Hip Septic Arthritis - Pediatric

Topic updated on 06/08/16 6:08pm
  •  A surgical emergency that requires prompt recognition and treatment 
  • Epidemiology
    • demographics
      • incidence
        • peaks in the first few years of life
      • age
        • 50% of cases occur in children younger than 2 years of age
    • location
      • hip joint involved in 35% of all cases of septic arthritis
    • risk factors for neonatal septic arthritis q
      • prematurity
      • cesarean section 
  • Pathophysiology
    • routes of inoculation
      • direct inoculation from trauma or surgery
      • hematogenous seeding
      • extension from adjacent bone 
        • 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)
    • mechanism of 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
  • Bacteriology
    • organisms vary with age (see chart)  
    • Neisseria gonorrhoeae
      • still the most common organism in adolescents
      • gram negative diplococci
      • 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
    • Group B streptococcus
      • most common in neonates with community-acquired infection
    • Staph aureus  
      • most common in children over 2 years of age 
      • gram positive cocci in clusters 
      • most common in nosocomial infections of neonates
    • HACEK organisms 
      • Haemophilus, Actinobacillus, Cardiobacterium, Eikenella, and Kingella
      • fastidious
      • Kingella is best isolated on blood culture media 
  • Prognosis
    • usually good unless diagnosis is delayed
    • poor prognostic indicators 
      • age < 6 months
      • associated osteomyelitis
      • hip joint (versus knee)
      • delay >4 days until presentation
  • History
    • similar to history of osteomyelitis
    • history of rash and swollen lymph nodes are associated with other conditions in the differential diagnosis and are not expected findings of septic arthritis
    • vaccination history must be obtained
  • Symptoms
    • presents more acutely than osteomyelitis
    • often associated with fever and other systemic symptoms causing toxic appearance
    • children refuse to walk or move their hip
  • Physical exam
    • inspection and palpation
      • localized swelling
      • effusion, tenderness, and warmth
      • hip rests in a position of flexion, abduction, and external rotation 
        • 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
      • unwillingness to move joint (pseudoparalysis)
      • examine adjacent joints
        • must rule out adjacent joint involvement  
  • Radiographs
    • recommended views
      • AP and frog-leg lateral pelvic x-rays
    • findings
      • may be normal, especially in early stages of disease
      • often see widening of the joint space, subluxation, or dislocation
        • in infants, prior to ossification of the femoral head, widening of joint space can be seen by lateral displacement of the proximal femur 
      • may see bone involvement with associated osteomyelitis
  • Ultrasound
    • may be helpful to identify effusion   
    • can be used to guide aspiration
  • MRI
    • difficult to obtain emergently
    • identifies a joint effusion and adjacent osseous involvement
  • Must distinguish from transient synovitis 
    • Probabilty of septic arthritis ranged as high as 99.6% when all four criteria below are present q
      • WBC > 12,000 cells/µl
      • inability to bear weight
      • fever > 101.3° F (38.5° C)
      • ESR > 40 mm/h
    • CRP > 2.0 (mg/dl) is an idenpendent risk factor (not included in studies of the previous 4 criteria)
      • 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: q
      • Fever > CRP > ESR > refusal to bear wieght > WBC 
  • Hip aspiration q 
    • indicated whenever a high suspicion for infection
    • required to confirm diagnosis  
    • joint fluid studies should include
      • cell count with differential
      • Gram stain, culture, and sensitivities
      • glucose and protein levels
    • a septic joint aspirate will show
      • high WBC count (> 50,000/mm3 with >75% PMNs)
      • 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
  • Lumbar puncture
    • consider in a septic joint caused by H. influenzae due to risk of meningitis
Differential diagnosis
  •  Table - Differential diagnosis of Hip Pain in Children
  • Psoas abscess 
    • presents like hip septic arthritis with hip pain and limp, with the limb held flexed
    • commonest organism is Staph aureus
    • may spread to hip joint causing septic arthritis because of
      • indirect passage via psoas bursa
        • lies between hip joint and psoas
        • connects psoas directly to hip joint in 15% of cadavers
      • direct passage between the iliofemoral and iliopubic ligaments
    • treatment
      • percutaneous ultrasound or CT-guided drainage
      • open drainage
        • useful for secondary psoas abscess e.g. spread from the bowel
          • can simultaneously address intraabdominal source
  • Nonoperative
    • antibiotics alone
      • indications
        • adolescent Neisseria gonorrhoeae infection
          • can be treated with large doses of penicillin alone and usually does not require surgical debridement
  • Operative
    • emergent surgical I&D 
      • indications
        • standard of care for almost all septic joints
        • considered a surgical emergency due to chondrolytic effect of pus
  • Septic Arthritis Antibiotic Treatment
    <12 mos staphylococcus sp., group B streptococci, and gram-negative bacilli 1st generation cephalosporin
    6 mos to 5 yrs S. aureusS. pneumoniae, group A streptococci, H. influenzae 2nd or 3rd generation cephalosporin
    5-12 yrs S. aureus 1st generation cephalosporin
    12-18 yrs N. gonorrhoeae, S. aureus




Surgical Techniques
  • Emergent incision and drainage
    • approach
      • most commonly one of the following approaches is utilized
        • medial approach to the hip 
        • anterolateral approach to the hip 
    • technique
      • an arthrotomy is performed to remove all purulent fluid and to irrigate the joint
      • synovial culture and drain placement is recommended
      • follow with IV antibiotics targeting pathogens based on age and medical comorbidities
      • convert to PO antibiotics once the clinical picture improves and definitive sensitivities are obtained
      • duration of antibiotic therapy is generally 3-4 weeks
      • terminate antibiotics once the CRP or ESR return to normal
    • postoperative care
      • range of motion exercises of the affected joint may be started within the first few days after surgery
  • Femoral head destruction
    • complete destruction of the femoral head and neck, easily visible on x-ray
    • salvage operations exist including varus/valgus proximal femoral osteotomies 
  • Deformity
    • physeal damage leads to late angular deformity and leg length discrepancy
  • Joint contracture
  • Hip dislocation
  • Growth disturbance
  • Gait abnormalities
  • Osteonecrosis 


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Qbank (18 Questions)

(OBQ13.94) A 17-month-old girl presents with intermittent fever, hip pain and irritability for 2 weeks. She walks with a limp. On examination, temperature is 38°C, and her hip is held in flexion. Passive hip extension, internal rotation, and abduction causes severe pain. WBC is 29,300 cells/microliter. ESR is 66 mm/h. Radiograph, bone scan and CT scan are shown in Figures A through C. What is the diagnosis? Topic Review Topic
FIGURES: A   B   C      

1. Septic arthritis
2. Psoas abscess
3. Sacroiliitis
4. Transient synovitis
5. Osteomyelitis

(OBQ12.108) Which of the following is true regarding matrix metaloproteinases (MMPs)? Topic Review Topic

1. They are activated by chelating agents
2. They mediate the destruction of cartilage in septic arthritis
3. Toll-like receptors inhibit the formation of MMPs
4. They have a anabolic effect on cartilage
5. Stromelysin is an indirect antagonist of many MMPs

(OBQ12.260) A 3-year-old presents with a 24-hour history of limping and progressive inability to bear weight. The parents recount no history of trauma, but note that he recently had an upper respiratory infection. A clinical photo is shown in Figure A. The patient’s vital signs are stable. Physical exam is limited because of pain. A hip ultrasound is shown in Figure B. Laboratory values are as follows: WBC-15.0 (97% PMN), ESR-120, CRP-5.0. What is the next best step for this patient? Topic Review Topic
FIGURES: A   B        

1. Admit for observation
2. Repeat hip ultrasound
3. Obtain an MRI
4. Start the patient on IV antibiotics
5. Emergent hip arthrotomy with irrigation and debridement

(OBQ11.21) A 2-year-old child is diagnosed with a septic hip. Initially, no organisms grew on the standard blood agar plate. However, after 1 week, the offending organism was recovered in an aerobic blood culture medium. Which of the following organisms was the most likely cause? Topic Review Topic

1. Kingella kingae
2. Mycobacterium tuberculosis
3. Mycobacterium avium
4. Neisseria
5. E-coli

(OBQ11.162) A 2-year-old boy is seen for evaluation of a limp. His history is significant for a left knee infection treated with IV antibiotics as a neonate and a family history of cancer. Laboratory testing demonstrates a normal ESR and CRP. The remainder of his workup is negative. An AP pelvis is seen in Figure A. What was the most likely etiology of his condition? Topic Review Topic
FIGURES: A          

1. Untreated neonatal hip infection
2. Chondrosarcoma
3. Legg-Calve-Perthes disease
4. Slipped capital femoral epiphysis
5. Osteosarcoma

(OBQ10.243) An 8-day-old infant is admitted to the hospital for septic arthritis of the hip. Which of the following will most likely be the causative organism by culture? Topic Review Topic

1. Group B Streptococcus
2. Staph Aureus
3. Staph Epidermidis
4. Haemophilus Influenzae
5. Neisseria Gonnorhea

(OBQ10.255) A 7-year-old boy developed a limp with right leg pain five days ago, and today has trouble bearing weight. On exam, he is lethargic and has chills. His temperature is 38.4 degrees centigrade. He points to his right inguinal region as the source of the discomfort. He winces with compression of his pelvis. Lab studies reveal a white blood cell count of 11,400/ul, CRP of 0.9 mg/dL (normal < 1.0 mg/dL), and erythrocyte sedimentation rate of 55 mm/h. A pelvis radiograph is shown in Figure A. Ultrasound guided aspiration of the right hip joint yields 9,000 leukocytes per mL. What is the most appropriate next step in management? Topic Review Topic
FIGURES: A          

1. Further imaging of the pelvis
2. Open drainage and irrigation of the right hip joint
3. Repeat aspiration of the hip joint
4. Percutaneous screw fixation of the proximal femoral physis
5. Nonsteroidal antiinflamatory medications and observation

(OBQ09.151) An 18 month-old child has been brought to the emergency room by his mother. He had the sudden onset of hip pain 3 days ago and now won't put weight on the affected limb. The child is febrile and an ultrasound (longitudinal view of the proximal femur) shown in Figure A shows the unaffected hip on the left and affected hip on the right. The patient is taken to the operating room for hip aspiration which reveals 60,000 leukocytes with 95% polymorphonucleocytes. What is the most likely diagnosis? Topic Review Topic
FIGURES: A          

1. Traumatic effusion
2. Toxic synovitis
3. Acute rheumatic fever
4. Juvenille rheumatoid arthritis (JRA)
5. Septic arthritis

(OBQ09.158) An 8-month old infant is brought by his parents to your office for fever and malaise. Your inspection of the patient is detailed in Image A. An oral temperature of greater than 38.5 has been found to be the best predictor of this child's condition. What is the second best predictor? Topic Review Topic
FIGURES: A          

1. Elevated neutrophil count
2. Elevated ESR
3. Elevated rheumatoid factor
4. Elevated CRP
5. Presence of bacteria on CSF gram stain

(OBQ08.68) A 6-week old boy refused to move his left hip. The patient was delivered by C-section 4 weeks premature, but otherwise is healthy. He has been afebrile. Examination reveals some mild, diffuse swelling about the left proximal thigh. Passive motion of the hip elicits discomfort. An AP pelvis radiograph is shown in Figure A. What is the most appropriate next step in management? Topic Review Topic
FIGURES: A          

1. MRI
2. CT scan
3. Observation
4. Aspiration
5. Pavlik Harness

(OBQ08.180) A 3-year-old boy presents with his caregiver with concerns regarding a long-standing gait disturbance. The birth history is unknown except for a prolonged ICU stay for sepsis. A pelvic radiograph is shown in Figure A. What is the most likely cause for this child's limp? Topic Review Topic
FIGURES: A          

1. Slipped capital femoral epiphysis
2. Legg-Calve-Perthes disease
3. Developmental dysplasia of the hip
4. Residual effects of previous untreated septic hip arthritis
5. Acute femur fracture secondary to child abuse

(OBQ06.121) Which of the following Gram stain images most accurately represents the primary causative organism for pediatric osteomyelitis and septic arthritis?
Topic Review Topic
FIGURES: A   B   C   D   E  

1. Figure A
2. Figure B
3. Figure C
4. Figure D
5. Figure E

(OBQ04.159) In differentiating pediatric septic hip from transient synovitis, an elevated ESR (>40), history of fever, refusal to bear weight and what other finding has been identified as predictive of a septic hip? Topic Review Topic

1. Elevated absolute neutrophil count
2. Serum white blood cell count > 12,000 cells/cubic millimeter
3. Positive blood cultures
4. Pain with hip extension
5. Symptoms greater than 3 days

(OBQ04.242) A 10-month-old infant is brought to the emergency department for fevers, irritability, and avoidance of motion in the right leg. On physical exam, passive motion of the right hip elicits crying. An AP pelvis and an ultrasound of the right hip are shown in Figures A and B respectively. A hip aspiration yields 82,000 WBC with >80% PMNs. Which of the following is the strongest predictor of a poor prognosis? Topic Review Topic
FIGURES: A   B        

1. CRP > 5mg/L
2. Delay in treatment >4 days
3. Age > 6 months
4. Absence of associated osteomyelitis
5. ESR > 40mm/hr

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