Anatomic considerations for posterior approach to the sacroiliac joint

Study Design. This anatomic study describes a new intraosseous, posterior approach to the sacroiliac joint. Objectives. To define a transosseous approach to the sacroiliac joint in which a triangular bony window is raised on the posterosuperior aspect of the ilium that provides improved access to the sacroiliac joint for posterior fusion. Summary of Background Data, A posterior approach to the sacroiliac joint has been widely used for debridement of infectious diseases and for fusion. Most conventional approaches to the sacroiliac joint are interosseous, and there is a relative lack of information on transiliac approaches. Methods. The projection of the sacroiliac joint on the outer table of the ilium and the thickness of the posterior ilium forming part of the sacroiliac joint were determined in 15 cadaveric pelves. A right angle, triangular bony window was raised from the posterior ilium to investigate the suitability of a transiliac approach in performing sacroiliac debridement and arthrodesis. A horizontal reference line 3-3.5 cm in length was drawn between a point 1 cm anterosuperior to the posteroinferior iliac spine and a point 1.5 cm superior to the superior border of the greater sciatic notch. A vertical reference line was extended superiorly for 2-2.5 cm perpendicular to and beginning at the anterior end of the horizontal reference line. The oblique arm of the right triangle was created by joining the superior end of the vertical reference line to the posterior end of the horizontal line. Results. Thirty percent to fifty percent of the articular surface of the iliac bone was removed with this triangular segment of bone, and a corresponding area of the sacral articular surface was visualized directly. It was possible to remove the rest of the articular cartilage with angled curettes in all specimens. Conclusions. This approach facilitates improved access to the sacroiliac joint for debridement and arthrodesis with minimal soft tissue dissection and iliac bone resection.