Cartilage regeneration builds a new knee, from the inside

Our Review Summary

 Anecdote and expert opinion triumphed over science and good journalism in a story on the regeneration of knee cartilage in USA Today.

The article focused on autologous chondrocyte implantation (ACI), an expensive procedure intended to regenerate articular cartilage in the knee involving two operations and an arduous 18-month rehabilitation process.

Unwarranted Assumption of Benefit

From start to finish, the article seemed to assume that ACI is a beneficial treatment. It examined the outcomes of ACI through the prism of a single patient, who is apparently making a good recovery 12 months after the procedure.

That the journalist chose to present the experiences of a celebrity—Olympic swimmer Dara Torres—only adds to the allure of this invasive therapy. But it is certainly open to question whether the experiences of a highly disciplined Olympic athlete are generalizable to other patients undergoing this treatment.

The article offered a misleading statistic from Torres’ surgeon, who stated that 92% of his more than 600 patients have had “success” with ACI.

Yet the USA Today story never defined the indications for surgery in these patients— or what “success” meant.

No Mention of Scientific Evidence

In an era of evidence-based journalism, the article went astray in never citing a single scientific study or attempting to quantify the expected benefit of ACI.

It didn’t specify the availability or costs (an estimated $20-$35K) of this procedure. It didn’t address specific treatment alternatives for cartilage damage.

It didn’t discuss the possibility of adverse effects related to ACI. Yet in some studies, up to 50% of patients who opted for ACI have had to undergo an additional surgical procedure for cartilage problems down the road. (Genzyme, Highlights of Prescribing Information, Genzyme.com)

Two outside experts did offer some tempering remarks but didn’t actually question the effectiveness of ACI. And like the other contributors to this article, they didn’t cite a single scientific study.

What Does the Scientific Evidence Say?

A few sentences on the scientific evidence base for ACI would have brought the entire article into focus—and provided a real benefit for individuals considering this procedure.

And what does that evidence show? The most recent systematic review found evidence that ACI can provide benefit over the short-to-intermediate term. So its long-term effectiveness hasn’t been established. (Harris JD et al., AACI: Systematic Review, JBJS, Sept 15, 2010)

It is not clear if ACI is superior to many other common treatments for pain and dysfunction related to articular cartilage damage. Well-designed randomized trials comparing ACI to usual care would be valuable. 

So in short, while the evidence on ACI is promising, the jury is still out. This observation should have been the starting point for the USA Today article.

 

Why This Matters

 Identifying treatments that can heal injuries to knee cartilage is something of a Holy Grail in musculoskeletal medicine.

Hyaline articular cartilage plays a vital role in the function of the knee joint, acting as a shock absorber and mechanical interface on the surfaces of the bones that meet in this weight-bearing joint.

Articular cartilage has a limited ability to heal. So in the absence of effective treatments, cartilage defects are to some extent permanent injuries and potential on-going mechanical triggers for knee degeneration.

Not all articular cartilage abnormalities lead to pain and dysfunction.  And it is not completely clear what differentiates pain-free from painful abnormalities.

However, even isolated cartilage defects can lead to vexing symptoms and the accelerated progression of knee degeneration. And when they occur in a knee with extensive degeneration their effects can be even more debilitating.

Though there are numerous treatments for articular cartilage damage, it is not yet clear that any of them can return the knee to full health and alter the natural history of symptomatic knee degeneration.