Ganz periacetabular osteotomy: How to make the osteotomy cuts easier?

Abstract

In 1982, Dr. Reinhold Ganz [1] introduced a new periacetabular osteotomy (PAO) as a therapeutic measure for hip dysplasia. The primary objective of this surgical procedure was the strategic reorientation of the acetabulum to optimize coverage of the femoral head and increase the surface area of the acetabular cartilage over the femoral head, all while preserving the structural integrity of the posterior column and maintaining the natural pelvic shape. The complexity of the Ganz periacetabular osteotomy presents a formidable learning curve, owing to the proximity of numerous neurovascular structures to the proposed cuts. Additionally, the surgical approach inherently lacks direct visualization of all osteotomy cuts, necessitating surgeons to rely on anatomic knowledge and meticulous interpretation of fluoroscopic views. This article endeavors to describe some techniques designed to facilitate and enhance the execution of the osteotomy.

Key concepts: (1)Superior ramus osteotomy: meticulous dissection and strategic use of retractors, such as Crego retractors, help protect obturator neurovascular structure during the superior ramus osteotomy, enabling direct visualization and precise execution of the cut.(2)Ischial osteotomy: fluoroscopic guidance aids in executing the ischial cut, with emphasis on careful consideration of sciatic nerve location, and meticulous completion of the osteotomy to prevent stress fractures into the posterior column.(3)Supra-acetabular osteotomy: creating a burr channel at the brim of the pelvic to facilitate posterior column cut later.(4)Posterior column osteotomy: performing the posterior column osteotomy involves 3 passes with a wider osteotome, regular depth checks, and an additional cut to connect the posterior column with the ischial cut.

Keywords: Ganz periacetabular osteotomy; Hip dysplasia.

Figure 1

Illustration of the position of Crego retractors around superior ramus to protect obturator neurovasculature.

Figure 2

Intra-operative position of Crego retractors. Blue solid arrows indicate Crego retractors. Dashed arrow indicates superior ramus. The Cregos are clearly around the ramus. Patient positioned cranial to the left of the picture.

Figure 3

Osteotome angled at 40° for the superior ramus cut and secondary cut to take out a small wafer to facilitate mobilization later.

Figure 4

Fifty to 55° false profile view to determine cranial-caudal location of the ischial cut.

Figure 5

Ferguson view to determine medial/lateral position of the cut and confirm completion of the ischial osteotomy.

Figure 6

Medial cut should be situated below the tear drop to avoid the inferior acetabulum. Homan retractor at the brim of the pelvis to facilitate insertion of the osteotome and is taken out after correct position of the osteotome is confirmed on fluoroscopy.

Figure 7

Intraoperative fluoroscopy showing 3 passes of the ischial cut. Homan retractor at the brim of the pelvis to facilitate insertion of the osteotome and is taken out after correct position of the osteotome is confirmed on fluoroscopy.

Figure 8

Illustration of orientation of the supra-acetabular cut. Radiolucent Homan retractor about the ischial spine to expose the inner table of the pelvis. Homan retractor #24 on the outer table to protect superior gluteal nerve and artery. Patient positioned cranial to the left of the picture.

Figure 9

Saw bone illustration and intraoperative fluoroscopy showing the location and orientation of posterior column cut. Starting point is 1 cm lateral to the brim and aim to split the posterior column 50/50.

Figure 10

Use finger to gauge the depth of the osteotome into the bone.

Figure 11

Saw bone illustration and intra-operative fluoroscopy showing the position of the fifth cut. The angled osteotome is positioned just distal to the posterior column osteotome.

Figure 12

Angled osteotome directed at the most superolateral corner of posterior column cut. Complete the lateral cortex here first.

Figure 13

Saw bone illustration and intra-operative fluoroscopy showing completion of the posterior column cut.

Figure 14

Ideal position of the acetabular coverage. Aim for AWI of 0.3 and posterior wall at the center of the femoral head.