➢ Advantages of the direct anterior approach for total hip replacement include a muscle-sparing surgical technique without the need for postoperative hip precautions that can delay functional recovery.
➢ The direct anterior approach for hip arthroplasty can be performed with or without a special orthopaedic table.
➢ Clinical results have shown that the technique is safe, with infection, dislocation, and early revision rates comparable with those associated with the posterior and lateral approaches.
➢ The risk of complications such as intraoperative fracture and nerve palsy appears to decrease with operative experience.
Total hip surgeons have tried to improve on the approximately 80% twenty-five-year survival rate associated with Charnley total hip arthroplasty1. For instance, investigators have addressed the risk of complications, the recovery time, and the longevity after total hip arthroplasty.
Proponents of minimally invasive total hip arthroplasty techniques have pointed to traits such as shortened surgical scar lengths, decreased soft-tissue trauma, diminished blood loss, and quicker pain and functional recovery2. Many variations of minimally invasive techniques involving single to multiple incisions have been developed over the years. Opponents, however, have pointed to the increased difficulty of obtaining optimal implant positioning, the lack of evidence demonstrating improvement in clinical measures, and the importance of implant positioning as the key variable affecting longevity. According to these opponents, if implant positioning is compromised in favor of a shorter incision, the long-term survival of the implant may be jeopardized2-6.
In recent years, the direct anterior surgical approach has been associated with minimally invasive total hip arthroplasty5. As more surgeons have adopted this method, the question has arisen as to whether or not claims of earlier functional recovery are balanced with the unique complications and drawbacks associated with this approach. In the present study, we reviewed the existing peer-reviewed literature to determine whether direct anterior minimally invasive total hip arthroplasty reflects a new surgical standard or is simply a passing fad.
The direct anterior surgical approach was first described in 1881 by Carl Hueter in his surgical textbook, Grundriss der Chirurgie5,7. Contrary to the notion that this is a new method, the direct anterior approach has been used for total hip arthroplasty for nearly 100 years. Smith-Petersen8 used this method in 1917, and the Judet brothers9 and O’Brien10 continued to use it in the 1950s. However, the potential risk of complications while preparing and implanting the femoral component and the reported success associated with Charnley’s transtrochanteric approach caused the direct anterior approach to lose popularity.
A resurgence of the anterior approach occurred when surgeons performing hip resurfacing, such as Wagner in 197811, utilized the Hueter approach7 to maximize exposure of the femoral head and neck and the acetabulum while utilizing muscle-sparing intervals to minimize morbidity. The use of the direct anterior approach for arthroplasty with an orthopaedic table was first described by Judet and Judet in the mid-1980s12. Contemporary authors have reported success, with minimal complications, in association with the use of a so-called orthopaedic table13,14. As minimally invasive techniques have developed, variations of the anterior approach involving single or multiple-incision techniques also have been used successfully15,16. It is important to note that an orthopaedic table is not essential for direct anterior total hip arthroplasty; the technique has been reported to be feasible and reliable without the use of such a table5,17,18. Without the orthopaedic table, an operating table that allows for the foot of the bed to be extended is required. This positioning makes delivery of the femoral head possible by hyperextending and adducting the hip and utilizing retractors to elevate the proximal part of the femur for access.
The attraction of the direct anterior approach for total hip arthroplasty is the intermuscular dissection. The approach provides excellent exposure to the acetabulum and reasonable femoral access, with or without the use of a special table5. The patient is placed in the supine position, with the lower extremity, including the hemipelvis, prepared into the operative field. If an orthopaedic table is not used, both lower extremities can be in the operative field17.
The skin is incised 2 to 3 cm posterior and 1 cm distal to the anterior superior iliac spine over the tensor fascia muscle belly13. A general rule for the proximal boundary of the incision is the inguinal crease. Many surgeons elect to begin the incision slightly more posteriorly in order to minimize the risk of injuring branches of the lateral femoral cutaneous nerve. Once the tensor fascia is encountered, the fascial incision is made in line with the skin incision, allowing the tensor muscle to be retracted laterally. Then, an extracapsular retractor is placed along the superolateral aspect of the femoral neck. The vastus lateralis fascia is incised, and ligation of the ascending branch of the lateral femoral circumflex vascular complex is performed. Elevating the sartorius and the direct head of the rectus medially exposes the reflected head of the rectus. The reflected head is elevated off the capsule with the iliocapsularis, and a retractor is placed superiorly along the acetabulum to retract the iliopsoas and rectus muscles. A second extracapsular retractor is placed inferomedially along the femoral neck. The capsulotomy is performed (with use of one of multiple variations), and the extracapsular femoral neck retractors are placed intracapsularly.
The femoral neck osteotomy is performed as either a single13 or double cut18. It may be beneficial to dislocate the hip prior to the osteotomy to facilitate femoral head removal13. Once the femoral head is excised and removed, the acetabulum is prepared with the excellent exposure provided. Reaming of the acetabulum is done with or without customized reamers and typically with use of fluoroscopy to minimize the risk of too much anteversion and abduction of the acetabular component.
Once the acetabular component has been positioned with use of fluoroscopy, attention is turned to the preparation of the femur, which requires hip extension, external rotation, and adduction with or without a special table. Injudicious force in externally rotating and lateralizing the femur can result in a fracture of the greater trochanter, femoral shaft, or ankle13. Sequential soft-tissue releases, including continued capsular release and possible release of the obturator internus and piriformis, can be performed to improve mobilization of the femur. Superior capsular release has the greatest impact on the ability to elevate the femur when compared with release of the anterior or posterior capsule or the obturator internus19. To minimize the risk of dislocation, the obturator externus must not be violated.
Once the femur has been prepared, the subsequent steps of trial and final implant placement are performed. Reversing the steps of dislocation—flexion, abduction, traction, and internal rotation—reduces the hip. In addition to clinical appearance, the use of intraoperative fluoroscopy allows instant feedback regarding implant positioning and limb-length comparison.
The direct anterior approach also can be used as an extensile exposure, particularly during revision arthroplasty. The incision can be extended proximally into the standard Smith-Petersen approach and distally into the direct lateral approach to the femur20,21.
When trying to adopt an unfamiliar operative technique, a certain stepwise progression should be considered to minimize patient risk. Educational courses, cadaver dissections, and observing or performing actual procedures along with experienced surgeons have been recommended to minimize risk associated with a new technique4,18,22,23. Complication rates are typically higher until the surgeon becomes more proficient and experienced24,25. For the Hueter approach to total hip arthroplasty7, the number of procedures that are required before there is a decrease in complications has been reported to range from thirty to 20026-29. If the surgeon is very experienced with total hip arthroplasty30, there is less anxiety and less new information to assimilate.
Patient selection is important when starting out with the direct anterior approach. Several authors have cautioned that, early in the learning process, a surgeon should avoid managing patients who are morbidly obese, who are very muscular, or who have short femoral necks, acetabular protrusio, or wide iliac wings. These variations create challenges to safe exposure of the femur23,31.
The use of fluoroscopy is helpful to confirm component positioning and limb lengths, especially during the learning process13. The use of a fluoroscopic grid attached to the operating table increases the accuracy of component positioning and decreases operative time. It also may be useful for surgeons who have less experience with total hip arthroplasty32. Some authors have recommended the use of computer navigation, if available, as it can decrease operative time and improve acetabular component position33.
It appears that the number of surgical procedures required in order for a surgeon to adequately learn the technique is similar to those for other hip procedures. Lee et al.34, in a study in which cup positioning by two fellowship-trained arthroplasty surgeons was evaluated objectively with the LC-CUSUM (learning curve cumulative summation) test, showed that fifty procedures were required in order for the surgeons to consistently place the acetabular component in the optimum position during total hip arthroplasty. Furthermore, the proficiency level for learning hip arthroscopy is reported to be approximately thirty procedures35.
Outcomes and Complications
Several single or multiple-surgeon case series (Level-IV evidence) focusing on direct anterior total hip arthroplasty are now available in the literature. Although the skin incision varied according to author description, the deep intermuscular approach was the same in all series. Table I summarizes the largest published series focusing on the direct anterior total hip arthroplasty with or without the use of a special table13,14,28,29,36. For the studies listed in Table I, the deep infection rates were <1%, the dislocation rates were ≤1.5%, the revision rates were <3%, and the intraoperative fracture rates were ≤3.5% (with the highest fracture rate in the series without the use of a special table). Dislocations can occur anteriorly and posteriorly. Very few series have included information on functional outcomes. The Anterior Total Hip Arthroplasty Collaborative reported the preoperative and postoperative pain and function component scores of the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC)29. Both scores plateaued at three months, indicating early recovery.
The Hueter approach7 has been used successfully for hemiarthroplasty in elderly patients, removing the need for postoperative hip precautions (e.g., the use of bulky abduction pillows) that can lead to problems with mobility37. Correct implant positioning is attainable, and the risk of intraoperative fracture is approximately 3% according to Schneider et al.37.
There have been very few reports describing revision total hip arthroplasty with use of the direct anterior approach. Cogan et al., in a study of sixty-one isolated acetabular revisions (including forty-three that involved the use of a reconstruction cage), tested the hypothesis that the Hueter approach7 would decrease the risk of dislocation38. Only four anterior dislocations occurred (prevalence, 6.6%), and only one patient required revision of the acetabular component because of recurrent dislocations. Factors that were significantly associated with the risk of dislocation in that series included the number of previous operations and a higher body mass index (BMI) (mean and standard deviation, 29.7 ± 0.8). Other reports have described specific techniques to increase the extensile nature of the exposure to successfully address more complex revisions20,21.
Complications associated with any total hip arthroplasty approach ultimately determine whether that method is accepted by community orthopaedic surgeons as the new standard or is limited to a few surgeons. Anterior total hip arthroplasty has been associated with complications, but the literature suggests that the prevalence of such complications declines with surgeon experience. The two most concerning complications associated with the Hueter approach7 to total hip arthroplasty are intraoperative fractures and lateral femoral cutaneous nerve palsy. Table I shows the prevalence of intraoperative fractures in the larger series. The rate of lateral femoral cutaneous nerve palsy has been reported to be as high as 88%, with few patients having complete recovery, but this complication appears to be clinically unimportant and to be unrelated to good functional outcomes39,40. Undergoing a hip resurfacing procedure instead of total hip arthroplasty substantially increases the risk of nerve injury.
Comparison with Other Approaches
The anterior approach has been compared with the anterolateral or lateral approach in several Level-III and IV studies. Alecci et al. retrospectively compared the perioperative data for primary total hip arthroplasties that had been performed through either the direct anterior approach (n = 221) or the lateral approach (n = 198)41. The anterior approach group had less blood loss, fewer transfusions, decreased pain, shorter hospital stays, and fewer discharges to nursing homes. However, there were substantially more American Society of Anesthesiologists (ASA) class-II and III patients in the lateral approach group, which may have contributed to the differences mentioned. Berend et al. reviewed the results of primary total hip arthroplasties that had been performed through the less invasive direct lateral approach (n = 372) or through the direct anterior approach with use of a standard operating table (n = 258)18. The anterior approach group had greater blood loss, more discharges to home, a higher rate of intraoperative fractures, and higher six-week Harris hip and lower extremity activity scores but also had similar revision and complication rates in comparison with the less invasive direct lateral approach group. In the study by Restrepo et al., 100 patients were prospectively randomized to treatment with primary total hip arthroplasty through either the direct anterior approach (n = 50) or the direct lateral approach (n = 50), with identical postoperative protocols being used for both groups42. One year postoperatively, the direct anterior approach group had significantly better Short Form-36 (SF-36) and WOMAC scores. However, these differences disappeared at two years.
It has been hypothesized that the direct anterior (intermuscular) approach causes less muscle damage that is evident on magnetic resonance imaging (MRI) at one year postoperatively when compared with the lateral approach43. Although this hypothesis may help to explain the improved gait parameters seen at six weeks postoperatively, these gait differences tend to disappear by sixteen weeks44-46. However, when compared with control patients, those who have undergone primary total hip arthroplasty through either the lateral or direct anterior approach have persistent stair-climbing abnormalities at ten months47.
Direct comparisons with the more commonly used posterior approach for total hip arthroplasty are limited. Bergin et al. prospectively compared biomarkers for inflammation and muscle damage in patients undergoing primary total hip arthroplasty through either a minimally invasive posterior approach (n = 28) or a direct anterior approach (n = 29)48. Serum creatinine kinase levels were significantly higher (p < 0.05) in the posterior approach group, indicating more muscle damage. Of note, there were more males in the posterior approach group; although this difference was not significant, males typically have more muscle mass, which could account for some of the observed differences in the creatinine kinase levels. Tsukada and Wakui reported that, among elderly patients with femoral neck fractures, early function was better for those who underwent bipolar hemiarthroplasty through the direct anterior approach as opposed to the posterior approach49. However, Wilson et al. reported that, at one year, there was no significant difference between the approaches in terms of Hospital for Special Surgery scores50. Likewise, Maffiuletti et al. reported that the direct anterior approach may positively affect gait for the first six months after primary total hip arthroplasty but reported no differences in terms of SF-12 and WOMAC scores51. Last, Nakata et al. reported that, in comparison with the minimally invasive posterior approach, the direct anterior approach was associated with more blood loss but also was associated with significantly faster early functional recovery52.
Conclusions and Clinical Care Recommendation
The direct anterior (Hueter) approach7 for total hip arthroplasty is not a passing fad. However, existing data are insufficient to make the statement that this approach reflects a new standard. As a result, we can only state that there is a fair amount of evidence to support recommending direct anterior total hip arthroplasty as an intervention, with very few studies suggesting that the risk of complications is too high during the initial period of learning while the surgeon continues to gain experience with the technique (Table II).
There are several factors that support this recommendation. At best, early recovery is enhanced, and, in the hands of skilled surgeons, the risk of complications appears to be comparable with those associated with other approaches. The operative method itself is not new; it was first described in the literature in 18817. In several studies, the dislocation, revision, and deep infection rates associated with the anterior approach were comparable with those associated with the posterior and lateral surgical approaches53,54. The early surgeon experience is also fraught with the risk of intraoperative fracture and lateral femoral cutaneous neurapraxia, both of which decline with surgeon experience55.
The literature has shown that the anterior approach is associated with improved early functional recovery in comparison with that after other, established approaches, but the advantages seem to dissipate relatively quickly. It is too early to tell if implant longevity and revision rates will be comparable with those reported in association with the lateral and posterior approaches. Until those data are available, surgeons must weigh the relative advantages and disadvantages associated with anterior total hip arthroplasty to decide whether or not to adopt this method in their surgical practices.
Source of Funding: No external funding sources were used in the support of this research.
Investigation performed at the Department of Orthopaedic Surgery, University of Missouri-Columbia, Columbia, Missouri
Disclosure: None of the authors received payments or services, either directly or indirectly (i.e., via his or her institution), from a third party in support of any aspect of this work. One or more of the authors, or his or her institution, has had a financial relationship, in the thirty-six months prior to submission of this work, with an entity in the biomedical arena that could be perceived to influence or have the potential to influence what is written in this work. No author has had any other relationships, or has engaged in any other activities, that could be perceived to influence or have the potential to influence what is written in this work. The complete Disclosures of Potential Conflicts of Interest submitted by authors are always provided with the online version of the article.
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