The autograft or iliac crest bone graft is not taken anywhere near the sacroiliac joint. The pelvis is a ring that is open in the front on the top but closed on the bottom. You can feel this by putting your hand on your “hips” where your belt line is. You can follow your pelvis from the back around to the front but this bony line stops at your ASIS (anterior superior iliac spine). This is really not a “spine” but the front endpoint of the upper ring.
If you palpated deeply, you would find that this ring drops but continues around at your pubis, the hard bony “knot” at the front of the groin.
The graft is taken from the top side of the pelvis at about the front third of the wing of the pelvis. This area is not weight bearing and the width of the graft is almost a perfect fit for the disc space of the cervical spine. The incision is small and a study I performed (unpublished) found that after six weeks, only 2% of patients has symptoms of a 1-2 on a 1-10 scale.
There is no risk to the sacroiliac joint and I have never had a patient with sacroiliac joint dysfunction who had a graft from the pelvis.
I have for the past 8 years given patients the option of placing sterile coral- yes coral in the graft site. Coral is calcium carbonate and the porosity of coral is almost exactly like bone. Bone grows into this material and incorporates like it was bone. This in my opinion alleviates any pain or discomfort from the graft site and is very well accepted.
The only downside is that patients will develop gills behind their ears and webbed fingers but no one has complained about this side effect;)
Hetertopic ossification is bone formation in regions that it is not functional (not useful and hinders the function of the region). Artificial discs do have the possibility of this abnormal bone formation but I have not had this happen to any of my patients. I believe that my preparation of the disc site reduces the chance of this from occurring but certainly this abnormal ossification is a possibility.