Peer-Review ReportTraumatic (Type II) Odontoid Fracture with Transverse Atlantal Ligament Injury: A Controversial Event
Introduction
The craniovertebral junction (CVJ) area is a very special, complex, and intriguing region of the spine where the strict cooperation between articular joints, ligaments, and membrane tension bands permits a wide range of movements compared with all other spinal levels (10). Ligamentous elements have a central role in any junctional traumatic injuries, not only to guarantee vertebral stability but also to influence the chance of bone fusion (8).
A detailed knowledge of all ligaments and membranes and their relationship with vertebral bone fractures is imperative from a clinical point of view, with the aim of guaranteeing the correct traumatic injury management and the appropriate operative strategies. The cruciform ligament is the most important stabilizer element of the CVJ region. It is composed of a transverse and a vertical part that form a cross behind the dens (26). The transverse part, called TAL, is considered the thickest and the strongest ligament of the entire spine and is the predominant stabilizer of the atlas (C1) and the axis (C2), constraining C1 around the dens (12, 24). The TAL and axis dens are connected by the presence of fibrocartilaginous layer on the anterior side of the TAL, forming a median C1-2 synovial joint between the facies articularis dentis and the fovea dentis (Figure 1) (27).
Dickman et al. (9) divides traumatic injury of the TAL into two types: type I, the disruption of the ligament substance, and type II, ligament avulsion at the osseous insertion site (atlantal tubercle of C1 lateral mass). The most common fracture of the second cervical vertebra is the odontoid fracture (Figure 2) (15), which surgical management was described for the first time by Mixter and Osgood in 1910 (22). Odontoid fractures are classified on the basis of the classification introduced by Anderson and D'Alonzo (3) in 1974 and later subjected to few modifications (14, 16).
Anderson and D'Alonzo (3) identified three fractures subtypes, on the basis of the anatomical location of the fracture line, that require completely different management strategies. Type I fractures involves the tip of the dens, type II fractures occurs across the neck of the dens, and type III fractures extends from the base of the dens into the axis body.
Despite the strict anatomical relationship between TAL and axis dens and the deep knowledge of their traumatic injury characteristics, the connection between these combinations of injuries is controversial and poorly defined. Only two contrasting studies concerning this issue are available in the literature (15, 28). Greene et al. (15) identified , in 1994, three patients in a series of 30 (10%) with concomitant injuries, subsequently Sayama et al. (28) reported, in 2006, a large series of 158 patients with type II and III odontoid fractures without spinal instability due to TAL injury in every cases.
We present our experience with 27 cases with traumatic odontoid type II fractures (Figure 2) who underwent magnetic resonance imaging (MRI) of the TAL in the acute phase. Our aim is to analyze the role of TAL injury and choose the appropriate neuroradiological tools in patients with type II odontoid fracture.
Section snippets
Methods
Between 2000 and 2009, 42 consecutive patients with traumatic type II odontoid fractures were managed at neurosurgical unit of the Niguarda Cà Granda Hospital in Milan. All patients presented to our emergency department immediately after traumatic injury, underwent computed tomography (CT) scan with 3D reconstruction (coronal and sagittal planes) demonstrating isolated odontoid type II fracture. MRI study was feasible, in the acute phase (<72 hours), for 27 patients (64%) with clinically stable
Results
CVJ CT scans demonstrated type II odontoid traumatic fractures in all patients (Figures 3A and 4A). A total of 27 patients underwent MRI, in the acute setting, with the aim of revealing any traumatic signs of the TAL damage. A total of 26 patients (96.3%) showed a uniform dark ligament without any sign of traumatic injuries (Figure 3B), and one patient (3.7%) had direct evidence of TAL disruption (Figure 4B). In the section to follow we report a detailed description of this single case.
Traumatic Odontoid Fracture
Traumatic odontoid fractures are classified on the basis of Anderson and D'Alonzo's classification (3), developed in 1974, and currently used with few modifications (14, 16). Odontoid fractures are common injuries and frequently an outcome of motor vehicle accidents and falls from a standing position, especially in young adults and in the elderly population, respectively (3, 17). The degree of neurological involvement varies; however, the majority of patients have a normal neurological
Conclusion
Traumatic type II odontoid fracture with TAL avulsion is a controversy event in literature but clearly documented here. It is widely known that CVJ ligaments and membranes have a central role in maintaining spinal stability after traumatic injury; however, it is very difficult to identify and interpret correctly a ligamentous traumatic damage. MRI actually has become the study of choice to directly evaluate normal and pathological anatomy of the TAL and to obtain a reliable assessment of the
Acknowledgments
A special thanks to Elena Sala for her review of the manuscript.
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2017, Neurosurgery Clinics of North AmericaCitation Excerpt :The role of MRI in odontoid fractures remains an area of debate. Although ligamentous injury, specifically of the transverse atlantal ligament, may be missed on plain radiographs and CT, the incidence of this seems to be low—between 0% and 10%.17–19 Despite the rarity of this injury, the integrity of the transverse ligament is an important consideration in the treatment algorithm.
Analysis of radiological measurement parameters that can predict the type of treatment to be applied in odontoid fractures: Clinical research
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Conflict of interest statement: The authors declare that the article content was composed in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.