Bone and Soft Tissue Infection Flashcards
OM
Bone infection
SA
Joint infection
Types of OM
Acute (days/wks)
Chronic (months/years) - assoc with avascular necrosis and sequestrum formation within bone
Specific - e.g. TB
Non-specific
Where OM affects most
Long bones of legs and arms in kids
Vertebrae in adults
Diabetics may get it in their feet if they are ulcerated
Who gets OM?
Mostly kids
Hx of minor trauma or other dx (e.g. DM, RA, immunocompromised, long term steroids Rx, sickle cell)
Sources of infection of OM
Haematogenous spread (bodily infection –> organism enters BS –> infiltrates BM –> localised systemic reaction)
Localised spread from contagious site of infection (e.g. open fracture, bone surgery, joint replacement)
Secondary to vascular insufficiency, reduced WCC to dispose of microbes reaching bones (dx affecting circulating, e.g. DM, sickle cell)
Organisms infecting <1y
OM
Staph aureus
GBS
E. coli
Organisms infecting older children
OM
Staph aureus
Strep pyogenes
H. influenzae
Organisms infecting adults (OM)
Staph aureus
Coagulase negative staphylococci (prostheses)
propionbacterium spp (protheses)
Myobacterium tuberculosis
Pseudomonas (secondary to penetrating injuries, IVDA)
Organisms infection diabetic foot and pressure sores (OM)
Mixed incl. anaerobes
Organisms infecting those with sickle cell dx (OM)
Salmonella
Organisms infecting fishermen, filleters (OM)
Mycobacterium marinum
Organisms infecting those with debilitating illness/HIV
Candida albicans
Where does AOM tend to affect?
Metaphysis of long dose (e.g. distal femur, proximal tibia/humerus) or joints with intra-articular metaphysis (e.g. hips, elbow)
METAPHYSIS MOST COMMON SITE as sluggish BF, fewer phagocytic cells
Bacteria settle in metaphysis –> acute inflammation –> increased pressure –> suppuration –> release of pressure as pus moves into medulla, subperiosteum and joint
Necrosis of bone (sequestrum)
New bone formation (Involucrum)
Can either resolve or –> COM
What are the CFs of OM in infants?
Minimal signs --> v. ill FFT Drowsy/irritable Metaphyseal tenderness/swelling Decreased RoM Positional change Commonest around knee
What are the CFs of OM in children?
Severe pain w. reluctance to move (neighbouring joints flexed)
Fever, tachycardia
Malaise, fatigue, NV, toxaemia
What are the CFs of OM in adults?
Tends to be after open fracture or surgery
How do you diagnose OM?
Hx Ex (pulse, temp) Suspect if local symptoms and non-specific signs/symptoms of inflammation
Blood tests - FBC, differential WCC, ESR, CRP, blood cultures x3 (at peak of temp), UE
Imaging
Bone biopsy for definitive diagnosis
Swabs/tissue in prosthetic infections
Imaging for OM
XRay (normal in first 14 days) USS Aspiearion Isotope bone scan Labelled white cell scan MRI - best
Xray signs of OM
Early - minimal change
Early periosteal changes - lytic lesions in medullary cavity
Late periosteal changes - sequestrum formation (dead bone separating)
Involucrum - layer of new bone growth outside existing bone
Differentials of OM
Acute SA Acute inflammatory arthritis Trauma Transient synovitis Sickle cell crisis, rheumatic fever Soft tissue infection (e.g. cellulitis, erysipelas)
Complications of OM
Septicaemia Death Metastatic infection Pathological fracture SA Altered bone growth Chronic OM
Management of OM
Supportive for pain/dehydration Analgesia Rest, splintage Antibx - flucolox and benzylpen empirical (IV --> oral) Surgery
Reasons for antibx to fail in OM Rx
Drug resistance Bacterial persistence Poor host defences, e.g. IDDM, alcoholism Poor drug absorption Drug inactivated by host flora Poor tissue penetration
Indications for surgery in OM
Aspiration of pus for culture/diagnosis
Abscess drainage
Debridement/lavage of dead/infected/contaminated tissue
Refractory to non-op Rx >24-48h
Aetiology of chronic OM
Following acute OM
Following op, open fracture
Immunosupressed, DM, elderly, drug abusers,
Repeated breakdown of healed wounds
Organisms causing chronic OM
Staph aureus, E. coli, strep pyogenes, proteus
What is the pathology of COM?
Cavities, sinuses
Dead bone (retained sequestra)
Involucrum
Chronic inflammation histologically
Complications of COM
Chronically discharging sinus and flare ups Ongoing metastatic infection Abscess formation Pathological fractures Growth disturbance and deformities Squamous cell carcinoma
Mx of COM
Local gentamicin cement/beads
System IV/oral antibx
Rx soft tissue problems
Deformity correction? Massive reconstruction? Amputation?
Routes of infection of SA
Haematogenous (e.g. septicaemia)
Eruption of bone abscess
Direct invasion (e.g. penetrating wound, IA injury, iatrogenic (joint infection, arthroscopy)
RFs for SA
Prosthetic implant
Damaged joints, e.g. RA
Aetiology of SA
Infected joint replacement most common
Metaphyseal septic focus can lead to either septic arthritis/OM
SA most common organisms
STAPH AUREUS, H. influenzae, strep pyorgenes, E. coli
Pathology of SA
Acute synovitis w. purulent joint effusion
Articular cartilage attacked by bacterial toxin and cellular enzymes –> complete destruction of articular cartilage
Sequlae of SA
Complete recovery or
Partial loss of articular cartilage and subsequent OA or
Fibrous/bony anklylosis –> dec. RoM
Neonatal presentation of SA
Irritability, resistant to movement, ill
Child/adult presentation og SA
Acute pain in single joint Reluctance to move joint Fever and tachycardia Tenderness Joint swelling/redness/hot
In adults often knee
Ix SA
FBC, WBC, ESR, CRP, blood cultures
USS, XRay (?OM, concurrent join), aspiration (arthocentesis - removal of synovial fluid from joint effusion, diagnostic and therapeutic - red. pressure –> red. pain) - req. for definitive diagnosis
Differentials SA`
Acute OM Trauma Irritable joint Haemophilia Rheumatic fever Gout
Mx SA
Analgesia
Antibx (3-4w)
Arthrocentesis
Surgical drainage - emergency, open/arthroscopic lavage
Infected joint replacements - 1/2 stage revision
Rehab and physio
TB classification
Extra-articular
Intra-articular
Vertebral body
CF TB
Insidious onset and general ill health Contact with TB Pain, esp at night, swelling, wt loss, fever Joint swelling, reduced RoM Anklyosis Deformity
Pathology TB
Primary complex in lung/gut
Secondary spread common in joints/bone
Tuberculous granuloma
Malnutrition/HIV/AIDs predispose to TB
CF spinal TB
Little pain
Present with kyphosis/abscess
Diagnosis of TB
Long Hx affecting single joint
Marked thickening of synovium, marked muscle wasting, periarticular osteoporosis
Ix TB
FBC, ESR Mantoux test Sputum/urine culture XRay - soft tissue swelling, periarticular osteopenia, articular space narrowing Joint aspiration & biopsy (AAFB)
Differentials TB
TS Monoarticular RA Haemorrhagic arthritis Pyogenic arthritis Tumour
Mx TB
2 months - rifampicin, isoniazid, ethambutol
6-12m: rifampicin, isoniazid
Rest, splintage, op drainage sometimes
