I am agonizing over the decision whether to have both my knees replaced at the same time or do them one at a time. How do other people make this decision?

Like you, many patients with painful arthritic knees wrestle with the decision to have them replaced one at a time (two separate surgeries and rehab) or both at the same time. The proposed advantages of the simultaneous bilateral knee replacements are decreased costs and shorter recovery time.

Some people make the decision simply based on economics (i.e., based on the amount of any out-of-pocket expense between the two procedures). A recent study showed that the difference in overall costs is significant: $43,401 for simultaneous procedures compared to $72,233 for staged procedures (almost double). This can add up to quite a bit of difference in out-of-pocket expenses.

You may find the results of a recent study of interest. 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.

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). The results (or outcomes) were just as good between the staged (one-at-a-time) approach and the simultaneous (both done together) method.

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. But this study 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).

This cost analysis showed the economic benefit of simultaneous procedures. Replacing both knee joints at the same time is both safe and effective. Data analyzed provides quality comparative evidence that can guide physicians and patients when faced with this decision.

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. Your surgeon will make this assessment and advise you as to whether or not you qualify for simultaneous replacements. You will want to discuss this decision with him or her as there can be other considerations in each individual case.