Expansive Suspension Laminoplasty Using a Spinous Process-Splitting Approach for Lumbar Spinal Stenosis: Surgical Technique and Outcomes Over 8 Years of Follow-up

Abstract

Introduction: To maximize the benefits of posterior decompression for severe multilevel lumbar spinal stenosis, we refined the expansive laminoplasty technique using a spinous process-splitting approach. This study tests the hypothesis that the surgical benefit of adequate decompression with posterior element preservation is maintained in the long term, over 8 years of follow-up.

Methods: Fifty-eight patients were followed up yearly for 8 years. Eight patients having nonlumbar spine surgery or Parkinson disease were excluded. The noninferiority of the 8-year versus peak-year outcomes was tested, with margins of 5 points for the Oswestry disability index and 1 point for the numeric rating scales (NRSs).

Results: In the 50 patients available for follow-up, the peak values of the mean improvements from baseline within the first 7 years were 35.8, 5.7, 5.9, and 2.8 points for the Oswestry disability index, low back pain NRS, leg pain NRS, and leg numbness NRS, respectively. The 95% lower confidence limits for the differences between the mean improvements from baseline at 8 years and the peak year were within the noninferiority margins for each scale.

Conclusion: Our technique was associated with substantial improvement from baseline for each scale. The initial improvements in function and symptoms were maintained for 8 years.

Figure 1

A–E, Diagram demonstrating surgical technique. A, Axial plane: the spinous process is split into one midline and two outer portions. B, Axial plane: bilateral gutters are longitudinally created. C, Axial plane: the laminar flap is elevated and kept suspended with bilateral laminar spacers. D, Posterior view: the laminar flap is elevated and kept suspended with bilateral laminar spacers. The spacers are fixed with two nonabsorbable sutures. E, Axial plane: bone autografts obtained from the excised laminae or facet joints are placed around the spacers. The bilateral outer portions of the spinous processes are reattached to each other.

Figure 2

A and B, Preoperative and postoperative MRI scans of a patient who underwent surgery at the levels between L1-L2 and L5-S1 at the age of 71 years. A, Preoperative scan. B, Five years postoperatively, an enlarged spinal canal throughout the disk and vertebral body levels and preserved spinous processes are evident. Little epidural fibrosis is seen between the dural sac and the laminae.

Figure 3

A and B, Preoperative and postoperative CT scans of the L4 vertebra of a man who underwent surgery at the levels between L3-L4 and L4-L5 at the age of 67 years. A, Preoperative CT scan after myelography indicating a narrowing of the spinal canal at the vertebral body level. B, A scan, obtained 4.6 years postoperatively, indicating enlargement of the spinal canal and successful reconstruction of the osseous continuities between the midline and outer portions of the spinous process and between the laminar flap and the lateral elements. Hydroxyapatite spacers were incorporated into the surrounding regenerated bone.