Two Knees at Once: More Clarity on Pluses and Minuses

LAS VEGAS — Simultaneous bilateral total knee arthroplasty (SBTKA) is a feasible option for many patients, including those who are severely obese, according to authors of a pair of new studies that examine complications from the procedure.

In a retrospective analysis of 133 patients undergoing SBTKA (average age 60, 83 female) from 2013-2016 at three academic institutions, there was no link between body mass index and length of stay or blood loss, according to senior author Fred D. Cushner, MD, of Northwell Health in Bayshore, New York, and colleagues.

Patients with higher BMI, however, needed longer surgeries, and the morbidly obese (BMI 40 or higher) had a much higher complication rate (44%) than the non-obese patients (21%, P=0.034). On the other hand, most complications were minor, and there was no difference between obese and non-obese patients in the rate of major complications, Cushner told MedPage Today.

“A bilateral knee in an obese patient can be done with acceptable risk. We were doing BMIs over 40,” said Cushner.

SBTKA was also compared with more conventional staged procedures in a study led by Mark P. Figgie, MD, of the Hospital for Special Surgery and Weill Cornell Medicine in New York City, which found higher rates of some complications with simultaneous surgeries but lower rates of others.

Using a national insurance database, Figgie and colleagues tracked 1,637 simultaneous and 6,110 staged bilateral TKA procedures from 2007-2015. They found that transfusions and readmissions were higher in the simultaneous group, while infections and mechanical complications were higher in the staged group. Those whose staged surgeries were less than 3 months apart had higher levels of manipulation under anesthesia.

Most notably, readmission rates at 90 days were much higher in the simultaneous group compared to staged groups (OR 0.11, 0.30, and 0.35 for procedures staged over 3 months, 3-6 months and 6-12 months, respectively; all P<0.05). And mechanical complications at 90 days were higher in the staged groups (OR 3.15, 3.29 and 3.32, respectively; all P<0.05).

The findings shed light on a national controversy over whether the benefits of SBTKA — less time for the patient to spend “laid up” and potentially less cost — outweigh the risks. Severe obesity is generally considered a contraindication to simultaneous procedures, although not absolute.

Which patients should get both knees replaced at once? “We’re constantly trying to figure out who the ideal patient is, who should get it and who shouldn’t get it,” said Figgie.

One big question mark has surrounded simultaneous bilateral knee replacements in obese patients. “Some people are afraid to operate on the severely obese,” Cushner said. “Most people will do a [patient with a] BMI of 30, there are some [who] won’t do over 35, and some have a hard stop at 40.”

Cushner is among those who maintain no firm upper limit to BMI. He agreed that patients’ obesity must be considered and risk stratification is needed. Still, he said, “you shouldn’t have a hard stop” — a BMI beyond which no procedure can be performed.

Figgie suggested that the higher transfusion rates with SBTKA aren’t a significant problem. “We already know that patients undergoing two procedures at the same time are bleeding a little more since they’re bleeding from both sides.”

As for higher readmission rates, he said the simultaneous procedures are “a bigger hit to the system,” and patients don’t tend to get moving as quickly post-surgery because both knees are affected.

The findings, Figgie said, suggest that staged bilateral procedures should be divided by at least 3 months. “It takes a while for the patients to recover mentally, physically, emotionally,” he said. “Going through a replacement isn’t easy.”