Septic
arthritis
Arthritis caused by sepsis is a rare but important surgical emergency.
Some organisms such as S. aureus may have a collagenase, which actually
dissolves the articular surface. If the joint is not sterilised within 24—48
hours, irreversible damage will occur to the articular surface, which will
inevitably lead to aggressive arthritis and even ankylosis (fusion) of the
joint. Pus in the joint may interfere with the nutrition of the articular
cartilage, which has no blood supply itself but derives nutrients from the
synovial fluid. In acute arthritis the rapid accumulation of pus leads to a
sharp rise in intra-articular pressure. This is extremely painful for the
Septic arthritis occurs most commonly in children but can also occur in
adults whose resistance to infection has been reduced, such as diabetics, and
can also occur after surgical intervention, such as arthroscopy. The onset is
sudden with extreme pain in the joint. The patient may have rigors and will
certainly feel shivery and generally unwell.
Examination
The joint may be red, hot and swollen, and held in the position of
comfort (see Table 24.1). However, the most characteristic feature is the
quite extraordinary amount of pain experienced by the patient when any attempt
whatsoever is made to move the joint. If the joint moves even 10 the patient
cries out with pain. If this sign is present, then both diagnosis and treatment
run hand in hand. The pressure in the joint needs to be relieved without delay
and the organism needs to be identified. Needle aspiration of the joint will
provide fluid for microscopy and culture and start the decompression of the hip.
In the child this will need to be done under a general anaesthetic, and is most
easily performed using an image
Late
diagnosis of septic arthritis
In immunocompromised patients the symptoms of septic arthritis may not
be so florid, and initially the diagnosis may not be suspected. If it is likely
that septic arthritis has been present for several days, then it is unlikely
that the infection can be brought under control without a synovectomy, and the
prognosis for the joint is poor. It should be splinted in a position of best
function, as a painless arthrodesis will be the best outcome that can be hoped
for. The position of function is not the same as the position of comfort, and
therefore the joint will need careful splintage. After acute septic arthritis
there is usually bony ankylosis. This provides a stable painless limb, but if
the ankylosis is not solid, or if the joint has fused in a poor position, a
formal arthrodesis may need to be performed once the infection has been brought
under control. This operation will need to be covered with antibiotics, as it
may produce a further recurrence of septicaemla.