Platelet-rich Plasma vs Viscosupplementation in the Treatment of Knee Articular Degenerative Pathology (PRP)

The investigators hypothesized that intra-articular injections of Platelet-rich Plasma (PRP) to treat knee degenerative articular cartilage pathology could determine pain relief and recovery of knee function with overall clinical outcome comparable or even better than viscosupplementation, which is a common injective approach applied in this kind of pathology. To this purpose the investigators designed a double blind randomized controlled trial comparing PRP vs viscosupplementation.

A power analysis has been performed for the primary endpoint of IKDC subjective score improvement at the 12-month follow-up for PRP. From a pilot study, a standard deviation of 15.2 points was found. With an alpha error of 0.05, a beta error of 0.2 and a minimal clinically significant difference of 6.7 points corresponding at 1/3 of the documented mean improvement, the minimum sample size was 83 for each group. Considering a possible drop out of 15%, 96 patients per group are required for total 192 patients, selected according to well-defined inclusion criteria (see 'Eligibility criteria' section). Patients are then assigned to two different treatment groups, according to a randomization list. The first group of treatment consists of three weekly intra-articular injections of autologous PRP obtained with the following procedure: a 150-ml autologous venous blood sample undergoes 2 centrifugations (the first at 1480 rpm for 6 minutes to separate erythrocytes, and a second at 3400 rpm for 15 minutes to concentrate platelets) to produced 20 ml of PRP. This unit of PRP is then divided into 4 small units of 5 ml each. One unit is sent to the laboratory for analysis of platelet concentration and for a quality test, 3 units are stored at -30° C.

The second treatment group consists of patients receiving three weekly injections of hyaluronic acid (Hyalubrix 30 mg/2ml, Fidia Farmaceutici Spa, Italy;Molecular Weight: 1500 kDa).

To guarantee the blinding of the patients, all of them undergo blood harvesting to obtain autologous PRP which will be used only in half of them, according to the aforementioned randomization list. One week after the PRP production, the injective treatment starts, with 3 weekly injections of PRP or HA. At the moment of the injection the syringe is properly covered to prevent the patient from discovering the substance he was receiving. After the injection, patients are sent home with instructions to limit the use of the leg for at least 24 h and to use cold therapy/ice on the affected area to relieve pain. During this period, the use of non-steroidal medication is forbidden.

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.