Page 138 - Canine Lameness

110 8 Diagnostic Joint Anesthesia

DJA has been reported to be 100% specific and 90% sensitive for the identification of joint pain
and lameness: Van Vynckt et al. (2012a) performed DJA in almost 200 dogs with thoracic or pelvic
limb lameness that was thought to be joint related. In that study, all dogs who received DJA in a
painful joint showed an improvement in lameness (100% specificity). Therefore, a positive response
clearly indicates that the infused joint is painful and contributing to the observed lameness.
However, 10% of lame dogs with a negative response to DJA (i.e. unchanged or worsening of the
lameness) were actually false negatives, meaning that the joint was the source of lameness based
on other diagnostics performed. Therefore, a negative response only indicates a 90% certainty that
the joint infused is non‐painful and not the source of lameness. As such, a negative response does
not completely rule out the treated joint as the source of pain and lameness in all cases. Negative
results should therefore be interpreted with caution and additional diagnostics should be utilized
if the clinician is suspicious that the result may be a false‐negative (rather than true negative)
result (Figure 8.1). Alternatively, additional joints can be tested using DJA. It is also possible that
specific joint disorders or pathology (such as pain originating from subchondral bone with intact
cartilage or severe arthritis) may be less responsive to DJA (Dyson 1986; Van Vynckt et al. 2010).
As mentioned above, a slight improvement in lameness may be attributed to the pain‐modulat-
ing effects of the sedation. While this response may be considered a false‐positive response, Van
Vynckt et al. (2012a) reported no false‐positive responses when using an improvement in lameness
by approximately 20% as the cutoff. While this has not been reported in dog studies, leakage of
anesthetic to surrounding extra‐articular structures as well as errors in lameness interpretation are
other reasons for false‐positive results in horses (Jordana et al. 2016).

References

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