Destandau’s Technique: Interlaminar Approach (Lumbar Diskectomy with Canal Decompression)

19 Destandau’s Technique: Interlaminar Approach (Lumbar Diskectomy with Canal Decompression)

Shrinivas M. Rohidas

19.1 Introduction

Lumbar intervertebral disk prolapse is a common occurrence. The standard surgical treatment is diskectomy with a posterior approach. With the Endospine operating tube, the same approach and surgical technique can be used while reducing the size of the skin incision and approach-related tissue trauma, especially in obese patients. Endospine helps in any deeply located pathology in the lumbar spine, such as disk herniation, stenosis, and foraminal disk herniation. With Endospine, the surgeon’s eye is focused right inside the body close to the pathology that is to be treated. In addition to the cosmetic benefit of the reduced length of the incision, the short access route and reduced length of the incision help to decrease postoperative incision discomfort and aid in rapid resumption of routine activities.

19.2 Indications

The technique is indicated for lumbar disk herniation—central, paracentral, extruded, and migrated with neural compression and associated canal stenosis—not relieved by adequate conservative treatment. All levels from L5–S1 to L1–L2 can be approached with the technique. Central and far-lateral lumbar disk extrusions, as well as foraminal and extraforaminal disk extrusions, can be treated with Endospine. Canal stenosis in the lumbar region can be treated with a unilateral approach while achieving bilateral lateral recess and central decompression. The versatility of Endospine lies in its ability to treat various lumbar pathologies, including disk herniations of any kind, along with canal stenosis.1,2

19.3 Contraindications

Severe lumbar instability with radiculopathy.

19.4 Patient Positioning

Various patient positions can be used for lumbar diskectomy, such as the prone position, lateral position, and knee-chest position. The prone and knee-chest positions are the natural positions for use of Endospine. With the lateral position, it is difficult to support the Endospine system. The author uses the knee-chest position on a flat operating table with flexion at the patient’s knees and hips. In this position, the abdomen is completely lax in between the two thighs at the same time that there is adequate interspinous distraction, which is necessary in cases of canal stenosis. With a pillow under the patient’s chest, the head is lower than the caudal end, allowing natural gravitational venous flow toward the heart, which helps in minimizing venous bleeding (Fig. 19.1).³

Fig. 19.1 (a) Knee-chest position. (b) Knee-chest position showing completely lax abdomen between the two thighs.

19.5 Localization of Disk Space

When the surgeon limits the size of the incision, it is necessary to exactly localize the target disk space. Exact localization of disk space is performed with help of a localizing pin available in the Endospine set. The localizing pin is used in lateral fluoroscopy with the patient placed in the knee-chest position. The localizing pin moves in all three spatial planes, and only lateral fluoroscopy is necessary to confirm the direction to the disk space. The entry point is obtained while determining the direction to the disk space. Hence there is no need for separate anteroposterior and lateral localization (Fig. 19.2, Fig. 19.3).⁴

19.6 Surgical Technique

Skin Incision

While marking the disk space level in lateral fluoroscopy, the surgeon also determines the entry point in the coronal plane. The incision is ~ 10 to 15 mm from the midline spinous process. The length of the incision is ~ 15 to 20 mm. The fascia is cut in the same direction, and then the paraspinal muscles are separated off the midline from the spinous process and interspinous ligament with a 12-mm osteotome. Bleeding from retracted muscles is controlled with bipolar coagulation.

Fig. 19.2 Localizing pin with C-arm fluoroscopy in lateral view to localize the disk space.

Fig. 19.3 Lumbar localizing pin in Endospine set.

Fig. 19.4 Endospine set with routine spine instruments.

Fig. 19.5 Hand movements with Endospine.

The author uses two gauze pieces with thread to retract separated muscles laterally. One gauze piece is pushed cranially over the lamina and another is used caudally in a similar fashion. Then the outer tube of the Endospine is placed between the spinous process medially and the separated muscles laterally. The outer tube should fit snugly between the spinous process and muscle. With the outer tube in place, the surgeon should see the exposed lamina in the cranial half of the outer tube and the ligamentum flavum in the caudal half. Then the surgeon is assured of the exact localization of the concerned disk space.

Preparation of the Endospine Assembly

The Endospine outer tube and inner tube/working insert with routine instruments are arranged on an instrument trolley. Next, the inner tube/working insert of Endospine is placed in the outer tube and is fixed in the proximal position with the built-in lock. This has to be in the proximal position so that an artificial space is created between the outer tube and the inner tube/working insert. If the inner tube is placed more distally, then the endoscope will touch the underlying tissue and the surgeon will not have space for movement of the instruments. (This is one of the mistakes the surgeon faces during the learning curve.) Then the endoscope is placed in the endoscope channel and is fixed. Suction is used with the left hand through a 4-mm channel that is parallel to the 4-mm channel for the endoscope. The channel for working instruments is the widest channel in the Endospine system: 12 mm. The two 4-mm channels for the endoscope and suction are parallel to each other, but the channel for working instruments is at an angle of 12° to the two 4-mm channels. The 12° angle between suction/endoscope and working instruments avoids intermingling of the instruments, while at the same time allowing the surgeon to use a 0° endoscope as an angled scope (Fig. 19.4).

Fig. 19.6 Hand movements with Endospine.

Fig. 19.7 Hand movements with Endospine.

Basic Philosophy of Mobility and Stability of Endospine

When the endoscope and suction are attached to the camera and suction tube, respectively, the whole system should remain relatively stable without any pull over the cables. The suction in the left hand is used to move the whole system with the left hand. The working instrument in the right hand is used to move the system with the right hand. With both hands, the surgeon can move the whole system—i.e., endoscope and instruments—in all four directions, cranial, caudal, medial, and lateral. This means that, while using the Endospine system, the surgeon has to balance the forces of both hands so that the whole assembly can be moved in any direction. Thus, when the surgeon moves the Endospine system with suction in the left hand, the system is stabilized by the working instrument in the right hand (Fig. 19.5, Fig. 19.6, Fig. 19.7). Similarly, when the Endospine system is moved to use working instruments in the right hand, the system is stabilized by the suction in the left hand (Fig. 19.8, Fig. 19.9).

The surgeon has to look at the monitor while balancing Endospine with suction in the left hand and working instrument in the right hand. The surgeon has to learn the basic movements to balance and at the same time to stabilize the system (Fig. 19.10). These are the basics of mobility of Endospine.^4,5

Excision of Lamina

The excision of lamina is usually started at the spinolaminar junction at the base of the spinous process. A 45° Kerrison punch is used to excise lamina. Excision of lamina is continued laterally and cranially so as to detach the anteroinferior attachment of the ligamentum flavum from the lamina (Fig. 19.11, Fig. 19.12). Once the learning curve is mastered, the surgeon can change the approach according to the interlaminar and interpedicular window size.

For example, at the L5–S1 level, where the interlaminar window is wider, the surgeon can detach the ligamentum flavum first and then, if necessary, part of lamina is excised to decompress the traversing nerve root. Part of the cranial lamina and the articular process is excised to expose the lateral edge of the dural sac and the shoulder of the traversing nerve root.