Authors of section

Authors

Derek Donegan, Michael Huo, Michael Leslie

Executive editor

Michael Baumgaertner

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Revision of cup to multihole pressfit cup with augments

1. Principles

Cup fixation stability is critical to ensure durable fixation.

One of the goals is to minimize fracture progression and comminution.

For further information about standard techniques for ORIF in native acetabular fractures, please refer to the acetabulum section of the AOSR.

Cup stability

Cup stability is determined by visual and manual examination.

Intraoperative X-ray should be utilized.

Removal of the cup should be considered if there is any question about stability.

2. Approach and exposure

The surgical management of these periprosthetic acetabular fractures involves using the standard surgical approaches for total hip arthroplasty, such as:

These approaches can be performed with the patient in lateral or supine positioning.

The surgeon should have full visualization of both the anterior and the posterior walls/columns of the acetabulum. This is critical to fully assess the extent of the fracture lines and patterns.

This would also allow for the most safe and efficient removal of the failed cup.

Acetabular exposure

Take care to protect the neurovascular structures that are at risk, such as the sciatic nerve, and those structures in the greater sciatic notch.

Acetabular neurovascular structures

3. Cup removal

Liner removal

The cup liner is removed prior to cup removal.

P270 Revision of cup to multihole pressfit cup with augments

Acetabular component removal

The acetabular component is removed. Details on how to remove an acetabular cup, and any associated screws, are described in the basic technique for acetabular cup removal.

P270 Revision of cup to multihole pressfit cup with augments
Note: Take care to maintain the bone stock and to avoid additional fractures or fracture propagation and displacement.

4. Fracture assessment

Assess the location, stability, and extension of the fracture(s) by visual inspection. If necessary, intraoperative imaging may also be used.

The most common fracture pattern involves the posterior wall of the acetabulum. If the posterior column is not involved, this type of fracture is managed with revision to a multi-hole porous cup.

Multi-hole porous cup

The fracture patterns may be difficult to classify. However, the treatment principles are identical to the management of any acetabular fracture.

It is important to maintain and to reestablish column stability and acetabular containment of the cup.

5. Cup revision and fracture fixation

Restoration of segmental defect(s) in the acetabulum can be performed using bone grafts, metal augments, or in combination.

Metal augments

Implant sizing

The surgeon should select the cup size that would provide optimal contact with the anterior and the posterior columns.

Acetabular cup sizing

Pitfall: Cup oversizing

The new cup should have stable and sufficient contact with the anterior and the posterior columns. Oversizing of the cup could create fracture extension and displacement without gaining additional cup press-fit stability.

If a significant increase in cup size seems to be indicated (more than one cup size larger than pre-planned), the need of ORIF or augment should be suspected.

Option 1: Metal augment fixation

Restore the acetabulum integrity using metal augment prior to new cup insertion according to the manufacturer's specifications.

Metal augment fixation

Option 2: Segmental cortical bone graft augmentation

If the surgeon chooses to use bone graft rather than metal augment, the graft may be either obtained from the resected femoral head in primary total hip arthroplasty, or banked allograft inventory.

Segmental cortical bone graft augmentation

The size and geometry of the graft, autograft or allograft, should be modified to the proper dimensions to augment the defect.

Size and geometry of the graft

New cup insertion

The new multi-hole cup is inserted into the acetabulum against the augment.

New cup insertion

Insert the new cup following the recommended position (inclination) and orientation (anteversion) guidelines.

The accepted "safe zone" is:

  • cup inclination 40° to 55° (a)
  • cup anteversion 20° to 40° (b)
Recommended cup position and orientation

Screw fixation

The cup is secured with multiple screws that than engage both the anterior and posterior columns, on each side of the fracture.

Screw fixation

Safe zones for screw implantation

Avoid placing screws into the antero-superior and antero-inferior zones when possible, and towards the medial wall of the acetabulum.

When required, critical evaluation of drill and screw depth is required. Consider oscillation of drill bit to prevent neurovascular injuries.

Safe zones for screw implantation

Interface stabilization

The interface between the metal augment and the new cup is stabilized (unitized) with the use of bone cement.

Interface stabilization

Cement unitization would not be necessary when the structural graft is used.

Structural graft stabilization

New liner insertion

The new liner is implanted into the shell using implant system specific instruments.

New liner insertion

Continue with hip replacement as preoperatively planned.

Multihole pressfit cup with metal augment

6. Aftercare following revision to a multihole pressfit cup

Physiotherapy guidelines

Routine physiotherapy protocols for elective total hip arthroplasty is followed.

Early mobilization with protective weight bearing (50%) is recommended for 6 to 8 weeks until sufficient fracture healing.

Hip dislocation precautions must be given to the patient.

Imaging

Postoperative radiographs should be made at 2 to 3 weeks to determine maintenance of satisfactory cup fixation stability and no fracture progression or displacement.

Follow-up radiographs should be made at 10 to 12 weeks after surgery to determine sufficient cup fixation stability and no further fracture displacement to increase the weight bearing status, and physical activities.

Future follow-up is similar to the routine and standard protocol for total hip arthroplasty.