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The direct anterior approach leaves the abductor muscles intact and has the potential to minimize the risk of gluteal insufficiency.
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Access to the cup is usually possible through a minimal approach comparable to that in primary total hip arthroplasty.
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Proximal extension of the approach in the interval along the iliac crest is easy.
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A partial release of the tensor fasciae latae muscle’s origin gives straight access to the femur for endofemoral procedures.
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Lateral access to the femur can be achieved by a dorsolateral extension of the incision or a second lateral incision dorsal to the lateral vastus muscle.
The main advantage of the direct anterior approach (DAA) is the preservation of muscle structures. This is especially true for the gluteal abductor muscle, which can be kept intact during primary total hip arthroplasty (THA). Whereas revision THA in general tends to be more destructive, the DAA and its extension have the potential to provide the advantage of gluteal muscle preservation also in revision cases.
If the approach is extended proximally along the iliac crest or distally along the lateral femur, the term “direct anterior” certainly refers to the fact that the portion of the approach in the area of the hip joint itself exploits the interval between the tensor fasciae latae (TFL) and the rectus femoris. Nevertheless, the main advantage of this portal, which is keeping the gluteal muscles intact, can still be achieved.
In my experience, the direct anterior portal to the hip seems ideal for cup revisions. Even in severe cases of acetabular destruction, an extension of the approach is hardly necessary to perform a cemented or uncemented reconstruction.
Straight access to the proximal femur can be achieved with this approach if an endofemoral revision is planned. This requires a partial release of the origin of the TFL from the ilium.
If access to the femoral diaphysis is necessary, the nerve supply does not allow anterior access to the femur. The incision has to be extended laterally or a second incision has to be made. Yet gluteal muscle can still be kept intact.
INDICATIONS AND CONTRAINDICATIONS
Indications for revision hip arthroplasty are septic or aseptic loosening of one or both components of a hip arthroplasty. For revision THA the DAA allows for keeping the incision small if only the cup has to be revised or in cases of stem revision; the femoral preparation can be performed strictly endofemorally from the proximal direction. Gluteal muscles can be preserved whether the approach can be limited to the original interval between the TFL and the rectus or it must be extended.
If preservation of the gluteal muscles is desired, the DAA and its extension are the approaches of choice. For endofemoral revision other than detachment of the TFL, hyperextension and sufficient adduction of the operated leg are important. If these cannot be achieved, an alternative operative strategy or a different approach should be considered. As this approach allows for extensions proximally and distally along the femur, it competes with lateral approaches to the hip joint and femur and does not have additional specific contraindications. The availability of specific curved, angulated, or offset instruments is mandatory.
TECHNIQUE
Skin Incision
The placement of the skin incision in the DAA in its minimally invasive version for primary THA is described in earlier chapters of this book. For standard cup revisions, incision and intermuscular preparation can be limited to the same portal.
Although it is recommended to place the skin incision further laterally than in the original Smith-Petersen version, the incision can be easily extended proximally analogously. It will not be placed directly above the iliac crest but will extend the original incision laterally parallel to the iliac crest. Usually it is necessary only to detach the origin of the TFL partially from the ilium. Therefore a proximal extension of the skin incision to the level of the anterior superior iliac spine (ASIS) or slightly proximal to it is sufficient ( Fig. 35-1 ).
Distally the incision can be lengthened anteriorly to the level of the lesser trochanter. If more distal access to the femur is necessary, this has to be achieved laterally. Therefore the skin incision has to be curved down to the lateral femur or lateral access can be achieved through a second lateral incision.
Patient Positioning
As in primary THA, I prefer to place the patient in supine position on the operating table. This position guarantees a stable pelvis and allows for easy leg length measurement. For exposure of the acetabulum with the femoral component in place, it is necessary to have a support for the lower leg (such as a Mayo stand) attached to the table. A table attachment opposite the operated side (such as an arm board) allows for easier hyperabduction of the opposite leg during femoral exposure. Both legs are draped flexibly. This allows for crossing the operated leg under the opposite leg during the surgical exposure of the femur.
Pearls
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A standard operating table can be used, which can be broken at the level of the hip joint in order to hyperextend both legs.
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Bilateral draping allows crossing the operated leg under the opposite leg during femoral exposure.
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An additional support for the lower leg is needed for acetabular exposure with the femoral component in place.
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An additional arm board supports the adducted leg for the femoral preparation.
Portal
The initial portal should be the same as in primary hip arthroplasty. Palpate the ASIS and the greater trochanter ( Fig. 35-2 ). The proximal starting point is found two fingerbreadths lateral and two fingerbreadths distal to the ASIS. Depending on the operative requirements, the incision length has to be chosen. I recommend keeping the incision length small initially and increasing it as needed during the course of the operation
