Revising the Statistics

The word that orthopedic patients least want to hear is “revision.” The very thought of surgery to replace an implant because problems have developed can be frightening. Who, in the universe of patients, do we expect to see on the receiving end of this bad news? If you guessed “the elderly” you would have been wrong. The reality of who is hearing “revision” may come as a surprise. Demographic trends in hips and knees have been changing, and these changes have left their marks on the orthopedic world.

Revisions can be ugly business. The revision procedure is more complex and difficult to perform than is the original primary procedure. Complications include a chance of the new implant to loosen, dislocate, become infected, and there is almost always bone loss. No patient wants to face a revision procedure any sooner than he has to. But the numbers show that younger patients are, in fact, increasingly suffering such a fate.

Hip and knee replacements were originally thought of as treatments for grandparents. According to the Healthcare Cost and Utilization Project released by the Agency for Healthcare Research and Quality (http://hcupnet.ahrq.gov/), a decade ago in 1998, over 70.0% of total hip replacement (THR) patients were age 65 or older and 65.8% of total knee replacement (TKR) patients were also 65 or older. However, as of 2006, these numbers have changed dramatically. Total hip replacement patients over the age of 65 now comprise only 54.4% of the procedures performed and total knee replacement patients of the same age group have dropped to 59.2%. 

So why are these percentages changing? Are orthopedic surgeons seeing fewer patients 65 years and older each year? That isn’t what the numbers are telling us. The numbers are percentages of the total which, taken by themselves, can be misleading. The fact is there has been continued growth in patients over 65 through 2005. There has been even faster growth in the number of patients under the age of 65. Using the PearlDiver database, we are able to take a closer look at what is happening with this market. As shown below, from a sample of over 40,000 hip and knee patients, there has been an astounding percentage growth in just the past several years.

Table 1: Growth in Hip and Knee Market for Patients Under the Age of 65

In comparison, according to The American Academy of Orthopaedic Surgeons, from 2004 to 2005 the total market for hips grew by just 2.2%, and the total market for knee replacements grew by 9.5%. From a demographic standpoint, the number of patients under the age of 65 are simply growing at a faster rate.

These numbers clearly substantiate claims that the average age of patients is continuing to drop. And why wouldn’t it? The implants are improving, the incisions are becoming less invasive, and the amount of time a patient stays in the hospital is decreasing. The more opportunity implants provide for an improved quality of life, the less incentive patients have to tolerate pain and delay the procedure.

What effect does this shift in the age of patients have on the number of revisions performed? Diving deeper into the PearlDiver data, it becomes apparent which age groups are experiencing the largest increase in the number of revisions performed. With respect to total hip revisions from 2004 to 2006, all age groups ranging from 40 to 64 showed significant increases. Revisions on patients aged 60 to 64 increased 24.7%, revisions on patients 55 to 59 grew 50% and revisions on patients age 50 to 54 grew 25%. Revisions on patients ranging in age from 45 to 49 grew by 17.3%, and those performed on patients between the ages of 40 to 44 grew 56%!

Not to be outdone, total knee replacement patients requiring a revision from 2004 to 2006 also increased at a rapid rate. The numbers of patients between the ages of 60 to 64 receiving knee revisions grew 36.9%, while revisions on patients between the ages of 55 to 59 grew 25.2%. Patients between the ages of 50 and 54, who had a revision procedure, grew an incredible 71%! Even revisions on younger patients between the ages of 45 to 49 increased at a rate of 15.6%.

The age of patients receiving an increased number of revisions isn’t the only surprise. Exploiting the resources of the PearlDiver database, several more subtle differences within the market have also been unearthed. First, as shown below in Table 2, there are discrepancies between the numbers of procedures performed on males versus females. The “All Ages” category is compiled from the Healthcare Cost and Utilization Project released by the Agency for Healthcare Research and Quality and represents the percentage of procedures on patients of all ages for their respective gender. This number is then compared to data derived from the PearlDiver database, which is able to isolate gender and specific age ranges for comparison.

Table 2: Percentage Based on Gender

By eliminating those patients over the age of 65, several interesting differences become apparent. There is a shift of about 10% in the total hip replacement category. Focusing solely on patients under the age of 65, men receive a greater percentage of hip replacements than women. Yet this is not true of hip revisions. It would be reasonable to expect that because men under 65 receive 8% more hip replacements than women that they would also receive more hip revisions as well.  Instead they receive 6% less.

Although less dramatic, there is also a difference in the demographics of knee replacements. With respect to the primary total knee replacement procedure, there is a 3.4% increase in males and a 3.0% decrease in females, slightly narrowing the majority of procedures on women. Yet the number of knee revisions performed shows a greater shift between genders, increasing 5.4% in males and decreasing 4.9% in females.

There is another twist to the demographics. The percentages set the expectation that females are more likely to receive a hip or knee revision than are males. Is that really the case?

We compared by gender the number of patients out of 100 who would require a revision. The table below shows that out of every 100 male patients under the age of 65 who received a primary knee replacement, 5.6 will require a revision. In contrast, 4.8 of every 100 female patients receiving a primary will require a revision.

Table 3: Patients out of 100 Under the Age of 65 Requiring Revision

By using the information within the PearlDiver database we can survey a random selection of patients sitting in the doctor’s office from a couple of perspectives. For patients under the age of 65, we are more likely to see a male rather than a female receiving a primary total hip replacement. But the females are more likely to be the ones there to get a hip revision. On a percentage basis, once a woman has had a primary hip procedure, she is more likely to receive a revision than is a male who has had a primary procedure (8.5% of females versus 6.6% of males).

However the same is not true for knees. From this data we see that women are more likely to have a primary total knee replacement than are men and that women receive a greater number of revisions. But the numbers show that on a percentage basis it is instead the male patient who after having a primary procedure is more likely to receive a revision (5.6% of males versus 4.8% of females). 

Now picture the orthopedic surgeon’s office. You can hear the bad news, “revision.” Looking at the patient, is he or she still the same person you expected to see?