With the plate  placed on the pelvic bone surface close to the border of the smaller pelvic, the screws are inserted parallel to the joint space, gripping the strong subchondral bone there. Acting as a compression plate with two screws at each side of the joint, the plate  achieves a strong three dimensional fixation of the sacroiliac joint.

Surgical technique.

The patient is placed on an ordinary operating table, possibly tilted about 10 degrees with the actual side facing upwards. The leg should be sterile draped to make flexion and adduction of the hip joint possible during the procedure.
The incision is made  about 1 cm above  and along  the iliac crest and is ended 2-3 cm anterior to the spina iliaca.
The approach goes further by stripping off the iliac muscle from the pelvis down to the sacroiliac joint. By careful dissection the joint is passed using a sharp rasp.
The periost is lifted from the lateral 15 mm of the sacrum up to a length of 3 cm. During this manoeuvre the hip joint should be flexed and adducted to minimize the tension to the iliac muscle and the closely lying nerve bundle.
Gynaecologic retractor gives good insight and for better working space 4 mm long rods are inserted into the sacral bone supporting the retractor.
 

Necessary preparations of the joint are made, cartilage or bone removal, bone-grafting etc (joint reduction facilitated by moving the draped leg).
The plate is placed over the  joint split. The first hole is drilled at the sacral side, parallel to the joint.  A screw suitable in length is inserted only so deep that the ball formed screw head touches the plate. The second hole is drilled diagonally to the first one parallel to the joint. The second screw is inserted. Then the two remaining holes are drilled. Spongious screws are used, usually with a length between 35 and 45 mm. When driving home all the screws the sacroiliac joint will be compressed.