Page 134 - Canine Lameness

106 8 Diagnostic Joint Anesthesia

Box 8.1 Principals of Diagnostic Joint Anesthesia (DJA)
Use only for patients with obvious lameness.
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● Use sedation protocol A for stressed/anxious animals and A or B for calm animals.
Use 2% mepivacaine (20 mg/ml Carbocaine®) at 1.5 mg/kg. A total dose of 5 mg/kg per dog
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and 4 ml/joint should not be exceeded.
A 20% improvement in lameness is considered a positive response.
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Ideally objective gait analysis is used to evaluate response.
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False-negative and false-positive (due to diffusion of anesthetic or pain modulating effects
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of sedation) results are possible.

The most common joints where DJA has been applied to aid in lameness diagnosis have been in
the thoracic limb (Van Vynckt et al. 2012b, 2013). This is understandable due to the frequent dif-
ficulty in isolating the location and cause of thoracic limb lameness (as compared to pelvic limb
problems). However, DJA has also been used in all major canine pelvic limb joints (Van Vynckt
et al. 2012a). The utility of DJA as a diagnostic aid should not be underestimated as the sensitivity
and specificity of DJA has been shown to be up to 90 and 100%, respectively (Van Vynckt et al.
2012a). Therefore, the use of this technique can be a valuable clinical tool. However, as with many
diagnostic tests, understanding the potential limitation is critical. Most importantly, false‐negative
results have been reported in approximately 10% of dogs. Furthermore, in dogs with more subtle
lameness, the clinical interpretation of DJA is challenging due to the less significant degree of
improvement seen and the potential effects of sedation on lameness. However, in dogs with more
moderate‐to‐severe lameness, the degree of improvement after DJA is often more dramatic and
this makes clinical interpretation easier. Clinicians should consider these factors when performing
DJA as a diagnostic test and when evaluating the treatment response.

8.3 Sedation Protocols

While routinely performed in horses, we do not recommend performing DJA without sedation in
dogs. Sedation ensures a pain‐free, atraumatic joint injection, in a manner that reduces patient
stress during the procedure (Chapter 7). General anesthesia should not be performed because this
technique is employed as a diagnostic tool and patients are required to walk prior to and after injec-
tion to evaluate the efficacy of treatment.
Because DJA is a diagnostic test, unlike arthrocentesis, the choice of sedative agent(s) is a more
important clinical consideration. Ideally, an effective sedative, that also allows quick ambulation
and does not affect lameness interpretation, is used. Unfortunately, our understanding on how
sedative agents affect lameness in dogs (positive or negative) and ultimately how they may influ-
ence our clinical interpretation of DJA is limited. Currently, only one study has evaluated the effect
sedative agents have on lameness in dogs (Van Vynckt et al. 2011); it evaluated the two sedation
protocols outlined below and found both to be suitable for use with DJA:

8.3.1 Sedation Protocol A: Sedation with an α₂-Adrenergic Receptor Agonist
This protocol is based on one of the most common and familiar methods of sedation in small ani-
mal medicine. The clinical benefits include rapid and effective sedation as well as sedation reversal