Troubleshooting the Direct Anterior Approach





Introduction


The only true intermuscular and internervous approach in total hip arthroplasty (THA), the direct anterior approach (DAA) continues to increase in popularity. Several proposed advantages have been attributed to DAA utilization, including lower dislocation rates, more accurate cup position, quicker patient mobilization, less early postoperative pain, and shorter length of stay. Over the past 2 decades, the DAA has been facilitated by the development and refinement of surgical implants, retractors, and approach-specific instrumentation.


Compared with other approaches for THA, the DAA spares major soft-tissue structures stabilizing the hip. The posterior capsule, short external rotators, and gluteus maximus are preserved, helping to protect against posterior instability. Further, the gluteus medius and minimus are preserved, mitigating the risk of abductor weakness, Trendelenburg gait, and instability. This combination of factors potentially reduces the risk of dislocation and reduces soft-tissue violation that may result in permanent dysfunction. However, the DAA can be a technically demanding surgery; understanding of potential challenges is critical in ensuring a successful patient outcome.


The goal of this chapter is to review the potential complications of the DAA, including preoperative and patient-specific factors, intraoperative technical considerations, complications, and their management.


Preoperative Factors


Patient Assessment


Preoperative planning and patient assessment are critical to ensuring satisfactory outcomes with the DAA. The DAA may be used as a primary approach for virtually any THA.


Body Habitus and Physical Exam


Obesity is a concern for every primary THA, and certain considerations should be taken for the DAA. In obese patients, the pannus may drape over the surgical site. During the preoperative examination, the skin should be closely examined for any areas of breakdown, chronic skin changes, excessive moisture, fungal infection, or ulceration. Although pannus can be directed superiorly and away from the surgical field in the supine position, there is a concern for postoperative wound healing due to incisional maceration and fold moisture. In the obese population, studies have demonstrated a higher rate of prosthetic joint infection, higher rates of wound complications, and higher rates of wound complications requiring reoperation. Obesity and diabetes mellitus have been found to be significantly associated with postoperative wound healing complications. Purcell et al. noted no difference in periprosthetic infections between obese patients undergoing the DAA versus posterolateral approach. However, the authors did report a higher rate of wound complication in the obese DAA group. Patients should be counseled and educated on pannus management in the perioperative period, with a focus on keeping the area dry and free of pressure. Some authors describe using an abdominal binder to prevent the pannus from overlying the incision following surgery. Incisional wound vacuum devices have also been shown to decrease wound complications in high-risk patient populations. ,


Special attention should be paid to actual and perceived leg length discrepancies. For surgeons using a standard table, recording preoperative supine leg lengths is critical for intraoperative guidance. In our experience, standing assessment of leg lengths using measured blocks under the operative limb can guide intraoperative lengthening goals for surgeons utilizing fluoroscopy intraoperatively.


Large hip and knee flexion contractures on the operative limb can preclude proper limb mobilization intraoperatively. These findings are especially pertinent to note when utilizing a specialized table, as hip extension for femoral exposure may be limited. Contralateral hip and knee flexion contractures can also interfere with fluoroscopy and assessment of limb lengths. External rotation contractures should be noted, as they frequently require further superior capsule and short external release for femoral mobilization.


Imaging Assessment


Preoperative imaging should be closely examined to recognize potential intraoperative challenges. Correlating radiographic limb length discrepancy with clinical and/or perceived discrepancies is imperative. Careful attention should also be paid to offset, which will influence cup placement (e.g., depth of medialization) and stem choice (e.g., standard vs. high offset). Preoperative assessment should include consideration of implants. Although almost any system can be used for the DAA, longer stems with ream-and-broach-style preparation often require a more extensile exposure to gain co-linear femoral canal access.


A horizontal or wide iliac wing can limit access to the femoral canal. Protusio, minimal femoral offset, and high neck shaft angles place the femoral canal close to the pelvis, potentially requiring larger, more extensile releases due to limited femoral canal access during broaching. Short varus necks with large superior neck osteophytes may also present a challenge to identifying the appropriate level at which the neck cut should be made. In this scenario, the use of intraoperative fluoroscopy allows the surgeon to confirm landmarks and level of resection.


Patients who have previously placed hardware from a posterior or lateral approach may be difficult to access via the standard DAA. A separate incision can be made to address the hardware. If it is felt that one surgical approach to remove the hardware will best preserve soft tissues, then that approach may be more appropriate.


Severe femoral deformity makes accessing the canal more difficult when using the DAA. For example, the need for a femoral shortening osteotomy and diaphyseal engaging stem in the setting of Crowe Type IV dysplasia may prove challenging. Conversely, the ability to utilize intraoperative fluoroscopy enhances cup placement and allows the surgeon to confirm the osteotomy level. Posterior wall or posterior column defects requiring grafting or augments can be difficult with the DAA, as can removing posterior acetabular hardware.


Operative Table Selection


The direct anterior approach can be safely performed on both a specialized surgical table and a standard operating table. Use of a specialized table to access the hip via an anterior approach has been utilized for decades, originally described by Judet and Judet and then expanded on by Matta et al. Prior studies have demonstrated no difference in intraoperative femur fracture rates, perioperative complications, or outcomes between a specialized surgical table and a standard table. , Variations and modifications to the standard surgical table also exist, including table attachments to maneuver and hold the operative leg, self-retaining retractors, and a femoral hook attachment that is used to elevate the femur. What follows will describe relative pros and cons of the different table options.


Specialized Surgical Table


The specialized surgical table secures the patient via a center groin post with both feet fixed in surgical boots on independent leg spars attached to the table. Acetabular exposure is easily performed and is similar across all table setups. Femoral access is consistently the more difficult portion of the DAA. It is aided by the specialized table through hyperextension, adduction, and external rotation of the operative extremity. A femoral bone hook can then be used to support the femur during broaching. The hydraulic hook should never be used as a tool to forcefully expose the femur due to fracture risk. Rather, the hook serves as a static retractor, holding the femur in a stable position during femoral preparation.


An advantage of the specialized table is decreased need for surgical personnel due to the leg spar and femoral hook holding the extremity in a secure, constant position. In cases for which traction is required, the table also provides a consistent and predictable force. The ability to utilize intraoperative imaging for evaluation of implant position, leg lengths, and offset is another valuable benefit of the specialized surgical table.


There are several disadvantages. Upfront cost and continued maintenance may result in a significant investment. Next, both the surgeon and operating room staff must be trained on how and when to manipulate the leg, with specific attention paid to preventing iatrogenic injuries such as nerve palsies, femur fractures, and ankle fractures. Finally, a radiology technician needs to be present for the case and must be facile with the appropriate views to limit operative and fluoroscopic exposure time.


Standard Table


A standard operating table is a viable alternative to the specialized surgical table. It is widely available, familiar to both surgeon and operating room staff, and comes at no extra cost to the hospital system. There is no need for further staff to run and manage the table, or to manipulate the leg during surgery. A standard table readily allows for intraoperative hip stability examination and manual assessment of clinical leg lengths. A notable disadvantage is possible requirement of extra scrub personnel to assist with retraction and limb manipulation. Although intraoperative imaging is feasible, it is not as facile compared with utilizing imaging with the specialized surgical table. Assessment of leg lengths must often be assessed manually on a standard table, which is prone to errors in positioning, and palpation of bony landmarks is more difficult. Femoral exposure is challenging and may require more soft-tissue release in order to adequately access the femoral canal.


Table Attachment Devices


A variety of devices exist to facilitate the DAA THA. These include mounted self-retaining retractors, portable spars, and femoral hooks. These attachments allow the use of stable adjustable spars and self-retractors while maintaining the “tableless” advantages listed earlier. The spars maintain consistency in limb position, and the mounted retractors allow for a decrease in scrub personnel. However, trained operating room staff members are required to manipulate the limb and the table attachments.


Intraoperative Complications and Their Management


Standard Incision and Skin Management


The DAA begins with identification of bony landmarks—specifically, the anterior superior iliac spine (ASIS) and greater trochanter. The incision starts 2 cm posterior and 1 cm distal to the ASIS, with an average incision length of 8 to 12 cm. By staying lateral to the tensor fascia lata (TFL)-sartorius interval, lateral femoral cutaneous nerve (LFCN) injury is more likely to be avoided. To prevent wound complications, efforts should be made to refrain from extending the proximal incision beyond the abdominal skin crease, especially in obese patients. If the exposure must be extended proximally, curving the incision laterally may help avoid the skin crease. Described in further detail later, the approach is extensile in both proximal and distal directions. Patients also tolerate adjunctive parallel incisions, such as in the need for hardware removal.


The main disadvantage of this incision is proximal wound healing complications, especially in the obese. Attention should be paid to the proximal and distal extent of the incision. While broaching, care should be taken to avoid skin abrasion at the proximal aspect. Do not stretch the skin, and extend the incision when needed. Avoid extensive undermining of the adipose/fascial layer, as this increases dead space for seroma formation. Hemostasis is also critical to prevent postoperative hematoma, especially of the lateral femoral circumflex vessels. Intermittent inspection of these vessels during surgery and a final inspection before closure is recommended to ensure that hemostasis is maintained. We recommend and routinely use a subcuticular closure with skin glue. A water-resistant dressing should be applied. In obese patients, or those at higher risk of wound complication, we routinely use an incisional wound vacuum dressing to facilitate healing.


Bikini Incision


Due to concerns regarding wound healing and cosmesis, the “bikini” approach was developed, described as a horizontal incision following the Langer lines. Different techniques are described in the literature. The incision is made either in the inguinal flexion crease or just distal and parallel to the crease, as demonstrated in Fig. 22.1 . The incision is typically centered on the ASIS and then utilized as a mobile window, allowing the DAA THA to continue in a standard fashion. Potential risks exist with this incision. The LFCN has a complex and variable branching pattern; there is a theoretically increased risk of injury to this nerve with the medial extent of the incision. However, results show similar outcomes of dysesthesia compared with the standard longitudinal incision. , To avoid LFCN injury, ensure that the fascial incision over the TFL stays lateral to the ASIS. Intraoperative attention must be paid to the amount of traction and soft-tissue tension applied during surgery, as this is likely the cause of LFCN neurapraxia. Concerns also exist regarding infection, as the medial aspect of the bikini incision is close to the groin. To our knowledge, no increased rate of infection or wound complications has been noted in the literature. Cosmesis and scar satisfaction is noted to be similar to slightly improved between the two incisions, while wound healing was improved in obese and nonobese populations. , , The main disadvantage is that this incision is not extensile in a distal direction. The level of lesser trochanter can be accessed, but access of the femoral shaft distal to this will need a separate, direct lateral incision.




Fig. 22.1


Bikini incision for direct anterior total hip.

Image courtesy of Jorge Manrique, MD


Initial Exposure


Obtaining exposure begins with ensuring adequate incision length and optimal position, as described earlier. Once capsular exposure is obtained, we prefer a hybrid capsular retention/resection technique. A T-capsulotomy is performed, tagging the inferior-anterior limb and resecting the superior-anterior capsule. The inferior capsule is reflected from the inferior femoral neck with cautery, allowing the femur to gain improved lateralization during broaching and posterior translation when prepping the acetabulum.


Identifying the level of the femoral neck cut should be based off accurate preoperative templating. The vastus tubercle and “saddle” (junction of the lateral neck and greater trochanter) are important landmarks that are used to approximate the level of the femoral neck cut. In addition, fluoroscopy can be used to confirm landmarks in cases in which abnormal anatomy or difficult exposure is present. Large osteophytes, a long femoral neck cut, protrusio, and short femoral necks may render femoral head removal difficult. To facilitate removal, multiple techniques can be employed, including a napkin-ring (wafer) cut, femoral traction, and preemptive osteophyte removal. Our preferred technique is to perform a napkin-ring cut followed by 1 to 2 turns of fine traction and positioning of the femur in 40 degrees of external rotation.


Standard exposure and preparation of the acetabulum is the next step, with removal of the labrum and circumferential visualization of the acetabulum. While placing retractors, it is important to note the position of the femoral nerve relative to the acetabulum. Cadaveric studies have demonstrated the locations that place the nerve at greatest risk of iatrogenic injury. Following the method as described by Wasielewski et al., a reference line is drawn from the ASIS to the center of the acetabulum. The intersection of the reference line and the anterior acetabular rim is defined as 0 degrees, with the femoral nerve closest to the acetabulum at 90 and 120 degrees. Care must be taken to avoid forceful retraction and placing the retractors too deep in these positions. Rim osteophytes, a long residual femoral neck, and nonmobile femur may result in difficult acetabular access for reaming. Thus, acetabular osteophyte removal, shortening the neck cut, and releasing the inferior capsule to improve removal mobilization are helpful methods to enhance exposure.


Acetabular Preparation and Implantation


A circumferential acetabular exposure with placement of the desired retractors should be followed by sequential reaming. Medialization to the desired depth and component size is estimated according to templating. Common reaming errors include reaming “up-and-in,” resulting in the loss of the anterior wall with proximal migration of the hip center. To prevent this, begin with a reamer 5 mm under the templated size (e.g., 47 mm reamer for 52 mm cup), centralize the reamer within the acetabulum, and inspect the acetabular walls following each ream. Fluoroscopy can be used to verify position and sizing during acetabular preparation. While inserting the final component, it is most common to place excessive anteversion and inclination due to the soft tissue of the thigh pushing against the insertion handle. The use of fluoroscopy, an extended distal incision, or offset impactor handle will mitigate this risk.


Early in the learning curve, it is common for surgeons to experience difficulty with obtaining an initial press-fit during cup insertion. If this occurs, remove the cup, regain a circumferential exposure, confirm that the acetabular rim is free of soft tissue, and confirm that the acetabular reaming is free of step-offs. In some instances, a slight increase in medialization may substantially improve initial press-fit. Typically, this sequence provides adequate fixation. The cup can be tested for stability with the insertion handle. If there is any concern regarding stability after replacing the cup, supplemental screws can be placed. Care must be taken to ensure that the screws are placed in the correct quadrant with proper visualization.


Femoral Exposure


Following acetabular preparation and implantation, the femoral hook is placed around the femur in the interval between the vastus and gluteal sling. It is helpful for gentle, static traction to be in place at this time, with the extremity placed in maximum external rotation following hook placement. A curved Hohmann retractor is inserted around the lateral greater trochanter, between the capsule and gluteus medius. To help lateralize the femur, a Mueller retractor is placed at the posteromedial calcar. The superior-lateral capsule is then released in a longitudinal direction, starting at the base of the residual lateral neck and extending proximally inside the border of the greater trochanter. Following this preliminary superior capsular release, while maintaining the short external rotators and piriformis, mobilization of the femur is assessed. This release is key in helping elevate the femur and clearing the greater trochanter from behind the acetabulum and pelvis. Release any remaining capsule adjacent to the lateral femoral neck osteotomy to complete the provisional superior capsular release. It is imperative that traction be released prior to dropping the leg into extension when using a specialized table. With traction off, the femur can be elevated by applying gentle anterolateral force with the femoral hook while the spar is dropped to the floor, with resultant adduction and extension of the operative leg. It is important to use the hook for retraction purposes only, not for forceful elevation of the femur. If access to the canal is not readily obtained, then further releases are necessary. The inferomedial capsule can be completely released at the calcar in a distal direction until the lesser trochanter is exposed. The superolateral capsule is again examined to ensure that it has been fully released, and the medial portion of the greater trochanter adjacent to the neck is completely clear. Inadequate release of this posterolateral capsule from the inside of the greater trochanter can lead to avulsion fractures. Often, these releases are enough to deliver the femur adequately for femoral broaching.


When proximal exposure continues to be inadequate, the TFL should be freed from adhesions until encountering its origin on the iliac wing. The proximal incision should also be extended to prevent proximal skin stretching. In cases of contracture, the conjoined tendons can be released from their insertion near the posterior greater trochanter. If needed, the piriformis tendon insertion on the superior border of the trochanter can also be released. There is little associated morbidity with these tendon releases, as the tendons do not recoil and have been shown to often heal in their anatomic position. Obturator externus is preserved due its more medial pull on the proximal femur, providing resistance to hip dislocation.


If femoral mobilization continues to prove difficult following the standard releases, bring the spar up to the neutral position. Next, maximally internally rotate the leg, followed by a return to maximum external rotation. This simple maneuver will often result in improved external rotation and exposure upon repositioning the leg for femoral preparation. If exposure continues to prove difficult, a more extensile approach is required.


Femoral Preparation


As described earlier, femoral exposure and preparation requires adequate anterior and lateral mobilization of the femur for broaching. With appropriate exposure, the entirety of the calcar should be visualized, and direct access to the canal for broaching should be unimpeded. Anteversion is often assessed by following the trajectory of the posterior calcar and aiming toward the apex of the calcar. Careful instrumentation of the canal with an awl or curette is helpful for determining the appropriate broaching trajectory. Standard, single, or dual offset broaches may be used according to surgeon preference and exposure needs. Offset handle broaches and holding the broach firmly internally rotated can counteract the tendency to increase anteversion. When broaching, toggling should be minimized in an effort to enhance axial stability of the final implant. Further, aiming the distal tip of the broach toward the patient’s anteromedial cortex when broaching will allow for a more colinear trajectory, improved proximal fill, and decreased perforation risk.


Extensile Exposure


The DAA has been criticized as being limited to primary arthroplasty due to difficulties with extensile exposure. However, extensile DAA exposure is well described and may be readily employed when required.


Distally, the DAA extends into the lateral approach to the femur. The incision is carried distally and posteriorly in a lazy-S shape to approach the femoral shaft. The iliotibial band is split, and the vastus is then elevated off the intermuscular septum or split. Attention must be paid to the perforating vessels, which can be ligated or coagulated. From here, the entire femoral shaft can be accessed. When possible, the vastus lateralis origin should be preserved. In certain cases, tagging and reflecting the vastus lateralis from its origin may be performed with subsequent repair.


When proximal extension is needed, the skin incision is extended proximally toward the ASIS and posteriorly along the iliac wing. The TFL fascial incision is extended proximally to the ASIS. If the TFL is not mobile and femoral exposure continues to be inadequate despite standard femoral releases, a TFL release can be performed. The skin incision is extended proximally, and 2 to 3 cm of the TFL is released off the iliac crest. A 1-cm cuff of tissue should remain on the iliac wing for future repair. Care must be taken to not release the TFL more than 4 to 5 cm along the crest, as this will violate the iliotibial band origin at the tubercle. Subperiosteal dissection may also be performed posteriorly beneath the gluteus minimus, allowing further access to the outer table of the ilium and both columns. Repair of the release is performed in conjunction with fascial closure.


An alternative approach for proximal extension is the ASIS osteotomy. In the primary setting, this exposure is best utilized when pelvic anatomy prevents femoral preparation despite the use of standard releases and offset broaches. The incision is extended proximally and posteriorly along the crest. The TFL-sartorius interval is developed to the crest, releasing 2 cm of TFL off of the iliac crest while leaving the sartorius and the inguinal ligament attached to the ASIS. Develop the interspinous interval and mark the osteotomy, which should extend 2 cm proximal/posterior to the ASIS and into the interspinous interval. Using a microsagittal saw and osteotome, the osteotomy is performed. Reflect the fragment medially to complete the exposure. To repair the fragment, a single 3.5-mm lag screw is placed into the iliac wing.


Femoral-Sided Complications


Femoral Perforation


When femoral perforations occur during broaching, they are most commonly located laterally and posteriorly. Femoral perforation rates are low, reported in less than 0.5% of cases. , Lateral perforations occur due to varus malpositioning, while posterior perforations are more commonly attributed to incomplete femoral exposure with obstruction by soft tissue and the ASIS. Thus, the surgeon’s hand is preferentially pushed toward the ceiling and away from the body. When inserting the broach, attention should be paid to directing the broach handle toward the floor (avoiding lateral perforation) and toward the body (avoiding posterior perforation). If there is concern regarding a perforation, broaching should be stopped and fluoroscopy used for assessment. Treatment depends on the size of the perforation. Small perforations can be bypassed with a standard stem and no postoperative weight-bearing precautions. Larger perforations, or those that propagate, may require a change in stem type, fracture stabilization, and modification of postoperative weight bearing. Most commonly, these perforations are bypassed with a primary stem, with no change in postoperative management.


Calcar Fractures


Reported rates of intraoperative calcar fractures range from 0.5% to 2.5% regardless of approach. , , Many risk factors have been identified, such as age, sex, stem design, body mass index, and, questionably, approach. , , , The most important aspect in the treatment of intraoperative calcar fractures is fracture recognition, as fractures identified and treated intraoperatively have low rates of subsequent postoperative fracture or aseptic loosening.


Calcar fractures may occur during broaching, hip reduction or dislocation, calcar planing, or final stem insertion. When a fracture is visualized, the distal extent must be identified. Intraoperative fractures are commonly limited to the proximal calcar and rarely extend far beyond the lesser trochanter. In this scenario, the broach or stem should be removed. The leg is placed in a neutral position, and cerclage cabling is performed. Our preferred technique is to pass the cable in the same manner as the femoral hook. With the leg 40 degrees externally rotated, the cable passer is placed between vastus and gluteal sling, looping around the lateral cortex and presenting at the posteromedial calcar. The cable can then be tensioned. Depending on the extent of the fracture, additional distal cables can be passed distal to the lesser trochanter and down the shaft. For displaced fractures extending distal to the lesser trochanter, a distally engaging stem is recommended. Larger displaced fractures extending into the femoral shaft may require additional plate fixation. Postoperatively, a period of protected weight bearing is often recommended based on fracture severity and final construct stability.


Greater Trochanter Fracture


Greater trochanter fractures are reported as occurring in 0.1% to 29% of cases, with the disparity in incidence due to methodology and methods in reporting. Homma et al. reported a 29% incidence of chip fractures, while Barnett et al. demonstrated a 0.2% incidence in a series of 5090 patients. , Similarly, the Anterior Total Hip Collaborative reported a 1% fracture rate and Hartford et al. reported a 2.2% risk of isolated greater trochanter fracture. , Small chip fractures reflect capsular avulsions during femoral exposure and elevation, typically due to incomplete capsular releases. These can typically be managed nonoperatively.


Identification of larger fracture fragments is important, which can be assessed with intraoperative fluoroscopy. Stability of the fragment should be assessed first. Even with larger fragments, many fractures are able to be treated nonoperatively through postoperative abduction precautions alone. As described by Matta et al., the “deltoid of the hip” is maintained with the DAA, conferring fracture stability to many fracture patterns. The TFL, vastus lateralis, and the gluteus maximus are not disturbed, helping to prevent displacement of any fracture fragments. In the event of fragment instability and gross movement, fixation is recommended. Addressing this through the DAA is difficult, and a lateral incision directly over the greater trochanter is recommended. Multiple techniques are available, including tension band or screw, plate, or wire fixation. Our preferred fixation method is a tension band technique. It affords secure fixation with less soft-tissue dissection and irritation than a claw plate. A separate incision is made directly over the tip of the greater trochanter. The fracture is cleaned of any debris and held (with either reduction clamps or longitudinal Kirschner wires [K-wires] down the lateral cortex of the femur) in its anatomic position. The first K-wire (1.6 or 2.0 mm) is passed perpendicular to the fracture, aiming just distal to the lesser cortex around the implant. If placement is correct on fluoroscopy, place a second K-wire in a parallel orientation starting 1 cm lateral/distal to the first wire with the goal of one wire anterior and one wire posterior to the implant. An anterior-to-posterior hole is drilled through the lateral metaphysis of the femur using a 2.0- or 2.5-mm drill bit. A cerclage wire is prepared by making a loop approximately one-third along its length and the shorter segment of wire is passed through the drill hole. The long segment of the wire is passed around the ends of the K-wires in a figure-of-eight configuration, deep to the abductors. The cerclage wire ends are then twisted to unite them. The wire ends are cut short and tension is applied by twisting the loops in the same direction at the same time in order to achieve equal tension on both limbs of the wire. The twisted wire ends are trimmed and turned toward the femur to prevent soft-tissue irritation. The K-wires are then bent 180 degrees and sunk into the trochanter to prevent backing out. An example of a greater trochanter fracture and tension band wiring is demonstrated in Fig. 22.2 .


Jun 18, 2022 | Posted by in ORTHOPEDIC | Comments Off on Troubleshooting the Direct Anterior Approach

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