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Lumbar facet bone fusion presents alternative method for stable degenerative grade I spondylolisthesis

ByJoseph C. Maroon, MD, FACS

ByJeff Bost, PAC

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There is no consensus in spine surgery as to the need to fuse the lumbar spine following a laminectomy for spinal decompression. Various studies have proposed risk factors for delayed instability, including preexisting spinal instability, significant facetal disease, increased disc height, the need for multiple level laminectomy and the extent of facet disruption or prior discectomy.

The need for laminectomy/fusion surgery for lumbar spinal stenosis with pre-existing spondylolisthesis is considered less controversial, which is especially true for documented spine instability. The postoperative risk for reoperation after lumbar laminectomy without fusion was recently addressed by Blumenthal and colleagues. They found patients with grade I spondylolisthesis who had undergone laminectomy and had a pre-existing facet angle greater than 50° had a 39% rate of reoperation. If the disc height was greater than 6.5 mm, then a 45% reoperation rate was found. The greatest reoperation rate (54%) was associated with spine segment movement of greater than 1.25 mm.

Increasingly common

Grade I lumbar degenerative spondylolisthesis with associated symptomatic spinal stenosis is an increasingly common presentation linked to the increased incidence of obesity, osteoporosis and facet arthropathy commonly found in older patients. The potential risks for reoperative fusion surgery following lumbar laminectomy, especially with significant comorbidities of aging, has led to an explosion of both innovative and traditional minimally invasive, percutaneous and other open surgical techniques to fuse the lumbar spine.

Joseph C. Maroon

Many of these fusion devices are being developed to supplant or reduce the need for traditional pedicle screw fixation (PSF). Risks associated with traditional PSF with transverse process bone fusion are well-documented and tend to be greater in older age groups with significant underlying medical comorbidities. Pedicle screw fixation also can add significant cost, morbidity and mortality risks beyond those associated with laminectomy alone.

Fuse articular surfaces

In an article published in January 2013 in Surgical Science, researchers evaluated a recently introduced allograft bone dowel (TruFUSE, minSURG, Clearwater, Fla.) designed to fuse the articular surfaces of the facet joint. The patient population evaluated were elderly patients (average age of 69.5 years) who had underlying pre-existing fixed degenerative spondylolisthesis with symptomatic lumbar stenosis. Their results using allograft bone dowel facet fusion were compared to a literature-based cohort of patients who had undergone lumbar pedicle screw fusion and had similar categories of data for comparison. Significant differences in length of hospital stay, operative time, blood loss and objective and subjective outcome measures were compared, along with potential cost savings using this technology.

Jeff Bost

Overall, 41 consecutive patients who had underwent single and multilevel laminectomy were fused with the allograft bone dowel fusion and transverse process bone fusion. They were evaluated at 2 years after surgery with lumbar flexion and extension radiographs. Facet fusion was done at one level for 73% of the patients and the rest of the patients had fusion at two levels, with the majority at L4-L5. The mean operative time for a laminectomy and fusion was 106±23 minutes and a mean blood loss intraoperatively of 145±66.8 mL. Patients were hospitalized for an average of 1.7±1.6 days postoperatively. There was no evidence of facet fracture or bone dowel dislodgement on any postoperative radiographs, including flexion and extension radiographs. Researchers found that 39 patients had no movement on follow-up flexion and extension radiographs.

Rapid bone placement

Although the concept of facet fusion with bone packed in and around facet joints is not new, this study demonstrated that milled bone dowels and specifically designed insertion instruments allows for rapid bone placement resulting in less operative time, tissue disruption and blood loss compared to traditional PSF. With a 95% fusion rate, 80% of patients postoperatively reported improvement and relief of preoperative symptoms, significant reduction of operative time and length of hospital stay compared to PSF. The authors concluded the cost saving in this selected group of patients could reduce the typical cost of fusion using PSF by 47%.

Conceding that laminectomy and facet bone dowel fusion along with transverse process bone fusion for stable grade I lumbar spondylolisthesis alone may not provide universal stabilization in all types of patients. This approach should be considered as an alternative to PSF for elderly patients or patients where excessive blood loss, operative time and costs are a consideration.