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Updated: Jan 8 2024

Hip Septic Arthritis - Pediatric

Images
https://upload.orthobullets.com/topic/4032/images/joint space widening.jpg
https://upload.orthobullets.com/topic/4032/images/right septic hip.jpg
https://upload.orthobullets.com/topic/4032/images/bad hip_moved.jpg
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https://upload.orthobullets.com/topic/4032/images/screen_shot_2014-05-25_at_8.27.50_pm.jpg
  • SUMMARY
    • Pediatric Septic Hip Arthritis is an intra-articular infection in children that peaks in the first few years of life.
    • While diagnosis may be suspected by a combination of history, physical exam, imaging, and laboratory studies, confirmation requires a hip aspiration. 
    • Considered a surgical emergency and requires prompt recognition and urgent surgical I&D followed by IV antibiotics.
  • EPIDEMIOLOGY
    • Incidence
      • rare
        • affects 4-5 per 100,000 children annually
    • Demographics
      • peaks in the first few years of life
      • 50% of cases occur in children younger than 2 years of age
      • male > female (2:1 ratio)
    • Location
      • hip joint involved in 35% of all cases of septic arthritis
        • knee joint involved in 35% of all cases of septic arthritis
    • Risk factors
      • prematurity (relatively immunocompromised)
      • cesarean section
      • patients treated in the NICU
      • invasive procedures such as umbilical catheterization, venous catheterization, heel puncture may lead to transient bacteremia
  • Etiology
    • Mechanism
      • direct inoculation
        • from trauma or surgery (skin penetration)
      • hematogenous seeding
        • upper respiratory infection precedes about 80% of the cases
      • extension from adjacent bone (osteomyelitis)
        • can develop from contiguous spread of osteomyelitis
        • often from metaphysis
          • common in neonates who have transphyseal vessels that allow spread into the joint
        • joints with intra-articular metaphysis include
          • hip
          • shoulder
          • elbow
          • ankle
          • (NOT the knee)
    • Pathophysiology
      • enzymatic destruction
        • release of proteolytic enzymes (matrix metalloproteinases) from inflammatory and synovial cells, cartilage, and bacteria which may cause articular surface damage within 8 hours
      • increased joint pressure
        • may cause femoral head osteonecrosis if not relieved promptly 
    • Microbiology
      • in up to 55% of cases, no organism is identified
      • organisms vary with age (see chart)
      • Microbiology by Organism
      • Group B streptococcus
      • most common in neonates with community-acquired infection
      • exposed during transvaginal delivery
      • most common in children over 2 years of age 
      • gram-positive cocci in clusters
      • most common in nosocomial infections of neonates
      • Neisseria gonorrhoeae
      • still the most common organism in adolescents 
      • gram negative diplococci, negative Gram stain a majority of the time
      • patients usually have a preceding migratory polyarthralgia, multiple joint involvement, and small red papules
      • may treat with large doses of penicillin alone and usually does not require surgical debridement.
      • Group A beta-hemolytic streptococcus
      • most common organism following varicella infection
      • Haemophilus, Actinobacillus, Cardiobacterium, Eikenella, and Kingella
      • fastidious
      • incidence of septic arthritis caused by H influenzae has markedly decreased since the advent of its vaccine
      •  Kingella noted to be the most common organism in children < 4 years in some studies (best isolated on blood culture media)
  • Presentation
    • History
      • recent local trauma or infections
      • vaccination history must be obtained, particularly with regard to vaccination against Haemophilus influenzae
      • recent or current antibiotics may mask symptoms
    • Symptoms
      • acute onset of pain
        • presents more acutely than osteomyelitis
      • systemic symptoms
        • often associated with fever and other systemic symptoms causing toxic appearance
      • limp or refusal to bear weight
    • Physical exam
      • vitals
        • temperature and vital signs to rule out hemodynamic instability
        • may show toxicity
      • inspection and palpation
        • localized swelling
        • effusion, tenderness, and warmth
        • hip rests in a position of flexion, abduction, and external rotation (FABER)
          • hip capsular volume is maximized with flexion, abduction, and external rotation and is the position of comfort for hip septic arthritis
      • range of motion
        • severe pain with passive motion
        • severe pain with logrolling of the hip
        • unwillingness to move joint (pseudoparalysis)
        • examine adjacent joints and spine
          • must rule out adjacent joint involvement
  • Imaging
    • Radiographs
      • recommended views
        • AP and frog-leg lateral pelvic x-rays, if hips can be put in frog leg position.
      • findings
        • may be normal, especially in early stages of disease
        • widening of the joint space
          • in infants, prior to ossification of the femoral head, widening of joint space can be seen by lateral displacement of the proximal femur
          • this is a sign of significant pus in joint
        • subluxation
        • dislocation
        • bone lesions
          • may see bone involvement with associated osteomyelitis
    • Ultrasound
      • indications
        • neonate contralateral hip
          • in neonates, ultrasound both hips if any septic joint is found, signs and symptoms of infection are muted in neonates, and a missed infection can be catastrophic.
        • can be used to guide aspiration
      • findings
        • may be helpful to identify effusion
        • cannot differentiate between a septic and a sterile effusion
    • MRI
      • may be difficult to obtain expeditiously
      • identifies a joint effusion and possible adjacent osseous involvement which can guide operative treatment
  • Studies
    • Serum labs
      • WBC
        • is elevated in 30-60% of patients with a left shift in 60%
        • neonates may have leukopenia
      • ESR
        • often elevated but may be normal early in the course of infection
      • CRP
        • may rise as soon as 6-8 hours after injury or infection
          • CRP > 2.0 (mg/dl) is an independent risk factor (not included in studies of the previous 4 criteria)
          • CRP < 2.0 (mg/dl) is suggestive of an alternative diagnosis (i.e. transient synovitis)
          • CRP > 2.0 (mg/dl) in combination with refusal to bear weight yields a 74% probability of septic arthritis
          • order of sensitivity of above criteria
            • fever > CRP > ESR > refusal to bear weight > WBC
    • Hip aspiration
      • may confirm diagnosis of septic arthritis
      • fluid samples should be sent for
        • WBC count with differential
        • Gram stain, culture, and sensitivities
        • Glucose and protein levels have been recommended by some, but of questionable value
      • A septic joint aspirate will show
        • high WBC count (> 50,000/mm3 with >75% PMNs)
          • PMN percentage more sensitive than total WBC count
            • 85% PMNs correlates with an 88% sensitivity.
        • glucose 50 mg/dl less than serum levels
        • high lactic acid level with infections due to gram positive cocci or gram negative rods
    • Blood cultures
      • should be performed if the patient is febrile, as they are often positive, even when local cultures are negative
    • Lumbar puncture
      • consider in a septic joint caused by H. influenzae due to risk of meningitis IF there are clinical signs of meningitis
  • Differential
    • Key Differential
      • transient synovitis
      • osteomyelitis
      • JRA
      • JIA
    • Additional Differential
      • Lyme Disease
      • SCFE
      • LCP
      • MED
    • Table - Differential diagnosis of Hip Pain in Children
  • Diagnosis
    • Diagnosis
      • made by a combination of history, physical exam, imaging, and laboratory studies
        • while the Kocher Criteria is commonly used, no one algorithm is diagnostic alone
    • Original Kocher Criteria
      • four criteria
        • WBC > 12,000 cells/µl of serum
        • inability to bear weight
        • fever > 101.3° F (38.5° C)
        • ESR > 40 mm/h
      • algorithm
        • probability of septic arthritis may be as high as 99.6% when all four criteria above are present
        • if none of the above predictors are present, probability of having septic arthritis is <0.2%
          • 3% incidence of septic arthritis if 1/4 criteria present, 40% incidence if 2/4 criteria present, 93% incidence if 3/4 criteria present
          • the Kocher criteria are only sensitive for diagnosing pediatric septic arthritis of the hip and should not be inappropriately applied to other locations such as the knee
    • Modified Kocher Criteria
      • additional criteria
        • CRP
  • Treatment
    • Nonoperative
      • antibiotics alone
        • rarely indicated
          • adolescent Neisseria gonorrhoeae infection
            • in some cases can be treated with large doses of penicillin alone and usually does not require surgical debridement
    • Operative
      • urgent surgical I&D followed by IV antibiotics
        • indications
          • standard of care for septic hip joints
            • if possible in septic arthritis it is better to err on the side of surgical drainage
          • considered a surgical emergency in the hip due to chondrolytic effect of pus
            • removes damaging enzymes which are chondrolytic
          • reduces intraarticular pressure and decreases epiphyseal ischemia
  • Techniques
    • Septic Hip Irrigation and Debridement
      • approach
        • most commonly one of the following approaches is utilized
          • anterolateral approach to the hip
          • anterior approach through the Smith-Peterson interval
          • drainage of the shoulder, elbow, knee, and ankle may be open or arthroscopic
      • technique
        • arthrotomy is performed to remove all purulent fluid and to irrigate the joint
        • consider removal of 1cm by 1cm hip capsule to minimize chances of re-accumulation
        • consider synovial culture
        • intra-articular drain placement is recommended
      • antibiotics
        • timing
          • perform joint aspiration, preferably before administration of empiric antibiotics
          • empiric IV antibiotics are started after samples are sent for culture
          • once cultures return follow with IV antibiotics targeting pathogens 
          • convert to PO antibiotics once the clinical picture improves and definitive sensitivities are obtained
            • current recommendation is a 2-7 day course of culture-specific IV antibiotics followed by a 2-3 week course of oral antibiotics
          • terminate antibiotics once the CRP or ESR normalizes, and clinical picture returns to normal
        • microbial coverage
          • based on age and medical comorbidities
          • immunization status determines whether empiric antibiotics should cover H influenzae
          • Septic Arthritis Antibiotic Treatment
          • Age
          • Organism
          • Antibiotics
          • < 3 months
          • group B streptococci, s. aureus, and gram-negative bacilli
          • 1st generation cephalosporin
          • 3 months to 5 years
          • S. aureus, Kingella, S. pneumoniae, group A streptococci, H. influenzae
          • 2nd or 3rd generation cephalosporin
            Kingella shown to be resistant to vancomycin and clindamycin 
          • 5-12 yrs
          • S. aureus
          • 1st generation cephalosporin
          • 12-18 yrs
          • N. gonorrhoeae, S. aureus
          • 2nd or 3rd generation cephalosporin
      • postoperative care
        • range of motion exercises of the affected joint may be started within the first few days after surgery
  • Complications
    • Femoral head destruction
      • complete destruction of the femoral head and neck, easily visible on x-ray
        • treatment
          • salvage operations exist including varus/valgus proximal femoral osteotomies
    • Femoral neck deformity
      • physeal damage leads to late angular deformity and leg length discrepancy
    • Joint contracture
    • Growth disturbance
      • patients should be followed up for 1-2 years to monitor for physeal arrest
    • Limb-length discrepancy
    • Osteonecrosis
  • Prognosis
    • Overview
      • usually good unless diagnosis is delayed
        • delay in diagnosis may result in permanent joint damage, and long-term disability.
    • Prognostic indicators
      • poor
        • age < 6 months
        • associated osteomyelitis
        • delay >4 days until presentation
        • hip joint (versus knee)
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