Page 71 - Clinical Manual of Small Animal Endosurgery

Diagnostic Arthroscopy 59

should be further evaluated mechanically using an instrumented tech-
nique. The cranial aspect of the humeral head is most readily reached
using an instrument placed cranially. Sometimes the ingress needle can
be used for this purpose, despite the unfamiliar angulation of insertion,
if triangulation has been achieved. If the ingress needle is readily visible
and its direction is suitable, a cannulated instrument portal can be
created following the same direction into the joint. Instrumented inspec-
tion of the middle and caudal aspects of the shoulder requires a caudally
placed instrument portal. The optimal site for the caudal instrument
portal is caudal and slightly distal to the tip of the acromion. In a middle-
sized dog a needle is inserted into the shoulder joint approximately 2 cm
caudal to the distal tip of the acromion, aiming to place the needle tip
in the vicinity of the arthroscope tip, but avoiding crossing the arthro-
scope. For the novice arthroscopist, an aiming device is invaluable for
this triangulation. Once triangulation is achieved, an instrument portal
can be established following an identical path to the joint cavity. Thick-
ened cartilage should be probed to evaluate its integrity and adhesion to
underlying subchondral bone. If radiological investigation suggests the
presence of an osteochondrosis lesion, arthroscopically visible fissures
should be probed to check for the presence of an osteochondritis disse-
cans flap in situ.
Since shoulder disease is usually characterised by synovitis and syno-
vial proliferation that affects the entire joint, it is rare that arthroscopic
visual inspection detects only a single injured structure that is hyperaemic
or fibrillated or covered in proliferated synovium and consequently iden-
tifiable as the only cause of a painful shoulder. Consequently, instru-
mented evaluation of the shoulder joint is also useful for assessing the
integrity of the soft-tissue structures. When there is synovitis affecting
the biceps tendon, instrumented probing and manipulation of the tendon
can be helpful to reveal macroscopic tears in the tendon that are other-
wise not visible on the surface most readily viewed. Arthroscopic inspec-
tion and probing may identify tearing of the tendon fibres or adhesion
between the tendon and an inflamed and constricted bicipital groove.
The blunt probe is also useful to assess the mechanical integrity of the
other soft-tissue structures, including the glenohumeral ligaments and
the subscapularis tendon.
Due to the risk of accidentally removing the arthroscope, inspection
of the lateral aspect of the shoulder joint is performed at the end of the
arthroscopy. The arthroscope is returned to its insertion position and
slowly withdrawn from the joint while tilting caudally. Rotation of the
light post towards the patient’s shoulder joint directs the arthroscopic
view laterally within the joint. The lateral aspect of humeral head and
of the glenoid cavity are viewed and, in the background, the craniolateral
joint capsule and caudolateral joint capsule can be inspected with careful
manipulation of the arthroscope and light post. An alternative approach
to the arthroscopic inspection of the lateral joint compartments uses
an additional medially placed arthroscopic portal and a ‘hanging limb’