Surprise, surprise: One of Amplitude’s fearless (if foolish) predictions for 2024 has proven out. “The commonly cited numbers about limb-loss prevalence—507 amputations a day, 186,000 a year, an overall population of 2.1 million US amputees—are based on 15-year-old data,” we wrote in our January edition. “New, more accurate estimates are due out this year.”
And here they are, courtesy of the Amputee Coalition and Avalere Health. The shiny new numbers appear in a paper titled “Prevalence of Limb Loss and Limb Difference in the United States: Implications for Public Policy,” which was published last week—about two months earlier than our forecast anticipated.
This long-overdue study is the first serious attempt since the George W. Bush administration to gauge how many Americans are living with limb loss/difference. It’s a huge step forward in building the data infrastructure necessary to achieve more affordable, effective, and equitable amputee care. “It gives health systems the data they need to invest in the services that would optimize outcomes for people living with limb loss and limb difference,” says Shelby Harrington, the study’s co-author and Avalere’s managing director of evidence and strategy. “Having the numbers really shows that there is a big enough population to justify that investment.”
Get the topline findings here, then download and read the whole thing from the AC website. Here’s what jumped out at us.
1. The limb-difference population outnumbers the limb-loss population.
Cutting to the chase: The AC’s prevalence study estimates there are a combined 5.7 million+ Americans living with limb loss or limb difference—a near-tripling of our previous understanding of the size of Amputee Nation. That total includes 2.3 million+ people with limb loss and 3.4 million+ with limb difference. (We’ll explain the plus-signs down below; just go with it for now.)
The estimated 2.3 million Americans with limb loss represents about a 10 percent increase over the previous estimate of 2.1 million, which was derived from data originally published in 2008 in the Archives of Physical Medicine and Rehabilitation (APMR). However, the APMR study made no attempt to count people with congenital limb difference; it only enumerated major limb amputations caused by trauma, cancer, vascular disease (including diabetes), infection, and so forth. The AC/Avalere study is the first serious, data-based attempt that we know of to count everyone, and it revealed a ginormous blind spot: The limb-difference population is much, much larger than anyone seems to have realized.
To tease out this distinction a bit more: Shaquem Griffin, a below-elbow amputee who appeared on our September 2023 cover, wouldn’t have been counted at all in the 2008 study; he was born with a congenital limb difference, so he wouldn’t have shown up in the data those researchers relied on. But Knox Gibson, another below-elbow amputee who graced the cover of Amplitude‘s November 2023 edition, would have been counted because he required amputation after a farm accident. Their lives are extremely similar—both have lived with limb difference since childhood, they use the same types of prosthetic devices and other adaptive technologies, they have similar healthcare needs, and they face the same challenges in navigating a nondisabled society. But one of them (Griffin) was completely invisible until now. The AC/Avalere study reveals just how massive that oversight was.
(BTW: Knox Gibson wouldn’t have been counted in the 2008 study either, because he doesn’t live in the United States. . . . but the basic point stands.)
2. Limb loss/difference incidence is way different from limb loss/difference prevalence.
According to the AC/Avalere paper, an average of 507,293 people lose a limb or are born with limb difference every year. Again, that’s a near tripling of the previously cited number (186K per year). At this rate, more than 2 million people have experienced limb loss/difference in this decade alone, and more than 7 million people have experienced it since the APMR paper was published. . . . but then, how can the overall population be only 5.7 million+?
There are two main reasons. First, many of those annual 507K limb-loss events are experienced by people who are already amputees—for example, people who lose a leg to the same vascular disease that previously caused amputation of their other leg, or BK amputees who require an AK revision—so those cases don’t increase the overall population. The second, more sobering reason is that the attrition rate among people with limb loss/difference is extremely high. The large number of new amputees each year is substantially canceled out by the number who pass away. The AC/Avalere study estimates that the mortality rate for people with limb loss (18.5 percent) is about 20 times as high as the rate for those with limb difference (0.9 percent) and the general population (0.8 percent).
“When we talk about incidence, we’re talking about a number of occurrences in a given year,” explains Harrington. “But when we’re talking about prevalence, that’s how many people in the US at any given moment are living with [limb loss/difference].” So 507K represents the annual incidence of limb loss/difference; 5.7 million+ is the prevalence. The numbers are related, but they have distinct meanings, so don’t mix them up. There will be a test. . . .
3. The new study aligns with prior projections about limb-loss population growth.
The 2008 APMR study was titled, “Estimating the Prevalence of Limb Loss in the United States: 2005 to 2050.” True to their word, the authors plotted a curve between those two years, projecting an increase from 1.6 million people with limb loss in 2005 to 3.6 million in 2050. (Again, that’s limb-loss only, excluding people with limb difference.) Their projection was heavily informed by rates of diabetes and obesity, with mortality rates factored in. According to their projection, the US limb-loss population ought to reach 2.2 million by the year 2020. The AC/Avalere estimate of 2.3 million+ is very consistent with the APMR projection. But . . . .
4. The “+” signs are necessary, because the current estimates are surely undercounts.
The new estimate is derived from insurance claims data, but the dataset doesn’t include every insured individual—nor any uninsured one. The core resources are Medicare files and the Invalon MORE2 Registry, a proprietary resource that encompasses a large chunk of private insurance plans, including managed Medicaid and Medicare Advantage plans. The MORE2 database doesn’t reflect a geographically representative sample of insurance plans, which may impact the estimates’ accuracy. Moreover, limb loss/difference data for military veterans and active-duty personnel aren’t included at all in this study, and those individuals may account for as much as 10 percent of the overall limb loss/difference population.
Despite these limitations, the new study has a more comprehensive data foundation than the one underlying the 2008 study, which was largely based on a sample of hospital discharge data. That study also undercounted, not only by omitting data from the military healthcare system but also by excluding limb difference from its analysis.
5. This is just the first step.
The AC/Avalere study is only meant to start the discussion, not to end it. It lays a foundation for new research, and it complements and provides context for other data projects that are already having an impact. For example, you can bet that advocates working on So Everybody Can Move legislation will be sharing these findings with lawmakers and citing it during testimony. It provides a useful reference point for the Limb Loss and Preservation Registry, which in an ideal scenario will eventually be able to yield hard counts of limb loss/difference incidence and prevalence.
Above all, this study might light a fire under the research community’s backside. “When you have this foundational data, you not only get the attention of regulators, policymakers, and payers, you also get the attention of other researchers,” says Harrington. “They say, ‘Wow, there’s a big, important question here. There are a lot of people whose lives are impacted.’ The decision makers start to think there is clear evidence that a positive investment can ultimately deliver better quality care and better outcomes at a lower cost. It really gives us a direction to look at and say: What can we as a healthcare system do to better serve these individuals and improve their lives?”