Occipitocervical dissociative injuries: common in blunt trauma fatalities and better detected with objective computed tomography-based measurements.
ABSTRACT Occipitocervical injuries (OCIs) are generally not common in blunt trauma victims, but autopsy studies of blunt trauma fatalities consistently report a high prevalence of these injuries. New computed tomography (CT)-based quantitative criteria have recently been developed for use in assessing the occipitocervical spine. The efficacy of these new criteria for detecting OCI would be supported if the high prevalence of OCI in blunt trauma fatalities can also be detected using these objective CT-based criteria.
To test the hypothesis that the prevalence of OCI in blunt trauma fatalities, determined using objective CT-based measurements and reliable reference data, will be similar to the prevalence reported in prior autopsy studies.
Retrospective assessment of the CT examinations of blunt trauma fatalities at a Level 1 trauma center.
Seventy-four consecutive patients who died within 21 days of blunt trauma and had a CT examination of the cervical spine.
Quantitative measurements from CT examinations of the occiput-C1 and C1-C2 levels.
Measurements were made on a Picture Archiving and Communication System (PACS) from the CT images that were originally used for diagnosis and also using imaging software that allowed for precisely reoriented slices that correct for variations in the alignment of the upper cervical spine. The prevalence of abnormal measurements found by each method and the interobserver reliability of the measurements were assessed.
At least one abnormal measurement was found in 50% of cases based on measurements made on the PACS, and in 34% of cases using measurements from carefully reoriented images. At least three abnormal measurements were found in 22% and 14% of patients, respectively. Only one of the patients had been diagnosed as having an OCI before death. Interobserver reliability measurements of more than 80% were found for most measurements.
Using precise CT-based measurements and reliable reference data for diagnosis of occipitocervical dissociative injuries, the prevalence of injuries in severely injured blunt trauma patients was close to the levels reported in prior autopsy studies (approximately 30%). This supports that with careful measurements, both soft- and hard-tissue OCI can be detected by CT. This study is limited by the fact that a gold standard was not available to confirm the injuries.
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ABSTRACT: An anatomical study using six fresh, human cadaveric cervical spine specimens was performed. After the dissection of all soft tissue, flexion-extension radiographs were obtained to verify initial stability. A sagittal plane bone cut was then made, centered on the odontoid and sparing the alar ligaments, the tectorial membrane, and the atlantooccipital (AO) ligaments. Repeat flexion-extension radiographs and photographs were taken to document maintenance of stability of these hemisections. The occipital-atlantoaxial ligaments were then individually and sequentially incised, maintaining all other structures each time. After the sectioning of each ligament, flexion-extension radiographs and photographs were obtained to identify subsequent motion patterns. Both gross anatomical and roentgenographic examinations demonstrated the important stabilizing role of the tectorial membrane in flexion. Additionally, contact between the posterior arch of Cl and the occiput limited hyperextension as a secondary restraint once the tectorial membrane was sectioned. Furthermore, the AO ligaments proved to play an insignificant role in the preservation of AO stability through a flexion-extension arc of motion. Under normal circumstances, the AO articulation is not excessively stressed. However, acute AO injury, as well as the insidious failure of these ligaments, has been documented in several cases involving various pathologies. This study demonstrates a mechanism of instability and highlights the essential role of the tectorial membrane in maintaining upper cervical spine stability. (C) Lippincott-Raven Publishers.Journal of Spinal Disorders & Techniques 01/1993; 6(1). · 1.77 Impact Factor
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ABSTRACT: High-speed computed tomography (CT) exams have replaced traditional radiographs for assessment of cervical spine injuries in many emergency departments. Recent evidence demonstrates that even subtle displacements can indicate significant upper cervical spine injuries. Many different anatomical measurements have been described in the upper cervical spine to date, most of them based on X-ray. The range of anatomical relationships that exist in an uninjured population must be known to reliably detect abnormal relations. The measurements with the lowest normal variation are likely to be most useful in detecting injuries. The purpose of this study was to describe the normal quantitative anatomical relationships as well as the threshold measurements most likely to detect injury in the upper cervical spine. Retrospective anatomical case review. Seventy-six thin-sliced cervical CT scans randomly selected from a trauma population, all negative for injury in the cervical spine. Forty-two different anatomical measurements were made of the upper cervical spine. These included traditional historical measurements and other detailed dimensions to characterize occipitocervical (OC) and atlantoaxial (AA) joint relationships. After review of all the anatomical measurements performed in the upper cervical spine, direct measurements of the joint space had the least variation. The mean OC joint space was 0.6mm, with an upper 95% confidence interval (CI) of 1mm at the most anterior or posterior aspects of the joints. This was true for both sagittal and coronal measurements. The mean AA joint space was 0.6mm, with an upper 95% CI of 1.2mm at the lateral aspect of the joint on the coronal image only. The midsagittal structures demonstrated significantly higher standard deviation and variability. These results revealed consistently narrow joint spaces and left-right symmetry in the upper cervical spine joints that do not vary according to demographics. There was distinctly greater consistency in the coronal plane, which enabled more precise diagnostic measurement and side-to-side comparison of measurements. This precision will enable more accurate identification of abnormal scans, which should prompt consideration for additional workup. Thus, better understanding of these relationships may enable earlier detection of subtle craniocervical dissociative injuries based on CT scan data. This is important, because the only evidence of a severe injury on CT can be subtle misalignment.The spine journal: official journal of the North American Spine Society 03/2010; 10(3):219-29. · 2.90 Impact Factor
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ABSTRACT: In the treatment of spine fractures and fracture-dislocations, stability of the spine is one of the major objectives. In the craniocervical joint, the alar and transverse ligaments provide much of the stability of the healthy spine. Because the anatomy appears well described, the contribution of each of these structures so far has received little attention. The alar ligament restrains rotation of the upper cervical spine, whereas the transverse ligament restricts flexion as well as anterior displacement of the atlas. A lesion in one or both structures can produce damage to the neural structures and/or cause pain. To investigate the possible role of each of these ligaments, a mechanical and histologic study of the upper cervical spine was made. The bone-ligament-bone complex of the alar and transverse ligaments was subjected to uniaxial mechanical testing in seven specimens. The alar ligaments had an in vitro strength of 200 N, and the transverse ligaments had an in vitro strength of 350 N. Histologic analysis revealed a mainly collagenous nature of these ligaments. Clinical evidence (broken odontoid processes) suggests that the transverse ligament is strong enough to withstand physiologic loads. The alar ligament, on the other hand, due to its lower strength and its axial direction of loading, might be prone to injury and therefore require stabilization of the appropriate vertebra more often than normally is assumed.Journal of Orthopaedic Research 02/1988; 6(3):452-61. · 2.88 Impact Factor