Access with flexible cannulae.

Flexible access cannulae maintain a readily accessible tract for the efficient introduction and withdrawal of both straight and curved endoscopic instruments from skin to the parietes. Their main advantage is their capacity to deform, allowing the passage of curved instruments. Several designs of flexible access cannulae are currently available. The most practical design makes use of tightly coiled springs as tubes with or without silicone coating. A modification of this design uses wire woven into a tubular form and coated with silicone. Gas seal valves for these cannulae are currently primitive. The capacity of flexible access cannulae for deformation along the longitudinal and transverse axes could potentially be exploited for retrieval of small organs. Clinically, flexible cannulae have been used whenever curved instruments were needed. Coaxial curved and bayonet instruments have been used extensively in both thoracoscopic and laparoscopic operations. These instruments will allow an additional degree of freedom, that of the pre-formed curve of the instrument. In clinical terms this will facilitate the dissection, retraction and encirclement of tubular structures. In addition, the creation of intra-corporeal surgical knots is more efficient using curved needle holders.