Page 86 - Clinical Manual of Small Animal Endosurgery

74 Clinical Manual of Small Animal Endosurgery

Fig. 3.10 A needle can be used to determine whether a coronoid
fragment is unstable.

directed on the tip of such a lesion, away from or towards the arthro-
scope, may reveal an unstable coronoid fragment disguised by overlying
cartilage (Fig. 3.10). Sometimes, directed pressure using a ‘banana’ knife
or a needle into such a fissure line dislodges a fragment that is lying
in situ. When the articular cartilage overlying a coronoid lesion looks
normal, gentle probing easily identifies diseased cartilage as abnormally
softened and gentle palpation of such cartilage often demonstrates its
fragility, displacing it from the diseased underlying bone. Cartilage dis-
placement or deliberate debridement reveals yellowed, relatively avascu-
lar subchondral bone. In such cases, current practice is to remove the
abnormal cartilage and the yellowed avascular bone using a hand burr
or a motorised shaver burr until healthy, bleeding subchondral bone is
reached (Fig. 3.11). The debridement instrument may need to be removed
intermittently and replaced with a probe while the joint is flushed to
remove the debris and to maintain a clear field of view. Temporary arrest
of irrigation enables evaluation of the subchondral bed to look for signs
of healthy, bleeding subchondral bone. Once all the diseased coronoid
subchondral bone is removed right up to the medial edge of the radial
head and there is a healthy bed of bleeding subchondral bone, then
healing takes the place through the formation of fibrocartilage which
covers the exposed vascular subchondral bone.
Histomorphometric studies and bone mineral density studies per-
formed on coronoid processes taken from dogs affected with coronoid
disease indicate that injury extends throughout the medial coronoid
process. Consequently, some workers advocate aggressive debridement
of the coronoid process to the level of three or four widths of the burr
(which is normally approximately 1 mm in diameter) below the height
of the radial head, attempting to achieve an arthroscopic subtotal coro-