Approach to Acute Monoarthritis

1
Approach to Acute Monoarthritis

• Hrach Ike Kasaryan MSIV

2
Definitions

• Acute Monoarthritis -acute inflammatory process
  that develops in a single joint over the course
  of a few days and less than two weeks

3
Differential
4
Work Up

• Many joint disorders initially can produce pain
  and swelling in a single joint
• Since missing important joint disorders such as
  septic arthritis can cause significant morbidity
  and mortality an appropriate approach to the
  diagnostic work up must be made
• If taken lightly, you may get burnt and cause a
  patient serious harm and life long consequences

5
(No Transcript)
6
Step 1History

• Establishing the chronology of symptoms is
  important
• Rapid onset over hours to days usually indicates
  an infection or a crystal-induced process
• Fungal or mycobacterial infections usually have
  an indolent and protracted course but can mimic
  bacterial arthritis

7
History

• Is there are history of Trauma?
• Even with no Trauma, if they have osteoarthritis,
  still may have traumatic injury
• Are there other joints involved
• Are there any penetrating injuries?
• Sexual history and history of illegal drug use,
  alcohol use, travel, and tick bites should be
  ascertained

8
History

• Look for the risk Factors!!
• A prospective, three-year study1 found that the
  most important risk factors for septic arthritis
  are a prosthetic hip or knee joint, skin
  infection, joint surgery, rheumatoid arthritis,
  age greater than 80 years, and diabetes mellitus

• Arthritis Rheum 1995381819-25

9
History
10
(No Transcript)
11
Step 2 Physical

• determine whether the source of the pain is the
  joint or a periarticular soft tissue structure
• Simple range of motion test can give great
  insight
• True intra-articular problems cause restriction
  of active and passive range of motion
• whereas periarticular problems restrict active
  range of motion more than passive range of
  motion.
• For example a septic knee will hurt no matter
  which way you move it or touch it. Where as a
  sprain will only hurt in certain directions or
  under stress

12
(No Transcript)
13
History of Trauma

• Radiology studies are now in order
• If the results show Fracture/Avulsion etc. it is
  now a matter of an ortho consult
• If the results show ostearthritis or
  chondrocalcinosis, you no longer are chasing a
  traumatic cause of the monoarthritis and you must
  look further

14
(No Transcript)
15
(-) Trauma or Radio work up (-)

• In this case, some lab studies are now in order.
• CBC, Uric Acid and ESR are general screens to
  lead us further
• High WBC, may be infection or chronic
  inflammation?
• High Uric Acid may be gout?
• High ESR, arthritis exacerbation??

16
Is it septic??

• Blood cultures should be obtained in patients
  with suspected septic arthritis.
• However cultures are positive in only about 50
  percent of nongonococcal infections but are
  rarely positive (about 10 percent) in gonococcal
  infection
• DONT LET NEGATIVE BLOOD CX THROW YOU OFF THE
  SEPTIC JOINT TRACK!!!

17
(No Transcript)
18
To Tap or Not To Tap that is the question
19
Tapping the joint.

• We have now reached a critical point in the
  decision tree.
• If there is even a slight suspicion that this
  might be an infectious cause a tap is mandatory!
• IF there is no effusion and there is still
  suspicion that the patient has septic arthritis,
  than CT guided or US guided tap should be
  undertaken.

20
why is tapping so critical??

• Because the results will dramatically change our
  therapy! Otherwise we wouldnt do it
• If it leads us down the infectious route, we use
  Antibiotics
• If it leads down the RA or other immune mediated
  route we blast the patient with steroids.
• Now think about the situation of not tapping the
  patient with septic arthritis, and blasting them
  with steroids!
• If the wrong call is made, kiss that joint goodbye

21
Tapping the knee (medial approach)

• Locate the inferior and superior pole of the
  patella and then draw a small circle half way
  between these marks and than move medially from
  that point until the edge of the patella
• The skin is cleansed with betadine and then
  alcohol.
• Than anesthetize the skin with 2 lidocaine using
  a 1 1/2 inch 25 gauge needle.

22
Tapping the Knee

• After marking the point of entry and skin prep,
  anesthetize the skin and subcutaneous tissue down
  to the synovium with 1-2 xylocaine without
  epinephrine

23
Tapping the knee

• After 1 minute or so, an 18 gauge needle can then
  be inserted and fluid withdrawn.
• As little as one or two drops can be used for
  culture , smears, and crystal ID

24
Tapping the Knee

• synovial fluid should be sent for a white blood
  cell (WBC) count with differential (specifically,
  the percentage of polymorphonuclear neutrophilic
  leukocytes), crystal analysis, Gram staining, and
  culture
• Superimposed cellulitis is a relative
  contraindication to arthrocentesis
• can be performed safely in patients who are
  taking warfarin (Coumadin)
• Removal of as much synovial fluid as possible
  offers symptomatic relief and helps to control
  infection
• If infection is suspected, ABX should be started
  after the tap empirically and than changed when C
  and S return
• Until infection has been ruled out,
  corticosteroids should not be injected into a
  joint.

25
So what do we do with the results after the
patient hates us for the tap?
26
(No Transcript)
27
Fat Droplets

• Fat droplets could indicate bone trauma and
  damage
• Orthopedic consult would be appropriate and
  patient may need surgery

28
(No Transcript)
29
Bloody

• If the on tap in draws back bloody, or
  microscopically many RBCs with out WBCs, the
  diagnosis of Hemarthrosis is now made
• If the patient has a history of a bleeding
  disorder (classically clotting factor
  difficiencies) appropriate management should be
  started
• If patient no history of trauma or clot d/o than
  a work up for inherited clotting d/o should be
  started

30
(No Transcript)
31
Crystals are seen

• If positively bifringent in polarized light and
  needle like crystals are seen the dx of Gouty
  arthritis can be made
• If negatively bifringent crystals are seen
  Pseudogout may be dx
• How ever, the finding of crystals does not
  exclude the diagnosis of septic arthritis
• The entire clinical picture should be considered
  when ruling out infectious causes keeping in mind
  it is the worst case scenario for the pt.
• Along with the crystals, there will be an
  inflammatory WBC, but much less segs, and much
  lower WBC count than septic picture would have

32
(No Transcript)
33
Non inflammatory

• Fluid is Transparent WBC
• We can now consider these noninflammatory dx, and
  make the appropriate theraputic decisions

34
(No Transcript)
35
Inflammatory Fluid

• Translucent fluid, 2000
• With this type of numbers, the following could be
  possibilities
• SLE, LYME, Spondyloarthropothies, Rheumatoid,
  Reactive Arthritis or others
• Even though no crystals could still be gout or
  psuedogout all though unlikely

36
(No Transcript)
37
Inflammatory and Septic

• Opaque fluid (frank pus) WBC75,000 75 segs.
• Any WBC 100,000 is infection until proven
  otherwise!!
• With these results, the appropriate management
  could be initiated if ABX were not started
  already
• However since we are good clinicians, we already
  started empiric Tx from high suspicion and need
  only to wait for culture and sensitivities to
  modify the ABXs.

38

• This is an xray of a untreated septic joint
• Notice the ulmost non-existant joint space
• And the very irregular borders of the bone at the
  joint suggesting necrosis

39
Conclusions

• In acute monoarthritis, Septic arthritis is the
  worst case with worst outcomes
• Therefore, you should assume it is until you have
  reached a thresh hold to rule it out
• 3 good rules for the Acute Monoarthritis
• RULE OUT SEPTIC JOINT!!! RULE OUT SEPTIC JOINT,
  RULE OUT SEPTIC JOINT!!!