Brian P. Jacob, David C. Chen, Bruce Ramshaw, Shirin Towfigh (eds.) - The SAGES Manual of Groin Pain-Springer International Publishing (2016)

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J.C. Campbell and G.D. Paiement
Fevers, chills, and leukocytosis may be seen; however, their absence
does not exclude the diagnosis of a septic hip.
Diagnostic Exams X-rays most often do not show any abnormalities,
with the exception of long-standing cases of osteomyelitis in which a
sequestrum and involucrum have had time to evolve. MRI can be useful
if considering osteomyelitis. However, in the case of a simple septic joint,
MRI will provide no more information other than the presence and size
of the effusion. Aspiration and targeted surgical and antibiotic treatment
are used as the standard of treatment. Synovial fluid is routinely sent for
crystal examination, cell counts, and cultures. Cell counts above 50,000
white blood cells (WBC) and with greater than 75 % polymononuclear
(PMN) cells are considered indicative of infection and are typically taken
to the operating room for joint irrigation and debridement [ 9 ]. It is
important to note that immunosuppressed patients may have an infected
joint space in the presence of lower cell counts. Culture examination,
although a critical part of the examination, does not trump the need for
operative decompression and irrigation of the septic hip.
With any prosthetic joint in which infection is a concern, erythrocyte
sedimentation rate (ESR) and C-reactive protein (CRP) need to be
checked in addition to a complete blood count (CBC). ESR above
30 mm/h and of CRP greater than 1 mg/dL should raise suspicion for
prosthetic joint infection. As in native hips, aspiration of the joint with
cell counts is the gold standard for diagnosis, however cell counts as low
as 1760 cells/μL are suggestive of a periprosthetic infection [ 2 ].
Differential It is important to consider crystalline arthropathy in the
differential diagnosis of a septic joint, as its clinical presentation is nearly
indistinguishable from that of a septic joint. Additionally, even if crystals
are seen on joint aspiration, in the scenario of high number of WBCs and
a high percentage of PMNs, the physician should consider the possibility
of a superimposed infectious process. Cultures should be followed for a
minimum of 3 days to rule out this possibility. However, if the suspicion
is high for an infection, one should expeditiously proceed with operative
treatment, i.e., decompression, irrigation, and debridement of the
infected joint.
Appropriate Treatment/Referral In any patient with an examination
concerning for septic hip, it is important to initiate an orthopedic
consultation immediately. A septic joint is considered an operative
emergency due to the unchecked inflammatory reaction that occurs as a
result of the infection within the joint space. Metalloproteases and other