CORR Insights®: How Does Mortality Risk Change Over Time After Hip and Knee Arthroplasty?

Where Are We Now?

Total hip and knee replacements are well-established, cost-effective surgical procedures that decrease pain, increase function and mobility, and improve the quality of life for patients with osteoarthritis (OA). Patients generally undergo thorough medical assessment and risk mitigation before surgery, so that the surgical procedure and aftercare can proceed as smoothly as possible. Patients who have extensive medical comorbidities that cannot be adequately improved upon often are not offered elective major surgery like arthroplasty. This selection bias may account for the decrease in mortality observed in patients undergoing total joint replacement (TJR), compared to a matched cohort not undergoing the operation during the first few years after surgery [8]. However, less is known about the long-term effects on longevity after TJR of the lower extremity. Although mortality in the first few years after TJR has declined [3, 5, 6], recent evidence from several centers in North America and Europe observed that mortality after about a decade increases [2, 9, 10]. These findings seem counterintuitive; one presumes that healthier patients undergoing an operation for joint pain and limited function would subsequently become more active and enjoy the health benefits of a more vigorous lifestyle. Unfortunately, most patients who undergo joint replacement of the hip and knee do not increase their activity levels postoperatively [7]. Furthermore, most patients do not lose excessive weight after TJR [1]. These points are enormously important, as the Western population is aging, and increased numbers of joint replacements are being performed worldwide at substantial cost.

The study by Harris and colleagues [4] addresses whether mortality after hip and knee arthroplasty changes after the operation, compared to individuals not undergoing these procedures.

Where Do We Need To Go?

Accordingly, patients, medical caregivers, insurers and governmental agencies should be concerned about the potential excessive mortality after the first decade for patients undergoing TJR. Why is this increased late mortality occurring? Are there patient-specific factors, such as race, body habitus, specific comorbidities, prior and ongoing medications, lifestyle choices, or local environmental factors that contribute to this excess mortality? Are there surgical or implant factors that may be relevant, such as implant type, bearing materials, or method of fixation? Patients may have multiple joint replacements for OA of the hip, knee, shoulder, and other joints. Are the potential adverse effects of multiple joint replacements on patient longevity additive? Finally, the interaction between the patient and the implant must be considered. Are there subsets of patients in whom the response to the implant predicts not only the immediate clinical outcome but long-term biocompatibility and patient longevity? Answers to these and other pertinent questions will hopefully explain the observed findings of excess mortality of TJR after the first decade.

How Do We Get There?

Assuming the finding of excessive mortality late after TJR is evidence-based, the first step is to confirm the findings in populations with different nationalities, races, and cultures. Although national registries will play an important role in finding these patient populations, they alone may not have sufficient granularity to determine the intricate details of each patient’s medical history and lifestyle. Linkages among registry data, hospital databases, and even insurance company databases, under a privacy compliant umbrella, may discover specific factors that are predictive of the excessive mortality after the first decade post-TJR. With the advent of supercomputers capable of manipulating and analyzing “big datasets”, this goal should be possible. However, new algorithms will need to be devised to interrogate, extract, and analyze such big data sets. This goal will spawn new collaborations and partnerships among academicians (such as orthopaedic surgeons and epidemiologists), insurers, and governmental agencies. Perhaps this analysis will generate a meaningful explanation as to why excess mortality after the first decade post-TJR is observed.