Abstract
A significant proportion of facial asymmetry cases are caused by abnormal growth of the mandibular condyles. Surgical management is generally based on a condylectomy performed through a pre-auricular transcutaneous access. However, this approach entails potential neurovascular, salivary, and aesthetic complications. In this study, a proof-of-concept evaluation was performed of a novel minimally invasive technique for condylectomy performed through an intraoral approach. Based on precise three-dimensional virtual planning to define intraoperative references, this technique provides an excellent access for total or partial condylectomy through a limited intraoral incision. Piezoelectric surgery with customized attachments enables the safe, accurate execution of the condylectomy. In addition, experience gained in seven consecutive cases suggests that the need for coronoidectomy can be obviated, surgical time is reduced to an average of 16.9 min, and postoperative morbidity is minimal. This alternative intraoral approach could become the treatment of choice for most condylar hyperplastic conditions.
Generically, condylar hyperplasia (CH) refers to any condition capable of enlarging the mandibular condyle, thereby affecting the size and morphology of the mandible, altering the occlusion, and indirectly affecting the maxilla. A symmetric or most often asymmetric dentofacial deformity can develop as a result. Treatment entails temporomandibular joint (TMJ) surgery to address the underlying pathological condition in the condyle and subsequent or concomitant orthognathic surgery to restore facial harmony and re-establish a functional occlusion.
The conventional approach to the mandibular condyle consists of an extraoral access through a pre-auricular incision. This extraoral approach provides excellent visualization of the condyle, condylar neck, and glenoid fossa. Moreover, additional anatomical exposure can be gained by temporal extension, zygomatic arch sectioning, or combination with a submandibular approach. Due to the proximity to vital anatomical structures, this approach entails a risk of neurovascular complications or salivary fistulae. It is technically complex, time-consuming, and requires a certain degree of surgical expertise. In addition, the use of an external transcutaneous incision can result in unaesthetic scarring.
As an alternative to this extraoral approach, an intraoral access to the condyle is possible. This intraoral approach minimizes the risk of facial nerve injury and salivary fistulae, and visible facial scars are avoided completely. Hence, a rapid postoperative recovery and high patient satisfaction are to be expected. Despite these advantages, the popularity of this approach, as reported in the scientific literature, is comparatively low. This is probably due to the lack of a comprehensive description of the surgical technique and the absence of precise treatment planning criteria.
A minimally invasive surgical protocol for intraoral condylectomy is described herein. This novel technique is based on precise three-dimensional (3D) treatment planning and piezoelectric surgical resection of the condylar process using customized attachments. A comprehensive analysis of the authors’ preliminary experience with seven consecutive cases is presented as a proof-of-concept demonstration of the feasibility, efficiency, and safety of this technique.
Patients and methods
All patients with facial asymmetry due to abnormal condylar growth, who underwent condylectomy via an intraoral approach at a specialized centre for the treatment of dentofacial deformities, were evaluated prospectively. The Declaration of Helsinki guidelines on medical protocol and ethics were followed at all stages of treatment. The performance of this study did not alter the ethically approved protocol for the diagnosis and treatment of facial asymmetry at the study centre and hence was exempt from the requirement for further ethical approval.
Diagnostic workup and treatment planning
After a detailed interview and thorough clinical assessment, the imaging protocol for facial asymmetry at the study institution was followed. This protocol includes: (1) technetium 99m ( 99m Tc) scintigraphy, in order to investigate active condylar growth, and (2) cone beam computed tomography (CBCT) (i-CAT version 17–19; Imaging Sciences International, Hatfield, PA, USA) in maximum mouth opening position, in order to evaluate the condylar morphology and the translation in maximum inter-incisal opening. The study centre’s standardized scanning protocol for dentofacial deformity patients was used. This protocol comprises vertical (sitting upright) scanning in the ‘extended field’ mode (field of view (FOV) 17 cm diameter and 22 cm height, scan time 7 s, voxel size 0.4 mm) at 120 kV and 5 mA. Patients were instructed to sit upright and position themselves in natural head position (NHP).
Primary CBCT images were stored as 576 DICOM (Digital Imaging and Communications in Medicine) data files. These were segmented manually and processed using third-party software (SimPlant Pro OMS; Materialise Dental, Leuven, Belgium). A 3D skull model reconstruction was obtained ( Fig. 1 ). The prospective level and orientation of the ostectomy were planned according to the underlying diagnosis and the adjacent anatomical structures, respectively ( Fig. 2 ). A high condylectomy was planned for an anatomically normal condyle, whereas a low condylectomy (at the junction of the condylar head and neck and preserving the condylar neck) was planned for benign tumours. Scanning in maximum mouth opening enabled the surgeon to determine whether the amount of condylar translation in maximum opening would be clearly sufficient to enable the planned resection through an intraoral approach. In addition, the anatomical relationship to the coronoid process was evaluated in terms of potential interference with the surgical access.
Surgical technique
Under general anaesthesia and nasotracheal intubation, maximum mouth opening was forced with a Molt mouth gag fitted with silicone tubing to avoid dental injuries.
A 2-cm vertical incision was made along the anterior border of the ascending mandibular ramus. This incision is similar to that used for a sagittal split osteotomy. Sub-periosteal dissection proceeded cranially towards the coronoid process and then deeply towards the sigmoid notch. The temporalis tendon was dissected from the anterior, lateral, and medial border of the ramus up to the level of the sigmoid notch ( Fig. 3 ). The superior temporalis attachment on the coronoid process above the level of the mandibular notch was preserved completely. If required, a coronoidectomy was performed at this stage using a piezoelectric microsaw (Implant Center 2; Satelec-Acteon Group, Tuttlingen, Germany).
