Microendoscopic decompression for lumbosacral foraminal stenosis: a novel surgical strategy based on anatomical considerations using 3D image fusion with MRI/CT

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  • 1 Department of Orthopedic Surgery, Wakayama Medical University, Wakayama;
  • 2 Spine Care Center, Wakayama Medical University Kihoku Hospital, Wakayama;
  • 3 Department of Orthopedic Surgery, Sumiya Orthopaedic Hospital, Wakayama, Japan; and
  • 4 Microendoscopic Spine Institute and Brigham and Women’s Hospital, Harvard Medical School, Boston, Massachusetts
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OBJECTIVE

Persistent lumbar foraminal stenosis (LFS) is one of the most common reasons for poor postoperative outcomes and is a major contributor to “failed back surgery syndrome.” The authors describe a new surgical strategy for LFS based on anatomical considerations using 3D image fusion with MRI/CT analysis.

METHODS

A retrospective review was conducted on 78 consecutive patients surgically treated for LFS at the lumbosacral junction (2013–2017). The location and extent of stenosis, including the narrowest site and associated pathology (bone or soft tissue), were measured using 3D image fusion with MRI/CT. Stenosis was defined as medial intervertebral foraminal (MF; inner edge to pedicle center), lateral intervertebral foraminal (LF; pedicle center to outer edge), or extraforaminal (EF; outside the pedicle). Lumbar (low-back pain, leg pain) and patient satisfaction visual analog scale (VAS) scores and Japanese Orthopaedic Association (JOA) scores were evaluated. Surgical outcome was evaluated 2 years postoperatively.

RESULTS

Most instances of stenosis existed outside the pedicle’s center (94%), including LF (58%), EF (36%), and MF (6%). In all MF cases, stenosis resulted from soft-tissue structures. The narrowest stenosis sites were localized around the pedicle’s outer border. The areas for sufficient nerve decompression were extended in MF+LF (10%), MF+LF+EF (14%), LF+EF (39%), LF (11%), and EF (26%). No iatrogenic pars interarticularis damage occurred. The JOA score was 14.9 ± 2.6 points preoperatively and 22.4 ± 3.5 points at 2 years postoperatively. The JOA recovery rate was 56.0% ± 18.6%. The VAS score (low-back and leg pain) was significantly improved 2 years postoperatively (p < 0.01). According to patients’ self-assessment of the minimally invasive surgery, 62 (79.5%) chose “surgery met my expectations” at follow-up. Nine patients (11.5%) selected “I did not improve as much as I had hoped but I would undergo the same surgery for the same outcome.”

CONCLUSIONS

Most LFS existed outside the pedicle’s center and was rarely noted in the pars region. The main regions of stenosis were localized to the pedicle’s outer edge. Considering this anatomical distribution of LFS, the authors recommend that lateral fenestration should be the first priority for foraminal decompression. Other surgical options including foraminotomy, total facetectomy, and hemilaminectomy likely require more bone resections than LFS treatment. The microendoscopic surgery results were very good, indicating that this minimally invasive surgery was suitable for treating this disease.

ABBREVIATIONS EF = extraforaminal stenosis; JOA = Japanese Orthopaedic Association; LF = lateral intervertebral foraminal stenosis; LFS = lumbar foraminal stenosis; MCID = minimum clinically important difference; MF = medial intervertebral foraminal stenosis; VAS = visual analog scale.

Supplementary Materials

    • Supplementary Figs. S1–S3 (PDF 3.76 MB)

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Contributor Notes

Correspondence Shizumasa Murata: Wakayama Medical University, Wakayama City, Wakayama, Japan. shizuman@wakayama-med.ac.jp.

INCLUDE WHEN CITING Published online August 7, 2020; DOI: 10.3171/2020.5.SPINE20352.

Disclosures Dr. Schoenfeld reports support of non–study-related clinical or research effort from the NIH, Orthopedic Research and Education Foundation, and Department of Defense, and receiving royalties from Wolters Kluwer. Dr. Simpson reports being a founder of the Microendoscopic Spine Institute and having ownership in VertebrX.

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