Non-inferiority of Osseous Decompression of the Lumbar Canal Until Normalization of Epidural Pressure Compared to Conventional Open Laminectomy in Patients With Symptomatic Lumbar Spinal Stenosis.
Phase: NA
Conditions: Lumbar Canal Stenosis, Lumbar Spinal Stenosis, Lumbar Spinal Stenosis (LSS)
Sponsor: Universidad Complutense de Madrid

Is it really necessary going all over the top in patients with 
symptomatic lumbar canal stenosis? 
 
 
 
 
 
 
 
 
 
Non-inferiority of osseous decompression of the lumbar canal until 
normalization of epidural pressure compared to conventional open 
laminectomy in patients with symptomatic lumbar canal stenosis. 
 
 
 
 
 
 
 
 
 
24/605-EC-X_Tesis 
 
 
 
 
 
 
 
 
June 2, 2025 
 
 
 
 
 
 
 
Juan Pablo Castaño Montoya 
Universidad Complutense de Madrid 
+34-669345474 
juanpablo.castano@salud.madrid.org 

 
2
1. Terminology 
 
• Pressure-guided laminectomy (PGL): Bone resection of the lamina and 
ligamentum flavum until epidural pressure reaches a normal value in the 
stenotic segment. 
• Non–pressure-guided laminectomy (NPGL): Complete resection of 
both the lamina and ligamentum flavum in the stenotic segment. 
 
2. Introduction 
 
Lumbar spinal canal stenosis is a prevalent and disabling cause of low back and 
lower limb pain in the elderly, and it is estimated to affect over 103 million people 
worldwide. (1) It significantly impairs patients’ quality of life due to the presence 
of pain and gait disturbances, impacting social functioning and contributing to the 
development of psychological disorders. (2) Three main hypotheses have been 
proposed to explain the phenomenon of neurogenic claudication: the postural 
theory, the ischemic theory, and the venous stasis theory. However, the precise 
mechanism by which nerve root compression causes the typical clinical 
presentation of lumbar stenosis remains incompletely understood. (3) 
 
A wide range of therapeutic options exists for the management of lumbar spinal 
stenosis, from conservative treatments such as physical therapy and 
neuromodulators to percutaneous procedures like epidural injections, and finally 
surgical approaches ranging from decompression to spinal fusion (1,4). Current 
surgical techniques focus on decompressing the dural sac to address a 
mechanical compression problem. These procedures can be performed through 
open surgery or minimally invasive methods using endoscopic or tubular 
approaches. 
 
A study conducted at this hospital by Carrascosa et al., with results published in 
2020 and 2023, found that in patients who underwent canal decompression via 
laminectomy with radiologic confirmation of the dural sac decompression area, 
clinical improvement was not associated with the postoperative area of the spinal 
canal or thecal sac (5,6). Similar findings have been reported in other studies, 
emphasizing the poor clinicoradiological correlation in this condition, which 
suggests that the pathogenesis of lumbar spinal stenosis may not be solely 
mechanical, and that additional contributing factors may be involved (7–9). 
  
Our research group has developed an interest in identifying these additional 
factors and has proposed a new theory to explain neurogenic claudication. We 
hypothesize that epidural pressure is elevated in stenotic segments compared to 
healthy ones and plays a role in the disease’s pathophysiology, either by 
impairing cerebrospinal fluid (CSF) flow or by causing local ischemia of the cauda 
equina nerve roots. This is supported by evidence of increased epidural pressure 

 
3
in patients with spinal stenosis compared to healthy controls, as well as the 
observation of dynamic epidural pressure changes in patients with neurogenic 
claudication (10–12). 
 
This theory supports the use of minimally invasive procedures, which aim to 
decompress the canal through small access corridors without requiring open 
surgery, extensive dissection of the lumbar musculature, or resection of bone and 
ligamentous structures. In this way, it is possible to minimize the risk of secondary 
spinal instability by performing decompression through a unilateral approach 
while preserving midline structures such as the supraspinous and interspinous 
ligaments and the paravertebral musculature (13–16). 
 
Based on the aforementioned rationale, this study aims to evaluate the non-
inferiority of pressure-guided lumbar canal decompression—until epidural 
pressure normalizes in the stenotic segment—compared to conventional open 
laminectomy without pressure guidance. Both groups will be assessed using 
clinical scales and radiologic imaging to determine clinical improvement. We 
hope that the results of this study will support the theory of lumbar epidural 
hypertension as a potential etiological factor in neurogenic claudication. 
 
3. Hypothesis 
 
The null hypothesis is that non-inferiority of pressure-guided laminectomy 
compared to non–pressure-guided laminectomy cannot be demonstrated in 
patients diagnosed with symptomatic lumbar spinal stenosis. 
 
The alternative hypothesis is that osseous decompression of the lumbar canal 
until epidural pressure normalization is not inferior to conventional open 
laminectomy in achieving clinical improvement in patients with symptomatic 
lumbar spinal stenosis, as measured by the Zurich Claudication Questionnaire 
(ZCQ). 
 
4. Objectives 
 
4.1. General objective 
 
To assess whether osseous decompression of the lumbar canal until 
normalization of epidural pressure is not inferior to conventional open 
laminectomy in achieving clinical improvement in patients with symptomatic 
lumbar spinal stenosis, as measured by the clinical severity subscale of the 
Zurich Claudication Questionnaire (ZCQ). 
 
4.2. Specific objetives 
 

 
4
• To characterize the demographic variables of patients undergoing surgical 
treatment for lumbar spinal stenosis. 
• To compare the clinical response of patients treated using the two different 
surgical techniques.  
• To determine the extent of osseous decompression performed using 
imaging techniques. 
• To evaluate the complications associated with the surgical procedures.    
 
5. Materials and methods 
 
A single-blind, randomized, controlled non-inferiority clinical trial is proposed to 
compare the effectiveness of total osseous decompression of the lumbar canal 
until normalization of epidural pressure versus conventional open laminectomy in 
patients with symptomatic lumbar spinal stenosis. 
 
5.1. Study and reference population 
 
The study will include patients with chronic low back pain and/or lower limb pain 
secondary to lumbar spinal canal stenosis, who are treated at the San Carlos 
Clinical Hospital and attend consultations in the Neurosurgery Department. Given 
the vulnerability of the study population, an a priori sample size calculation will be 
performed to ensure the objectives can be met and a representative sample of 
this patient population can be obtained. 
 
To improve the statistical reliability of the study results, a minimum sample of 24 
subjects has initially been selected. The study will be conducted in the 
Neurosurgery Department at the San Carlos Clinical Hospital in Madrid. 
 
5.2. Inclusion and exclusion criteria 
 
Inclusion criteria: 
• Age over 50 years. 
• Surgical indication determined by: 
o Low back and/or lower limb pain lasting more than 3 months.  
o Pain refractory to conservative medical treatment (analgesics, physical 
therapy, epidural block). 
o Clinical criterion for neurogenic claudication defined as a score ≥11 on 
the N-CLASS scale (Annex 1). (17) 
o Preoperative MRI confirming spinal canal stenosis. (18) 
• Patient agrees to undergo the proposed surgical intervention.  
• Patient consents to participate in the study by signing the informed consent 
form. 
 

 
5
Exclusion criteria: 
• Foraminal or lateral recess stenosis. 
• Symptomatic disc herniation at the surgical level. 
• Spondylolisthesis greater than Meyerding Grade I (vertebral displacement 
>25%) or spondylolysis. 
• Radiological instability defined as sagittal plane displacement >5 mm on 
dynamic flexion-extension spinal X-rays. 
• Scoliosis with a Cobb angle >30º. 
• Compression fracture at the target surgical level. 
• Previous surgery at the same level to be treated. 
• Prior infection at the target level. 
• Contraindication for magnetic resonance imaging. 
• Diagnosis of major depression or dysthymia according to DSM-V criteria. 
(19) 
 
5.3. Withdrawal criteria 
 
• The patient requests to withdraw from the study. 
• Inability to follow the assigned surgical protocol (e.g., intraoperative 
necessity to convert to a different surgical technique due to unforeseen 
findings). 
• Medical events that contraindicate surgical intervention. 
• Withdrawal of informed consent by the patient. 
 
5.4. Dropouts and management of withdrawals 
 
Patients who choose to withdraw from the study may do so at any time without 
any negative consequences to their medical care. 
 
Data collected up to the point of withdrawal will be used for analytical purposes 
unless the patient explicitly requests otherwise. Confidentiality and current data 
protection regulations will be always respected. 
 
5.5. Study Termination 
 
The study will conclude once follow-up of all enrolled patients has been 
completed and the required sample size for statistical analysis has been 
achieved. 
 
Likewise, the study may be terminated early by decision of the ethics committee 
or the principal investigators if unforeseen risks are identified or if insurmountable 
difficulties in conducting the study arise. 
 

 
6
5.6. Sample size 
 
The sample size was estimated using the TwoSampleMean.NIS function from 
the TrialSize package of the statistical software R v.4.4.0. The expected mean 
difference between the groups in the ZCQ clinical severity subscale is 0.51 with 
a standard deviation of 0.57. With a non-inferiority margin set at 0.75 (minimal 
clinically important difference), a one-sided α of 0.05, and a β of 0.20, we estimate 
that a sample size of 20 patients would demonstrate non-inferiority with a power 
of 80%. Finally, based also on similar previous studies and considering a dropout 
rate of 20%, we decided to assume a total N of 24 patients to justify a sample 
size capable of meeting the general study objectives. (20,21) 
 
6. Experimental design 
 
6.1. Study design and work plan  
 
A single-blind, randomized, controlled non-inferiority clinical trial will be 
conducted to compare the effectiveness of total osseous decompression of the 
lumbar canal until normalization of epidural pressure versus open laminectomy 
in patients with symptomatic lumbar spinal stenosis. 
 
The study will not involve participation from the medical industry, and the 
research protocol will be registered on ClinicalTrials.gov. 
 
The indication for surgical intervention will be made by a single neurosurgeon 
from the San Carlos Clinical Hospital, based on clinical scales and imaging 
studies as outlined in the inclusion criteria. After signing the informed consent 
form (Annex 2) and being included on the surgical waiting list, patients will be 
randomized 1:1 using a simple randomization method implemented through 
SPSS software. Baseline evaluations will include various clinical scales (ZCQ, 
Numeric Pain Rating Scale [NPRS], Oswestry Disability Index [ODI], and 
Japanese Orthopedic Association Back Pain Evaluation Questionnaire 
[JOABPEQ]). The patient will remain blinded to their assigned surgical 
intervention. 
 
Study interventions (Figure 1): 
 
• Non–Pressure-Guided 
Laminectomy 
(NPGL): 
Open laminectomy with total decompression of the posterior elements. 
This is defined as the classical technique, in which, after muscle 
dissection, a Codman microsensor (Integra LifeSciences) will be inserted 
into the epidural space under direct visualization. Careful dissection of the 
ligamentum flavum below the right hemilamina will be performed to obtain 
the patient’s baseline epidural pressure (Figure 2). The sensor will then 

 
7
be removed, and resection of the spinous process, supraspinous and 
interspinous ligaments, hemilaminae, and ligamentum flavum will be 
carried out bilaterally until proper decompression of the thecal sac is 
visualized. 
• Pressure-Guided 
Laminectomy 
(PGL): 
After muscle dissection, the Codman microsensor will be inserted into the 
lower epidural space as described above. The patient’s baseline epidural 
pressure will be recorded, and osseous decompression will begin 
following the “unilateral laminotomy for bilateral decompression” 
technique from the left side, continuing until epidural pressure decreases 
to 10 mmHg—previously established as a median non-pathological value 
(22,23).  
 
 
 
Figura 1. Schematic of the osseous decompression to be performed during 
surgical interventions (adapted figure). (24) 
 

 
8
 
Figura 2. A. Codman Microsensor. B. Codman ICP Express Monitor. C. 
Technique for inserting the pressure catheter into the epidural space at the 
stenotic level. 
 
The CODMAN MICROSENSOR pressure catheter (Integra LifeSciences) is a 
transducer with a micro-strain gauge at its distal end that records pressure 
changes in a medium. At the proximal end, it has an electrical connector that 
must be linked to the ICP-EXPRESS monitor. This sensor model was chosen due 
to its availability in the operating room and its prior use in published scientific 
studies. (11) 
 
All procedures will be performed by a single neurosurgeon from the San Carlos 
Clinical Hospital. Patients will be evaluated two weeks postoperatively, during 
which clinical scales will be applied, and the surgical wound will be assessed. 
Follow-up will continue at 3 and 6 months via telephone, and at 12 months in 
person to reassess clinical outcomes. 
 
Additionally, a follow-up lumbar MRI will be performed 3 months after surgery to 
evaluate the degree of decompression achieved. 
 
6.2. Data collection and information sources 
 

 
9
Sociodemographic data and clinical outcome variables will be collected during 
the preoperative consultation and during follow-up visits at 1, 3, and 6 months, 
as well as at one-year post-surgery. Imaging data will be obtained from the 
patient’s preoperative (baseline) lumbar spine MRI and from a follow-up MRI 
performed three months after the surgical procedure. T2-weighted axial 
sequences will be used to assess the degree of osseous decompression 
achieved. 
 
6.3.  Variables  
 
6.3.1. Outcome variables 
 
• Primary outcome: ZCQ – Symptom Severity Subscale (Annex 4): consists 
of 7 items assessing symptom severity over the past month using a 5-point 
numerical scale, where 5 indicates greater severity. The final score is 
calculated as the mean of all item scores. (28–33) 
• Secondary outcomes:  
o ZCQ – Physical Function Subscale (Annex 4): consists of 5 items 
evaluating functional impairment over the past month on a 4-point 
scale, where 4 indicates greater disability. The mean score of the 
items is used as the result. (28,31,33–35) 
o ZCQ – Patient Satisfaction Subscale (Annex 4): consists of 5 items 
categorized into 4 levels (from very satisfied to very dissatisfied). It 
evaluates overall outcome, pain relief, walking capacity, ability to 
work, perform household or gardening tasks, strength, and balance. 
This subscale will be applied at 6 and 12 months postoperatively. 
(28,31,33) 
o NPRS (Annex 5): The Numeric Pain Rating Scale is an 11-point 
scale in which patients rate their pain from 0 to 10, with 0 (on the 
left) representing “no pain” and 10 (on the right) representing “worst 
imaginable pain.” It will assess both lower limb symptoms (NPRS 
lower limbs) and low back and/or gluteal pain (NPRS back or gluteal 
region). (36,37) 
o ODI (Annex 6): The Oswestry Disability Index assesses pain-
related disability across 10 items; each scored from 0 (normal) to 5 
(severely affected). The final score is calculated as the sum of item 
scores divided by the total possible score and multiplied by 100. 
Disability is classified as: mild (0–20%), moderate (21–40%), 
severe (41–60%), crippled (61–80%), and bed-bound or symptom 
exaggeration (>80%). (30,38–40) 
o JOABPEQ (Annex 7): The Japanese Orthopedic Association Back 
Pain Evaluation Questionnaire includes five domains: pain-related 
disorders, lumbar dysfunction, gait disturbance, impairment of 

 
10
social life, and psychological disorders. Scores range from 0 to 100, 
with higher scores indicating better health status. (2,41) 
o Surgical complications.  
o Reoperation.  
 
6.3.2. Variables of interest 
 
• Sociodemographic: 
o Age.  
o Gender.  
o Marital status.   
o Social risk factor (defined as poor family support or undergoing 
disability benefit procedures) 
 
• Clinical:  
o Duration of symptoms (in months).  
o Pain location (lumbar, lower limbs, or both). 
o Predominant pain type (axial or appendicular). 
o Smoking history. 
o Overweight (BMI > 25).  
o Opioid dosage (expressed in morphine milligram equivalents). (25)  
 
• Imagen: 
o Preoperative MRI:  
▪ Degree of lumbar canal stenosis according to the Schizas 
morphological classification (Annex 3). (26) 
o Postoperative MRI:  
▪ Degree of decompression based on the dural sac cross-
sectional area (DSCA) (Figure 3) (24,27) 
 
 

 
11
Figure 3. Measurement of the dural sac cross-sectional area before (left) 
and after decompressive surgery (right) in patients with lumbar spinal 
stenosis. (9) 
 
6.4. Data management 
 
The database generated by the study will not contain any patient-identifying 
information; patient identity will remain confidential. Study data will be recorded 
in a dissociated manner and linked to a code assigned to each patient, so that 
only the investigator can associate the data with a clinical record. Only the 
investigators and personnel responsible for ensuring data quality and analysis 
will have access to participants’ clinical documentation. 
 
The study will comply with Regulation (EU) 2016/679 of the European Parliament 
and of the Council of 27 April 2016, concerning the protection of natural persons 
with regard to the processing of personal data and the free movement of such 
data, and repealing Directive 95/46/EC (General Data Protection Regulation), as 
well as with the Spanish Organic Law 3/2018 of 5 December on the Protection of 
Personal Data and the Guarantee of Digital Rights (LOPDGDD). 
 
The data controller is the San Carlos Clinical Hospital. Its data protection officer 
is the DPO Committee of the Health Department of the Community of Madrid, 
which will process the data for the purposes indicated in this document. 
 
Personal data, including health information, will be retained for the duration of the 
project and for up to three years after its conclusion. Patients may exercise their 
rights to access and rectify their data, as well as their right to restrict data 
processing and to request a copy of the data or to have it transferred to a third 
party. 
 
6.5. Study populations 
 
6.5.1. Per protocol population (PP): Includes all patients who completed 
all scheduled visits and strictly adhered to the study protocol 
instructions. 
6.5.2. Intention-to-treat population (ITT): Includes all patients who were 
initially assigned to an intervention group, regardless of whether they 
deviated from the protocol. 
 
6.6. Data analysis 
 
The demographic and clinical data of the study will be described using descriptive 
statistical indices. Quantitative variables will be summarized using the mean and 
standard deviation (SD). For quantitative variables that do not follow a normal 

 
12
distribution, the median and interquartile range (IQR) will be reported. Qualitative 
variables will be presented as frequency distributions. 
 
No interim efficacy analysis will be conducted. 
 
The efficacy analysis will be performed using both the Per-Protocol (PP) and 
Intention-To-Treat (ITT) populations. The safety analysis will be performed 
exclusively on the ITT population. Data will be analyzed longitudinally, and the 
primary analysis will focus on differences in effectiveness, measured using the 
ZCQ scale and other clinical outcome measures, between the two surgical 
intervention groups. Interactions between treatment and time will also be 
examined to explore potential temporal variations in the treatment effect. 
 
Non-inferiority analysis will be carried out using linear regression models, 
applying a one-sided significance level (α) of 0.05 and the non-inferiority margins 
detailed in Table 1. (20,21,42–46). Multiple non-inferiority hypotheses (one for 
each clinical scale) will be evaluated. Statistical adjustment for multiplicity will be 
applied to control the overall type I error rate, progressively narrowing the 
allowable error margin to maintain the required global error threshold across all 
comparisons. 
 
Table 1. Non-inferiority margins. 
Outcome 
Expected difference 
Non-inferiority margin 
ZCQ (symptom severity) 
0,7 
0,75 
ZCQ (physical function) 
0,6 
0,6 
NRPS back or gluteal 
2 
1,25 
NRPS lower extremity 
2 
1,5 
ODI 
10 
5 
JOABPEQ 
20 
20 
 
In addition to unadjusted models, all analyses will also be adjusted for potential 
confounding variables such as age, sex, and comorbidities using multiple linear 
regression. 
 
The safety analysis will examine the complications that occur during the study 
period. Their association with the surgical intervention will be analyzed using 
logistic regression models. For these analyses, a two-sided significance level (α) 
of 0.05 will be used. 
 
All results will be presented as point estimates with corresponding 95% 
confidence intervals (CIs). These estimates will be compared against the 
predefined non-inferiority margins to determine whether non-inferiority can be 
established. All statistical analyses will be performed using IBM SPSS Statistics 
version 26 and R version 4.4.1. 

 
13
 
6.7. Resources 
 
• Human resources: 
o Neurosurgeon.  
o Neurosurgery Resident Physician. 
o UAMI (Unit for Methodological Support in Research). 
• Facilities: 
o Scheduled surgery operating room. 
o Outpatient consultation room equipped with a chair, desk, 
computer, and examination table. 
o Office with a computer workstation. 
• Specialized Equipment: 
o Intracranial pressure monitoring catheter (Codman). 
o Intracranial pressure monitoring device. 
 
6.8.  Timeline 
 
The estimated duration of the trial is two years, subdivided into a 12-month patient 
recruitment period and one year of follow-up. 
 
 
             2025 
                  2026 
Bioethics committee 
 
  
 
 
 
 
 
 
 
 
Patient recruitment 
 
  
 
 
 
 
 
 
 
 
Follow-up visit (1 month) 
 
  
 
 
 
 
 
 
 
 
Follow-up visit (3 months) 
 
  
 
 
 
 
 
 
 
 
Follow-up visit (6 months) 
 
  
 
 
 
 
 
 
 
 
Follow-up visit (12 months)  
  
 
 
 
 
 
 
 
 
Data analysis 
 
  
 
 
 
 
 
 
 
 
 
6.9. Adverse events 
 
It is the responsibility of the investigator to detect and document any event that 
meets the criteria and definitions of an adverse event (AE). All AEs will be 
reported in accordance with the guidelines set forth in the “CONSORT Statement 
for Randomized Trials of Nonpharmacologic Treatments: A 2017 Update and a 
CONSORT Extension for Nonpharmacologic Trial Abstracts.”” (47) 
 
6.10. 
Ethical considerations 
 
The clinical trial will be conducted in accordance with the principles outlined in 
the Declaration of Helsinki (Annex IV), as well as the current legal regulations in 

 
14
force in Spain. The study will commence only after obtaining approval from the 
relevant Clinical Research Ethics Committee (CEIC). 
 
6.11. 
Dissemination plan 
 
Once the study is completed, the results will be prepared for publication in 
national or international scientific journals and for presentation at conferences. 
The principal investigator commits to complying with current Spanish legislation, 
which mandates the publication of results—whether positive or negative—in 
scientific journals. The publications will acknowledge the Clinical Research Ethics 
Committee (CEIC) that approved the study and disclose the source of funding. 
 
7. References 
 
1. 
Katz JN, Zimmerman ZE, Mass H, Makhni MC. Diagnosis and Management of 
Lumbar Spinal Stenosis: A Review. JAMA. 3 de mayo de 2022;327(17):1688-99.  
2. 
Kobayashi H, Sekiguchi M, Yonemoto K, Kakuma T, Tominaga R, Kato K, 
et al. Reference values of the Japanese Orthopaedic Association Back Pain Evaluation 
Questionnaire in patients with lumbar spinal stenosis and characteristics of  
deterioration of QOL: Lumbar Spinal Stenosis Diagnosis Support Tool: DISTO  project. 
J Orthop Sci. julio de 2019;24(4):584-9.  
3. 
Chad DA. Lumbar spinal stenosis. Neurol Clin. mayo de 2007;25(2):407-18.  
4. 
Chen X, Zheng Z, Lin J. Clinical Effectiveness of Conservative Treatments on 
Lumbar Spinal Stenosis: A Network Meta-Analysis. Front Pharmacol. 2022;13:859296.  
5. 
Carrascosa-Granada A, Velazquez W, Wagner R, Saab Mazzei A, Vargas-
Jimenez A, Jorquera M, et al. Comparative Study Between Uniportal Full-Endoscopic 
Interlaminar and Tubular Approach in the Treatment of Lumbar Spinal Stenosis: A Pilot 
Study. Global Spine J. abril de 2020;10(2 Suppl):70S-78S.  
6. 
Süner HI, Castaño JP, Vargas-Jimenez A, Wagner R, Mazzei AS, Velazquez W, 
et al. Comparison of the Tubular Approach and Uniportal Interlaminar Full-Endoscopic 
Approach in the Treatment of Lumbar Spinal Stenosis: Our 3-Year Results. World 
Neurosurgery. 1 de mayo de 2023;173:e148-55.  
7. 
Boden SD, Davis DO, Dina TS, Patronas NJ, Wiesel SW. Abnormal magnetic-
resonance scans of the lumbar spine in asymptomatic subjects. A prospective 
investigation. J Bone Joint Surg Am. marzo de 1990;72(3):403-8.  
8. 
Gupta S, Bansal T, Kashyap A, Sural S. Correlation between clinical scoring 
systems and quantitative MRI parameters in degenerative lumbar spinal stenosis. J Clin 
Orthop Trauma. diciembre de 2022;35:102050.  
9. 
Hermansen E, Myklebust TÅ, Weber C, Brisby H, Austevoll IM, Hellum C, 
et al. Postoperative Dural Sac Cross-Sectional Area as an Association for Outcome 
After Surgery for Lumbar Spinal Stenosis: Clinical and Radiological Results From the  
NORDSTEN-Spinal Stenosis Trial. Spine (Phila Pa 1976). 15 de mayo de 
2023;48(10):688-94.  
10. 
Takahashi K, Kagechika K, Takino T, Matsui T, Miyazaki T, Shima I. Changes 
in epidural pressure during walking in patients with lumbar spinal stenosis. Spine (Phila 
Pa 1976). 15 de diciembre de 1995;20(24):2746-9.  
11. 
Barz T, Melloh M, Staub LP, Lord SJ, Lange J, Merk HR. Increased 
intraoperative epidural pressure in lumbar spinal stenosis patients with a positive nerve 

 
15
root sedimentation sign. Eur Spine J. mayo de 2014;23(5):985-90.  
12. 
Takahashi K, Miyazaki T, Takino T, Matsui T, Tomita K. Epidural pressure 
measurements. Relationship between epidural pressure and posture in patients with 
lumbar spinal stenosis. Spine (Phila Pa 1976). 15 de marzo de 1995;20(6):650-3.  
13. 
Boukebir MA, Berlin CD, Navarro-Ramirez R, Heiland T, Schöller K, 
Rawanduzy C, et al. Ten-Step Minimally Invasive Spine Lumbar Decompression and 
Dural Repair Through Tubular Retractors. Oper Neurosurg (Hagerstown). 1 de abril de 
2017;13(2):232-45.  
14. 
Soliman MAR, Ali A. Decompression of lumbar canal stenosis with a bilateral 
interlaminar versus classic laminectomy technique: a prospective randomized study. 
Neurosurg Focus. 1 de mayo de 2019;46(5):E3.  
15. 
Zhang C, Chen L, Li J, Huang D, Zhang W, Lin J. Should Posterior Midline 
Structures Be Preserved in Decompression Surgery for Lumbar Spinal Stenosis?: A 
Systematic Review and Meta-analysis. Clin Spine Surg. 1 de octubre de 
2022;35(8):341-9.  
16. 
Mariconda M, Fava R, Gatto A, Longo C, Milano C. Unilateral laminectomy for 
bilateral decompression of lumbar spinal stenosis: a prospective comparative study with 
conservatively treated patients. J Spinal Disord Tech. febrero de 2002;15(1):39-46.  
17. 
Genevay S, Courvoisier DS, Konstantinou K, Kovacs FM, Marty M, Rainville J, 
et al. Clinical classification criteria for neurogenic claudication caused by lumbar spinal 
stenosis. The N-CLASS criteria. Spine J. junio de 2018;18(6):941-7.  
18. 
Steurer J, Roner S, Gnannt R, Hodler J. Quantitative radiologic criteria for the 
diagnosis of lumbar spinal stenosis: a systematic literature review. BMC Musculoskelet 
Disord. 28 de julio de 2011;12:175.  
19. 
American Psychiatric Association. Diagnostic and Statistical Manual of Mental 
Disorders [Internet]. 5th ed. Washington, DC; 2013. Disponible en: 
http://dx.doi.org/10.1176/appi.books.9780890425596 
20. 
Cleland JA, Whitman JM, Houser JL, Wainner RS, Childs JD. Psychometric 
properties of selected tests in patients with lumbar spinal stenosis. Spine J. octubre de 
2012;12(10):921-31.  
21. 
Fukushima M, Oka H, Oshima Y, Yuzawa Y, Matsudaira K, Tanaka S, et al. 
Evaluation of the Minimum Clinically Important Differences of the Zurich Claudication 
Questionnaire in Patients With Lumbar Spinal Stenosis. Clin Spine Surg. diciembre de 
2020;33(10):E499-503.  
22. 
Spetzger U, Bertalanffy H, Naujokat C, von Keyserlingk DG, Gilsbach JM. 
Unilateral laminotomy for bilateral decompression of lumbar spinal stenosis. Part I: 
Anatomical and surgical considerations. Acta Neurochir (Wien). 1997;139(5):392-6.  
23. 
Jia R, Wang XQ, Zhang Y, Hsueh S. Long-Term Outcomes After Minimally 
Invasive Bilateral or Unilateral Laminotomy for Degenerative Lumbar Spinal Stenosis: 
A Minimum 10-Year Follow-Up Study. World Neurosurg. agosto de 2022;164:e1001-6.  
24. 
Hermansen E, Austevoll IM, Hellum C, Storheim K, Myklebust TÅ, Aaen J, 
et al. Comparable increases in dural sac area after three different posterior 
decompression techniques for lumbar spinal stenosis: radiological results from a  
randomized controlled trial in the NORDSTEN study. Eur Spine J. septiembre de 
2020;29(9):2254-61.  
25. 
Dowell D, Haegerich TM, Chou R. CDC Guideline for Prescribing Opioids for 
Chronic Pain--United States, 2016. JAMA. 19 de abril de 2016;315(15):1624-45.  
26. 
Schizas C, Theumann N, Burn A, Tansey R, Wardlaw D, Smith FW, et al. 
Qualitative grading of severity of lumbar spinal stenosis based on the morphology of the 
dural sac on magnetic resonance images. Spine (Phila Pa 1976). 1 de octubre de 

 
16
2010;35(21):1919-24.  
27. 
Hermansen E, Myklebust TÅ, Austevoll IM, Hellum C, Storheim K, Banitalebi 
H, et al. Dural Sac Cross-sectional area change from preoperatively and up to 2 years 
after decompressive surgery for central lumbar spinal stenosis: investigation of  
operated levels, data from the NORDSTEN study. Eur Spine J. 8 de abril de 2024;  
28. 
Stucki G, Daltroy L, Liang MH, Lipson SJ, Fossel AH, Katz JN. Measurement 
Properties of a Self-Administered Outcome Measure in Lumbar Spinal Stenosis. Spine 
[Internet]. 1996;21(7). Disponible en: 
https://journals.lww.com/spinejournal/fulltext/1996/04010/measurement_properties_of_
a_self_administered.4.aspx 
29. 
Comer CM, Conaghan PG, Tennant A. Internal construct validity of the Swiss 
Spinal Stenosis questionnaire: Rasch analysis of a disease-specific outcome measure for 
lumbar spinal stenosis. Spine (Phila Pa 1976). 1 de noviembre de 2011;36(23):1969-76.  
30. 
Tonosu J, Takeshita K, Hara N, Matsudaira K, Kato S, Masuda K, et al. The 
normative score and the cut-off value of the Oswestry Disability Index (ODI). Eur 
Spine J. agosto de 2012;21(8):1596-602.  
31. 
Hidalgo Ovejero AM, Menéndez García M, Bermejo Fraile B, García Mata S, 
Forcén Alonso T, Mateo Sebastián P. Cross-cultural adaptation of the Zurich 
Claudication Questionnaire.Validation study of the Spanish version. An Sist Sanit 
Navar. abril de 2015;38(1):41-52.  
32. 
Fujimori T, Ikegami D, Sugiura T, Sakaura H. Responsiveness of the Zurich 
Claudication Questionnaire, the Oswestry Disability Index, the Japanese Orthopaedic 
Association Back Pain Evaluation Questionnaire,  the 8-Item Short Form Health 
Survey, and the Euroqol 5 dimensions 5 level in the  assessment of patients with lumbar 
spinal stenosis. Eur Spine J. junio de 2022;31(6):1399-412.  
33. 
Wertli MM, Rossi D, Burgstaller JM, Held U, Ulrich NH, Farshad M, et al. 
Validity of outcome measures used in randomized clinical trials and observational 
studies in degenerative lumbar spinal stenosis. Sci Rep. 19 de enero de 
2023;13(1):1068.  
34. 
Tomkins CC, Battié MC, Hu R. Construct validity of the physical function scale 
of the Swiss Spinal Stenosis Questionnaire for the measurement of walking capacity. 
Spine (Phila Pa 1976). 1 de agosto de 2007;32(17):1896-901.  
35. 
Araki M, Nonoshita H, Kitano S, Shigematsu H, Tanaka M, Kawasaki S, et al. 
The critical cutoff point of the Zurich Claudication Questionnaire and the Japanese 
Orthopaedic Association score indicating locomotive syndrome in patients  with lumbar 
spinal canal stenosis. J Orthop Sci. marzo de 2021;26(2):290-4.  
36. 
Childs JD, Piva SR, Fritz JM. Responsiveness of the numeric pain rating scale in 
patients with low back pain. Spine (Phila Pa 1976). 1 de junio de 2005;30(11):1331-4.  
37. 
Chiarotto A, Maxwell LJ, Ostelo RW, Boers M, Tugwell P, Terwee CB. 
Measurement Properties of Visual Analogue Scale, Numeric Rating Scale, and Pain 
Severity Subscale of the Brief Pain Inventory in Patients With Low Back Pain: A  
Systematic Review. J Pain. marzo de 2019;20(3):245-63.  
38. 
Fairbank JC, Pynsent PB. The Oswestry Disability Index. Spine (Phila Pa 1976). 
15 de noviembre de 2000;25(22):2940-52; discussion 2952.  
39. 
Pratt RK, Fairbank JCT, Virr A. The reliability of the Shuttle Walking Test, the 
Swiss Spinal Stenosis Questionnaire, the Oxford Spinal Stenosis Score, and the 
Oswestry Disability  Index in the assessment of patients with lumbar spinal stenosis. 
Spine (Phila Pa 1976). 1 de enero de 2002;27(1):84-91.  
40. 
Vishwanathan K, Braithwaite I. Construct validity and responsiveness of 
commonly used patient reported outcome instruments in decompression for lumbar 

 
17
spinal stenosis. J Clin Orthop Trauma. mayo de 2021;16:125-31.  
41. 
Fukui M, Chiba K, Kawakami M, Kikuchi S ichi, Konno S ichi, Miyamoto M, 
et al. Japanese Orthopaedic Association Back Pain Evaluation Questionnaire. Part 3. 
Validity study and establishment of the measurement scale : Subcommittee on Low  
Back Pain and Cervical Myelopathy Evaluation of the Clinical Outcome Committee of  
the Japanese Orthopaedic Association, Japan. J Orthop Sci. mayo de 2008;13(3):173-9.  
42. 
Ostelo RWJG, Deyo RA, Stratford P, Waddell G, Croft P, Von Korff M, et al. 
Interpreting change scores for pain and functional status in low back pain: towards 
international consensus regarding minimal important change. Spine (Phila Pa 1976). 1 
de enero de 2008;33(1):90-4.  
43. 
Haase I, Kladny B. Clinical Relevance of Changes in Pain Intensity in Patients 
with Specific Back Pain. Z Orthop Unfall. abril de 2022;160(2):213-21.  
44. 
Ogura Y, Ogura K, Kobayashi Y, Kitagawa T, Yonezawa Y, Takahashi Y, et al. 
Minimally clinically important differences for the Japanese Orthopaedic Association 
Back Pain Evaluation Questionnaire (JOABPEQ) following decompression  surgery for 
lumbar spinal stenosis. J Clin Neurosci. noviembre de 2019;69:93-6.  
45. 
Fujimori T, Miwa T, Oda T. Responsiveness of the Japanese Orthopaedic 
Association Back Pain Evaluation Questionnaire in lumbar surgery and its threshold for 
indicating clinically  important differences. Spine J. enero de 2019;19(1):95-103.  
46. 
Takenaka H, Kamiya M, Sugiura H, Nishihama K, Suzuki J, Hanamura S. 
Recovery of the Japanese orthopedic association back pain evaluation questionnaire 
score and walking ability following lumbar spinal stenosis surgery. Eur Spine J. 7 de 
abril de 2024;  
47. 
Boutron I, Altman DG, Moher D, Schulz KF, Ravaud P. CONSORT Statement 
for Randomized Trials of Nonpharmacologic Treatments: A 2017 Update and a 
CONSORT Extension for Nonpharmacologic Trial Abstracts. Ann Intern Med. 4 de 
julio de 2017;167(1):40-7.  
 

 
18
Annex 1. N-CLASS criteria.  
 
 
 
 

 
19
Annex 2. Informed consent.  
 
INFORMED CONSENT FOR LAMINECTOMY AND EPIDURAL PRESSURE 
RECORDING 
 
PARTICIPATION IN THE STUDY 
 
You are invited to participate in the study titled: “Non-inferiority of osseous 
decompression of the lumbar canal until normalization of epidural pressure compared to 
conventional open laminectomy in patients with symptomatic lumbar canal stenosis.” 
You have the right to be informed about the procedures to which you will be subjected 
and the potential complications that may arise. This document aims to explain all these 
issues. Please read it carefully and consult your Neurosurgeon with any questions that 
may arise. 
 
We remind you that, for legal reasons, you or your legal representative, if applicable 
(family member or person with close personal ties), must sign the Informed Consent in 
order for the surgical procedure to be carried out. 
 
It is important to understand that participation in this study is voluntary. Once you give 
your consent to be included in the study, you may withdraw it at any time without this 
affecting your medical care. 
 
Lumbar canal stenosis is a prevalent and disabling cause of lower back and leg pain and 
is associated with a significant decline in patients' quality of life due to pain and gait 
impairment. It is defined as narrowing of the spinal canal in the lumbar area, which 
compresses the spinal nerves traveling to the legs. The diagnosis is established by the 
presence of characteristic symptoms and confirmed through imaging studies (MRI). 
 
Although multiple theories attempt to explain the effects caused by this disease, the 
exact mechanism remains unknown. Through this study, our group aims to evaluate the 
epidural pressure theory by comparing a surgical intervention involving less bone 
removal to the conventional surgery, with the goal of preventing future mechanical 
instability of the lumbar spine. 
 
Both surgical procedures are performed under general anesthesia. Access to the 
affected level will be via a posterior approach to the spine. The procedure involves bone 
resection at the back of the vertebra to remove excess bone and ligaments and ensure 
decompression of the dural sac, the structure that covers the lumbar nerves. 
By agreeing to participate in the study, you consent to the use of personal clinical and 
radiological data for analysis, always maintaining the confidentiality of personal data 
(Annex: confidentiality and data protection). 
 
 
 
 

 
20
DESCRIPTION OF STUDY PROCEDURES 
 
By agreeing to participate in this study, you acknowledge that you will be randomized to 
receive one of the following procedures: 
 
• 
Open Laminectomy: This consists of the removal of the bony structures of the 
vertebrae known as spinous processes and laminae, along with the supraspinous 
and interspinous ligaments and the ligamentum flavum located between the 
laminae and the membrane covering the nerve roots (dura mater), to decompress 
the neural structures. 
• 
Unilateral Laminotomy for Bilateral Open Decompression: This involves the 
resection of the vertebral laminae and ligamentum flavum located between them 
and the dura mater, with the aim of decompressing the neural structures. The 
bone resection will be performed from one side only, intending to remove the 
necessary bone to normalize the pressure on the neural structures. The following 
structures will be preserved: spinous process, supraspinous and interspinous 
ligaments, to minimize postoperative segmental instability. 
 
Additionally, the study includes the measurement of epidural pressure at the affected 
level causing symptoms, before performing the laminectomy and both before and during 
the laminotomy. This will be done by inserting a pressure microsensor between the 
ligamentum flavum and the dura mater once the vertebral level has been identified during 
surgery. The sensor will be removed after pressure measurement in the laminectomy 
and after completing bone decompression in the laminotomy. These steps do not carry 
significant surgical risk. During the study, you will not know whether bone resection was 
guided by pressure measurement and may find out once follow-up is complete or if you 
choose to withdraw from the study. 
 
PREOPERATIVE 
 
Before surgery, you will need to undergo blood tests, a chest X-ray, and an ECG. You 
will also have a pre-anesthesia assessment and receive preoperative instructions 
(fasting hours, medication adjustments, etc.). 
 
POSSIBLE RISKS, DISCOMFORTS, AND CONSEQUENCES 
 
After surgery, you may experience pain at the incision site that may last several weeks. 
You should know that lumbar stenosis is a degenerative spinal process strongly 
associated with aging, and that surgery will decompress the lumbar nerves but will not 
restore the spine to its prior condition. Pain relief is expected, but complete resolution is 
not guaranteed. 
 
After recovering from anesthesia, the patient will be admitted to the general neurosurgery 
ward or intensive care unit if required. You will then gradually resume walking with 
assistance. If there are no complications, discharge will occur within 1 to 3 days. You will 
return after two weeks for wound care follow-up and suture removal if appropriate. 
 
POSSIBLE COMPLICATIONS 

 
21
 
You should know that every surgical procedure carries potential complications due to the 
technique itself and individual factors (diabetes, heart disease, hypertension, anemia, 
obesity, etc.). These may require additional medical or surgical treatment and, in rare 
cases, can result in death. 
 
Main complications include: 
 
1. Spinal cord or nerve root injury: May cause paralysis, sensory deficits, or loss of 
bladder/bowel control, which may be temporary or permanent. 
2. Dura mater injury or rupture: Can occur during surgery or epidural pressure 
catheter insertion. Even with intraoperative repair, a cerebrospinal fluid leak may 
develop, requiring bed rest for 5 days or a new surgical procedure. 
3. Venous thrombosis in the lower limbs: May lead to leg swelling and, rarely, 
pulmonary embolism, which can be fatal. 
4. Bleeding: May be superficial or deep and occasionally require surgical 
evacuation. 
5. Surgical wound infection: May be superficial or deep and may require 
reoperation. Can also lead to cerebrospinal fluid infection (meningitis), requiring 
long-term antibiotics. 
 
 
ALTERNATIVE TREATMENTS 
 
Alternatives include conventional open laminectomy or continuation of medical 
treatment: analgesics, anti-inflammatories, lumbosacral orthosis, epidural injections, and 
rehabilitation. 
 
BENEFITS 
 
It is possible that none of the surgical interventions will improve symptoms. When 
improvement occurs, it usually lasts up to 4 years post-surgery. The new surgical 
technique aims to achieve similar clinical improvement with less bone resection, 
potentially reducing future spinal instability. Your participation will also provide data that 
may benefit other patients in the future. 
 
PATIENT’S DECLARATION 
 
After receiving this information, the patient or legal representative HEREBY 
DECLARES: 
 
1. Having received clear and precise information from the physician about the 
personalized risks and alternatives. 
2. Being satisfied with the information and having all doubts clarified by the 
physician. 
3. Giving consent to undergo the surgical procedure and participate in the study, 
allow the recording of described variables, and analysis of obtained results 
under proper data protection. 

 
22
4. Understanding the right to revoke consent at any time without reason and 
without affecting medical care. 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Signed in Madrid, on the ____ day of 
________________________20_____ 
 
 
Patient or Legal Representative 
Signed in Madrid, on the ____ day of 
________________________20_____ 
 
 
Physician 
 

 
23
REVOCATION OF CONSENT 
 
 
The 
undersigned 
patient 
hereby 
revokes 
the 
consent 
given 
to 
Dr. 
__________________________________________ 
for 
the 
proposed 
surgical 
treatment and inclusion in the clinical research study. 
 
This revocation does not result in any prejudice to your medical care. 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Signed in Madrid, on the ____ day of 
________________________20_____ 
 
 
Patient or Legal Representative 
Signed in Madrid, on the ____ day of 
________________________20_____ 
 
 
Physician 
 

 
24
CONFIDENTIALITY AND DATA PROTECTION 
 
All data collected about you and your health during the study will only be used for this 
purpose. Any future related studies will require prior approval by a Research Ethics 
Committee. 
 
Your data will be treated with strict confidentiality: your name and personal health 
information will be replaced with a code. Only the principal investigator will have access 
to the code. Access to the study data (including health information) will be limited to 
the research team, study monitor, ethics committee members, and competent health 
authorities to ensure compliance with laws and regulations. 
 
The data controller is Hospital Clínico San Carlos (“HCSC”), which will take all necessary 
security measures. Your data will be retained until the end of the study and for 25 years 
thereafter. 
 
According to Organic Law 3/2018 on the Protection of Personal Data and Digital Rights, 
you may exercise your rights to access, rectify, oppose, or delete your data. You may 
also restrict processing of incorrect data, request a copy, or request data portability, if 
applicable. To exercise these rights, contact the principal investigator (NAME, CENTER, 
TELEPHONE). You may also contact the Data Protection Agency if dissatisfied. More 
information: https://www.aepd.es/guias/guia-ciudadano.pdf 
 
HCSC Data Protection Officer Contact: 
Secretary 
of 
the 
Data 
Protection 
Delegate 
Committee   
Calle 
Melchor 
Fernández 
Almagro, 
1, 
28029 
Madrid   
Email: protecciondedatos.sanidad@madrid.org 
 
 
 
 
 
 

 
25
Annex 3. Morphological Classification (Schizas) of Lumbar Spinal 
Stenosis Based on MRI. 
 
 

 
26
Annex 4. Zurich Claudication Questionnaire (ZCQ) (Spanish adapted 
version). 
 
 
 
 

 
27
Annex 5. Numeric Pain Rating Scale (NPRS). 
 
 

 
28
Annex 6. Owestry Disability Index (ODI). 
 
 
 
 

 
29
Annex 7. Japanese Orthopedic Association Back Pain Evaluation 
Questionnaire (JOABPEQ).
 
With regard to your health condition during the last week, please circle the one 
item number of the answer for the following questions that best applies. If your 
condition varies depending on the day or the time, circle the item number of your 
condition at its worst. 
 
Q1-1 To alleviate low back pain, 
you often change your posture. 
1) Yes 2) No 
Q1-2 Because of the low back 
pain, you lie down more often than 
usual. 
1) Yes 2) No 
Q1-3 Your lower back is almost 
always aching. 
1) Yes 2) No 
Q1-4 Because of the low back 
pain, you cannot sleep well. (If you 
take sleeping pills because of the 
pain, select “No.”) 
1) No 2) Yes 
Q2-1 Because of the low back 
pain, you sometimes ask someone 
to 
help 
you 
when 
you 
do 
something. 
1) Yes 2) No 
Q2-2 Because of the low back 
pain, you refrain from bending 
forward or kneeling down. 
1) Yes 2) No 
Q2-3 Because of the low back 
pain, 
you 
have 
difficulty 
in 
standing up from a chair. 
1) Yes 2) No 
Q2-4 Because of the low back 
pain, turning over in bed is 
difficult. 
1) Yes 2) No 
Q2-5 Because of the low back 
pain, you have difficulty putting on 
socks or stockings. 
1) Yes 2) No 
Q2-6 Do you have difficulty in any 
one of the following motions; 
vending 
forward, 
kneeling 
or 
stooping? 
1) I have great difficulty 3) I have no 
difficulty 
2) I have some difficulty 
Q3-1 Because of the low back 
pain, 
you 
walk 
only 
short 
distances. 
1) Yes 2) No 
Q3-2 Because of the low back 
pain, you stay seated most of the 
day. 
1) Yes 2) No 
Q3-3 Because of the low back 
pain, you go up the stairs more 
slowly than usual. 
1) Yes 2) No 
Q3-4 Do you have difficulty in 
going up the stairs? 
1) I have great difficulty 2) I have 
some difficulty 3) I have no difficulty 
Q3-5 Do you have difficulty in 
walking more than 15 minutes? 
1) I have great difficulty 2) I have 
some difficulty 3) I have no difficulty 
 
 
 
 
 
 
 

 
30
Q4-1 Because of the low back 
pain, you do not do any routine 
housework these days. 
1) No 2) Yes 
Q4-2 Have you been unable to do 
your work or ordinary activities as 
well as you would like? 
1) I have not been able to do them at 
all. 
2) I have been unable to do them 
most of the time. 
3) I have sometimes been unable to 
do them. 
4) I have been able to do them most 
of the time. 
5) I have always been able to do 
them. 
Q4-3 Has your work routine been 
hindered because of the pain? 
1) Greatly 2) Moderately 3) Slightly 
(somewhat) 
4) Little (minimally) 5) Not at all 
Q5-1 Because of the low back 
pain, you get irritated or get angry 
at other persons more often than 
usual. 
1) Yes 2) No 
Q5-2 How is your present health 
condition? 
1) Poor 2) Fair 3) Good 4) Very good 
5) Excellent 
Q5-3 Have you been discouraged 
and depressed? 
1) 
Always 
2) 
Frequently 
3) 
Sometimes 4) Rarely 5) Never 
Q5-4 Do you feel exhausted? 
1) 
Always 
2) 
Frequently 
3) 
Sometimes 4) Rarely 5) Never 
Q5-5 Have you felt happy? 
1) Never 2) Rarely 3) Sometimes 4) 
Almost always 5) Always 
Q5-6 Do you think you are in 
decent health? 
1) Not at all (my health is very poor) 
2) Barely (my health is poor) 
3) Not very much (my health is 
average health) 
4) Fairly (my health is better than 
average) 
5) Yes (I am healthy) 
Q5-7 Do you feel your health will 
get worse? 
1) Very much so 2) A little bit at a time 
3) Sometimes yes and sometimes no 
4) Not very much 5) Not at all 
 
Measurement:  
• Social life function: (‘Q1-2’ × 2 + ‘Q2-4’ × 4 + ‘Q2-5’ × 6 + ‘Q2-6’ × 10 − 22) 
× 100 ÷ 74 
• Mental health: (‘Q1-13’ × 3 + ‘Q2-1’ × 4 + ‘Q2-7’ × 6 + ‘Q2-8’ × 6 + ‘Q2-9’ 
× 3 + ‘Q2-10’ × 3 + ‘Q2-11’ × 3 − 28) × 100 ÷ 103 
• Lumbar function: (‘Q1-4’ × 10 + ‘Q1-5’ × 10 + ‘Q1-6’ × 20 + ‘Q1-8’ × 10 + 
‘Q1-9’ × 30 + ‘Q2-3’ × 20 − 100) × 100 ÷ 120 
• Walking ability: (‘Q1-10’ × 30 + ‘Q1-12’ × 20 + ‘Q1-14’ × 10 + ‘Q2-2’ × 10 
+ ‘Q2-4’ × 30 − 100) × 100 ÷ 140 
• Low back pain: (‘Q1-1’ × 20 + ‘Q1-3’ × 20 + ‘Q1-7’ × 20 + ‘Q1-11’ × 10 − 
70) × 100 ÷ 70