PERIACETABULAR OSTEOTOMY

The goal of periacetabular osteotomy is to reorient the acetabulum (hip socket) in order to minimize contact pressures on the hip joint as well as to help contain the femoral head and avoid an unstable joint.

 

1.This patient's pelvis radiograph (left) demonstrates hip dysplasia and is compared to a normal pelvis radiograph (right). The hip dysplasia is more advanced on the right side where the acetabular labrum has been damaged and actually been converted to bone (arrow). The roof of the acetabulum is sloped upward leading to increased pressure within the hip and an increased tendency for the head of the femur to be unstable within the hip joint. This is termed hip subluxation. The presence of increased contact pressures and hip instability leads to hip arthritis in many patients with hip dysplasia.

2.The acetabular index is a measurement of a line formed parallel to the weightbearing zone and the line connecting the base of both hip sockets. In this case it measures 34 degrees. The normal measurement is approximately 6 degrees. A second measurement used in the evaluation of hip dysplasia is called the Center-Edge angle (CE angle). It is measured by drawing a line vertically through the center of the femoral head and a second line from the center of the femoral head to the edge of the hip socket. The angle between these two lines is the Center-Edge angle. In this case, it measures 11 degrees. The normal value for the CE angle is greater than 20 degrees.

3.These are specialized MRI images taken from a procedure called MRI arthrography where a specialized material is injected into the hip joint and an MRI is obtained. These show the damage to the acetabular labrum as well as demonstrating the minimal coverage of the femoral head.

4.In this patient, we recommended a periacetabular osteotomy. In this photograph, the muscular interval between the sartorius (SA) muscle and the tensor fasciae latae (TFL) is utilized. The sartorius muscle originates from the anterior superior iliac spine (ASIS).

5.A special angled bone cutting tool (osteotome) is used to cut the ischium bone behind the hip joint. The image on the right is an intraoperative live radiograph which shows the position of this osteotome.

6.After the cut on the ischium bone, the pubis bone is cut with a chisel (shown on this radiograph). Next a cut is performed on the ilium bone and this is connected to the partial cut of the ischium bone. The fragment containing the hip socket is then completely separated from the pelvis. A pin shown on the surgical photograph on the right is used to position the hip socket in an optimal configuration using intraoperative radiographs.

7.Once the optimal position is achieved the fragment containing the hip socket (arrow) is held in place with smooth wires from the top of the ilium bone.

8.Bone graft obtained during the bone cuts is the used to bridge the triangular space created by the configuration. This bone graft remodels over time to form a sturdy bone bridge across the cut bone.

9.This is the final radiograph demonstrating the correction of the deformity and the position of the hip screws used to stabilize the cut bone fragment which contains the hip socket.