Mini Lateral Approach Total Hip Arthroplasty: The Anterolateral Approach (Modified Hardinge)

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Chapter Synopsis

This chapter describes the technique for minimally invasive lateral approach total hip arthroplasty. The technique described is the modified Hardinge surgical approach, performed with the patient in the supine position.

Important Points:

1

Slowly reduce the size of the incision as comfort with the technique grows.
2

Do not compromise the ability to place components properly because of incision size.

Clinical/Surgical Pearls:

1

Consider injury to soft tissues; minimize with releases as needed.
2

A starter reamer to prepare the femur can be used in oscillating mode to prevent soft tissue damage.
3

Offset broaches allow shorter proximal incision without injuring soft tissues with a rasp.

Clinical/Surgical Pitfalls:

1

Do not make the incision too small and compromise the clinical outcome.
2

The rasp and reamer should not traumatize the skin at insertion.

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INTRODUCTION

Historically, total hip arthroplasty was done through a 20- to 30-cm incision. Improvements in technique and instruments have allowed a decrease in the size of the incision without increased soft tissue injury. In patients with normal body habitus, hip replacement surgery can be done through a variety of approaches with 8- to 10-cm incisions. The goals of surgery should not change: expeditious performance of the procedure, minimal soft tissue injury, and proper component placement. The issue of small-incision surgery yielding a faster recovery is debatable. However, consumer demand for small incisions is unquestionable. This chapter addresses how this can be achieved with the mini-lateral modified Hardinge approach.

When talking of minimally invasive surgery, tissue damage at all levels must be considered. Incision length is only one criterion by which to judge surgery as minimally invasive. In fact, a small incision is not always the least traumatic option. Too small of an incision can lead to extensive trauma to the skin and soft tissues from retraction or surgical instruments.

In all surgery what goes on beneath the skin obviously is crucial. Minimizing soft tissue damage, bone damage, and blood loss is important. The emphasis should be on gentle exposure that minimizes overall muscle, bone, and skin trauma. Although the modified Hardinge approach involves splitting the abductor, this may be less traumatic than aggressively retracting the muscle. Some indirect exposures do not require removal of any muscle insertions, but these indirect exposures can severely bludgeon the muscle and have the potential to create maximal trauma (invasion). The patient does not benefit from minimal incision size when damage of the muscle or bone occurs by having inadequate releases and exposure. In summation, small-incision surgery does not always equate minimally invasive surgery.

Choosing the proper implant also is important. The selected system must facilitate component positioning through a small incision. It must have proven clinically success yet be extremely simple and reproducible. Preparing the bone and implanting the prosthesis should be done with minimal trauma. A proximally coated tapered titanium-alloy prosthesis inserted after minimal disruption of the bone is reproducible and minimally invasive. Reducing reaming minimizes blood loss, disruption of endosteal blood supply, and fat embolism. Proximal fixation is used to reduce stress-shielding bone loss associated with distal fixation stems.

Properly positioning the components also is crucial, and this principle cannot be sacrificed to minimize the incision. Serious complications, such as nerve injury, leg-length discrepancy, dislocation, and fracture must be avoided. No matter the approach, the critical anatomic landmarks must be well visualized. Adequate exposure of the calcar is necessary to achieve implant lateralization and prevent and recognize fractures when inserting the stem. Special retractors designed to minimize trauma and maximize visibility are available. Retractors with a built-in light source can be helpful.

Although the benefits of small-incision surgery are questionable, no doubt exists that new techniques can provide equal visualization and equal outcomes. Some studies have shown that these techniques allow faster surgery and reduced postoperative pain. Reducing surgical time is beneficial to minimize blood loss, contamination leading to infection, and phlebitis. Small-incision surgery should not significantly increase the time needed to perform arthroplasty.

INDICATIONS AND CONTRAINDICATIONS

The small-incision modified Hardinge approach is indicated for routine primary total hip arthroplasty in patients with a normal or slightly elevated body mass index. It is contraindicated in obese patients, although incision size can safely be reduced somewhat in these patients as well. In general, small incisions should not be used in the presence of significant stiffness, deformity, or prior surgery with retained implants or arthrofibrosis. Small incisions are not indicated for revision surgery. In the revision setting, more extensive femoral releases are required to get adequate exposure.

SURGICAL TECHNIQUE

General or spinal anesthesia is applicable and should be based on the patient’s medical status and the anesthesiologist’s familiarity with a particular method. However, when appropriate, spinal anesthesia is preferred. Spinal anesthesia provides excellent muscular relaxation, results in less blood loss, and is associated with a reduced risk of pulmonary embolism.

After the anesthetic has been administered, the patient is placed in the supine position. A 5-cm thick pad is centered under the ischium and the patient is moved to the edge of the table. This allows soft tissues in the incision area to drop posteriorly out of the surgical field. The hip is the prepped and draped in a sterile fashion. A foot rest placed preoperatively allows the leg to be positioned at 45 degrees hip flexion and 90 degrees knee flexion. The bony landmarks are palpated and labeled. Marks are placed to identify the tip of the greater trochanter and the direction of the femur.

With the hip in flexion the incision is centered on the trochanter, slightly anterior (1 cm), and in line with the long axis of the femur. The incision is taken though skin and down to the fascia ( Fig. 22-1 ). The incision initially can be made shorter until the greater trochanter location is verified, and then it can be expanded. The incision ideally is equal distance proximally and distally from the center of the greater trochanter. Hemostasis should be addressed at this point with coagulation of all bleeding vessels. Deep fascia is exposed using blunt dissection with a lap sponge or a Cobb elevator. A limited amount of dissection allows the identification of this layer at closure and ensures better repair. However, excessive dissection should be avoided to eliminate dead space and devascularization of subcutaneous adipose tissue. By freeing the fascia from the overlying fat layer, the tissues are freer to move with retraction. A Hibbs retractor is placed anteriorly to hold the tissues away from the field.

The tensor fascia is then split with a knife. The cut is made in line with the femur and is centered immediately adjacent to the center point of the greater trochanter. The Hibbs retractor is placed under this fascia layer anteriorly.

The trochanteric bursa is split using a combination of blunt dissection and sharp dissection with a pair of mayo scissors. This allows full visualization of the gluteus medius as it inserts into the greater trochanter. The vastus lateralis also will be visible at the inferior aspect of the medius insertion. A blunt split is created in the gluteus medius with a finger at the junction of the anterior third and posterior two thirds of the muscle. A rough rule of thumb: if a clock is superimposed over the trochanter with 12 o’clock being anterior, for a right hip the split is at the 10 o’clock position and for a left hip it is at the 2 o’clock position. A blunt Hohman retractor is then introduced around the posterior aspect of the femoral neck to retract the posterior two thirds of the muscle ( Fig. 22-2 ). The hook end of the Hibbs retractor is inserted around the anterior third of the muscle and is used to pull the gluteus medius anteriorly. With Bovie cauterization, the split is taken down to the greater trochanter. Immediately behind the split lies the tendon of the gluteus minimus. With a long-handled knife, the capsule is split posterior to this tendon. A sponge is packed into the proximal wound to control bleeding. Attention is then turned to the vastus region. A split is made on the vastus ridge distally in line with the femur with a Bovie cautery. A blunt Hohman retractor is placed anteriorly around the femur. The surgeon uses a Hibbs retractor in the left hand to retract the anterior tissues. The two splits are connected by elevating and releasing the anterior gluteus medius and anterior hip capsule with Bovie cautery ( Fig. 22-3 ). A small cuff of tissue of the gluteus medius tendon is left on the greater trochanter to reattach the muscle. Staying on bone, the gluteus medius, gluteus minimus, and the anterior capsule are all removed as a single flap. To perform the release the leg is slowly adducted into the figure-4 position. This keeps the tissues under tension as they are released and allows gentle, less traumatic elevation. Before hip dislocation the patient receives a single dose of 1000 U intravenous heparin. When the full release has been performed, the hip will dislocate with a gentle pull with a bone hook. If further force is needed, be certain that the release is complete and osteophytes are not blocking dislocation.