Changes of condylar position after orthognathic surgery may in long term lead to skeletal relapse, malocclusion, condylar resorption, and TMJ dysfunction. Reyneke [2, 10] described various types of condylar displacement—condylar sag—and divided it into two main categories—peripheral and central. Reyneke also suggested that assuring the proper relationship of the condyle to the glenoid fossa is critical and is probably the most demanding step in the BSSO procedure.

Condyle positioning appliances were introduced to address this issue. However, in the authors’ department, these appliances have not yet been utilized. Also, usage of these devices remains controversial, as the benefit of using them is uncertain [11, 12]. Some studies also suggest computer-assisted condylar positioning techniques. In a systemic review, Chow reports considerable accuracy in both the non-computer-assisted and computer-assisted condylar positioning techniques [13].

The amount of segment movement, local anatomy, presence of eventual bony interferences, and experience of the performing surgeon also influence condylar position. Harris reported the amount of distal segment movement, extent of mandibular rotation, and local anatomy indication the shape of the mandible may be important [8].

Type of osteosynthesis can also be an important factor influencing condylar position after orthognathic surgery. Some authors still recommend bicortical screws, even despite the reported condylar displacement risk and higher percentages of skeletal relapse [14]. Some authors prefer the usage of one miniplate with monocortical screws, while others apply two miniplates [3, 15, 16]. Reyneke believes the use of bicortical screws for BSSO osteosynthesis relates to a higher risk of peripheral condylar sag—when the segments are forcefully fixated, tension is applied to the condyle, which can result in condylar displacement medially, laterally, or inferiorly [10]. In the authors’ earlier published studies, no significant changes in condylar position and function were found after fixing BSSO with bicortical screws [17, 18].

Verhelst stated it is believed that BSSO induces biomechanical stresses at the TMJ [19]. This biomechanical stress can lead to a process called “physiological joint remodeling.” When joint remodeling surpasses its physiological limits, pathological remodeling can occur regardless of whether the patient had preexisting TMJ dysfunction. The question of why one overloaded joint develops TMD and another develops condylar resorption remains an enigma. In the same article, the authors stated that in the postoperative phase, three types of biomechanical stresses are possible at the TMJ—prolonged alteration of the condyle position, tension in the muscles attached to the mandible, and postoperative orthodontic forces incurred with the use of elastics.

Mild condylar remodeling is normal after orthognathic surgery. In a study published by Claus utilizing CBCT condylar superimposition, medial and lateral surfaces presented fewer bone changes. Overall, the bone changes in their study were smaller than 1 mm in 85.7% [20]. In a volumetric CBCT study of the TMJ published by Park, condylar volume and height showed a significant decrease in 6 months after bimaxillary orthognathic surgery, but a significant increase between 6 months to 6 years after surgery [21]. Another study published by Xi [22] also found a mean of 6.1% in postoperative condyle volume. The question of follow-up timing plays an important role in the whole study model. As mentioned in previous studies [19, 21, 22], follow-ups are recommended immediately after surgery, at 6 months after surgery, and also after longer periods of time [21] in order to properly characterize the extent of condylar remodeling and changes of position after orthognathic surgery.

All of the cases in this study were performed using conventional planning. Digital planning has been utilized in the authors’ department since April 2023, and none of the patients operated have yet managed it to the follow-up CT after 6–12 months after surgery. Three-dimensional planning offers more possibilities and methods in assessing TMJ position pre- and postoperatively and also more detailed planning of the osteotomies, movements, and also segment torque and flaring in order to avoid abnormal movements [23, 24].

In this study, the results showed significant changes in pre- and postoperative values in AB angle, which represents condylar rotation in the transversal axis. This change was even more apparent in mandibular setback group, where the values showed a significant decrease, indicating medial condylar rotation. Higher FDR values in the advancement group indicate a more anterior postoperative condylar position in comparison to the setback group.

There is still controversy as to whether orthognathic surgery influences TMJ function. Farella reports an unpredictable and variable occurrence of TMD after orthognathic surgery [4]. In Abrahamsson’s study, TMD symptoms after orthognathic surgery improved [5]. Moroi reports an improved occlusal contact area, bite force, and occlusal balance after orthognathic surgery [25]. In a study published by Togashi, it was reported that 16.5% of the patients with no preoperative TMJ disorder symptoms started to experience TMJ disorders after orthognathic surgery [6]. Kretschmer reported a 6.4% incidence of TMJ pain, 4.8% crepitus, and clicking 19.1% developing after orthognathic surgery in preoperatively asymptomatic patients [7].

In a systematic review published by Veldhuis, also confirmed by other authors [5, 17,18,19, 25], it was concluded that orthognathic surgery does not seem to have any harmful impact on the TMJ [17,18,19, 25, 26].

The authors of this study can conclude that orthognathic surgery does have a moderate effect on postoperative position of the condyles, especially regarding condylar rotation in the transversal axis.