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90-day and 10-Year Risks Associated with Hip Replacement

Did you know that two-thirds of all adults who have a total hip replacement also have high blood pressure? And many patients getting a hip replacement have what's called multiple comorbidities -- in other words, lots of other medical problems.

Besides hypertension, heart disease, high levels of cholesterol, and a past bout with cancer head the list of comorbidities. And the list goes on: heart arrhythmias, lung disease, urinary tract infection, diabetes, obesity, anemia, rheumatoid arthritis, depression, dementia, and many more.

According to a recent study, the presence of these risk factors increases the chances of periprosthetic infection (around the implant) and even death. In the first 90-days after surgery, up to one per cent of patients die as a result of complications. A slightly higher percentage (up to two per cent) of patients develops an infection in or around the implant during the first 10 years after surgery.

Surgeons would like to erase those problems but how? This study provides the first step: identify the risks. Then look for a way to reduce or eliminate them. If the surgeon doesn't even know there's a link between some of these comorbidities and infection (or worse yet: death), then he or she won't necessarily be looking out for them as major risk factors.

This study not only identified the risk factors, it also quantified them. To quantify something means to give it a number that helps put the risk into perspective. So for example, patients with rheumatoid arthritis having a hip replacement were 1.7 times more likely to develop a periprosthetic infection. Obesity and blood clots had a similar hazard ratio.

Two tables were included in the article. One listed the risk factors for prosthetic joint infection (and their hazard ratios). The other presented hazard ratios for comorbid conditions linked with death in the first 90-days postoperatively. Those hazard ratios ranged from 1.3 for heart arrhythmias up to 1.7 for rheumatologic diseases.

Risk factors studied in association with death in the first three months following hip replacement were as low as 0.62 for high cholesterol levels. That actually places high cholesterol as a condition that decreases the risk of mortality (death). But dementia (2.04), metastatic cancer (3.14), and congestive heart failure (2.11) were much higher. And many patients had more than one health concern. The risk of combined medical conditions on infection and/or mortality was not calculated.

The surgeons involved in this study agree that the numbers of patients who die in the first 90-days or who develop a hip joint infection in the first 10 years are small but important. If you ever become a patient in the one to two per cent who develops these serious problems, it becomes a matter of great importance. Surgeons' attention to these matters is appreciated by all patients undergoing hip replacement.

Reference: Jennie McKee. Quantifying the Risks of THA. In AAOS Now. January 2011. Vol. 5. No. 1. Pp. 9-10.