Valli - it's going to be tough to answer that definitively. I looked up his article published in 2010 in the British version of the Journal of Bone and Joint Surgery (a very reputable journal), and he reported success in his patients, but there wasn't a control group. Thus, it's tough to tell what percentage would have had total knee replacements had they not undergone a meniscal transplant. I'm not sure that other studies have confirmed that it's so easy to regrow cartilage with a local paste created during the initial surgery (there are other more involved methods such as "ACI" that are very involved and with narrow indications), and it may just be the microfracture that he's doing at the time of surgery.
Thus, in summary, it's tough to draw any real conclusions from one case-series study. Dr. Stone is certainly a very skilled surgeon, but one has to be careful drawing widespread conclusions from a case series without a control group.
Bookmarks