Direct Anterior Approach for Hip Arthroplasty

Gregory K. Deirmengian, MD

William J. Hozack, MD

Dr. Deirmengian or an immediate family member is a member of a speakers’ bureau or has made paid presentations on behalf of Angiotech; serves as a paid consultant to or is an employee of Synthes, Angiotech, Zimmer, and Biomet; and has stock or stock options held in CD Diagnostics. Dr. Hozack or an immediate family member has received royalties from Stryker; serves as a paid consultant to or is an employee of Stryker; has received research or institutional support from Stryker; and serves as a board member, owner, officer, or committee member of The Hip Society.

INTRODUCTION

Total hip arthroplasty (THA) is one of the most successful surgical procedures in modern medicine. The procedure reliably relieves pain, restores function, and improves quality of life for most patients with debilitating hip arthritis. Successful achievement of the technical goals of THA requires surgical exposure of the acetabulum and proximal femur. This may be achieved through one of many well-described and commonly used approaches, each with its own advantages and disadvantages.

The long-term success of THA has been well established. Recent attention has been placed on early outcomes and the achievement of a rapid recovery. It appears that this goal may be attained through the integration of a combination of tactics, including patient education and preconditioning, anesthesia, surgical technique, aggressive postoperative physical therapy, and modern approaches to pain management.¹^,²^,³ The literature has placed considerable focus on elements of surgical technique that may influence the speed of recovery.

The most common approaches for THA include the posterior approach and the modified Hardinge (also called direct lateral) approaches. Attempts to minimize the invasiveness of these approaches have involved limiting the size of the skin incision and the extent of the corresponding deep dissection. Several studies have shown, however, that the size of the skin incision does not influence the speed of recovery.⁴ Furthermore, in inexperienced hands, small-incision surgery may lead to inadequate exposure, resulting in technical errors that may compromise the long-term outcome of the procedure.⁵

The direct anterior approach is a modification of the classic Smith Petersen approach and was first described for use in THA by Judet in 1947.⁶ Recently, the direct anterior approach has become popular for THA because of its unique potential for achieving the goals of the procedure while minimizing the splitting or detaching of muscles or tendons. Careful technique leads to minimization of soft-tissue trauma, which is known to affect rapid recovery. As with any approach to the hip, proper exposure is the most important factor in achieving proper component sizing and positioning. This chapter describes our method of achieving appropriate exposure and minimizing soft-tissue trauma with the direct anterior approach.

PATIENT SELECTION

Contraindications

Proficiency in THA through a direct anterior approach is like any other surgical procedure in that it involves a learning curve.⁷ Careful patient selection is critical during the time when the surgeon is becoming comfortable with the approach. As with any other hip approach, the direct anterior approach is more challenging in patients who are obese or muscular or in whom the femoral neck is short and varus (Figure 1). In addition, more complicated cases, such as those involving dysplasia, deformity, or prior surgery, should be avoided until the surgeon and other members of the surgical team achieve proficiency in the approach.

Obesity that involves excessive soft-tissue folds that override the area of the skin incision is a relative contraindication to the direct anterior approach. Although such soft-tissue folds may be retracted during surgery, they raise the risk of wound healing complications in the postoperative period. Also, although the direct anterior approach is extensile, cases that require more extensive femoral exposure, such as those involving femoral deformity or femoral revision arthroplasty, are likely better served with an alternative approach.

PREOPERATIVE IMAGING

Radiographic evaluation is standard for all hip approaches. AP radiographs of the pelvis and hip and a lateral radiograph of the hip are obtained and reviewed.
The radiographs also are used for templating with standard overlay templates or with a digital templating system. Preoperative prediction of the appropriate component sizes may provide important clues in the intraoperative setting. For example, if the femoral trial broach is several sizes smaller than the size predicted with templating, then the surgeon may have inadequately lateralized the broach in preparing the femur.

FIGURE 1 AP radiograph of the hip demonstrates a short, varus femoral neck. This anatomic pattern is associated with a difficult reconstruction.

FIGURE 2 Photograph shows the room setup using a standard operating table for the direct anterior approach for total hip arthroplasty. The gel bump, 30° of table flexion, and the distal arm board on the nonsurgical side of the table facilitate the extension and adduction of the surgical lower extremity necessary for femoral exposure.

VIDEO 57.1 Direct Anterior Approach for Total Hip Arthroplasty. Gregory K. Deirmengian, MD; William J. Hozack, MD (23 min)

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Video 57.1

PROCEDURE

Room Setup/Patient Positioning

Many surgeons who perform this procedure use a specialized table that facilitates the positioning of the surgical extremity in a manner that optimizes proximal femoral exposure. Our preference is to perform the procedure with the patient in the supine position on a standard table. We achieve the flexion, adduction, and external rotation of the surgical hip that is required for adequate exposure to ensure safe and effective femoral preparation as follows: Hip flexion is achieved by placing a gel bump under the patient’s pelvis and by flexing the table approximately 30° at the time of femoral exposure (Figure 2). During patient setup, the gel bump is placed just proximal to the break of the operating table to allow for extension of the hip as the operating table is flexed. Adduction is achieved with the use of an arm board attached to the distal aspect of the nonsurgical side of the table. At the time of femoral exposure, the nonsurgical leg is placed on the arm board, opening space on the table for placement of the surgical extremity in an adducted position. External rotation is achieved by gentle manipulation by an assistant. We typically perform the procedure with six team members: the surgeon and first assistant on the operating side of the table, a second assistant on the nonsurgical side of the table, a
surgical technician at the foot of the bed, the anesthesia team member at the head of the table, and a circulating nurse.

Using a standard table for the direct anterior approach has several advantages and avoids some of the disadvantages associated with specialized tables. Standard tables are familiar to all operating room staff members, are used for most other orthopaedic procedures, and are associated with time and cost savings. Using a standard table allows faster patient setup, draping, and room turnover. It also allows more controlled manipulation of the extremity during femoral exposure and preparation. As a result, the increased risk of ankle and trochanteric fracture that has been associated with the use of specialized tables is minimized. Lastly, with a standard table, the surgical extremity is draped free, allowing better assessment of motion, stability, and leg length.

Special Instruments/Equipment/Implants

The direct anterior approach does not dictate or limit the components used for reconstruction, but it is of utmost importance that the chosen system has the specially designed curved, angled, or offset instrumentation available for acetabular and femoral preparation and component implantation (Figure 3). The use of standard instrumentation may lead to inadequate or inappropriate access to the femur and acetabulum, which may result in technical errors and/or undue soft-tissue damage. In addition, certain femoral implant design features, such as a reduced lateral shoulder and contoured distal tip, facilitate femoral reconstruction with the direct anterior approach.

FIGURE 3 Photographs depict the specialized angled and offset acetabular (A) and femoral (B) instruments that are essential for the direct anterior approach for total hip arthroplasty.

Surgical Technique: Total Hip Arthroplasty

Incision Planning and Superficial Dissection

Careful planning of the skin incision is one of the most critical aspects of the direct anterior approach. The superior, inferior, and medial borders of the anterior superior iliac spine (ASIS) are palpated and marked. The superior aspect of the incision starts 2 to 3 cm distal and 2 to 3 cm posterior to the inferomedial aspect of the ASIS. The incision is continued distally with a gentle posterior angle (Figure 4, A). In slender individuals, the borders of the tensor fascia lata (TFL) are palpable. The incision should be located in the midaspect of the TFL, following its course from proximal to distal. The incision length is typically 8 to 10 cm, but it is critical that the surgeon err on the side of enlarging the incision when necessary to improve the exposure, relax the soft tissues, and avoid undue soft-tissue injury. The skin and subcutaneous tissue are incised, and subcutaneous bleeders are carefully cauterized. Below the subcutaneous tissue, a thin fascia layer is encountered and incised (Figure 4, B). Underneath the fascia lies a thin layer of fat that is bluntly swept to expose the TFL. Careful planning of the incision of the thin fascia that encases the TFL is critical. Typically, the midaspect of the TFL muscle can be visualized through the thin fascia. Laterally, the fascia becomes thicker, obscuring visualization of the muscle. Medially, a fat stripe often is visible deep to the fascia at the medial border of the TFL. Lastly, small vessels often perforate the thin fascia at the midaspect of the TFL; the number, pattern, and location of these vessels vary. After these combined landmarks are used to define the anatomy, the thin fascia is sharply incised at the midaspect of the TFL in line with the skin incision. Care is taken to avoid damaging the underlying muscle with the scalpel. Next, the medial border of the incised fascia is dissected free of the TFL muscle, and this path is followed until the medial border of the muscle is encountered. The stripe of fat within the Smith Petersen interval is visualized when the medial border of the TFL is encountered.

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