Morphological classification of the tubercle of insertion of the transverse atlantal ligament: A computer tomography–based anatomical study of 200 subjects

Background and purpose The atlantal tubercle is the attachment point of the transverse atlantal ligament, the main stabilizer of the atlantoaxial complex. No system of classification of the tubercle exists in the literature. We aimed to develop a morphologically based classification system of the atlantal tubercle to aid clinicians who deal with craniocervical pathology. Materials and methods A retrospective review of computed tomography (CT) scans of the cervical spine was performed. The morphology of the atlantal tubercle was classified into four variants: rounded (classical), pointed, flattened, and hypoplastic. Age, presence, and morphological type were recorded. Results A total of 200 CT scans were identified and reviewed. The tubercle was present bilaterally in all patients. Patients were equally distributed over various age ranges. The following morphological types were recorded: rounded (227/400; 56.8%), pointed (13/400; 3.3%), flattened (126; 31.5%), and hypoplastic (34/400; 8.5%). The same type was seen bilaterally in 68% (135/200) of patients. Morphological types appear equally on the right and left side of the atlas. Conclusions The first morphologically based classification system of the atlantal tubercle utilizing CT is presented. Morphology type, especially hypoplastic type, may confer an increased risk for subsequent need for posterior fusion.

Traumatic Atlantoaxial and Fracture-Related Dislocation

Traumatic atlantoaxial dislocation due to ligamentous and combined osseous injuries rarely occurs in adults. There are only few cases published in the literature. In this level 4 study, a cohort of nine consecutive patients suffering from traumatic atlantoaxial dislocation has been analyzed regarding morphology of injury, trauma mechanism, and outcome since 2007. Three types of those injuries have been found regarding direction of dislocation indicating the underlying ligamentous injuries as well as the accompanying grade of instability. Firstly, there was rotatory dislocation, if the alar ligaments were injured. Secondly, there occurred horizontal dislocation, when transverse atlantal ligament was damaged additionally. Thirdly, excessive ligamentous injury led to distraction of the atlantoaxial complex resulting in dissociation of the atlas against the axis. Additionally fractures of the atlas as well as of the odontoid process (type II or III according to Anderson/D’Alonzo) were diagnosed frequently. Atlantoaxial dislocation injuries, especially distraction injuries, offer a high risk for accompanied neurovascular disorders deserving reduction followed by surgical fixation. Only rotatory injuries leading to ligamentous damage solitarily can safely be successfully treated conservatively. Understanding of the injuries’ morphology is essential, in order to set the correct diagnosis and to implicate the most advantageous treatment regime.

Traumatic injury of the transverse atlantal ligament

Introduction. In some cases C2 may suffer only rotational dislocation around its own axis (dens), causing no increase in the atlantodental interval (ADI), making it difficult to diagnose the instability in static radiographies. Objective. To report a case of atlanto-axial traumatic subluxation, without bony injury or displacement, in which the diagnosis cannot be achieved through conventional radiology and computed tomography, and discuss the types of transverse ligament injuries, its diagnosis, the instability and their treatment. Methods.A 61-year-old man, victim of head (occipital), complaining neck. Static radiographies and CT scan of cervical spine were performed, demonstrating no abnormalities. Flexion and extension cervical radiography revealed an increase of ADI in flexion, indicating instability and damage to the transverse atlantal ligament (TAL). The MRI of the cervical spine demonstrated the discontinuity of the TAL, configuring an injury to the structure of the ligament. The patient underwent to early surgery with C1-C2 fixation using the Goel-Harms’technique. Results. The diagnosis could be revealed only in dynamic radiographs or MRI study. The patient presented complete improvement of symptoms. Conclusions. The use of cervical dynamic radiography and / or magnetic resonance imaging allowed the diagnosis of instability and visualization of the TAL injury, avoiding the lack of diagnosis with its consequences. The MRI allows a direct view of the ligament injury, their classification and the prognostic evaluation of the injury, guiding the therapy, surgical or conservative.