After TMJ double-puncture arthrocenthesis under local anesthesia, hyaluronic acid (Suplasyn®, 20 mg/ml) will be injected in the joint with the first portal.

32ml of venous blood per joint will be collected and added to four 8ml-collection tubes containing sodium citrate. Then, blood will be centrifugated at 800rpm for 8 minutes at room temperature. 3 layers are perceptible: (1)layer with platelet-rich plasma and growth factors; (2)layer with white blood cells; (3)layer corresponding to red blood cells. Then, the total plasma volume will be calculated, and the plasma corresponding to the first fraction (low platelet fraction) aspirated. The second fraction of the first layer corresponding to PRP, above the white blood cell layer, will be removed and transferred to new tubes.

10 minutes before the mixing with HA, a calcium chloride-rich activator (Endoret ®, BTI Biotechnology Institute, Vitoria-Gasteiz, Álava, Spain) will be added to the PRP. The mixture of PRP with HA was then carried out at a ratio of 1cc of low molecular weight HA (Suplasyn®, 20 mg/ml) +1cc of PRP and introduced in the joint with the first portal.

The first puncture involved carefully palpating the lateral rim of the glenoid fossa. A 5-cc syringe was prepared with a mixture of 3 cc of Ringer lactate and 1.8 cc of lidocaine with epinephrine. A 21-G needle connected to the syringe was gently inserted into the TMJ skin area. Once the needle tip made contact with the posterior slope of the eminence of the upper joint compartment, it was oriented vertically to access the upper compartment, allowing the surgeon to perform a validation step. For the second puncture, the joint was maintained at maximum distention with continuous inflow through the first portal, while the surgeon felt insufflation/distention in the anterior joint area. The second portal was established using a 21-G needle with successful fluid outflow. After completing an effective circuit, joint washing was carried out using intra-articular hydraulic pressure with at least 150 ml of Ringer lactate solution.

The level of TMJ arthralgia was registered through pain during palpation of the lateral pole or around the lateral pole or pain on maximum unassisted or assisted opening, right or left lateral movements, or protrusive movements, following the DC/TMD guidelines.12, 13 Patient scored for each side using a 10-point VAS, from 0-no pain and 10-severe pain.

MMO was measured using a certified ruler between the incisor's teeth.