INSITE data indicate efficacy of minimally invasive sacroiliac joint fusion


Delegates at the annual meeting of the International Society for the Advancement of Spine Surgery (ISASS; 15–17 April, San Diego, USA), received an update out to six months on the INSITE trial from Peter Whang. The trial compares the use of minimally invasive sacroiliac joint fusion using iFuse implants (SI-Bone) with non-surgical management to treat chronic sacroiliac joint dysfunction.

Peter Whang, Yale University School of Medicine, USA, told delegates that previous studies indicate that up to 15% of chronic low back pain can be attributed to the sacroiliac joint, and though promising case series have been published previously, there still exists a “paucity of high-quality prospective randomised controlled clinical trials”. Despite this lack of data, interest in the field—both clinical and commercial—is growing.

The six-month data from INSITE—a multicentre randomised controlled trial—has gone some way in addressing this paucity, indicating that the minimally invasive fusion approach using triangular implants was significantly more successful than non-surgical treatment.

In the sacroiliac joint fusion group, mean joint pain improved from 82.3 (0 to 100 scale) at baseline to 29.8 at six months—a 53-point drop. By contrast, the non-surgical group showed little improvement with only a 12-point drop from 82.2 to 70.4. Six-month improvement in pain was 40.5 points greater in the surgery group (p<0.0001). Disability scores (measured using the Oswestry Disability Index) improved by 30 points in the surgery group vs. 4.9 points in non-surgical patients (difference in means, p<0.0001).

Quality of life outcomes, as measured by EQ-5D and SF-36, showed statistically significant differences in improvements in the iFuse group compared to non-surgical management for all subdomains. The study’s primary clinical endpoint was overall treatment success defined as patients who achieved clinically significant pain improvement (>= 20 point drop in Visual Analogue Scale score), no device-related complications, no neurologic worsening, and no reintervention. The fusion group saw 81.4% of the patients achieve overall treatment success compared with 23.9% for the non-surgical group.


Peter Whang spoke to Spinal News International about the study, and about what the data means for the ongoing debate over sacroiliac joint treatment.

How has the treatment of sacroiliac joint pain developed?

Back pain is still not well-understood and we know that there are a lot of different things that can cause it. Obviously, as spinal surgeons, we tend to focus on the lumbar spine—is it the disc, is it the facet joint, is it neurocompression? The one condition that I think has become better recognised as a source of axial back pain is the sacroiliac joint, and that is really something that has come to the forefront in the past several years and something that we have gotten a lot better at identifying and treating.

In the past when we thought someone had sacroiliac joint pain there were not many good treatment options. We used things like medication, physical therapies, injections and nerve ablations, but none of those really represented good long-term solutions because sacroiliac joint  dysfunction is a mechanical problem. The challenges up to this point have been diagnosing the problem correctly and finding reliable treatments. In the past, sacroiliac joint fusions were done via an open technique causing a lot of damage to soft tissues, and this was largely for people who had major pelvic injuries from car accidents and things like that. With the advent of less invasive fusion procedures, we now have a more effective way to treat this pain.

Why has attention on the sacroiliac joint increased in recent years?

I think that now we have alternative approaches with minimally invasive techniques that cause less damage we are more willing to approach the problem. I also think one important step forward is that we have good data from the INSITE trial, suggesting that this minimally invasive fusion may be superior to non-operative care. Obviously with new technologies the burden of proof is on us to show that it is better than the existing options. That is exactly what this data are showing, that this method not only has potential but actually does appear to provide better outcomes that non-operative care.

How can you be sure that symptoms are associated with problems in the sacroiliac joint?

I think, as with any condition, diagnosis is critical. The success of this and any other procedure we do is based on establishing that correct diagnosis—if you have someone with hip arthritis or a degenerative disc and you treat the sacroiliac joint, they are not going to improve. The success is contingent upon establishing the fact that the pain is arising from the sacroiliac joint.

I think something that is important is a patient’s response to injections. If you inject local anaesthetic into the joint and that was the source of the pain, the patient should have temporary relief—and that means 50% or more relief, which is what I look for when I am talking to my patients. If their pain was gone for eight hours after the injection then I am pretty convinced that the pain is coming from the sacroiliac joint. If the pain is helped a little bit for five minutes and then it was no different, I am going to focus on other things in the lumbar spine or the hip. So I think that, in particular for the sacroiliac joint, it is really important that we establish the correct diagnosis because there are a lot of different things that can cause similar symptoms.

Are more and better data the way to convince the sceptics?

Yes. I do not blame them for being apprehensive. We see new techniques all the time and it is up to us to show through good studies that what we have is as good as or better than existing options. So I certainly would not fault someone for being unsure as this is something that has only more recently come to the forefront. As physicians talk more about it, hopefully we will get more comfortable with the idea.

At this point I can say that, when the diagnosis is correct, I have been shocked with how well people do. I always say that if my lumbar spine patients did as well as my sacroiliac joint patients I would be a happy man.

Do you think these results could be reproduced by other systems on the market?

I think that there is potential for different materials and different surgical approaches—some of the implants take a different approach and a different trajectory. I do not think you can really translate the data from a study like the INSITE trial which uses a specific shape, material and surgical approach to comment on any other techniques, because I think there could potentially be big differences. For example, if you have a screw as opposed to a triangular implant you have to take a different trajectory, which may give different results. This study was specific to the iFuse procedure, which is different to a lot of other procedures on the market.

Can we expect to see a proliferation of sacroiliac joint fusion devices and techniques in the future?

Yes. And at that point there will need to be comparative studies done comparing different materials, shapes, trajectories and so on. This field is still in its infancy and ours is the landmark study showing that this specific technique has the potential to be better than non-operative care. Once this is legitimised then we can start talking about other implants and material and I think that is when the comparative studies will come—INSITE is the foundation for these future comparative studies.

What is the current state of the sacroiliac joint treatment debate?

I think the controversy is still there. I think that certainly sacroiliac joint-mediated pain and fusion for this condition is now better accepted, and I think that the fact we are seeing debates at major meetings is a step forward—a few years ago people would not have even been talking about this.

Up until this point there has not been a lot of good data. There have been retrospective studies or small series of patients showing that this technique may be effective, but you really have not had that high level prospective randomised data. That is what we are going to be seeing with the INSITE trial. I am not surprised that there is still some controversy surrounding this technique, but I think that the results of this study will go a long way to settling things and hopefully convincing people that this is something that has merit.