Hi Joăo
You probably have read of a very small phase I trial of a 12 patients who had long standing tennsis elbow that didn't respond to treatment. The treatment involved one injection of a culture of collagen-producing cells derived from skin fibroblasts
http://bjsm.bmj.com/content/43/4/293.full
The results from the trial are promising as 11/12 both reported benefits and demonstrable benefits on a number of tests that examined the quality of the tendon.
Phase I trials like this are designed to test the safety of the procedure as it is the first time an experiment of this type has been conducted on humans. It is not designed to test the effectiveness of the treatment as it is too small and there was not control group or sham group who believed they were getting a treatment but didn't. Furthermore the people who conducted the testing were aware of the procedure the patients went though and this introduces bias. It is a sad fact of life that more often than not such treatments turn out to be less effective when good quality clinical trials are conduted.
It will no doubt be a while before such a treatment has been shown to be worthwhile and will become available. The long term effects of the treatment remain unknown. For example could the injection induce cancers later.
If you do find an institution providing such treatment I would approach it with great caution. It would be unethical for such an institution or Dr to offer such treatment and the chances are the place is looking for making some big money and may not be offering truly valid stem cell therapy.
I do appreciate thetennis elbow is some times difficult to treat. However there are a number of treatments in physiotherapy that seem to work in the long term. The other option is corticosteroid injection which can be effective , particularly in the short term. How long have you had the problem and what treatment have you had so far?
In addition I wonder if the diagnosis is right? You usually don't have both golfers + tennis elbow + ulnar nerve involvement although it is possible.