Choosing the Exposure

Ashton H. Goldman

Michael J. Taunton

Key Concepts

Choice of operative exposure in revision total hip arthroplasty (THA) has a strong influence on how well and how efficiently the rest of the procedure can be performed.
Surgeon experience and preference plays an important role in operative approach choice.
However, specific revision scenarios are better suited to one exposure than another.
Each exposure has specific advantages and disadvantages in terms of how extensile the exposure is and also the risks and potential complications associated with that exposure.
Some exposures allow conversion to a more extensile approach more easily than others.

Sterile Instruments and Implants

Instruments

Routine hip retractors
- Specialized hip retractors for direct anterior approach (DAA).
A full set of revision THA instruments, including:
- Cup explant system
- Femoral component explant system instruments and tools
- High-speed burrs (short and long pencil-tip burrs, 6.5-mm round burr)
- Osteotomes (straight, curved, flexible)
- Cement removal instruments if cement is present
- Ultrasonic cement removal device if available and if cement is present in femur
- Curettes
- Cobb elevators
- Drill, drill bits, threaded drill guides, depth gauge
In the event of a trochanteric osteotomy:
- Cabling device/wire passers (also for prophylactic use during femoral component revision)
- Oscillating saw

Implants

Highly porous revision acetabular components
Various acetabular liner options: standard, dual mobility, constrained
Acetabular screws
Porous metal augments
Acetabular cages
Revision femoral components (with trial stems)
Femoral heads (with trial heads)
Cerclage cables and wires
Allograft bone chips

Positioning

Lateral decubitus with hip positioners or supine based on approach.
The operative limb should be draped out and sterilely prepared from the iliac crest to the distal thigh.

Surgical Approach

The authors typically prefer a posterolateral approach, although an anterolateral, a direct anterior, or a transtrochanteric approach may be used. This discussion on approach will be the focus of this chapter.
A trochanteric osteotomy can facilitate femoral component removal and/or relieve tension when exposure of the ilium could risk traction injury to the superior gluteal nerve.

Preoperative Planning

Record Review

Obtaining the outside operative report and implant stickers is essential.

Laboratory Workup

Assess for infection preoperatively with inflammatory markers and fluoroscopically guided hip aspiration as indicated.

Imaging

Preoperative imaging is imperative and includes the following:
- Anteroposterior (AP) pelvic radiograph
- AP hip radiograph
- Cross-table lateral hip radiograph
Additional views in cases of extreme bone loss or fracture may include the following:
- Judet radiographs (obturator and iliac oblique views)
- Thin-slice computed tomography (CT) scan with 3-dimensional reconstruction
The above-mentioned imaging should be used to determine:
- The extent and location of acetabular bone loss, including the presence of a pelvic discontinuity (separation of the ilium from the ischiopubic segment).
- The extent and location of femoral bone loss and to determine if there is enough diaphysis to obtain a stable fixation of a revision femoral stem.

Exposure Options: Approaches

Direct Anterior Approach

Advantages

Some recent studies have demonstrated improved early perioperative functional recovery in the primary setting.
The supine position allows for improved use of intraoperative fluoroscopy and assessment of leg lengths postoperatively.
The posterior capsule and external rotators are left intact leading to improved posterior stability.
The abductors are not cut leading to reduced chance of permanent muscle deficiency or denervation.

Disadvantages

In revision surgery, the need for extensile exposure usually outweighs the advantages of a tissue sparing approach.
- There are methods to make the DAA more extensile, and it may be suitable in certain revision situations.
The neurovascular bundle to the vastus lateralis is at risk when making femoral osteotomies.
Risk of denervation or neuropraxia of the lateral femoral cutaneous nerve and the femoral neurovascular bundle from overretraction anteriorly.

Suitable Situations

Head and liner exchange may be performed through the DAA because a limited revision through this approach may decrease the risk of instability.
Revision of a loose femoral stem to a diaphyseal engaging stem is possible through this approach by surgeons very experienced with the approach, but there are some caveats:
- If the tensor fascia lata muscle is left attached to the iliac rim, exposure to the femoral canal with a straight reamer is very difficult and sometimes impossible.
- The anterior 1 cm of the tensor fascia lata origin may be taken down off the iliac rim to allow for access to the longitudinal axis of the femoral diaphysis.
- Others have proposed an iliac rim osteotomy.
Removal of a well-fixed femoral stem through an osteotomy.
- The neurovascular bundle to the vastus lateralis, which runs just distal to the lesser trochanter, must be managed while performing osteotomies.
- The author would typically extend the approach superficially and split the fascia distally. The vastus lateralis is lifted off of the femur from the linea aspera. A Bennet retractor is placed to retract the vastus lateralis.
- The distal aspect of the anterior limb of an extended trochanteric osteotomy is made with an oscillating saw. Then attention is turned superior to the vastus lateralis and the anterior limb is created proximally.
- The osteotomies are connected with a narrow osteotome using care not to disrupt the neurovascular supply to the vastus lateralis. This “episiotomy” can be widened with a wide osteotome without creating a formal extended trochanteric osteotomy (ETO) (Figure 22.1).
- Combined with a pencil tip burr and flexible osteotomes, even some well-fixed stems may be removed through this technique.
- However, if the stem still cannot be removed, the distal limb may be made and the wide osteotomes may be used to crack the posterior cortex to complete the ETO.
- The external rotators should be left attached to the medial limb, and the osteotomized fragment can be translated anterior-medially for access to the femur.
Acetabular revision
- If the tensor fascia lata muscle is released 1 to 2 cm off of the anterior iliac rim and the rectus femoris is taken off the anterior inferior iliac spine, there is considerably increased exposure to the acetabulum (Figure 22.2).
- Exposure to the posterior column is limited.
- Surgeons should be very familiar with revisions through traditional approaches and familiar with performing complex primaries and simpler revisions through DAA before attempting complex acetabular revisions through the DAA.

Anterolateral Approach

Advantages

The anterolateral, Harding, Watson-Jones, or other variations of a laterally based abductor splitting approach have been employed.
The anterolateral approach (ALA) has a demonstrated long history of a very low hip instability rate.
The ALA has versatility, from small to very extensile exposure.
The posterior capsule and external rotators are left intact leading to low risk of posterior hip instability.

Figure 22.1 ▪ A, AP femur radiograph demonstrating septic loosening of an uncemented hydroxyapatite-coated stem. A clinical photograph (B) demonstrates that an extensile direct anterior approach has been carried out distally. The vastus lateralis has been translated medially, while preserving its neurovascular bundle. An anterior osteotomy has been made distal and proximal and completed underneath the vastus to aid in removal of the stem. Once the stem is removed, the osteotomy can be reapproximated with a cable and the femur elevated for preparation for a diaphyseal engaging stem. A specialized table with a bed attachment hook is seen aiding in the elevation of the femur (C).

Disadvantages

The abductors are cut leading to an increased chance of permanent muscle deficiency or denervation.

Risk of injury to the superior gluteal neurovascular bundle when extending the abductor split proximally.

Typically, if the abductors are split more than 2 cm above the acetabular rim, or 5 cm or more above the tip of the greater trochanter, the surgeon should watch out for the bundle.

Figure 22.2 ▪ A, Clinical photograph of the direct anterior approach with exposure of the acetabulum. The posterior retractor is directed toward the sciatic notch, and the anterior retractor is on the anterior wall below the psoas tendon to protect the femoral neurovascular bundle. The component was removed with minimal bone loss (B).

Figure 22.3 ▪ Clinical photographs of the extensile exposure that is obtained through the anterolateral approach. Here a trabecular metal cup has been placed, with a cage that has been overlaid and fixed to the ilium superiorly.

Risk for denervation or neuropraxia of the femoral neurovascular bundle from over-retraction anteriorly.
Although some surgeons are able to ably manage issues with the posterior column through the ALA, most find it more difficult to directly manage posterior column fractures and defects through the ALA and would prefer the posterolateral approach (PLA) in this setting.

Suitable Situations

Many surgeons who use the ALA as their primary approach of choice would scarcely use another approach for revision unless for certain situations.
A complete view of the rim may be obtained without osteotomy, and there is a favorable angle achieved for screw placement in the anterior and posterior columns (Figure 22.3).
- As mentioned previously, care must be taken to avoid injury to the superior gluteal neurovascular bundle if the exposure is extended proximally on the ilium.
One particular situation in which we typically utilize an ALA is if we are performing a head and liner exchange or other revision where we are planning on retaining an underanteverted acetabular component where we are concerned that a PLA would lead to instability and force an acetabular component revision.
- An overly anteverted acetabular component that is planned to be retained may be an example of a contraindication for ALA.
Femoral revision may be carried out through the ALA favorably as well.
- Access to the femur allows for a reasonable starting position for femoral diaphyseal preparation especially with larger amounts of anterior femoral bow.
- An anterior-based extended greater trochanteric osteotomy (Wagner style osteotomy) goes through a similar muscular interval as the ALA but keeps muscle attached to bone.
- However, if an osteotomy is needed after an ALA is completed, that anterior osteotomized fragment is stripped of muscle attachment.