Posterior approach to the acetabulum

Introduction

Indications

• Fractures of the posterior lip of the acetabulum.
• Fractures of the posterior column.
• Fractures of the posterior lip and posterior column.
• Simple transverse fractures (patient prone).

Advantage

• Exposure of the posterior wall of the acetabulum and its posterior column.
• Less blood loss.

Disadvantage

• Approach does not allow access to the anterior column.

Position of patient

Lateral position

• Used for fractures of the posterior lip and/or posterior column.
• Skeletal traction can be used by placing a skeletal pin transversely through the lower end of the femur, ensure that the knee is placed in full flexion to reduce the risk of a traction injury to the sciatic nerve.

Prone position

• Used for transverse fractures, as it facilitates reduction of transverse fractures by preventing the natural tendency for the femoral head to move medially.
• Place a skeletal pin transversely through the lower end of the femur with the knee flexed to reduce the risk of a traction injury to the sciatic nerve.

Landmarks and incision

Landmark

• Greater trochanter on the outer aspect of the thigh.

Incision

• Longitudinal incision centered on the greater trochanter, extending from just below the iliac crest to 10 cm below the tip of the greater trochanter.

Internervous plane

No true internervous plane in this approach.

Superficial dissection

• Deepen the incision through subcutaneous fat.
• Incise the fascia lata in the line of the skin incision in the lower half of the wound.
• Extend this incision superiorly along the anterior border of the gluteus maximus muscles (split in the line of its fibers is not significantly denervated because it receives its nerve supply well proximal to the split).
• Retract the split edges of the fascia to reveal the piriformis muscle and the short external rotators of the hip.
• Internally rotate the leg to put the short external rotators and the piriformis on the stretch and detach these muscles after tagging as they insert into the femur.
• The posterior capsule of the hip joint is now exposed.

Deep dissection

• Posterior lip fractures can be visualized at this stage.
• For more exposure of the posterior column, perform an osteotomy of the greater trochanter and displace this piece of bone, with its attached muscles (gluteal muscles attach to it superiorly and the vastus lateralis attaches to it inferiorly), anterior to the femur.
• Trochanteric fragment can be reattached easily with screws during closure.

Dangers

Sciatic nerve

• Minimize the chance of injury by using proper gentle retraction and releasing the short external rotators posteriorly to protect the sciatic nerve from traction.
• Flex knee to prevent injury if skeletal traction is applied.

Inferior gluteal artery

• Leaves pelvis beneath piriformis.
• If the artery is transected, it will retract into the pelvis; turn the patient into the supine position, open the abdomen, and tie off the internal iliac artery via a retroperitoneal approach.

Superior gluteal artery and nerve

• Leaves the pelvis above the piriformis and enters the deep surface of the gluteus medius.
• This tethering limits upward retraction of the gluteus medius and blocks access to the iliac crest.

How to enlarge the approach

• Proximally, the exposure cannot be usefully extended.
• Distally, the skin incision can be extended to the level of the knee by splitting the vastus lateralis or elevating it from the lateral intermuscular septum to allow exposure of the lateral surface of the entire shaft of the femur.

Figures