I’ve heard that if I have both knees replaced at the same time (for severe arthritis), the cost is less but the risks are higher. What can you tell me about this?

As you point out, the proposed advantages of the simultaneous bilateral knee replacements are decreased costs and shorter recovery time. Previous studies have reported more complications with simultaneous knee replacements compared with staged procedures. Problems such as gastrointestinal complications, blood clots, heart attacks, and even death can occur.

A recent high-quality study has some information that may be helpful to you. Researchers at the University of North Carolina (Charlotte) and the OrthoCarolina Research Institute (also in Charlotte, North Carolina) took on the task of doing a cost-utility and cost-effectiveness study. They used the Nationwide Inpatient Sample data to compare the results of 24,574 cases of simultaneous knee replacements with 382,496 patients who had unilateral (one-at-a-time) procedures.

They found no difference in the overall rate of complications between these two approaches. In fact, for minor, major and in-hospital mortality (death), simultaneous procedures had lover complication rates. For example, the major complication rate for the staged group was 2.36 per cent compared with 1.49 per cent among the simultaneous group. The minor complication rate was 8.98 per cent (staged group) versus 6.84 per cent (simultaneous group). The number of in-hospital deaths was slightly higher in the simultaneous group (0.2 per cent versus 0.18 per cent for staged bilateral total knee replacements).

Measures used to compare the outcomes included perioperative complications (minor, major, and mortality), hospital costs, rehabilitation costs, anesthesia costs, and health utilities (visits to the surgeon, primary care physician, physical therapist). Most striking was the difference in overall costs: $43,401 for simultaneous procedures compared to $72,233 for staged procedures (almost double).

The researchers concluded that the results (or outcomes) were just as good between the staged (one-at-a-time) approach and the simultaneous (both done together) method.
This cost analysis showed the economic benefit of simultaneous procedures. Replacing both knee joints at the same time was determined to be both safe and effective.

Although there is a risk of increased complications with simultaneous procedures, exposure to only one anesthetic, decreased recovery time, shorter hospital stay, and lower costs may outweigh the risk. Older adults with serious health problems may not qualify as candidates for the simultaneous replacement of both knees.