Anterolateral Approach to the Hip
The anterolateral approach is the approach most commonly used for total joint replacements. It combines an excellent exposure of the acetabulum with safety during reaming of the femoral shaft. Popularized by WatsonJones (D. Hirsh, personal communication, 1981) and modified by Charnley,4 Harris,5 Hardinge, and Müller,6 it exploits the intermuscular plane between the tensor fasciae latae and the gluteus medius. It also involves partial or complete detachment of some or all of the abductor mechanism so that the hip can be adducted during reaming of the femoral shaft and so that the acetabulum can be more fully exposed (Fig. 8-25).
The abductor mechanism can be released either by a trochanteric osteotomy7 or by detaching part of the anterior part of the gluteus medius and the whole gluteus minimus from the trochanter.6 The two methods seem to offer different approaches, but they are actually variations on a theme. The differences should not obscure the fundamental fact that all anterolateral approaches exploit the same intermuscular plane, between the tensor fasciae latae and the gluteus medius.
The uses of the anterolateral approach include the following:
1. Total hip replacement6,7
2. Hemiarthroplasty
3. Open reduction and internal fixation of femoral neck fractures22
4. Synovial biopsy of the hip
5. Biopsy of the femoral neck
Position of the Patient
Place the patient supine on the operating table, so close to the edge that the buttock of the affected side hangs over (Fig. 8-26). Tilt the table away from you as the patient lies flat. Both maneuvers allow the buttock skin and fat to fall posteriorly, away from the operative plane, and lift the skin incision clear of the table, making it easier to drape the patient. You must take the table tilt into account when you insert the acetabular portion of a total joint replacement because the guides used to position the acetabular prosthesis usually take the ground as their reference plane.
Drape the patient so that the limb can be moved freely during surgery.
Landmarks and Incision
Landmarks
The anterior superior iliac spine is subcutaneous. It is easy to palpate in all but the most obese patients, who have a thick layer of adipose tissue covering it. To palpate it, bring your thumbs up from beneath the bony protuberance.
The greater trochanter is a large mass of bone that projects up and back from the junction of the shaft of the femur and its neck (Fig. 8-27).
The shaft of the femur can be felt as a resistance through the massive vastus lateralis on the lateral side of the thigh (see Fig. 8-49).
Figure 8-25 The route of the anterolateral approach to the hip joint.
Figure 8-26 Position of the patient on the operating table for the anterolateral approach to the hip. Bring the greater trochanter to the edge of the table, and allow the buttocks, skin, and fat to fall posteriorly, away from the operative plane.
Figure 8-27 Incision for the anterolateral approach to the hip.
The vastus lateralis ridge, a rough line that marks the fusion site of the greater trochanter to the lateral surface of the shaft of the femur, is easiest to palpate from distal to proximal. It is not palpable in obese patients.
Incision
Flex the leg about 30 degrees and adduct it so that it is lying across the opposite knee both to bring the trochanter into greater relief and to move the tensor fasciae latae anteriorly. Make an 8- to 15-cm straight longitudinal incision centered on the tip of the greater trochanter. The length of the incision relates to the size and obesity of the patient as well as the surgeon’s experience. The incision crosses the posterior third of the trochanter before running down the shaft of the femur (see Fig. 8-27).
Internervous Plane
There is no true internervous plane for this approach, since the gluteus medius and the tensor fasciae latae have a common nerve supply, the superior gluteal nerve. However, the superior gluteal nerve enters the tensor fasciae latae very close to its origin at the iliac crest; therefore, the nerve remains intact as long as the plane between the gluteus medius and the tensor fasciae latae is not developed up to the origins of both muscles from the ilium (see Fig. 8-25).
Superficial Surgical Dissection
Incise the fat in the line of the skin incision to reach the deep fascia of the thigh. Using a sponge, gently push back subcutaneous fat off the fascia lata until you can reach the fascia at the posterior margin of the greater trochanter. Incise the fascia lata at this point, entering the bursa that underlies it (Fig. 8-28). Now, divide the fascia lata in the line of its fibers superiorly, heading proximally and anteriorly in the direction of the anterior superior iliac spine. Finally, complete the fascial incision by extending the cut distally and slightly anteriorly to expose the underlying vastus lateralis muscle. Elevate this flap anteriorly by getting your assistant to retract it forward, using a tissue-holding forceps. Now, detach the few fibers of gluteus medius that arise from the deep surface of this fascial flap and locate the interval between the tensor fasciae latae (which is being lifted anteriorly by the assistant) and the gluteus medius. This is best done by blunt dissection using your fingers. A series of vessels cross the interval between the tensor fasciae latae and the gluteus medius. These act as a guide to the interval, but require ligation (Fig. 8-29).
Next, place a right-angled retractor deep to the gluteus medius and minimus, and retract these muscles proximally and laterally away from the superior margin of the joint capsule that covers the femoral neck (Fig. 830).
Figure 8-28 Incise the fascia lata posterior to the tensor fasciae latae.
Figure 8-29 Retract the fascia lata and the tensor fasciae latae muscle, which it envelopes, anteriorly, revealing the gluteus medius and a series of vessels that cross the interval between the tensor fasciae latae and the gluteus medius.
Figure 8-30 Retract the gluteus medius posteriorly and the tensor fasciae latae anteriorly, uncovering the fatty layer directly over the joint capsule.
Fully externally rotate the hip to put the capsule on stretch. Identify the origin of the vastus lateralis at the vastus lateralis ridge. Above it is the anterior aspect of the joint capsule, at the junction of the femoral neck and shaft. Bluntly dissect up the anterior part of the joint capsule, lifting off the fat pad that covers it. The fat pad can reduce postoperative scarring and adhesions and should be preserved even though it intrudes into the operative field (Fig. 8-31). The safest technique is to use a swab.
Deep Surgical Dissection
Deep surgical dissection consists in detaching part or all of the abductor mechanism and then dissecting up the femoral neck superficial to the capsule of the joint until a suitable retractor can be placed over the anterior lip of the acetabulum.
Two techniques improve exposure of the acetabulum by neutralizing the abductor mechanism, allowing the femur to fall posteriorly. They also permit adduction of the leg for safe femoral reaming and accurate positioning of prosthetic stems within the femoral shaft. The technique chosen depends on the prosthesis to be used.
1. Trochanteric osteotomy. Performing a trochanteric osteotomy allows complete mobilization of the gluteus medius and minimus muscles, which in turn allows excellent exposure of the shaft of the femur during femoral reaming. Palpate the vastus lateralis ridge on the lateral border of the femur, from distal to proximal. Osteotomize the trochanter, using either an oscillating saw or a Gigli saw, and reflect it upward with the attached gluteus medius and minimus muscles. The base of the osteotomy should be at the base of the vastus lateralis ridge. The upper end of the osteotomy may be either intracapsular or extracapsular; the thickness of the osteotomized portion of bone varies considerably, depending on the prosthesis you intend to use. Alternatively, detach the trochanter using two cuts at right angles to one another. This will leave the trochanter looking like the roof of a Swiss chalet. This technique maximizes the bone-to-bone contact surface area and, because of its shape, also is inherently more stable after fixation than a straight osteotomy.
Reflect the osteotomized trochanter upward. To free it completely, release some soft tissues (including the tendon of the piriformis muscle) from its posterior aspect (Figs. 8-32 and 8-33).
2. Partial detachment of the abductor mechanism. Place a stay suture in the anterior portion of the gluteus medius just above its insertion into the greater trochanter. Cut the insertion of this anterior portion off the trochanter. Identify the thick white tendon of the gluteus minimus as it inserts onto the anterior aspect of the trochanter and incise it. The exact amount of the gluteus medius that must be detached varies considerably from case to case (Fig. 8-34). In thin, nonmuscular people, you may even be able to preserve the whole of the gluteus medius attachment.
Figure 8-31 Bluntly dissect the fat pad off the anterior portion of the joint capsule to expose it and the rectus femoris tendon.
Figure 8-32 Osteotomize the greater trochanter.
Figure 8-33 Reflect the osteotomized portion of the trochanter superiorly (with the attached gluteus medius) to reveal the joint capsule.
Figure 8-34 The joint capsule may also be exposed by partial resection of the gluteus medius tendon from the anterior portion of the trochanter.
Figure 8-35 Reflect the head of the rectus femoris from the anterior portion of the joint capsule.
Bluntly dissect up the anterior surface of the hip joint capsule in line with the femoral neck and head. Detach the reflected head of the rectus femoris from the joint capsule to expose the anterior rim of the acetabulum (Fig. 8-35, and inset). (This plane is easier to open up if the leg is partly flexed, since the rectus femoris remains relaxed. Flexing the leg also keeps the femoral nerves and vessels off the stretch and farther from the operative field.) Elevate part of the psoas tendon from the capsule. Because both the rectus femoris and the psoas may insert into the capsule, the plane between muscle and capsule is often difficult to establish.
Place a Hohmann retractor on the anterior rim of the acetabulum. Make certain that the dissection and the insertion of retractors remain beneath the rectus femoris and iliopsoas, because the neurovascular bundle lies anterior to the psoas. If you cannot develop a plane between the psoas and the capsule, incise the capsule and insert a retractor around the femoral head so that you can see the joint better.
Incise the anterior capsule of the hip joint with a longitudinal incision. Develop this into a T-shaped incision by cutting the attachment of the capsule to the acetabulum as far around as you can reach. Now incise the capsule transversely at the base of the neck to convert the T-shaped incision into an H-shaped one (Fig. 8-36, and inset). Dislocate the hip by externally rotating it after you have performed an adequate capsulotomy (Fig. 8-37).
Dangers
Nerves
The femoral nerve is the most laterally placed structure in the neurovascular bundle in the femoral triangle, thus the structure closest to the operative field and most at risk. The most common problem is compression neurapraxia, caused by overexuberant medial retraction of the anterior covering structures of the hip joint. Less frequently, the nerve is directly injured by retractors placed in the substance of the iliopsoas (see Figs. 8-47 and 8-48).
Vessels
The femoral artery and vein may be damaged by incorrectly placed acetabular retractors that penetrate the iliopsoas, piercing the vessels as they lie on the surface of the muscle. You can avoid this complication by making sure that the tip of the retractor is placed firmly on bone, with no intervening tissue. The anterior retractor should be placed in the 1-o’clock position for the right hip and in the 11-o’clock position for the left hip. Finding the correct plane between the rectus femoris and the anterior part of the hip joint capsule is easier if the limb is in about 30 degrees of flexion. Alternatively avoid placing any retractors over the acetabular lip until after a capsulotomy has been performed and the femoral head excised when the exact position of the acetabular margin is obvious and retractors can be inserted under direct vision.
Figure 8-36 Incise the anterior joint capsule to reveal the femoral head and neck and the acetabular rim. If further proximal exposure is needed, incise the fascia lata proximally toward the iliac crest and along the iliac crest anteriorly. To facilitate dislocation of the hip, incise the tight fascia lata and the fibers of the gluteus maximus (inset).
The profunda femoris artery lies on the psoas muscle, deep to the femoral artery. The artery may branch off from the femoral artery just distal to the inguinal ligament and this anatomical variant lies very close to the anterior lip of the acetabulum. The artery may be damaged by poorly placed retractors.
Be aware that damage to either of these arteries may not be obvious at the time of surgery because any bleeding that may occur may be into the retroperitoneal space and not into the surgical wound.
Fractures of the Femoral Shaft
Femoral shafts have been known to fracture while hips are being dislocated. For that reason, it is critical that you do an adequate capsular release before attempting dislocation. To dislocate the joint, lever the femoral head out of the acetabulum with a skid (such as a Watson-Jones) while your assistant gently externally rotates the limb. Your assistant has a considerable lever arm during this procedure—if rotating the leg too forcibly, a spiral fracture of the femur can result.
In severe protrusion of the hip, you may have to osteotomize the rim of the acetabulum, which often has an osteophyte, to achieve dislocation.
If you cannot dislocate the hip without resorting to extreme force, it is safer to perform a double osteotomy of the femoral neck, excising a 1-cm portion of it, then remove the femoral head (which is lying free) with a corkscrew.
Fractures of the femoral shaft also can occur when the limb is placed in full adduction and external rotation for reaming of this femoral shaft. In order for the operator to gain a good enough view of the cut surface of the femur, the femoral shaft must be adducted. If the incision in the fascia lata has been placed too far anteriorly, then the fascia lata will resist adduction and enthusiastic assistants may cause femoral shaft fracture. This is the reason why the fascia lata should be incised initially at the posterior border of the greater trochanter. If the fascia lata gets in your way when attempting to adduct the leg, it is safest to incise it along the lines of fibers of gluteus maximus (see Fig. 8-36).
Figure 8-37 To expose the acetabulum, di
