Percutaneous Pedicle Screw Fixation

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Chapter 30 Percutaneous Pedicle Screw Fixation

Sang-Ho Lee, MD, PhD, Won-Gyu Choi, MD, PhD, Sung-Bae Ban, MD

Anterior lumbar interbody fusion (ALIF) has advantages over other fusion procedures, such as shorter operating time, lower blood loss, and no epidural complications [1–6]. However, in the case of spondylolytic or degenerative spondylolisthesis at multiple vertebral levels, higher pseudarthrosis rates have been reported with ALIF [7,8].

Percutaneous pedicle screw fixation (PPF) was developed as a minimally invasive posterior augmentation for ALIF [9]. At present, the PPF technique has been applied to a wide range of fusion procedures, including mini–open transforaminal lumbar interbody fusion (TLIF) [10].

Advantages

The potential advantages of PPF are as follows [10–12]:

image Immediate spinal stabilization without the need for posterior decompression
image Preservation of the posterior spinal elements
image A small skin incision
image Less blood loss, paraspinal muscle damage, and postoperative pain
image Better cosmetic result

Indications

Currently, PPF has been applied to a wide range of procedures, TLIF, posterior lumbar interbody fusion (PLIF), and posterolateral fusion. PPF is most useful in the following minimally invasive lumbar fusion techniques:

image Mini–open TLIF, especially with the use of a tubal retractor
image Laparoscopic transperitoneal ALIF
image Mini–open retroperitoneal ALIF
image Minimally invasive PLIF

Contraindications

PPF should not be used in patients with the following conditions:

image Requiring more than three motion segments fixation
image Spondylolisthesis of severity greater than grade II
image Severe scoliosis
image Previous pedicle fixation

Preoperative preparation

image Computed tomography is used to ascertain the size of the pedicle and to plan the length and direction of the screw (Fig. 30-1).
image Dynamic studies, such as flexion and extension radiographs, are helpful in the evaluation of spinal stability, particularly in the patient with spondylolisthesis.
image For older women, a bone density study helps determine whether the bone mineral content is adequate for pedicle screw fixation. In patients with severe osteoporosis, vertebral augmentation by vertebroplasty is needed (Fig. 30-2).
image

Figure 30–1 Computed tomography for measuring the size of the pedicle and to plan for the length (both arrows) and direction of the screw. L, left; P, posterior.

image

Figure 30–2 Vertebroplasty can increase the pullout strength of the pedicle screw and can prevent the subsidence of the implant due to osteoporosis. Bone cement inserted at L5 and S1 vertebral bodies were confirmed at fluoroscopic AP (A) and lateral view (B).

Procedures

Until recently, difficulty was always encountered with percutaneous placement of connecting rods. The innovation of the CD HORIZON Sextant system (Medtronic, Inc., Minneapolis, MN) has overcome the need for open rod placement.

Procedure for Percutaneous Pedicle Screw in General

1. The patient’s written informed consent is obtained.
2. The patient is placed in a prone position with the abdomen free. The procedure is performed under C-arm (fluoroscopic) guidance.
3. The back is prepared and draped in a sterile fashion.
4. With a No. 11 scalpel blade, the surgeon makes a 15-mm-long incision for each screw over the spinous process at the level to be fused (Fig. 30-3).
5. A 14-gauge vertebroplasty needle is positioned with its tip on the lateral margin of the pedicle oval and advanced until the stylet tip has abutted the bone under anteroposterior view (Fig. 30-4).
6. The surgeon advances the needle through the cortex by tapping its back end with a mallet on a lateral fluoroscopic view. The lateral view shows the needle passing parallel to the superior and inferior edges of the pedicle. With the needle tip located on the posterior vertebral bodyline on a lateral view, the intrapedicular location of the needle is confirmed on the anteroposterior view (Fig. 30-5).
7. After confirmation of placement, the needle is advanced so its tip is at the junction of the middle and posterior thirds of the vertebral body.
8. The stylet is replaced by a 200-mm-long Kirschner wire, and then a series of sequential dilations is performed along the Kirschner wire.
9. With the Kirschner wire still in place, a hole is drilled in the pedicle with a 5.0-mm cannulated drill bit.
10. After removing the Kirschner wire, the surgeon places a long straight beaded-tip probe into the pedicle and evaluates the pedicle walls are for possible perforation.
11. The surgeon inserts a pedicle screw into the prepared hole using the same orientation as for the Kirschner wire and under fluoroscopic guidance.
12. The same procedure is repeated for the other target pedicles.
13. The surgeon makes a soft tissue tunnel that connects the two pedicle screw heads in a each side is made using a custom-made curved passer through the same stab wound and muscle layer (Fig. 30-6).
14. Then the surgeon inserts a longitudinal connector (rod or plate) and passes it firmly through both screw heads (Fig. 30-7).
15. Fluoroscopic confirmation of the connector passage through the screw heads is obtained in both planes to ensure proper positioning of the connector.
16. A locking bolt is introduced into the screw head through the same stab wound and is tightened under fluoroscopic guidance or direct vision with brief retraction of the stab wound. While tightening a screw-connector construct, the surgeon uses the remaining screw path to give anti-torque and some compression force.
17. The same procedure is performed on the contralateral side of the spine, after which all incisions are irrigated and closed.
18. Finally, only a single deep stitch is needed at each screw entry incision (Fig. 30-8).
image

Figure 30–3 Skin entry points are determined by placing a bone biopsy needle on the skin and 15-mm-long incisions for each screw are drawn at the level to be fused.

image image image

Figure 30–4 (A) Intraoperative photography during insertion of 14-gauge vertebroplasty needles toward the pedicles and vertebra bodies; (B) Confirmation of proper needle positions through whole length of pedicles on fluoroscopic lateral view; (C) Proper needle positions with their tips on the lateral margin of the pedicle oval and advanced until the stylet tip has abutted the bone under anteroposterior view.

image image

Figure 30–5 Pedicle screws are inserted into the vertebral bodies at L4 (A) and L5 (B) along the Kirschner wire under the fluoroscopic guidance.

image

Figure 30–6 A soft tissue tunnel that connects two pedicle screw heads is made using a custom-made curved passer through the same stab wound and muscle layer.

image image image

Figure 30–7 A longitudinal connector (rod or plate) are inserted and passed firmly through both screw heads at one side (A) and contralateral side. (B) under AP fluoroscopic guidance. Proper position of connector is then confirmed by fluoroscopic lateral view (C).

image

Figure 30–8 A single deep stitch is needed at each screw entry incision.

Procedure for Use of the Sextant System

Patient Positioning and Operating Room Setup

1. The patient’s written informed consent is obtained.
2. The patient is positioned prone on top of a chest roll with the abdomen free. Chest rolls are radiolucent and do not disturb the movement of the operating table.
3. Before skin preparation and draping, it is important to determine whether adequate anteroposterior and lateral fluoroscopic images of the lumbar spine can be obtained.
4. The patient is placed so that the vertebral level to be operated is over the joint of the table, in order to make the proper lumbar lordotic curvature with movement of the table (Fig. 30-9).
image image

Figure 30–9 The patient is positioned prone on top of a chest roll with the abdomen free (A) and bending the operative table can provide a more lordotic curvature position (B).

Fluoroscopy for Percutaneous Pedicle Screw Fixation

It is essential to obtain true lateral and AP images. Even slightly oblique projections can mislead the surgeon, potentially leading to screw misplacement. Unfortunately, the quality of these views can be adversely affected by spinal deformity, obesity, and osteopenia.

Procedure for Percutaneous Pedicle Screw Fixation

1. The pedicle position is drawn with a sterile marking pen on the skin under fluoroscopic guidance (Fig. 30-10).
2. The exact skin entry point depends in part on the type of minimally invasive fusion procedure being performed. The skin entry point is placed 1 to 2 cm lateral to the pedicle point, to provide a trajectory that follows the lateral-to-medial angulation of the pedicle.
3. The two entry points are at a significant enough distance from each other that two separate 15-mm incisions are created. However, at the lumbosacral junction and in case of spondylolisthesis, the entry points can be quite close, and a single 25-mm incision is used for both levels (Fig. 30-11).
4. A tap needle is passed through the skin until its tip reaches the junction of the facet and transverse process under fluoroscopic guidance. This operative step is very important for proper pedicle screw placement. The surgeon should be careful to avoid injury of the facet joint on the upper levels (Figs. 30-12 and 30-13).
5. Owing to the gradient on the intersectional surface of the facet and the transverse process, the surgeon sometime encounters difficulty in placing the needle tip on the ideal starting point. Therefore, it is recommended to place the needle tip initially on the cortical bone vertical to the site. This maneuver makes it easier to advance the tip into the cancellous bone, which is parallel to the pedicle.
6. The pedicle is tapped with the cannulated tap, and the tap itself can be stimulated to assess for pedicle wall breach as well (Fig. 30-14).
7. Placing all needles before moving on to the next step makes placement of needles to the second pedicle easier. Also, when we insert the needle on the opposite side, the views are only minimally disturbed by the initial screw.
8. Once the needle has safely entered the vertebral body, the inner trocar is removed and a Kirschner wire is inserted through the needle lumen and into the vertebral body (Fig. 30-15).
9. The sequential dilators are placed over the guidewire to expand the path through muscle and fascia. This procedure provides a path of the appropriate space and avoids a tissue injury.
10. After removal of the last dilator, the entire screw-extender assembly is placed over the Kirschner wire, and the screw is inserted into the pedicle under fluoroscopic guidance (Fig. 30-16). Once the screw has reached the vertebral body, the wire is removed to prevent inadvertent advancement of the assembly.
11. The second screw is inserted to approximately the same depth.
12. Rotate the extenders so the two flat sides are facing each other. There is no gap between the two extenders. This is known as “mating” of the screw extenders. The external alignment of the screw extenders causes the screw head to be aligned internally and ready for insertion of the rod (Fig. 30-17).
13. A trocar tip is attached to the rod inserter before passing the rod (Fig. 30-18). After the insertion of a trocar tip, one should confirm if the trocar tip is firmly fixed to the trocar inserter.
14. After insertion of the rod into the second screw head, lateral, oblique, and anteroposterior fluoroscopic views are obtained to verify that the rod is properly positioned into the screw heads (Fig. 30-19).
15. Appropriate forces with compression or distraction can be applied to the construct prior to final tightening (Fig. 30-20).
16. Final tightening is performed with the plug driver. The rod inserter serves as the counter-torque device (Fig. 30-21).
17. When the rod is disconnected from the inserter, a percutaneous rod and screw construct is left in place (Fig. 30-22).
image image image image

Figure 30–10 Fluoroscope-guided drawing for the exact skin entry point. The midline through spinous processes are confirmed (A) and imaginary lines connected lateral pedicle margins are drawn at AP fluoroscopic view (B). The lines which are parallel to center of pedicles are confirmed at lateral fluoroscopic view (C). The skin entry points are placed 1 to 2 cm lateral to the pedicle point (red circles) to provide a trajectory that follows the lateral-to-medial angulation of the pedicle (D).

image

Figure 30–11 A 15-mm skin incision is made at each entry point.

image image

Figure 30–12 The tip of the tap needle should be placed on the lateral border of the pedicle because it helps avoid the superior facet and provides conversion of screw direction. The proper position of needle is confirmed at fluoroscopic AP (A) and lateral view (B).

image

Figure 30–13 As the needle reaches the pedicle–vertebral body junction on a lateral fluoroscopic image, the tip should be positioned in the center of the pedicle on an anteroposterior image by pushing the needle toward spinous process (arrow).

image

Figure 30–14 The pedicle is tapped with the cannulated tap needle. Intraoperative view (A) and fluoroscopic lateral view (B).

image image

Figure 30–15 Insertion of the Kirschner wire through the needle lumen into the vertebral body by fluoroscopic AP (A) and lateral view (B).

image image

Figure 30–16 After removal of last dilator, the entire screw-extender assembly is placed over the Kirschner wire (A) and the screw is inserted into the pedicle under lateral fluoroscopic guidance (B).

image

Figure 30–17 Rotation of the extenders so that the two flat sides are facing each other makes no gap between the two extenders.

image

Figure 30–18 The trocar tip being attached to the rod inserter before passing the rod.

image image

Figure 30–19 After insertion of rod into second screw head, lateral (A) oblique, and anteroposterior (B) fluoroscopic views are obtained to verify that the rod is properly positioned into the screw heads.

image image

Figure 30–20 Appropriate forces with compression (A) or distraction (B) can be applied to the construct prior to final tightening.

image

Figure 30–21 Final tightening is performed with the plug driver. The rod inserter serves as the counter-torque device.

image

Figure 30–22 The rod is disconnected from the inserter; a percutaneous rod-and-screw construct is left in place.

Limitations of the Sextant System

image It is impossible to use in cases involving more than two levels.
image It is used only for lordotic nature, not compression nature.
image It is a lengthy procedure with increased radiation exposure.
image Checking for a proper insertion track can be achieved only on a fluoroscopic image.
image Bicortical screw fixation is difficult at the S1 level.

Modified methods allow for these limitations

image An adjuvant instrument, such as an awl, T-probe, or long, straight, beaded-tip probe, can be used for checking the wall of the body (Fig. 30-23).
image An awl is placed on the junction of the facet and transverse process under fluoroscopic guidance. The tip of awl should reach the pedicle–vertebral body junction on the lateral view, and it should be positioned in the center of the pedicle on the anteroposterior view (Fig. 30-24).
image The awl technique (omitting the needling and dilator procedure) is time efficient, and with this technique, it is possible to perceive the bony entry point and to pass through the pedicles more easily than in the original Sextant procedure.
image A long, straight, beaded-tip probe (wall checker) is inserted into the pedicle and vertebral body. The wall checker is used to palpate the bony surface of the pedicle for proper insertion of the screw and to prevent screw misplacement (Fig. 30-25).
image A T-probe is simple to operate and allows the user to control the location and the direction of the screw in the vertebral body. It is especially helpful for bicortical screw fixation at the S1 level.
image

Figure 30–23 Adjuvant instruments (from top to bottom): an awl, a long, straight, beaded-tip probe for checking the wall, and a T-probe.

image

Figure 30–24 (A) The awl is inserted from the skin incision. (B) The tip of awl should be positioned in the center of the pedicle on the anteroposterior image. (C) The tip of awl reaches the pedicle–vertebral body junction on the lateral fluoroscopic image. (D) A T-probe is inserted from skin incision. (E) The tip of probe should be also positioned in the center of the pedicle on the anteroposterior image.

image

Figure 30–25 A long, straight, beaded-tip probe (wall checker) is inserted into the pedicle and vertebral body. The wall checker is used to palpate the bony surface of the pedicle for proper insertion of the screw and to prevent screw misplacement.

Complications

Screw misplacement is a well-known complication of open pedicle screw placement, and it is certainly a potential problem in PPF (Fig. 30-26). Unlike with open surgery, there are no visible landmarks, and there is little palpation feedback during navigation of the pedicle. The surgeon must rely on the quality of the fluoroscopic images and his or her ability to interpret the images.

image

Figure 30–26 A case of screw which is misplaced into the spinal canal (A). Another complication is injury to the bowel or viscous structures by the guidewire which can slip forward if the screw and guidewire are not parallel (B).

Another complication is injury to the bowel or viscous structures by the screw or guidewire. For example, during insertion of the screw, the guidewire can slip forward if the screw and guidewire are not parallel.

CASE STUDY 30.1 Lytic Spondylolisthesis at the L4-L5 Level Corrected by Percutaneous Pedicle Screws Without Laminectomy

A 45-year-old woman experienced severe neurologic claudication in both legs. Magnetic resonance imaging and plain films demonstrated lytic spondylolisthesis at the L4-L5 level (Fig. 30-27A and B). The anterior lumbar interbody fusion with pecutaneous pedicle screw was performed without laminectomy. Postoperative radiographs confirmed no laminectomy, acceptable pedicle screw placement, good reduction of slippage, and increased disc height (Fig. 30-27C and D).

image image

Figure 30–27 Case Study 30.1: Lytic spondylolisthesis at the L4-L5 level demonstrated on preoperative lateral magnetic resonance image (A) and plain film (B). (C) Postoperative anteroposterior radiograph demonstrates no laminectomy and acceptable screw placement. (D) Postoperative lateral radiograph reveals good reduction of slippage and increased disc height. (E) Photograph taken 4 months after surgery showing 15-mm skin incisions for each pedicle screw.

CASE STUDY 30.2 Lytic Spondylolisthesis at the L4-L5 Level Corrected by Percutaneous Pedicle Screws Without Laminectomy

Magnetic resonance imaging and plain radiographs demonstrated that a 55-year-old woman had severe lytic spondylolisthesis at the L4-L5 level (Fig. 30-28A and B). The anterior lumbar interbody fusion with pecutaneous pedicle screw (sextant system) was performed without laminectomy. Postoperative radiographs demonstrated acceptable screw placement, good reduction of slippage, and increased disc height (Fig. 30-28C and D).

image

Figure 30–28 Case Study 30.2: Severe lytic spondylolisthesis at L4-L5 demonstrated on preoperative sagittal magnetic resonance image (A) and lateral plain film (B). (C) Postoperative anteroposterior radiograph demonstrates acceptable screw placement. (D) Postoperative lateral radiograph shows good reduction of slippage and increased disc height.

References

1 Lee S.H., Choi W.G., Lim S.R., et al. Minimally invasive anterior lumbar interbody fusion followed by percutaneous pedicle screw fixation for isthmic spondylolisthesis. Spine J. 2004;4:644-649.

2 Choi W.G., Lee S.H., Jung B.J., et al. Mini-open anterior lumbar interbody fusion and simultaneous percutaneous pedicle screw fixation for low-grade isthmic spondylolisthesis with leg pain. Korean J Spine. 2004;1:255-262.

3 Chang S.B., Lee S.H., Lee S.C., et al. Anterior lumbar interbody fusion with Chuinard & Peterson bone graft and posterior percutaneous facet screw fixation for post-discectomy pyogenic spondylitis. Korean J Spine. 2004;1:76-82.

4 Shim C.S., Lee S.H., Jung B.J., et al. Fluoroscopically-assisted percutaneous facet screw fixation following anterior lumbar interbody fusion. Spine. 2005;30:838-843.

5 Jang J.S., Lee S.H., Lim S.R. Guide device for percutaneous placement of translaminar facet screws after anterior lumbar interbody fusion: Technical note. J Neurosurg. 2003;98:100-103.

6 Jang J.S., Lee S.H. Clinical analysis of percutaneous facet screw fixation after anterior lumbar interbody fusion. J Neurosurg Spine. 2005;3:40-46.

7 Herkowitz H.N., Kurz L.T. Degenerative lumbar spondylolisthesis with spinal stenosis: A prospective study comparing decompression with decompression and intertransverse process arthrodesis. J Bone Joint Surg Am. 1991;73:802-808.

8 Fischgrund J.S., Mackay M., Herkowitz H.N., et al. Volvo award winner in clinical studies: Degenerative lumbar spondylolisthesis with spinal stenosis: A prospective, randomized study comparing decompressive laminectomy and arthrodesis with and without spinal instrumentation. Spine. 1997;22:2807-2812.

9 Lowery G.L., Kulkarni S.S. Posterior percutaneous spine instrumentation. Eur Spine J. 2000;1:S126-S130.

10 Jang J.S., Lee S.H. Minimally invasive transforaminal lumbar interbody fusion with ipsilateral pedicle screw and contralateral facet screw fixation. J Neurosurg Spine. 2005;3:218-223.

11 Kim D.Y., Lee S.H., Chung S.K., Lee H.Y. Comparison of multifidus muscle atrophy and trunk extension muscle strength: Percutaneous versus open pedicle screw fixation. Spine. 2005;30:123-129.

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