matrix – inorganic – hydroxyapatite
Organic – 80% water, 20% type II collagen &
proteoglycans
Chondrocytes – primitive mesenchymal cells –
chondroblasts -> chondrocytes
Hyaline cartilage, fibrocartilage, elastic cartilage

9. INFECTIONS – OSTEOMYELITIS
 Inflammation of bone & marrow
 Manifests as primary solitary focus of disease
 Systemic diseases spreading to bone –
typhoid, actinomycosis, syphilis, brucellosis, myc
etoma
 * Pyogenic bacteria & mycobacteria

10. PYOGENIC OSTEOMYELITIS
 Bacterial infection – hematogenous route
, contiguous site , direct implantation
 Infants & young children – 5-15 yrs
 Long bones / vertebral bodies
 Common – staph aureus- express receptor to
bone matrix components & facilitates adherence
to bone tissue

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E.coli, Pseudomonas, Klebsiella
Location – neonate-> metaphysis
Children – metaphysis
Adult – epiphysis

12. Morphology –
 Depends on stage – acute , subacute or chronic
& location of infection
 Suppuration, ischaemic necrosis, healing by
fibrosis & bony repair
 Acute inflammatory reaction -> cell death
 Entrapped bone – necrosis
 Bacteria & inflammation spreads

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Infection begins in metaphyseal end of marrow
cavity occupied by pus, microscopy shows
congestion, oedema, & exudate of neutrophils
Infection spreads along marrow cavity to
endosteum, haversial canal – Periosteitis
May reach subperiosteal space – subperiosteal
abscess

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May penetrate through cortex creating draining
sinus tracts
Combination of suppuration & impaired blood
supply to cortex results in erosion, thinning &
infarction necrosis of cortex – Sequestrum
Later there is formation of new bone beneath
periosteum present over infected bone. This
forms encasing sheath around necrosed bone Involucrum

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Continued neo-osteogenesis gives rise to dense
sclerotic pattern of osteomyelitis
Occasionally acute osteomyelitis may be
contained to a localised area & walled off by
fibrous tissue & granulation tissue – Brodie’s
abscess

17. Clinical course –
 Acute systemic illness with malaise , fever, chills
, leucocytosis & pain
 X – ray – lytic focus of bone destruction
surrounded by zone of sclerosis
 Blood culture , biopsy

18. Complications
 Septicaemia
 Acute bacterial arthritis
 Pathologic #
 SCC
 Secondary amyloidosis

20. TUBERCULOUS OSTEOMYELITIS
 Adolescents or young adults
Morphology –
 Blood borne , originate from focus of active
infection
 Sites – spine , knees & hips

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Central caseous necrosis, granuloma
Involvement of joint space & interverebral disc
are frequent
Pott’s disease – TB of spine commences in
vertebral body, may be associated with
compression #, destruction of intervertebral
discs -> permanent damage & paraplegia

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Psoas abscess – extension of caseous material
alongwith pus from lumbar vertebrae to sheaths
of psoas muscle

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Pain on motion , localized tenderness
, fever,chills & weight loss
Kyphosis & scoliotic deformities
Neurologic deficits