This procedure is one of the many shelf operations. The shelf enlarges the acetabulum by grafting bone over the joint capsule. The joint capsule under the graft undergoes metaplasia to fibrocartilage. As the coverage is fibrocartilage, the shelf procedures are considered as salvage operations. Shelves are easily combined with other procedures. For example, if coverage or congruity is inadequate with a Chiari, Salter, or Pemberton procedure, consider adding shelf to improve coverage.
Slotted acetabular augmentation is indicated if the acetabular deficiency is severe or if nonspherical congruity is present. Other factors that make a shelf attractive include excessive scarring; bilateral augmentation, as both sides can be corrected in one operative session; the need for combined procedures; and to provide containment in Perthes disease.
When indicated, hyaline cartilage moving procedures such as the Salter or Pemberton osteotomy are preferred. Excessive laterization is best managed by the Chiari procedure (unless bilateral).
From a standing radiography of the pelvis, measure the CE angle and draw in a CE angle of 40°. Measure the needed width of the augmentation. Compare the standing radiograph with another taken in abduction in internal rotation. A difference in reduction indicates that the hip is unstable and a cast will be necessary.
Technique of Slotted Acetabular Augmentation
Anatomy Note that the reflected head of the rectus takes origin at the superior margin of the acetabulum.
Approach Place a towel under the pelvis to elevate the hip. Prep and drape the leg free. Through a bikini incision, expose the iliac crest. Identify the sartorius rectus interval. Incise the fascia over the sartorius and dissect through the interval to the hip joint without exposing the lateral femoral cutaneous nerve. Divide the apophysis or sharply divide the origin of the abductors from the iliac crest. Strip the abductor origin from the anterolateral side of the ilium to expose the hip capsule.
Elevate tendon Identify the tendon of the reflected head of the rectus. Divide it anteriorly, and sharply elevate it from the underlying joint capsule while preserving its posterior attachments.
Create a slot in the ilium just at the lateral acetabular margin about 1 cm deep and 5 mm wide. Extend it as far anterior and posterior as needed to provide required coverage.
Graft Harvest abundant graft from the ilium.
Place graft Place cancellous graft into the slot and over the capsule laterally as determined to create a CE angle of about 40°.
Secure graft Secure the graft by resuturing the reflected head over the graft. Reattach the abductors. Place the additional graft under the abductors to create a thick augmentation. The graft should be congruous with the acetabulum. Close the wound and apply a spica cast if the hip is unstable.
If the hip is unstable, immobilize in a cast for about 6 weeks. Nonweight-bearing crutching is continued until the graft has consolidated—usually an additional 6 weeks. Full activity is allowed at 6 months.
Unilateral augmentation Note the thick augmentation.
Bilateral augmentation Bilateral procedures may be performed concurrently.