326 Surgical Treatment
the studies was specifically designed to address
this question. Prospective studies are, therefore,
needed to validate these findings.
Diagnosis
Even though SSI can occur up to a year postop-
eratively, most infections are diagnosed within
the first couple of months after surgery. In a
study of 1000 TPLOs, the average time between
surgery and diagnosis of infection was 25 days
(range 7–60 days) if the dogs were treated with
antibiotics postoperatively, and 18 days (range
7–30 days) for dogs that did not receive postop-
erative antibiotics (Fitzpatrick & Solano 2010).
Similarly, for TTA, the average interval was 42
days, with 67% of infections diagnosed before
30 days (Yapet al. 2015).
The infection can be localized around the sur-
gical implants and the osteotomy site or be
intra-articular, or both. Septic arthritis is rela-
tively infrequent and is present in roughly 10–
16% of infections (Priddyet al. 2003; Yapet al.
2015). Clinical signs vary, but are typical for
infection: Localized heat, redness, pain, or ten-
derness are usually present. The swelling and
bruising may be localized around the implant
or involve the entire distal limb. Excessive
incisional discharge may develop soon after
surgery in acute cases, while chronic cases may
develop draining tracts. Dehiscence of the inci-
sion, often to the level of the bone plate, can
also be observed. In some cases, systemic signs
such as depression and fever may be detectable
(Marchevsky & Read 1999; Thompsonet al.
2011). In most cases, increased lameness is evi-
dent. Animals affected with acute septic arthri-
tis often present with a severe lameness. How-
ever, low-level, chronic septic arthritis cases
may be presented with a less severe but lin-
gering lameness (Hillet al. 1999; Marchevsky &
Read 1999; Fitchet al. 2003).
Radiographic signs of infection are gener-
ally mild and non-specific unless the infection
is severe and chronic. Periosteal reaction and
radiolucency around surgical implants can be
observed in chronic cases, but are often absent
in the more acute cases (Trampuz & Zimmerli
2006; Yapet al. 2015). Joint effusion is often
detected in cases with septic arthritis (Fitchet al.
2003).
Arthrocentesis and analysis of synovial fluid
is a quick and reliable way to rule out joint
involvement. Care must be taken to avoid iatro-
genic contamination of the joint when perform-
ing the arthrocentesis. Aseptic preparation of
the skin is carefully performed and a puncture
site away from the site of infection is selected, if
possible. Septic arthritis is often associated with
a markedly increased synovial cell count con-
sisting primarily of neutrophils (Marchevsky &
Read 1999). In many cases, toxic changes to
synovial neutrophils are absent. Therefore, this
feature should not be used to rule out a sep-
tic process (Marchevsky & Read 1999). Aerobic
culture of the synovial fluid should be per-
formed. However, only 50% of the cultures
are expected to yield positive results (Mont-
gomeryet al. 1989; Marchevsky & Read 1999;
Clementset al. 2005; Scharfet al. 2015). Enrich-
ment in the blood culture medium as a way to
increased sensitivity of the cultures has been
recommended but has been met with mixed
results (Montgomeryet al. 1989; Marchevsky &
Read 1999; Scharfet al. 2015).
Deep aspiration of the fluid around the sur-
gical implant before surgery or intraoperative
tissue culture are the best ways of diagnosing
implant-associated infection (Trampuz & Zim-
merli 2006). Similar to synovial fluid, culture of
fluid from around the implant can have a low
sensitivity. Therefore, a negative culture should
not, by itself, rule out infection (Darouiche
2004). If necessary, sonication of the implant can
be used to increase sensitivity of the cultures,
but is not routinely available (Trampuz & Zim-
merli 2006). Because of the high incidence of
MDR bacteria (Nazaraliet al. 2015) it is essen-
tial to obtain culture and sensitivity panels.
Extended sensitivity panels may be required for
MDR bacteria. In the absence of a positive cul-
ture but clinical evidence of infection, empiri-
cal antibiotics can be administered based on the
best evidence of bacterial flora and resistance
patterns prevalent in each hospital.Treatment
Treatment will depend on the severity of the
infection, the location of infection, and the stage
of healing. Infections diagnosed early without
evidence of abscess formation are often initially