Many techniques in the past have been used to fuse the sacro iliac joints (SIJ). Most of them terrible. They often involved large open surgeries through the back to expose the joint, burr out the remaining cartilage and pack the defect with bone graft, and then stabilise the joint with some metal screws and implants while the bone graft consolidates and fuses the joint. Sometimes this is done at the time of lumbar spine surgery especially if older, posterior (through the back) techniques are used for long pedicle screw constructs. There are two reasons for this - firstly to make a secure base for the entire lumbar fusion to sit on, and second to actually treat SIJ degeneration which co-existed with the spine pathology.
To the right is a pretty gruesome picture of one of these types of techinique. The rods are connecting screws that go from the mid lumbar spine to the pelvis and the surgeon has opened the SIJ, removed the cartilage and packed it with bone graft then taken a chisel to the pelvis so that the bone graft will join and fuse the spine to the pelvis
The x-ray below shows what this looks like radiographically
These types of surgeries are ones we desperately try to avoid doing but unfortunately in rare cases they are actually necessary for the most complex of spinal deformities. One of the biggest complications though of this surgery is loosening of the screws and even fracture of the screws because the bone graft often does not mature quickly enough or, even worse, never actually works at all - especially common in smokers.
The x-ray to the right shows loosening of the screws in the pelvis due to failure of the bone graft. Loose metalwork in the spine is extremely painful and has to be removed, which in these cases means a redo of the large, horrible incision shown above. You will note that using these big, open techniques only one screw is placed across the SIJ. Another cause of failure in these cases is that this is often quite simply totally inadequate fixation and does not hold the SIJ rigidly still.
In keeping with our desire to avoid these big surgical exposures and adopt minimally invasive techniques instead I investigated mutiple devices and was the first surgeon in Australia to use and adopt the 'ifuse' device into my practice. This is a device which fuses the entire joint using 3 extremely rigid bolts placed through a 3-4cm incision on the side of the buttock. Not only is this minimally invasive but the 3 triangular bolts hold the joint instantly immobile. Bone grows onto the bolts because of it's special coating which attracts boney in-growth and thus the joint never moves again. The schematic below shows what this looks like. The surgery takes about 30-45 minutes per side and often patients go home the next day. Sometimes they partial weight bear on crutches for a few weeks.
These bolts are inserted using intra-operative fluoroscopy and so require special training to insert, In the USA over 20,000 have been implanted with very high levels of patient satisfaction. More information can be found on this device here
This is what the bolts look like in real life in an x ray of a lady who had both of her sacroiliac joints fused for severe back pain. The surgery took about 30 minutes per side and she stayed in hospital 2 nights. Sometimes patients are placed on crutches for a few weeks to protect the weightbearing especially if the bone quality is not great.