Page 97 - Clinical Manual of Small Animal Endosurgery

Operative Arthroscopy 85

tilting combined with caudal rotation of the light post allows examina-
tion of the structures caudal to the scope entry point. The lateral joint
capsular structures are challenging to view because they are adjacent to
the arthroscopic portal and care should be taken to avoid inadvertent
removal of the scope during this examination.
Joint capsule and ligament tears may be partial or complete and the
severity of a tear may influence the method of treatment for restoring
joint stability. A partial tear may be treated by thermal contracture, using
a radiofrequency probe (Fig. 3.14b) to contract the remaining intact but
lengthened tissue adjacent to the tear (O’Neill and Innes, 2004; Cook
et al., 2005b). Complete tears in the medial glenohumeral ligament have
been treated by thermal contracture of the medial joint capsule, aiming
to restore joint stability through capsular contracture alone. However,
in such cases of marked laxity of the medial structures of the shoulder
joint it is likely that extra-articular stabilising structures of the medial
aspect of the shoulder are also compromised and the efficacy of treatment
using intra-articular thermal shrinkage alone may be insufficient. Con-
sequently, consideration should be given to performing open surgery,
repairing torn or stretched structures. Imbrication of the subscapularis
tendon of insertion and placement of prosthetic ligaments anchored to
anatomic sites of origin and insertion have each been described for the
successful management of medial instability of the shoulder joint (Pettitt
et al., 2007). Biceps tendon transposition is also a useful and effective
technique to restore medial shoulder stability. For radiofrequency-
induced thermal capsulorrhaphy, different techniques for application of
the heat source to the soft tissues are described, including ‘spot welding’,
‘paint brushing’ and ‘grid lining’. Thermal shrinkage procedures risk
thermal injury of articular cartilage and of peri-articular structures,
hence radiofrequency surgery must be performed in a carefully controlled
manner, following guidance specific to the model of equipment and for
the radiofrequency probe used. High flow rates of irrigation fluid are
indicated to try to prevent excess heating of the articular environment,
since cartilage damage occurs at temperatures of 45°C and above (Horst-
man and McLaughlin, 2006).
Following thermal contracture, the treated tissues are mechanically
weakened for at least 4 weeks and it is essential to prevent normal physi-
ological loading of the tissues, which would risk stretching or tearing.
Prevention of tissue loading during the recovery period is best achieved
through using a non-weight-bearing sling or custom-made jacket that
keeps the treated limb off the ground. Following removal of the non-
weight-bearing device, re-introduction of limb use and of activity must
be strictly controlled during the following weeks of the tissue remodelling
and healing to prevent injury and stretching or tearing of the contracted
tissues.
Lateral glenohumeral ligament injury and tears to the lateral aspect of
the shoulder joint are encountered less frequently than injuries to the
medial support structures. Resolution of shoulder pain and lameness has