n v asi ve Spinal Sur ge r y Via P o s te r o la te ral Acc e ss I ns t rum e n t s and Sur g ical Appr o ach e s f o r Minimall yI 3

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Instruments and Surgical Approaches for Minimally Invasive Spinal Surgery Via Posterolateral Access

Parviz Kambin, MD

INSTRUMENTS

A variety of instruments have been marketed by at least five industries. All of them share the already published principles (1–4):

1. Precise positioning of needle or guide pin under fluoroscopic control in the triangular working zone.

2. Use of a blunt-ended cannulated obturator or soft-tissue dilator over the previously positioned guide pin. The blunt end of the obturator will have a tendency to bypass the traversing or exiting root as it descends toward the triangular working zone.

3. Final positioning of a working cannula that is passed over the previously positioned soft-tissue dilator.

The instruments include the following:

1. An 18-gage needle, 15 cm (6 in.) in length (Fig. 1).

2. A blunt-end cannulated obturator with a 4.9-mm outer diameter (od).

3. Cannulas: A number of cannulas are available and have been used by various surgeons for arthroscopic spinal surgery. The round universal cannula has a 6.4-mm od that provides an inner diameter (id) working area of 5 mm. Recently, a round, bevel-ended cannula has been introduced and utilized by some surgeons (T. Yeung, personal communication).

Two sizes of oval cannulas are available (Fig. 1): a cannula with a 6.4 × 10 mm od that provides a 5 × 8 mm id working area; and a larger oval cannula, primarily used for arthro- scopic anterior column stabilization, that provides a 10 × 5 mm id working area (4,5) (available from Stryker, Howmedica, Osteonics, Allendale, NJ).

I and others have used a series of telescoping oval cannulas (Fig. 2) in order to maxi- mize access to the intervertebral disc for the introduction of bone grafts. These cannulas were designed to fit within the dimensions of the triangular working zone. Because the height of the triangular working zone is somewhat limited by the height of the intervertebral disc, oval cannulas will not exert undue traction to the neural structures when it lies within the triangular working zone. A 10- and a 12- mm oval cannular jig permits parallel insertion of both a cannulated obturator and a half- or full-moon auxiliary obturator in preparation of insertion of 10- or 12-mm cannulas (Fig. 3A,B).

4. Triphens: Two sizes of triphens are available that can be used for annular fenestration or cutting and removing osteophytes. Both triphens fit within the lumen of the 5-mm cannula, which was previously described (Fig. 4). Three working scopes are available in 0, 8, and

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From: Arthroscopic and Endoscopic Spinal Surgery: Text and Atlas: Second Edition Edited by: P. Kambin © Humana Press Inc., Totowa, NJ

20 ° models. The working channel of these instruments accommodates small-caliber for- ceps, knives, curettes, a radiofrequency coagulator, and palpating instruments (Fig. 5).

5. Arthroscopes: A variety of 0, 30, and 70 ° arthroscopes are available for intradiscal and periannular surgery. These scopes may be used with the appropriate irrigation sheaths in conjunction with round or oval-shaped cannulas (Fig. 6).

6. Straight-upbiting and flexible-tipped forceps (Fig. 7).

7. Articulating suction forceps.

8. Deflecting tube that permits 40 ° dorsal angulation of the flexible-tipped forceps when it is fully inserted into the deflecting tube.

9. Variety of powered trimmer blades (disc shavers).

10. Monopolar or bipolar radiofrequency coagulator.

11. Video equipment that is available in most operating room settings.

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Fig. 1. Instruments for spinal surgery. Shown are from left to right a 5 × 10 mm id oval cannula, a 5 × 8 mm id oval cannula, a 5 × 5 mm id cannula, a cannulated obturator, an 18-gage needle, and guide wire.

Fig. 2. Schematic drawing of a series of telescopic cannulas.

Instruments and Surgical Approaches 51

Fig. 3. (A) Jig for insertion of two cannulated obturators in preparation of insertion of 5 × 10 mm oval cannula. (B) A cannulated obturator and a half-moon obturator are inserted into the intervertebral disc in preparation of insertion of a 5 × 8 mm id oval cannula.

Fig. 4. Shown are from top to bottom a 3-mm triphen, a 5-mm triphen, and a universal 5-mm-id

cannula.

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Fig. 5. Working-channel scope with a variety of instruments that can be used in conjunction with working scope.

Fig. 6. Three video discoscopes are available: 0, 30, and 70 °. The scopes are inserted into the scope sheath, which is used for inflow of saline solution. The scope and the scope sheath assembly fit within the lumen of the 5-mm-id cannula, as well as of the oval cannulas.

SURGICAL APPROACHES

A variety of approaches have been used to access the intervertebral discs and vertebral

bodies in the lumbar region. Selection of the surgical approach is largely dictated by the

site of the pathology and the experience of the operating surgeon with the particular

approach.

Instruments and Surgical Approaches 53

Fig. 7. Additional instruments used for arthroscopic and endoscopic spinal surgery. From top to bottom, upbiting forceps, straight punch forceps, deflecting tube and flexible-tip forceps, punch forceps, deflecting suction forceps, and a variety of trimmer blades (disco shavers).

Uniportal Approach

A 5 × 5 mm or 5 × 8 mm id cannula is commonly used for uniportal access to the her- niated disc fragments in the lumbar region (1,2,5) (Fig. 8A,B). A larger-diameter cannula may also be telescoped over the 5 × 5 mm id cannula to provide wider access to the inter- vertebral disc. A working channel scope is usually used with a 5-mm-id cannula. However, a 5 _× 8 mm id cannula provides additional advantages by simultaneously accommodating a 0 or 30° arthroscope, larger forceps, and resecting instruments (3–5) (Fig. 9A,B).

The uniportal approach is commonly utilized for retrieval of paramedial, small central, foraminal, and extraforaminal herniations (see Chapter 4). Uniportal use of a 5 mm id cannula also provides adequate access for a transforaminal approach to the spinal canal (see Chapter 4).

Bilateral Biportal Approach

In the bilateral biportal technique, two cannulas are inserted contralaterally from the

right and left sides of the intervertebral disc (Fig. 10A,B). A small cavity is created

posteriorly adjacent to the spinal canal by resection of nuclear tissue and torn fibers of

the annulus and the posterior longitudinal ligament. Communication between the right

and left portals is essential to establish free inflow of saline into one portal and outflow

from the opposite portal. A radiofrequency probe has been most helpful in vaporizing

nuclear tissue and establishing communication between the two portals (2,3,5). Adequate

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Fig. 8. (A) Properly positioned cannula at medial pedicular line for access to content of spinal canal at L2-L3 level; (B) lateral interoperative fluoroscopic view of position of tip of cannula adjacent to posterior boundary of L2-L3.

visualization is accomplished by insertion of a 70 or 90 ° arthroscope from one portal

and introduction of articulating or upbiting forceps from the opposite portal. The bilat-

eral biportal approach is suitable for removal of large central herniations and sequestered

nonmigrated disc fragments. Following retrieval of a sequestered disc fragment, the

ventral surface of the dura is usually visualized with the arthroscope that is inserted into

the intervertebral disc. Retrieval of a sequestered fragment from the spinal canal is usually

Instruments and Surgical Approaches 55

Fig. 9. (A) Interoperative fluoroscopic examination showing position of 5 × 8 mm id oval cannula at L5-S1 in anteroposterior projection. (B) Flexible-tip forceps and 30 ° arthroscopes are used in conjunction with a 5 × 8 mm id oval cannula for visualization and removal of larger disc fragments.

followed by a discharge of venous blood into the disc cavity. This blood has a tendency to coagulate when the instruments are removed.

In addition, bilateral biportal access is necessary for anterior column stabilization when a minimally invasive posterolateral approach is employed (see Chapter 5).

Unilateral Biportal Approach

In the unilateral biportal approach, two parallel or converging cannulas are positioned

in the triangular working zone with the aid of specially designed jigs. The two parallel

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Fig. 10. (A) Interoperative lateral fluoroscopic examination of biportal access to L3-L4 intervertebral disc. Note the posterior position of the instruments adjacent to the spinal canal.

(B) Anteroposterior fluoroscopic examination of position of cannulas shown in (A). Note that a

5 × 8 mm id oval cannula is used on the left and a 5-mm-id cannula on the right. The cannulas

are positioned for removal of a centrally located sequestrated disc herniation.

Instruments and Surgical Approaches 57

Fig. 11. Schematic drawing of unilateral biportal access to foramen utilizing specially designed jig.

Fig. 12. (A) Intraoperative endoscopic review demonstrating how high-speed diamond burr

is being used for laminatomy. (B) Intraoperative photograph following laminatomy and partial

facetectomy. Note the dural sac at the top of the photograph and the herniated disc in the axilla

of the traversing nerve root. (C) Schematic drawing of (B).

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Fig. 12. (Continued)

obturators then may be replaced with an oval-shaped cannula that provides wider access

to the intervertebral disc (4,5) (Figs. 1 and 3). The 5 _× 8 mm id cannula (Fig. 9A,B) is

suitable for intradiscal or subligamentous access to a disc herniation. It also may be

used for retrieval of extraforaminal and foraminal herniations. The 5 _× 10 mm id cannula

(Figs. 1 and 3A) is commonly utilized in the course of arthroscopic anterior column

stabilization. Two converging cannulas are useful for visualization and removal of

foraminal and extraforaminal herniations (Fig. 11) (5,6).

Interlaminar Access

Endoscopic interlaminar access to the content of the spinal canal and the lateral recess follows the principle of already established open operative procedures (see Fig. 18 in Chapter 1). Although originally my colleagues and I used a working cannula with a side window (3–5) for insertion of a straight arthroscope, with the availability of 45 and 90 ° angled arthroscopes (Figs. 3–5) in the pursuing years, we were able to introduce the arthroscope and resecting instruments directly from the proximal opening of the can- nula into the surgical field. We have used a high-speed diamond burr for laminatomy (Figs. 3–12A), and the retrieval of disc fragments has been similar to that of known tech- niques used during open procedures.

REFERENCES

1. Kambin P, Gellman H. Percutaneous lateral discectomy of the lumbar spine: a preliminary report. Clin Orthop 1983;174:127–132.

2. Kambin P. Arthroscopic microdiscectomy. Arthroscopy 1992;8:287–295.

3. Kambin P. Arthroscopic techniques for spinal surgery, in Operative Arthroscopy (McGinty JB, Casperi RB, Jackson RW, Poehling GG, eds.), Lippincott-Raven, Philadelphia, 1996, pp.

1215–1225.

4. Kambin P, Gennarelli T, Hermantin F. Minimally invasive techniques in spinal surgery:

current practice. Neurosurg Focus 1998;4(2):1–10.

5. Kambin P. Arthroscopic microdiscectomy, in The Adult Spine: Principles and Practice, 2nd ed.

(Frymoyer JW, Ducker T, Hadler N, et al. eds.), Raven, New York, 1996, pp. 2023–2036.

6. Kambin P. Unilateral biportal percutaneous surgical procedures and instrumentation.

US patent 5,395,317, October 1991.

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