Clinical Outcome Study of Minimally Invasive Decompression for Lumbar Spinal Stenosis
Clinical Outcome Study of Minimally Invasive Decompression for Lumbar Spinal Stenosis
The study is a prospective outcome study to evaluate the effectiveness and treatment outcomes
 of microendoscopic decompressive laminotomy (MEDL) with objective evaluation tools. The
 patients who fulfill the selection criteria will be enrolled to collect the pre-operative
 clinical data including demographic data, image studies, and functional evaluation for
 neurological symptoms and disability.

 The patient will receive MEDL and post-operative follow-up will be arranged at 1 week, 1
 month, 6 months, and 12 months after the operation. All the collected data will be analyzed
 to evaluate the efficacy and treatment results of MEDL.
The patients undergoing microendoscopic decompressive laminotomy (MEDL) for lumbar spinal
 stenosis (LSS) between will be enrolled in this prospective study. The patients included must
 fulfill the following selection criteria:

 -  neurogenic claudication or radicular leg pain with associated neurologic signs referring
 to the LSS syndrome;

 -  moderate to severe spinal canal stenosis shown on cross-sectional imaging such as MRI or
 CT scan;

 -  failure of conservative treatment for at least three months.

 The patients who presents with either mechanical low back pain or segmental instability.
 Mechanical lower back pain is defined as pain that was induced by posture change, or that
 prevents the patient from sitting or standing for more than 30 minutes. Patients are
 considered to have segmental instability if they had isthmic spondylolisthesis, degenerative
 spondylolisthesis with more than 4 mm of translation or intervertebral angle reversal on
 dynamic radiographs.18 Surgical techniques

 All the surgical procedures will be performed by a single surgeon (J. P.). The patients is
 positioned prone on the Relton-Hall frame after general anesthesia. Decompression is done
 under the endoscope with the tubular retraction system METRx (Medtronics, Minneapolis, MN).
 For patients with unilateral neurological symptoms, we will perform unilateral laminotomy and
 foraminotomy. For patients with bilateral neurological symptoms, we will performe unilateral
 laminotomy for bilateral decompression (ULBD) to decompress the central canal and bilateral
 lateral recesses.

 When performing multiple-level decompression, the skin incision will be centered at the
 midpoint between selected intervertebral disc levels. The incision can be mobilized one level
 above or below after releasing the underlying connective tissues. Then we can set up the
 tubular retractor system through separate muscular portals for each level. For patients with
 small stature, we can perform a three-level surgery through a single surgical wound, just as
 the same size as we perform the single-level surgery.

 All the patients will have routine AP, lateral, dynamic lateral radiographs pre-operatively,
 six months after the surgery, and at final follow-up. Post-operative instability is defined
 as progression of listhesis or scoliosis on dynamic radiographs.

 Every patient will MR images of the lumbar spine before the surgery. The severity of stenosis
 is classified according to the cross sectional area of the dura sac at the axial plane on
 T1-weighted MR images-severe stenosis for less than 76 mm2, moderate stenosis for between 76
 and 100 mm2, and mild stenosis for more than 100 mm2. When MRI is contraindicated,
 CT-myelography will be used instead.

 Outcomes assessment will done with Oswestry Disability Index (ODI) for the overall disability
 and the Japanese Orthopedic Association (JOA) score for the clinical symptoms and signs. The
 patients will receive evaluation before the surgery, at six months, and at the final
 follow-up examination. The range of ODI is 100 ~ 0 with a lower index corresponding to a
 better result. Significant improvement is defined as more than 15 points of improvement after
 the treatment. The range of JOA score is -3 ~ 29 with a higher score corresponding to a
 better result. The improvement rate based on JOA score is calculated as follows:
 (pre-operative score - post-operative score)/(29 - pre-operative score) × 100%. The clinical
 results are classified into four grades by the improvement rate: excellent (more than 75%),
 good (between 51% and 75%), fair (between 26% and 50%), and poor (less than 26%). The success
 of treatment is defined as more than 25% improvement rate in JOA score.20 At the final
 follow-up, we will inquire each patient if he or she is satisfied with the treatment results.

 The data about the pre-operative comorbidities, intra-operative, peri-operative, and
 post-operative complications will be retrieved from medical chart review.

 Distribution of gender, age, clinical characteristics (coexistence of spondylolisthesis or
 scoliosis, severity of stenosis, and levels of decompression), and self-assessed satisfaction
 by the binary outcome of treatment (success or not, based on the JOA score; significant
 improvement of not, base on the ODI) will be tabulated. Fisher exact test will be preformed
 to compare the difference between the two groups. Odds ratios will be calculated by using the
 univariate logistic regression. Variables with two-sided p-value less than 0.05 were
 considered as significant factors associated with successful treatment. All statistical
 analyses are performed with statistical software, SAS version 9.1 (SAS Institute Inc, Cary,
 NC).
Inclusion Criteria:

 -  neurogenic claudication or radicular leg pain with associated neurologic signs
 referring to the LSS syndrome

 -  moderate to severe spinal canal stenosis shown on cross-sectional imaging such as MRI
 or CT scan

 -  failure of conservative treatment for at least three months

 Exclusion Criteria:

 -  mechanical low back pain or segmental instability