Anterior Approach to Sacroiliac Joint

The anterior approach to sacroiliac joint offers safe, reliable access to that structure and allows anterior plates to be positioned accurately across the joint.

It also permits the exposure of the inner wall of the ala of the ilium, allowing fixation of associated iliac fractures.

The Anterior Approach to Sacroiliac Joint allows greater exposure and control than does the posterior approach, because of the shape of the joint.

Position of the Patient

• Place the patient in a supine position on the operating table, and put a large sandbag under the buttock (The iliac crest should be pushed up toward the surgeon).
• Support the opposite iliac wing with a support attached to the operating table and then tilt the table 20 degrees away, allowing the mobile contents of the pelvis to fall away.

Landmarks and Incision

• Landmarks:
  1. The anterior superior iliac spine.
  2. The anterior third of the iliac crest.
• Incision:
  • Make a long, curved incision over the iliac crest, beginning 7 cm posterior to the anterior superior iliac spine (at about the level of the iliac tubercle).
  • Curve the incision forward until the anterior superior iliac spine is reached.
  • Continue the incision anteriorly and medially along the line of the inguinal ligament for an additional 4 to 5 cm.

Internervous plane

• There is No true internervous plane for the anterior approach to sacroiliac joint.
• The approach consists simply of stripping muscles off the pelvis; because the bone is being approached via its subcutaneous surface, no muscle is denervated.

Superficial dissection

• Deepen the skin incision through the subcutaneous fat.
• Expose the deep fascia overlying the glutei and tensor fasciae latae muscles at the point where it attaches to the outer lip of the iliac crest.
• Next, incise the periosteum of the entire anterior third of the iliac crest and gently strip the muscles off the outer wall of the pelvis to expose about 1 cm of the outer surface below the crest of the ilium.
• Predrill the iliac crest for easy reattachment.
• Using an oscillating saw, transect the wing of the ilium at this level, cutting only the outer cortex and the cancellous bone underneath.
• Next, crack the inner cortex with an osteotome, this allows the anterior superior iliac spine to be detached along with the transected portion of the iliac wing.

Deep dissection

• The iliacus muscle arises from the inner wall of the ilium; detach it by blunt dissection.
• As the dissection is deepened, the detached anterior superior iliac spine, which still is attached to the lateral end of the inguinal ligament, must be mobilized.
• This block of bone and muscle must be moved medially; to accomplish this, divide some fibers of both the tensor fasciae latae and sartorius muscles.
• Remaining strictly in a subperiosteal plane, strip the iliacus muscle off the inner wall of the pelvis to expose the underlying sacroiliac joint.
• The distance is surprisingly short. As the muscle is stripped off, some nutrient vessels will have to be detached from the inner wall of the pelvis.
•  Mobilizing the iliacus muscle off the inside of the pelvis with a large bone block allows the muscles to be reattached securely with screws during closure.

Approach Extension

• The anterior approach to sacroiliac joint may be enlarged into an extended ilioinguinal approach that provides access to the entire anterior column of the acetabulum.

Dangers

The structures at risk during anterior approach to sacroiliac joint include:

• Nerves:
  1. The lateral cutaneous nerve of the thigh.
  2. The sacral Nerve Roots.
• Vessels:
  • Relatively large nutrient vessels often are avulsed from the inner wall of the ilium.

References

• Surgical Exposures in Orthopaedics book – 4th Edition
• Campbel’s Operative Orthopaedics book 12th