Over the past two decades of TMJ surgeries, we have consistently observed a vein passing over the TMJ capsule. The capsular vein described in this study has not been clearly defined in the literature; however, it is presumed to be a branch of the middle temporal vein. In all patients, we observed that the capsular vein runs vertically across the middle of the articular fossa in the same fascial plane as the frontal branch of the facial nerve, making it a useful intraoperative guide to avoid nerve injury. In our series, identifying and ligating this vessel during the TMJ approach was associated with no significant intraoperative bleeding and no permanent facial nerve weakness, and it reduced the need for extensive dissection to locate the facial nerve. These findings suggest that using the capsular vein as a landmark allows the TMJ to be approached more efficiently and safely.

Maxillofacial surgeons frequently operate on a wide variety of TMJ pathologies. Although many skin incisions have been suggested, the fundamental deep approach is similar because the key structures lie within the same anatomical layers [9]. The preauricular approach remains one of the preferred options [4, 10]. The hockey-stick modification can improve the anterior and lateral exposure and results in safe and temporary impairment of function [6]. Despite the evolution of numerous approaches to the TMJ, the frontal (temporal) branch of the facial nerve remains at risk for injury during dissection. Opinions differ regarding the exact course and safe region of this nerve branch, and considerable variation exists in anatomical descriptions [9]. During TMJ surgery, it is essential to identify and avoid the facial nerve branches to prevent injury; however, facial nerve injury following to the maxillofacial region ranges from 0 to 48% [1]. The highly variable course of the temporal branch makes it particularly susceptible to injury during TMJ surgery [11]. The risk of facial nerve injury is especially elevated in patients with TMJ ankylosis [6, 7]. In severe inflammatory conditions like ankylosis, the normal fascial planes can be distorted, making it difficult to maintain the correct dissection plane. This significantly increases the risk of nerve injury, even though surgeons are aware that the temporal branch typically lies 8–35 mm anterior to the external auditory meatus, deep to the temporoparietal fascia at the level of the zygomatic arch [12]. Using our described technique, after the capsular vein was ligated, the temporal branch of the facial nerve could be consistently identified with a nerve stimulator on the anterior or anteromedial side of the ligated vein in all patients. We emphasize that this procedure obviates the need for a separate dissection to find the facial nerve, thereby reducing the risk of direct nerve exposure or injury. Nevertheless, surgeons should still take care to avoid excessive retraction or stretching of the tissues, as this can cause neurapraxia of the nerve.

Arthroplasty—which was the most commonly performed procedure (66.1% of cases) in this study—is among the oldest techniques for TMJ surgery, having originated in the nineteenth century. The early form of this procedure involved a simple resection to separate the mandibular ramus from the skull base. Because that approach often resulted in a high rate of re-ankylosis, later modifications increased the gap between the resected bone segments (to at least 10 mm), leading to the development of the gap arthroplasty (GA) technique [13]. To create such a large gap, the surgical resection typically includes not only the condyle but also a portion of the glenoid fossa. Because the glenoid fossa is a deep concavity in the temporal bone, preserving or re-establishing its shape may be advantageous for TMJ function. Wang et al. reported in an in vivo study that the presence and proximity of the developing mandibular condyle are essential for normal development of the glenoid fossa [14]. In cases with normal anatomy, we found that the ligated capsular vein was typically positioned at the midpoint of the glenoid fossa, corresponding roughly to the center of the condylar head. Therefore, the capsular vein can serve as a useful intraoperative reference point during arthroplasty. Importantly, the capsular vein courses vertically across the lateral capsule at the most superior point of the glenoid fossa. This consistent anatomical location allows it to serve as a valuable reference even in cases where normal anatomy is disrupted, such as bony ankylosis, severe inflammation, loss of the condylar head, or displaced condylar fractures. Furthermore, as long as the condyle and capsule are present (e.g., in conditions other than complete bony ankylosis), this vein could be used as a landmark for the capsular incision to access the superior joint space—for example, to help locate and remove pathologic nodules in synovial chondromatosis.

This study has several limitations. First, it was a retrospective analysis without a control group, which inherently introduces potential selection bias and limits the strength of comparative conclusions. All patients in our series underwent the same surgical technique, so we could not directly compare outcomes between the capsular vein-guided approach and other conventional approaches that involve facial nerve dissection or different landmarks. Second, the capsular vein has not been clearly defined in anatomical literature, and we did not perform cadaveric dissection or dedicated imaging studies to validate its anatomy. Thus, its exact origin and course, as well as its consistent relationship to the facial nerve, remain to be confirmed. Looking ahead, further studies are needed to validate and expand upon our findings. Anatomical verification of the “capsular vein” through cadaveric dissection would help confirm its consistent presence, vascular origin, and precise anatomical relationship to the facial nerve and surrounding structures.

Despite these limitations, the capsular vein was consistently present and identifiable in all patients in our cohort. By using the capsular vein as an anatomic landmark to guide the surgical approach, we were able to minimize the risk of nerve damage and intraoperative bleeding, since this was the only vessel that required ligation. This technique also improved visualization of the TMJ capsule and articular eminence, allowing the surgeon to plan the capsular incision or ostectomy for procedures such as ankylosis release, total joint replacement, or other interventions based on the patient’s needs. Ultimately, our clinical results provide a foundation for future research on this structure. Multicenter studies with larger patient samples, as well as dedicated cadaveric dissection and high-resolution imaging to validate the vein’s anatomical characteristics, can build on our work to determine the broader applicability and surgical relevance of the capsular vein as a landmark for safe TMJ surgery.