Review Question - QID 3515

Long screws placed into the posterior superior or posterior inferior quadrant may pass into sciatic notch and endanger the sciatic nerve and superior gluteal vessels. This is particularly a risk in revision surgery when the acetabular component may be placed in a high hip center position, as the sciatic nerve is at increased risk when placing transacetabular screws posteriorly.

Meldrum et al evaluated the quadrant system used to guide screw placement in primary cadaveric uncemented total hip surgery in the high hip center, jumbo component, and 3 designs of reinforcement rings. Of all the acetabular revision scenarios tested, the high hip center showed increase risk of neurovascular injury in the center and anterior portions of the posterior superior quadrant. All of the other implants met the standard, non-revision scenario quadrant recommendations.

Wasielewski et al performed an anatomical and radiographic study to determine the safest zones in the acetabulum for the transacetabular placement of screws during uncemented acetabular arthroplasty. They found that the posterior superior and posterior inferior acetabular quadrants are relatively safe for the transacetabular placement of screws. They also determined that the anterior superior and anterior inferior quandrants should be avoided whenever possible, because screws placed improperly in these quadrants may endanger the external iliac artery and vein, as well as the obturator nerve, artery, and vein.

Illustration A demonstrates the four quadrants of the acetabulum relevant to transacetabular screw placement.