All contained disk herniations (DHs) and extruded fragments between the midline and the medial border of the pedicle. In relation to the disk space, the fragments may be caudally or cranially extruded. In the latter case, the translaminar approach is preferred.

DH combined with central/recess stenosis or with asymptomatic segmental instability.

Recurrent DH.

Foraminal or far lateral DHs which are located lateral to the lateral border of the pedicle

Optional in first surgery cases, provided that the MRI investigation encloses a coronal slice (scoliosis!). Mandatory (1) in recurrent DHs cases to evaluate bony defects and (2) whenever MRI leads to suspect a bony abnormality (spina bifida, pars interarticularis defects)

Sagittal slices: Contained disk herniation (DH) or extruded fragment? Caudal or cranial (suitable for translaminar approach) fragment dislocation? Mid-vertebral body herniation (halfway between two disk spaces)? Foraminal slice: Black neuroforamen? Extraforaminal slice: Disk fragment still apparent? Axial slices: Axillary disk fragment? How much of the DH is underneath the thecal sac, intraforaminal or extraforaminal (Fig. 18.2)? Pseudomeningocele in recurrent disk surgery? Coronal slices: Which approach for combined intra- and extraforaminal DH? Gadolinium-enhanced slices: Amount of scar tissue on the way to and into the spinal canal? Differentiation between recurrent DH and scar tissue?

Second choice whenever MRI contraindicated or not available. Disko–CT (diskography + CT): helpful in suspected extraforaminal DH. CM–enhanced CT: indicated for recurrent disk and differentiation between intraforaminal DH and neurinoma

The patient is placed prone on the Wilson frame. Advantages: Hip and knee joints are only moderately flexed, especially important in obese patients. The lordosis of the lumbar spine should be reduced as required by increasing the height of the arches. The distance between the laminae can be adjusted according to the size of the patient in order to allow a free-hanging abdomen to reduce bleeding (Fig. 18.3).

The head is positioned into a ProneView mask (Manufacturer: Dupaco Inc, Oceanside, California, USA). Eyes, nose, and chin are protected: The anesthesiologist is able to check them intraoperatively by use of a mirror (Fig. 18.3).

For safety reasons the patient is secured with a belt on the gluteal area: This becomes helpful when the OR table has to be tilted away from the surgeon, e.g., in dealing with extraforaminal or far lateral disk herniations (EFDHs).

The OR table is tilted until the lumbar spine is parallel to the floor.

X-ray localization: A 2 cm skin incision does not allow a “seek and find” surgery. Therefore the correct X-ray localization of the surgical target area is of paramount importance. The needle is always inserted contralateral to the intended surgical side in order to avoid subcutaneous or intramuscular hematoma and off the midline in order to prevent inadvertent CSF leakage. The needle is perpendicular to the target area (and to the floor): Soft tissue dissection is easier straightforward down. Even small oblique deviations can lead to the wrong level, especially in obese patients. The needle should point to the equator of the target disk. With increasing experience, the surgical field may be narrowed further to only the extruded disk fragment.

Prophylactic antibiotic coverage (e.g., cephazoline 2 g) 30 min before skin incision

Muscle: (SP) Paramedian retraction of the paravertebral muscles from the interspinous ligament. Sharp dissection of the rotators from the lower rim of the superior lamina and from the facet joint capsule. Insertion of a miniaturized speculum-counter-retractor system (Fig. 18.1c; manufacturer: Medicon, Tuttlingen, Germany).

(TM) Blunt splitting with the index finger until the lamino-facet junction can be palpated. Opening of the muscular corridor with miniaturized muscle retractors or with a dilator. Insertion of an expandable tubular retractor (Fig. 18.1e; manufacturer: Medicon, Tuttlingen, Germany) of 15 mm or 18 mm diameter. Both the speculum and the tube may be secured to the OR table with a self-holding arm nicknamed the “snake” (Fig. 18.1e).

Management of the DH: The local anatomy will dictate the necessary steps. Usually, a gentle dissection between root and disk material is accomplished first. In our experience the root retraction is performed intermittently with a flat sucker rather than with a conventional root retractor. Free disk fragments are removed with miniaturized forceps (Fig. 18.1b, manufacturer: Medicon, Tuttlingen, Germany). If indicated, the annulus is split bluntly with the dissector or with a scalpel and further disk material is removed. In the authors’ experience, additional diskectomy is performed in 20–30 % of the cases.

The disk space, when opened, is rinsed with normal saline. The opening of the annulus is closed with a collagen sponge coated with fibrinogen and thrombin (Tachosil®, manufacturer: Behring, Marburg, Germany). The epidural fat is mobilized in order to cover the root. Careful hemostasis goes along with closure by layers.

Cranially extruded disk fragments pushing the exiting root against the lower rim of the pedicle. Usually they are located within the root canal between two lines marking the medial and lateral border of the superior facet.

Recurrent cranially extruded disk fragments of DH previously removed via an interlaminar approach.

Lack of an adequate bony lamina, e.g., severe spinal canal stenosis and spina bifida

MRI (sagittal slices): Measure the distance between the upper border of the disk space and the lower rim of the cephalad pedicle. The translaminar hole will be centered on the halfway of this distance. Axial slices: Look at how much of the bulk of the DH is underneath the thecal sac and how much is lateral of it or even intraforaminal. The translaminar hole is centered on the lateral border of the dural sac.

Basically the same as for the interlaminar approach.

Important: The target lamina should be parallel to the floor! This may require the surgeon to tilt the OR table in a reverse-Trendelenburg position. The advantages of a horizontal target lamina are twofold: The placement of the retractor blade and the drilling of the hole become easier (see Figs. 18.6 and 18.7).

Radiographic localization: The needle should point to the largest portion of the DH which is usually halfway between the upper border of the target disk and the lower rim of the cranial pedicle. At the beginning of the learning curve, these landmarks may be labeled on the skin incision centered in between.

The lamina can be approached via a subperiosteal (SP) or a transmuscular (TM) route. The soft tissue approach mirrors the interlaminar approach. Remember: The width and the overlapping of the lamina in relation to the disk space increase in the caudal-cranial direction, whereas the width of the isthmus decreases. This means that the translaminar hole will be more medially and more oval-shaped in the upper lumbar levels (Figs. 18.4 and 18.5).

Lamina: Irrespective of the type of retractor used, the lateral border of the lamina should be visible underneath the retractor valve. A dissector is placed onto the lamina where the bulk of the DH is suspected and a fluoroscopic localization is performed. At this point the lamina should have been tilted parallel to the floor, so that the high-speed cutting burr can be held easily perpendicular to the lamina. With slow circular movements, a round (L5) or oval-shaped (L4 and cranially) hole of about 10 mm in diameter is performed (Figs. 18.6 and 18.7). Three layers “white” (outer cortical bone), “red” (spongy bone), and “white” (inner cortical bone) will be drilled off. For the sake of safety, the inner cortical bone should be drilled with a diamond burr. Remarks: (1) At least 3 mm of the lateral border should be spared in order to avoid a fracture of the pars interarticularis (Fig. 18.6); (2) usually the translaminar hole is located just cephalad to the cranial insertion of the yellow ligament. So, after removal of the thin shell of inner cortical bone with small patches, epidural fat will appear.

Epidural dissection: Up and down dissection of the fat along the lateral border of the dura. That should be continued cranial up to the axilla of the exiting root.

Gelfoam soaked with a long-acting steroid to fill in the hole is optional, but should be avoided if the disk space has been cleared.

DH whose bulk is located at least two-thirds lateral to the pedicle

Foraminal DH located more than two-thirds inside the root canal