CORR Insights®: Do Postoperative Results Differ in a Randomized Trial Between a Direct Anterior and a Direct Lateral Approach in THA?

Where Are We Now?

In the current study, Mjaaland and colleagues [7] present a well-designed and thoughtful consideration of the direct anterior versus direct lateral approaches in THA. They conclude that although the direct anterior has a higher risk of nerve injury, and the direct lateral has a greater likelihood of abductor dysfunction, no meaningful difference in clinical outcomes was appreciated at any time point between 3 months and 2 years. The authors appropriately address three important themes: (1) Achievement of reliable and consistent patient-reported and functional outcomes, (2) avoidance of complications, and (3) the learning curve as it applies to incorporation of a new surgical technique.

Considerable refinement in THA technique in the decades following Charnley has generated not only multiple options, but also a polarizing debate as to which approach is “best”. Supporters of the direct anterior approach cite facilitation of early recovery and a low risk of prosthetic dislocation, while detractors criticize the steep learning curve, and increased risk of intraoperative complications [1, 4, 6, 8, 10, 11]. Those in favor of the posterolateral approach cite its utilitarian nature, familiarity, and technical reproducibility, while critics point to an increased risk of dislocation [4, 6, 10, 11]. Proponents of the direct lateral and anterolateral approaches most frequently cite extraordinary stability while disbelievers focus on the risk of persistent postoperative limp [8].

In the face of largely inconclusive data to definitively support any one over another, an individual surgeon’s preferred approach to THA therefore may be influenced by a number of subjective factors, including exposure during training, influence of mentors, and the balance of potential risks and benefits that the available evidence has suggested may apply to each approach. Indeed, surgeons have come to appreciate the characteristic set of pros and cons reliably associated with each technique.

At any stage of practice, incorporation of a new technique is accompanied by a requisite learning curve, the nature of which has been well-described for direct anterior THA [3]. When the impetus for developing a new technique is additionally influenced by nonclinical factors such as marketability, the impact of the learning curve on patient safety and risk of complications must be considered carefully. In recent years, orthopaedic education has appropriately trended towards a competency-based model with advancement dependent upon achievement of defined performance standards [2, 5, 9]. Such competency-based evaluation may be more practically applicable to the traditional graduated apprenticeship model of residency and fellowship as opposed to the alternate models of observation, course enrollment, and cadaveric laboratory participation more commonly used by experienced surgeons seeking to gain specialized skills after completion of formal training.

Where Do We Need To Go?

One must consider whether the addition of new technique provides enough value to future patients to justify the potential increased risk of complications for those first few [1, 3, 8]. What are the best methods to facilitate adoption of new techniques while minimizing patient risk associated with a learning curve? How does the traditional model of graduated apprenticeship compare to the experience of seasoned surgeons who develop new skills via self-directed laboratory and observation experiences?

Nearly 30% of patients otherwise eligible for participation in the current study were appropriately excluded because they had explicitly requested direct anterior THA. The preponderance of patients with a stated preference for surgical approach is reflective of the impressive direct-to-consumer marketability of direct anterior THA. One might wonder to what extent do nonclinical factors impact the decision to offer a particular approach to THA? Furthermore, does the message received by patients reflect an accurate and measured interpretation of outcomes and complication rates associated with surgical approach to THA?

Beyond seeking a “winner” in this debate, future studies should add nuance to the questions they seek to answer, such as “Under what circumstances might an alternate approach for THA provide meaningful advantage?”, or “Which THA patients will benefit most from an approach different than one’s default approach?”

How Do We Get There?

Modern national joint replacement registries like the Swedish Hip Register and the American Joint Replacement Registry provide data on numerous THA approaches and will continue to provide guidance particularly with respect to the likelihood of reoperation and revision. The precise nature of complications associated with each THA approach is likely to become more accessible as registry data collection continues to evolve. Considering that the vast majority of THAs are performed outside academic centers, registries additionally provide feasible opportunity for surgeons without academic resources to report outcomes and contribute greatly to the generalizability of data.

The incorporation of core competencies into the curricula of orthopaedic education remains a work in progress, though these efforts may provide a template for application in the setting of postgraduation training. The concept of certification in a new technique with objective assessment prior to independent practice would need to be validated against the current models through prospective evaluation of rates of surgical complications, operative time, and patient reported outcomes over a representative sample of independent cases encompassing the learning curve.

The impact of nonclinical factors on an individual surgeon’s decision to devote time towards adding a new approach to THA may be most simply addressed through a survey of hip surgeons regarding their attitudes, tolerances, relevant personal experience, and observations of colleagues. Such an investigation could also capture information about the rate of abandonment when a new approach failed to live up to expectations. In an era where patients are as likely to learn about approaches to THA through social media as from their surgeon, a simple questionnaire that assesses not only patients’ sources, but also interpretation of information regarding THA, could guide dissemination of accurate materials.