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Old 05-27-2012
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Rheumatology/Orthopedics 2 week left hip pain...what is the most likely dx?

A 67-year-old man is evaluated in the emergency department for a 2-week history of pain
involving the left hip. He has had no fever. Four years ago, he underwent total arthroplasty
of the left hip joint to treat osteoarthritis. One month ago, he underwent tooth extraction for
an abscessed tooth.
On physical examination, temperature is 36.6C (98.0F), blood pressure is normal, and pulse rate is 90/min. Cardiopulmonary examination is normal. A well-healed surgical scar is present
over the left hip, and there is no warmth or tenderness. External rotation of the left hip joint
is markedly painful.
Laboratory studies reveal an erythrocyte sedimentation rate of 88 mm/h.
Radiograph of the left hip shows a normally seated left hip prosthesis. Fluoroscopic-guided
arthrocentesis is performed. The synovial fluid leukocyte count is 38,000/μL (38 109/L)
(90% neutrophils). Polarized light microscopy of the fluid shows no crystals, and Gram stain
is negative. Culture results are pending.
Which of the following is the most likely diagnosis?
(A) Aseptic loosening
(B) Gout
(C) Pigmented villonodular synovitis
(D) Prosthetic joint infection
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Old 05-27-2012
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(D) Prosthetic joint infection
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I'm Predictable In The Unpredictable Future !
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Old 05-27-2012
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EXPLaNation PLZ
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Old 05-27-2012
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Quote:
Originally Posted by tyagee View Post
A 67-year-old man is evaluated in the emergency department for a 2-week history of pain
involving the left hip. He has had no fever. Four years ago, he underwent total arthroplasty
of the left hip joint to treat osteoarthritis. One month ago, he underwent tooth extraction for
an abscessed tooth.
On physical examination, temperature is 36.6C (98.0F), blood pressure is normal, and pulse rate is 90/min. Cardiopulmonary examination is normal. A well-healed surgical scar is present
over the left hip, and there is no warmth or tenderness. External rotation of the left hip joint
is markedly painful.
Laboratory studies reveal an erythrocyte sedimentation rate of 88 mm/h.
Radiograph of the left hip shows a normally seated left hip prosthesis. Fluoroscopic-guided
arthrocentesis is performed. The synovial fluid leukocyte count is 38,000/μL (38 109/L)
(90% neutrophils). Polarized light microscopy of the fluid shows no crystals, and Gram stain
is negative. Culture results are pending.
Which of the following is the most likely diagnosis?
(A) Aseptic loosening
(B) Gout
(C) Pigmented villonodular synovitis
(D) Prosthetic joint infection
Quote:
Originally Posted by tyagee View Post
EXPLaNation PLZ
i 'm sure not body no why
cuz xray showed joint is in position, make loose joint ?
and cell count < 50.000, make infection also ?
and its ofcourse neither gout nor Pigmented villonodular synovitis(associated with bloody synovial fluid)

so PLZ what the ANS
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Old 05-27-2012
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Which of the following is the most likely diagnosis?
(A) Aseptic loosening -- wudnt show the joint in place + also occurs 10-20 years after replacement

(B) Gout-- will show crystals

(C) Pigmented villonodular synovitis-- will have hemorrhagic fluid + increased swelling

(D) Prosthetic joint infection-- although systemic symptoms are absent i would think this is hte answer by exclusion
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Old 05-27-2012
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(D) Prosthetic joint infection

Using a threshold of approximately 10,000 WBC/l is going to have a very good negative predictive value. It is a good rule-out test. With a value of approximately 27,800/uL, the synovial fluid WBC count is a good rule-in test with a very good positive predictive value. It is important to recognize these values are very different than the thresholds we would use for diagnosing chronic periprosthetic infections which hover around 1,800 to 3,000 WBC/uL.

Aseptic loosening shows on X-rays as lines appearing around the prostheses or isolated cavities.

Pigmented villonodular synovitis--The synovial fluid of the joint is often grossly hemorrhagic.
PVNS, under the microscope, looks as the name of the condition suggests; it is composed on nodules and/or villi and has an abundant number of (pigmented) hemosiderin-laden macrophages.

Some cases of failed orthopaedic implants that were considered aseptic loosening based on the absence of clinical signs of infection and the failure to isolate bacteria may actually have an infectious etiology. In addition to biofilms, potentially important concepts that also may contribute to false-negative culture results include the failure to recognize small colony variants induced during growth in vivo and the presence of bacteria inside host cells including osteoblasts. Importantly, bacteria persisting as small colony variants within biofilms and/or inside osteoblasts also may be an explanation for the recurrent nature of musculoskeletal infection.

Last edited by Novobiocin; 05-27-2012 at 11:29 AM.
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Old 05-28-2012
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So in prothetic hip, we consider infection once we have wbc>10000 even with negative culture?
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Quote:
Originally Posted by bisho View Post
So in prothetic hip, we consider infection once we have wbc>10000 even with negative culture?
No, it means that if the count is below 10,000/uL then it is not a prosthetic joint infection. If it is above 27,800/uL then it is highly likely to be a prosthetic joint infection. Between 10,000/uL & 27,800/uL you are in a no mens land. Negative cultures could be due to biofilms and you need to consider that along with other findings.
I am sure there will more clues in the real exam if they even put such a question there which I really doubt. But it's good to know that criteria for Prosthetic jt infection are different from a garden variety septic arthritis.

Last edited by Novobiocin; 05-28-2012 at 08:08 AM.
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