Endoscopically Assisted Treatment of Condylar Base and Neck Fractures: A Single Institution Analysis of Outcomes and Complications

Abstract

Background

Conservative treatment, including observation and closed treatment, as well as open reduction and internal fixation are existing options for treating condylar process fractures. Extraoral approaches are widely preferred for open reduction and internal fixation. Transoral access for condylar base and neck fractures is not yet commonly used as it is technically demanding and requires special equipment.

Purpose

In this study, the transoral endoscopically assisted approach is described, and its outcomes and complications were investigated. Imaging data and clinical records of 187 patients with condylar process fractures, treated via endoscopically assisted transoral approach between 2007 and 2017 were analyzed. Parameters included diagnosis and fracture classification, treatment, osteosynthesis configuration and postoperative complications.

Results

Early complications, including infection, transient postoperative malocclusion, pain and limited mouth opening, occurred in 35 patients (18.7%). Late onset complications, such as screw loosening were documented in only 4 patients (2.1%). Revision surgery following postoperative 3D imaging was required in only 3 cases (1.6%). Fragment length ranged from 15.5 to 38.3 mm. In 57.7% of patients with condylar fragment length < 20 mm, a single osteosynthesis plate was used, with no elevated complication rate. Two osteosynthesis plates with 4 screws each was used as standard in longer fragments.

Conclusion

Endoscopically assisted transoral treatment of condylar process fractures is a reliable, yet technical demanding technique. It allows for reduction and fixation of fractures with a condylar fragment length of > 15 mm with low postoperative complication and revision rates.

Introduction

Mandibular fractures account for 65–75% of all facial bone fractures [1]. In 25–45% of those fractures, the condylar process is involved [1, 2]. Many different classifications [3–7] have been introduced but often lack clear treatment recommendations. Besides the latest AOCMF classification, all previous ones were based on 2D imaging, including the commonly used Spiessl and Schroll classification [4]. Nowadays, 3D imaging such as cone beam-computed tomography (CBCT) or computed tomography (CT) is considered mandatory to adequately assess condylar process fractures and allow for surgical decision making. This has been taken into consideration in the most recent classification by Cornelius and Neff [7], which follows the latest requirements and developments in surgical techniques [2]. According to this classification, fractures of the condylar process can be subdivided into fractures of the head, neck and base. However, indications or recommendations for treatment are not included.

Basically, surgical and non-surgical options are available. Commonly accepted indications for surgery include luxation, dislocation, deviation of more than 30°, comminution and loss of vertical height [8, 9]. Absolute indications for surgical treatment of condylar neck fractures are severe dislocation, bilateral fractures, heavily distorted occlusion and impaired function [10–12]. Non-displaced fractures and edentulous patients, in general, are only relative indications.

The terminology for non-surgical treatment can be misleading and must be chosen carefully. Usually, non-surgical options are summarized as conservative treatment and include either observation or closed treatment. Observation includes soft diet and analgesia, while closed treatment requires a closed reduction with any kind of immobilization using mandibular-maxillary fixation (MMF). Conservative options are suggested to have minor or even no early complications. However, severe late complications might arise, including deviation in mandibular movements, dysmorphic joints, resorption, arthrosis, restricted mouth opening, ankylosis, internal derangements and chronic pain [13]. In our opinion, the term closed treatment (closed reduction) for dislocated condylar process fractures might be misleading, since it is impossible to reduce a dislocated condylar head or neck fracture against muscular contraction with loss of vertical height by using just MMF. Contrary to closed treatment, open reduction and rigid internal fixation (ORIF) allows for early function, with or without shorter periods of elastic MMF. Early function without MMF increases patient´s acceptance, improves quality of life, preserves joint function, and reduces the risk of postoperative temporomandibular joint (TMJ) disorders [14, 15]. Some meta-analyses recommend open treatment in general [16, 17].

A variety of different ORIF techniques have been suggested so far. Internal fixation with a single miniplate was suggested to lead to an increased rate of screw and plate failure [18]. Two miniplates seem to be the best solution for rigid fixation [19, 20], since it was proved to be the only method to withstand normal forces of loading [21]. Alternative options include a single load-bearing reconstruction plate [22]. In this study, a modification of the two-plate-fixation method was used. Instead of conventional miniplates, a 2.0 mm dynamic compression plate (DCP, Compact System, DepuySynthes, Raynham MA, USA) was used to align the posterior aspect of the ascending ramus and distal fragment with application of compression. The second plate, a conventional miniplate, was inserted at a 30° angle to the compression plate, if possible. Further developments in fixation methods for condylar base and neck fractures include preformed osteosynthesis plates (Modus Midface 2.0, Medartis, Switzerland), rhomboid plates (Rhombus 3D, KLS Martin Group, Tuttlingen, Germany) and catching condyle plates [23], which can also be inserted transorally.

For fractures of the condylar neck and base, extraoral incisions are more commonly used than the transoral approaches. They include retro- and submandibular, angular or the rhytidectomy approach. Some of these approaches require dissections through the parotid gland and facial nerve branches [24–27] with a 14.4% risk of temporary facial nerve injury and 1.4% risk of permanent injury. Thus, the risk of visible scars and temporary or permanent damage to neural and glandular structures is present, which might lead to reluctance for surgery. On the other side, those fractures cannot be accessed adequately using conventional transoral approaches, with or without transbuccal options. The endoscopically assisted transoral approach provides an additional treatment option for those fractures that cannot be accessed via pre- or retroauricular approaches and where retro- or submandibular approaches would be required.

However, special instruments and endoscopic equipment are required to perform the presented approach. Extended training in endoscopic techniques and handling of the angulated instruments is also essential [10, 28, 29]. The transoral approach to the condylar process and the option for endoscopic assistance have been previously described [28, 30]. Its advantage is known to be a lower risk for facial nerve trauma.

In this study, fracture topography, surgical and clinical parameters, indications, limitations, complications, and the outcomes of patients treated with the endoscopically assisted transoral approach have been analyzed.

Materials and Methods

Patients, Clinical and Radiological Data Collection

This study was approved by the local ethical review committee (study nr: 8163_BO_K_2018). The department’s internal database was scanned for patients with ICD 10 codes S02.61 (fracture of condylar process) and S02.64 (fracture of mandibular ramus). Subsequently 187 patients with condylar process fractures who had undergone endoscopically assisted open reduction and internal fixation between 2007 and 2017 were included. Fractures of the condylar head were excluded. The patients’ data were analyzed, including patients’ history, demographics, fracture etiology and fracture-related symptoms, imaging, surgical details, method of fixation, intra and postoperative complications, clinical follow-up, and TMJ-related parameters like pain, mouth opening (MIO) and occlusion using the Eichner Index [31]. Three-dimensional imaging datasets (CT, CBCT) were analyzed using Visage^® (Visage 7.1, Visage Imaging GmbH, Berlin, Germany), iPlan^® CMF 3.0 (Brainlab, Munich, Germany) and Voxim 6.0 (IVS Solutions, Chemnitz, Germany). Fracture topography was analyzed two and three dimensionally, and different established fracture classifications were applied. The length of the condylar fragment was measured from the highest physiological point of the condylar head to the fracture line in an oblique sagittal or coronal view (Figs. 1a/b, 3a). Data collection was performed using Microsoft Excel 2010 (Microsoft, Redmond, USA) and statistical analysis was carried out in SPSS (IBM SPSS Statistics 25, IBM, Armonk, USA). Mean and standard deviations were calculated. Uni- and multivariate regression analyses were carried out to identify predictive parameters for postoperative complications.

Fig. 1.

Thirty-eight-year-old male patient with an unilateral condylar neck fracture on the left side. a Preoperative CT-scan in oblique sagittal orientation, bone windowing, dislocated, contracted fracture of the condylar neck; measurement of fragment length: 21.6 mm. b Preoperative CT-scan in coronal orientation, bone windowing; measurement of fragment length: 29.4 mm. c Intraoperative CBCT-scan in oblique sagittal orientation, after reduction and internal fixation with two 2.0-mm osteosynthesis plates. d Intraoperative CBCT-scan in coronal orientation

Fig. 3.

Nineteen-year-old male patient with an unilateral, dislocated condylar neck fracture on the left side. a Preoperative CT-scan in coronal orientation, bone windowing; measurement of fragment length: 15.9 mm. b Intraoperative CBCT-scan in coronal orientation, bone windowing; reduced and fixed fracture. c Endoscopic photograph, distal osteosynthesis plate fixed (DCP); condylar fragment is further reduced via the second, more anterior plate, which is already fixed to the fragment. In this case, a locking plate was used

Description of the Surgical Technique

For the endoscopically assisted transoral open reduction and fixation, the retromolar region was infiltrated with a local anesthetic and vasoconstrictor agent (Articaine/Adrenalin 1:100,000) to provide hemostasis. A retromolar incision was made in the vestibule and extended onto the anterior margin of the ascending ramus. Orthognathic retractors and instruments are recommended during dissection. The condylar fragment was carefully dissected without complete denudation, either medially of the ascending ramus by simultaneous distraction of the mandible, or laterally out of the vestibular soft tissues. Electrocauterization was used carefully without harming facial nerve, which can be in direct vicinity. Contrary to conventional ORIF techniques, the first osteosynthesis plate was fixed to the condylar fragment first and was used to reduce the dislocated fragment. Prior to reduction, the first osteosynthesis plate was fixed at the posterior aspect of the condylar fragment. Without reduction, the first hole was drilled in the condylar fragment 2–3 mm from the fracture line using the angulated drill. The position of the hole was checked endoscopically (Fig. 2a). Then, the first osteosynthesis plate mounted onto the angulated screw driver, together with the first screw next to the fracture line, was carefully inserted and fixed. Before the first screw was fully tightened, the alignment of the plate along the posterior aspect of the condylar fragment was checked and corrected, if required. The second hole then was drilled (Fig. 2b) and the screw was inserted into the distal fragment to fix the plate to it. Again, the position of plate and screws was verified using the endoscope. Depending on the type of dislocation, the mandible was now distracted to allow the reduction of the fragment over the proximal mandibular segment. Using a claw-shaped hook instrument, the fragment was pulled on top of the proximal mandibular segment using the first osteosynthesis plate. The alignment was again checked endoscopically (Fig. 2c). If correct reduction was achieved, the distal fragment was fixed to the proximal mandibular segment with the third screw under compression of the fracture line. The reduction of the distal fragment with the claw-shaped instrument and the dynamic compression plate (DCP, Compact System, DepuySynthes, Raynham MA, U.S.) provided the required compression of the fracture. Occlusion and mandibular movements were checked prior to definitive fixation. Finally, the second osteosynthesis plate was fixed at a 30° angle to the first, using the same technique (Fig. 2d). The second plate can either be a conventional miniplate or another DCP. Locking screws and plates can also be used (Fig. 3c). Usually, 2.0 mm plates with 6 mm screws are sufficient. Quality control of reduction and fixation was performed either intra- or postoperatively using 3D imaging. Intraoperatively, a CBCT (Ziehm Vario RF 3D, Ziehm Imaging, Nürnberg, Germany) was used (Figs. 1c/d, 3b). The patients were scanned in MMF in order to assess condylar positions in habitual occlusion.

Fig. 2.

Thirty-eight-year-old male patient with an unilateral condylar neck fracture on the left side. a Intraoperative endoscopic photograph after transoral approach, dissection of periosteum and initial reposition of the fractured condylar neck. b, c Endoscopic photograph, drilling and fixation of the first osteosynthesis plate (DCP). d Final situation of the reduced fracture and osteosynthesis with two 2.0-mm plates with 4 screws each. The anterior plate is fixed with one single screw in the condylar fragment

Postoperative Regime

MMF was established for 3–14 days, depending upon the fracture type, topography, classification and surgeon’s preference. The patients received only liquids for the first 3 days and continued with soft diet for 14 days. Starting from postoperative day 3, early functional mobilization was started with intermittent MMF. Antibiotics were administered as perioperative single injections and were continued only in comminuted, combined and complex fractures.

Results

One hundred and eighty-seven patients with 208 fractures of the condylar process were treated using the endoscopically assisted transoral approach, between 2007 and 2017.

Fracture Topography and Classification

All fractures were condylar base or neck fractures according to the AO classification. Twenty-one fractures (11.2%) were bilateral, of which 73.4% had additional mandibular fractures like symphyseal or body fractures; 44.6% of the unilateral fractures were associated with other mandibular fractures. According to the AO classification the inferior part of the condylar fragment was medially or laterally dislocated in 76.7% of fractures. Complete luxation of the condylar head out of the glenoid fossa was diagnosed in 21.6% of fractures. Comminuted fractures with more than two condylar fragments occurred in 14.4% of fractures. Fragment length ranged from 15.5 to 38.3 mm, with a mean of 26.25 ± 5.98 mm.

Demographics and Etiology

Nearly 3 of 4 patients were male (140; 74.9%), 47 were female (25.1%). Their ages ranged from 4 to 83 years with a mean of 35.2 ± 15.9 years (Table 1). The most common cause of trauma was interpersonal violence, followed by fall and traffic accidents (Table 2).

Table 1.

Patients characteristics

Gender
Male	n = 140	74.9%
Female	n = 47	25.1%
	Mean	SD
Patient age (years)	35.2	± 15.9
Surgery duration (minutes)	149.8	± 76.4
Hospital stay (days)	7.6	± 3.0

Table 2.

Cause of trauma

Cause of trauma	n	%
Violence/crime	76	40.6
Bicycle accident	27	14.5
Traffic accident	16	8.6
Syncopated fall	7	3.7
Sporting accident	11	5.9
Fall	46	24.6
Other	4	2.1
Total	187	100

Surgical Details and Type of Fixation

The mean operation time was 149.8 ± 76.39 min (Table 1). The setting-up time for the endoscope was 6.9 ± 2.3 min. If the fragment length was ≥ 15 mm and ≤ 20 mm, a single plate with 4 screws (2 in the condylar fragment) was placed at the posterior edge of the ramus in 57.7% of fractures (Fig. 4). If the fragment length was ≥ 20 mm in 84.1% of fractures a second plate—anterior to the first plate—with at least 1 screw in the condylar fragment (Fig. 2d) could be inserted. Finally, in 74.7%, the second plate could be fixed with 2 screws in condylar fragment (Fig. 3c). 86.7% of all treated patients received MMF for a maximum of 14 days.

Fig. 4.

Bar graph, showing number of fractures and osteosynthesis type used, in dependence of condylar fragment length

Complications

In total, in 35 cases (18.7% of cases, 16.8% of fractures), complications were assessed. In bilateral fractures, no bilateral complications could be identified in this study. Three patients (1.6%) underwent revision surgery after postoperative 3D imaging (CBCT/CT), because intraoperative imaging was not available at that time. In 3 other cases (1.6%), an extraoral approach became necessary during surgery, as repositioning via the initial intraoral approach failed. After revision surgery, no more complications were documented. However, when extraoral approaches were performed additionally, 2 of those 3 cases developed an abscess, which was treated with drainage and antibiotics. Apart from that, early postoperative complications after uneventful surgery (Fig. 5) occurred in 31 patients (16.6%), those included temporary malocclusion, reduced mouth opening, wound dehiscence and abscesses. From those, 27 occurred within the first 2 weeks after surgery. Abscesses were treated with drainage and antibiotics, temporary malocclusion and reduced mouth opening resolved without therapy. Only 4 of the 31 patients (2.1%) had late onset complications including screw loosening or hardware failure. In these cases, as well late revision surgery was performed to remove the loosened screws and plates. Re-osteosynthesis was not necessary since the fracture had already healed properly.

Fig. 5.

Number of cases with different complications after transoral endoscopically assisted reduction and internal fixation of condylar neck fractures, total n = 35. 31 of these occurred within 2 weeks after surgery. Only 4 patients suffered from late onset complications, all of those were screw loosening

In summary, the most common complications of the 31 patients were temporary limited mouth opening (n = 8) and abscess (n = 10). Permanent facial nerve damage or damage to the parotid gland or the intraoral part of the parotid duct was not observed at all.

A significant correlation between the condylar fragment length and incidence of abscess was found (p = 0.038), with higher values in longer fragments. Screw loosening and malocclusion were more common in cases with shorter fragments. In a logistic regression analysis with the variable “abscess” a significant influence of the Eichner Index (category B and C) was found (p = 0.013). No influence of the type of osteosynthesis on the occurrence of complications was found.

Discussion

The treatment of condylar process fractures is still controversial and differs significantly between, and even within, countries [32]. Closed treatment was widely favored for the majority of condylar process fractures in the past [13, 33, 34]. However, in recent years, a paradigm shift toward surgical open treatment can be seen. Studies show fewer late onset complications such as malocclusion or TMJ-pain and an improved early function with a shorter period of IMF [10, 16, 29, 35, 36]. The different extraoral approaches to the condylar process have a risk of either transient or permanent damage to the facial nerve, visible scars or affections of the parotid gland [37]. Since there is no risk of damage to those structures, and because of a tolerable outcome, conservative treatment is still widely preferred over surgical options. However, the disadvantage of extraoral approaches to the condylar process can be avoided for selected cases by using a transoral route with endoscopic assistance [10, 28, 29, 38]. This approach to condylar process fractures is reliable, reproducible, and has, apart from minor temporary complications, low late onset complications (2.1%) and low revision rate (1.6%). We could further show no elevated complication rate by using only one osteosynthesis plate in especially short condylar fragments, contrary to former reports [18]. Open treatment aims to reduce anatomic structures in order to restore affected function [10, 39, 40]. In contrast, closed treatment can result in facial asymmetry due to shortening of mandibular height on the fractured side [41]. Therefore, a fractured condylar fragment with a dislocation of 10°–45° or a loss of vertical height in the ascending ramus of 2 mm or more, should be treated with open reduction and internal fixation. The patients with severe occlusal disturbance immediately after trauma seem to benefit significantly from open treatment [10]. These data support the presented therapeutic algorithm for condylar base and neck fractures.

In addition, a new diagnostic tool could be validated in the present study. By measuring the length of the condylar fragment in an oblique sagittal view, the indication for the transoral endoscopically assisted approach can be made. If the fragment length is ≥ 20 mm, the patients are treated transorally. If the fragment is between 20 and 15 mm, decision making for surgical approach has to be done in respect of cases individual configuration, but as we could show in this study, transoral approach is even feasible for condylar fragments down to 15 mm. For even shorter fragments, reduction and internal fixation is done via an extraoral approach.

In this monocentric, retrospective analysis, only cases treated via the transoral endoscopically assisted approach were included in order to assess diagnosis, indication, outcome, morbidity, complications and clinical follow-up. The initial complication rate of 18.7% in this study was similar to those published before [1, 42]. However, the definition of complication varies among studies. It is crucial to differentiate between transient early complications and irreversible long-term ones. Kokemueller et al. [10] reported mild clinical dysfunctions in 37% and severe clinical dysfunction in 7% of patients with fractured condylar neck, treated with endoscopic assistance. Complications found in our study were mostly early surgical complications such as wound infection, abscesses and mild postoperative pain. The significantly higher rate of abscesses in cases with longer fragments in the present study could have been induced by the increased proximity of the osteosynthetic material to the oral cavity. Moreover, deficient occlusal support (Eichner class B and C) could be a predictor for postoperative complications, whereas as the age of patients was not. Interestingly, not only patients with complete loss of occlusal support (Eichner C) but also patients with partial loss (Eichner B) seem to have a higher risk for abscess and/or screw loosening. An influence of less stabilization provided by IMF in these patients cannot be ruled out.

Conclusion

Due to technical progress, the transoral endoscopically assisted approach for treating fractures of the condylar process has become more popular in recent years. Surgical decision making can be simplified by measuring the condylar fragment length in 3D imaging. As we could show, transoral approach can be chosen for condylar fragments of at least 15 mm length. This approach retrospectively showed only minor complications and low revision rates. It provides a reliable alternative for treating condylar neck and base fractures by avoiding visible scars, reversible and irreversible facial nerve palsy and parotid gland affections. In general, open treatment of fractures of the condylar process, particularly of the condylar base and neck, is effective and safe. Contrary to closed treatment, it allows for early function and does not show significant long-term TMJ dysfunctions.

Author’s Contribution

All authors contributed to the study conception and design. Material preparation, data collection and analysis were performed by [M-TN], [LB] and [RZ]. The first draft of the manuscript was written by [M-TN] and [RZ] and all authors commented on previous versions of the manuscript. All authors read and approved the final manuscript.

Funding

No funding received.

Availability of Data and Material

Not applicable.

Compliance with Ethical Standards

Code Availability

Not applicable.

Conflict of interest

The authors declare that they have no conflict of interest.

Consent to Participate

Not applicable.

Consent for Publication

Not applicable.

Ethical Approval

This study was approved by the local ethical review committee (study nr: 8163_BO_K_2018).