Fusion of multiple lumbar segments associated with sacroiliac joint pain

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The number of segments involved in lumbar and lumbosacral procedures has been shown to affect the incidence of sacroiliac joint pain, in a study published online in Spine, confirming the symptom as a potential cause of low back pain following these procedures.

Noting published failure rates of between five and 30% for lumbar and lumbosacral spinal fusion procedures, as well as the increasing frequency of these surgeries, a team of researchers from the Akita Kousei Medical Center (Akita, Japan) performed a retrospective analysis of patient data to determine the primary causes of postoperative sacroiliac joint fusion pain. The team asserted that multiple authors have noted sacroiliac joint pain as a potential candidate for the cause of low back pain following lumbar fusion.

Using data from patients who had undergone lumbar or lumbosacral fusion at the Akita centre between June 2006 and June 2009, the researchers investigated the incidence of sacroiliac joint pain associated with both fixed and floating fusion, and the relationship between the number of segments involved in the fusion surgery and the rate of sacroiliac joint pain.

Two hundred and sixty-two patients who had not experienced preoperative sacroiliac joint pain were included in the study. Of these patients, 201 underwent a floating fusion and 61 also had their sacrum fused. Two (±1.4) segments were fused for each patient on average. After determining 66 patients who had developed low back pain postoperatively through the investigation of medical records, the authors used physical, neurological and imaging results to identify which patients had developed this as a result of sacroiliac joint pain. The gold-standard sacroiliac block was administered in patients with suspected sacroiliac joint pain. Diagnosis was made in 28 patients according to the diagnostic criteria recommended by Murakami et al (J Orthop Sci. 2007;12:274–80).

With regards to lumbar and lumbosacral fusion, the authors discovered that sacroiliac joint pain occurred in 20 of the 201 lumbar fusion patients (10%) and eight of the 61 lumbosacral patients (13.1%). Whilst this did trend towards lumbosacral fusion, the authors observed no significant difference. When comparing incidence of the symptom among fusion at different levels, the authors discovered that significantly more patients who underwent fusion of three or more segments (20% at 3, 22.5% at ≥4) developed postoperative sacroiliac joint pain.

The authors reviewed literature to determine a potential mechanism behind the presentation of sacroiliac joint pain following lumbar and lumbosacral fusion surgery. Given the insignificant difference between the presence of this symptom when the sacrum is fused as part of a lumbar fusion procedure, it could be more likely that sacroiliac joint pain is related to the fusion of multiple segments of the spine. “We consider that fusion of multiple segments can restrict the motion of the lumbar or thoracolumbar spine considerably depending on the number of involved spinal segments, consequently increasing stress at the sacroiliac joint,” the authors wrote.

Citing a body of literature reporting a transfer of load onto lower segments by the straightening of fused levels of the spine in adjacent segment disease following lumbar fusion, the authors speculate that a mechanism similar to that of adjacent segment disease following lumbar fusion surgery could explain sacroiliac joint pain. A body of literature has reported on the transfer of loads to lower levels from the straightening of fused segments in adjacent segment disease. In the case of sacroiliac joint pain, loads might also be transferred from fused segments onto the sacroiliac joint.

The authors note that the study is limited by its retrospective design, particularly with regards to the identification of patients who had latent sacroiliac joint fusion pain before surgery. They emphasise, however, that their screening was extensive. “We believe that our study shows the presence of sacroiliac joint fusion pain as a potential cause of low back pain…after lumbar/lumbosacral fusion,” they write.

Spinal News International spoke to lead author, Eiki Unoki, about these results, and their implications for physicians performing lumbar and lumbosacral fusions.

Why did you see sacroiliac joint pain as a likely explanation for cases of low back pain following lumbar fusion surgery?

We noticed that the postoperative symptoms differed from preoperative symptoms in some patients after lumbar or lumbosacral fusion. They presented pain in and around the right or left posterior superior iliac spine. We consider a pain around this area to be characteristic of sacroiliac joint pain. In Japan, Murakami’s One-Finger Test is very popular.1 That is, asking patients to indicate the main site of pain using their index finger. When patients can point to the posterior superior iliac spine, or within 2cm of it, as the main site of pain by one-finger test, the sacroiliac joint should be considered as an origin of the low back pain.

How could surgeons use this kind of data to improve lumbar fusion success rates?

Similar to adjacent segment disease, I think that sacroiliac joint pain cannot be completely prevented. In the case of multiple fusion, I think that it is dangerous when combined with fixation to the sacrum. This is because two risk factors occur at the same time, of which the fusion of multiple segments is the stronger participant. In our data, when we added sacral fusion cases to multiple segment (three or more) fusion cases, sacroiliac joint pain was 30% (six of 20). On the other hand, when we did fusions of multiple segments without sacral fixation, 17.8% (eight of 45) reported sacroiliac joint pain. This is significantly different.

If possible, one should extend fixation to the pelvis. An article by Ohtori et al found that development of sacroiliac joint pain was not seen in the case of pelvic fixation.2 I think that movement of sacroiliac joint could be limited in this case.

What future research is needed to better understand the failure rates associated with lumbar fusion procedures?

The onset of sacroiliac joint pain at the fixed lower end of the spine is an area which should be investigated. When multiple segments are fused to the sacral vertebrae, we can see that this is very high-risk. On the other hand, when we fuse to the pelvis—such as using S2-iliac screw—we see almost no sacroiliac joint pain. This is an area in which I would like to conduct future research.

References
1 Murakami E, Aizawa T, Noguchi K et al. Diagram specific to sacroiliac joint pain site indicated by one finger test. J.Orthop Sci. 2008; 13: 492-97

2 Ohtori S, Sainoh T, Takaso M et al. Clinical incidence of sacroiliac joint arthritis and pain after sacropelvic fixation for spinal deformity. Yonsei Med J. 2012; 53: 416-21