Hyaluronic acid injections for pain relief and functional improvement in patients with temporomandibular disorders: an umbrella review of systematic reviews

Background: Temporomandibular disorders (TMD) are the main cause of chronic facial pain, and intra-articular (IA) injections of hyaluronic acid (HA) are commonly performed. Objectives: This umbrella review of systematic reviews aimed at analysing the effectiveness of HA injections on pain and functional outcomes in patients affected by TMD. Methods: PubMed, Cochrane Library and PEDro were systematically searched from inception until 17 January 2023 to identify systematic reviews evaluating the effects on pain and functional outcomes of HA IA injections. PROSPERO registration number: CRD42022382586. Results: Out of 316 papers suitable for title/abstract screening, 18 articles were included in the umbrella review. Thirteen studies included only randomized controlled clinical trials (RCTs). The included systematic reviews reported no statistically significant differences between HA and corticosteroids, whereas platelet derivates seem to have good results in pain relief. The literature did not show severe adverse events, except for mild pain in the site of injection. Concerning the quality assessment of the 18 systematic reviews, 2 (11.11%) had a high quality, 3 (16.67%) a moderate quality, 7 (38.89%) a low quality and 6 (33.33%) a critically low quality. Conclusions: Taken together, findings of this umbrella review showed intriguing effects of IA HA injections in terms of reduction of pain intensity and improvement of functioning in patients affected by TMD. Furthermore, there is no agreement on the effectiveness of a combination of arthrocentesis or arthroscopy with IA HA injections. Although the literature showed these positive results after IA HA injections, the overlapping of primary studies in the systematic reviews included might have affect our results, such as the very low quality of the papers. Thus, further RCTs are needed to confirm the efficacy of IA injections of HA on pain relief in patients with TMD.