Simultaneous Bilateral Total Knee Arthroplasty: What Is the Value? Commentary on an article by Susan M. Odum, PhD, and Bryan D. Springer, MD: "In-Hospital Complication Rates and Associated Factors After Simultaneous Bilateral Versus Unilateral Total Knee Arthroplasty".

Abstract

Commentary Total knee arthroplasty has long been shown to be both safe and efficacious for the treatment of degenerative conditions of the knee—relieving pain, restoring function, correcting deformity, and providing measurable improvements in quality of life. Total knee arthroplasty also has been demonstrated to be very cost-effective from a societal perspective, with estimates between ten and twenty thousand dollars per quality-adjusted life year (QALY)1. Frequently, patients present with bilateral symptomatic disease and deformity, prompting patients and surgeons to consider simultaneous bilateral total knee arthroplasty. The number of total knee arthroplasties performed and rate of utilization in the United States has grown exponentially over the last several decades. In fact, more than 700,000 were performed in 2010, with projections of more than three million total knee arthroplasties expected to be performed annually by 20302. The surgical demand creates major financial strains on the American health-care system and, in part, is responsible for the pay-for-performance measures enacted by the Centers for Medicare & Medicaid Services (CMS) and the recent public reporting of outcomes for total hip and total knee arthroplasty surgery. Simultaneous bilateral total knee arthroplasty has represented a consistent 4% to 6% of total knee arthroplasties performed annually in the United States1,3,4. Despite a lengthy history of surgeons performing simultaneous bilateral total knee arthroplasty, there continues to be debate about the indications for the procedure and concern regarding its overall safety. Those surgeons who support the use of simultaneous bilateral total knee arthroplasty cite decreased cost, improved recovery time, the utilization of a single anesthetic, and equal functional outcomes when compared with staged bilateral total knee arthroplasty. Those surgeons who favor staged bilateral total knee arthroplasty cite increased mortality, both in-hospital and within thirty days of surgery, following the simultaneous procedure1,3-6. In addition, they note increased rates of cardiovascular incidents, venous thromboembolic events such as pulmonary embolism, and the increased need for perioperative blood-product transfusion associated with simultaneous bilateral total knee arthroplasty3,5. It is the safety and efficacy of simultaneous bilateral total knee arthroplasty, compared with unilateral total knee arthroplasty, that is the subject of the present study by Odum and Springer. The investigators queried the Nationwide Inpatient Sample (NIS) data set for the period of 2004 to 2007 using International Classification of Diseases, Ninth Revision (ICD-9) coding data to identify procedure, perioperative minor and major complications, as well as in-hospital mortality. As have many prior authors, they identified simultaneous bilateral total knee arthroplasty as being associated with significantly higher odds of in-hospital complications, both minor and major, as well as increased mortality3-5. The investigators identified demographic data, including age, sex, and race/ethnicity, the number of comorbid conditions, type of payer, and hospital volume as factors that significantly related to the relative assessment of risk. What is difficult to control for in many studies of a similar design is inherent surgeon selection bias when choosing patients in whom to perform simultaneous bilateral total knee arthroplasty. Despite attempts at statistical modeling for matched covariates or multilogistic regressions, that selection bias persists to influence the outcomes of this and similar series. Despite that, it is quite clear, in this investigation as well as in others, that perioperative complication risks and mortality risk are increased with simultaneous bilateral total knee arthroplasty when compared with unilateral total knee arthroplasty3-5. Far fewer investigators have identified minimal or no difference in risk, and those more favorable studies, likewise, are often subject to some degree of physician selection bias. It is possible that, without this referenced selection bias, the true perioperative complication risk and risk of mortality from simultaneous bilateral total knee surgery would be greater than that identified in the present study and similar investigations. Considering the facts as presented, and this interpretation, it is reasonable for surgeons to choose to “do no harm” and argue for unilateral and/or staged bilateral total arthroplasty when caring for their patients. In the current era of value-based purchasing and assessment of outcomes for total knee arthroplasty, it is incumbent upon us to consider the evaluation of simultaneous bilateral total knee arthroplasty on a value basis. Value is defined as the quality, or outcome, of a medical procedure as it relates to the cost incurred in achieving that outcome. Cost-utility measures such as that performed by Odum et al.1 would imply that, on a broad scale—for instance, the perspective of CMS—the cost difference between simultaneous bilateral and staged bilateral total knee arthroplasty, without an identified difference in outcome as measured by QALYs, would result in enhanced value for simultaneous bilateral total knee arthroplasty. However, this is broadly applied through the perspective of health-care systems and the provision of care for society as a whole. It does not account for the perception of value from an individual hospital’s perspective, physician’s perspective, or, most importantly, the patient’s perspective. Hospitals may perceive the value of simultaneous bilateral total knee arthroplasty differently, as it is associated with an increased likelihood of perioperative complications such as venous thromboembolism and cardiovascular incidents, which are now publicly reportable outcome measures of quality. At some time in the future, this may have negative consequences with regard to reimbursement and the ability to negotiate bundled payment strategies for health-care institutions and physicians. Furthermore, although it has not, to my knowledge, been the subject of study, it is reasonable to surmise that the increased risk of complication with simultaneous bilateral total knee arthroplasty may negatively impact readmission rates and even play a role in increased medical liability exposure. Most physicians—other than those rare individuals who have well-managed systems in place to safeguard their patients and have fairly assessed their simultaneous bilateral total knee arthroplasty outcomes, finding them to be equivalent to unilateral—are likely to have a perspective similar to that of their hospitals. Most important, many patients, when faced with the option of choosing an elective surgical procedure that increases the likelihood of serious perioperative complications or mortality, will rightfully fail to see the benefit of increased risk, and are, therefore, more likely to choose a procedure with less risk involved. For the moment, the value of simultaneous bilateral total knee arthroplasty is clearly linked to the perspective from which the data are viewed. When examining value from various perspectives, it is relatively easy to define cost, but more difficult to define outcomes, except at the broad societal level as measured by QALYs. While in some cases, value is subject to individual interpretation, at the individual patient level, the true risk and cost of a compromised outcome, due to medical complications and mortality, depends on our ability to accurately risk-stratify patients. Unfortunately, with the current information available, we are able to identify individual risk factors but not able to calculate individual patients’ true risk for perioperative complications and mortality after simultaneous bilateral total knee arthroplasty. Large, national databases with Level-IV data may assist us in more accurately risk-stratifying individual patients in the future. Similarly, randomized, prospective investigations comparing simultaneous bilateral total knee arthroplasty with staged bilateral total knee arthroplasty could clarify true risk potential and identify the optimal time interval for staged total knee arthroplasty in order to minimize that risk. Until that time, I am left with the same impression as that offered by the Consensus Conference on Bilateral Total Knee Arthroplasty, in which 81% of the interdisciplinary steering committee of surgeons, anesthesiologists, internists, and epidemiologists agreed that same-day simultaneous bilateral total knee arthroplasty was associated with a higher risk of complications when compared with unilateral or staged total knee arthroplasty6. In addition, 93% of participants acknowledged that there is a need for a multicenter study group that can pursue additional research to assess clinical risk6. With the current data available and the considerable consensus of multispecialty opinion, it appears as though orthopaedic surgeons should, for now, recommend and choose the pathway that will provide the most predictable outcome for patients desirous of bilateral total knee arthroplasty—staged procedures over time.