Even for Healthy Patients, Bilateral Simultaneous TKA May Not Be Safe
With surgeons offering total knee arthroplasty (TKA) to increasingly younger patients with osteoarthritis and other degenerative conditions, the idea that both knees could be replaced during the same operation is appealing. Many of these patients still work, and by undergoing surgery only once, they minimize time off from work and, theoretically, minimize the risk of complications from a second anesthesia and hospitalization.
Not to mention the potential for cost savings.
The literature is mixed on whether bilateral simultaneous TKA is a good idea, however. Some studies have shown that it is safe, with no difference in complications compared with unilateral TKA, [1-4] while others have found an association between bilateral simultaneous TKA and increases in: [5-9]
- Intraoperative blood loss requiring transfusion
- Deep vein thrombosis
- Cardiorespiratory complications
- Neurologic complications
- Periprosthetic joint infection
In a retrospective review of data from the National Inpatient Sample, Remily et al  identified a trend in the type of patient being offered bilateral simultaneous TKA: Between 2009 and 2016, these patients became progressively younger and healthier, which the study authors speculated “likely resulted from improved patient assessment and management.” In addition, the number of patients who had bilateral simultaneous TKA decreased from 5.6% of bilateral TKAs in 2009 to 4.0% in 2016. 
Anecdotally, the latter finding was what surgeons at Cleveland Clinic in Ohio had been seeing in their area: Their peers seemed to be pulling back from offering bilateral simultaneous TKA. Robert M. Molloy, MD, Vice Chairman of Orthopedics and the Director of Adult Reconstruction at Cleveland Clinic, said this could be a response to recent research showing that performing bilateral TKA under the same anesthesia may put the patient at a higher risk for complications.
However, as noted by co-author Nicolas S. Piuzzi, MD, from the Cleveland Clinic Musculoskeletal Research Center and Cleveland Clinic Joint Preservation Center, research has also shown that about 40% of TKA patients subsequently undergo TKA of the contralateral knee within a decade,  suggesting that bilateral simultaneous TKA may be of benefit for some patients.
With indications for bilateral simultaneous TKA seemingly narrowing, Dr. Molloy, Dr. Piuzzi, and their colleagues from Cleveland Clinic wanted to know: Is there a subset of patients in which bilateral TKA can be safely performed in a single operation?
To find out, they compared 30-day mortality and complication rates in bilateral simultaneous TKA and unilateral TKA patients from the American College of Surgeon’s National Surgical Quality Improvement Program (NSQIP) database, which includes more than 100 data points on surgical patients from hundreds of hospitals nationwide.
Their findings were presented in November 2020 at the annual meeting of the American Association of Hip & Knee Surgeons and then published online ahead of print by The Journal of Bone & Joint Surgery in December 2020.
The investigators identified 323,510 TKAs performed between 2012 and 2018: 315,219 unilateral TKAs and 8291 bilateral simultaneous TKAs. They then matched the unilateral and bilateral TKA patients 1:1 based on morbidity probability, a cumulative variable that includes:
- Demographics, such as ethnicity, BMI, sex, and age
- Comorbidities, such as dyspnea, hypertension, diabetes, and congestive heart failure
- Laboratory values, such as albumin, creatinine, white blood-cell count, and hematocrit
Patients in both groups – bilateral simultaneous TKAs and unilateral TKAs – were then separated into quartiles according to their morbidity probability, with the first quartile being the healthiest and the fourth quartile being the least healthy patients. Complications and mortality rates were compared in each quartile to answer the Cleveland Clinic’s question: Is there a subset of patients in which bilateral TKA can be safely performed in a single operation?
The researchers found that, at least with this database, the answer is no: Overall, patients in the bilateral simultaneous TKA group were 3.6 times more likely to experience any complication and 2 times more likely to experience a major complication than patients in the unilateral TKA group.
This significantly increased risk for complications was true regardless of health status:
- First quartile: Bilateral TKA patients had a more than a 3-fold increased risk for all complications and more than a 2-fold increased risk for major complications.
- Second quartile: Bilateral TKA patients had a more than a 4-fold increased risk for all complications and 2-fold increased risk for major complications.
- Third quartile: Bilateral TKA patients had a more than a 4-fold increased risk for all complications and nearly a 3-fold increased risk for major complications.
- Fourth quartile: Bilateral TKA patients had a more than 3-fold increased risk for all complications and 57% increased risk for major complications.
A complication was considered to be a “major complication” if it required a complex surgical or medical intervention, if it was a threat to the patient’s life, or if it caused functional impairment, as defined by Pulido et al. 
No difference in mortality was detected between groups in any of the quartiles.
Although the study did not identify a subset of patients for whom bilateral simultaneous TKA is safe, Dr. Molloy emphasized that surgeons do not have to stop offering the procedure when it is appropriate. “I don’t think that this study is the definitive end-all to put question to rest,” he said.
Rather, it provides additional information for surgeons and their patients to use in a shared decision-making scenario. No surgery is without risk. The study findings, Dr. Molloy said, will help surgeons educate patients about the risks of bilateral simultaneous TKA so that they can decide together if the benefits for that individual patient outweigh the potential risks.
Like Dr. Mollloy, Dr. Piuzzi recognizes the need for more research on the safety of bilateral simultaneous TKA, acknowledging that the NSQIP database has some limitations. For example, it does not follow patients longitudinally, so it can identify associations but not necessarily causality. Dr. Piuzzi said that he and his colleagues are using a different database to further explore the safety issue.
Warren JA, Siddiqi A, Krebs VE, Molloy RM, Higuera CA, Piuzzi NS. Bilateral Total Knee Arthroplasty May Not Be Safe even in the Healthiest of Patients (Paper 30). Presented at the 30th AAHKS Annual Meeting, November 5-8, 2020, Dallas, Texas.
Warren JA, Siddiqi A, Krebs VE, Molloy R, Higuera CA, Piuzzi NS. Bilateral simultaneous total knee arthroplasty may not be safe even in the healthiest patients. J Bone Joint Surg Am. 2020 Dec 24;Publish Ahead of Print. doi: 10.2106/JBJS.20.01046. Online ahead of print.
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