Osteomyelitis & Septic ArthritisB. Markman, MDSFORP9/18/00

EpidemiologyOsteomyelitis- more common in later years of 1st decadeSeptic arthritis- more common in early years of 1st decade (

EtiologyKochs postulates (basis of germ theory)Most early studies could not reproduce heme spreadOnly w/ some local tissue trauma or necrosis, was it reproduce.Many questions still unanswered:Why a predilection for males?Why a increased incidence in the LE?Why a peak age?

OsteomyelitisGenerally- acute hematogenous osteo (SHO)Rare- chronic multifocal osteoAnatomy- kids have highly vascularized metaphyseal bone capillary sinusoids are end vessels; filter against transient bacteremiaHost factors- frequent bacteremia in kidsMany RE cells in medullary cavity; few RE cells in sinusoids. (Hobo, 1921; India ink)(minor) trauma > inc perm in BMImmunocompromised pt; sickle cell dz

Hematogenous spreadWithin 24 hours3 days

Local spread

Clinical pictureH/o minor trauma > fine for 1-3 days > inc pain, tenderness, swelling; dec useRubor, calor, dolor, swelling, & functio laesaClinical exam can be extremely difficult!May have any or all: fever, inc WBC (only 25%, Mayo), inc ESR & CRPXray changes are slow to occurRarefaction @ 7-14d after symptomsPeriosteal reaction can be an expected or worrisome sign

When to be suspicious?Classically pain, warmth, swelling, a fever; an infant may simply not use the extremity.Elevation of the acute phase reactants (>90%,Mayo)Blood Cx is positive in 50%; aspiration of affected site inc yield to 70%Xrays are normal (unless theres another Dx)Bone scan is positive in 90% after first 24hMRI is more expensive; variability in interpretation.

Case: 16 mo w/ 36hr sx1st finding => deep STSPinhole views => metaphysis peaking

Case: 14yo M w/ 6wk sxBone destructionPeriosteal new boneFluid collectionST edema

The workup & treatment:Carefully performed clinical examWhere does it hurt?Make absolutely sure it is not a septic hip.Aspirate bone if desired.(atypical cases)Start antibiotics.Get a three-phase Tc bone scan.

Medical versus Surgical RxMany authors rec routine aspiration to inc yield of Cx; however, some feel that w/ strong clinical, + labs, + BS may start abx rx based on age.Atypical cases may req aspiration.Generally accepted that AHO caught early & w/ normal xrays, does not req surgical intervention. (Philadelphia study)

When to operate:Demonstrated abscessSignificant bone changes on xray (sequestrum/ involucrum)No improvement on appropriate IV abx in 36-48h (must presume- dead bone or abscess).

MicrobiologyOsteomyelitisSeptic Arthritis

Antibiotics:Neonategroup B strepSAGNRInfant 4yoSAH. flu>4yoSA

OxacillinGentamicin3rd gen. Cephalo

Cefuroximethen Ceclor

Cefazolinthen Keflex

Duration of RxTotal duration of 6wks of antibiotics.IV therapy until clear improvement, usually w/ dec ESR/CRP. Then finish 6wks on oral therapy.Do not stop abx until ESR is normal.

Subacute OsteomyelitisRoberts et.al.Diagnostic dilemma: Infection vs. Tumor?No acute episode/symptoms.

Septic ArthritisMost common: 1st knee, 2nd hip, 3rd elbowHost factors:Avascular cartilage; highly vascular sinoviumNo RE cellsMay be caused by penetrating trauma, but usually by hematogenous spread.Always think of local spread from metaphyseal osteo (hip, knee, shoulder).By-products of infection can start to affect hyaline cartilage by as early as 5 days.

Clinical pictureMost commonly in kids

The workup:Exam: red, warm, swollen jtIrritable w/ PROM (hip). Flexed/externally rotated posture (hip).Infant will not use the leg.Elevated ESR/CRP (>90-95%)WBC is not always reliable (Mayo, 25%)Differential count also not perfect (65%)Blood Cx + in 50%Always Xray US (suspicious hip)

Is it SA or toxic synovitis?Kocher et al. (JBJS 1999)

When to aspirate?+ clinical exam & easy jt to tapSuspicious exam & documented effusion (xray/US)Aspiration through cellulitis?Probably a bad idea. One rabbit study;

Synovial Fluid AnalysisFink & Nelson, 1986 (126 cases): 55% - 50K or less 34% - < 25K only 44% - 100KRheumatologists say JRA does not start in the hip.

TreatmentMust drain an infected effusion (either by needle aspiration or surgery).Repeat aspirations can be effective for knees (or elbows & ankles, but harder to tap). May need to be done daily; & parent issues. Aspirations & Abx only for Gonococcus.If youre finding reasons not to tap, you should surgically I&D.THE HIP JOINT MUST ALWAYS BE SURGICALLY DRAINED! (AVN risk inc after 72-96h)

Anterior Drainage of the Septic HipInterval b/w Sartorius & TFLWatch out for lateral femoral cut. n.Find Rectus Femoris

Anterior approach

AntibioticsTotal duration is usually 4 wks.Cx-specific antibiotics!May change IV to PO route when there is clear clinical improvement, usually dec ESR/CRP.

Special situationsPuncture wound osteoPseudomonasGive tetanus, but no prophalactic abx at initial presentation.Lyme ArthritisMono or poly (migrating), Swelling >> painMore indolent courseBorrelia burgdorferiIV PCN or Amoxicillin; TCN is ok >8yo (x4wk)

Special situationsUse Ceftriaxone for Gonococcal arthritis because of inc resistance to PCN/TCN.Dx of JRA requires at least 6 weeks of unremitting symptoms.

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Kochs > organism must be identified in the disease produced; organism must be found at the site of disease; must be able to produce the disease in other animals; must not be found in other diseases.