Based on my experience, 2 tubes of Radiesse injected to each hand should have produced more of a result. However, you should find out whether the larger 1.5 cc syringe or the smaller 0.8cc was utilized. Nonetheless, everyone is different and what works for most people unfortunately does not work for all. I would go back to your doctor and discuss your results.
4 syringes of Radiesse should have given you much more volume. You should see if the radiesse was diluted or if this is truly what was injected. If you have an area to harvest fat, this may be a better option for you as it would give you more volume and may last longer. I suggest seeing a filler expert for treatment. Veins can also be treated with sclerotherapy which can really rejuvenate the hands in some cases. You should see if you are a candidate. Best, Dr. Emer.
Radiesse comes in 0.8cc and 1.5cc syringes. We usually use 1.5cc per hand, sometimes a little more. If you have low Calcium levels in your blood, Radiesse (which is Calcium Hydroxyapatite) may break down more quickly. Check your calcium levels. If they are normal, I would question the amount of Radiuses in the "syringes" and make sure that they were not diluted. Good luck and be well.
Radiesse is a stimulatory filler so it may take some time to see full effects. Take before and after photos and speak to your injector about your concerns.