Dr. Kevin Yip

Dr Kevin Yip
Orthopaedic Surgeon
MBBS(UK), FRCS(EDIN), FAM(SING), FHKCOS(ORTHO)

Featured on Channel NewsAsia

Septic Hip

Basics
Description
  • The incidence of septic hip is increasing, especially in elderly and immunosuppressed individuals.
  • This condition may occur in infants, children, adults, and the elderly, but it is more common in the pediatric population.
  • Risks factors include hip surgery (most common cause), intravenous drug abuse, alcoholism, and steroid use.
Epidemiology
Incidence
  • In children, the hip may be the most common site of joint infection .
  • In adults, infected knees are more common than infected hips.
  • The rate of infection after total hip replacement is ~2%.
Risk Factors
  • Local factors:
    • Previous surgery
    • Previous hip replacement
    • Intra-articular hip injection
    • Osteoarthritis
    • AVN
    • Previous trauma
  • Systemic factors:
    • Immunosuppression
    • Intravenous drug abuse
    • Hemophilia
    • Seronegative arthritides
    • Sickle cell disease
Pathophysiology
  • Direct inoculation secondary to surgery is a common cause of infection in the adult hip.
  • Hematogenous spread is more common in the pediatric population than in the adult.
  • Sources include:
    • Urinary tract
    • Lung
    • Skin Infections
Etiology
  • Bacteria in the blood lodge in the vascular synovial membrane or enter directly through a damaged joint capsule or diseased synovium.
  • Common organisms:
    • Staphylococcus aureus:
      • The most common organism in both children and adults.
  • Streptococcus species
  • Gonococcus
  • Pseudomonas species
  • Escherichia coli
  • Salmonella
  • Klebsiella
  • Myobacterium tuberculosis
  • Brucella
Associated Conditions
  • Hemophilia
  • Sickle cell disease
  • Intravenous drug abuse
  • Immunosuppression
Diagnosis
Signs and Symptoms
  • Pain in the groin and/or inner thigh
  • Fever and occasionally chills
  • Concurrent source of infection
History
  • Pain in the affected hip is the most common complaint.
  • Occasionally patients present with isolated pain in the ipsilateral knee.
Physical Exam
  • Fever
  • Skin changes such as a rash or decubitus ulcer
  • Gait disturbances such as antalgic gait or the inability to ambulate
  • Hip examination:
    • Tenderness
    • Hip held in flexion, external rotation
    • Restricted and painful ROM
Tests
Lab
  • Laboratory tests are unreliable, especially in the immunocompromised patient.
  • Elevated ESR
  • Elevated C-reactive protein
  • White blood cell count may or may not be elevated.
    • Usually an elevated percentage of polymorphonuclear leukocytes is present.
  • Hip aspiration
  • Blood cultures
Pediatric Considerations
  • Diagnosis in the neonatal and pediatric population is difficult.
  • The most sensitive factors are thought to be fever >38.5°C, inability to bear weight, elevated ESR, and C-reactive protein >2.0 mg/dL.
Imaging
  • Plain radiography:
    • May remain normal for up to 2 weeks
    • Early findings include widening of the teardrop interval.
    • Late findings include erosive and absorptive changes of surrounding bone and destruction of the femoral head.
  • Nuclear scans
  • MRI:
    • May show soft-tissue abnormality, pelvic fracture, or osteomyelitis or retroperitoneal fluid
    • No studies show its usefulness in the diagnosis of septic arthritis.
  • Ultrasound:
    • Valuable to show effusion in the neonatal and pediatric age groups
    • Used to guide aspiration
Diagnostic Procedures/Surgery
  • Hip aspiration is the most important test in diagnosis.
    • Elevated white blood cell count (100,000-250,000)
  • Positive joint fluid culture
  • Occasionally a positive Gram stain
Pathological Findings
  • Rapid destruction of the femoral head and acetabulum
  • Late findings include septicemia, subluxation, deformity, and ankylosis.
Differential Diagnosis
  • Crystalline arthropathy
  • Inflammatory arthritis
  • Rheumatoid arthritis
  • Hemophilia
  • Transient synovitis of the hip
Treatment
Initial Stabilization
  • Early diagnosis is the key to joint preservation and possibly to patient survival.
  • Initiation of empiric antibiotics after joint fluid is obtained
  • Diagnosis in neonates and children is particularly difficult, and the use of regimented guidelines has been found to be helpful.
  • Diagnosis in the presence of a prosthetic joint also may be difficult because cultures may be negative even in the presence of infection.
Medication
  • After obtaining fluid for cultures and sensitivities, antibiotics based on history and Gram stain should be started immediately.
  • The antibiotics can be tailored after obtaining identification of the infecting organism.
Surgery
  • Open surgical drainage and debridement are the mainstays of treatment.
  • Case series have reported on using hip arthroscopy to debride the hip.
  • If the patient is too ill to undergo surgery, serial aspirations can be performed.
  • Treatment of the infected prosthetic joint:
    • Suppressive antibiotics alone: Used only in patients who cannot tolerate surgery
    • Washout and retention of the components: Useful if the infection is not chronic and the components are stable
    • 1-stage revision surgery:
      • Only 1 surgery for both debridement and revision of the prosthesis
      • Controversial, but may have higher failure rates than 2-stage treatment
    • 2-stage revision surgery is the most reliable method for eradicating infection.
  • Treatment of the late sequelae of hip infection is difficult.
    • In children, may include pelvic osteotomy, hip fusion, or hip resection
    • In the adult, may include hip resection or 2-stage hip replacement
Follow-up
Disposition
Issues for Referral
  • All patients with painful hips should be referred quickly to an orthopaedic surgeon to rule out sepsis.
  • The importance of a quick diagnosis cannot be overemphasized.
  • Antibiotics should not be started until cultures are obtained.
Prognosis
  • If diagnosis and treatment are initiated early, prognosis usually is good.
  • Outcomes usually are poor if treatment is delayed.
  • Infection and osteomyelitis with methicillin-resistant S. aureus is thought to have a worse prognosis than that from methicillin-sensitive organisms.
Complications
  • Osteomyelitis
  • Septicemia
  • Degenerative joint disease
  • Deformity
Miscellaneous
Codes
ICD9-CM
711.95 Septic arthritis, hip
FAQ
Q: How is a septic hip diagnosed and treated in a child?
A: The clinical signs are pain and swelling in the hip, inability to walk, and fever. ESR and C-reactive protein tests should be checked. If levels are elevated, the suspicion for sepsis is high. The joint should be aspirated and antibiotics should be started. If infection is found, the hip should be treated surgically with arthrotomy.

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