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