Minimally Invasive Posterior or Transarticular Approach to Sacroiliac Joint Fusion?

Meeting Highlight from the 31st Annual Meeting of the Section on Disorders of the Spine and Peripheral Nerves—Spine Summit 2015

Hector E. Soriano-Baron, MD presented, Sacro-Iliac Joint Fusion with Two Different Minimally Invasive Techniques: Posterior vs. Trans-Articular, Biomechanical Analysis during the 31st Annual Meeting of the Section on Disorders of the Spine and Peripheral Nerves—Spine Summit 2015 in Phoenix, AZ.

Sacroiliac jointUp to 20% of low back pain can be caused by one or both sacroiliac (SI) joints. Diagnosis of the SI joint as the pain generator can be challenging and requires positive response to provocative maneuvers and image-guide injection(s). If nonoperative treatment fails to reduce pain and relieve other SI-joint-related symptoms, a minimally invasive procedure to fuse the joint may be considered.

In his presentation, Dr. Soriano-Baron discussed posterior and transarticular implantation of fusion devices. This in vitro study compares both procedures in the context of range of motion (ROM):

  • ROM of normal SI joints
  • ROM of destabilized SI joints
  • ROM of fused SI joints

“In the last couple of years, there have been many papers that show minimally invasive placement into the SI joint with implants can be a potentially successful treatment option for these patients— with improvement in pain and disability up to five years postop when the conservative measurements have failed,” stated Dr. Soriano-Baron. With that said, Dr. Soriano-Baron cautioned that the sacrum is complex, the anatomy is variable, and sacral bone mineral density varies. Similar to other regions of the spine, the surgeon must carefully consider screw length, orientation, and trajectory chosen as these decisions can affect the construct’s strength.  

Previous Study
In a study performed by Barrow’s Neurological Institute a year prior, range of motion in flexion/extension decreased when a lateral approach was utilized to insert the implants. However, there was no difference in lateral bending or axial rotation. Dr. Soriano-Baron theorized:

  1. If the trajectory of the middle pin is altered to the sacral bone of greater density, it may be possible to achieve better results, and reduce ROM is all loading directions.
  2. The transarticular technique would be better than the traditional posterior approach.

Current Study: Methods
Seven cadaveric specimens were obtained that included L4-sacrum-pelvis.

  • 5 male/2 female, mean age 51.9±14.4 years
  • Bone mineral density (BMD) at L4: 0.905±0.345 g/cm2

The left (and later, the right) acetabulum was clamped and attached to the bottom of the testing frame; the contralateral side moved freely. ROM was assessed during single leg stance model, applications of pure moments (7.5 Nm) stimulated flexion/extension, lateral bending, and axial rotation.

Intact range of motion was measured to establish baselines. The pubic symphysis was cut to allow free movement of each side, and to have a paired analysis between the techniques for each specimen. iFuse implants (SI-BONE, San Jose, CA) were utilized: 7 mm wide and the device length dependent on the specimen.

Posterior Approach

  • First implant placed above the S1 neural foramen
  • Second implant placed lateral to S1
  • Third implant placed between S1 and S2

Transarticular Approach

  • First implant placed above the S1 neural foramen
  • Second implant placed anterior to the ala line to try to reach the anterior third of the sacral bone
  • Third implant placed over the projection of the ala line

Current Study: Results
“What we conclude from this study is that the insertion of implants to fuse the SI joint can be feasible, can diminish and decrease the range of motion in posterior and transarticular techniques—and the data showed no difference in between the techniques,” stated Dr. Soriano-Baron. 

Dr. Soriano-Baron concluded his presentation by stating, “But for me—and hopefully for you—the take-home message is SI joint can generate pain. Diagnosing it can be very challenging. And in the correct patient, these techniques can be very useful.”

This study was funded by SI-BONE.

Updated on: 09/23/16
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