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U.S. Department of Health and Human Services

Post-Approval Studies (PAS)

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The FDA has the authority to require sponsors to perform a post-approval study (or studies) at the time of approval of a premarket approval (PMA), humanitarian device exemption (HDE), or product development protocol (PDP) application. Post-approval studies can provide patients, health care professionals, the device industry, the FDA and other stakeholders information on the continued safety and effectiveness (or continued probable benefit, in the case of an HDE) approved medical devices. This database allows you to search Post-Approval Study information by applicant or device information.

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LTOS Study

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Application Number P040001 / PAS001
Current Plan Approved 12/08/2006
Study Name LTOS Study
General Study Protocol Parameters
Study Design Prospective Cohort Study
Data Source New Data Collection
Comparison Group No Control
Analysis Type Descriptive
Study Population Transit. Adolescent B (as adults) : 18-21 yrs, Adult: >21
Detailed Study Protocol Parameters
Study Design Description The Long-Term Outcomes Study (LTOS) is a prospective, multi-center study of patients who received the X-STOP device in the pre-market trial, crossover study (COS) or continued access program (CAP).
Study Population Description The study population is comprised of patients aged 50 years and older who have lumbar spinal stenosis, suffers symptoms of neurogenic intermittent claudication, have moderately impaired physical function, and are able to relieve their symptoms when they bend forward or flex their spines. This device is indicated for treatment of patients aged 50 or older suffering from neurogenic intermittent claudication secondary to a confirmed diagnosis of lumbar spinal stenosis (with X-Ray, MRI, and/or CT evidence of thickened ligamentum flavum, narrowed lateral recess and/or central canal narrowing). The X STOP is indicated for those patients with moderately impaired physical function who experience relief in flexion from their symptoms of leg/buttock/groin pain, with or without back pain, and have undergone a regimen of at least 6 months of nonoperative treatment. The X STOP may be implanted at one or two lumbar levels in patients in whom operative treatment is indicated at no more than two levels.
Sample Size The sample size is 155 potential patients who participated in the IDE.
Data Collection The primary effectiveness endpoint is treatment response, defined as follows:- Clinically significant improvement (by at least 5 points) in the Symptom Severity (SS) Domain of the ZCQ compared to the preoperative baseline.-Clinically significant improvement (by at least 0.5 points) in the Physical Function (PF) domain of the ZCQ compared to the preoperative baseline score

-Patient satisfaction with treatment defined by Patient Satisfaction score at the five-year postoperative evaluation.- No additional surgery for lumbar stenosis performed.- No dislodgement of the implant. - No device-related complications. Secondary effectiveness endpoints encompass mean individual ZCQ domain scores and mean SF-36 scores.Radiographic examination will permit the assessment of the maintenance of distraction. Distraction will be maintained if the distance between the spinous processes is not reduced by more than 4 mm from the distance observed at the six-week clinical assessment.
Follow-up Visits and Length of Follow-up The duration of patient follow-up will be 5 years. The follow-up schedule for the study is delineated below:- 24 months following initial enrollment for those patients actively participating in either the CAP or COS at the time of LTOS study initiation- 36 months for all CAP/COS patients following enrollment into their original IDE study- 48 months for all CAP/COS patients following enrollment into their original IDE study - 60 months for all CAP/COS patients following enrollment into their original IDE study, > 60 months, for all Pivotal Trial patients following their IDE study enrollment into the X-STOP group. All patients in the Pivotal Trial have already reached their fifth postoperative year; therefore they will have in excess of 60 months device experience at their next follow-up visiT. At every office visit, patients will complete the ZCQ and the SF-36 prior to physician examination. Patients will undergo a complete clinical examination with emphasis on the neurological assessment for strength, reflexes, sensation, and pain related to the diseased intervertebral space.

Radiographic examination, anterior/posterior (AP) and lateral x-rays, will be performed on all LTOS patients at their 5 year postoperative visit. Radiographic examination will also be performed on LTOS patients at 24 months. Data collected from the radiographic examinations will include the position of the X-STOP, the status of the X-STOP, the status of the spinous process, laminae and facets, and the distance between the tips of the spinous processes.

Final Study Results
Interim Safety Information Radiographic findings for 63 subjects are provided. Radiographs were assessed for maintenance of distraction, device positioning, device condition, and status of the spinous process, laminae, and facets. As previously reported in the first amendment to the 24-month interim report, two subjects (subjects 01-022 and 01-024) declined to participate in the radiographic examination portion of the 60-month clinical follow-up. Neither of these subjects reported any adverse events, as shown in Tables 8 and 9.

Per the March 27, 2009, amendment to the 24-month interim study status report (P040001/R011), Medtronic has contacted the core radiographic lab to review film quality and radiographic evaluation procedures to improve interpretation of LTOS data. In four subjects, the 12-month radiographic assessment was used as baseline in lieu of the 6-week radiographic assessment, as 6-week films were not available (subjects 01-002, 01-006, 01-008, 05-002).
Number of Patients A total of 69 study subjects were enrolled.
Number of Sites A total of six study sites were enrolled.
Follow-up Rate The follow-up rate for enrolled patients was 97.1%.
Safety Findings A total of 56 patients were analyzed radiographically at the 5-year postoperative assessment (29 had single-level implants and 27 had multilevel implants). In those with single-level implants,

27/69 (39.1%) patients maintained distraction for at least 5 years. In those with multilevel implants, 23/69 (33.3%) patients maintained distraction at all levels for at least 5 years

The most commonly reported adverse events were lumbar spinal stenosis (LSS, 7.2% of patients overall; 7.3% of patients in the target cohort and 7.1% patients in the safety cohort) and arthralgia (5.8% of patients overall; 7.3% of patients in the target cohort and no patients in the safety cohort).

Effect Findings The treatment success rate was 45.5% (25/55) for the target cohort and 42.9% (6/14) for the safety cohort.

Patients in the target cohort showed statistically significant improvements in the domains of bodily pain, general health, physical component, physical functioning, role-emotional, role physical, social functioning, and vitality scores as measured by the SF-36 at 5 years post- implantation. Patients in the safety cohort showed statistically significant improvements from baseline in the domains of bodily pain, physical component, physical functioning, role physical, and vitality scores.

Strengths & Weaknesses Strengths of the study include the duration of follow-up and the conduct of radiographic examinations.

Study weaknesses include the retrospective coding of adverse events and limited sample size,

Label Changes Yes, labeling change is recommended to provide long-term, five year data regarding device safety and effectiveness, including clinical results and radiographic findings.

LTOS Study Schedule

Report Schedule
Date Due
FDA Receipt
Applicant's Reporting Status
18 month report 05/21/2007 05/21/2007 On Time
2 year report 11/21/2007 11/21/2007 On Time
18 month interim report 05/21/2008 05/21/2008 On Time
3 year report 11/21/2008 11/20/2008 On Time
4 year report 11/21/2009 11/18/2009 On Time
5 year report 11/21/2010 11/18/2010 On Time
6 year report - FINAL REPORT 11/25/2011 11/23/2011 On Time

Contact Us

Julie Unger
Project Manager, Post-Approval Studies Program
Food and Drug Administration
10903 New Hampshire Ave
WO66-4206v Silver Spring, MD

Phone: (301) 796-6134
Fax: (301) 847-8140

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