Effect of Preoperative Intramuscular Injection of Botulinum Toxin A on Pain and Mouth Opening After Surgical Intervention in Temporomandibular Joint Ankylosis Cases: A Controlled Clinical Trial.

[PURPOSE] The aim of the present study was to determine the effect of intramuscular injection of botulinum toxin A (BTX-A) into the masticatory muscles on the physiotherapy pain and mouth opening outcomes after surgical intervention of temporomandibular joint (TMJ) ankylosis and to verify the effects using electromyographic studies.

[PATIENTS AND METHODS] The study included 20 patients with TMJ ankylosis. The patients were further subdivided into control and interventional groups. The interventional group was given intramuscular injections of BTX-A in the masticator muscles before surgery. Only saline injections were given to the control group. All 20 patients were evaluated for pain and ease of active physiotherapy at the 1-week and 1-, 3-, and 6-month follow-up visits using a questionnaire. Intergroup comparisons were performed for both groups. Electromyographic (EMG) studies were also performed in the intervention group for each patient. EMG recordings were performed of the individual masticator muscle in each patient before injection and at 1 and 3 months after injection.

[RESULTS] The intervention group showed better results with respect to pain during the mouth opening exercises and improvements in mouth opening. All the interventional group patients showed a transient decrease in the microvolt value on the EMG studies of their masticator muscles on injection of BTX-A.

[CONCLUSIONS] BTX-A injection can be a straightforward and useful adjunct to surgical treatment of TMJ ankylosis for the reduction of pain during postoperative physiotherapy.