As described by Dr. Robert Cloward in 1953, posterior lumbar interbody fusion (PLIF) was originally performed using structural iliac crest bone graft and no supplemental internal fixation. Excellent results were reported with this technique, although these proved difficult to re-create in the hands of other surgeons. The technique experienced a resurgence in the late 1990s with the introduction of cylindrical, threaded titanium cages, again placed without supplemental internal fixation. The initial Investigational Device Exemption (IDE) studies showed low complication rates and near perfect fusion rates. Follow-up studies, however, showed quite variable results, and these devices were largely abandoned.
In the intervening years, however, the technique for PLIF has continued to be developed and refined. At present, it is a widely used, safe, and effective technique used for the treatment of spinal instability. Currently, a multitude of variations exist, including variations on the extent and vector of the surgical approach, the location of bone graft insertion, and the use of bilateral versus unilateral techniques. Similarly, multiple options exist for bone grafts, with or without interbody implants, as well for supplemental posterior instrumentation, which has become in integral part of the procedure.
This chapter highlights some of the technical aspects of PLIF. It attempts to capture some aspects of the procedure that are common to all these techniques, with emphasis on the surgical anatomy; the technical details of particular implants are left to other sources.
51.2 Patient Selection
PLIF is indicated for the treatment of patients requiring surgical arthrodesis of the lumbar spine. That being said, certain conditions distinguish themselves as being particularly appropriate. Ideally, a candidate for PLIF will have an underlying condition that requires both a dorsal decompression (particularly if this involves a diskectomy) and a surgical arthrodesis. Such conditions include disk herniation with concomitant instability, deformity, or disabling low back pain, lateral or foraminal disk herniations requiring facetectomy for treatment, massive disk herniations requiring bilateral complete facetectomy for adequate decompression, and certain recurrent disk herniations, especially if they are associated with disabling low back pain. For most patients who do not meet these criteria, alternative options usually exist that do not involve extensive disruption of the epidural space. Of course, for most patients, a reasonable trial of nonoperative treatment must have been unsuccessful before surgery is considered.
Relative contraindications are few, provided that the patient is a candidate for surgical arthrodesis of the lumbar spine. Because the performance of a PLIF requires substantial retraction of the thecal sac and nerve roots, conditions that restrict or prevent this maneuver should be given special consideration. A standard PLIF should not be performed at or above the level of the conus medullaris. When this procedure is considered in the upper lumbar region, imaging should be performed to ascertain the level of the conus. Tethered cords and similar congenital anomalies usually preclude PLIF at that level. Likewise, the presence of a conjoint nerve root at the level to be fused may preclude PLIF, at least on the side of the anomaly.
51.3 Preoperative Preparation
Preoperatively, patients should be counseled in a standard manner and informed consent obtained. Patients appear to benefit substantially from detailed preoperative counseling regarding their expected postoperative level of discomfort, postoperative course, and need for immediate mobilization. In almost all cases, smoking should be stopped well in advance of the procedure. Nonsteroidal anti-inflammatory medications should be stopped 1 week before and for at least 1 month after the procedure. In addition to standard blood tests, a type and screen should be ordered. We rarely cross-match blood products in routine cases.
After induction of anesthesia, a Foley catheter is routinely placed. The cell saver is used routinely. Standard anesthetic techniques are used. I prefer that patients be maintained in a normotensive, euvolemic state. Perioperative antibiotics are administered. Muscle relaxants are not used unless anesthetic considerations dictate their use. Likewise, corticosteroids are not used unless concomitant medical conditions dictate their use.
51.3.1 Positioning
Patients are positioned prone with the lumbar spine in lordosis. Pressure on the abdomen should be minimized by using transverse rolls at the levels of the shoulders and waist or with any of a variety of frames designed specifically for this purpose. Abduction of the arms alleviates interference with lateral radiography, although they should not be abducted more than 90 degrees. All pressure points should be generously padded, and the genitalia and breasts should be free of compression. If intraoperative surgical adjuncts are to be used, such as fluoroscopy or navigation systems, all equipment should be compatible.
51.4 Operative Procedure
As already discussed, numerous technical variations in the performance of a PLIF exist. The technique described here represents a single-level, generic, “maximally invasive” technique that may be refined based on the patient’s pathology, individual experience, alternative implants, and intraoperative adjuncts, at the discretion of the surgeon.
A midline incision incorporating three spinous processes is designed, centered on the spinous process of the upper vertebrae of the segment to be fused (i.e., L4, in the case of an L4–5 fusion). The incision is infiltrated with 0.5% lidocaine/1:200,000 epinephrine. After the patient is prepared and draped, and the surgical “timeout” is performed, the skin incision is made down to the thoracolumbar fascia with minimal use of the electrocautery. The fascia is then opened, and a bilateral subperiosteal dissection is performed of the spinous processes, lamina, and facets of the levels to be fused. Although exposure of the facet joint immediately cephalad of the segment to be fused is usually necessary to place transpedicular instrumentation, care is taken not to violate the facet joint capsule. Likewise, the capsule of the facet joint at the level to be fused is not violated until a lateral radiograph, taken at this time, has confirmed the appropriate level. Exposure of the transverse processes is usually unnecessary because a concurrent transverse process fusion is not recommended.
Using techniques described in Chapter 52, bilateral transpedicular screws are placed in the rostral and caudal vertebrae. After appropriate connectors and rods have been placed, the hardware is provisionally tightened ( ▶ Fig. 51.1). If desired, gentle distraction can be applied across the segment before provisional tightening. It is my preference to do this only when the disk space is particularly collapsed.
Fig. 51.1 Dorsal view of segment to be fused, after placement of posterior nonsegmental instrumentation. Cranial is right, caudal is left. Ordinarily, transverse processes would not be exposed. Note that heads of screws are directed laterally so as not to impinge on the cranial facet joint.
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