Training and Education for the Direct Anterior Approach

Jose A. Rodriguez

Tim P. Lovell

John F. Sloboda

Joseph T. Moskal

Key Learning Points

When selecting patients, favor thin patients with a flexible hip, a narrow pelvis, and a lower native offset, at least early on. Avoid those with muscular thighs, morbid obesity, minimal hip motion, a wide pelvis, a low neck-shaft angle, and/or coxa vara.
Regarding proactive hemostasis, there are predictable sites of blood loss that benefit from preemptive cauterization, and a focused plan of hemostasis promotes better visualization and surgical efficiency.
Supine acetabular reaming can be disorienting and is mechanically different than in posterior or lateral approaches. Awareness of varied mechanical forces during reaming avoids potential errors.
Adequate femoral exposure for safe, reproducible femoral preparation is markedly dissimilar from other approaches. A stepwise release sequence is critical and helps prevent proximal femoral injury. Accurate broaching is facilitated by understanding femoral spatial anatomy.
Understanding the capacities and limitations of the C-arm enables accuracy of fluoroscopy and generally helps prevent errors.

Introduction

Never practice struggle.

—Terry Laughlin, swim coach and founder of Total Immersion Swimming.

This chapter describes the process of educating residents, fellows, and orthopaedic surgeons on the direct anterior approach (DAA) for total hip arthroplasty (THA). Facets unique to DAA instruction are elucidated. A stepwise program has been developed to provide a repeatable method for learning and performing the DAA with an emphasis on the nuances of each step to maximize accuracy and minimize complications.

Many studies report relatively longer operative times, increased blood loss, and iatrogenic femur fractures as the frequently encountered complications while learning DAA THA. The number of cases before proficiency is achieved with DAA THA ranges from 50 to 100.¹^,²^,³^,⁴^,⁵^,⁶^,⁷^,⁸ It is imperative for novice surgeons to visit experienced surgeons; practice cadaver dissection, preferably with fluoroscopy and ideally an experienced DAA surgeon; learn the relevant anatomy; understand the equipment needed; and master the soft tissue releases in order to minimize risk during the learning phase. It is very helpful, after appropriate training as described earlier, to have a DAA surgeon-mentor perform the first five cases with the surgeon if the surgeon is not fellowship trained. Attempting DAA THA after abbreviated training (eg, a weekend cadaver course) is insufficient and will lead to complications and poor outcomes. There are no shortcuts.

We have organized DAA THA learning into 12 key and critical steps. This reproducible method has facilitated the teaching of DAA THA to residents, fellows, and practicing orthopaedic surgeons while ensuring patient safety. We have also identified factors unique to teaching DAA THA (eg, the use of fluoroscopy) and present these factors to help the DAA instructor “better instruct.” Features of the learning curve are discussed as well.

This 12-step method has been refined and validated at national cadaver-based courses aimed at teaching DAA THA and is part of the core curriculum of the annual Direct Anterior Approach Hip Course offered by the International Masters Anterior Course (IMACx).

Targeting Your Specific Audience

The technique for teaching a surgical procedure will vary depending on the learner and the environment. The traditional teaching of a residency program allows the opportunity for preparation and repetition as well as an entire rotation time period in order to synthesize information. In addition, for a young learner, the more formal hierarchical student-teacher relationship can add additional motivation as the resident is working through the basics of surgical technique while learning a specific series of steps that comprise the surgical procedure.

Teaching of a surgical fellow can presuppose the attainment of basic surgical techniques and allows a more dedicated focus on the specific steps of the procedure, the decision-making processes as to when that is successfully completed and when to begin the next step, and the subtleties of surgical execution and flow. The issue of flow is particularly important in that the surgeon can perceive nascent problems at a subconscious level because the “feeling” of flow is interrupted. This is often an issue of exposure or position that can be easily overlooked by the learning surgeon and can be readily remedied by the teaching surgeon who perceives this break in flow. As with a resident, having a prolonged period of time during which the information can be absorbed, processed, and synthesized provides a powerful environment for learning. Part of the role of the teacher is to provide
access to the information including anatomic references; video-based surgical references; and, most importantly, direct feedback to the learner on performance.

There are particular challenges to teaching an established surgeon by means of a cadaver-based symposium. The most concerning issue is the limited time available to transmit the information. The more successful teaching programs incorporate recommended reading before the symposium, give very specific stepwise instructions on the procedure, and are followed by an opportunity for a reverse surgical visitation by the teacher to the established surgeon learner. There is a wide variety of surgical acumen present among surgeons who attend symposia to learn a new procedure. Similarly, there will be variability in the retention of material that is presented. The short-term nature of the symposium experience creates the challenge of the teacher knowing that the learner has understood what is taught. Therein lies the value in the reverse surgeon visitation—to cement in the thought processes that were transmitted and add subtleties in surgical execution.

The 12-Step Method for Teaching (and Learning) the Direct Anterior Approach

The 12-step method is presented, listing each critical step during the DAA THA procedure. Tips for avoiding common complications during the learning curve are provided. This serves as a methodological framework for teaching DAA THA with a stepwise progression once proficiency is achieved at a particular step along the pathway to performing the DAA.

Step 1: Preoperative Planning—Patient Selection and Templating

When initially starting to learn the procedure, it is important to select easier patients. Patient characteristics that facilitate femoral exposure include thin patients with a flexible hip, a narrow pelvis, and lower native offset. These characteristics increase the femoral working space and make formal exposure much easier (Figure 7.1A). Patients with muscular thighs, morbid obesity, minimal hip motion, a wide pelvis, significant deformity, or coxa vara or coxa breva can make the femoral exposure more challenging (Figure 7.1B). Deep hips or patients with acetabular protrusio are not recommended during the learning curve. Abdominal obesity with a pannus that would rest on the planned skin incision is a relative contraindication for the DAA. Templating the THA procedure with standardized radiographs helps improve the accuracy and equipment planning needs for the case. This should be done routinely as a way to perform the operation before reaching the operating room. Preoperative templating can also help prevent placing the stem undersized and in varus.

FIGURE 7.1 A, A generous (oval shape) femoral broaching space. B, A tighter (circle shape) femoral broaching space.

Step 2: Preparation, Drape, and Skin Incision

The patient is positioned supine on the operating table, and the operative limb is draped to allow easy access to the anterior superior iliac spine (ASIS), iliac crest, and the posterior border of the greater trochanter (GT). This also allows planned access to the proximal third of the femur, if not the full length of the femoral shaft. If a standard operating room table is used, the patient’s perineum should be positioned at the hinge of the bed so that when the leg portion of the bed is lowered, hip extension is achieved. On a standard table, it is also helpful to place an arm board on the contralateral side of the foot of the bed to allow abduction of the nonoperative leg, thereby allowing more adduction of the operative leg during femoral exposure. The incision starts proximally 3 cm lateral and 2 cm distal (variable depending on the groin crease) to the ASIS and continues for 10 cm distally, aiming for the fibular head and over the bulk of the tensor fascia lata (TFL; Figure 7.2). It is generally better to make the incision slightly more lateral than too medial. Moving the incision lateral to the true Smith-Peterson interval helps to decrease the risk of injury to
the main trunk of the lateral femoral cutaneous nerve. It is important to avoid making the proximal part of the incision extend into the hip flexion crease because this may increase the risk of proximal wound breakdown.

FIGURE 7.2 DAA THA incision (black line) versus Smith-Peterson incision (white line) left hip.

Step 3: Fascia Over the Tensor Fascia Lata—Identification of the Portal

The fascia encasing the TFL muscle is then identified (Figure 7.3A and B). The TFL has a spectrum of thickness and color. In most patients, it is a fairly thin, bluish translucent layer with muscle fibers easily identifiable underneath it, whereas in other patients it appears thick and glossy white superficially with a thinner more translucent fascial layer below that. Generally, the fascia over the TFL becomes whiter in color relative to the surrounding tissue going lateral and posterior as it coalesces into the iliotibial band and fascia overlying the gluteus medius. There are usually two to three perforating vessels that are helpful for guiding placement of the TFL fasciotomy, which is made 1 to 2 cm anterior to these perforators and in line with the skin incision (ie, if one is encountering perforators, the fasciotomy is too posterior). It is important to make sure the correct interval is entered. Going medial to the sartorius puts the femoral neurovascular bundle at risk and makes it impossible to obtain femoral exposure. Going posterior or lateral to the TFL is a Watson-Jones approach and endangers the superior gluteal nerve innervation to the TFL.

FIGURE 7.3 TFL fascia release and mobilization (left hip).

A, The this fascial layer encasing the TFL muscle is then identified and incised over the muscle belly of TFL anterior to perforating vessels and in line with skin incision. B, An Allis clamp is then attached to the medial flap of TFL fascia and provides countertraction as the surgeon’s finger bluntly sweeps the muscle fiber of TFL off its medial fascia.

Step 4: Muscle Management—Creating Space Between the Tensor Fascia Lata and the Rectus Femoris

An Allis clamp is then attached to the medial flap of TFL fascia and provides countertraction as the surgeon’s finger bluntly sweeps the muscle fibers of the TFL off of its medial fascia. It is important not to dive too deeply with this maneuver in the central and distal part of the wound because this will risk injury to the ascending branch lateral femoral circumflex vessels. An index finger is then placed proximally in the wound through the posterior TFL fascia and into the interval between the gluteus minimus and the superior hip capsule. This allows the surgeon to feel the correct interval to place a cobra retractor into the space between the gluteus minimus and the superior hip capsule. This space proximal to the femoral neck between the capsule and the gluteus minimus can be tight or scarred into place and requires the surgeon to ensure the minimus is not split after placing the retractor. Flexing or abducting the hip can also help relax the soft tissues enough to place the retractor.

Attention is then turned to the mid-distal aspect of the incision where a Hibbs retractor is used to retract the rectus muscle belly medially and another Hibbs retracts the TFL laterally.

Two layers of fascia are then encountered. The initial thin layer is that of the TFL. Deep to that is another much thicker fascia running from the undersurface of the rectus femoris into the fascia lata. Between these two layers of fascia lie the ascending branches of the lateral femoral circumflex vessels (Figure 7.4A and B). These vessels are typically encased in a thin membrane surrounded by fat. Spreading a tonsil parallel to the vessels or perpendicular to the incision is helpful to identify them. These vessels are the major source of blood loss early in the learning curve if they are not controlled; careful cauterization addresses this. The vessel ends should be checked during the case and again just before wound closure because it is not uncommon for some residual bleeding to occur given the large size of the vessels.

FIGURE 7.4 A and B, Location and cauterization of the ascending branches of the lateral femoral circumflex vessels (left hip). Arrows indicate direction of ascending branches of lateral femoral circumflex vessels. This is also the direction in which to spread the tonsil when dissecting through the membrane surrounding the vessels.

The position of the anterior circumflex vessels relative to the skin incision is a helpful guide to assess whether the length of the skin incision is appropriate, too proximal, or too distal. The anterior circumflex vessels should lie in the central portion of the incision. Often, slight distal skin extension is needed for proper DAA exposure.

Step 5: Capsule Management—Femoral Neck Exposure

The pericapsular fat is then identified, and a cobra retractor is placed adjacent to the femoral neck inferiorly. A Bovie or Cobb elevator is gently used to elevate the indirect head of the rectus femoris off the capsule to allow a double-bent Hohmann retractor to slide over the anterior rim of the acetabulum just anterior to the capsulolabral interval. Extreme caution should be taken to keep the tip of this retractor directly on bone to avoid femoral nerve and arterial injury (especially if a sharp retractor is used). It is not uncommon for the capsulolabral interval to be densely scarred, requiring cautery release of this space to safely place the anterior column retractor; elevation of the lower extremity can help relax this space. This retractor is placed perpendicular to the inguinal ligament to avoid neurovascular injury.

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