The DAA to total hip arthroplasty (THA) is a cost-
effective approach to hip replacement that is associated with excellent peri- and postoperative outcomes, pain relief, and an acceptable complication profile compared with other approaches.^1,2 Although the positive patient outcomes associated with this approach can in part explain the increase in the adoption of the DAA among orthopaedic surgeons, the economic benefit of using this method can further drive use in differing health care reimbursement environments.

In this chapter, we discuss the net benefit of using the DAA compared with other approaches as well as future strategic program development. We touch on the strategy of value development with regard to comparative effectiveness vs cost-effectiveness approaches to cost reduction in orthopaedics and as a whole. Evidence for the value of the DAA along with details of the history of the value-based approach to medicine and THA is also presented. Finally, recommendations are given on what is perceived to be the outlook of the modern DAA THA and what we can look forward to with respect to value-based health care.

The DAA to hip surgery, originally described by Carl Hueter in 1881, was later popularized by Marius N. Smith-Petersen (known as the Smith-Petersen approach) when he introduced mold arthroplasty in 1923 as an early precursor of today’s THA. Robert Judet is also credited for its popularization in pediatric hip disease and acrylic hemiarthroplasty. Thus, this approach was among the earliest to see broad use and was perhaps adopted by early pioneers for many of the same reasons for which it is seen as attractive today (ie, it provides direct access through a limited soft tissue envelope and is essentially internervous and intermuscular). Nonetheless, the early use of this approach may have appeared to be technically challenging because of the reliance on a fracture table as described by key pioneers including Light and Keggi and then later by Matta with the use of a specialized fracture table; this had perhaps discouraged the widespread use of the procedure³ because specialized retractors and instrumentation were needed to successfully complete the operation. Until recently, with the increased technicality of the DAA THA procedure, de Steiger et al⁴ determined a learning curve of 50 or more DAA procedures for surgeons converting to DAA from another approach; as hip surgery became more commonplace and more complex pathologies were being tackled, surgeons were driven to adopt approaches that they deemed more facile and more extensile.

Although the history of surgery has seen surgeons choose their surgical approach based primarily on the need to address the underlying pathology to be treated, recently a new era has emerged in which patients are increasingly driving considerations related to recovery and function. Decreasing average age for surgery and increasing expectations for higher-activity patients, including the need to return quickly to work or sports, have driven the patient demand for minimally invasive procedures, especially in the setting of younger patients returning to work after surgery and for older patients seeking immediate pain relief and quality of life in later years. The market and demand for such approaches are being experienced with increasing frequency in the realm of THA, with a perception among patients that the anterior approach lends itself to a faster recovery with fewer attendant restriction. These market forces have likely driven a concurrent increased adoption among orthopaedic surgeons. Surgeons have responded to these patient preferences and perceptions by increasingly adopting this approach as an option for their patients. In some cases, surgeons will continue to offer several approaches, attempting to match pathology and need with the best approach, whereas in other practices the perceived advantages have led to a wholesale transformation of the practice.

In the 2018 American Association Hip and Knee Surgeons poll, over 40% of American Association Hip and Knee Surgeons members were performing DAA THA compared with under 30% in 2016. When pooling from survey data, patients tended to request this approach due to the lower incidence of reported complications.⁵ Although the need to satisfy the demand of patients remains paramount, other environmental factors may come into play, including the economics of joint replacement, the overall paradigm shift to value-based care, and the changing setting of care delivery. Furthermore, with an increasing demand for such services due to an aging population and increasing prevalence of osteoarthritis, understanding the impact of this approach on the micro- and macroeconomic concerns of payers, providers, and policy makers will be paramount.

There is strong evidence that the DAA provides measurably improved short-term clinical and functional outcomes and a reduction in perioperative pain. In a prospective randomized controlled trial of 116 patients, Taunton et al¹ found that patients randomized to the DAA experienced a shorter time in discontinuing their walker (10 vs 15 days, P = .01), a shorter time to discontinuing all gait aids (17 vs 24 days, P = .01), and greater mean steps/day (3897 vs 2235, P = .01).

These clinical findings are consistent with those found in retrospective reviews looking at in-hospital, 90-day, and 1-year outcomes. In a systematic review and meta-analysis of seven randomized controlled trials, Miller et al⁶ analyzed the in-hospital outcomes of 609 patients and found a significantly shorter incision length, shorter hospital stay, less pain, and lower postoperative opioid use (P < .05) compared with the posterior approach. The only significant feature of the DAA that was unfavorable was a longer mean operative time.⁶ In a propensity score-matched analysis of 1794 patients, Kamath et al⁷ found decreased length of stay (2.07 vs 2.98 days, P < .0001) and an increased proportion of patients discharged to home (87.3% vs 68.7%, P < .0001) for patients who underwent DAA THA vs all other approaches.

Zawadsky et al⁸ similarly found reduced length of stay compared with a mini-incision posterior approach (2.9 vs 3.9 days, P < .0001) and an increased likelihood for discharge home (80% vs 56%, P = .0028). When analyzing 90-day outcomes, Miller et al⁹ analyzed 13 prospective studies and among 1000 patients found less pain with concurrently less narcotic use with the DAA group; in addition, better hip function was recorded. Seah et al¹⁰ also reported lower daily opioid use and lower pain scores in the early postoperative period with the DAA. In a noncomparative DAA series, Chughtai et al¹¹ found a 0.3% complication rate with a mean postoperative Harris Hip Score of 88 (P < .01) at 1 year.

Finally, in a systematic review and meta-analysis of 19 studies outlining >1-year outcomes, Miller et al⁵ found a lower risk of reoperation, dislocation, and infection for the DAA; however, patients reported more nerve injury, specifically that of the lateral femoral cutaneous nerve. This body of evidence from multiple systematic reviews and multiple meta-analyses indicates that the DAA is a clinically successful approach to THA, with early benefits sustained throughout the midterm postoperative period.

When considering an approach to THA, one must consider not only the clinical outcomes but also any relative economic concerns or advantages. Discussion of any health care topic in the United States, with its significant cost disparity in comparison with the remainder of the world, must include cost. Payers, providers, patients, and policy makers are rightfully asking for an understanding of the value of a procedure or episode of care, with an eye toward promoting those procedures that can deliver equal or better quality but at a reduced cost. According to the latest Health Care Cost Institute data, the average 2017 US hip arthroplasty admission carried a cost of $32,500 compared with an average cost of $6900 in Holland (2017 US dollars).¹² In Sweden, in-patient costs were as low as $502 (US dollars) in a study by Rolfson et al.¹³ In their study, it was determined that productivity loss from the patient’s inability to work had a greater economic impact than the surgery itself.

Health care costs are on the rise, even though attention has been placed on the introduction and implementation of value-based programs. Experts have pointed to administrative waste, costly technology implementation, a lack of competition in areas with hospital consolidation, the increasing Consumer Price Index, and a growing aging population as among the reasons for these increasing costs. The United States spent $3.6 trillion on health care ($11,000 per person), with that figure projected to increase to $6.2 trillion ($18,000 per person) by the year 2028.¹⁴ Total health care spending consists of two factors: the cost of the health care services themselves and the degree of utilization of such services. Given a procedure of increasing prevalence, such as THA, it is clear that cost must be considered, in addition to clinical outcomes, when evaluating the value of innovative practices.

In their landmark book entitled Redefining Health Care: Creating Value-Based Competition on Results, Porter and Teisberg¹⁵ sought to define value in health care as the relationship of quality to cost. They contended that, if purchasers and users of health care had a value framework, then competition among health plans, health systems, physicians, and hospitals in the diagnosis, treatment, and prevention of diseases can drive efficiencies in the market and thus lower cost. Value has been defined as the outcomes (quality + service + safety) over the cost¹⁵ (Figure 52.1). In search of value, there has been a hypothesis that the move away from fee for service toward alternate payment models known as value-based payment programs can drive cost reduction.

Several programs have been introduced based on this hypothesis, and the Affordable Care Act codified this approach into law with its passage in 2010. The initial pilot began in 2009 with the introduction of the Medicare Acute Care Episode demonstration by the Centers for Medicare and Medicaid Services (CMS) program, which used 28 cardiac and nine orthopaedic inpatient surgical services and procedures.¹⁶ This demonstration was limited to five centers in Texas and Oklahoma and was the first government-sanctioned program to demonstrate the advantages of aligning the incentives for both physicians and hospitals in pursuit of higher quality of care and value.

The Bundled Payment for Care Improvement (BPCI) initiative established by the newly created Center for Medicare and Medicaid Innovation in 2011 was launched in 2013 and was the first large-scale demonstration project, ultimately expanding over multiple enrollment windows to over 2000 sites. This program defined an episode of care as a composite of all related services over a specified period of time, at first 30 or 90 days, and eventually established the 90-day postoperative episode duration. Surgeon and/or health systems could choose to go at risk for the composite price of the episode and were thus incentivized to identify waste and inefficiencies. The average savings from the BPCI program was over $800 per case, confirming that when incentivized providers could find ways to reduce unnecessary spend.

Episode-based payment models have been warmly embraced by CMS as a method to reduce cost while maintaining quality. Further iterations include the Comprehensive Care for Joint Replacement (CCJR) model introduced in 2015 and the follow-up BPCI advanced model that further build on the experience with composite pricing and provider contraction. Ultimately, it has been the goal of CMS to learn from these programs and to move much of payment for services into alternate payment approaches. At one point, the stated goal was for up to 75% of payments to be issued through one or more such model, but as experience has increased, it remains unclear whether this goal is correct or can be achieved. Although the BPCI initiative was voluntary, the 2016 CCJR rollout was compulsory for surgeons and hospitals in 67 targeted metropolitan statistical areas as defined by CMS; metropolitan statistical areas were counties with a core urban area associated with a population greater than 50,000 people.

As physicians and health systems have become accustomed to thinking about THA as an episode of care, the appeal of the DAA THA rests in part on the economic advantages realized through the potential for overall episode cost reduction. Numerous studies have modeled the economic benefits of using the DAA compared with other approaches. When analyzing the 90-day differences between approaches, Miller et al¹⁷ found a per-
patient savings of $6206 (2016 US dollars) in patients using the DAA compared with a matched control group of all other approaches. Their model included patients from the publicly available Medicare Standard Analytic File from 2012 to 2014. In-hospital stay and postoperative discharge health care utilization over an episode of 90 days were analyzed. Payer mix-adjusted costs were calculated by applying a private payer-to-Medicare multiplier of 1.68. Approximately 35.8% of payers analyzed were private; $2400 of the overall savings was realized during the index admission, $3800 in savings was realized due to lower utilization of postacute care, and $900 was due to fewer readmissions within the 90-day postoperative period.

In their study, it was postulated that lower narcotic usage associated with lower pain scale reporting, as well as faster discharge rates, contributed significantly to these cost savings. Using the same database, Kamath et al⁷ found a lower overall wage-adjusted payment over the 90-day period for episodes using the DAA compared with all other approaches ($4139 vs $7465, P < .0001). When stratified by setting of care, the DAA was more cost-efficient than all other approaches in every setting including the index admission ($10,873 vs $12,285, P < .0001), home health ($1688 vs $2095, P < .0001), skilled nursing facility ($1244 vs $2952), inpatient rehabilitation ($178 vs $965, P < .0001), and for readmission episodes ($561 vs $1269, P = .010). Other approaches had less costly episode cost in the hospital outpatient setting by a marginal amount ($360 vs $330, P = .017).