Innovative use of Nitinol in
Laparoscopic Surgery
Desmond H. Birkett, Department of
General Surgery,
Lahey Clinic Medical Center,
Burlington, MA USA

Nitinol having the unique property of
returning to a preformed shape once a
deformation has been released, or the
deformation can be controlled by
changing the temperature of the metal.
These properties are used to great
effect in laparoscopy where access to
the peritoneal cavity is limited by
narrow straight rigid port placed across
the abdominal wall. As result, Nitinol
becomes an appealing technology that
has a significant future in minimal
access surgery. Her are a few examples
of how it is being used.

The current retrieval bags used for
removing specimens from the
abdominal cavity have Nitinol in the
necks of the bags to open them once
deployed into the peritoneal cavity.
This happens automatically and
permits the easy placement of
specimens into the bags. Nitinol has
been used in retractors which are
introduced straight and once in the
peritoneal cavity form a curve that is
them used to retract intra-abdominal
organs. Most instruments are straight
but Nitinol is used in graspers and
dissectors to deflect them once into
the peritoneal cavity. They are held
straight by a sheath which when pulled
back causes the tip to bend. The
deflection and therefore the angle and
positioning of the tips of the
instrument can be controlled by the
degree to which the rigid sheath of the
instrument is pulled back.

A new and very important use of
Nitinol is effect a bowel anastomosis.
This can be performed as an end to end
or side to side manner using a Nitinol
compression ring. Cooling the Nitinol
ring opens it so that it can be placed
across two ends of tissue. As the ring is
warmed up to body temperature it
closes compressing the bowel together,
holding it together so that it can heal.
The bowel that is compressed by the
ring becomes necrotic, thus freeing the
ring to that it can fall free into the
lumen of the bowel to be passed with
the feces. When performing a
laparoscopic hernia it is often difficult
to unroll the mesh that is being placed
for the repair. Nitinol has been placed
in the edge of the mesh so that as it is
unfolded it automatically opens up.

There are many other potential in the practice of minimal access surgery that
the unique properties of Nitinol can be
used to improve instrumentation.