Stick a needle in itDiagnosis and management of septic arthritis in the ED

Dr Sarah Dawson, May 2014

Why septic arthritis?

• Most dangerous and destructive monoarthritis• Can destroy cartilage within days• Mortality 7-15 % despite antibiotic use

Aims

• To list the main differentials for acute monoarthritis• To understand the pathogenesis of septic arthritis• To list the main organisms that cause septic arthritis• To recognise the symptoms and signs of septic arthritis• To understand the key risk factors for septic arthritis and

how this affects subsequent investigation• To describe the anatomy and method for needle aspiration• To describe empirical antibiotic therapy and approaches

for joint aspiration

Differential

• Infection- bacterial, mycobacterial, fungal• Gout• Pseudogout• Reactive arthritis• Osteoarthritis• Haemarthrosis• Lyme disease• SLE• RA

Incidence

• 2-9 / 100 000 person years• 8-27% patients presenting to ED with acute arthritis

Defitition

• Joint sepsis• 2ry to pathogenic innoculation of joint• By direct or haematogenous routes

Pathogenesis

Deposit in synovial

membrane

Enter synovial

fluid

Cause purulent

joint

Bacteria enter joint

Haematogenous spread

Direct innoculation

Bite or trauma

Organisms

• Can be bacterial, fungal, mycobacterial or viral• Bacterial divided into gonococcal and nongonococcal• Gonococcal more common but less morbidity and mortality• Staphylococcus• Streptococcus

Risk Factors

• Age over 80 (LR 3.5, 95% CI 1.8-7.0)• DM (LR 2.7, 95% CI 1.0-6.9)• RA (LR 2.5, 95% CI 2.0-3.1)• Recent joint surgery (LR 6.9, 95% CI 3.8-12.0)• Hip or knee prosthesis (LR 3.1, 95% CI 2.0-4.9)• Skin infection (LR 2.8, 95% CI 1.7-4.5)• Skin infection + joint prosthesis (LR 15, 95% CI 8.1-28)• HIV (LR 1.7, 95% CI 1.0-2.8)• IV drug use• Alcoholism• IA steroid injection

Symptoms

• Pain in affected joint 85%• Swelling in affected joint 78%• Large joint (knee or hip 60%)• Wrists and ankles also common

• Sweats 27%• Rigors 19%• May be subacute- especially TB and

prosthetic joints• More than 1 joint affected in 22%

cases• Underlying RA or overwhelming

sepsis

Signs

• Fever >37.5 57%• Hot, swollen tender joint (or joints)• Reduced ROM

Investigations

• Bloods- FBC, CRP, ESR- low specificity• WCC>10 000 LR 1.4 (95%CI 1.1-1.8)• ESR>30 LR 1.3 (95% CI 1.1-1.8)• CRP>100 LR 1.6 (95%CI 1.1-2.5)

• Synovial WCC and PMN• WCC<25000 LR 0.32, >25000 LR 2.9, >50000 LR 7.9, >100000 LR

28• PMN >90% LR 3.4• PMN<90% LR 0.34

• Synovial fluid microscopy (only +ve in 50%) and culture• Blood culture (+ve in 50%)• Imaging plain radiograph- baseline, osteomyelitis, concurrent joint

disease

Synovial fluid analysis

Anatomy of the knee

Arthrocentesis

Initial Antibiotic choice

• Little evidence comparing different antibiotics• No RCTs, based on likelihood of which organism

Patient group Antibiotic choice

No RF for atypicals Fluclox 2g qds +/- fusidic acid or gentamicin. If pen allergic Clindamycin or 2nd/3rg gen cephalosporin

High risk gram –ve sepsis (elderly, frail, recurrent UTI, recent abdominal surgery)

2nd or 3rd gen cephalosporin eg cefuroxime

MRSA risk Vancomycin plus 2nd or 3rd gen cephalosporin

Suspected gonococcus or meningococcus Ceftriaxone

IV drug users d/w micro

ITU patients d/w micro

Duration of therapy

• No controlled trials• Usually IV abs at least 2 weeks in duration followed by at

least two weeks oral therapy• May need longer for particular organisms- P. aeruginosa,

Enterobacter spp. or S. Aureus with septicaemia

Joint drainage

• Aim to remove pus from joint space- i.e. drain abscess• Surgically- arthroscopy or arthrotomy• Closed needle aspiration

• No randomised controlled studies comparing the two, needle aspiration may be preferable

• If adequate aspiration not possible by needle, surgery may be necessary

• May be indicated initially for hips, shoulders and prosthetic joints

• Arthroscopy usually for knee shoulder and wrist- hips may have arthrotomy

Outcomes

• The prognosis of bacterial arthritis has not improved significantly in the last few decades

• Outcome related to:• host factors- prior joint disease, old age• Virulence of infecting organism• Speed of initiating effective treatment

• Inflammation and destruction of joint may continue even in sterile joints with effective antimicrobial therapy

• Mortality 10-15% dependent on co-morbidities

Summary

• Non gonococcal bacterial arthritis is a dangerous and destructive form of acute arthritis

• Risk factors include pre-existing joint disease, joint replacement, old age, immunosuppression and overlying infection or ulceration

• It usually presents as monoarthritis involving a large joint like the knee

• Because symptoms such as fever may be absent and tests such as FBC and CRP are non specific, joint aspiration is necessary to establish the diagnosis- for cell count, microscopy and culture. BC are also useful

• Staph and strep are the most common pathogens and are usually treated with flucloxicillin, but older patients, ICU patients, IVDUs may have gram-ves and given3rd gen cephalosporin

• Joint drainage- by needle aspiration or surgical means should also be considered

References

• www.uptodate.com : Septic arthritis in adults

• Mary E. Margaretten, MD; Jeffrey Kohlwes, MD, MPH; Dan Moore, PhD; Stephen Bent, MD “Does This Adult Patient Have Septic Arthritis?” JAMA. 2007; 297(13):1478-1488

• C J Mathews, G Kingsley, M Field, A Jones, V C Weston, M Phillips, D Walker, G Coakley “Management of septic arthritis: a systematic review” Ann Rheum Dis 2007;66:440-445