Sacroiliac Joint Fusion Versus Sham Operation for Treatment of Sacroiliac Joint Pain. A Prosepctive Double Blinded Randomized Controlled Multicenter Trial.
Phase: NA
Conditions: Sacroiliac Joint Somatic Dysfunction
Sponsor: Oslo University Hospital

 
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SacroIliac Joint Fusion vs Sham Operation  
for treatment of sacroiliac joint pain 
A prospective double blinded randomized controlled multicenter 
trial 
 
Engelke Randers, MD  
Thomas Johan Kibsgård, MD, PhD  
Oslo University Hospital, Department of Orthopaedics, Oslo, Norway 
Institute of Medicine, University of Oslo, Oslo, Norway 
 
Paul Gerdhem 
Reconstructive Orthopaedics, Karolinska University Hospital, Department of Clinical 
Sciences, Intervention and Technology, Karolinska Institutet, Stockholm, Sweden. 
Department of Orthopaedics and Hand Surgery, Uppsala University Hospital and Department 
of surgical sciences, Uppsala University 
 
Trial registration: The RCT is registered at www.clinicaltrials.gov with identification 
number NCT03507049 
 
Date of revision: 30th June 2022.  
 
 

 
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Table of contents 
INTRODUCTION ................................................................................................................................................. 3 
PATIENTS AND METHODS ............................................................................................................................... 4 
Study design.................................................................................................................................................... 4 
Patients ............................................................................................................................................................ 4 
Table 1: Inclusion and exclusion criteria ................................................................................................ 5 
Interventions................................................................................................................................................... 6 
Cases/Surgery ............................................................................................................................................ 6 
Controls/Sham surgery ............................................................................................................................. 6 
Figure 1: Flow-chart of trial timeline. ..................................................................................................... 7 
Sample size...................................................................................................................................................... 8 
Outcomes ........................................................................................................................................................ 9 
Primary outcome ....................................................................................................................................... 9 
Secondary outcomes .................................................................................................................................. 9 
Table 2: Timeline of outcome measures ................................................................................................ 10 
Study procedures ......................................................................................................................................... 10 
Randomization ......................................................................................................................................... 10 
Blinding .................................................................................................................................................... 11 
Withdrawal .............................................................................................................................................. 11 
Postoperative care ................................................................................................................................... 11 
Data analysis plan ........................................................................................................................................ 12 
Research questions, objectives and hypotheses .................................................................................... 12 
Data collection .......................................................................................................................................... 13 
Data set and variables ............................................................................................................................. 13 
Data analysis ............................................................................................................................................ 15 
Shell tables ................................................................................................................................................ 16 
DISCUSSION ..................................................................................................................................................... 19 
Ethics, registration, funding and potential conflicts of interest ......................................................................... 20 
Aknowledgements ............................................................................................................................................... 21 
References: ......................................................................................................................................................... 21 
 
 
 

 
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INTRODUCTION 
Sacroiliac joint (SIJ) pain is increasingly recognized as a possible pain generator in low back 
pain (LBP) (Sembrano et al. 2009). In as many as 15-30% of patients with LBP, the sacroiliac 
joint may be the cause of pain, and to an even greater extent in patients suffering from “failed 
back surgery” ( Sembrano et al. 2009, DePalma et al. 2011).  
The sacroiliac joint transfers force from the spine through the pelvis to the lower extremities 
(Vleeming et al. 2012). Dysfunction of the joint’s articular congruity, ligamentous structures 
and motor control might be a cause of pain (Aldabe et al. 2012). The joint is richly innervated 
and contains mechano- and nociceptive receptors ( Sakamoto et al. 2001, Szadek et al. 2008). 
Even though pain can arise from the sacroiliac joint, the diagnosis of sacroiliac joint pain is 
challenging. Patient history and radiological imaging have low sensitivity and specificity for 
the diagnosis of sacroiliac joint pain (Elgafy et al. 2001, Vleeming et al. 2008). Single clinical 
tests show little diagnostic strength for sacroiliac joint pain, but composites of clinical tests 
have fair sensitivity and specificity (Laslett et al. 2005, Vleeming et al. 2008). To strengthen 
the diagnosis, clinical tests are combined with intraarticular sacroiliac joint injection with 
local anesthetics (Kennedy et al. 2015).   
Sacroiliac joint pain can be severe, disabling and reduce quality of life similarly to other spine 
conditions (Cher et al. 2014). Non-operative treatment consists of physiotherapy, pain 
medication, intra-articular sacroiliac joint steroid injections, prolotherapy and radiofrequency 
neurotomy of sacral nerve branches. There is limited evidence of effect of these treatment 
modalities (Luukkainen et al. 2002, Cohen et al. 2008, Kim et al. 2010, Patel et al. 2012) . In 
many patients non-operative treatment fails (Polly et al. 2016a).  Historically open surgery has 
often been unsuccessful, due to intense postoperative pain and severe complications (Smith-
Petersen et al. 1926).  Recent multiple minimally-invasive sacroiliac joint fusion studies have 
reported pain relief and improved function to a greater extent than non-operative treatment 
and open surgery, and with low frequency of complications (Ledonio et al. 2014, Polly et al. 
2016a, Sturesson et al. 2016, Whang et al. 2019).  The increase in both available implants for 
minimally invasive sacroiliac joint fusion and their use is demonstrated by a growing number 
of publications. However, many are industry-sponsored and of poor quality (Sachs et al. 2012, 
Sachs et al. 2013, Miller et al. 2014, Rappoport et al. 2017, Fuchs et al. 2018).   
Although the literature suggests superiority of minimally invasive sacroiliac joint fusion to 
non-operative treatment, some of the effect may be explained by placebo; to what extent is 

 
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not known. Therefore, we designed a non-industry sponsored prospective multi-center, 
double-blind, randomized sham-surgery controlled trial (RCT) in accordance with the SPIRIT 
recommendations to test the null-hypothesis that there is no difference in pain reduction 
between sham surgery and minimally invasive sacroiliac joint fusion.  
 
PATIENTS AND METHODS  
Study design 
The trial is designed as a prospective multi-center, double-blinded, randomized sham-surgery 
controlled trial with 2 parallel groups. Participants, investigators, and data analysists are 
blinded for group allocation until the primary endpoint. The primary end-point is group 
difference in sacroiliac joint pain intensity on the operated side at 6 months postoperatively, 
measured by Numeric Rating Scale (NRS).  
60 participants will be included after oral and written study information is given, and with 
written consent from the participant. There are 2 recruitment sites; Oslo University Hospital 
(OUS) in Norway and Karolinska University Hospital in Sweden. The recruitment phase 
started in April 2018, and the 1st participant was recruited in August 2018 in Norway and 
December 2019 in Sweden. Due to the corona virus pandemic there were large delays in 
inclusion in both countries. Inclusion was completed October 2021.  All patients are followed 
for 6 months before unblinding, and for a total of 2 years postoperatively. The studies primary 
endpoint, the 6 month follow-up was finished by May 2022. 
 
Patients 
Referrals from general practitioners and from departments of orthopedic surgery or physical 
medicine and rehabilitation are screened for eligibility by an orthopedic consultant in the 2 
departments and all patients whose referral includes information about pain originating from 
the sacroiliac joint are taken in for evaluation. This baseline evaluation is performed at the 
hospital’s outpatient clinics with standardized clinical examination in accordance with 
inclusion and exclusion criteria (Table 1). Those who fulfill the inclusion criteria are invited 
to participate in the RCT. 
 
 

 
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Table 1: Inclusion and exclusion criteria 
 
The orthopedic department at Oslo University Hospital is currently the only center in Norway 
that performs minimally invasive sacroiliac joint. Approximately 40-60 patients are evaluated 
per year in the outpatient clinic. Sweden has evaluated twice the number of patients annually, 
and minimally invasive sacroiliac joint fusion is performed at 2 centers. One of the centers in 
Sweden participate in the study.   
 
 
 
INCLUSION CRITERIA 
1. 
Suspected SIJ pain for >6 months, or >18 months for pregnancy induced pelvic girdle pain. 
2. 
Between 21-70 years old 
3. 
Diagnosis of the SIJ as the suspected primary pain generator based on both of the following: 
A. 
Pain pointed with a single finger (Fortin Finger Test) at or close to the posterior superior iliac spine (PSIS) with possible radiation into 
buttocks, posterior thigh or groin  
B. 
At least 3 of 6 clinical tests for SIJ pain (Laslett et al. 2005; Vleeming et al. 2008) 
1. 
Compression  
2. 
Posterior Pelvic Pain Provocation test – P4  
3. 
Palpation of the long dorsal sacroiliac ligament 
4. 
Patrick FABER’s test  
5. 
Active Straight Leg Raise (ASLR) test 
6. 
Gaenslen´s test 
4. 
Reduced SIJ pain (NRS) of at least 50% of the pre injection NRS score after fluoroscopically or computed tomography guided controlled injection of 
local anesthetic into the SIJ.  
5. 
Oswestry Disability Index (ODI) score of at least 30%. 
6. 
SIJ pain of at least 5 on the Numeric Rating Scale (NRS), where 0 is no pain at all and 10 is worst imaginable pain.  
7. 
Bilateral SIJ pain, if one dominant side. If eligible the dominant painful SIJ will be treated in the study. 
8. 
Mentally and physically able to comply with study protocol. 
9. 
Signed study-specific informed consent.  
EXCLUSION CRITERIA 
1. 
Pain due to other causes, such as lumbar disc degeneration, lumbar disc herniation, lumbar spondylolisthesis, lumbar spinal stenosis, lumbar facet 
degeneration, and lumbar vertebral body fracture. 
2. 
Sacroiliac pathology caused by auto-immune disease (e.g. ankylosing spondylitis), neoplasia or crystal arthropathy. 
3. 
History of recent (<1 year) fracture of the pelvis with documented malunion, non-union of sacrum or ilium or any type of internal fixation of the pelvic 
ring. 
4. 
Spine surgery during the past 12 months. 
5. 
Previously diagnosed or suspected osteoporosis (defined as T-score <-2.5 or history of osteoporotic fracture). 
6. 
Documented osteomalacia or other metabolic bone disease. 
7. 
Any condition or anatomy that makes treatment with the iFuse Implant System infeasible. 
8. 
Patients with prior SIJ surgery. 

 
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Interventions 
Patients are randomized to either receive minimally invasive sacroiliac joint fusion or a sham 
procedure (Figure 1). All patients will receive the same pre- and postoperative assessment 
(i.e. blood samples, general anesthesia, draping, wound care and pain medication). They will 
not be randomized before they are under general anesthesia. Patients are kept under general 
anesthesia for 40 to 50 minutes regardless of intervention group as this operation on average 
lasts for 45 minutes. The operations will be done by 1 or 2 surgeons and the theater will be 
closed to all other personnel. After the procedure is completed the participants will be treated 
with standard post-operative care as given after minimally invasive sacroiliac joint fusion 
regardless of randomization group. The post-operative follow-up during the hospital stay will 
be done by health staff blinded for treatment allocation.   
Cases/Surgery 
Patients randomized to sacroiliac joint fusion receive treatment with triangular titanium 
implants according to the surgical technique manual (iFuse, SI BONE, Inc. ) (SI BONE 
2020).  The procedure starts with a 3-5cm long skin incision over the posterolateral aspect of 
the pelvis.  Blunt dissection is performed through the subcutaneous tissue, fascia and muscle. 
Guide pins are inserted over the SIJ at the desired entry-point, verified by fluoroscopy. The 
surgeon drills and broaches over the pins, and 3 triangular titanium implants are inserted. The 
wound is then closed. An injection of the sacroiliac joint with local anaesthetic is performed 
under guidance of fluoroscopy at the time of the procedure. A subcutaneous injection of local 
anaesthetic is given around the skin incision.  
 Controls/Sham surgery 
The control group consists of participants randomized to sham operation. The sham operation 
consists of the surgeon making the same skin incision as the surgical group receives. Blunt 
dissection is performed through the subcutaneous tissue, fascia and muscle. Guide pins are  
 
 

 
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Figure 1: Flow-chart of trial timeline.   
 

 
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inserted to the ileum, but do not enter the bone. The wound is then closed. Participants will be 
under general anesthesia while the procedure is simulated. All instruments needed are 
smeared with blood from the skin incision in order to keep the 2 procedures as similar as 
possible. An injection of the sacroiliac joint with local anaesthetic is performed under 
guidance of fluoroscopy during the procedure. A subcutaneous injection of local anaesthetic is 
given around the skin incision.  
The surgeon will use a standard phrasing for the surgical report for both cases and controls. 
For controls pre-operative planned implants are reported and for intervention cases the actual 
implants used are reported. 
Initially 2 methods of sham intervention (Norway vs Sweden) were described in the protocol 
section on ClinicalTrials.gov. The reason for this was due to different criteria for obtaining 
ethical approval in the 2 countries. However, after observing the 2 different sham intervention 
methods the study group concluded that the differences where insignificant and therefore 
could be described similarly.  
 
Sample size 
The average mean pre-operative NRS in previous studies has been reported to be 7.0-8.5 
( Kibsgard et al. 2013, Sachs et al. 2013, Duhon et al. 2016, Polly et al. 2016b). There are 2 
RCT´s that have compared minimally invasive sacroiliac joint fusion to non-operative 
treatment (Polly et al. 2016a; Sturesson et al. 2016). These report a mean decrease in global 
NRS of respectively 4.3 and 5.3 (Polly et al. 2016a; Sturesson et al. 2016). The same 2 studies 
showed a mean 0.5-1.3 points decrease in NRS in the group treated with non-operative 
treatment. We assume our trial´s case group to have at least mean 3 points decrease in NRS 
and the control group to experience a mean 1 point decrease in NRS.  2 previous studies have 
suggested that 2 points reduction in NRS represents a clinical important difference ( Farrar et 
al. 2001, Hagg et al. 2003). For the sample size calculation, we assumed a change that would 
result in a mean 2 point difference between the groups for the main outcome in NRS on the 
operated side 6 months postoperatively. The standard deviation (SD) was set to 2.5 points 
since the SD has been reported in previous studies to vary between 1.0-2.9 at 6 months 
follow-up after sacroiliac joint fusion ( Kibsgard et al. 2013, Sachs et al. 2013, Polly et al. 
2016b, Duhon et al. 2016). The probability of a type 1 error (alpha) was set to 0.05. Based on 
these assumptions we calculate 25 participants in each group with 80% power using an online 

 
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sample size calculator (http://www.clincalc.com). Due to a possible dropout of 20% we will 
include 30 participants in each group, giving 60 participants in the study.  
 
Outcomes 
Primary outcome 
The primary outcome is group difference in pain intensity on the operated side at 6 months 
postoperatively, measured by NRS, where 0 is no pain at all and 10 is worst imaginable pain. 
NRS is used as a primary outcome in other studies on minimally invasive sacroiliac joint 
fusion and will make it possible to compare our results with existing literature (Polly et al. 
2016a; Sturesson et al. 2016).  
Secondary outcomes 
Secondary outcomes are patient-related-outcome-measures (PROMs), functional tests and 
pain-scores measured with NRS for global pelvic pain, contralateral sacroiliac joint pain and 
leg pain (Table 2). The PROMs collected are Oswestry Disability Index (Copay et al. 2016), 
Pelvic Girdle Questionnaire (Stuge et al. 2011) and the Euroqol 5 dimension (EQ-5D-5L) and 
EQ visual analogue scale (EQ-5D Foundation 2017). The functional tests consist of the active 
straight leg raise test, the 6 minute walking test and Timed Up and Go test. Furthermore, data 
on work status, ambulatory status, adverse events including re-intervention in target sacroiliac 
joint, implant loosening and fractures are recorded. Patient assessment of treatment and 
patient satisfaction with treatment is also collected. All assessments at 3- and 6-months 
follow-up are performed by blinded investigators who are qualified health personnel. After 6 
months patients and investigators are un-blinded. Follow-up is continued for 2 years after the 
operation.  
 
 

 
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Table 2: Timeline of outcome measures 
 
 
Abbreviations and explanations: SIJ = Sacroiliac joint. NRS = Numeric Rating Scale (measured on scale 0-10 where 0 is no pain and 10 is 
worst imaginable pain). ODI = Oswestry Disability Index (scale 0-100, where 0 is normal function,100 is bedridden). PGQ = Pelvic girdle 
questionnaire (score converted to percentage 0-100%, where 0 is worst pelvic health, 100 is best pelvic health).  EQ-5D-5L: describes 
quality of life through scores in 5 dimensions all scored between 1 = no problems to 5= extreme problems. EQ-VAS (scale from 0-100: 
where 0 is worst health and 100 is best health). ASLR = Active Straight Leg Raise test (scale 0-5 where 0 = no difficulty raising leg, 5 = 
severe difficulty. Measured per leg.). ASLR range test = Active Straight Leg Raise Range test (measures how high a straight leg can be 
raised from examination table to the nearest 5 degree). 6MWT = 6 minute walking test (measures the distance in meters walked in 6 minutes 
in one round). TUG = Timed Up and Go (Measures the time it takes a patient to sit in chair, raise, walk 3 meters back and forth and sit back 
in chair. Mean time of two rounds is recorded). 
 
Study procedures 
Randomization 
Participants who give consent to participate in the trial and who fulfill the inclusion criteria 
will be randomized by the operating surgeon at each site (1 per site) after the participant has 
been anesthetized. Participants will be randomly assigned to either minimally invasive 
Endpoint/outcome 
Baseline 
Preoperative 
Postoperative 
3 months 
6 months 
12 
months 
24 
months 
NRS operated SIJ/side 
x 
x 
x 
x 
x 
x 
x 
Global NRS 
x 
x 
x 
x 
x 
x 
x 
NRS non-operated SIJ/side 
x 
x 
x 
x 
x 
x 
x 
Leg pain NRS 
x 
x 
x 
x 
x 
x 
x 
ODI 
x 
x 
 
x 
x 
x 
x 
PGQ 
x 
x 
 
x 
x 
x 
x 
EQ-5D-5L, including EQ-VAS scale 
x 
x 
 
x 
x 
x 
x 
Clinical tests: 
• 
Patrick´s test (FABER) 
• 
Posterior Pelvic Pain Provocation test 
(P4) 
• 
Gaenslens test 
• 
Mennells test  
• 
Distraction 
• 
Compression 
• 
Palpation of the long dorsal ligament 
and sacrotuberal ligament 
x 
x 
 
x 
x 
x 
x 
Functional tests  
• 
ASLR 
• 
ASLR range test 
• 
6MWT  
• 
TUG 
x 
x 
 
x 
x 
x 
x 
Ambulatory and work status 
x 
x 
 
x 
x 
x 
x 
Adverse Events (including device 
breakage, migration, loosening etc) 
 
 
x 
x 
x 
x 
x 
Re-intervention of target SIJ 
 
 
 
x 
x 
x 
x 
Patient satisfaction with treatment 
 
 
 
x 
x 
x 
x 
Patients assessment of treatment 
 
 
 
x 
x 
x 
x 

 
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sacroiliac joint fusion or sham surgery. Randomization is performed as block randomization 
with blocks of 4 or 6 with a 1:1 allocation to minimally invasive sacroiliac joint fusion or 
sham surgery. The randomization sequence is pepared by an independent statistician and the 
randomization sequence was unknown to the researchers.  Allocation is completed with a 
computer generated randomization stratified by site through a specific website (Viedoc 
©Viedoc Technologies (Viedoc 2021) provided by OUS). This website can only be accessed 
with personified username and password, and only the operating surgeon has access to 
randomize participants.  
Blinding 
All other parties than the operating surgeon and assisting staff in the operating theatre are 
blinded as to which intervention the participant has received. This includes trial participants, 
care providers, investigators and data analysts. No other than the operating surgeons have 
access to randomization prior to follow-up. Un-blinding occurs after completed 6-months 
follow-up. Participants that have undergone sham intervention and wish to cross over to 
surgical intervention are allowed to when the 6-month follow-up is completed. Both 
participants who were randomized to minimally invasive sacroiliac joint fusion initially and 
participants who cross-over to minimally invasive sacroiliac joint fusion are then followed for 
at least 2 years postoperatively (Figure 1). Participants who have undergone surgical 
intervention with implants can undergo surgery of the opposite sacroiliac joint if they wish 
after the initial 6-month follow-up. 
Un-blinding of participants may take place if there is a suspicion of a severe adverse event in 
which knowledge of implant positioning is essential for patient management. Example of such 
events can be severe pain, new neurological deficits, or other injuries of such severity that it 
demands radiological examination to ensure adequate emergency medical care.  
Withdrawal 
The participant may withdraw from the study for any reason at any time. The investigators 
may also withdraw participants from the study in order to protect their safety and/or if they 
are unwilling or unable to comply with the required study procedures. 
Postoperative care 
All participants are informed of partial weight bearing on crutches for the first 4-8 weeks 
postoperatively. After 12 weeks there are no restrictions.  

 
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CT scan of the sacroiliac joint is performed pre-operatively and at 6, 12, 24 months follow-up 
to evaluate proper implant placement and lack of radiological signs of loosening.  
 
Data analysis plan 
Research questions, objectives and hypotheses 
Research questions: 
1. What is the efficacy of minimally invasive sacroiliac joint fusion? 
2. Are there any tests, signs, symptoms or patient reported outcomes which can predict 
the outcome of minimally invasive sacroiliac joint fusion? 
Objectives: 
The main objective of this trial is to test the null-hypothesis that there is no difference in pain 
intensity between the sham surgery and minimally invasive sacroiliac joint fusion groups at 
follow-up.  
Secondary objectives are to test the secondary hypotheses listed below and investigate the 
following research questions: 
1. Is there a difference in pain intensity between minimally invasive sacroiliac joint 
fusion and sham at follow-up? 
2. Is there a group difference in reduction in pain intensity from baseline to 3 months to 
6 months between the sacroiliac joint fusion group and the sham group?  
3. Is there a difference in functional outcomes measured with PROMs, clinical tests and 
functional tests between the sacroiliac joint fusion group and the sham group? 
4. Is there a difference in the proportion of individuals that reach a clinically significant 
improvement of 2 points or more on the NRS scale in the sacroiliac joint fusion group 
and the sham group? 
5. Is there a difference in the usage of analgesics at 3 and 6 months in the sacroiliac joint 
fusion group and the sham group? 
6. Is there a difference in the rate of complications at 3 and 6 months in the sacroiliac 
joint fusion group and the sham group? 
7. Is there a difference in the proportion of individuals that are on full or partial sick 
leave at 3 and 6 months in the sacroiliac joint fusion group and the sham group? 
Hypotheses: 
1. There is no difference between the groups in pain intensity on the operated SIJ in the 
sacroiliac joint fusion group compared to the sham group 
2. Pain improves similarly in the sacroiliac joint fusion group as in the sham group between 
baseline and 3 months.  
3. Pain improves similarly in the sacroiliac joint fusion group as in the sham group between 
3 months and 6 months.  

 
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4. Pain improves similarly in the sacroiliac joint fusion group as in the sham group between 
baseline and 6 months.   
5. There is a similar improvement in physical function, measured with functional tests and 
subjective questionnaires, in the sacroiliac joint fusion group as in the sham group. 
6. The same proportion of individuals in the sacroiliac joint fusion group achieve a 
clinically significant improvement of 2 points or more on the NRS scale as in the sham 
group. 
7. Individuals in the sacroiliac joint fusion group use the same amount of analgesics at 3 
and 6 months as individuals in the sham group.  
8. The proportion of individuals with complications at 3 and 6 months is similar in the 
sacroiliac joint fusion group as in the sham group.  
9. The proportion of individuals that are on full or partial sick leave at 3 and 6 months is 
similar in the sacroiliac joint fusion group as in the sham group  
Data collection 
Baseline data on age, sex, diagnosis of sacroiliac joint pain, level of sacroiliac joint pain and 
response to injection if applicable, is registered on all eligible individuals evaluated at the 
outpatient clinic in order to evaluate reasons for failure to include individuals and for 
exclusion.  
All data from both trial centres is collected into the Viedoc website (©Viedoc Technologies 
(Viedoc 2021)) provided by OUS. The data is confidential and not available as the trial is not 
completed and recruitment is still ongoing.  Data collection is done either by direct electronic 
registration into the Viedoc Database or by forms, subsequently transcribed into Viedoc by 
the investigators. If there are missing data these will be collected by contacting the participant 
or by medical records review. Any adjustment of data entry has to be documented and is 
registered and reported by the database.  
Data set and variables 
The data set is exported from the Viedoc database as an excel-file. Only data from baseline, 
preinjection, postinjection, preoperative, postoperative, 3 months and 6 months time-points 
are used in this data analysis.  
 
 

 
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Variables 
Independent or Predictor variables 
Dependent or outcome variables 
Continuous 
Categorical 
Continuous 
Categorical 
Age (years) 
Sex (F/M) 
Numeric Rating Scale 
(NRS) (0-10 scale): 
- 
Operated SIJ 
- 
Contralateral SIJ 
- 
Leg pain 
- 
Global pelvic pain 
EQ-5D-5L 
 
 
Weight (kg) 
 
Etiology of SIJ 
pain: 
- 
Idiopathic 
- 
Related to 
pregnancy 
- 
Trauma 
Other 
EQ-5D-5L index 
 
 
Height ( cm) 
 
Civil status 
 
 
Clinical tests 
(pos/neg): 
- 
Patrick´s test 
(FABER) 
- 
Posterior Pelvic 
Pain 
Provocation 
test (P4) 
- 
Gaenslens test 
- 
Mennells test 
- 
Distraction test 
- 
Compression 
test 
- 
Palpation of 
Long Dorsal 
Ligament and 
Sacrotuberal 
Ligament.  
Employment 
status 
 
Clinical tests (pos/neg): 
- 
Patrick´s test 
(FABER) 
- 
Posterior Pelvic Pain 
Provocation test (P4) 
- 
Gaenslens test 
- 
Mennells test 
- 
Distraction test 
- 
Compression test 
- 
Palpation of Long 
Dorsal Ligament and 
Sacrotuberal 
Ligament.  

 
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Oswestry 
Disability Index 
(%) 
Comorbidities 
(number of 
previous 
illnesses) 
Oswestry Disability 
Index (%) 
 
Pelvic girdle 
questionnaire (%) 
SIJ pain specific 
questions (Y/N) 
Pelvic girdle 
questionnaire (%) 
Adverse Events (Y/N) 
 
EQ-5D VAS scale 
(0-100) 
 
EQ-5D VAS scale (0-
100) 
Re-intervention of 
operated SIJ (Y/N) 
Children (number  
of children) 
 
 
Patient satisfaction with 
treatment (0-5) 
Timed Up and Go 
(sec) 
6 minute walking 
test (meters) 
 
Timed Up and Go 
(sec) 
6 minute walking test 
(meters) 
Patient assessment of 
treatment (0-5) 
Functional tests: 
- 
ASLR (0-5) 
- 
ASLR range 
test (0-
90degrees) 
Pain medication 
use (No of 
medication per 
category) 
Functional tests: 
- 
ASLR (0-5) 
ASLR range test 
(0-90degrees) 
Pain medication use (No 
of medication per 
category) 
 
Data analysis 
Data from the intervention groups will be compared based on the intention to treat (ITT) 
principle). Statistical comparisons in order to test differences between 2 independent groups 
will be made by the Student´s t-test or, in the case of a non-normal distribution, the Mann-
Whitney U-test. To assess contingency tables, the chi square test will be used or, in the case 
of small expected frequencies, Fischer´s exact test. Descriptive statistics will be used to 
characterize the data. A p-value of <0.05 will be considered as significant. A sensitivity 
analysis will be performed comparing the intention to treat data against the per-protocol data 
exclusively from patients who complied with the study protocol. The proportion of patients in 
both intervention groups who obtain a clinically significant improvement of 2 points and more 
on the NRS scale will be compared.  

 
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In addition, a linear mixed model for repeated measures with a subject-specific random 
intercept will be used to assess results at the different follow-up time points using the outcome 
measurements during follow-up as dependent variable and the outcome variable at baseline, 
time, intervention and the interaction term between time and intervention as fixed effects. 
For the primary outcome measure NRS for the operated sacroiliac joint measured at the day of 
the 6-month follow-up is used.  
For the secondary outcomes the baseline value will be taken from the preinjection time point. 
Where such data is not available at this time point, baseline data will be collected from the 
preoperative measure point. These baseline values will be compared with values at 3 and 6 
month follow-up. 
 All statistical analysis will be performed by a blinded statistician. The code for group 
belonging will not be broken until the analyses and interpretations of the results have been 
performed. Data will be analyzed using IBM SPSS statistical software, version 28.0.1.1 (14). 
An independent blinded statistician will do additional analyses using STATA statistical 
software.  
 
Shell tables 
10. Demographics 
Variable 
Intervention group (N=n, 
CI 95%) 
Control group(N=n, CI 
95%) 
Age 
20-29:N= 
30-39: N= 
40-49:N= 
50-59: N= 
60-70: N= 
Age groups: 
20-29:N= 
30-39: N= 
40-49:N= 
50-59: N= 
60-70: N= 
Age groups: 
20-29:N= 
30-39: N= 
40-49:N= 
50-59: N= 
60-70: N= 
Sex 
- 
Female 
Female N= / male N= 
Female N= / male N= 

 
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- 
Male 
Civil status 
- 
Married 
- 
Partner 
- 
Single 
 
 
Employment status: 
- 
Employed 
- 
Sick leave: 
o 
Partial (<25%, 25-
50%, 50-75%) 
o 
Full (100%) 
 
 
No of Children 
 
 
BMI and Weight/Height 
 
 
Ambulatory without assistance 
 
 
Prior Lumbar fusion 
 
 
Underlying diagnosis n(%) 
- 
Pregnancy 
- 
Trauma 
- 
Idiopathic 
 
 
Previous comorbidities (number 
of) 
 
 
Taking opioids, n (%) 
 
 
Preinjection: 
- 
ODI, score, mean (+/- SD) 
- 
PGQ, score, mean (+/-SD 
- 
NRS, score, mean (+/- SD) 
o 
operated SIJ 
o 
contralateral SIJ 
o 
global pelvic pain 
o 
leg pain 
- 
Eq-5D index 
 
 
 
 
 
 

 
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11. Group difference in NRS sacroiliac joint fusion group versus sham group. Improvement 
NRS sacroiliac joint fusion group versus sham group. Also demonstrated graphically. 
Months 
Group difference between surgical group and control group of pain 
intensity in operated SIJ measured with NRS  
Baseline (0) n/N and mean score, CI 95% 
3months 
n/N and mean score, CI 95% 
6 months 
n/N and mean score, Ci 95% 
 
12. NRS values in sacroiliac joint fusion group compared to sham group. Also demonstrated 
graphically. 
Months 
NRS operated SIJ 
 
Surgery 
Sham 
Baseline (0) n/N and mean score, CI 95% 
n/N and mean score, CI 95% 
3months 
n/N and mean score, CI 95% 
n/N and mean score, CI95% 
6 months 
n/N and mean score, Ci 95% 
n/N and mean score, CI 95% 
 
13. Improvement in NRS shell table proportions 
Months 
NRS operated SIJ improvement 
of 2 points or more 
NRS global pelvic pain 
improvement of 2 points or more 
 
Surgery 
Sham 
Surgery 
Sham 
Baseline (0) 
n/N and % 
n/N and % 
n/N and % 
n/N and % 
3months 
n/N and % 
n/N and % 
n/N and % 
n/N and % 
6 months 
n/N and % 
n/N and % 
n/N and % 
n/N and % 
 

 
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14. Improvement in ODI and PGQ  
Months 
ODI 
PGQ 
 
Surgery 
Sham 
Surgery 
Sham 
Baseline (0) mean score, CI 
95% 
mean score, CI 
95% 
mean score, CI 
95% 
mean score, CI 
95% 
3months 
mean score, CI 
95% 
mean score, CI 
95% 
mean score, CI 
95% 
mean score, CI 
95% 
6 months 
mean score, CI 
95% 
mean score, CI 
95% 
mean score, CI 
95% 
mean score, CI 
95% 
 
15. Improvement in TUG and 6MWT 
Months 
TUG 
6MWT 
 
Surgery 
Sham 
Surgery 
Sham 
Baseline (0) mean score, CI 
95% 
mean score, CI 
95% 
mean score, CI 
95% 
mean score, CI 
95% 
3months 
mean score, CI 
95% 
mean score, CI 
95% 
mean score, CI 
95% 
mean score, CI 
95% 
6 months 
mean score, CI 
95% 
mean score, CI 
95% 
mean score, CI 
95% 
mean score, CI 
95% 
7. Shell tables for other outcomes will look and contain similar content as the examples 
above.  
 
DISCUSSION 
Minimally invasive sacroiliac joint fusion is increasingly used worldwide with reported 
reduced pain, improved physical function and quality of life compared to non-operative 
treatment in two industry-sponsored RCTs (Polly et al. 2016a; Sturesson et al. 2016). Both 
showed a clinically and statistically significant difference between the surgically and non-
operatively treated groups with greater pain reduction in the surgically treated group (Polly et 
al. 2016a; Sturesson et al. 2016). It is a weakness that the studies were industry-sponsored. 
Further, a placebo effect might have contributed to the reported superiority of minimally 
invasive sacroiliac joint fusion.  

 
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To what extent a placebo effect influences the result after minimally invasive sacroiliac joint 
fusion is not known. A placebo effect after surgery has been shown to be an important factor 
in efficacy (Turner et al. 1994). Both patient and health care provider can influence a placebo 
effect on treatment results. This has particularly been shown in treatment of chronic pain, 
where the psychological component is believed to be important. Patients with long-lasting 
diseases seem to be poorer placebo responders, but on the other hand placebo tend to work 
better in patients expecting to have changes in sensation of pain (Vandana et al. 2001).  
Several sham controlled studies in orthopedic surgery have shown comparable pain relief in 
both groups, such as Moseley et al (2002) and Schrøder et al. (2017).  Hence, the effect of 
minimally invasive sacroiliac joint fusion might be explained by placebo, but this is yet to be 
examined. 
The ethical dilemma of sham surgery is relevant. To ask patients to undergo general 
anaesthesia for sham surgery might seem unethical. However, a German study of 1,37 million 
anaesthetic procedures with elective patients, graded as ASA classification physical status I 
and II, showed 7,3 cases of death or serious complication per million cases, corresponding to 
a very low risk (Schiff et al. 2014). All types of surgery are associated with risks of 
complications, and so also for minimally invasive sacroiliac joint fusion (Shamrock et al. 
2019). In the control group the risks for surgical complications should be very low. A possible 
result showing sham surgery to be equal to minimally invasive sacroiliac joint fusion might 
spare thousands of people from undergoing unnecessary elective surgery with the risk and 
costs such surgery entail. We therefore find it ethically acceptable to complete a sham-
controlled double-blinded randomized prospective study.  
Ethics, registration, funding and potential conflicts of interest 
Ethical approval for the study has been granted in Norway by the Ethics Committee Health 
Region Southeast, Oslo, Norway (2017/1892/REK sør-øst A), and in Sweden from The 
Regional Ethics Committee in Stockholm, Sweden (nr: 2018/1463-31). 
The protocol of this study is registered with clinicaltrials.gov (NCT03507049)  
The final result from this study will be published in peer-reviewed international journals and 
also disseminated through international congress lectures. 
This trial has received funding from Sophies Minde AS in form of salary payment for the 
fellow. The Division of Orthopeadic Surgery, Oslo University Hospital is covering the costs 

 
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of the Norwegian arm of the trial. Metodrådet Stockholm-Gotland covered costs for the 
ethical consent application in Sweden.  Paul Gerdhem is supported by Region Stockholm (for 
a clinical research appointment) and CIMED, Karolinska Institutet. 
None of the principal investigators have any financial or competing interests. 
Aknowledgements 
We gratefully acknowledge the assistance of the Division of Orthopaedic Surgery at Oslo 
University Hospital and Karolinska University Hospital for sponsoring and facilitating the 
trial.  
References: 
Aldabe, Daniela, Stephan Milosavljevic, and Melanie Dawn Bussey. 2012. 'Is pregnancy 
related pelvic girdle pain associated with altered kinematic, kinetic and motor control 
of the pelvis? A systematic review', European Spine Journal, 21: 1777-87. 
Cher, Daniel, David Polly, and Sigurd Berven. 2014. 'Sacroiliac joint pain: burden of disease', 
Medical Devices (Auckland, NZ), 7: 73. 
Cohen, Steven P., Robert W. Hurley, rd Chester C. Buckenmaier, Connie Kurihara, Benny 
Morlando, and Anthony Dragovich. 2008. 'Randomized placebo-controlled study 
evaluating lateral branch radiofrequency denervation for sacroiliac joint pain', 
Anesthesiology, 109: 279-88. 
Copay, Anne G., and J. Cher Daniel. 2016. 'Is the Oswestry Disability Index a valid measure 
of response to sacroiliac joint treatment?', Qual Life Res, 25: 283-92. 
DePalma, M.J., J.M. Ketchum, and T.R. Saullo. 2011. 'Etiology of chronic low back pain in 
patients having undergone lumbar fusion', Pain Med., 12: 732-39. 
Duhon, Bradley S, Fabien Bitan, Harry Lockstadt, Don Kovalsky, Daniel Cher, Travis Hillen, 
and SIFI Study Group. 2016. 'Triangular titanium implants for minimally invasive 
sacroiliac joint fusion: 2-year follow-up from a prospective multicenter trial', 
International Journal of Spine Surgery, 10. 
Elgafy, H., H.B. Semaan, N.A. Ebraheim, and R.J. Coombs. 2001. 'Computed tomography 
findings in patients with sacroiliac pain', Clin.Orthop.Relat Res.: 112-18.  
EQ-5D Foundation, Euroqol Research. 2017. 'EG-5D-5L About', Accessed 5 Oct. 
https://euroqol.org/eq-5d-instruments/eq-5d-5l-about/. 
Farrar, John T, James P Young, Linda LaMoreaux, John L Werth, and R Michael Poole. 
2001. 'Clinical importance of changes in chronic pain intensity measured on an 11-
point numerical pain rating scale', Pain, 94: 149-58. 

 
SIFSO Protocol version 003 
SIFSO 
22
Fuchs, Volker, and Benjamin Ruhl. 2018. 'Distraction arthrodesis of the sacroiliac joint: 2-
year results of a descriptive prospective multi-center cohort study in 171 patients', 
European Spine Journal, 27: 194-204. 
Hagg, O., P. Fritzell, and A. Nordwall. 2003. 'The clinical importance of changes in outcome 
scores after treatment for chronic low back pain', Eur.Spine J., 12: 12-20. 
Hollis, S., and F. Campbell. 1999. 'What is meant by intention to treat analysis? Survey of 
published randomised controlled trials', BMJ, 319: 670-4. 
Kennedy, David J., Andrew Engel, D. Scott Kreiner, Devi Nampiaparampil, Belinda 
Duszynski, and John MacVicar. 2015. 'Fluoroscopically Guided Diagnostic and 
Therapeutic Intra‐Articular Sacroiliac Joint Injections: A Systematic Review', Pain 
Med, 16: 1500-18. 
Kibsgard, T.J., O. Roise, E. Sudmann, and B. Stuge. 2013. 'Pelvic joint fusions in patients 
with chronic pelvic girdle pain: a 23-year follow-up', Eur.Spine J., 22: 871-77. 
Kim, Woong Mo, Hyung Gon Lee, Cheol Won Jeong, Chang Mo Kim, and Myung Ha Yoon. 
2010. 'A randomized controlled trial of intra-articular prolotherapy versus steroid 
injection for sacroiliac joint pain', J Altern Complement Med, 16: 1285-90. 
Laslett, M., C.N. Aprill, B. McDonald, and S.B. Young. 2005. 'Diagnosis of sacroiliac joint 
pain: validity of individual provocation tests and composites of tests', Man.Ther., 10: 
207-18. 
Ledonio, Charles G. T., David W. Polly Jr, and Marc F. Swiontkowski. 2014. 'Minimally 
Invasive Versus Open Sacroiliac Joint Fusion: Are They Similarly Safe and 
Effective?', Clin Orthop Relat Res, 472: 1831-38. 
Luukkainen, R. K., P. V. Wennerstrand, H. H. Kautiainen, M. T. Sanila, and E. L. Asikainen. 
2002. 'Efficacy of periarticular corticosteroid treatment of the sacroiliac joint in non-
spondylarthropathic patients with chronic low back pain in the region of the sacroiliac 
joint', Clin Exp Rheumatol, 20: 52. 
Miller, Larry E., and Jon E. Block. 2014. 'Minimally invasive arthrodesis for chronic 
sacroiliac joint dysfunction using the SImmetry SI Joint Fusion system', Med Devices 
(Auckl), 7: 125-30. 
Moseley, J Bruce, Kimberly O'malley, Nancy J Petersen, Terri J Menke, Baruch A Brody, 
David H Kuykendall, John C Hollingsworth, Carol M Ashton, and Nelda P Wray. 
2002. 'A controlled trial of arthroscopic surgery for osteoarthritis of the knee', New 
England Journal of Medicine, 347: 81-88. 

 
SIFSO Protocol version 003 
SIFSO 
23
Patel, Nilesh, Andrew Gross, Lora Brown, and Gennady Gekht. 2012. 'A Randomized, 
Placebo‐Controlled Study to Assess the Efficacy of Lateral Branch Neurotomy for 
Chronic Sacroiliac Joint Pain', Pain Med, 13: 383-98. 
Polly, David W, Daniel Cher, Kathryn Wine, Peter Whang, Clay Frank, Harry Lockstadt, 
Charles Harvey, and Jonathan Sembrano. 2016a. 'Randomized Controlled Trial of 
Minimally Invasive Sacroiliac Joint Fusion Using Triangular Titanium Implants vs. 
NonSurgical Management for Sacroiliac Joint Dysfunction', Global Spine Journal, 6: 
GP113. 
Polly, David W, John Swofford, Peter G Whang, Clay J Frank, John A Glaser, Robert P 
Limoni, Daniel J Cher, Kathryn D Wine, Jonathan N Sembrano, and INSITE Study 
Group. 2016b. 'Two-Year Outcomes from a Randomized Controlled Trial of 
Minimally Invasive Sacroiliac Joint Fusion vs. Non-Surgical Management for 
Sacroiliac Joint Dysfunction', International Journal of Spine Surgery, 10. 
Rappoport, Louis H., Ingrid Y. Luna, and Gita Joshua. 2017. 'Minimally Invasive Sacroiliac 
Joint Fusion Using a Novel Hydroxyapatite-Coated Screw: Preliminary 1-Year 
Clinical and Radiographic Results of a 2-Year Prospective Study.(Clinical report)', 
World Neurosurgery, 101: 493. 
Sachs, D., and R. Capobianco. 2012. 'One year successful outcomes for novel sacroiliac joint 
arthrodesis system', Ann.Surg.Innov.Res., 6: 13. 
Sachs, D., and R. Capobianco. 2013. 'Minimally invasive sacroiliac joint fusion: one-year 
outcomes in 40 patients', Adv.Orthop., 2013: 536128. 
Sakamoto, Naotoshi, Toshihiko Yamashita, Tsuneo Takebayashi, Masatoshi Sekine, and 
Seiichi Ishii. 2001. 'An Electrophysiologic Study of Mechanoreceptors in the 
Sacroiliac Joint and Adjacent Tissues', Spine (Phila Pa 1976), 26: E468-E71. 
Schiff, JH, A Welker, B Fohr, A Henn-Beilharz, U Bothner, H Van Aken, A Schleppers, HJ 
Baldering, and W Heinrichs. 2014. 'Major incidents and complications in otherwise 
healthy patients undergoing elective procedures: results based on 1.37 million 
anaesthetic procedures', British journal of anaesthesia, 113: 109-21. 
Schrøder, Cecilie Piene, Øystein Skare, Olav Reikerås, Petter Mowinckel, and Jens Ivar Brox. 
2017. 'Sham surgery versus labral repair or biceps tenodesis for type II SLAP lesions 
of the shoulder: a three-armed randomised clinical trial', Br J Sports Med: bjsports-
2016-097098. 
Sembrano, Jonathan N., and David W. Polly. 2009. 'How Often Is Low Back Pain Not 
Coming From the Back?', Spine (Phila Pa 1976), 34: E27-E32. 

 
SIFSO Protocol version 003 
SIFSO 
24
Shamrock, A. G., A. Patel, M. Alam, K. H. Shamrock, and M. Al Maaieh. 2019. 'The Safety 
Profile of Percutaneous Minimally Invasive Sacroiliac Joint Fusion', Global Spine J, 
9: 874-80. 
SI BONE. 2020. 'iFuse surgical technique', Accessed December 3. https://si-
bone.com/providers/solutions/ifuse/surgical-technique. 
Smith-Petersen, M.N., and William A. Rogers. 1926. 'End-Result Study of Arthrodesis of the 
Sacro-Iliac Joint for ArthritisGÇöTraumatic and Non-Traumatic', The Journal of Bone 
& Joint Surgery, 8: 118-36. 
Stuge, B., A. Garratt, Jenssen H. Krogstad, and M. Grotle. 2011. 'The pelvic girdle 
questionnaire: a condition-specific instrument for assessing activity limitations and 
symptoms in people with pelvic girdle pain', Phys.Ther., 91: 1096-108. 
Sturesson, Bengt, Julius Dengler, Djaja Kools, Robert Pflugmacher, and Domenico 
Prestamburgo. 2016. 'Sacroiliac minimal invasive fusion compared to physical 
therapy: six-month outcome from a multicentre randomised controlled trial', The Spine 
Journal, 16: S73-S74. 
Szadek, K.M., P.V. Hoogland, W.W. Zuurmond, J.J. De Lange, and R.S. Perez. 2008. 
'Nociceptive nerve fibers in the sacroiliac joint in humans', Reg Anesth.Pain Med, 33: 
36-43. 
Turner, J.A., R.A. Deyo, J.D. Loeser, Korff M. Von, and W.E. Fordyce. 1994. 'The 
importance of placebo effects in pain treatment and research', JAMA, 271: 1609-14. 
Vandana, R., and R. Tushar. 2001. 'Placebos: current status', Indian journal of pharmacology, 
33: 396-409. 
Viedoc. 2021. 'Viedoc', Accessed 04-09. https://www.viedoc.com. 
Vleeming, A., H.B. Albert, H.C. Ostgaard, B. Sturesson, and B. Stuge. 2008. 'European 
guidelines for the diagnosis and treatment of pelvic girdle pain', Eur.Spine J., 17: 794-
819. 
Vleeming, A., M.D. Schuenke, A.T. Masi, J.E. Carreiro, L. Danneels, and F.H. Willard. 2012. 
'The sacroiliac joint: an overview of its anatomy, function and potential clinical 
implications', J.Anat., 221: 537-67. 
Whang, Peter G., Emily Darr, S. Craig Meyer, Don Kovalsky, Clay Frank, Harry Lockstadt, 
Robert Limoni, Andy Redmond, Philip Ploska, Michael Oh, Abhineet Chowdhary, 
Daniel Cher, and Travis Hillen. 2019. 'Long-Term Prospective Clinical And 
Radiographic Outcomes After Minimally Invasive Lateral Transiliac Sacroiliac Joint 

 
SIFSO Protocol version 003 
SIFSO 
25
Fusion Using Triangular Titanium Implants', Medical Devices: Evidence and 
Research, 12: 411-22.