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https://upload.orthobullets.com/topic/4032/images/septic hip.jpg
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Introduction
  • An intra-articular infection in children that is considered a surgical emergency and 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
      • knee joint involved in 35% of all cases of septic arthritis
    • risk factors for neonatal septic arthritis q
      • 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
  • Pathophysiology
    • routes of inoculation
      • direct inoculation from trauma or surgery
      • hematogenous seeding
      • 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)
    • 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
    • microbiology
      • 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
        • exposed during transvaginal delivery
      • 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 
        • HaemophilusActinobacillusCardiobacterium, Eikenella, and Kingella
        • fastidious
        • Incidence of septic arthritis caused by H influenzae has markedly decreased since the advent of its vaccine
        • Kingella is best isolated on blood culture media 
  • Prognosis
    • usually good unless diagnosis is delayed
      • delay in diagnosis may result in permanent joint damage, and long-term disability. 
    • poor prognostic indicators 
      • age < 6 months
      • associated osteomyelitis
      • delay >4 days until presentation
      • hip joint (versus knee)
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
      • 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
    • helpful to distinguish from transient synovitis 
      • probabilty of septic arthritis may be as high as 99.6% when all four criteria below are present (Kocher Criteria) q q
        • WBC > 12,000 cells/µl of serum
        • inability to bear weight
        • fever > 101.3° F (38.5° C)
        • ESR > 40 mm/h
      • if none of the above predictors are present, probability of having septic arthritis is <0.2%
      • 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 ***The most important of the labs
        • 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) 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 
    • 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 has been recomended by some, but of questionable value
    • 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
    • should be performed if the patient is febrileas 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 miningitis
Differential Diagnosis
  •  Table - Differential diagnosis of Hip Pain in Children
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,
          • in possible 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
      • antibiotics
        • timing
          • perform joint aspiration, preferably before empiric administration of empiric antibiotics 
          • empiric IV antibiotics are started after samples are sent for culture and are usually continued for 3 weeks
          • once cultures return follow with IV antibiotics targeting pathogens 
          • 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, and clinical picture returns to normal
        • microbial coverage
          • empiric antibiotics
            • based on age and medical comorbidities
            • immunization status determines whether empiric antibiotics should cover H influenzae
Septic Arthritis Antibiotic Treatment
Age
Organism
Antibiotics
<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. gonorrhoeaeS. aureus

oxacillin/cephalospori


 
Surgical 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
    • 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
    • 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
  • Limb-length discrepancy
  • Gait abnormalities
  • Osteonecrosis 
 

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Questions (20)
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(OBQ12.108) Which of the following is true regarding matrix metaloproteinases (MMPs)? Review Topic

QID: 4468
1

They are activated by chelating agents

6%

(219/3768)

2

They mediate the destruction of cartilage in septic arthritis

75%

(2817/3768)

3

Toll-like receptors inhibit the formation of MMPs

6%

(234/3768)

4

They have a anabolic effect on cartilage

6%

(218/3768)

5

Stromelysin is an indirect antagonist of many MMPs

6%

(236/3768)

Select Answer to see Preferred Response

PREFERRED RESPONSE 2

(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? Review Topic

QID: 3357
FIGURES:
1

Further imaging of the pelvis

48%

(989/2049)

2

Open drainage and irrigation of the right hip joint

31%

(625/2049)

3

Repeat aspiration of the hip joint

4%

(86/2049)

4

Percutaneous screw fixation of the proximal femoral physis

0%

(10/2049)

5

Nonsteroidal antiinflamatory medications and observation

16%

(335/2049)

Select Answer to see Preferred Response

PREFERRED RESPONSE 1

(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? Review Topic

QID: 566
FIGURES:
1

Slipped capital femoral epiphysis

1%

(17/2355)

2

Legg-Calve-Perthes disease

6%

(142/2355)

3

Developmental dysplasia of the hip

8%

(187/2355)

4

Residual effects of previous untreated septic hip arthritis

85%

(1991/2355)

5

Acute femur fracture secondary to child abuse

0%

(6/2355)

Select Answer to see Preferred Response

PREFERRED RESPONSE 4

(OBQ06.121) Which of the following Gram stain images most accurately represents the primary causative organism for pediatric osteomyelitis and septic arthritis?
Review Topic

QID: 307
FIGURES:
1

Figure A

18%

(242/1313)

2

Figure B

2%

(21/1313)

3

Figure C

2%

(27/1313)

4

Figure D

2%

(30/1313)

5

Figure E

75%

(982/1313)

Select Answer to see Preferred Response

PREFERRED RESPONSE 5

(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? Review Topic

QID: 2964
FIGURES:
1

Traumatic effusion

1%

(7/862)

2

Toxic synovitis

4%

(35/862)

3

Acute rheumatic fever

1%

(7/862)

4

Juvenille rheumatoid arthritis (JRA)

0%

(1/862)

5

Septic arthritis

94%

(807/862)

Select Answer to see Preferred Response

PREFERRED RESPONSE 5

(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? Review Topic

QID: 4620
FIGURES:
1

Admit for observation

5%

(118/2546)

2

Repeat hip ultrasound

0%

(9/2546)

3

Obtain an MRI

4%

(111/2546)

4

Start the patient on IV antibiotics

3%

(68/2546)

5

Emergent hip arthrotomy with irrigation and debridement

88%

(2228/2546)

Select Answer to see Preferred Response

PREFERRED RESPONSE 5

(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? Review Topic

QID: 1264
1

Elevated absolute neutrophil count

3%

(29/918)

2

Serum white blood cell count > 12,000 cells/cubic millimeter

89%

(814/918)

3

Positive blood cultures

5%

(48/918)

4

Pain with hip extension

1%

(9/918)

5

Symptoms greater than 3 days

1%

(13/918)

Select Answer to see Preferred Response

PREFERRED RESPONSE 2

(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? Review Topic

QID: 3342
1

Group B Streptococcus

76%

(1884/2464)

2

Staph Aureus

19%

(467/2464)

3

Staph Epidermidis

0%

(8/2464)

4

Haemophilus Influenzae

3%

(65/2464)

5

Neisseria Gonnorhea

1%

(26/2464)

Select Answer to see Preferred Response

PREFERRED RESPONSE 1

(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? Review Topic

QID: 3444
1

Kingella kingae

81%

(1728/2128)

2

Mycobacterium tuberculosis

5%

(109/2128)

3

Mycobacterium avium

2%

(51/2128)

4

Neisseria

7%

(141/2128)

5

E-coli

5%

(97/2128)

Select Answer to see Preferred Response

PREFERRED RESPONSE 1

(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? Review Topic

QID: 2971
FIGURES:
1

Elevated neutrophil count

8%

(144/1791)

2

Elevated ESR

15%

(270/1791)

3

Elevated rheumatoid factor

0%

(8/1791)

4

Elevated CRP

73%

(1308/1791)

5

Presence of bacteria on CSF gram stain

3%

(56/1791)

Select Answer to see Preferred Response

PREFERRED RESPONSE 4

(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? Review Topic

QID: 454
FIGURES:
1

MRI

21%

(163/795)

2

CT scan

1%

(6/795)

3

Observation

6%

(49/795)

4

Aspiration

48%

(378/795)

5

Pavlik Harness

25%

(196/795)

Select Answer to see Preferred Response

PREFERRED RESPONSE 4

(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? Review Topic

QID: 3585
FIGURES:
1

Untreated neonatal hip infection

92%

(1974/2141)

2

Chondrosarcoma

1%

(25/2141)

3

Legg-Calve-Perthes disease

5%

(109/2141)

4

Slipped capital femoral epiphysis

0%

(5/2141)

5

Osteosarcoma

1%

(21/2141)

Select Answer to see Preferred Response

PREFERRED RESPONSE 1

(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? Review Topic

QID: 1347
FIGURES:
1

CRP > 5mg/L

5%

(21/452)

2

Delay in treatment >4 days

90%

(408/452)

3

Age > 6 months

1%

(6/452)

4

Absence of associated osteomyelitis

0%

(0/452)

5

ESR > 40mm/hr

3%

(14/452)

Select Answer to see Preferred Response

PREFERRED RESPONSE 2
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