Patients are prospectively evaluated basally and at 2, 6, and 12 months of follow-up using clinical subjective scores and objective parameters to determine clinical outcome (see 'Outcome measure' section). Patient satisfaction and adverse events will be also reported. All the clinical evaluations are performed by a medical staff not involved in the injective procedure, in order to keep the study double blinded. At the end of the study, the nature of the injected substance is revealed to the patients.