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GA NAPNAP 2013Musculoskeletal Infections:
What You Need to Know
Jorge Fabregas, MDChildren’s Orthopaedics of Atlanta
February 23,2012
Goals
IncidencePrevalenceEtiologyTreatment Septic Arthritis Osteomyelitis Soft Tissue Infections
Understand evaluation of patient with possible
infection
The Great Imitator
What defines infection? Fever Pain Swelling Warmth Irritable joint Pus Wound drainage ESR, CRP, WBC
Aspiration ▪ cell count, diff, gram
stain Radiographic changes Positive culture▪ 20% no organism
identified Floyed and Steele 2003
Positive blood culture Response to antibiotics Absence of other
pathology
2yF refusing to walk
Pain x 24 hours Left sided limping, then inability to
bear weight Crying, ill-appearing Family brings to ED for evaluation
History
No trauma Possible fever Low appetite Upper respiratory infection 2 weeks
ago no antibiotics
No sick contacts Goes to daycare No PMH/PSH
Physical examination
37.2, 131, 30, 97/72, 95% RA, 11.1kg Ill-appearing
Laying still Left hip flexed, abducted, externally
rotated Left hip irritable
No pain ROM knee or ankle No tenderness knee and distal Wiggles toes Neurovascularly intact
Laboratory evaluation
CBC WBC 10.36, 63%
PMNs Hgb 12.4 Plt 296
ESR 15
CRP 7.9
Blood cultures
Imaging
Xray normal
Ultrasound effusion
MRI Effusion No osteo No abscess Perfusion
Treatment
OR for aspiration and I&D left hip Small amount of viscous, cloudy, bloody
fluid▪ Sent for culture and DNA studies
Closed over drain Antibiotics ID consult PICC Blood and synovial fluid cultures no
growth to date
Joint aspiration
Inoculate directly into blood culture bottle to enhance culture of fastidious organisms K. kingae
WBC > 50,000/mm3 with predominance of neutrophils (75%) consistent with infection WBC <25, 000 in 34%of patients WBC can be elevated in JRA
Gram stain positive in 30-50% of patients Cultures positive in 50-80% of patients
Low protein, high lactate and low glucose levels compared to serum indicative of infection
Kocher criteria JBJS 2003, JBJS 2004
Fever 38.5 Refusal to bear weight ESR 40 mm/hr Serum WBC >12,000 cells/mm3
4 predictors 99.6% (93%) 3 predictors 93.1% (72.8%) 2 predictors 40% (35%) 1 predictor 3% (9.5%)
CRP > 2.0 Caird et al JBJS 2006
5 predictors 98% 4 predictors 93% 3 predictors 83%
Synovial fluid analysis
Disease Leukocytes (cells/mL) Polymorphs (%)
Normal <200 <25
Traumatic effusion <5,000, many RBCs <25
Toxic synovitis 5,000-15,000 <25
Acute rheumatic fever 10,000-15,000 50
JIA 15,000-80,000 75
Septic arthritis >50,000 >75
• Wide range WBC possible, often lower with atypical organisms
• Organism identified 30% Lyon and Evanich JPO 1999
• No significant clinical or laboratory differences
Management
Surgical decompression of joint space Create capsular window to ensure
continued drainage Leave drain in place until drainage
decreases significantly If no rapid improvement of
symptoms▪ Reexploration ▪ Further diagnostic workup
Epidemiology
Incidence 1:5000 Sonnen and Henry 1996
Acute hematogenous osteomyelitis, age < 13
Septic arthritis twice as common Gutierrez 1997
Most common in 1st decade ½ younger than 5 Gillespie 1987
Lower extremity 70-90% Hip 54% Wang 2003
Incidence decreasing Awareness, immunization, antibiotics
Acute Hematogenous Osteomyelitis & Septic Arthritis
Metaphysis may be within the joint capsule proximal part of
the femur, humerus, ankle and proximal radius.
result in the coexistence of septic arthritis and osteomyelitis
Acute Hematogenous Osteomyelitis & Septic Arthritis
Newborns: infection can cross the physis and enter epiphysis and joint
Capillaries on metaphyseal side of growth plate do not cross growth plate after 6 -18 months
Clinical Manifestations
Trauma or URI may precede symptoms
Joint pain, fever, irritability, anorexia, limp
Redness, swelling, and warmth over affected joint
Painful restricted ROM Hip in flexion, abd, ER
Diagnosis
Blood culture positive 30-50% Peripheral blood
WBC, ESR and CRP elevated▪ CRP occasionally not elevated, especially with
K. kingae Radiology
Evaluate for other causes: trauma, malignancy, osteomyelitis
Diagnosis
Important to differentiate between septic joint and transient synovitis Considerable overlap in clinical and lab findings▪ Hip pain▪ Refuse to WB, limp▪ Pseudoparalysis▪ Hip held in flex, abd, ▪ Recent viral illness
Treatment varies dramatically▪ NSAID’s vs Open arthrotomy
▪ Predominates in 5-10 year old males
▪ Radiology usually normal
▪ US screening ▪ modality of choice for
joint effusion
Most common organisms
Staphylococcus aureus 70-90% cases musculoskeletal infection Blyth JBJS 2001
Newborns S. aureus, Group B strep, Gram negative rods
Children S. aureus, Group A β-hemolytic strep, Strep pneumo, Kingella
kingae, (H. influenza) Adolescents
Gonococcus Sickle cell
Salmonella Foot puncture wound
Pseudomonas
Management Most antibiotics achieve high synovial fluid
concentrations IV therapy until clinical improvement and CRP
returning to normal Uncomplicated septic joint (no concurrent osteo)▪ 3-4 days of IV therapy followed by appropriate oral therapy
Duration depends on response to therapy and on suspected organism▪ S. pneumoniae, K. Kingae, Hib, N. gonorrhhoeae treated for
2-3 weeks▪ S. aureus or gram-negative enteric bacteria treated 3-4
weeks
CA-MRSA
Young, previously healthy children Aggressive skin, soft tissue, and bone infection Risk factors
Antibiotic use within the preceding year, crowded living conditions, compromised skin integrity, participation in team sports.
mecA gene Resistance to methicillin and other β-lactam antibiotics
Panton-Valentine leukocidin (PVL) Cytotoxin Lyses WBCs, promotes tissue necrosis, allows pathway for
CA-MRSA to proliferate in the host Associated with deep-seated and life threatening
infections
CA-MRSA Vanderhave et al JPO 2009
Review of all patients with CA-MRSA infections requiring orthopaedic care
27 previously healthy children (18 M, 9F) average age 9.3 years (3mo to 17.7 y) History of minor trauma (n=4) or sports-related injury
(n=5) within 1 week of presentation in 9 of 27 patients (33%).
Clinical presentation involved an extremity in 23/27 5 upper extremities and 18 lower extremities
17 had temp > 38.5 at presentation, 6 over 40 Osteomyelitis 13, pyomyositis 11, septic arthritis
10, soft tissue or subperiosteal abscess 6, multifocal involvement 13
CA-MRSA Vanderhave et al JPO 2009
2 patients treated w/ clindamycin developed resistance
Significant long-term sequelae 9 patients (33%) 4 chronic osteomyelitis requiring surgery 3-12
mo later 1 fixed elbow contracture in dominant arm 1 heterotopic ossification around the hip 1 destruction of hip due to osteo required THA 1 distal tibial physeal arrest elected amputation
for pain and deformity
Articular cartilage destruction Proteases, peptidases,
collagenases released Leukocytes, synovial cells, cartilage Break down cellular and extracellular
structure of collagen Loss of glycosaminoglycans – 8 hours▪ Softens cartilage▪ Susceptible to increased wear
Once catalytic enzymes released, living bacteria are not necessary for cartilage destruction to continue
Risk Factors for Poor Outcome Prematurity Age less than 6
months Delay in treatment
> 4 days Concurrant
osteomyelitis of femur
Septic dislocation of hip joint
Sequelae of SepticArthritis of the Hip
40% hip infections poor results
Partial or complete destruction of the proximal femoral physis
Osteonecrosis of the femoral head
Trochanteric overgrowth Pseudarthrosis of the femoral
neck Complete dissolution of the
femoral neck and head Progressive limb-length
discrepancy Varus or valgus alignment of
the femoral head Unstable hip articulation Hip dislocation Ankylosis of the hip joint
12yF 3 days right ankle pain
Fevers to 102 Twisted his R ankle last week Unable to bear weight x 2 days Seen at urgent care, dx arthralgia,
Tylenol #3 Warts removed from left knee 1
month ago Cellulitis treated with antibiotics
PMH: twin born 38 weeks via C-section
Exam
37.7 °C, 101, 18, 104/77, 100% RA, weight 46.9 kg
Ill-appearing Generalized maculopapular rash Right foot and ankle swelling, warmth,
maculopapular rash No open wounds No fluctuance Tender over ankle, distal tibia, distal fibula Ankle joint irritable Sensation intact DP and PT pulses palpable
Labs
WBC 18.6, 58% PMNs Hgb 15.8 Plt 215
ESR 10 CRP 23
Blood culture
Bone scan may help localize
Diagnosis
Attempts to obtain culture should be made Blood and tissue cultures▪ Blood cultures positive 30-50% ▪ Tissue critical for diagnosis of organism▪ Culture and histopathology
Inoculation of material directly into aerobic blood culture bottle facilitates isolation of fastidious organisms
Begin empiric therapy for “most likely” organism
Aspiration
Right ankle, tibia, fibula Point of maximum tenderness
Gross purulence Gram positive cocci in clusters
Acute Hematogenous Osteomyelitis
Aspiration Locate point of maximum
tenderness & swelling▪ Usually metaphyseal
16 or 18 gauge spinal needle to aspirate▪ Extraperiosteally, subperiosteally,
intraosseously. Positive in 60% cases (Biopsy 90%)
Management
Institution of appropriate antibiotic therapy Healthy neonate: Group B Streptococcus most
common (S. agalactiae)▪ Oxacillin or cefotaxime
High risk neonate: S. aureus most common▪ Oxacillin or cefotaxime plus gentamycin
Infants to 3 years: S. aureus, K. kingae▪ Cefataxime or cetriaxone and PCN for K. kingae
> 3 years: S. aureus▪ Oxacillin
Acute Hematogenous Osteomyelitis
Diagnosis: clinical findings, and a high index of
suspicion essential. Unexplained bone pain with fever means
osteomyelitis until proven otherwise. onset is usually sudden 30% to 50% of patients have had a recent
or concurrent nonmuscular infection.
Microbiology
S. aureus most common in all age groups CA-MRSA becoming more common
Infants <2 months S. agalactiae, Neisseria gonorrhoeae, gram-
negative enteric bacteria, Candida 2 months – 5 years:
S. aureus, S. pyogenes, S. pneumoniae and K. kingae
> 5 years: S. aureus, S. pyogenes, N. gonorrhoeae
Osteomyelitis - pathophysiology Metaphysis
Small terminal vessels beneath physis – slow flow
Few phagocytic cells Endothelial gaps Rapidly growing long bones
Trauma 30-50% acute hematogenous osteomyelitis iv S. aureus lead to infection in
metaphysis of injured rabbit Morrissy and Haynes JPO 1989
Inflammation Intramedullary pressure Communication with subperiostial space Ischemia/necrosis “Bone cellulitis” “Bone abscess” Subperiosteal
abscess Sinus tract to skin may form = cloaca (Latin: “sewer”) Inaccessible to antibiotics
▪ Chronic osteomyelitis
Treatment
ICU admission Coagulopathy, petechial rash
I&D right fibula, wound vac placement Repeat I&D, vac placement Repeat I&D, closure over a drain
Vancomycin, ceftriaxone → clindamycin → oxacillin
ID consult Blood cultures: MSSA Fibula aspiration: MSSA
Afebrile, CRP 7.6
Osteomyelitis – Complications/Sequelae
Bone loss Need for grafting
Fracture Growth disturbance
Limb length inequality, angular deformity
Chronic osteomyelitis DVT
Other Imaging Studies
Ultrasound can detect
fluid collections or abscess
periostitis/surface abnormalities
CT scan
Fast but less useful in early stages Identifies cortical destruction,
bony sequestrum, extraosseous abscess or gas
CT Scan is helpful in chronic cases small areas of osteolysis (sequestra)
foci of gas, minute foreign bodies
Bone scan Detect specific lesions or multiple lesions Useful in initial 48-72 hours of symptom onset
May have cold scan initially▪ Vascular supply to bone is compromised ▪ Decreased uptake of isotope
Tagged WBC scan can increase specificity for infection (80%)
Positive in other illnesses causing increased osteoblastic activity Malignancy, trauma, cellulitis, postsurgery, arthritis
Preferred test by some pediatric infectious disease experts Less expensive than MRI Sedation not necessary Useful for multifocal or location of infection not obvious
MRI Most sensitive modality, but
not specific Soft tissue abscess, bone
marrow edema, bone destruction
Preferred test for surgical planning
Limitations Expense Sedation in young children Inability to assess whether other
bones are affected Fracture or bone infarction may
not be easily distinguished from infection
Optimal imaging strategy for community-acquired Staphylococcus aureus musculoskeletal infections in children.
Pediatr Radiol. 2008 Aug;38(8):841-7.
Retrospective review of CA-SA osteomyelitis cases since 2001 at Texas Children's Hospital
199 children with CA-SA osteomyelitis MRI bone scintigraphy n=160 n=35 sensitivity = 98% 53%
CONCLUSION: MRI is the preferred imaging modality for the investigation of pediatric CA-SA musculoskeletal infection because it offers superior sensitivity for osteomyelitis compared to bone scintigraphy and detects extraosseous complications that occur in a substantial proportion of patients.
MRI may eliminate unnecessary surgery for children with suspected musculoskeletal infections.
Kan, J.H. American Journal of Roentgenology. November, 2008
Vanderbilt Children’s Hospital in Nashville, Tenn
130 children with suspected musculoskeletal infections
34 patients underwent an MRI after diagnostic or therapeutic intervention
96 patients had an MRI prior to any procedure 60% of patients had neither septic arthritis
nor osteomyelitis
“The majority of the children in the study group had a diagnostic or surgical procedure which could have been avoided with early MRI evaluation.”
Radiology Summary
No radiographic technique can make or exclude diagnosis with certainty raise/lower suspicion when
applied to a specific clinical situation
Soft Tissue Infections
Cellulitis Diffuse leukocyte inflammation, hyperemia,
edema without abscess. Group A Beta hemolytic Strep or S. aureus IV or oral abx Surgical drainage if abscess forms
Puncture wound S. aureus, Pseudomonas if
athletic shoe Tetanus toxoid ER or surgical debridement
Necrotizing Fasciitis
Life and limb threatening Deceivingly benign presentation Polymicrobial, Strep Painful intense cellulitis Skin Bullae and ecchymoses occur
later Definitive dx with biopsy CT, MRI, US
inflammation of fascial layer Emergent surgical debridement
Grey necrotic fascia, muscle spared, foul smelling dishwater pus
Repeat debridements 18% mortality in children even with aggressive
treatment
Summary
What looks like a septic joint may be osteomyelitis
Osteomyelitis easily complicated by septic arthritis Transphyseal vessels in neonates Periosteal abscess can invade joints where
metaphysis is contained within the joint capsule▪ Hip, shoulder, ankle, elbow
CA-MRSA on the increase Remember to think about potential
clindamycin resistance Consider DVT in children with high fever,
high CRP and older than 8 years old▪ LE doppler studies
Consider K. kingae with negative cultures Culture correctly: fastidious organism PCN sensitive
Take home points
Infection is the Great Imitator Evaluation of the patient includes
H&P, ESR, CRP, WBC, imaging, aspiration Kocher criteria for septic hip Obtain aspirate Empiric antibiotics Recognize osteomyelitis and septic
arthritis CA-MRSA is life and limb threatening
Have high index of suspicion