Long-term clinical efficacy and imaging evaluation of submandibular joint injection of hyaluronic acid for irreversible anterior displacement of the articular disc

Anterior disc displacement without reduction (ADDwoR) represents a common and debilitating subtype of temporomandibular disorder, manifesting as restricted mouth opening and joint pain that profoundly affects patients’ quality of life. This study aims to evaluate the long-term clinical efficacy and associated structural changes of patients with ADDwoR treated with intra-articular injections of sodium hyaluronate into the superior compartment of the temporomandibular joint (TMJ). In total, 209 patients diagnosed with ADDwoR who presented to the clinic between January 2016 and June 2023 were included. Of these, 27 patients underwent complete magnetic resonance imaging evaluations both before and after treatment (follow-up duration: 1–6 years. The therapeutic protocol consisted of joint lavage followed by sodium hyaluronate injection administered every 2 weeks; three consecutive sessions comprised one full treatment course. Magnetic resonance imaging was used to measure the length of the joint disc and its displacement distance. Clinical efficacy was assessed using the Craniomandibular Index (CMI), Jaw Functional Limitation Scale, and psychological assessment tools, including the Generalized Anxiety Disorder Questionnaire-7, Patient Health Questionnaire-9 (PHQ-9), and Patient Health Questionnaire-15. Post-treatment results revealed no statistically significant differences in joint disc length (8.95 ± 1.26 mm vs. 8.46 ± 1.10 mm) or disc displacement distance (3.79 ± 1.36 mm vs. 4.36 ± 1.96 mm) (P > 0.05). However, both the Dysfunction Index and Craniomandibular Index demonstrated significant reductions following treatment (P < 0.001). Functional improvement was further supported by a marked decrease in the Jaw Functional Limitation Scale score, from 81.59 ± 40.55 to 30.59 ± 25.57 (P < 0.001). Additionally, psychological assessments indicated significant improvements in anxiety (Generalized Anxiety Disorder Questionnaire-7) and depression (Patient Health Questionnaire-9) scores (P < 0.05). While hyaluronic acid injections do not restore the anatomical configuration of the articular disc, existing evidence and findings from this study suggest they effectively reduce inflammation and enhance joint lubrication. These therapeutic effects contribute to functional recovery and alleviate the psychological distress associated with chronic TMJ dysfunction. To further substantiate the long-term protective benefits of this intervention on TMJ structure and function, future research should incorporate larger sample sizes and adopt a prospective, controlled study design.