Overview

The technique for ipsilateral lumbar transfacet fixation (ILTF) was first described by King in 1948. It was modified in 1959 by Boucher, who reported the results of transfacet fixation that used longer screws to obtain primary fusion in the lumbosacral spine. In 1984, Magerl described another open technique for transfacet fixation in which screw entry starts in the contralateral lamina and then passes through the ipsilateral facet joint. Numerous clinical studies describe the outcomes of open transfacet fixation. However, pedicle screw fixation, first introduced by Roy-Camille in 1963, has become the standard for stabilization of the lumbar spine and is used much more commonly than open transfacet fixation.

The advantage for transfacet fixation is the smaller footprint required for insertion, which increases the bony surface area available for fusion and provides the potential for percutaneous insertion. Standard placement of pedicle screws requires a significant amount of soft-tissue dissection, which can increase the morbidity associated with the procedure. Additionally, exposure of the cephalad facet joint capsule introduces the potential for disruption, which may lead to adjacent segment degeneration. Ipsilateral transfacet fixation provides an alternative method for posterior stabilization following an anterior interbody procedure, especially because the failure of fusion of stand-alone anterior lumbar interbody fusion (ALIF) has been reported to be up to 24%.

Translaminar facet screws have been shown in biomechanical studies to be equivalent to pedicle screws in resisting motion in all three planes when used with a load-sharing interbody implant. Studies that compare transfacet to pedicle screw fixation following ALIF show similar load fluctuations in the disk space in a one-level interbody fusion and equivalent biomechanical properties in two-level interbody fusions. Translaminar facet screws have been shown to provide added construct stability for resisting extension and axial rotation when combined with anterior interbody fusion. The stability of transfacet fixation is not compromised after repetitive cycling in biomechanical studies.

Best and Sasso compared clinical outcomes of transfacet fixation versus pedicle screw fixation as an adjunct to anterior interbody fusion for patients with diskogenic low-back pain and found that transfacet screws required less operative time, less blood loss, and fewer additional operations for hardware removal. Tuli and colleagues demonstrated decreased hospital stays when comparing translaminar fixation with pedicle constructs.

Transfacet fixation serves as an alternative method for posterior stabilization as an adjunct to anterior interbody fusion with the potential advantages over pedicle screw fixation of less dissection, a lower profile, less blood loss, reduced cost, reduced operative time, and shortened hospital stay. Familiarity with multiple techniques provides the spinal surgeon with options for the many different scenarios encountered both in primary, revision, and salvage scenarios.

Anatomy Review

When placing transfacet screws, a variety of options are available. These include direct facet fixation or translaminar fixation, which can be done through an open or minimally invasive percutaneous approach.

The standard approach for open placement of transfacet fixation is the posterior midline approach. The extent of the dissection is less than what is commonly done for pedicle screw placement. It is important to remember that the spinous process and lamina are contiguous with the inferior facet and serve as a guide or reference point for translaminar facet screw placement. Likewise, the superior facet is continuous with the pedicle and transverse process of the caudal level ( Fig. 49-1 ). When considering open or less invasive techniques, it is important to have an understanding of the orientation of the facets throughout the lumbar region. Figure 49-2 demonstrates the variation in facet joint surface angle for each level in the lumbar spine. Because of the sagittal orientation angle of the facets at L1–L2 and L2–L3, placement of direct facet screws is challenging. Likewise, the coronal orientation of the L5–S1 facet creates difficulty in placing translaminar facet screws.

Anatomic model demonstrates the ideal starting point for an ipsilateral L5–S1 transfacet screw, starting in the middle aspect of the inferior facet and angled as close to perpendicular to the joint as possible.

Average angles of the surface of the facet joint relative to the spinous process throughout the lumbar spine.

Indications

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  Adjunct to stable anterior column (interbody fusion or significant degenerative disc disease)

  
  
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  Posterior fusion (without neural decompression)

  
  
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  Salvage procedure when pedicle fixation is not an option

  
  
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  Cephalad adjacent-level fusion: allows for additional level of fusion without having to remove adjacent pedicle screw-and-rod construct

Contraindications

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  Inadequate bone stock

  
  
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  Deficient posterior elements

  
  
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  Concomitant neural decompression (laminectomy or facetectomy)

  
  
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  Isthmic spondylolysis

  
  
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  Degenerative spondylolisthesis higher than grade II

Operative Technique

Technique

Open Technique Direct Facet Screw Placement

The dissection is limited to the level of interest. The spinous processes, laminae, and facet joints are exposed in their entirety. For a single-level fusion at the L3–L4 level, the spinous process and lamina of L3 and the L3–L4 facet joint are exposed. Care is taken not to disrupt the facet capsules cephalad and caudad to the level of interest. If a decompression is required at the same level, the surgeon must preserve an adequate amount of the facet to allow for fixation. An alternative would be to place the facet screws before decompression.

The facet capsule is opened, and the cartilaginous surfaces of the respective facets are removed. This can be done with a high-speed burr or a curette. After decorticating, the space is packed with bone graft material.

For the direct approach, the trajectory starts at the junction of the pars interarticularis and the inferior facet (see Fig. 49-1 ). The goal is to ultimately place the screw perpendicular to the joint surface, with final purchase into the bone of the adjacent pedicle. Remember that each level has a different orientation of the facet surface (see Fig. 49-2 ). A 3.2-mm drill bit, 4.5-mm tap, and 4.5-mm cortical screw are used for this technique. This screw can be placed as a neutralization screw or lag screw; if a lag screw is intended, overdrilling of the inferior facet is required.

Open Translaminar Technique

A similar approach is taken as previously described for direct facet screw placement. After achieving adequate exposure, the starting point is identified at the junction of the spinous process and lamina ( Fig. 49-3 ). A starting point is created for the screw at the spinolaminar junction using a 3.0-mm burr. A 3.2-mm drill bit is directed toward the contralateral facet joint, and care is taken to maintain a path within the cortices of the lamina. With an open technique, prevention of a breach is facilitated because the path can be directly visualized. A Woodson or Penfield instrument can also be used to palpate the ventral surface of the lamina to detect violation into the epidural space.

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