Managing Intraoperative Complications of the Direct Anterior Approach
In this article, the authors outline techniques for avoiding known intraoperative complications of the DAA, as well as offer tips for treating these complications if they occur.
Tyler D. Goldberg, MD, and Andrea Torres, BS
Direct anterior approach (DAA) total hip arthroplasty (THA) has gained popularity over the last several years. This approach is both intermuscular and internervous, and consequently, its proponents cite advantages such as: [1,2]
- Reduced surgical trauma
- Reduced dislocation rates
- Quicker rehabilitation
- Better implant positions
Critics of the DAA cite the complex learning curve needed to gain proficiency, the risk of perioperative femur fracture, and early femoral loosening as obstacles for adoption of the technique. [3,4]
The purpose of this article is to outline known intraoperative complications of DAA and discuss how to avoid them and how to treat them if they occur.
The DAA Technique in Brief
- With the patient in the supine position and using an orthopedic table to assist with the approach, a scout radiograph of the affected hip is performed.
- Once the patient is draped, an 8-cm skin incision is made over the tensor fascia lata (TFL). The TFL fascia is incised and retracted laterally.
- The rectus femoris (RF) is identified and retracted medially. The reflected head of the RF is incised.
- The fascial floor of the rectus sheath is incised exposing the ascending branch of the lateral circumflex artery (ABLCA). This is ligated and the fat pad overlying the bare area of the anterior hip capsule is excised.
- A capsulotomy is performed and retractors are placed around the femoral neck. A transcervical osteotomy is performed and the femoral head is delivered.
- The acetabulum is exposed and reamed and the acetabular implant placed. Fluoroscopy is used to check implant placement and neck osteotomy length.
- The femur is delivered by sectioning the pubofemoral ligament (PFL) and the ischiofemoral ligament (IFL). The leg is externally rotated and extended for femoral preparation.
- Once broaches, trials, and final implants are placed, the hip is reduced and final fluoroscopic images are obtained to evaluate for leg length, offset, and any complications.
The skin incision typically lies directly over the TFL muscle belly. Placement of the incision here will protect the lateral femoral cutaneous nerve (LFCN) from injury. The skin can receive damage from excessive retraction, causing cell death and subsequent wound breakdown.
Furthermore, migration of the skin incision across the groin crease can lead to painful scarring, delayed wound healing, or infection from the unsanitary glabrous skin of the groin (Figure 1). This can be minimized by extending the incision laterally as it moves proximal and performing meticulous exposure/releases.
Figure 1. Poor wound healing of the left hip.
Lateral Femoral Cutaneous Nerve
Injury to the LFCN is common in DAA. The LFCN is a terminal branch of the lumbar plexus. It exits the pelvis distal to the anterior superior iliac spine (ASIS), runs in the interval between the TFL and sartorius muscles, and has 2 bifurcation patterns. . It is common for the tensor bundles to become severed with the skin incision, leading to numbness in the skin lateral to the skin incision for 6 to 12 months after surgery. Distal numbness in the LFCN distribution has a relatively low incidence. 
Injury to LFCN can best be avoided by utilizing an approach through the fascial sheath of the TFL rather than the direct DAA interval, the Smith-Petersen approach. 
As with any surgical approach to the hip, muscular damage may occur. In particular, the TFL and RF can be torn, or even severed, with aggressive retraction during DAA. The TFL can also be injured during acetabular preparation with straight-handled reamers. Care should be taken to fully relax the patient, completely expose the TFL from its origin on the ilium, and utilize off-set reamers when needed. The reflected head of the RF is routinely incised. The author is unaware of any morbidity this may pose to the patient. Furthermore, injury to the deeper muscles about the hip, such as the gluteus medius and psoas, may cause postoperative heterotopic ossification.
Femoral Neurovascular Bundle
Injury to the femoral neurovascular bundle occurs when the dissection proceeds medial to the sartorius and RF muscles. If this occurs, the 2 muscles are retracted laterally, exposing the femoral triangle. The nerve lies most lateral and is visible as it divides to innervate the quadriceps. This dissection is best avoided by placement of the incision laterally over the belly of the TFL and careful identification of the TFL. The TFL can be identified easily as its fibers run distal and lateral from the pelvis, whereas the sartorius fibers run medially.
The neurovascular bundle is also at risk during placement of the peri-acetabular retractors. The anterior retractor must be placed intracapsular and extra-labral. This space is identified with relaxation of the RF through flexion of the hip. The nerve and even artery can be at risk if the retractor is placed superficially around the acetabulum. An emergent arteriogram must be performed and a revascularization procedure done If arterial injury is suspected (Figures 2a-b).
Figure 2a. Arteriogram showing arterial injury of the external iliac artery passing over the hip.
Figure 2b. Successful revascularization with use of a stent.
The vascular anatomy in DAA is quite predictable, and an understanding of the location of potentially problematic vessels is helpful for preventing unnecessary blood loss.
The largest vessel encountered in DAA is the ABLCA (Figure 3). This vessel exists in its own fascial plane below the RF sheath and the scarpa’s fascia that encloses the precapsular fat. It reliably runs inferior-medial to proximal-lateral directly over the origin of the vastus lateralis (VL). Care needs to be taken to ligate the ABLCA.
Figure 3. Ascending branch of the lateral circumflex in the right hip.
The second major vessel encountered is the medial circumflex artery (MCA). This vessel is encountered in the posterior capsule, proximal to the obturator externus (OE) tendon. Branches of the MCA run along the posterior and lateral femoral neck. Prevention of injury and pretreatment are key to avoid hemorrhage from the MCA. The author places a sponge over the top of the femoral neck during the femoral neck osteotomy, the most common time of injury.
Other vasculature that can be problematic includes the small vessels that lie in the posterior capsular-labral junction. After removal of the labrum, cautery can be performed. The artery of ligamentum teres is sectioned during removal of the femoral head. However, most patients do not have a patent artery in the ligament itself. Instead, the vessel is injured during removal of the pulvinar from the fovea centralis. If injured, it can be coagulated by cautery placed in the anterior inferior aspect of the fovea below the transverse acetabular ligament.
Exposure of the acetabulum is enhanced with incision of the reflected head of the RF and careful placement of retractors in an intracapsular/extralabral position. Tearing of the hip flexors can potentially occur if the anterior retraction is performed too vigorously, causing postoperative groin pain. Furthermore, vigorous retraction can fracture the relatively thin anterior wall of the acetabulum. As stated previously, bleeding can occur from the posterior capsular-labral junction and fovea centralis.
Once exposed, the acetabulum can be reamed utilizing straight or off-set reamers. The typical mistake made by surgeons with less DAA experience is to ream the cup such that it is too vertical and too anteverted. The reamer will also tend to deflect medially in an osteoarthritic hip due to sclerotic bone in the posterior and lateral acetabulum. This can cause penetration of the medial wall and removal of the anterior wall.
The author preferentially reams medially to set the reamer coverage first and then will not let the reamer migrate medially, thus only growing laterally as reamers increase in size. In addition, a small amount of posterior reaming is done to “soften” the posterior wall bone. Prominent posterior soft tissue and the cut neck of the femur will also produce an anterior force on the reamer shaft further increasing risk of anterior wall blow out.
In contrast to the osteoarthritic hip, a hip with avascular necrosis often has more uniform bone porosity. The posterior wall is at risk for blow out if the surgeon preferentially reams posteriorly.
Fluoroscopy can be used to check position of the reamers. However, this will not give anteroposterior (AP) placement of the reamer and, therefore, direct anterior and posterior wall visualization is necessary.
Implant placement in DAA tends to be too vertical and anteverted during the surgeon’s learning curve (Figure 4). This can be minimized by assessing the anterior wall and matching the rim of the cup to bone. It often appears as if the implants are too neutral with regard to version. An implant that will not seat definitively is usually blocked by labral tissue that is invaginating into the acetabulum during impaction. Complete removal is necessary. Inadequate press-fit can occur if the reaming is not deep enough to gain acceptable coverage of the cup or if the preparation is not spherical. These are easily determined with a simple fluoroscopic image.
Figure 4. Typical misplacement of cup early in the learning curve (vertical, anteverted, proximal).
Acetabular fracture can occur with severe strikes to the implant. This is best avoided by making sure the labrum is removed and the prepared bone is reamed spherically.
Femoral complications arise primarily from the inability to correctly expose the femur and allow safe and accurate preparation. There are 2 essential releases to allow the femur to be delivered from a deep position behind the lateral acetabulum.
- First, the pubofemoral ligament is released to allow sufficient external rotation of the femur.
- Second, the ischiofemoral ligament is released to its insertion in the piriformis fossa. This allows further external rotation and allows the femur to be delivered from behind the acetabulum.
Further releases, in the author’s preferred order, include the conjoint tendon (obturator internus and superior gemellus) followed by the piriformis. The OE is not released as it is a primary stabilizer of the hip. Exposing the femur requires delivery so that access to the canal is obtained safely and without untoward bone or soft tissue tension.
Extensile exposure of the entire femur is possible through the DAA. Briefly, the skin incision is extended distally and posterior along the mid-coronal plane of the femur. The TFL/iliotibial band is retracted laterally, exposing the VL. The VL can then be either split in line with its fibers or elevated from posterior to anterior to expose the lateral femur.
The first error commonly experienced is broaching the femur in too much anteversion. This occurs because inadequate release has resulted in effective internal rotation of the femur. A good landmark is to broach co-planar with the posterior cortex of the cut femoral neck. An internally rotated broach introduces torque to the proximal femur, which may result in either fracture or poor implant placement.
The second problem with broaching is attempting an attack into the canal that is too steep. It is often difficult to appreciate the exact location of the canal, leading to perforation of the lateral cortex. Although a varus stem position is acceptable, perforation of the cortex must be dealt with by bypassing the defect only. No other fixation (such as cerclage cable) is necessary unless a distal split of the femur has occurred.
Broaching angle errors can be prevented by hyperextending the hip and locating the canal with a curved awl before broaching.
Femur fractures occur during any THA procedure regardless of approach. With the DAA, the key is recognizing that such a fracture has occurred and then understanding its mechanism and how to treat – or not treat – the fracture.
The greater trochanter (GT) may fracture at the tip during the femoral neck osteotomy. The GT is at risk of iatrogenic injury if the femur is externally rotated (allowing the GT to rotate posteriorly) and the osteotomy is performed straight anterior-posterior. To prevent this from occurring, the femur should be in neutral rotation and the osteotomy angled medially.
The GT may also fracture during extension in patients with weakened bone or during broach removal. If the soft tissue sleeve of this bone is intact, preventing escape of the fragment, the fracture should not be fixed; it will heal through bone or fibrous union with no untoward effects on the patient. Postoperative abduction exercises should be avoided.
A calcar fracture may occur during impaction of the stem because of increased proximal hoop stress. Identification of this fracture is key, as failure can lead to fracture propagation and subsequent subsidence of the stem. This fracture is fixed with a cerclage cable placed proximal to the lesser trochanter (Figure 5).
Figure 5. A calcar fracture fixed with a cerclage cable.
An extended diaphyseal fracture may occur via multiple mechanisms, the most common being malrotation of the broach or aggressive impaction. This fracture must be treated. If the fracture is a simple, stable longitudinal fracture, the author’s preferred technique is simple cable cerclage with increased implant size (Figure 6). Alternatively, a longer diaphyseal-engaging stem can be used to bypass the fracture, thereby obtaining intramedullary fixation (Figures 7a-b).
Figure 6. A diaphyseal fracture treated with cerclage cables.
Figures 7a-b. A proximal femur fracture is bypassed with a longer stem.
A cortical perforation fracture may occur during broaching. This fracture should be examined closely. A small, proximal perforation may be treated by cautiously realigning the stem down the intramedullary canal. However, significant defects or perforations with fracture extension down the femur should be treated with a long stem that bypasses the defect (Figures 8a-b).
Figures 8a-b A cortial perforation is bypassed with a longer stem.
It should be noted that other lower extremity fractures have been reported with DAA directly related to orthopedic table use. [8, 9] These fractures are minimized by strict adherence to DAA technique.
Implant placement is straightforward in the DAA. However, several factors should be evaluated before accepting final implantation. First, if an implant is seated too proud from the broach, an unacceptable leg length discrepancy may occur. Second, if the final implant seats deeper than the equivalent broach, then a high degree of suspicion for fracture must occur. The author’s preference in this situation is to remove the stem and obtain radiographs at oblique angles to show the fracture, as they are sometimes not visible on the AP view.
Subsidence can also be predicted by the final placement. In general, varus and neutral stems will not subside, while valgus stems predictably subside (Figures 9a-b).
Figures 9a-b. A varus stem (top) and at-risk valgus stem (bottom).
Postoperative Protocol for Complications
After fixation, many fractures encountered can be rehabilitated with routine standard protocols and weight-bearing as tolerated. However, it is the author’s opinion that postoperative weight-bearing should be modified to allow time for fracture consolidation and soft tissue healing. In addition, fractures of the greater trochanter should have abduction exercises limited for a minimum of 6 weeks.
The DAA is a powerful procedure for both patient and surgeon. As with any medical procedure, it has its own unique complications of which the surgeon needs to be aware. If complications occur, quick recognition and treatment will help ensure a good outcome for the patient. This paper has outlined common intraoperative complications of DAA, their treatment, and, most importantly, how to avoid them.
Tyler D. Goldberg is a board-certified orthopedic surgeon specializing in adult joint reconstruction. He practices at Texas Orthopedics, Sports & Rehabilitation Associates in Austin. Andrea Torres, BS, is a research assistant at Texas Orthopedics, Sports & Rehabilitation Associates in Austin.
The authors have no disclosures relevant to this article.
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