Length of instruments

TTTS. Length of instruments

Adequate length of the trocar, endoscopes, and working instruments is paramount. In addition, the relationship between trocar length and endoscope length may vary between product companies. In one system, the endoscope and trocar are flushed at the tip, with a locking mechanism at the back end to prevent loss of fluid (hysteroscopic model). 

This system requires that the trocar and endoscope complex be moved back and forth within the amniotic cavity to reach the different vessels. In the endoscopes designed by Quintero (laparoscopic model), trocar length is always smaller than endoscope length. Fluid loss is prevented by a checkflow valve within the lumen of the trocar. 

The greater length of the endoscope allows surgery to be performed with decreased friction of the trocar against the membranes, as the trocar does not need to be advanced or retrieved within the amniotic cavity during the procedure. Endoscope length is critical for the adequate completion of the surgery. 

Ideally, the endoscope should span the entire amniotic cavity to reach all anastomoses, regardless of the point of entry into the amniotic cavity. Since fundal height can be as large as 40 cm in patients with TTTS, we have designed our endoscopes to reach that length. The trocar sleeve is approximately 4 cm shorter than the endoscope to allow freedom of the scope, but not much smaller, as it may be needed for assistance during surgery (see below).