The Sagittal Plane Shear Index (SPSI) for Planning Whether to Fuse After Decompressing a Stenotic Lumbar Level
Phase: NA
Conditions: Lumbar Spinal Stenosis, Spondylolisthesis
Sponsor: Medical Metrics Diagnostics, Inc

 
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The Sagittal Plane Shear Index (SPSITM) for planning whether to fuse 
after decompressing a stenotic lumbar level 
 
 
 
Version Date: 14-July-2023 
 
Clin Trials #: NCT03754972

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SYNOPSIS 
Investigation Title 
The Sagittal Plane Shear Index (SPSI™) for deciding whether to fuse after 
decompressing a stenotic lumbar level 
Sponsor 
Medical Metrics Diagnostics, Inc. 
Protocol Reference 
SPSI-01 
Investigational Device 
Sagittal Plane Shear Index (SPSITM) 
Overall Design 
This is a prospective, multi-center, single arm clinical investigation  
Device description 
SPSITM quantifies the sagittal plane translation per degree of rotation from 
high-quality flexion-extension radiographs of the lumbar spine. 
Intended Use 
SPSITM will be used preoperatively in lumbar stenosis patients to objectively 
assess the sagittal plane translation per degree of rotation of the stenotic 
level. 
Objective of the clinical 
investigation 
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 
Investigation duration 
and number of visits 
Total duration of the clinical investigation is 41 months: 
• Enrollment period: 12 months 
• Follow-up phase: 24 months 
• Total number of visits per subject: 4 
Investigational Centers 
3 centers in the Netherlands 
Investigation Population 
65 lumbar spinal stenosis subjects  
Inclusion Criteria 
1. Symptoms consistent with single level lumbar spinal stenosis based 
on judgment and experience of the investigator  
2. Central and or foraminal stenosis confirmed by MRI as per the 
investigators clinical standards 
3. Grades 1 (10 to 25%) or 2 (26 to 50%) anterior or retro-
spondylolisthesis using the Meyerding scale  
4. Absence of lateral spondylolisthesis  
5. No prior lumbar spinal surgery 
6. Absence of American Society of Anesthesiologists (ASA) class IV or 
higher disease 
7. 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) 
8. Prior to viewing the spinal motion report, the surgical plan includes 
decompression or decompression and fusion of only one level 
9. Based on the investigators subjective assessment, the patient is able 
to flex and extend sufficiently to facilitate acceptable flexion and 
extension radiographs 
10. The fusion technique planned prior to viewing the spinal motion 
report is the following: Instrumented posterior (pedicle screws and 
rods) with / without PLIF cage. 

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11. Subject is able to understand and sign the study Informed Consent 
Form 
12. Subjects is at least 18 years of age.  
13. Subject has willingness and ability to comply with study procedures 
and visit schedules and able to follow oral and written instructions 
Exclusion Criteria 
1) Lumbar stenosis without spondylolisthesis 
2) 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 SPSITM 
3) Pregnant women   
4) Scoliosis involving a lumbar curve greater than 10 degrees 
5) Stenosis at the level of a transitional vertebra 
6) Lateral spondylolisthesis (Coronal plane translational misalignment 
between vertebrae) 
7) Prior lumbar spinal surgery 
8) American Society of Anesthesiologists (ASA) class IV or higher disease 
Primary Endpoint 
The primary endpoint is the proportion of lumbar spinal stenosis treatment 
plans that change when SPSITM results are used in establishing the surgical 
plan. 
Secondary Endpoints 
The secondary endpoint is the comparison of clinical outcomes (as measured 
by ODI and NRS leg pain) at 12 months and 24 months in lumbar stenosis 
patients where the surgical plan was in accordance with the SPSITM metric 
compared to historical controls.  
Exploratory Endpoints 
• Does the presence of a facet fluid sign as indicated by the investigator on 
preoperative MRI correlate to instabilities specified by SPSITM results? 
• What is the rate of instability (defined as a > 1 standard deviation increase 
in SPSITM) 12 months after decompression (no fusion) surgery, how do 
these rates compare to the published data and does the development of 
post-decompression instability have an effect on the change in ODI or NRS 
scores relative to preop? 
• 
What are the reoperation rates at 12 months following decompression 
alone and following decompression plus fusion, and how do these rates 
compare to published data from studies where similar inclusion and 
exclusion criteria were used and patients were randomized to 
decompression alone or decompression plus fusion? 
• Does a nonunion following decompression plus fusion surgery have an 
effect on the change in ODI or NRS scores relative to preop? 

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1. INTRODUCTION 
1.1. 
Lumbar Spinal Stenosis and Surgical Treatment Planning 
Lumbar spinal stenosis is a relatively common medical problem, the clinical outcomes are often 
suboptimal (eg only about 50% reporting satisfaction with surgery at 2 years [1]), and the patient-specific, 
optimal treatment for the condition is poorly understood, due in part to a lack of diagnostic tests that 
have been validated to aid in treatment optimization [2]. Decompression surgery with or without 
additional fusion surgery are common surgical treatments. As reviewed by Machado et al, many prior 
research studies have concluded that there is at best marginal benefit to fusing a stenotic lumbar level 
following decompression, versus just decompressing the level [3]. These studies are summarized in 
recent, high-profile publications [1, 4].  The decompression part of the surgery is generally accepted as 
essential to achieving clinical benefit by relieving the physical source of stenosis. Fusion surgery, if 
indicated, is typically performed as part of an expanded surgical procedure (decompression plus fusion). 
However, avoiding fusion when it is not beneficial is important since fusion can add substantial expense 
and morbidity to the surgery [5, 6].  
There are two generally accepted hypotheses for justifying fusion surgery in addition to decompression 
surgery. First, fusion is justified if the level being decompressed was unstable preoperatively. Unstable is 
typically defined as intervertebral motion above the range of motion expected in healthy and 
asymptomatic spines. Second, fusion surgery is justified if needed to prevent complications from 
iatrogenic instability that might be created by the decompression surgery.  
The first justification is supported by studies documenting an association between abnormal 
intervertebral motion and symptoms. Correcting a known potential source of symptoms (abnormal 
intervertebral motion) during the same surgery used to correct the primary source of symptoms 
(stenosis) is rational. The challenge with the first justification has been the lack of a validated, objective 
test to diagnose and objectively quantify preoperative instability.  
With respect to the second justification, there are some scientific publications that provide guidance to 
the surgeon to determine whether the decompression procedure may destabilize the spine [7, 8], 
although there is a lack of rigorous clinical validation studies. There is a range of techniques for 
decompressing the spine; some with a low probability of destabilizing the spine and others with a higher 
probability. The extent to which a decompression procedure may alter the stability of a spine can 
currently not be predicted with certainty.   
Neither of these two justifications for supplemental fusion surgery has been validated by clinical studies, 
partly due to the lack of a validated diagnostic test for spinal instability. Surgeons are currently faced 
with the dilemma of whether or not to add fusion to a decompression procedure. Surgeons currently 
rely mostly on their experience to conclude if a level is unstable preoperatively or if a specific 
decompression procedure is likely to destabilize the spine.  
As such, the preoperative determination of the stability of the spine is critical for the surgical planning 
for treatment of lumbar spinal stenosis. Unfortunately, although hundreds of peer-reviewed scientific 
publications address the challenge of reliably diagnosing spinal stability, no well-validated diagnostic test 
to reliably diagnosing spinal stability is currently in wide-spread clinical use. The facet fluid sign (high 

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signal intensity in axial or sagittal sections through the facet joints) that can be seen in some MRI exams 
of the lumbar spine is currently one of the best supported indicators for instability [9-11]. It should also 
be noted that gas can sometimes be seen in CT exams of the facet joints [12-14]. Gas in the facet joints is 
also an accepted indicator of instability [15], but gas would appear black on an MRI and would therefore 
be a false-negative. The MRI fluid sign may therefore have an unacceptable false-negative rate, although 
this has never been formally tested, also for lack of a gold-standard test for spinal instability. A validated 
test for spinal instability would facilitate research to determine whether instability measurements can be 
used choose the optimal surgical treatment for each level. 
An objective metric called the Sagittal Plane Shear Index (SPSITM) has been recently described in the 
scientific literature [16]. This metric was labeled as the Quantitative Stability Index (QSI™) [16]. To avoid 
confusion between multiple intervertebral motion metrics, the metric that was previously labeled QSI™ 
is now being labeled as the Sagittal Plane Shear Index (SPSITM). The SPSITM metric quantifies the sagittal 
plane intervertebral translation-per-degree-of-rotation (TPDR), and is reported as the number of 
standard deviations from the average found at radiographically normal levels in asymptomatic 
volunteers. The asymptomatic population that is used to define normal TPDR has been previously 
described [17]. Data for an additional 193 asymptomatic volunteers was added to this population to 
strengthen the definition of normal motion [18].  
TPDR has previously been described as a potential metric for spinal instability [19], but was not 
extensively pursued following the 1990 publication for lack of a clinically practical and validated method 
measuring intervertebral translations and rotations in clinical practice. The SPSITM metric can now be 
obtained in routine clinical practice using translation and rotation measurements obtained with 
validated computer-assisted methods (QMA®) [20-24]. SPSITM is intended to be simple to use.  According 
to the SPSITM treatment planning algorithm,   SPSITM > 2 informs a clinician that the TPDR is > 2 standard 
deviations above the average TPDR in the asymptomatic population. This provides for an objective 
diagnostic indicator for spinal instability defined as a specific, well-defined intervertebral motion metric 
that is outside the 95% confidence interval established for asymptomatic volunteers. If SPSITM is > 2 at a 
level where surgical treatment for stenosis is planned, then the clinician has objective evidence of 
abnormal motion and this may help to determine whether fusion should be completed in addition to the 
decompression surgery.  
In conclusion: Spine fusion is used in addition to decompression surgery for lumbar spinal stenosis in 
order to prevent abnormal intervertebral motion causing associated symptoms. At the same time, if the 
intervertebral motion at the stenotic level is within normal limits prior to surgery, and it is unlikely that 
the decompression will compromise stability, only spinal decompression will be performed [25]. Fusion is 
not indicated if the spinal level is stable preoperatively.  
The research proposed in this document is intended to address the need identified in a recent 
publication by Austevoll et al. [26], reporting on the effectiveness of decompression alone compared 
with additional fusion for lumbar spinal stenosis with degenerative spondylolisthesis. They concluded: 
“…a considerable number of patients can be treated with decompression alone. A challenge in future 
studies will be to find the best treatment option for each patient.” SPSITM is intended to be part of a 
solution to the challenge that Austevoll et al. describe. 

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1.2. 
Sagittal Plane Shear Index (SPSITM) 
The device under investigation is the Sagittal Plane Shear Index™ (SPSI™).  SPSITM is intended to be used 
preoperatively to objectively assess the sagittal plane translation per degree of rotation of the stenotic 
level in lumbar spinal stenosis patients. SPSITM is considered software as a medical device. The software 
is installed at MMI and will be used solely by trained analysts and technical staff at MMI. Investigational 
sites are required to electronically upload X-ray images of the spine to MMI, where these images are 
analyzed and SPSI™ is calculated using QMA®. The output of the system is a SPSI™ report containing a 
labeled X-ray image of the lumbar spine and corresponding SPSI™ data. This report is provided 
electronically to the investigational sites for use in the treatment planning of patients with lumbar 
stenosis. 
The SPSITM quantifies the magnitude of sagittal plane translation of the posterior-inferior corner of a 
vertebra in a direction defined by the superior endplate of the immediately inferior vertebra (Figure 1). 
The raw magnitude is first measured in units of percent endplate width (to control for variability on the 
size of the vertebra). This is then divided by the magnitude of intervertebral rotation (to control for 
variability in patient effort when asked to flex and extend). This ratio is then expressed as the number of 
standard deviations from the average TDPR that was found in asymptomatic volunteers with 
radiographically normal spines.  SPSITM > 2 informs a clinician that the TPDR is > 2 standard deviations 
above the average TPDR in the asymptomatic population. This provides for an objective diagnostic 
indicator for spinal instability defined as a specific, well-defined intervertebral motion metric that is 
outside the 95% confidence interval established for asymptomatic volunteers. The raw measurements of 
translation and rotation are obtained from lateral radiographs of the spine with the patient flexed 
forward and with the patient extended backwards. These measurements are obtained using a 
computerized system (QMA®, Medical Metrics, Inc) previously validated to have the accuracy and 
reproducibility required for measuring the small translations that occur in a healthy spine[20]. The 
measurement methods are also the same that were used to establish the level-specific TDPR expected in 
a healthy and asymptomatic spine.   
The computerized system along with the generated SPSI™ report is considered software as a medical 
device (SaMD). According to the European Union Medical Device Regulation (MDR), this type of device 
should be treated as an active device. Since this software is intended to provide information which is 
used to take decisions with diagnosis, it is considered a class IIa device (Rule 11 in Annex VIII of the 
European Union MDR).  
During the SPSI-01 clinical trial, the active production version of QMA used at Medical Metrics, Inc. to 
conduct regulated clinical trials business will be used to generate SPSI. At the start of the SPSI-01 clinical 
trial this will be version 1.35 or higher. The QMA version number used to generate SPSI will be specified 
on the SPSI report. New QMA versions will not change the validated algorithms used to generate SPSI. 
 

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FIGURE 1: The sagittal plane intervertebral translation between the flexed and extended positions of the spine is 
illustrated below by the magenta arrows. The dashed lines represent the direction in which the translation is 
measured, and this is defined by the superior endplate of the inferior vertebra. On the left side is shown the 
translation expected in a healthy spine. On the right is shown the translation that can occur when spinal motion 
is abnormal. In both the left and right sides, there is 13 degrees of intervertebral rotation between the flexed 
and extended positions of the spine. 
1.3. 
Manufacturer 
The device is manufactured by Medical Metrics, Inc. (MMI). MMI is a medical imaging company located 
at 2121 Sage Rd, Suite 350, Houston, Texas, USA. 
MMDx has contracted Medical Metrics, Inc. (MMI) to provide for importing of flexion-extension 
radiographs from the sites, for analyzing intervertebral motion using Quantitative Motion Analysis 
(QMA®) technology, and for calculating SPSITM. MMI has an established quality program for providing 
these services and for the software used to produce patient-specific reports that provide SPSITM data. 
The MMI quality system will be relied on for the purposes of the clinical investigation. MMI will deliver 
the SPSITM report to the clinical sites. 
1.4. 
Intended Purpose of the Device in the Clinical Investigation 
SPSITM is intended to be used preoperatively to objectively assess the sagittal plane translation per 
degree of rotation of the stenotic level.   
1.5. 
Intended populations and indication  
With respect to the clinical investigation as detailed in this clinical investigation plan, the intended 
population are patients who have previously consented to surgical treatment for lumbar spinal stenosis, 
and the specific indication will be for objectively assessing the preoperative intervertebral motion.  
1.6. 
Required Training and Experience 
Investigators will be extensively trained in the use of the SPSITM metric. During this training, investigators 
will be educated on all available current knowledge about SPSITM and will engage in discussion with 

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MMDx scientists to address and resolve all issues. Investigators and MMDx scientists will review and 
discuss multiple lumbar stenosis case examples with imaging and SPSITM reports and will identify any 
areas of question or concerns. This training will use methods similar to those used by Debono et al. [27]. 
The training will consist of the investigator developing an initial surgical plan after reviewing the imaging 
and clinical history. The investigator will then be provided with the SPSITM report and will be asked to 
develop a second surgical plan. The investigators will then discuss these results with MMDx with specific 
emphasis on the changes to the surgical plan that the SPSITM metric would support. The technicians at 
each site will be trained on how to obtain high-quality flexion and extension radiographs, that is where 
the subject has exerted sufficient effort when asked to flex and extend.  
1.7. 
Technical Procedure: SPSITM 
The SPSITM metric requires good-quality lumbar flexion-extension radiographs. An imaging protocol and 
training materials to obtain high-quality flexion-extension radiographs will be provided to all 
investigational sites. Radiographs will be electronically sent to MMI, where they will be imported into 
previously validated computer-assisted Quantitative Motion Analysis (QMA®) measurement software 
[20-22, 24]. Using the QMA® software, intervertebral translation and rotation will be measured at the 
treatment level identified by the investigator as well as the other levels between the first lumbar and the 
first sacral vertebrae.  
The subject will be withdrawn from the study if there is insufficient intervertebral rotation (< 5 degrees) 
at the treatment level to allow for a reliable assessment of SPSITM. This ≥ 5 degree threshold is required 
since without sufficient intervertebral motion, it is not possible to determine whether the intervertebral 
motion restraints are competent or whether abnormal motion can occur during flexion to extension. 
Motion < 5 degrees is considered to be within the neutral zone of intervertebral motion [28-30], where 
the spine is not sufficiently stressed to allow for detection of incompetent intervertebral motion 
restraints. SPSITM will be reported as “NA” at any level where there is < 5 degrees of rotation.  
Additionally, if there is excessive out-of-plane imaging (the x-ray beam was so oblique to the sagittal 
plane of the spine such that the four corners of the vertebral bodies could not be reliably identified), or if 
the entire spine was not captured in either the flexion or extension radiograph, or if there was any other 
image quality problem that prevents a reliable calculation of SPSITM, at the level the investigator had 
intended to treat, then the subject will also be withdrawn from the study. In these cases, the SPSITM for 
that level will be recorded as “NA” (not analyzable). These subjects will be withdrawn from the study and 
the end of the pre-surgery phase and will not receive any follow-up.   
The QMA® software will calculate SPSITM for each intervertebral level, as previously described, using 
normative reference data [17, 31]. A report that includes the SPSITM metric will be completed and 
returned to the investigator within 3 business days of receipt of both the flexion-extension radiographs 
and the pre- SPSITM surgical plan. MMI and MMDx will not have access to the pre- SPSITM surgical plan 
until after the SPSITM report has been delivered to the investigator.  
Prior to providing the investigator with the SPSITM report, the investigator must record and submit a 
initial surgical plan (pre-SPSITM surgical plan)detailing whether they plan to perform only decompression 
surgery, or decompression plus fusion, along with the specific level that they plan to treat. 

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The SPSITM report will be provided to the investigator no sooner than 24 hours after they submit the pre-
SPSITM surgical plan. This is to reduce potential bias from resistance to changing a plan that was just 
completed. After the investigator receives and reviews the SPSITM report, the investigator will record a 
second surgical plan (the post-SPSITM surgical plan).  
TABLE 1. APPLICATION OF PREOPERATIVE SPSITM IN ESTABLISHING A TREATMENT PLAN FOR LUMBAR SPINAL 
STENOSIS. 
Level 
 
Pre-SPSITM Surgical Plan 
 
Preop 
SPSITM metric 
Post-SPSITM Surgical Plan 
 
Surgical Plan 
Changed? 
Stenotic Decompress 
<2 
Decompress 
No 
Stenotic Decompress 
>2 
Decompress & Fuse 
Yes 
Stenotic Decompress & Fuse 
<2 
Decompress 
Yes 
Stenotic Decompress & Fuse 
>2 
Decompress & Fuse 
No 
 
2. JUSTIFICATION FOR CLINICAL INVESTIGATION DESIGN 
The design of the clinical investigation addresses the well-documented clinical need for a practical 
diagnostic test to allow a investigator to determine the stability of a level in the lumbar stenotic spine. 
The extensive number of clinical studies that have been conducted to assess whether decompression 
alone or decompression plus fusion is the best treatment option for patients diagnosed with lumbar 
stenosis is evidence for the desire for help in selecting the best treatment option. The primary reason for 
spine fusion surgery is to stop motion between vertebrae, and the primary justification for stopping 
motion is abnormal intervertebral motion. Several expert reviews conclude there is currently no 
validated metric for abnormal intervertebral motion. After those reviews were published, the Sagittal 
Plane Shear Index (referred to as QSI in the publication) was validated against the facet fluid sign [31]. 
The facet fluid sign is an indirect and imperfect diagnostic for abnormal motion, so the validation study is 
limited to showing the association between a high SPSITM and the presence of the facet fluid sign. A 
clinical investigation is needed to test the potential clinical efficacy of SPSITM in diagnosing abnormal 
motion, in order to use this diagnosis in the decision process on whether to add fusion to decompression 
of a stenotic lumbar level.  
3. OBJECTIVE AND HYPOTHESIS 
The primary objective of this clinical investigation is to determine if the SPSITM metric calculated from 
preoperative flexion-extension radiographs will change the surgical treatment plan that was initially 
recorded before accessing the SPSITM data.  
The associated hypothesis is that use of SPSITM will provide an objective stability metric that will change 
the surgical plan in a significant proportion of subjects. These changes can include the decision to fuse a 
level that was previously planned to only be decompressed, or to decompress a level that was previously 
planned to be decompressed and fused.  

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As a secondary objective of the current clinical investigation, clinical outcome data will be collected to 
test the hypothesis that the use of the preoperative SPSITM at the treatment level will result in improved 
clinical outcomes. The sample size for the current study is unlikely to be sufficient to test this hypothesis 
with a high level of statistical power, yet the data will help with design of subsequent research.  
The outcomes from this clinical investigation will serve as input for a subsequent clinical investigation to 
investigate the hypothesis that planning surgical treatment using the preoperative SPSITM at the 
treatment level(s) will result in improved clinical outcomes and a reduction in healthcare costs.  
4. DESIGN OF THE CLINICAL INVESTIGATION 
4.1. 
General 
This is a prospective, multi-center, single arm clinical investigation 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.  
4.1.1. Minimization of Bias 
This will be a single-arm clinical investigation where each investigator records a surgical plan (preprior to 
having access to the SPSITM results, and then approves or rejects changes to the treatment plan based on 
the results of the SPSITM metrics. Medical Metrics will provide the SPSITM report prior to having access to 
the investigator’s initial treatment plan. If the investigator rejects any changes to the surgical plan that 
would be required by an algorithmic application of the SPSITM results, the investigator will be required to 
record a justification for the rejection. Any bias against the SPSITM results would be evidence in a 
systematic rejection of changes required by an algorithmic application of the SPSITM results.  
4.1.2. Primary Endpoints 
The primary endpoint is the proportion of lumbar spinal stenosis treatment plans that change when 
SPSITM results are used in establishing the surgical plan.  
This endpoint was chosen for the current study, since the outcome is critical to the design of subsequent 
research to answer the more important question of whether use of preoperative SPSITM to select the 
optimal surgical treatment can improve clinical outcomes for patients. If the SPSITM metric rarely changes 
the surgical plan, it may not be worth further pursuit of the SPSITM metric. Conversely, if the SPSITM 
metric changes the plan in a significant proportion of cases, then that knowledge can be used to help 
design subsequent research. 
4.1.3. Secondary Endpoints 
The secondary endpoint is the comparison of clinical outcomes (as measured by Oswestry Disabilty Index 
(ODI) and Numeric Rating Scale (NRS) leg painleg pain) at 12 months and 24 months in lumbar stenosis 
patients where the surgical plan was in accordance with the SPSITM metric compared to historical 
controls.  

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If the SPSITM metrics change the surgical treatment plan in a significant proportion of cases, the next 
question is whether the changes that the SPSITM metrics support can lead to improved clinical outcomes, 
reduced reoperation rates, reduced use of pain medications and other clinical benefits. Without first 
documenting that investigators will use the SPSITM metrics to change the surgical treatment plan, a 
clinical study to determine if the SPSITM metrics can improve outcomes was not justified. However, the 
results of the proposed study will provide data that can be analyzed for evidence to support the 
hypothesis that use of SPSITM metrics can help to decide if fusion should be performed in addition to 
decompression of a stenotic lumbar level. That analysis will be valuable in the design of subsequent 
research.  
4.1.4. Exploratory Endpoints 
The following exploratory endpoints will be assessed:   
• 
Does the presence of a facet fluid sign as indicated by the investigator on preoperative MRI 
correlate to instabilities specified by SPSITM results? 
• 
What is the rate of instability (defined as a > 1 standard deviation increase in SPSITM) 12 months 
after decompression (no fusion) surgery, how do these rates compare to the published data (for 
example Guha et al [40] and Cushnie et al [41] ), and does the development of post-
decompression instability have an effect on the change in ODI or NRS scores relative to preop? 
• 
What are the reoperation rates at 12 months following decompression alone and following 
decompression plus fusion, and how do these rates compare to published data from studies 
where similar inclusion and exclusion criteria were used and patients were randomized to 
decompression alone or decompression plus fusion [3, 42]? 
• 
Does a nonunion following decompression plus fusion surgery have an effect on the change in 
ODI or NRS scores relative to preop ? 
4.1.5. Safety Endpoint 
The safety endpoint will be the nature and frequency of all adverse events observed during the clinical 
investigation including their timing, severity and relatedness to the investigational device and/or clinical 
investigation procedures. 
4.1.6. Equipment for Assessment 
High-quality flexion and extension radiographs are required for all subjects, both preoperatively and at 
12 months follow-up. High-quality is defined as visualizing all levels from L1 to S1 and having at least 5 
degrees of intervertebral rotation between flexion and extension, and the ability to clearly identify the 
four corners of each vertebra in both the flexion and extension radiographs. All radiographs must be 
provided in digital format, with images created by either a computer radiography or digital radiography 
system. Photographs of an x-ray on a view box are not acceptable. During site-screening, the x-ray 
equipment that will be used to collect the flexion-extension radiographs will be assessed for ability to 
provide the required quality. That includes the ability to easily position the x-ray source and detector to 
capture the spine in the fully flexed and fully extended positions, the ability to transmit x-rays to MMI in 

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digital format, as well as the ready availability of a walker required for patient support during image 
acquisition. 
4.1.7. Subject Replacement 
Subjects that are enrolled but who fail screening, or where the post-SPSITM surgical plan is not in 
accordance with the SPSITM metric (either because the investigator chooses not to follow the SPSITM 
metric, or the SPSITM for applicable level will be recorded as “NA”), or do not receive surgery, will be 
replaced.  
4.2. 
Investigational Device and Comparators 
No comparator device will be used to address the endpoint s of this study. 
4.3. 
Subjects 
4.3.1. Inclusion Criteria 
1) Symptoms consistent with single level lumbar spinal stenosis based on judgment and 
experience of the investigator  
2) Central and or foraminal stenosis confirmed by MRI as per the investigators clinical 
standards 
3) Grades 1 (10 to 25%) or 2 (26 to 50%) anterior or retro-spondylolisthesis using the 
Meyerding scale [43] 
4) Absence of lateral spondylolisthesis  
5) No prior lumbar spinal surgery 
6) Absence of American Society of Anesthesiologists (ASA) class IV or higher disease 
7) 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) 
8) Prior to viewing the spinal motion report, the surgical plan includes decompression or 
decompression and fusion of only one level 
9) Based on the investigators subjective assessment, the patient is able to flex and extend 
sufficiently to facilitate acceptable flexion and extension radiographs 
10) The fusion technique planned prior to viewing the spinal motion report is the following: 
Instrumented posterior (pedicle screws and rods) with / without PLIF cage 
11) Subject is able to understand and sign the study Informed Consent Form 
12) Subjects is at least 18 years of age.  
13) Subject has willingness and ability to comply with study procedures and visit schedules and 
able to follow oral and written instructions 
4.3.2. Exclusion Criteria 
9) Lumbar stenosis without spondylolisthesis 
10) 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 SPSITM 

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11) Pregnant women   
12) Scoliosis involving a lumbar curve greater than 10 degrees 
13) Stenosis at the level of a transitional vertebra 
14) Lateral spondylolisthesis (Coronal plane translational misalignment between vertebrae) 
15) Prior lumbar spinal surgery 
16) American Society of Anesthesiologists (ASA) class IV or higher disease 
4.3.3. Subject Withdrawal, Discontinuation and Study End 
A subject may withdraw or discontinue its participation at any time during the clinical investigation. 
He/she does not have to give a reason for withdrawal. Subjects may also be withdrawn from the clinical 
investigation by the investigator for non-compliance with clinical investigation plan, due to adverse 
events or if the investigator feels it is in the subject’s best interest to stop. Subjects withdrawn due to an 
adverse event will be followed until resolution of the adverse event or 30 days, whichever is the shorter 
time. Withdrawn subjects will be replaced in accordance with section 5.1.7, other withdrawn subjects 
will not be replaced.  The reason for subjects’ withdrawal or discontinuation will be recorded. Any data 
collected up until the time of withdrawal of the subject will be used for analysis. After study end, 
subjects will receive medical care according to standard of care, if applicable.  
4.3.4. Enrollment 
A subject is considered enrolled in the clinical investigation after they have provided written informed 
consent. A subject is considered treated per algorithm if the post- SPSITM surgical plan is in accordance 
with the SPSITM metric and if the subject has received surgery. A subject who is enrolled in the clinical 
investigation, but does not comply with the inclusion and exclusion criteria is considered a screen-failure.  
4.3.5. Total expected duration of the clinical investigation 
The clinical investigation is expected to take approximately up to 41 months including the enrollment 
period.  
4.3.6. Expected duration of subject’s participation  
Time from the subject’s consent for participation in the clinical investigation until surgery is up to 3 
months. Each subject will be followed for two year after surgery. The total expected duration is therefore 
up to up to 27 months.  
4.3.7. Enrollment period 
The enrollment period is expected to take approximately 14 months.  
4.3.8. Number of Subjects 
A total of 65 “treated per algorithm subjects” will be included. A subject is considered “treated per 
algorithm” if the post- SPSITM surgical plan is in accordance with the SPSITM report and if the subject has 
received surgery. Each clinical site contributing to the clinical investigation is expected to enroll at least 
20 subjects.   

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4.4. 
Procedures 
4.4.1. Schedule of Assessments 
TABLE 2. SCHEDULE OF ASSESSMENTS 
Assessment  
Visit 1 
Screening 
(≤ 3m to 
surgery) 
Pre-surgery 
phase 
Visit 2 
Surgery 
Visit 3* 
6m 
(±30d) 
Visit 4 
12m 
(±30d) 
Visit 5 
24m  
(±30d) 
Informed Consent 
X 
 
 
 
 
 
Demographics 
X 
 
 
 
 
 
Medical History  
X 
 
 
 
 
 
MRI 
X# 
 
 
 
 
 
Flexion/Extension X-rays 
X 
 
 
 
X 
 
Surgical Plan – pre SPSITM (P1) 
 
X 
 
 
 
 
SPSITM metric 
 
X 
 
 
X 
 
Surgical Plan – post SPSITM (P2) 
 
X 
 
 
 
 
Actual Surgery Performed (P3) 
 
 
X 
 
 
 
Oswestry Disability Index 
X 
 
 
X 
X 
X 
Numeric Rating Scale leg pain  
X 
 
 
X 
X 
X 
Patient satisfaction 
 
 
 
X 
X 
X 
Collection of reoperation data 
 
 
 
 
X 
X 
Collection of analgesic use data 
X 
 
 
 
X 
X 
Collection of Adverse Event data 
 
 
X 
 
X 
X 
# MRI done as part of standard of care.  
*This visit can be done over the phone. 
4.4.2. Visit 1 - Screening (≤3m to surgery)  
Consecutive lumbar stenosis patients that are planned to undergo lumbar decompression surgery or 
lumbar decompression plus fusion (based on symptoms, MRI-based confirmation of stenosis and severity 
of stenosis, and the investigator’s current clinical decision making process), will be asked to participate in 
the clinical investigation. Subjects must have an MRI exam available (performed per standard of care) 
that was used to confirm stenosis, as well as images that were used to document spondylolisthesis per 
the investigator’s standard of care. Prior to performing any activities/evaluations related to the clinical 
investigation, except the standard of care assessments, the subject must be thoroughly informed about 
all aspects of the study, including scheduled visits and activities, and must have signed the informed 
consent approved by the Ethics Committee. The screening visit may occur at any time within 3 months 
prior to surgery.   
During the screening visit the following assessments will be performed: 
4.4.2.1. 
Informed Consent 
Informed consent procedure will be performed as described in section 14.  

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4.4.2.2. 
Demographics 
Recording of patient baseline characteristics (e.e. age, gender, race, ethnicity) will be completed at 
screening. 
4.4.2.3. 
Medical History 
Recording of the subject’s relevant medical history (up to 5 years prior to screening) will be completed. 
Medical history is considered relevant when related to any of the study eligibility criteria, when it may 
influence the conduct of the study, or when it may affect any of the study endpoints, at the discretion of 
the investigator.  
4.4.2.4. 
Standard of care MRI 
A standard of care MRI exam will be used to confirm stenosis. The MRI exam is considered standard-of-
care in the management of spinal stenosis patients as it is the primary tool for verifying the presence and 
extent of stenosis. This MRI will also be used to determine the presence of facet fluid sign. The facet fluid 
sign is observation of an abnormally wide area of high signal intensity in the left and/or right facet joints. 
The observations will be done by the investigator. 
4.4.2.5. 
Pre-surgery Flexion-Extension Radiographs 
Flexion-extension radiographs will be obtained following a study-specific radiographic protocol to help 
assure that all x-rays will be of high-quality. The subject will be asked to watch a training video available 
on YouTube prior to collection of the radiographs. The training video will help to assure that the subject 
is aware of what is required of them to obtain radiographs of high-quality. During image acquisition, the 
subject will be asked to stand in front of a standard walker. Using the walker for support, the subject will 
bend forward as instructed in the video, and the flexion radiograph will be obtained. The subject will 
then be asked to use the walker for support as they bend backwards, as instructed in the training video, 
and the extension radiograph will be obtained. The flexion and extension radiographs will be 
electronically sent to MMI for analysis. The site will be responsible for assigning a study-specific 
identification number to the subject, and for providing that study-specific number to MMI along with the 
flexion and extension radiographs.  
4.4.2.6. 
Oswestry Disability Index 
The Oswestry Disability Index (ODI) version 2.1a is a validated patient reported outcome and is used to 
indicate the extent to which a person’s functional level is restricted by disability. The ODI consist of ten 
topics concerning intensity of pain, lifting, ability to care for oneself, ability to walk, ability to sit, sexual 
function, ability to stand, social life, sleep quality, and ability to travel. Each topic has 6 potential answers 
consisting of statements related to the topics. The subject checks the statements which most closely 
resembles their situation. Each question is scored on a scale of 0–5 with the first statement indicating 
the least amount of disability (scored 0) and the last statement indicating most severe disability (scored 
5). The scores for all questions answered are summed, then multiplied by two to obtain the index (range 
0 to 100). Zero equates to no disability and 100 relates to the most severe disability. The ODI will be 
collected on paper after which it will be entered into the electronic case report form (eCRF).   
4.4.2.7. 
Numerical Rating Scale leg pain 
The Numeric Rating Scale (NRS) leg pain is a patient reported outcome and is used to measures a 
person’s pain intensity with respect to leg pain. Subjects are to indicate on a scale from 1 to 10, the 

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average pain experienced in the previous week. Zero is equated to no pain and 10 equates to worst pain 
possible. The NRS leg pain will be collected on paper after which it will be entered into the eCRF.   
 
4.4.2.8. 
Analgesic Use 
Current analgesic use will be recorded at screening, 12 months and 24 months. The analgesic use 
questions as described by Clement et.al.[44]will be used to collect this information. Subjects will be 
asked if they use narcotic or non-narcotic pain relieving medication for their back problems, “yes 
regularly”, “yes sometimes”, or “no”.   
4.4.3. Pre-surgery phase 
4.4.3.1. 
Pre-SPSITM Surgical Plan   
After the screening visit, the investigator will complete an pre- SPSITM surgical plan.  This pre- SPSITM 
surgical plan will document the type of operation (decompression or decompression plus fusion) that 
would be performed at the operative level based on the investigator’s standard of care decision making. 
This pre- SPSITM surgical plan will be entered by the investigator into the eCRF and collected by the CRO 
managing the study. This surgical plan must be provided to the CRO before the SPSITM report is provided 
to the investigator. 
4.4.3.2. 
SPSITM Report 
The preoperative flexion-extension radiographs will be sent to MMI and the intervertebral motion will be 
analyzed using QMA®. To avoid any possibility of bias, MMI will not be informed what level the 
investigator intends to treat. Every level in the lumbar spine, from L1-L2 to L5-S1 will be analyzed. If 
there is insufficient intervertebral motion to reliably calculate SPSITM (< 5 degrees), or if there is excessive 
out-of-plane, or if not the entire spine was captured in either the flexion or extension radiograph, or if 
there was any other image quality problem that prevents a reliable calculation of SPSITM, then the SPSITM 
for that level will be recorded as “NA” (not analyzable). When the site receives the SPSITM report, the 
investigator will determine whether SPSITM is reported at NA at the level the investigator had intended to 
treat. These subjects will be withdrawn from the clinical investigation and the end of the pre-surgery 
phase and will not receive any follow-up.  In the event of subject being withdrawn from the study as a 
result of SPSITM being reported as NA, the flexion/extension protocol will be re-reviewed with the site to 
determine if interventions can be implemented at the site to avoid further situations where SPSITM 
cannot be reliably calculated.  
A SPSITM report that provides SPSITM will be completed and returned to the investigator after 24h, but 
within 3 business days of receipt of the flexion-extension radiographs at MMI and recording of the initial 
pre-SPSITM surgical plan at the CRO.  
4.4.3.3. 
Post- SPSITM Surgical Plan 
Based on review of the SPSITM report, the investigator will determine if the pre-SPSITM surgical plan needs 
to be modified as described in Table 1 of this clinical investigation plan. The investigator will review any 
modifications to the pre-SPSITM surgical plan and integrate the information in the SPSITM report along 
with their knowledge of the spine motion metrics and all other information that they obtain from the 
available imaging (MRI, CT, radiographs as per their standard clinical practice) to make a decision about 

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which levels to treat and what operation to perform at the stenotic level. The investigator will then 
complete a post-SPSITM surgical plan. By comparing the post-SPSITM surgical plan with the pre-SPSITM 
surgical plan, a determination will be made, per Table 1, whether the SPSITM report resulted in a change 
in the surgical plan. Those data will be used to address the primary endpoint: What proportion of 
surgical treatment plans were changed after integrating SPSITM metrics into the planning process.  
In addition, if the post-SPSITM surgical plan is inconsistent with the SPSITM report (e.g. SPSITM report 
indicates instability but the investigator plans to decompress only, or SPSITM report indicates stability but 
the investigator plans to decompress and fuse), the investigator will be asked to record the reason (e.g. 
SPSITM report indicates instability but there is a contraindication to fusion; or SPSITM report indicates 
stability but there is excessive fluid in the facet joint, suggesting instability, so level will be fused). If the 
post-SPSITM surgical plan is inconsistent with the SPSITM report, the subject will exit the study after the 
surgery has been performed  
4.4.4. Visit 2 - Surgery  
Surgery will be performed according to the post-SPSITM surgical plan . Decompression and fusion surgery 
will be conducted according to standard hospital procedures. After the surgery is complete, the 
investigator records any deviations and reason for deviations from the post-SPSITM surgical plan. For 
example, whereas the investigator may have planned to only decompress a level, they may find during 
surgery that a more extensive decompression was required than originally anticipated, and that requires 
fusion to avoid iatrogenic instability. Deviations from the post-SPSITM surgical plan are not considered 
protocol deviations. Additionally, details of the surgical procedures are collected.  
4.4.5. Visit 3 – 6 months (±30d) follow-up 
At 6 months (±30d) after surgery the subjects will undergo the following assessments: 
• 
Oswestry Disability Index 
o ODI will be collected as described in section 5.4.2.6. 
• 
Numeric Rating Scale Leg pain 
o NRS leg pain will be collected as described in section 5.4.2.7. 
• 
Patient satisfaction 
o Subjects will be asked if they are “satisfied”, “uncertain”, or “dissatisfied” with surgery 
outcome. 
This visit can be performed over the phone. 
4.4.6. Visit 4 – 12 months (±30d) follow-up.  
At 12 months (±30d) after surgery the subjects will undergo the following assessments: 
• 
Flexion/extension X-rays  
o Flexion/extension X-rays will be collected at the 12 month follow-up visit for all patients 
as described in section 5.4.2.5. 
• 
SPSITM metric 

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o The 12 month flexion-extension radiographs will be sent to MMI and the intervertebral 
motion will be analyzed using QMA® and the SPSITM metric will be calculated. The 12 
month SPSITM metric will be used to document whether the decompression procedure 
changed the stability of the treated level in subjects who underwent decompression 
surgery only.  Additionally, in subjects who underwent decompression and fusion 
surgery, the intervertebral rotation will be used to determine whether the fusion was 
successful at stopping motion between vertebrae. A level will be classified as fused if 
intervertebral rotation is < 2 degrees at the operated level and > 5 degrees at an 
adjacent level, and will be classified as not fused if rotation is ≥2 degrees[45]. It is 
expected that a proportion of patients will be considered indeterminate due to 
insufficient patient effort and those will not be included in the data analysis. 
• 
Oswestry Disability Index 
o ODI will be collected as described in section 5.4.2.6. 
• 
Numeric Rating Scale Leg pain 
o NRS leg pain will be collected as described in section 5.4.2.7. 
• 
Patient satisfaction 
o Subjects will be asked if they are “satisfied”, “uncertain”, or “dissatisfied” with surgery 
outcome. 
• 
Assessment of any reoperations.  
o The occurrence of any reoperations will be recorded along with the general type of 
reoperation (surgery at the originally treated levels or at the adjacent levels).  
• 
Analgesic use 
o Current analgesic use of pain medication will be recorded at screening, 12 months and 
24 months of the clinical investigation. Subjects will be asked of they use narcotic or 
non-narcotic pain relieving medication for their back problems, “yes regularly”, “yes 
sometimes”, or “no”.    
• 
Assessment of adverse events 
o Occurrence and assessment of all AEs will be recorded.  
4.4.7. Visit 5 – 24 months (±30d) follow-up   
At 24 months (±30d) after surgery the subjects undergo the following assessments: 
• 
Oswestry Disability Index 
o ODI will be collected as described in section 5.4.2.6. 
• 
Numeric Rating Scale Leg pain 
o NRS leg pain will be collected as described in section 5.4.2.7. 
• 
Patient satisfaction 
o Subjects will be asked if they are “satisfied”, “uncertain”, or “dissatisfied” with surgery 
outcome. 
• 
Assessment of any reoperations.  
o The occurrence of any reoperations will be recorded along with the general type of 
reoperation (surgery at the originally treated levels or at the adjacent levels).  
• 
Analgesic Use 

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o Current analgesic use of pain medication will be recorded at screening, 12 months and 
24 months of the clinical investigation. Subjects will be asked of they use narcotic or 
non-narcotic pain relieving medication for their back problems, “yes regularly”, “yes 
sometimes”, or “no”.    
• 
Assessment of adverse events 
o Occurrence and assessment of all AEs will be recorded.  
4.4.8. Activities Performed by Sponsor Representatives 
The sponsor of the clinical investigation (Medical Metrics Diagnostics, Inc) will work with MMI to provide 
investigators, X-ray technicians, and subjects with training materials. MMI will also be responsible for 
managing transfer of flexion-extension radiographs from the clinical sites to MMI where the QMA and 
calculation of SPSITM will be performed using previously validated methods. MMI will be responsible for 
getting the SPSITM report to the clinical site and for addressing any difficulties that the investigators 
encounter with the SPSITM reports. 
5. STATISTICAL CONSIDERATIONS 
Data analysis will be independently performed at MMDx and by a statistician independent of MMI. 
Discrepancies will be reviewed and resolved by the independent statistician. This will be done to reduce 
any potential errors. 
5.1. 
Primary Endpoint  
Proportion of surgical treatment plans changed after including SPSITM metrics  
The primary endpoint is the proportion of lumbar spinal stenosis treatment plans that change when 
SPSITM results are used in establishing the surgical plan. The proportions will be analyzed using a 
statistical test for proportions. The hypothesis to be tested is that SPSITM will result in a change in surgical 
plan for at least 15% of subjects. 
Three lumbar spinal stenosis treatment plans (surgical plans) will be identified per the following table: 
TABLE 3. DESCRIPTION OF SURGICAL PLANS 
Surgical Plan 
Description 
P1 
Pre-SPSITM  surgical plan  
P2 
Post-SPSITM  surgical pl 
P3 
Actual surgery performed 
 
The primary endpoint will be investigated using the proportion of P2 surgical plans that changed 
relative to the P1 plan. This describes the proportion of surgical treatment plans that appeared to 
change by inclusion of the SPSITM metric. The primary endpoint analyses will be done using the Per-
algorithm Population, defined as enrolled subjects who received surgery, where the post- SPSITM 
surgical plan is in accordance with the SPSITM metric and who do not have any major protocol 
deviations.  

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5.1.1. Subgroup analysis related to primary endpoint 
The data on changes to surgical plans will be further analyzed to better understand the changes as 
described below. This will be done for exploratory purposes and for planning subsequent research. 
The comparison between the pre-SPSITM surgical plan (P1), post-SPSITM surgical plan (P2) and the actual 
surgery performed (P3)  will be documented on a per-patient and per-level basis. With respect to the 
influence per-patient, the following table will be completed: 
TABLE 4. SUBGROUP ANALYSIS OF THE EFFECTS OF CHANGES TO SURGICAL PLAN ON SURGERIES PERFORMED 
Comparison 
Proportion of Patients 
No Change 
Increased 
Levels 
Fused 
Decreased 
Levels 
Fused 
P2 versus P1 
 
 
 
P3 versus P2 
 
 
 
P3 versus P1 
 
 
 
5.2. 
Secondary Endpoint 
Comparison of clinical outcomes in lumbar stenosis patients where surgical planning including SPSITM 
compared to historical controls 
After 12 month (± 30 days)  the change from baseline (12 month minus PreOp) in both the ODI, and the 
region-specific NRS [46-48] leg pain score will be calculated for each subject in the study. These 
outcomes instruments have been used in many spine studies, are well-accepted, and there is reference 
data in the literature that can be used to help interpret results from the proposed study. ThesSecondary 
endpoint analyses will be done using the per-algorithm population. The per-algorithm population 
includes all patients where the surgeon modified the initial surgical plan as needed per the algorithm 
defined in Table 1. 
The purpose of the ODI is “To indicate the extent to which a person’s functional level is restricted by 
disability”1. The mean and standard deviation for the 12 month ODI, and the change in the 12 month ODI 
relative to baseline in study subjects will be compared (using a T-test) to the mean and standard 
deviations expected from peer-reviewed publications that have randomized lumbar stenosis patients to 
either decompression only or decompression and fusion. Most of this literature is already available at 
MMDx but an updated search will be completed using Google Scholar and pubmed prior to the data 
analysis so that any recent literature can be included. The data analysis will be repeated after 24 month 
outcomes have been collected.  
The comparison of study data to historical control data can be done for each historical control study that 
has comparable data. The expected rate will be based on a review of the available literature. Many peer-
 
1 https://eprovide.mapi-trust.org/instruments/oswestry-disability-index 

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reviewed publications do not report means and standard deviations in a manner that allows for use of 
their data directly as a historical control [4] although the data can nevertheless help to support choice of 
numbers to use. Table 5 summarizes some of the studies that provide historical control data. 
Most of the prior literature reports a similar improvement in outcome scores for patients treated with 
decompression only versus decompression and fusion. The null hypothesis is that the use of SPSITM 
report by investigators to select levels to treat and the type of surgery to use will NOT effect the 
improvement in clinical outcomes for lumbar stenosis patients treated with decompression only or 
decompression plus fusion. The null hypothesis would be rejected if, when SPSITM is used to select 
treatment, the improvement in outcome scores is significantly better than reported in the peer-reviewed 
literature.  Although it is unlikely that the sample size in the current study will be sufficient to address 
the null hypothesis with an acceptable significance level and statistical power, the data from this pilot 
study will be used to help establish sample sizes required to more definitively document the clinical 
benefit of SPSITM for selecting levels and treatments in lumbar spinal stenosis patients. 
TABLE 5: A SAMPLING OF PAPERS THAT PROVIDE POTENTIAL REFERENCE ODI AND NRS DATA. A MORE COMPLETE 
LIST WOULD BE GENERATED PRIOR TO INTERPRETING THE STUDY RESULTS BASED ON A COMPLETE LITERATURE 
REVIEW AND CONSULTATION WITH THE PARTICIPATING INVESTIGATORS TO ASSURE THAT THE HISTORICAL 
CONTROL DATA INCLUDE THOSE PUBLICATIONS THAT THE INVESTIGATOR USES TO INFORM PATIENTS ON 
EXPECTED OUTCOMES. 
Study 
FU 
Months 
N 
Delta ODI 
Delta NRS Leg Pain 
D 
D&F 
D 
D&F 
Weinstein 
2010 
24 
109 
-16.1(19.8) 
 
 
 
Austevoll 
12 
260/260 
-17.5[16.1] 
-19.7[18.3] 
-3.0[2.9] 
-3.5[2.8] 
Ghogawala 
12 
35/31 
-22.2[NR] 
-26.1[NR] 
NR 
NR 
Key to abbreviations in Table 5: 
Delta ODI: The change in the Oswestry Disability Index at follow-up (FU) relative to PreOp. 
Delta NRS Leg Pain: The change in the visual-analog score for patient reported leg pain. 
D: Decompression surgery only 
D&F: Decompression surgery and fusion surgery 
5.3. 
Exploratory Endpoints 
5.3.1. Exploratory research question 1: Association between preoperative SPSITM and the 
facet fluid sign 
The facet fluid sign is observation of an abnormally wide area of high signal intensity in the left and/or 
right facet joints. Prior research has demonstrated that SPSITM (labeled QSI in the paper) is significantly 
elevated in the presence of the facet fluid sign [31]. Data from the current study will be analyzed for 
supporting or refuting evidence to the prior observation. However, due to the expense of image transfer 
and independent radiologist assessment of the MRI exams, the observations by the investigators will be 
used. Each investigator will be provided with training material on how to interpret the facet fluid sign. 

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This training materials is based on training that was successfully used in the prior publication [31]. 
Analysis of variance tests (if data are normally distributed) or the Kruskal –Wallis equality-of-populations 
rank test will be used to test whether SPSITM is significantly greater at levels identified by the 
investigators as having a facet fluid sign. This endpoint will be analyzed using the Safety Population. 
5.3.2. Exploratory research question 2: Proportion of levels treated using decompression 
only that have an increase in SPSITM at 12 months 
As previously noted, one common justification for adding fusion surgery to surgery for decompression of 
lumbar stenosis, is that the decompression may create an instability that will later need to be treated. 
The fusion surgery is sometimes used prophylactically against the possibility of developing instability 
following decompression surgery. However, if instability rarely develops, this justification is not 
appropriate. Multiple research studies have been published providing data on the low-proportion of 
patients that develop instability following decompression-only surgery [7, 40, 49-54]. However, it is 
somewhat difficult to fully accept those studies since there are also scientific reviews concluding that 
there is currently no validated method for diagnosing instability [13]. Therefore, the proportion of 
patients where SPSITM increases significantly following decompression-only surgery will be determined 
using an objective metric for spinal stability. This analysis will be completed as simple descriptive 
statistics and also using a simple test of proportions in comparison to the proportion of patients reported 
in prior publications. There is some evidence that a high translation-per-degree-of rotation can be 
associated with low-back symptoms [19]. In addition, there is some evidence that increased 
spondylolisthesis following decompression may be associated with worse outcomes [55, 56], so a binary 
classification (significantly increased SPSITM versus no change in SPSITM) will be analyzed as a covariate 
when analyzing clinical outcome scores. If the change in SPSITM is greater than +0.75, then that patient 
will be classified as having increased SPSITM. Otherwise, the patient will be classified as having no 
significant change. This endpoint will be analyzed using the Per-algorithm Population. 
5.3.3. Exploratory research question 3: Reoperation rate at 1 and 2 years following surgery 
To provide confidence that clinical results of the current study are consistent with previously published 
data, the occurrence of any reoperations will be recorded along with the general type of reoperation 
(surgery at the originally treated levels or at the adjacent levels). Some reoperations would be expected 
based on previously published data (for example Bydon et al [57]). This endpoint will be analyzed using 
the Per-algorithm Population. 
5.3.4. Exploratory research question 4: Dependence of outcomes on non-union of levels 
treated using fusion surgery 
The clinical outcomes following surgical treatment of lumbar spinal stenosis can depend on multiple 
factors. It can be difficult to determine the true effect of a specific surgical procedure on clinical 
outcomes, without reliably accounting for the cofactors that may affect outcomes. Unfortunately, there 
are limited data available to determine how best to account for cofactors. Although not all published 
data are consistent, there is evidence that fusion surgeries where the surgery fails to stop motion 
between vertebrae may have worse outcomes than in patients where the fusion surgery stops motion 

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between vertebrae. For this reason, per-protocol flexion-extension radiographs will be obtained at 12 
months for those patients treated with decompression plus fusion surgery. The flexion-extension 
radiographs will then be used to calculate intervertebral rotation at the treated level. If the rotation is 
greater than 2 degrees, then that level will be classified as a non-union. This threshold of motion has 
been used in multiple prior studies, so some reference data are available.  It is likely that a much larger 
sample size would likely be required to rigorously assess this cofactor, so this exploratory endpoint is not 
being used to power the current study. This endpoint will be analyzed using the Per-algorithm 
Population. 
5.4. 
Safety endpoint 
An overall summary of AEs will be provided including the number of events and percent of subjects with 
any AEs, SAEs, and USADEs. For each type of event, the number of events and number and percent of 
subjects with the event will be provided in a table. Separate summaries of all adverse events will be 
summarized by relationship to device and procedure. The safety endpoint will be analyzed using the 
safety population.   
5.5. 
Sample Size 
The primary endpoint will be investigated using the proportion of surgical plans recorded after 
integrating SPSITM  metrics that changed relative to the surgical plan recorded prior to accessing the 
SPSITM  metrics. Since all of the investigators will have extensive experience with the surgical treatment of 
lumbar spinal stenosis patients, it is reasonable to assume that each individual surgeon would 
consistently generate the same treatment plan if they managed the same patient at multiple visits. 
published data was found documenting this assumption, but the clinicians tend to agree with that 
assumption.  
Nevertheless, we will allow for the possibility that 10% of treatment plans could differ if surgeons were 
to generate treatment plans at multiple visits. Further, we will assume that for the SPSITM metrics to be 
accepted as clinically effective, then at least 15% of treatment plans would need to be changed by 
inclusion of SPSITM  metrics. With alpha = 5% and power = 90%, a simple test of proportions indicates that 
a sample size of 59 patients would be required to determine if the proportion of treatment plans 
changed after including SPSITM metrics was at least 25% assuming that 10% of treatment plans could 
change due to variability in how surgeons establish treatment plans (Stata/IC ver 15, StatCorp, College 
Station, TX).  
To allow for up to 7 patients that need to be dropped from the analysis for various reasons, up to 65 
patients that meet all inclusion and exclusion criteria will be entered into the study to assure at least 59 
patients in the final data analysis.  Each clinical site contributing to the study must aim to enroll at least 
20 patients.  
Note that this sample size requirement assumes that the investigators will follow any changes in surgical 
plan that the SPSITM metrics would support. Since investigators can choose to reject the changes 
supported by the SPSITM metrics, additional subjects will be enrolled to replace those where the 
investigator chose to reject any SPSITM -based changes.  

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5.6. 
Analysis Populations 
Data analysis with respect to the primary and secondary endpoints will be completed for two defined 
populations: 
1. Safety Population: Enrolled subjects who receive surgery, regardless of whether the investigator 
changed the surgical plan to conform with the results of the SPSITM metrics. 
2. Per-algorithm Population: Enrolled subjects who received surgery, where the post- SPSITM surgical 
plan is in accordance with the SPSITM metric and who do not have any major protocol deviations.  
5.7. 
Missing Data 
No imputation or adjustments for missing data will be performed. All available data will be analyzed per 
the defined analysis populations. 
5.8. 
Stopping Rules 
The proportion of surgical treatment plans that changed after including SPSITM metrics will be monitored 
throughout the clinical investigation. If it becomes clear that the proportion of changed reports is so low 
that the data are unlikely to support the value of SPSITM in surgical treatment planning, then the study 
may be stopped early. This decision would be made in consultation with the Principal Investigators to 
assure that they agree with the conclusion that the SPSITM reports are proving to be of no or only very 
limited value in surgical treatment planning. 
5.9. 
Interim analysis 
An interim analysis will be performed after the last subject has completed the surgery visit. 

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6. BIBLIOGRAPHY  
 
 
1. 
Försth P, Ólafsson G, Carlsson T, Frost A, Borgström F, Fritzell P, Öhagen P, Michaëlsson K, 
Sandén B: A randomized, controlled trial of fusion surgery for lumbar spinal stenosis. N Engl J 
Med 2016, 2016(374):1413-1423. 
2. 
Siebert E, Prüss H, Klingebiel R, Failli V, Einhäupl KM, Schwab JM: Lumbar spinal stenosis: 
syndrome, diagnostics and treatment. Nature Reviews Neurology 2009, 5(7):392-403. 
3. 
Machado GC, Ferreira PH, Yoo RI, Harris IA, Pinheiro MB, Koes BW, van Tulder MW, Rzewuska M, 
Maher CG, Ferreira ML: Surgical options for lumbar spinal stenosis. The Cochrane Library 2016. 
4. 
Ghogawala Z, Dziura J, Butler WE, Dai F, Terrin N, Magge SN, Coumans J-VC, Harrington JF, Amin-
Hanjani S, Schwartz JS: Laminectomy plus fusion versus laminectomy alone for lumbar 
spondylolisthesis. New England Journal of Medicine 2016, 374(15):1424-1434. 
5. 
Deyo RA, Mirza SK, Martin BI, Kreuter W, Goodman DC, Jarvik JG: Trends, major medical 
complications, and charges associated with surgery for lumbar spinal stenosis in older adults. 
JAMA 2010, 303(13):1259-1265. 
6. 
Raad M, Donaldson CJ, El Dafrawy MH, Sciubba DM, Riley III LH, Neuman BJ, Kebaish KM, 
Skolasky RL: Trends in isolated lumbar spinal stenosis surgery among working US adults aged 
40–64 years, 2010–2014. Journal of Neurosurgery: Spine 2018:1-7. 
7. 
Iida Y, Kataoka O, Sho T, Sumi M, Hirose T, Bessho Y, Kobayashi D: Postoperative lumbar spinal 
instability occurring or progressing secondary to laminectomy. Spine 1990, 15(11):1186-1189. 
8. 
Abumi K, Panjabi MM, Kramer KM, Duranceau J, Oxland T, Crisco JJ: Biomechanical evaluation of 
lumbar spinal stability after graded facetectomies. Spine 1990, 15(11):1142-1147. 
9. 
Ben-Galim P, Reitman CA: The distended facet sign: an indicator of position-dependent spinal 
stenosis and degenerative spondylolisthesis. Spine J 2007, 7(2):245-248. 
10. 
Rihn JA, Lee JY, Khan M, Ulibarri JA, Tannoury C, Donaldson WF, III, Kang JD: Does lumbar facet 
fluid detected on magnetic resonance imaging correlate with radiographic instability in 
patients with degenerative lumbar disease? Spine 2007, 32(14):1555-1560. 
11. 
Chaput C, Padon D, Rush J, Lenehan E, Rahm M: The significance of increased fluid signal on 
magnetic resonance imaging in lumbar facets in relationship to degenerative spondylolisthesis. 
Spine 2007, 32(17):1883-1887. 
12. 
Coulier B: The spectrum of vacuum phenomenon and gas in spine. JBR BTR 2004, 87(1):9-16. 
13. 
Leone A, Guglielmi G, Cassar-Pullicino VN, Bonomo L: Lumbar Intervertebral Instability: A 
Review1. Radiology 2007, 245(1):62. 
14. 
Hasegawa K, Kitahara K, Shimoda H, Ishii K, Ono M, Homma T, Watanabe K: Lumbar 
degenerative spondylolisthesis is not always unstable: clinicobiomechanical evidence. Spine 
2014, 39(26):2127-2135. 
15. 
Lefkowitz DM, Quencer RM: Vacuum facet phenomenon: a computed tomographic sign of 
degenerative spondylolisthesis. Radiology 1982, 144(3):562-562. 
16. 
Hipp JA, Guyer RD, Zigler JE, Ohnmeiss DD, Wharton ND: A new method correlating an objective 
radiographic metric for lumbar spine instability and the facet fluid sign on MRI. In: Int Society 
Advancement of Spine Surgery: 2015; San Diego; 2015. 
17. 
Staub BN, Holman PJ, Reitman CA, Hipp JA: Sagittal plane lumbar intervertebral motion during 
seated flexion-extension in 658 asymptomatic, non-degenerated levels. J Neurosurgery Spine 
2015, 23(6):731-738. 
18. 
Hipp JA, Newman P, Avila-Montes O: Toward standardization of lumbar flexion-extension 
studies. In: ISASS. Toronto; 2018: 529. 

SPSI-01 
Page 26 of 28    
July 14, 2023 
Confidential 
 
Medical Metrics Diagnostics, Inc 
19. 
Weiler PJ, King GJ, Gertzbein SD: Analysis of sagittal plane instability of the lumbar spine in 
vivo. Spine 1990, 15(12):1300-1306. 
20. 
Zhao KD, Yang C, Zhao C, Stans AA, An KN: Assessment of noninvasive intervertebral motion 
measurements in the lumbar spine. JBiomechanics 2005, 38(9):1943-1946. 
21. 
Pearson AM, Spratt KF, Genuario J, McGough W, Kosman K, Lurie J, Sengupta DK: Precision of 
lumbar intervertebral measurements: Does a computer-assisted technique improve reliability? 
Spine 2011, 36(7):572-580. 
22. 
Patwardhan AG, Havey RM, Wharton ND, Tsitsopoulos PP, Newman P, Carandang G, Voronov LI: 
Asymmetric motion distribution between components of a mobile-core lumbar disc prosthesis: 
an explanation of unequal wear distribution in explanted CHARITE polyethylene cores. J Bone 
Joint Surg Am 2012, 94(9):846-854. 
23. 
Auerbach J, Namdari S, Milby A, White A, Reddy S, Lonner B, Balderston R: The Parallax Effect in 
the Evaluation of Range of Motion in Lumbar Total Disc Replacement. SAS Journal 2008, 
2(4):184-188. 
24. 
Zhao KD, Ben-Abraham EI, Magnuson DJ, Camp JJ, Berglund LJ, An K-N, Bronfort G, Gay RE: Effect 
of Off-Axis Fluoroscopy Imaging on Two-Dimensional Kinematics in the Lumbar Spine: A 
Dynamic In Vitro Validation Study. Journal of Biomechanical Engineering 2016, 138(5):054502. 
25. 
Peul WC, Moojen WA: Fusion for Lumbar Spinal Stenosis—Safeguard or Superfluous Surgical 
Implant? New England Journal of Medicine 2016, 374(15):1478-1479. 
26. 
Austevoll IM, Gjestad R, Brox JI, Solberg TK, Storheim K, Rekeland F, Hermansen E, Indrekvam K, 
Hellum C: The effectiveness of decompression alone compared with additional fusion for 
lumbar spinal stenosis with degenerative spondylolisthesis: a pragmatic comparative non-
inferiority observational study from the Norwegian Registry for Spine Surgery. European Spine 
Journal 2017, 26(2):404-413. 
27. 
Debono B, Lonjon G, Galovich LA, Kerever S, Guiot B, Eicker S-O, Hamel O, Ringel F: Indication 
Variability in Degenerative Lumbar Spine Surgery. Spine 2018, 43(3):185-192. 
28. 
Panjabi MM: The stabilizing system of the spine. Part II. Neutral zone and instability 
hypothesis. Journal of Spinal Disorders 1992, 5(4):390-396; discussion 397. 
29. 
Crawford NR, Peles JD, Dickman CA: The spinal lax zone and neutral zone: measurement 
techniques and parameter comparisons. Journal of Spinal Disorders & Techniques 1998, 
11(5):416-429. 
30. 
Sengupta DK, Fan H: The Basis of Mechanical Instability in Degenerative Disc Disease: A 
Cadaveric Study of Abnormal Motion Versus Load Distribution. Spine 2014, 39(13):1032-1043. 
31. 
Hipp JA, Guyer RD, Zigler JE, Ohnmeiss DD, Wharton ND: Development of a novel radiographic 
measure of lumbar instability and validation using the facet fluid sign. Int J Spine Surgery 2015, 
9, Article 37. 
32. 
Hasegawa K, Shimoda H, Kitahara K, Sasaki K, Homma T: What are the reliable radiological 
indicators of lumbar segmental instability? Journal of Bone and Joint Surgery-British Volume 
2011, 93(5):650. 
33. 
Bogduk N: Clinical and Radiological Anatomy of the Lumbar Spine, Chapt 16: Elsevier Health 
Sciences; 2012. 
34. 
Hipp JA, Chan EF: Threshold Limit Graphical Approach to Understanding Outcome Predictive 
Metrics: Data from the Osteoarthritis Initiative. Cureus 2017, 9(7). 
35. 
Mettler FA, Huda W, Yoshizumi TT, Mahesh M: Effective Doses in Radiology and Diagnostic 
Nuclear Medicine: A Catalog1. Radiology 2008, 248(1):254. 
36. 
Cardis E, Vrijheid M, Blettner M, Gilbert E, Hakama M, Hill C, Howe G, Kaldor J, Muirhead C, 
Schubauer-Berigan M: Risk of cancer after low doses of ionising radiation: retrospective cohort 
study in 15 countries. BMJ 2005, 331(7508):77. 

SPSI-01 
Page 27 of 28    
July 14, 2023 
Confidential 
 
Medical Metrics Diagnostics, Inc 
37. 
Bolus NE: NCRP report 160 and what it means for medical imaging and nuclear medicine. 
Journal of nuclear medicine technology 2013:jnmt. 113.128728. 
38. 
Desai A, Bekelis K, Ball PA, Lurie J, Mirza SK, Tosteson TD, Zhao W, Weinstein JN: Outcome 
variation across centers after surgery for lumbar stenosis and degenerative spondylolisthesis: 
the SPORT experience. Spine 2013, 38(8):678. 
39. 
Resnick DK, Choudhri TF, Dailey AT, Groff MW, Khoo L, Matz PG, Mummaneni P, Watters WC, III, 
Wang J, Walters BC et al: Guidelines for the performance of fusion procedures for degenerative 
disease of the lumbar spine. Part 9: fusion in patients with stenosis and spondylolisthesis. 
JNeurosurgSpine 2005, 2(6):679-685. 
40. 
Guha D, Heary RF, Shamji MF: Iatrogenic spondylolisthesis following laminectomy for 
degenerative lumbar stenosis: systematic review and current concepts. Neurosurgical focus 
2015, 39(4):E9. 
41. 
Cushnie D, Johnstone R, Urquhart JC, Gurr KR, Bailey SI, Bailey CS: Quality of Life and Slip 
Progression in Degenerative Spondylolisthesis Treated Nonoperatively. Spine 2018, 
43(10):E574-E579. 
42. 
Jansson K-Å, Németh G, Granath F, Blomqvist P: Spinal stenosis re-operation rate in Sweden is 
11% at 10 years—a national analysis of 9,664 operations. European spine journal 2005, 
14(7):659-663. 
43. 
Meyerding HW: Spondylolisthesis as an etiologic factor in back pain. JAMA 1938, 111:1971. 
44. 
Clement RC, Welander A, Stowell C, Cha TD, Chen JL, Davies M, Fairbank JC, Foley KT, Gehrchen 
M, Hagg O: A proposed set of metrics for standardized outcome reporting in the management 
of low back pain. Acta orthopaedica 2015, 86(5):523-533. 
45. 
Putzier M, Strube P, Funk J, Gross C, Perka C: Periosteal cells compared with autologous 
cancellous bone in lumbar segmental fusion. Journal of Neurosurgery: Pediatrics 2008, 8(6). 
46. 
Childs JD, Piva SR, Fritz JM: Responsiveness of the numeric pain rating scale in patients with low 
back pain. Spine 2005, 30(11):1331-1334. 
47. 
Ostelo RW, Deyo RA, Stratford P, Waddell G, Croft P, Von Korff M, Bouter LM, Henrica C: 
Interpreting change scores for pain and functional status in low back pain: towards 
international consensus regarding minimal important change. Spine 2008, 33(1):90-94. 
48. 
Van Lerbeirghe J, Van Schaeybroeck P, Robijn H, Rasschaert R, Sys J, Parlevliet T, Hallaert G, Van 
Wambeke P, Depreitere B: Cross-cultural adaptation and validation of the Dutch version of the 
core outcome measures index for low back pain. European Spine Journal 2018, 27(1):76-82. 
49. 
Johnsson KE, Willner S, Johnsson K: Postoperative Instability After Decompression For Lumbar 
Spinal Stenosis. Acta Orthop Scand (in press) 1985:1-23. 
50. 
Johnsson KE, Redlund-Johnell I, Uden A, Willner S: Preoperative and postoperative instability in 
lumbar spinal stenosis. Spine 1989, 14(6):591-593. 
51. 
Fox MW, Onofrio BM, Hanssen AD: Clinical outcomes and radiological instability following 
decompressive lumbar laminectomy for degenerative spinal stenosis: a comparison of patients 
undergoing concomitant arthrodesis versus decompression alone. Journal of Neurosurgery 
1996, 85(5):793-802. 
52. 
Katz JN, Lipson S, Larson M, McInnes J, Fossel A, Liang M: The outcome of decompressive 
laminectomy for degenerative lumbar stenosis. The Journal of bone and joint surgery American 
volume 1991, 73(6):809-816. 
53. 
Ghogawala Z, Resnick DK, Glassman SD, Dziura J, Shaffrey CI, Mummaneni PV: Randomized 
controlled trials for degenerative lumbar spondylolisthesis: which patients benefit from 
lumbar fusion? Journal of Neurosurgery: Spine 2017, 26(2):260-266. 
54. 
Blumenthal C, Curran J, Benzel EC, Potter R, Magge SN, Harrington Jr JF, Coumans J-V, 
Ghogawala Z: Radiographic predictors of delayed instability following decompression without 

SPSI-01 
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July 14, 2023 
Confidential 
 
Medical Metrics Diagnostics, Inc 
fusion for degenerative Grade I lumbar spondylolisthesis: Clinical article. Journal of 
Neurosurgery: Spine 2013, 18(4):340-346. 
55. 
Bridwell KH, Sedgewick TA, O'Brien MF, Lenke LG, Baldus C: The role of fusion and 
instrumentation in the treatment of degenerative spondylolisthesis with spinal stenosis. 
Journal of Spinal Disorders 1993, 6(6):461-472. 
56. 
Mullin BB, Rea GL, Irsik R, Catton M, Miner ME: The effect of postlaminectomy spinal instability 
on the outcome of lumbar spinal stenosis patients. Journal of Spinal Disorders 1996, 9(2):107-
116. 
57. 
Bydon M, Macki M, Kerezoudis P, Sciubba DM, Wolinsky J-P, Witham TF, Gokaslan ZL, Bydon A: 
The incidence of adjacent segment disease after lumbar discectomy: a study of 751 patients. 
Journal of Clinical Neuroscience 2017, 35:42-46.