How Bad are Bipolar Articular Cartilage Lesions of the Knee, Really?
We won't fib to you, they're not great — but maybe not as bad as you thought; or maybe unipolar lesions don't do quite as well as we hoped . . . ?
What’s the Claim?
A registry-based study on articular cartilage restoration procedures in the knee (most commonly autologous chondrocyte implantation [ACI]) that compared unipolar to bipolar lesions found:
- A surprisingly low percentage of patients in either group improved by a clinically important margin. Even 2 years after surgery, only 46% of patients with bipolar lesions and 65% of patients with unipolar lesions improved their KOOS scores by the minimum clinically important difference (MCID) of 10 points.
- No clinically important difference between unipolar and bipolar lesions in the KOOS score at 24 months, and no differences between the groups at any other time point from 6 to 36 months.
- No between-group difference in the risk of reoperation (8% in the bipolar group versus 4% in the unipolar group; p = 0.26) or the time to reoperation (17 versus 32 months, respectively; p = 0.23).
On balance, the bipolar lesions did not do nearly as poorly as expected and in most important respects were little different from the unipolar lesions, though a lower percentage of them improved by a clinically important margin at 2 years. Our summary differs from that of the authors, which is important because the authors claimed a number of differences that fell below the MCID — meaning patients probably wouldn’t care about or notice them — as well as some that were not borne out by their own analyses (using language like “this difference was not statistically significant,” which is misleading in this context).
