Equipment

You will need lead and a C-arm for this case. No loupes unless you need them to place dermal stitches and run a monofilament absorbable over the skin (not subcuticular). 

Indications

Patients presenting with low back pain, sometimes with a component radiating down the leg, that is not referable to the spine or hip. Patients often present with persistent back pain despite lumbar or lumbosacral fusion or hip arthroplasty. 

On physical exam, there is marked tenderness to palpation about the SI joint.

Current guidelines require a positive provocative test, followed by 2 to 3 diagnostic SIJ injections with at least 75% repeated improvement after the injection.

Compression test

The test is performed by placing the patient in a side-lying position, with the affected side up, and applying a downward pressure on the lateral ilium.

Gaenslen maneuver

The patient begins positioned in supine with the painful leg resting on the edge of the treatment table. The examiner sagittally flexes the non-symptomatic hip, while the knee also flexed (up to 90 degrees). The patient should hold the non-tested (asymptomatic) leg with both arms while the therapist stabilizes the pelvis and applies passive pressure to the leg being tested (symptomatic) to hold it in a hyperextended position. A downward force is applied to the lower leg (symptomatic side) putting it into hyperextension at the hip, while a flexion-based counterforce is applied to the flexed leg pushing it in the cephalad direction causing torque to the pelvis.

Faber's maneuver

Faber stands for flexion, abduction and external rotation, which are the primary anatomical movements associated with this test. The patient lies supine then the affected leg is crossed over the unaffected knee while the examiner stabilizes the patient at the unaffected hip. The examiner applies gentle pressure to the inside of the patient's affected knee, bringing it towards the exam table. If pain, tightness or inability to move the leg is created with this motion, the test is positive

Instrumentation

As of July 2024, Dr. Gerszten uses the Siros 3D printed lateral sacroiliac joint fusion instrumentation. This is represented by Stryker at the Presbyterian Hospital. 

Medications

Preoperative antibiotic prophylaxis, usually with Ancef, only. 

Monitoring

SSEPs only. 

Room Setup

Bumpy Jackson table with a face rest. The brackets for the arm boards should go as high as possible. 

C-arm is placed on the side opposite the pathology. The screen is at the foot of the bed while the machine is at the patient's side. 

Positioning

Pad the iliac crests before flipping the patient prone. Place blue towels against the skin before taping the patient to the bed. The upper tape goes around the lower rib cage. The lower tape goes obliquely around the hips, with the tape on the side of the pathology being lower. 

Put the patient in a significant amount of reverse Trendelenberg. 

 Fluoroscopic Views

First, you want to get your outlet view. Start with an AP shot of the lumbar spine and center the spinous process between the pedicles. Then, wag the image intensifier rostrally to look at the S1 endplate edge-on. The goal is a crisp, clean S1 endplate. Ask the C-arm tech to make note of the C-arm settings; you will return to this view several times throughout the case. 

Next, get the inlet view by wagging the C-arm in the opposite direction, caudally. The goal is a crisp, clean pelvic brim. The inlet view is useful for making sure you haven't gone into the bowel. On this view, nothing should be ventral to the pelvic brim. Again, have the tech record the C-arm settings.

Finally, get your lateral view. For a true lateral view, line up the S1 endplate and pedicles. 

Marking

Place a radiopaque instrument against the patient's side and, on the lateral shot, localize the expected locations of the first and last screws. Mark an incision between the projected location of the first and last screws. It is a short incision.

Draping

Four blue towels in a square followed by a down sheet and Ioban. Last, apply a thyroid drape with the long end towards anesthesia. Follow this with a C-armor. 

Localization

Go to a lateral shot and again localize the expected locations of the first and last screws against the sacrum. Use the large needle holder. 

Procedure

 Infiltrate the incision with 0.5% lidocaine with epinephrine 1:200,000. 

Incision

Incise the skin with a 15 blade and carry through the dermis, subcutaneous fat, and muscle fascia with the Bovie. 

Approach

Under lateral fluoroscopy place the short K-wire against the sacrum at the planned location of the first screw, the one closest to the sacral endplate. Once it's in position, use a mallet to gently tap the tip into the bone. 

Switch to the outlet view and move the trajectory until it's parallel with the floor. Use the hand drill to grip the K-wire and advance to the lateral aspect of the S1 pedicle (blue line). Be aware of the location of the S1 foramen (red dotted circle). 

Switch to the inlet view and verify that the K-wire isn't in the bowel. 

Pass the first dilator over the K-wire until it hits the bone of the sacrum. Note that there is a small ruler at the back end of the dilator that gives the difference in length between the K-wire and dilator and can be used to estimate the expected length of screw. 

Successively dilate the tract then place the working channel. Remove the dilators but leave the K-wire in place. 

Screw the K-wire extension onto the back of the K-wire to lengthen the wire. Then, pass the cannulated drill bit over the wire and drill to the lateral border of the S1 pedicle. 

Remove the drill, leaving the K-wire in place. Ask the scrub tech to harvest the bone chips from the drill bit and pack into the graft (red square in picture below). Screw length is estimated from the x-ray shots and the ruler on the back of the dilator. Dr. Gerszten always uses 11.5 mm screw width. 

Place the cannulated screw over the K-wire and advance until the graft bisects the sacroiliac joint. The middle part of the screw, which is unthreaded, should overlie the joint. 

Once the screw is placed, switch to an inlet view to finally verify that nothing is in the bowel. 

Place the next two screws in the same way, being sure to respect the lateral border of the S1 and S2 neuroforamina. Note that, on the lateral projection, all three screws are not in a straight line. Instead, they describe something of a triangle. 

Closure

Irrigate three big bulbs full of antibiotic irrigation through the working channel before removing it. Leave the K-wire in place.

Infiltrate the soft tissue with 0.5% bupivacaine. Place the smallest dilator over the K-wire, withdraw the K-wire, and inject bupivacaine down the bore of the dilator. 

Close the deep dermal layer with 0 Polysorb braided absorbable suture. The fascia is usually not accessible through such a small incision. 

Follow this with a layer of 2-0 Polysorb braided absorbable suture.

Close skin with a simple running 4-0 Biosyn absorbable monofilament suture. 

Dress the wound with Mastisol, Steri-strips, and a small Primapore dressing on top. 

Postop

Floor admission with PT evaluation the next morning. Patients are given a crutch and instructions for "touch down weight bearing" on the side of surgery. This is where they are not allowed to bear full weight on that side but are allowed to touch the foot to the floor. Most of their weight should be supported on the crutch. 

Dr. Gerszten is okay with one day of Toradol 15 mg q6 hours while the patient is admitted. 

Discharge home the following day with follow up in 2 weeks for a wound check, no imaging.