Patient Selection: Lumbosacral Fusion
Lumbosacral Fusion: Cages, Dowels, Pedicle Screws: Part 3
While the overwhelming majority of patients with mechanical low back pain secondary to lumbar degenerative disc disease have only transient, self-limiting episodes, up to 5% do not respond to appropriate nonoperative treatment.25, 31 ALIF procedures have been utilized in an ever-increasing fashion for the management of these failures.22, 28, 58, 83, 90 The actual pathophysiology of such "discogenic" pain patients is poorly understood, involving a combination of degenerating intervertebral discs, social, and psychological factors.25, 37 Magnetic resonance imaging (MRI) has proven to be of value in the assessment of such patients, demonstrating excellent sensitivity and specificity in the diagnosis of discal pathology.29 However, even among 20 to 39 year-olds, the rate of asymptomatic disc degeneration is as high as 34%, with up to 21% having asymptomatic disc herniations.6 Because of this, discography is a useful tool in the assessment of patients with MRI-documented "black disc disease".14, 32, 56, 58 To date, discography is the sole procedure capable of correlating pathoanatomy and symptomatology in patients with primary discogenic pain89 and several studies have suggested improved surgical outcomes among interbody fusion patients with concordant discography preoperatively.20, 33
Appropriate patient selection is critical to the clinical success of ALIF. Indications for interbody fusion procedures include degenerative disc disease of one or two contiguous levels of the lumbar spine with chronic, severe, disabling, intractable low back pain of at least six months duration in patients unresponsive to an adequate and extensive trial of nonoperative treatment.60, 83 Although some series have included patients undergoing up to three level stand-alone ALIFs, it has been clearly shown that with each additional level fused, the interbody pseudarthrosis rate increases and the clinical success rate declines.14, 36, 58 Ray,83 stressed the importance of disc height and mobility loss. Patients who had a disc-space height of more than 12 mm were excluded from his series. Interbody fusion may also be indicated in selected patients with a failed prior posterior fusion attempt. 11, 28, 36, 58, 72 Certainly, under these circumstances, avoiding the peridural fibrosis is a major advantage of these devices in an anterior application.
Contraindications for ALIF include active systemic or local disc space infection, osteopenia, the presence of degenerative changes at adjacent, neighboring disc spaces, symptomatic peripheral vascular disease, malignancy, gross obesity, spondylolisthesis greater than grade 1, pregnancy, neural compression secondary to stenosis, and previous retroperitoneal surgery. 60, 83 Kuslich60 limited his procedure to patients between the ages of 21 and 65 years. While these devices have been FDA approved for grade I spondylolisthesis, caution should be used with isthmic pathology, rather than a degenerative etiology. The pars defect leads to increased posterior column instability (particularly in axial rotation) and potentially could lead to an increased failure rate. 68, 99 McAfee64 believes the use of cages should be limited to patients who have postlaminectomy syndrome or disc-space collapse with neuroforaminal narrowing. Optimally, only patients who have involvement of one disc level should be treated with stand-alone cages, and patients who require more than a two level fusion should undergo a posterior procedure.