PROs are a vital tool used to assess the impact an intervention has on a patient. They are an important adjunct to objective clinical and radiographic assessments at pre- and postoperative time points. These subjective metrics provide insight into the patient’s perspective of their own health and functional ability and are commonly used to assess patients before and after a surgical intervention. Increasing evidence supports routine assessment of PROs in the clinical setting can lead to improved care. Furthermore, there is growing interest and potential for using PROs to help guide care on the individual patient level, as well as to facilitate accountability and performance improvement of health care providers and systems.

This chapter reviews several of the most common patient-reported outcome measures (PROMs) and how they relate to direct anterior approach (DAA) THA. Specifically, the Patient-Reported Outcome Measurement Information System (PROMIS-10), Veterans RAND 36 Item Health Survey (VR-36) (RAND Corporation, Santa Monica, CA, USA), and the 36-Item Short Form Health Survey (SF-36) as markers of global health will be evaluated as they relate to DAA THA. The disease-specific Hip Disability and Osteoarthritis Outcome Score (HOOS), University of California Los Angeles (UCLA) activity-level rating, Western Ontario and McMaster Universities Osteoarthritic Index (WOMAC), and Forgotten Joint Score (FJS) are also reviewed.

In 1917, Ernest Amory Codman (1869-1940), a surgeon in Boston at Massachusetts General Hospital, introduced the idea of the “end result,” imploring surgeons to track and publish the outcomes of their surgical interventions.¹ He kept careful notes on his surgical cases and insisted on having patients follow up at 1 year postoperatively. He felt that the promotion of surgeons should be based in part on surgical case outcomes rather than on seniority, which was not well received by his physician peers or the hospital administration at that time.² Codman’s message was dismissed at that time by the Massachusetts General Hospital administration and continued to be overlooked by the broader medical and surgical community for decades. He later published a landmark book on shoulder surgery, created the first sarcoma registry, and became a founding member of the American College of Surgeons (despite never being a member of the American Academy of Orthopaedic Surgeons). It took many more decades before the ideas within his work on the end result were realized and respected, and these have now become a core part of orthopaedic surgical care worldwide. There was much to learn from this forward-thinking Boston physician in regard to the 21st century paradigm of accountability in medicine we now are experiencing.³

With the modern focus on value-based health care, there is now a renewed interest in the collection of PROs.⁴ A wide variety of both generic and condition-
specific PROs are used in current orthopaedic practice depending on the clinical context.⁵ Although yet to be ubiquitously integrated into all orthopaedic clinical care, the routine collection of PROs has a history starting in the late 1980s.⁶ Oncologists were the first to note that doctors could not adequately measure quality of life in patients receiving cancer treatment, and doctors had wide-ranging variability in their assessment of patient quality of life.^7,8 These observations were amplified in chronic conditions such as hip osteoarthritis (OA) in which the goals of treatment were to improve function, decrease pain, and prevent further health decline.

PROs are any reports coming directly from patients about how they function or feel in relation to a health condition and its therapy, without interpretation of the patient’s responses by a clinician or anyone else.⁹ In orthopaedic surgery, PROs are generally used to assess the response to an intervention as it pertains to the patient’s health (both physical and mental), function, and quality of life.¹⁰ PROs are generally categorized as (1) general health-related quality of life measures, which assess the impact of physical, mental, and social factors on the patient’s ability to perform activities of daily living; (2) overall quality-of-life measures, which quantify a patient’s overall well-being, satisfaction, and/or happiness with
life in general; and (3) system-specific and disease-specific outcome measures, which generally measure changes in pain and function outcomes for a specific body region (eg, hip) or a specific pathology (eg, hip OA). In general, assessing a system-specific or disease-specific PRO with a general or overall quality of life measure provides a more complete appraisal of a patient’s response to their disease or to the care they have received. A number of psychometric properties including validity (content, criterion, and construct), consistency, reproducibility (agreement), reliability, responsiveness, interpretability, and floor and ceiling effects can influence the usability of PROs.^11,12

PROs are designed for, and meant to be integrated into, routine clinical practice. Barriers for implementation into clinical arthroplasty practices include resources for realizing PRO collection (eg, staff time, technology, and expense), time required for collection, patient survey fatigue, real-time scoring and result availability, and suboptimal understanding in applying PROs to patient care.¹³ Language barriers and/or illiteracy can also become barriers for the use of PROs in practice.

PROs can significantly influence both patient evaluation and decision making when implemented into practice. A robust collection of PROs can help in several ways. First, PROs can be used to establish baselines for patients seeking treatment for hip OA. Well-functioning patients with limited pain may have higher (more normal) PROs regardless of the radiographic and examination criteria used to grade disease severity. These patients require significant discussion time preintervention to ensure that their expectations for treatment are attainable. Longitudinal post-THA PRO collection affords an opportunity to aid patients in understanding their trajectory of improvement or decline compared with similar patients. Importantly, the collection and use of PROs in clinical practice have been shown to improve patient experience.¹⁴

Health care value has been defined as the outcomes per episode cost of care, but the optimal approach to dependably and precisely assess outcomes has not been established.¹⁵ For hip arthroplasty, a hybrid assessment including both PROs and clinical outcomes might offer the best evaluation of episode outcome to be used in establishing value. The Centers for Medicare and Medicaid Services Comprehensive Care for Joint Replacement (CJR) integrates the collection of PROs into its assessment of care outcomes.¹⁶ Currently, the inclusion of PROs in this model is meant to determine the logistic feasibility to collect PROs in this patient population. The CJR collection periods (90-0 days preoperative and 270-365 days postoperative) may not be attainable within a routine academic practice.¹⁷ However, other payers are viewing the integration of PROs into an outcomes scorecard eventually destined for payment decisions.¹⁸ Although the definitive long-term use of PROs in hip arthroplasty practice is unknown, their implementation to improve patient care and affect payment seems inevitable.

As the DAA has become increasingly popular in the United States for primary THA, partially driven by the perception of an improved and more rapid recovery, it is important to track these patients closely as Codman had suggested.¹⁹ The intermuscular plane used during the approach may minimize abductor dysfunction postoperatively, and proponents believe that by sparing the posterior and lateral hip musculature during surgical dissection, patients may recover faster with fewer functional limitations, less dependence on assistive devices, and a lower dislocation risk.^{20,21,22,23,24,25,26,27} When looking specifically at the DAA, there are many facets of “function” that can be assessed postoperatively. Using PROs to follow these patients and compare them with patients who underwent THA through differing approaches affords us the opportunity to better understand its potential benefits in regard to joint-specific metrics and overall generic health-related quality of life.

The SF-36 was developed in 1992 from a multiyear, multisite study to explain variations in patient outcomes and is the most commonly used health-related quality-of-life measure in research.²⁸ The SF-36 is a set of generic, coherent, and easily administered quality-of-life measures. These measures rely on patient self-reporting and are becoming more widely used for the assessment of patient outcomes. The SF-36 yields eight scale scores and two summary scores specifically reporting on a physical component summary (PCS) and a mental component summary (MCS) score.²⁸ A shorter version, the 12-Item Short Form Survey (SF-12), is thought to provide adequate physical and mental health summary scores with less survey fatigue.^29,30 The Short Form 6-dimensions yields a preference-based score based on a subset of the SF-36 and SF-12 items that enables economic evaluation and calculation of quality-adjusted life-years.³¹ Despite being a general health and quality-of-life measurement tool, the Short Form Health Survey has been validated for use in OA.^32,33

The VR-36 was developed in 1999, with a 12-item version (VR-12) developed later.^34,35 The Veterans RAND Health Survey is a patient-reported global health measure that is used to assess a patient’s overall perspective of their health much like the SF-36 and its modified versions. The VR-36 implemented 5-point response choices for the scales “role limitation due to physical function” and “role limitation due to emotional function,” rather than the two choice options (yes or no) in the original RAND-36 from which it is was modified. This change results in a reduction of floor and ceiling effects of these scales. The VR-36 and VR-12 also contain two additional items that assess how the patient’s mental and physical health has changed over time.³⁶ The questions in this survey correspond to seven different health domains: general health perceptions, physical functioning, role limitations due to physical and
emotional problems, bodily pain, energy and fatigue levels, social functioning, and mental health. Like the SF-36, answers are summarized into two scores, PCS and MCS, which then provide an important contrast between the respondents’ physical and psychological health status.

In May 2002, the Director of the National Institutes of Health convened a series of meetings to chart a “road map” for medical research in the 21st century.³⁷ Over 5 years, a group network of clinicians, clinical researchers, and measurement experts were tasked to develop, validate, and standardize a way to measure PROs relevant across common medical conditions much like the SF-36. This tool was not intended to be disease specific but rather a global measure of health. Thus, the PROMIS (PROMIS Health Organization, River Forest, IL, USA, www.promishealth.org) and its shorter version, PROMIS-10, were developed.³⁸ The PROMIS-10 Global Health survey is a 10-item questionnaire that assesses generic health-related quality of life compared with normal values for the general population.³⁹ Developed by the US National Institutes of Health to evaluate health-related quality of life, the PROMIS-10 is contrasted against US normative scores. It measures five domains (ie, physical function, fatigue, pain, emotional distress, and social health) on a 5-point response matrix. The structure of the score offers greater responsiveness to changes in general health but has been used to evaluate a host of diseases including OA.^40,41,42 The PROMIS-10 is similar in scope to the VR-12, and a validated crosswalk can be used to convert scores from the VR-12 to PROMIS-10 scores.⁴³

Both the SF-36 and PROMIS-10 have been used to assess global health-related quality of life for several decades. The use of these surveys to measure outcomes in orthopaedics, specifically those related to DAA THA, is much less robust. In 2015, Higgins et al⁴⁴ published the first systematic review and meta-analysis comparing the DAA with the posterior approach (PA) for THA. This review emphasized the lack of methodologically rigorous, multicentered, prospective, randomized controlled trials (RCTs) with predefined reporting, standardized follow-up intervals, and outcome measures. Because of the heterogeneity of results among the included studies, the authors were unable to provide a firm recommendation as to whether the anterior approach or the PA was superior. In fact, only two included studies at the time included the SF-12 and one the SF-36.^23,45,46 No study found a difference in outcomes when comparing these global health metrics. At the time of publication, there was only one prospective RCT published in 2003 included in the analysis.²⁶ The study was a single-surgeon series (43 DAA and 44 PA) with the primary end point being the ability to climb stairs normally and walk at 6 weeks and 3, 6, and 12 months. The secondary end points included assessment by several outcome instruments including the visual analog scale for pain, the HOOS, and the Harris Hip Score (HHS). The benefits of the DAA were reflected in superior physical function measured in walking distance (unlimited and stairs), the HHS, and selected HOOS subscores at 6 weeks after surgery, but by 1 year the outcomes were similar between groups. There was no global PCS score like with the PROMIS-10 or SF-36 reported in this study, but this does represent early level 1 evidence supporting a short-term benefit of the DAA for THA.

There has since been a significant increase in the utilization of the DAA for THA. This has prompted an increased interest in outcomes after this procedure, yet large-scale prospective studies with global PROs are still limited. The use of joint-specific PROs such as the HOOS and HHS seem to be more common than global health metrics like the PROMIS-10 and Short Form Health Survey. Improved early pain scores without a difference in outcome scores between DAA and PA THA patients were reported in a single-surgeon RCT by Christensen et al.⁴⁷ Patients were noted to have earlier discard of walking aids in the DAA group, yet neither of the SF-12 subscales demonstrated significant differences between the groups after surgery.

Furthermore, in a prospective RCT of 54 patients, Taunton et al²⁵ sought to prospectively examine the clinical and radiographic differences between DAA and mini-posterior approach (MPA) THA. They showed the MPA was superior in terms of the SF-12 mental scores at a 3-week follow-up, yet the clinical significance of this is unknown because there were no differences found at later time points. Taunton et al⁴⁸ followed this study with a subsequent RCT of 116 patients randomized between the DAA and MPA with a specific aim of determining if the DAA had superior PROMs than the MPA. At 2 months and 1 year, there were no differences in SF-12 mental or physical component scores.

In a single-surgeon retrospective review evaluating patient-reported physical function between DAA (86 patients) and PA (135 patients) THA patients, the VR-12 PCS and MCS scores were assessed at 1 month, 3 months, and 1 year after surgery.⁴⁹ After controlling for relevant confounding variables, the DAA was associated with greater PCS improvement at 3 months compared with the PA. There were no differences in the adjusted PCS at either 1 month or 12 months. At 1 year after THA, there were no intergroup differences in self-reported physical function, although both groups had significant loss to follow-up at that time (35 DAA patients, 21 PA patients). In regard to the adjusted MCS change, the DAA group was noted to report worse outcomes at 1 and 3 months after surgery. The authors concluded that the DAA can be performed with expected results similar to those of the PA and that there may be a transient benefit to the DAA, including improved physical function at 3 months after surgery.

A prospectively collected series on 1457 THAs (1052 DAA and 405 PA) performed by six surgeons evaluated physical function improvement using the PROMIS-10 PCS.⁵⁰ The authors defined clinically
significant improvement as a 5-point change. DAA patients had higher unadjusted preoperative and postoperative PCS scores, yet there was no difference in the total PCS change after THA between approaches (8.1 vs 8.2, P = .798) or the number of patients with a clinically significant PCS change. Interestingly, despite the inclusion of surgeons who performed only the DAA or PA to avoid selection bias from a surgeon who might perform both approaches, the DAA patients in general started with higher preoperative PCS scores, suggesting perhaps that patients with higher baseline PCS scores may seek out surgeons who perform the DAA.

In a small retrospective review of 24 matched DAA patients with 24 PA patients, at the 3-month follow-up, the DAA group demonstrated significantly higher scores for the VR-12 Mental, VR-12 Physical, and SF-12 Physical scores.⁵¹ However, no significant differences were found regarding the SF-12 Mental scores. There were no reported outcomes at any other time point reported, and how patients were selected for the DAA or PA was not clear, which is concerning for the possibility of selection bias.

Early functional outcomes after DAA THA compared with the direct lateral (DL) approach were reported in a prospective RCT.⁵² The DAA group demonstrated significantly better improvement in the SF-36 scores for role limitation, bodily pain, and general mental health compared with patients in the DL approach group up to 1 year postoperatively. At 2 years, this difference was no longer seen and both groups demonstrated similar results. This same group published a subsequent RCT comparing functional outcomes between the DAA and DL approach with improved short-term functional measures again noted in the DAA group.²⁴ These results were noted to be the same at the 1-year follow-up between groups, and no measure of global health was performed.