Parasacral approach (according to Mansour)


Anatomical landmarks

Posterior superior iliac spine, ischial tuberosity, (greater trochanter)


Block technique

The parasacral block targets the sciatic nerve at its most proximal point where it induces fast and full anaesthesia. The block is performed with the patient seated or in the lateral recumbent position. We prefer the lateral recumbent position, given that, in combination with the psoas compartment block, the technique is especially suited for complex surgical interventions on the leg, and avoids the inconvenience of repositioning and re-draping of the patient between the two procedures. The side to be blocked is upward, the lumbar spine shows a kyphosis and the hip flexed to facilitate orientation. The posterior superior iliac spine and the ischial tuberosity are marked. From the posterior superior iliac spine, the palpating finger follows the tuberosity until no more bony structures are encountered. Here, approximately 5 – 7 cm caudad to the posterior superior iliac spine, the puncture site is marked. After disinfection and deep infiltration of the puncture channel, a stimulation needle of 80 –120 mm in length is advanced sagittally in the direction of the tuberosity until a stimulatory response is elicited from the peroneal or tibial part of the sciatic nerve. The amplitude is reduced accordingly down to the threshold current and 20 to 40 ml of local anaesthetic are injected. If no primary stimulatory response is achieved or bony resistance encountered, the insertion direction is corrected to the caudolateral (around to midline between greater trochanter and ischial tuberosity). Here, there will be no problems placing an indwelling catheter. Whilst contractions of the gluteal muscles are of no value, a stimulation of the ischiocrural muscle group is a promising response.