Daniel Gastambide (Paris)
L'étage L5S1 a souvent une hernie discale mais son accès mini-invasif peut être gêné par la hauteur des crêtes iliaques. Le Dr Gastambide décrit ici les moyens d'effectuer une intervention dans ce cadre.
• Explain the aim of the sedation to the anesthesiologist, because sometimes, the drugs can have a paradoxical effect on the patient and make him agitated
• If possible, prescribe premedication yourself to the patient, thus, adapting the type of medication to his sensibility and to his degree of anxiety
• Prescribe antibiotics 24 hours prior to the operation, because the disk is white without direct vascularization, and antibiotics penetrate it very slowly
• You must have a good monitor,
• A good endoscope,
• Good tubes (adapting each one to the next, with a degressive length),
• Good forceps (Figs 7.11A and B) and a good C-arm with orthogonal views, a printer for the C-arm, an arthro-pump with an injectible serum
• Gentalline (40 mg/L) with adrenaline (half a mg/L).
The first reflex you have when you see a high iliac crest on an L5 – S1 hernia is to think you will operate it using a posterior approach. However, I personnally prefer to use a
percutaneous approach on a high iliac crest for two reasons:
• There is less risk of radicular lesion than in the case of an endoscopic interlaminar approach
• The endoscopic transforaminal technique is the most used for lumbar hernias for “endoscopist” surgeons.
You have to install the patient in a lateral position for several reasons:
• First of all, it is easier for the anesthesiologist to survey the patient
• This position is more comfortable for the patient
• You can try to open the intervertebral space by placing the contralateral external buttock in one of the operating table’s curves; a buttock under the flank is not usually tolerated
• Sometimes it is difficult to stabilize the knees with a cushion more so if the patient moves during the operation
• To avoid the patient moving during the operation, you can put a special band around him; however, by doing so, it could prove difficult to reposition the patient after
an unexpected displacement
• You may be tempted to ask the anesthesiologist to put the patient to sleep so he or she does not react to the nociceptive stimuli. However, by doing so, you would put the security of the operation at risk and can easily paralyse the feet elevators.
You have to evaluate the L5 – S1 slope on the lateral X-ray and CT scan. It’s often higher than 30 degrees and is high enough to insert the first needle. The skin landmarks have to be very precise. You have to penetrate the disk at an angle of 70 degrees to the sagittal plane. This means that you make two orthogonal marks with a metallic instrument using anteroposterior and lateral X-rays, projecting the tip of the instrument on the foramen. Of course, you must first inject the skin with lidocaine through a very thin needle. Then you insert the 18 G needle very slowly to spread the lidocaine on its way. After this you have to feel the anterior border of the facet’s capsule with the tip of this needle and then you slide along it, across the foramen until you feel you have reached the disk. If you want to make a local anesthesia in the epidural space, only use 0.5% lidocaine. This will create a hypoesthesia
without any motor deficits, and it is a secure method because the patient will react to the nociceptive stimuli.
This often shows where the hernia is. Having penetrated the disk with the 22 G needle, you will then be able to push the 18 G needle in a more precise and slightly curved trajectory around the 22 G in the disk. The bevelled tip of the 18 G needle often has to be axially rotated in order to obtain a smooth penetration in the disk without scraping the superior vertebral plateau. Then you pull out the 22 G needle and insert a thin Kirshner-wire with a rounded tip inside the 18 G needle. You pull out the 18 G needle, controlling on the X-ray monitor that you do not pull out the K-wire at the same time. Then, you push in the dilators. You can insert them into the disk at an angle of about 25 degrees. After having done this, you control that you have penetrated the disk and not the S1 bone. If the patient feels too much pain, you have to insert the endoscope to see the L5 exiting root which is often on the anterosuperior
side. Because of this, when you insert the bevelled dilator, you have to open the bevel in an anterosuperior direction to leave some space for the exiting root. You always have to check the exiting root through the scope. Then, you can use the last working tube with a rotating axial movement to smoothly push the exiting root away.
Variations of the Birth of Rami Communicantes
Sometimes this rotating movement can prove painful for the patient because of the thickness or adhesions of the ganglion (the anatomy of the anastomotic branches of the ganglion is essentially variable). Then you have to check the anterosuperior half of your view and smoothly slide your instruments along the posteroinferior rim of this exiting root. If you can push the working tube into the disk without creating any pain, you can use 4 – 5 mm forceps without scope to extract thicker fragments faster. Often at the end of the procedure and sometimes at the beginning, you can see the epidural fat or directly the dura mater which pulses at the same rhythm as the arthro-pump. Then you can verify whether the descending
root is free or not. If you fear that fragments have remained above, below, or behind the L5 or S1 wall, you can place one of your forceps jaws along the posterior wall to check that
there are not any other fragments behind the vertebra. X-ray control is always necessary. At the end of the procedure, you check that the hernia has been properly extracted by inserting the endoscope.