Evaluating the Direct Anterior Approach to the Hip
The direct anterior approach has experienced a resurgence in utilization in the past decade due to potential advantages over other approaches for total hip arthroplasty and a desire to perform hip reconstruction through a smaller incision with tissue-sparing techniques. What does the literature say about the direct anterior approach?
Akash K. Shah, MD; Dionisio Ortiz III, MD; James Slover, MD, MSc; and Ran Schwarzkopf, MD, MSc
The direct anterior approach (DAA) for total hip arthroplasty (THA) was first described by Carl Heuter in the late 1800s and subsequently refined by Smith-Peterson, Light and Keggi, and the Judets. [1-4] Modern literature frequently refers to this surgical method interchangeably as the Hueter approach and the Smith-Petersen approach when identifying the anterior-based incision that utilizes the interval to the hip joint through the tensor fasciae latae (TFL) and the sartorius muscles. 
The DAA has experienced a resurgence in utilization in the past decade due to potential advantages over other approaches and a desire to perform hip reconstruction through a smaller incision with tissue-sparing techniques.  Many orthopedic surgeons use the DAA exclusively for primary THA, while others also use it for complex revision procedures and in patients with hip fractures. [6-10] Advocates of the DAA have cited decreased pain, shorter length of stay (LOS), lower dislocation rate, and expedited recovery as rationales for employing the DAA. 
In polling done at the 30th Annual Meeting of the American Association of Hip and Knee Surgeons (AAHKS) in 2020, 45% of members said they prefer using the DAA for primary THA, compared with 12% in 2009 when the poll question was first asked and 40% at the 2018 Annual Meeting.  In past polling, AAHKS members who chose not to employ the DAA stated that their decision was due to perceived worse outcomes, no significant clinical benefits compared with other surgical approaches, and a steep learning curve that may lead to increased complication rates [12-14].
This review aims to summarize the published literature on the DAA, with a focus on comparative pearls and pitfalls. An understanding of the surgical technique and its outcomes can ultimately help surgeons better evaluate the role of the DAA in contemporary THA.
Patient Considerations and Challenges
Certain patient considerations are important for the DAA, as with any surgical approach to THA. With experience, surgeons may be able to use the DAA in most, even all, patients, regardless of body habitus or hip conditions. [15,16] However, early in the learning curve, the ideal candidate has been described as a flexible, non-muscular patient with a valgus femoral neck and good femoral offset – in other words, slender patients with a body mass index (BMI) less than 30 kg/m2 [17,18].
Although obesity can make any THA approach difficult, subcutaneous fat in the anterior hip region tends to be minimal compared with the posterior and lateral aspects. Patients with a large abdominal panniculus, however, particularly those with tissue that overlaps the upper thigh, are a challenge when using the DAA. The overlapping tissue has the potential to create a moist environment that may result in chronic skin irritation or fungal infection, making these patients more prone to wound complications. The DAA can be employed, but additional vigilance will be required to ensure proper healing of the skin incision. 
Variability in the anatomy of the native hip and pelvis may make the DAA more challenging to perform, especially during the learning curve: 
- A wide or horizontal iliac wing limits access to the femoral canal for broaching and femoral component placement.
- Acetabular protrusio positions the femoral canal adjacent to the pelvis and obstructs access to the femur.
- A neck-shaft angle with decreased offset positions the femoral canal deeper in the thigh.
- Anatomy in which limited space is available for adequate component placement, particularly in obese, muscular males.
Other instances in which the DAA is unsuitable include a deficient posterior acetabular wall from previous hardware or trauma and consideration of posterior acetabular augmentation. 
The learning curve associated with the DAA has been evaluated by multiple authors to determine the number of procedures a surgeon must perform to become comfortable with the technique. In a meta-analysis, Nairn et al  found that mean operative time was significantly lower by case 100 and that the complication rate decreased significantly as the surgeon performed more procedures using the DAA.
A prospective study by Pirruccio et al  compared operative results of a single surgeon’s first 100 DAA cases with the last 100 posterior approach cases. They found no significant difference in complication rate, estimated blood loss (EBL), or morbidity rate between the 2 approaches, concluding that the DAA may be implemented without any significant adverse risk when a structured learning process is followed.
Multiple studies have concluded that with proper training and exposure to a preset number of cases, the DAA can be implemented with minimal complications. [9,12,23-25] Most studies described mentorship or instruction by a senior surgeon for those new to the DAA.
The DAA is said to provide a faster recovery than other approaches. The term “recovery” is ambiguous in this context, however, as it can encompass multiple areas of the patient’s postoperative course. A number of authors have, therefore, attempted to tease out the significance of this metric.
In a randomized controlled trial of 60 patients, Zhao et al  compared the DAA to the posterolateral (PL) approach to assess differences in EBL, LOS, and patient-reported outcome (PRO) scores. They found that DAA patients had higher Harris Hip Scores (HHS) and University of California Los Angeles Activity Scores at 3 months. By 6 months, the PRO scores between groups were similar. Using PRO scores for 12,274 patients in the Dutch arthroplasty registry, Peters et al  compared the DAA to the PL approach and found that at 3 months, patients in the 2 groups had similar scores.
In a study by Tauton et al,  patients who underwent THA with the DAA were able to discontinue their walking aids sooner than patients who underwent THA with a mini-posterior approach, and at 2 weeks after surgery, had a higher mean number of steps per day. No differences were seen in PRO scores, radiographic parameters, or complications between groups. By 2 months after surgery, there were also no differences in activity measures. 
Similarly, Singh et al  compared the DAA with the posterior approach using the Forgotten Joint Scores (FJS). Initial data suggest that patients who underwent THA with the DAA achieved a higher FJS at 12 weeks, but this difference dissipated when the data were normalized to account for surgeon experience with their respective surgical approach. 
The available literature, therefore, provides no definitive answer on the metric of “recovery” for the DAA versus other surgical approaches to THA.
Surgeons who advocate for the DAA say that it can result in reduced postoperative pain compared with other THA approaches. Again, “pain” may be an ambiguous term that encompasses multiple factors. Institutional differences in pain protocols and analgesic/anesthetic usage may account for differences in pain experienced by patients and can be a confounder when comparing pain associated with a particular approach to THA. In addition, pain is a subjective measure, which can create difficulties when trying to quantify and standardize outcomes across groups and populations.
Zhao et al  compared self-reported postoperative pain scores in patients who underwent THA with the DAA with those who underwent THA with the PL approach and found lower scores among the DAA patients at 24, 48, and 72 hours. Cheng et al  compared Western Ontario and McMaster Universities Arthritis Index (WOMAC) scores for pain and stiffness in 72 patients who underwent either DAA or posterior approach THA. They found no statistical difference at 2, 6, and 12 weeks between groups. 
In a multicenter propensity score-matched study, Sauder et al  compared the DAA with the PL approach. They found that DAA patients were less likely to achieve a Patient Acceptable Symptomatic State (PASS) for the Harris Hip Score and Hip Outcome at their postoperative visit than PL approach patients.  In addition, there was no statistical difference in the minimal clinically important difference (MCID) for pain at 1 year after surgery.
With the literature divided on the topic, there is no easily identifiable delineation between the surgical approaches with regard to the metric of “pain.”
In-Hospital Length of Stay
Length of stay is a vital measure not only for patient safety, but also for the fiscal security of the facility and surgeon practice. Decreases in LOS can lower hospital-acquired infections, decrease costs, and allow for earlier return to normal activities, which in turn may result in increased patient satisfaction and outcomes.
Like recovery and pain, LOS is dependent on multiple patient factors, such as pre-existing conditions, age, gender, and smoking status, most of which are out of the surgeon’s control. Procedure-related factors, such as operative time, start time, and approach, may also affect LOS.
It is important to note that inpatient THA has been scrutinized in recent years due to several changes in the dogma of managing these patients. The Centers for Medicare and Medicaid Services removed THA from the inpatient-only (IPO), encouraging surgeons to move toward an outpatient model, although, of course, not all patients are candidate for outpatient management. In addition, the COVID-19 pandemic discouraged patients from undergoing elective procedures that required prolonged hospital stays due to fear of exposure, coupled with limitations on hospital resources. Therefore, any procedure or advance in treatment that may shorten LOS is a highly valuable commodity.
Cheng et al  examined LOS and time to home discharge for DAA patients versus posterior approach patients and found no significant difference between groups. In a meta-analysis of 17 studies, Higgins et al  found a significant decrease in LOS for DAA patients compared with posterior approach patients. They said, however, that the current level of clinical evidence demonstrates no clear superiority of one approach over the other, noting that the choice of surgical approach should be determined by the surgeon’s knowledge of and experience with the technique, patient characteristics, and surgeon and patient preferences. 
The DAA may be associated with a decreased rate of postoperative dislocations compared with other THA approach, but the data are conflicting.
In a propensity score-matched study, Maratt et al  compared DAA and posterior approach THAs and found no significant difference in dislocation rate between the approaches. They did, however, report that the posterior approach was associated with longer LOS, increased fracture risk, increased blood loss, and postoperative hematoma formation.  Similarly, Huerfano et al  found no significant difference in dislocation rate between the DAA and the PL in a meta-analysis of 25 studies containing 7172 patients.
Siljander et al  found that the dislocation rate was lower for the DAA when compared with the PL approach and the direct superior approach, although this finding failed to reach statistical significance. The study included 5341 THAs: 3162 PL approach, 1846 DAA, and 333 direct superior approach.  In a study with 38,399 patients, Charney et al  showed that patients treated with the DAA had a lower dislocation rate and fewer revisions for instability compared with patients treated with the posterior approach.
Pincus et al  found that patients treated with the DAA were at increased risk of dislocation when compared with patients who underwent THA by other approaches. This study consisted of population-level data, however, and did not control for the surgeon or hospital volume and experience with the DAA.
The DAA has a long and complex history and is advocated by some surgeons over other approaches in THA. To date, however, the published literature remains inconclusive and the decision to employ any approach should be based on training and personal preference. Further long-term studies are needed to determine if the DAA is superior to, equal to, or inferior to other approaches to the hip.
Dionisio Ortiz III, MD, and Akash K. Shah, MD, are NYU/ISK Adult Reconstruction Fellows at NYU Langone Health, New York, New York. James Slover, MD, MS, and Ran Schwarzkopf, MD, MSc, are from the Department of Orthopedic Surgery, Division of Adult Reconstructive Surgery, at NYU Langone Health, New York, New York.
Disclosures: The authors have no disclosures relevant to this article.
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