The
saphenous nerve, a branch of the femoral nerve, runs alongside the femoral
artery in the adductor canal. It pierces the deep fascia at the knee
posterior to the sartorius muscle and, accompanied by the great saphenous vein,
becomes superficial on the medial side of the knee.
A saphenous
nerve block in the region of the knee can be employed for superficial surgery
on the medial aspect of the leg, as in skin grafts, saphenous vein harvesting
or debridement of ulcers in the distribution of the nerve. The saphenous
nerve block can be used for pain relief of ulcers and as part of an ankle
block.
Position. The patient lies in a supine position
with the thigh externally rotated and the leg flexed 90E at the knee joint
(tailor's position).
Procedure. The sartorius tendon, the medial condyle of the
femur and the great saphenous vein provide landmarks indicating the entry,
which is situated on the medial side of the knee 2.5 cm above a line drawn
through the joint.
After local
infiltration at the point of entry, the needle penetrates the skin and
superficial fascia, thereby eliciting paresthesia on the medial aspect of the
leg. A dose of 5-8 ml local anesthetic solution is injected at the site
at which paresthesia is noted. The area around the great saphenous vein
is infiltrated with up to 10 ml local anesthetic solution to a depth of about
0.5 cm from the skin.
Phlebitis,
infection at the site of entry, or septicemia contraindicate performance of a
saphenous nerve block.
Infection,
hematoma and neuritis are possible complications with this type of block.