Sagittal Plane Shear Index for Planning Lumbar Stenosis Surgery

Study Overview
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Brief Summary
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The objective of the clinical investigation is to assess the proportion of lumbar spinal stenosis surgical treatment plans that change when an objective measurement of spinal stability is included and applied following a simple treatment algorithm. The objective spinal stability metric is calculated from flexion-extension radiographs using previously validated methods.

Detailed Description
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Patients with previously diagnosed lumbar spinal stenosis and spondylolisthesis, who have consented to surgical treatment consisting of either decompression alone or decompression plus fusion will be invited to participate in the study. The initial surgical plan will be recorded prior to reviewing the sagittal plane shear index (SPSI). The sagittal plane shear index will be calculated flexion-extension radiographs. The measurements required to calculate SPSI will be obtained using previously validated methods. SPSI greater than 2 indicates that the translation-per-degree of rotation (TPDR) is above the upper limit of the 95% confidence interval observed in several hundred asymptomatic and radiographically normal individuals. SPSI will be reported to the surgeon after recording the pre-SPSI surgical plan. The surgeon will then decide whether to change the surgical plan. For example, if the initial surgical plan was to only decompress a level, and SPSI is greater than 2, the surgeon may plan to add fusion to the decompression. Conversely, if the initial plan was decompression plus fusion, and the SPSI indicates that the level is objectively stable, the post-SPSI plan may be to only decompress the level. The proportion of surgical plans that change after reviewing the SPSI report will be determined. If the proportion of surgical plans that change is greater than 15%, further research will be undertaken to explore whether deciding, based on objective measurement of spinal stability, whether to add fusion to decompression of a stenotic lumbar level will have a significant effect on clinical outcomes.

Official Title
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The Sagittal Plane Shear Index (SPSI) for Planning Whether to Fuse After Decompressing a Stenotic Lumbar Level

Conditions
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Lumbar Spinal Stenosis

Intervention / Treatment
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* Diagnostic Test: Sagittal plane shear index (SPSI)


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: Symptoms consistent with single level lumbar spinal stenosis based on judgment and experience of the investigator Central and or foraminal stenosis confirmed by MRI as per the investigators clinical standards Grades 1 (10 to 25%) or 2 (26 to 50%) anterior or retro-spondylolisthesis using the Meyerding scale [43] Absence of lateral spondylolisthesis No prior lumbar spinal surgery Absence of American Society of Anesthesiologists (ASA) class IV or higher disease The single level surgical technique planned (prior to viewing the spinal motion report) to decompress the level is not expected to destabilize the spine (fusion is not deemed necessary due to probable iatrogenic instability) Prior to viewing the spinal motion report, the surgical plan includes decompression or decompression and fusion of only one level Based on the investigators subjective assessment, the patient is able to flex and extend sufficiently to facilitate acceptable flexion and extension radiographs The fusion technique planned prior to viewing the spinal motion report is the following: Instrumented posterior (pedicle screws and rods) with / without postero-lateral interbody fusion cage Subject is able to understand and sign the study Informed Consent Form Subjects is at least 18 years of age. Subject has willingness and ability to comply with study procedures and visit schedules and able to follow oral and written instructions Exclusion Criteria: Lumbar stenosis without spondylolisthesis Severe lumbar stenosis that requires a wide decompression where the investigator believes (based on experience and available research studies) that the decompression will destabilize the spine and fusion surgery is required regardless of preoperative SPSI Pregnant women Scoliosis involving a lumbar curve greater than 10 degrees Stenosis at the level of a transitional vertebra Lateral spondylolisthesis (Coronal plane translational misalignment between vertebrae) Prior lumbar spinal surgery American Society of Anesthesiologists (ASA) class IV or higher disease

Ages Eligible for Study
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Minimum Age: 18 Years

Sexes Eligible for Study
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All

Accepts Healthy Volunteers
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No

Study Plan
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How is the study designed?
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Design Details

Primary Purpose: Diagnostic
Intervention Model: Single Group Assignment
Interventional Model Description: Determine whether an objective metric for spinal stability will change the surgical treatment plan in a significant proportion of patients with lumbar spinal stenosis
Masking: None (Open Label)


Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Experimental: Lumbar spinal stenosis surgery candidate<br>Patients with lumbar spinal stenosis and spondylolisthesis that have previously consented to surgical treatment. After recording the initial surgical plan, the Sagittal plane shear index (SPSI) will be provided to the surgeon. The surgeon may change the initial surgical plan based on the stability metric. | Diagnostic Test: Sagittal plane shear index (SPSI)<br>* Report SPSI to surgeon after surgeon records an initial surgical plan, and determine whether the objective spinal stability metric influences a change in the surgical plan.<br>|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Proportion of surgical plans recorded prior to the SPSI report that are altered after integration of SPSI into the surgical planning | The surgeons will record their surgical plan (decompression alone or decompression plus fusion) prior to receiving the SPSI report. The surgeon will then integrate the data in the SPSI report into their surgical planning and record a post-SPSI report surgical plan. The proportion of lumbar spinal stenosis surgery plans that change after an objective metric for spinal stability is included in the surgical planning will be determined. If the proportion of plans that change after integration of the SPSI report is greater than expected due to subjectivity in surgical planning, then the SPSI report will be considered clinically effective and further research will be pursued. | Pre-surgery | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Association between the preoperative SPSI and the facet fluid sign observed in a preoperative MRI | Prior research has reported that SPSI is significantly higher at lumbar levels where a facet fluid sign is observed in a MRI exam. Outcome 2 is intended to test the hypothesis that this prior finding can be repeated. SPSI will be calculated for all levels in the lumbar spine from preoperative lumbar flexion-extension radiographs. The surgeons will record whether they observe the fluid sign in the facet joints based on review of a preoperative MRI exam. Statistical tests will be performed for an association between preoperative SPSI and the presence or absence of a facet fluid sign observed by the treating surgeon in a preoperative MRI exam of the lumbar spine. | Pre-surgery | 
| The proportion of surgically decompressed levels where SPSI was at least one standard deviation higher at 12 months compared to preoperatively. | Prior research has documented that decompression surgery may compromise the stability of the treated level. To test whether this phenomena can be documented using the SPSI metric, SPSI measured at 12 months will be compared to SPSI measured preoperatively. This will be assessed only in patients treated with decompression alone (patients treated with fusion in addition to decompression will not be included). Statistical tests will be used to determine the proportion of levels treated using decompression only where the SPSI at 12 months was at least 1 standard deviation greater than preoperatively. | One year after surgery | 
| Reoperation rate at 1 and 2 years following surgery | Multiple prior studies have documented reoperation rates following surgery for lumbar spinal stenosis. To test whether the reoperation rate in the current study is comparable to prior studies, clinical records will be reviewed to determine whether additional surgery was performed at the treated and/or adjacent levels. Statistical tests will be used to compare the reoperation rates at 12 and 24 months after the index surgery to reoperation rates previously reported in the peer-reviewed literature. | 12 and 24 months | 
| Are the ODI scores at 12 months following lumbar fusion surgery dependent on whether the treated level is fused, with fusion defined as intervertebral rotation < 2 degrees and an absence of radiographic signs of a non-union | The existing peer-reviewed literature is inconsistent with respect to the hypothesis that the Oswestry Disability Index (ODI) is affected by a non-union of a lumbar level treated using fusion surgery. The ODI quantifies disability related to low back pain. The ODI will be recorded preoperatively and at 12 months following surgery. Each lumbar level will be classified as fused if intervertebral rotation between flexion and extension is < 2 degrees and there is an absence of a discontinuity in bone bridging between vertebrae. The ODI at 12 months, as well as the change in ODI relative to preoperative outcomes will be compared for subjects classified as fused versus not-fused. This test will only be performed for subjects where the stenotic lumbar level was treated using decompression and fusion. | 12 months | 
| Is leg pain at 12 months following lumbar fusion surgery dependent on whether the treated level is fused, with fusion defined as intervertebral rotation < 2 degrees and an absence of radiographic signs of a non-union | The existing peer-reviewed literature is inconsistent with respect to the hypothesis that leg pain assessed using a Numerical Rating Scale (NRS) is affected by a non-union of a lumbar level treated using fusion surgery. Leg pain measured using a NRS will be recorded preoperatively and at 12 months following surgery. Each lumbar level will be classified as fused if intervertebral rotation between flexion and extension is < 2 degrees and there is an absence of a discontinuity in bone bridging between vertebrae. The leg pain NRS data at 12 months, as well as the change in leg pain relative to preoperative outcomes will be compared for subjects classified as fused versus not-fused. This test will only be performed for subjects where the stenotic lumbar level was treated using decompression and fusion. | 12 months |