Patient Selection

As with any operation, patient selection is a critical factor in lumbar spine surgery where preexisting pain syndromes and dependence on medication may complicate the pre- and postoperative care of patients. The rationale for performing a PLIF is that fusion of the vertebral segments eliminates any instability that may be causing recurrent or persistent pain. Unless a focal neurologic deficit is identified, aggressive nonoperative therapy, including but not limited to the use of muscle relaxants, steroid injections, and pain medications, should be tried prior to committing the patient to an operation. Contraindications to performing PLIF include osteoporosis, discitis, subchondral sclerosis, and adhesive arachnoiditis. Once a patient has been selected for surgery, standard preoperative imaging and laboratory tests, including electrocardiography and chest x-rays, should be obtained, and the patient should be cleared by anesthesia for operative intervention. In most cases, supine and standing radiographs and computed tomography of the spine may be useful.

Open PLIF

The classic PLIF technique consists of three surgical steps: (1) laminectomy or laminotomy with partial or complete facetectomy, (2) removal of the intervertebral disc, and (3) fusion. The classic PLIF technique is performed with the patient in the prone position, using a midline incision and subperiosteal dissection. Although the approach is relatively straightforward, the posterior spinal musculature is likely to be damaged. With the advent of minimally invasive spinal approaches (described later), many surgeons now use muscle-splitting approaches to minimize such damage to the paraspinal muscles.

After the patient is placed in the prone position, pressure points are padded to minimize pressure sores (Fig. 169-1). A Jackson table can be used to avoid compression and venous congestion, which may cause excessive bleeding during posterior approaches. Fluoroscopy should be used to identify the spinal level of interest. As in any posterior approach, the landmarks are the spinous processes, iliac crest, and posterior superior iliac spine.

FIGURE 169-1 Setup of the operative theater with the patient positioned prone, the fluoroscope and microscope in place, and the position of the anesthesia team and scrub staff relative to the surgeon.

(Used with permission from Barrow Neurological Institute.)

The skin is incised (Fig. 169-2A) in the midline above the spinous process, and the subcutaneous tissue is dissected. The thoracolumbar fascia is incised and dissection proceeds in a subperiosteal fashion, detaching the paraspinal muscles from the spinous process and lamina (Fig. 169-2B). For each level that is to be treated, the cranial lamina and ligamentum flavum are removed completely (Fig. 169-2C). The cranial aspect of the caudal lamina should also be removed to gain adequate access to the interbody space. To prevent traction on the spinal cord or nerve roots during placement of the interbody graft, a wide window is created by resecting the lower third of the inferior facet and the medial two thirds of the superior facet. Next, the nerve root and dural sac are retracted medially, creating maximal exposure of the interbody space for removal of any bony or disc material (Fig. 169-3A).

FIGURE 169-2 A, Incision used in the open PLIF centered over the thoracolumbar spine. B, The incision exposes the anatomy, revealing the lamina, facet joints, and dura. C, Next, the lamina and facets are removed and the exposure of the annulus and dura is increased to perform the necessary discectomy without placing undue traction on the spinal cord and thereby damaging it.

(Used with permission from Barrow Neurological Institute.)

FIGURE 169-3 A, The nerve root and dural sac are retracted medially, creating maximal exposure of the interbody space. B, The interbody device is inserted bilaterally and packed with bone for maximal fusion. C, A pedicle screw is used to distract the disc space. The trajectory and depth of the screw are important for successful fusion. D, Next, using either a screw or a rod construct, the final arthrodesis is reinforced until biologic fusion is achieved.

(Used with permission from Barrow Neurological Institute.)

Following adequate decompression of the neural structures and removal of the disc material, the disc space is distracted using pedicle screws or disc space distractors. We prefer to use pedicle screws as distractors (Fig. 169-3B). Next, the end plates are prepared, using curettes to remove any remaining disc material while preserving the bony end plates to prevent graft subsidence. Adequate preparation of the graft site and preparation of the end plates are important steps for ensuring a proper fusion.

In young patients, the lumbar cortical end plates are thinner; therefore, when a PLIF is performed on a young patient, appropriate exposure of the cortical bone is sufficient to ensure adequate surface for fusion. In older patients, the surface of the bone should be roughened to the cancellous bone to provide adequate blood supply for fusion.

Next, a graft spacer or cage is placed into the interbody space under direct visualization of the cranial and caudal nerve roots (Fig. 169-3C). Bone graft packing is used to augment the fusion. The graft choice is highly surgeon dependent, with options such as threaded cages, titanium mesh cages, and auto- and allograft with or without the use of bone morphogenetic protein. The graft-filled interspace is stabilized with internal fixation using screws and rods or a plate construct to aid in fusion and immobilization (Fig. 169-3D).

PLIF is an effective procedure and results in excellent fusion (Fig. 169-4) with rates in the range of 80% to 98%.^13,¹⁴ PLIF also has been shown to be effective for reducing pain and disability.¹³