Dry needling of the lateral pterygoid muscle: anatomical and CT-scan assessment on cadaveric heads.

Louis sibille [UCL] Benoît Dive Millon, Domitille [UCL] Daniel Bosch Pitance, Laurent [UCL]

Background and Aims: At present, there is a lack of information regarding dry needling of the lateral pterygoid muscle in the treatment of myofascial pain. The aim of the study was to determine the feasibility and safety of an original dry needling technique of the lateral pterygoid muscle on fresh cadaveric heads. Methods: A dry needling approach of the lateral pterygoid muscle was conducted by an expert on six fresh cadaveric heads bilaterally. Twelve needles were inserted under the zygomatic arch, behind the posterior margin of the masseter muscle and anterior to TMJ, with a 25 degree angle in the cranial direction and a 30 degree angle in the anterior direction. Each head was analyzed using CT-scan imaging. The topographical location of the tip of the needle was recorded. An ideal puncture point was then determined on the radiological images, located in the superior head of the muscle. The distance between the tip of the needle and the ideal puncture point was measured in the frontal, coronal and sagittal plans. One of the cadaveric heads was finally used for anatomical study by dissection. Results: Despite a standardized procedure of needle insertion, the variability of locations of the tip of the needle was significant. Eight needles were located in the infratemporal fossa, two were on the posterolateral wall of the maxillary sinus, one was in the pterygomaxillary fossa, and one was in the posterolateral orbital wall. None of the inserted needles were located in the lateral pterygoid muscle. The mean distance between the tip of the needle and the ideal puncture point was 11,2 mm anteriorly, 8,3 mm cranially, and 15,6 mm laterally. During the dissection, several vascular and nervous structures were identified in proximity to the inserted needles, although none of those structures seemed to have been pierced. Conclusions: The lateral pterygoid dry needling technique evaluated in this study was not validated for several reasons. The inserted needles were not located in the lateral pterygoid muscle, for the chosen angle of insertion was too cranial and too anterior. In addition, the risk of iatrogenic lesions is substantial. Further studies are necessary in order to determine an adequate placement technique which can be used on patients. Clinical studies without previous radiological validation of the technique seem premature.