Page 61 - Clinical Manual of Small Animal Endosurgery

Diagnostic Arthroscopy 49

Fig. 2.19 Before injecting local anaesthetic, joint fluid is withdrawn and
assessed.

• First, a needle (normally 22 or 19 gauge and 40–50 mm) is inserted
into the joint and joint fluid is aspirated and retained for assessment
(gross or cytologic) and the joint is distended by syringe with arthro-
scopic lavage fluid containing ropivacaine (dose as discussed above).
Thumb pressure is maintained on the syringe to maintain distension
of the joint while retaining the access to the joint cavity (Fig. 2.19).

• Second, the access point for the arthroscope is determined and con-
firmed by inserting a needle in the location and direction intended
for the arthroscope. When the correct location and direction are
identified, the needle enters the joint space, gliding between the
opposing two articular surfaces. It can be helpful to maintain this
‘locator’ needle in position to ensure subsequent correct position and
orientation of the arthroscope cannula and trocar. A stab incision is
made in the skin that follows the needle down to the joint capsule
and the arthroscope cannula with blunt trocar inserted is introduced
into the joint, following the same path as the locator needle (Figs
2.20 and 2.21). Correct insertion of the cannula is confirmed when
the trocar is removed and irrigation fluid egresses from the cannula.
The arthroscope is carefully inserted through the cannula, the Luer
lock is locked into position and irrigation fluid is connected to the
scope cannula, making the needle the egress cannula (Fig. 2.22). The
locator needle is removed, while the ‘distension’ needle is retained to
allow egress of fluid. It is often helpful to replace or augment the
distension needle with a larger needle (19–14 gauge) to provide a
superior fluid egress.
• Thirdly, the instrument portal is identified by insertion of a needle at
the appropriate location. Fluid egress occurs as the needle punctures