Factors That Influence Hip and Knee Replacement Outcomes

Physical therapist helping man with knee replacement
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Hip and knee replacement surgery are among the most common surgical procedures performed by orthopedic surgeons. One of the major goals for joint replacement surgery is to provide patients who undergo this procedure with a pain free, normal functioning joint that allows them to return to their desired activities. However, the other major goal is to ensure the safest possible treatment that minimizes potential risks and seeks to avoid any possible harm.

Many aspects of joint replacement surgery have improved over the past several decades to lower the potential for risks associated with surgery. One of the most helpful ways to limit risks associated with surgery is to be able to anticipate which patients and what interventions might be associated with the highest likelihood of harm.

Preventing Harm From Joint Replacement

Most people considering joint replacement are aware of some of the common risks associated with this type of treatment. Some of the more common risks include infection, blood clot, joint stiffness, persistent pain, among others.

In an effort to limit the potential of these possible complications associated with surgery, your surgical team will take a number of steps to try and prevent these problems. In addition, there are increasing efforts to attempt to identify which patients might be at the highest risk for potential complications, and take steps to try and lower the potential for harm prior to surgery in these specific groups of people.

The first step necessary is to try to determine what factors may lead to the potential of complications following joint replacement. In an effort to try to identify which of these factors are most important, there has been research investigating which patients are most likely to require readmission to the hospital within 90 days of their surgical procedure.

A recent study has investigated over 1500 patients who underwent hip or knee replacement, and try to determine which factors might lead to an increased likelihood of readmission in the first 3 months following surgery.

ASA Class

The research found that one of the most important risks associated with readmission to the hospital was a higher ASA score. The ASA score was developed by the American Society of Anesthesiologists to classify the fitness of patients undergoing surgical treatment. Initially there were five categories, and a sixth was subsequently added. In general, joint replacement might only be considered in categories 1 through 4.

The ASA classification rates patients as the following:

  1. Healthy person
  2. Mild systemic disease
  3. Severe systemic disease
  4. Severe systemic disease that is a constant threat to life

People who have an ASA score of 3 or higher have a much higher risk of re-admission to the hospital. These patients should be carefully evaluated prior to surgery, and steps should be considered to address the systemic diseases that are causing this increased risk of surgical intervention.

Discharge Location

As recently as the past few decades, nearly all patients undergoing joint replacement were sent to either a rehabilitation facility or nursing home following their inpatient hospitalization.

Over the last 10 years, the use of post-acute inpatient services has dramatically decreased. Part of the reason for this decline is the fact the people who go to either inpatient rehabilitation facilities or nursing homes have a higher chance of requiring readmission to the hospital. More patients are being sent home with home health services or outpatient physical therapy. In addition, some surgeons are starting to develop programs that allow for outpatient joint replacement surgery.

This shift in discharge plans for people having joint replacement is quite remarkable. As recently as the late 1990s, only 15 percent of patients went directly home from the hospital.

Today, well over 50 percent of patients for most hospitals, and in some hospital settings a much higher percentage, are going directly home from the inpatient hospital.

There are several reasons that may explain why patients who require post-acute inpatient rehabilitation may have a higher risk of readmission to the hospital. These tend to be more frail individuals, and sometimes have other medical issues. In addition, many surgeons have concerns about healthcare-acquired infections that can occur in these rehabilitation and nursing facilities. These reasons may contribute to the higher chance of requiring readmission after joint replacement.

Body Mass Index

The body mass index, or BMI, of people undergoing joint replacement surgery continues to be a valuable predictor of the likelihood of complications, including readmission to the hospital. People who have a BMI over 40 had shown higher risks of complication following joint replacement surgery including unplanned readmission to the hospital.

One of the most challenging aspects of BMI, is the ability to change BMI either before, or after, joint replacement surgery. People who have severe arthritis, and are obese, had a very difficult time trying to lose weight given their joint pain. On a positive note, there are methods of exercise and weight loss that can help some of these individuals. If you are motivated to lower your risk of complication prior to joint replacement surgery, discussed with her doctor some of the methods you can use to reduce your body mass index.

A Word From Verywell

Joint replacement surgery is a very safe and effective procedure. However, there are possible complications, some of which can have devastating consequences. For this reason, surgeons are becoming increasingly interested in predicting which patients have a higher chance of developing problems associated with surgical intervention, and then taking steps to lower this potential risk. It is important for people who are considering joint replacement to understand if they might have a higher risk of complication, and also learned the steps that they might be able to take to decrease their chance of having one of these complications occur.

Sources:

Varacallo MA, Herzog L, Toossi N, Johanson NA. "Ten-Year Trends and Independent Risk Factors for Unplanned Readmission Following Elective Total Joint Arthroplasty at a Large Urban Academic Hospital" J Arthroplasty. 2017 Jun;32(6):1739-1746. Epub 2016 Dec 27.

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