Page 44 - Clinical Manual of Small Animal Endosurgery

32 Clinical Manual of Small Animal Endosurgery

Fig. 2.1 A, 1.9 mm 30° oblique arthroscope; B, 2.4 mm 30° oblique
arthroscope.

transmit light from a light source down the arthroscope shaft, illuminat-
ing the subject area captured at the tip. Arthroscopes are characterised
by their diameter, their viewing angle and their working length.

Diameter
The most popular sizes of arthroscope used in small animal arthroscopy
are the 1.9, 2.4 and 2.7 mm arthroscopes (Fig. 2.1). In large joints in
giant-breed dogs, a 4 mm arthroscope can be usefully employed, since
for all sizes the larger the diameter of the arthroscope used, the greater
the field of view and the greater the illumination, hence the better the
visualisation. Conversely, the smaller the arthroscope, the more limited
the view and the greater the fragility of the arthroscope. For this reason
great care must be taken when using the smaller arthroscopes to prevent
damaging them during use and handling.

Lens angle and viewing angle
The lens angle is the angle between the axis of the arthroscope and the
centre of image visible at the tip of the arthroscope. For most applica-
tions of small animal arthroscopy, it is helpful to use an arthroscope that
has a 30° viewing angle, such that the centre of the image viewed is 30°
away from ‘straight ahead’. The 30° arthroscope facilitates a large area
of view by rotation of the arthroscope about its length. In this way, a
large area is viewed without changing the direction and position of the
arthroscope within the joint. The field of view at the tip of the arthro-
scope is determined by the size of its objective lens, which is a function
of the diameter of the arthroscope. Smaller-diameter arthroscopes have