Condition category
Circulatory System
Date applied
Date assigned
Last edited
Prospectively registered
Overall trial status
Recruitment status
No longer recruiting
Publication status
Results overdue

Plain English Summary

Background and study aims
Lumbar spinal stenosis is a common condition of the spine affecting mainly the older population. It causes back pain and pain down the legs and impairs mobility, therefore it has a negative impact on the individual’s quality of life. An operation can help to alleviate some of these symptoms. Laminectomy is the standard operation that is offered however this is quite invasive and not always successful. It also has a considerable risk of complications. A new device called X-stop is an implant that can be inserted in between the bones of the spine to achieve the same effect or similar to a laminectomy. The latter is a relatively minor operation where the risk of complications is less, however, the device itself is very expensive and is not proven to be better than a laminectomy. The aim of the study is to find out which operation results in a better quality of life and which one is more cost-effective.

Who can participate?
Adult patients with lumbar spinal stenosis

What does the study involve?
Patients with Lumbar Spinal Stenosis who are candidates for surgery and who agree to participate in the trial are randomly allocated to either a Laminectomy or X-Stop operation. They are asked to complete questionnaires before and after surgery and are followed up for two years.

What are the possible benefits and risks of participating?
Patients follow normal NHS pathways and as such there are no benefits to participate in the trial. The follow up for the trial is two years however, and normally patients would be discharged before that. Therefore, participants in the trial are likely to get longer follow up than usual. Participation is voluntary and patients may withdraw from the study at any point. Patients who agree to participate are unable to choose which operation they will have. Also they are asked to complete several questionnaires prior to surgery and again at 6, 12 and 24 months post operatively which wouldn’t be required outside the trial.

Where is the study run from?
1. The National Hospital for Neurology and Neurosurgery (UK)
2. St George’s Hospital (UK)
3. Hurstwood Park Neuroscience centre (UK)

When is the study starting and how long is it expected to run for?
April 2008 yo August 2017

Who is funding the study?
Kyphon Europe (Belgium)

Who is the main contact?
Mr David Choi

Trial website

Contact information



Primary contact

Mr David Choi


Contact details

Department of Neurosurgery
National Hospital for Neurology and Neurosurgery
Queen Square
United Kingdom
+44 845 155 5000

Additional identifiers

EudraCT number number

Protocol/serial number


Study information

Scientific title

Cost effectiveness and quality of life after treatment of lumbar spinal stenosis with the X-STOP® Interspinous Process Distraction (IPD) device or laminectomy: a prospective randomised trial


CELAX - Cost Effectiveness of lumbar LAminectomy versus X-STOP®

Study hypothesis

Null hypothesis: There is no difference in cost effectiveness, clinical efficacy, quality of life and safety of the X-STOP® device compared to that of conventional lumbar decompressive surgery.

Ethics approval

Charing Cross Research Ethics Committee, 01/04/2008, ref: 08/H0711/12

Study design

Multicentre prospective randomised controlled trial

Primary study design


Secondary study design

Randomised controlled trial

Trial setting


Trial type


Patient information sheet

Not available in web format, please use the contact details below to request a patient information sheet


Neurogenic intermittent claudication secondary to lumbar spinal stenosis


Participants will be randomly allocated to the one of two treatment groups. A five block randomisation process will be used and patients are randomised the day before surgery.

Lumbar laminectomy: Participants receive a standard surgical decompression where the laminae at the affected level are removed. The operating surgeon’s discretion is used to determine the extent of the decompression including undercutting of the facet joints and whether a drain is required.

X-STOP® interspinous distractor: Patients have the device inserted at the affected level.

Participants in both groups complete follow up questionnaires post-operatively, and after six months and one and two years.

Intervention type



Not Applicable

Drug names

Primary outcome measure

Cost of implanting X-stop interspinous distractor compared to conventional surgical decompression

Secondary outcome measures

The following will be assessed preoperatively, on discharge, at 6 weeks, 6, 12 and 24 months:
1. Quality of life, assessed by the EQ-5D, 36-item Short Form health survey (SF-36) and Quebec Back Pain Disability Questionnaire
2. Clinical efficacy, assessed by the Zucher Claudication Questionnaire (ZCQ), Oswestry Disability Index (ODI) and visual analogue scale (VAS)
3. Safety (any complication either perioperatively or postoperatively)

Overall trial start date


Overall trial end date


Reason abandoned (if study stopped)


Participant inclusion criteria

1. Age: 18-80
2. Sex: males and non-pregnant females
3. Chronic leg pain with or without back pain of greater than 6 months duration, partially or completely relieved by adopting flexed posture and who are suitable candidates for posterior lumbar surgery
4. Those who have completed at least 6 months of conservative treatment without obtaining adequate symptomatic relief
5. Degenerative changes at one or two adjacent levels between L1-S1 confirmed by X-ray, computerised tomography (CT) or magnetic resonance imaging (MRI) scan

Participant type


Age group




Target number of participants

110 (55 in each treatment group)

Participant exclusion criteria

1. Fixed motor deficit
2. Active infection or metastatic disease
3. Degenerative spondylolisthesis >= Meyerding Grade 2
4. Known allergy to implant materials
5. Severe osteoporosis or rheumatoid arthritis
6. Cauda equina syndrome

Recruitment start date


Recruitment end date



Countries of recruitment

United Kingdom

Trial participating centre

The National Hospital for Neurology and Neurosurgery
Queen Square
United Kingdom

Trial participating centre

St George’s Hospital
Blackshaw Road
SW17 0QT
United Kingdom

Trial participating centre

Hurstwood Park Neuroscience centre
Princess Royal Hospital
Hayward’s Heath
RH16 4EX
United Kingdom

Sponsor information


University College London Hospitals NHS Foundation Trust (UK)

Sponsor details

c/o Mr Philip Diamond
Research and Development Department
1st Floor
Maple House
149 Tottenham Court Road
United Kingdom
+44 845 155 5000

Sponsor type




Funder type


Funder name

Kyphon Europe (Belgium)

Alternative name(s)

Funding Body Type

Funding Body Subtype


Results and Publications

Publication and dissemination plan

Planned publication in a per reviewed journal.

IPD Sharing plan:
The datasets generated during and/or analysed during the current study are/will be available upon request from Anouk Bord (

Intention to publish date


Participant level data

Available on request

Basic results (scientific)

Publication list

Publication citations

Additional files

Editorial Notes

18/04/2017: The following changes have been made to the record: 1. The public title, interventions, trial participating centres, publication and dissemination plan and IPD Sharing plan have been added. 2. The overall trial dates have been updated from 01/06/2008 - 01/06/2011 to 01/04/2008 - 01/08/2017 and the recruitment dates have been updated from 01/06/2008 - 01/06/2011 to 11/12/2008 - 01/02/2014. 12/04/2017: No publications found in PubMed, verifying study status with principal investigator