Paper of the month June 2023 - No. 1

Patient-Reported and Radiographic Outcomes After Revision of Sacroiliac Joint Fusion.
Int J Spine Surg. 2023 Apr;17(2):250-257.
Thompson JC, Marigi E, Cross WW 3rd.

This is the most numerous revision case series after primary SIJ fusion surgery reported by Dr. William Cross, et al.

I like his concept of a surgical procedure based on the principles of arthrodesis in orthopedic surgery, i.e., (1) joint decortication, (2) bone grafting, (3) compression, and (4) rigid internal fixation. The most characteristic feature of this technique is the rigid fixation by a highly skilled trauma surgeon. The technical difficulty of this procedure is unknown.

Followings are my questions to authors of this paper.

  1. The operative time and blood loss may vary depending on the condition of each patient, but I wonder how it was in the revision cases.
  2. What kind of implants are used in the most difficult revision cases and what anatomical characteristics they have?
  3. How long would the surgery take if it were performed as a primary surgery, how much blood loss would occur, and what are the key points of the procedure?
  4. What was the history of the cases that led to this revision? Since most of the patients' symptoms improved after the revision surgery, there is no possibility that the cases were misdiagnosed. If this is the case, I would like to know what kind of post-operative care the patients had with their previous surgeons, and what kind of occupations and lifestyles necessitated the revision surgery.

Many of the revision cases were considered to have pseudoarthrosis on imaging in this study.

It is possible that the primary surgery was not strong enough to hold the SIJ in place to control micromotion. Or perhaps the fixation was good initially, but micromotion occurred later and the pain recurred. If the latter is the case, the lack of bone bridging could certainly be considered pseudoarthrosis. However, I thought it might be difficult to determine whether it was pseudarthrosis or not on imaging.

I really think that being able to do these revisions properly is the qualification of a true sacroiliac surgeon. To avoid revision cases, the type of implant used may be related, but it also depends on the quality of the patient's subsequent lifestyle management and rehabilitation (when to start weight bearing, not to allow stair climbing, etc...).

After learning directly from Drs. Sturesson and Kibsgård about postoperative care, I thought that the number of revision cases with them might be low because they are very careful about it.

In 2018, when there was a SIMEG meeting in Tampa, the radiologist who underwent the SIJ fusion surgery was looking for a surgeon who could do a revision. In other words, the surgeon who performed the surgery the first time could not perform the revision. He mentioned that he had seen a CT of his pelvis and that obviously the implants had loosened and his symptoms had returned. That would be a problem. The revision rate after MIS SIJ surgery is not high. However, it is always present. In this paper, Dr. Cross et al. provide an answer as to how we surgeons should handle these cases. I am very grateful to them, and we should make sure that cases requiring revision go through the proper route to his institution and to his colleagues who have mastered this revision technique. Of course, postoperative care should be careful to prevent revision surgery. It will be an important activity of our SIMEG to make this known.

From my own anatomical studies, I have learned that SIJs are structurally stabilized by applying compression. So, I like his surgical concepts. I hope to visit his institution in the near future to see his surgery.

Daisuke Kurosawa


Paper of the month June 2023 - No. 2

Dr. Dall published this interesting article in January 2023 that examines obesity and outcomes after sacroiliac joint fusion surgery. A PDF of this article is available by entering the title in "Google scholar".

Patients with Severe and morbid obese had more adverse events such as screw breakage and loose screw. There have been no reports on the degree of such obesity and the outcome of sacroiliac joint fusion. This Paper is the foundation for encouraging more large-scale surveys.  

Dr. Bengt Sturesson recommended 50% partial weight bearing for up to 6 weeks postoperatively, and Dr. Kibsgard recommended more than 8 weeks of partial weight bearing. The amount of 50% partial weight bearing depends on the weight of each patient, but since the size of the pelvis does not vary that much from person to person, an overloaded pelvis would certainly increase the risk of implant breakage and pseudoarthrosis.

I would very much like to hear from our member surgeons.

  • Do you order weight loss preoperatively? Weight loss through exercise seems to be difficult in chronic pain cases.
  • Do any of your facilities work with nutrition specialists on calorie restriction, etc.?
  • What kind of post-operative care do you provide, especially for the morbidly obese?

Any other active feedback would be very welcome.

Daisuke Kurosawa

Leave a Comment

Comment by Bruce Dall |

The question surrounding limiting weight bearing in majorly obese SIJ fusion patients is a good one. I used two surgical techniques (one open, one minimally invasive) during my career and never restricted immediate full weight bearing in anyone. The technique I used in all the patients in this study was the posterior midline fascial splitting muscle sparing procedure. This technique utilizes both distraction and compression with very rigid fixation. This was also my go to salvage procedure for those especially difficult redoes. The technique can be visualized in a 14 minute video I put together on YouTube:

It can also be read about in the textbook “Surgery for the painful dysfunctional sacroiliac joint: a clinical guide”, which is in the references of the article we’re discussing. I do not know if limiting weight bearing in my morbidly obese patients would have eliminated loosening in the few cases in which it occurred. My philosophy has been to fixate these types of patients as rigidly as possible during the operation as I did not feel they were capable of limited weight bearing the postop period. I felt they needed to move as much as possible right out of the gate to prevent them from developing medical complications. Any limitation of weight bearing in this group would essentially be putting them in a chair or in bed.

Comment by William Cross |

I am honored to have my study selected as one of the papers of the month. Our revision practice continues to grow and we have been able to improve our outcomes steadily. Furthermore, as we gained more experience with implant removals, surgeries have become more efficient and less morbid.

Dr. Kurosawa raises some excellent points and is very insightful with his comments. I would like to specifically address some of his comments and questions.

The operative time and blood loss in revision cases are certainly longer than in the primary setting but not to the extent where complications increase and hospital admissions are prolonged. The vast majority of revision cases are overnight observation cases whereas patients are discharged at 1200 the next day.

Most of the revision cases in the series were transfixation style implants relying upon ingrowth in the ilium and sacrum while bridging the SI joint. Often, loosening occurred in the porous sacral ala but in a few cases, there was loosening in the ilium. We saw both triangular and round implants used. Since this series was published, I am seeing more referrals for loose or malpositioned allograft implants inserted posteriorly. In cases where significant ingrowth has occured, implant/company specific removal trays are available which work very well and in other cases (round static screws/cylinders) where the implant won't easily screw out, a large trephine is used.

In terms of time for revision surgeries, it is variable. I will certainly say that we are much faster than we used to be! This highlights the learning curve for revision surgeries. Currently, removal of implants typically takes 30 minutes or less and the revision fusion takes an additional 30-45 minutes. As we decorticate the joint, the tool used here has to work through quite a bit of sclerosis in an effort to expose good bone to facilitate fusion. Blood loss is typically less than 300cc. The key points I stress intraoperatively are to ensure complete access to all sides of the implant. This facilitates easier removal with the extraction tools.

The critical point in any SIJ surgery and especially that of revisions is diagnosis. I typically use the same provacative tests as with primary cases and also get the injection. If exam and injection (>50% relief) are positive, and imaging shows no bridging bone or loosening (or a malpositioned implant), I will offer revision surgery.

Postoperatively, patients are usually weight-bearing as tolerated using crutches or a walker for comfort only. This is my same protocol for primary cases. To my knowledge, we have had zero revisions for loosening with this protocol.

I am honored to have our article selected by Dr. Kurosawa and look forward to learning more from his expertise in the field of SI joint dysfunction.

What is the sum of 2 and 5?