This week I examined a Regenexx-C patient from 2008 who was still holding onto great relief despite being 2-3 years post procedure. Compare and contrast that to another patient of the same age and treated about the same time who had great results for only 12-14 months. Why? As with any medical procedure, finding out why a therapy failure occurs is almost as important as finding out why it works. In this case both patients initially responded and even the shorter relief patient still attained obtained longer relief than any other injection documented in the literature. In addition, most patients in this 2-3 year group are still holding onto their pain relief. However, what causes some patients to have shorter term relief? For purposes of this Regenexx-C analysis discussion, I’ll call the mid-term relief patient (12-14 months relief) MTR and the long-term relief patient LTR. Both patients had their initial Regenexx-C procedure about the same time. Both MTR and LTR were about the same age when injected. In addition, based on our review of the data from hundreds of treated Regenexx-C patients, there were no significant differences in outcome vs. age. LTR had slightly less severe osteoarthritis (KL grade 3 for LTR versus 4 for MTR), so this could have played a role. However, when we looked at arthritis severity on MRI in our Regenexx-C patients and compared that to outcome, it didn’t pan out that disease severity was a big factor predicting less robust results (i.e. most severely arthritic patients reported on average about a 10% less robust result). So while disease severity isn’t a huge factor, it could be a contributor to the failure. An obvious difference between these two patients is that MTR had 13 prior surgeries in the treated knee and has generalized arthritis in many more joints than LTR. We have observed clinically that patients with many prior knee surgeries respond less robustly, since they have less and less viable tissue in the knee with each surgery. However, the theories about the severity of MTR’s surgical knee fall apart when one examines that his two other less severe joints that were also injected also had only mid-term relief. That leaves only one obvious difference between these two patients, cell properties. This means MTR and LTR may have stem cells at different biologic activity levels. For example, we know that certain patients have a genetic predisposition to early onset arthritis. The upshot? These two patients likely have stem cells that are different in their ability to heal joints-just like some patients have great healing potential after surgery and others have less healing potential. While biologic assays of stem cells might help predict failures, this type of treatment prediction can only be accurate once these metrics are compared to real patient results. While animal modeling of this type of biologic activity might provide some clues, the only way to figure this one out is to treat many different types of patients and critically examine the results.