Clinical application of a CT-designed guide plate for targeted injection into the lateral pterygoid muscle

To investigate the effectiveness of an extraoral guide plate system targeting the superior and inferior heads of the lateral pterygoid muscle in improving the accuracy of injection therapy for anterior disc displacement (ADD) of the temporomandibular joint (TMJ) with lateral pterygoid myalgia, and to provide a reference for precise clinical treatment.

With approval from the institutional medical ethics committee and informed consent from patients, spiral CT scans were performed on seven patients with ADD accompanied or not accompanied by lateral pterygoid myalgia to acquire craniofacial data. Mimics 21.0 software was used to reconstruct three-dimensional craniofacial structures, identify attachment points of the superior and inferior heads of the lateral pterygoid muscle, and design dual injection paths along with a retention system. Personalized templates were fabricated using digital light procession-based 3D printing. Under the guide plate, a single targeted injection of 20 U of botulinum toxin type A (BTX-A) was administered into both the superior and/or inferior heads of the lateral pterygoid muscle. Immediate postoperative CT scans were conducted to compare actual needle placement with preoperative plans. Pain was assessed using the visual analogue scale (VAS) at 3 days and 1, 2, and 4 weeks postoperatively. Joint clicking was recorded at 2 and 4 weeks, and complications were monitored throughout the duration of the study.

A total of 15 sites in 7 patients were injected into the upper / lower head of the lateral pterygoid muscle under the guidance of the guide plate. Under the guide plate, all of the injections achieved an angular deviation within 2.5° (superior head: 2.49° ± 0.17°, inferior head: 2.31° ± 0.16°) and a needle tip positional deviation within 2 mm [superior head: (1.96 ± 0.25) mm, inferior head: (1.65 ± 0.21) mm]. The significant pain improvement rate (defined as ≥3-point reduction in VAS score) increased from 60% (9/15) at day 3 to 85% (13/15) at 2 weeks post-operation, stabilizing at 86.7% (13/15) at 4 weeks post-operation. Joint clicking improvement rates reached 72% (11/15) at 2 weeks post-operation and 75% (11/15) at 4 weeks post-operation. Regarding safety, only one case of injection site swelling and one case of transient paresthesia were observed; both resolved spontaneously within a short period of time. No neurovascular injury events occurred.

CT-guided guide plate achieves precise targeting design to minimize injection errors in the lateral pterygoid muscle. This technology is effective and safe, and it can provide an anatomically specific and operationally versatile targeted therapy for temporomandibular disorders.