Saphenous nerve block
Upper border of the patella, medial vastus and sartorius muscles Alternativ: Tub. tib., med. Kopf des M. gastrocnemius, Achillessehne
The Block Technique
The location between the medial vastus and sartorius muscles is palpated some 2 to 4 cm superior and medial to the patella, and puncture is carried out there with the stimulation cannula inserted perpendicularly to the underlying layer and into the sub-sartorial fatty tissue, where electrical paresthesia can be triggered with a pulse width of 1.0 ms if the patient is cooperative. 10 to 15 ml of local anaesthetic are then applied after corresponding reduction of the amplitude to 0.3 - 0.5 mA. In many cases, the saphenous nerve is still adjacent to a muscle branch of the femoral nerve, which in turn innervates the medial vastus muscle. In that case, the stimulation motor response from the medial vastus muscle can be taken as a promising sign. A catheter can be inserted without problems. An alternative technique which does not require patient cooperation is to carry out subcutaneous infiltration from the medial head of the gastrocnemius muscle to the tuberosity of the tibia. In principle, this infiltration technique is possible at any level of the medial lower leg, provided that infiltration from the Achilles tendon to the front border of the tibia is carried out distally.
Ultrasound-guided saphenous nerve block
The block of the saphenous nerve, which is basically the purely sensory end branch of the femoral nerve, is carried out about 10 to 15 cm above the knee joint on the medial thigh. A puncture level which seems suitable for this is the point where the nerve enters the adductor canal. On its distal path from the groin, the nerve runs alongside the femoral artery and femoral vein, lying against the long adductor muscle in the adductor canal and covered by the sartorius muscle. These structures normally make it possible to display its course as far as the puncture level quite successfully.