Septic Arthritis



Septic Arthritis


Alan R. Blackburn II

John R. Fowler



INTRODUCTION


Pathoanatomy



  • Septic arthritis is an infection of the joint space resulting from traumatic inoculation, hematogenous seeding, or contiguous spread.


  • Cartilage destruction is rapid by the action of proteolytic enzymes and bacterial toxins, necessitating prompt diagnosis and management to prevent eventual osteomyelitis.


Mechanism of Injury



  • Small joints of hand—Most commonly due to traumatic inoculation


  • Wrist—Most commonly due to bacteremia with hematogenous seeding


Epidemiology



  • Staphylococcus aureus and Streptococcus are the most common causative organisms, accounting for 91% of septic arthritis cases, regardless of site, although Gonococcus should always be high on the differential. If a clenched fist injury has occurred, polymicrobial infections are typical, and Eikenella corrodens may be involved in up to 30% of cases.


EVALUATION




Physical Examination



  • Signs and symptoms include erythema, edema, warmth, and painful range of motion both actively and passively.


  • Fluctuance may be present.


  • Systemic signs such as fever, chills, or tachycardia may be present; however, these systemic signs may be absent when small joints are affected.


Laboratory Evaluation



  • White blood cell count, ESR, and CRP should always be obtained; however, these studies may or may not be elevated when dealing with small joints of the hand.


  • Blood cultures should always be sent, especially when systemic symptoms are present.


  • Definitive diagnosis is made with synovial fluid analysis; however, aspiration of small joints can be challenging and may yield only minimal amounts of fluid.



    • Aspirate should be sent for Gram stain, aerobic and anaerobic culture, and crystal analysis.


    • Additional fluid may be sent for cell count, fluid protein and glucose levels, and fungal and mycobacterial cultures.


  • A diagnosis of joint sepsis is supported by a synovial fluid WBC count of higher than 50 000/mL (>75% neutrophils), glucose 40 mg less than fasting blood glucose, and a positive Gram stain or culture.


  • The presence of crystals does not exclude the possibility of coexisting infection.

May 7, 2019 | Posted by in ORTHOPEDIC | Comments Off on Septic Arthritis
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