Reliability and Accuracy of Palpable Anterior Neck Landmarks for the Identification of Cervical Spinal Levels

Study DesignA descriptive experimental study.PurposeThe purpose of this study was to describe the reliability and accuracy of palpable anterior neck landmarks (angle of the mandible, hyoid bone, thyroid cartilage, and cricoid cartilage) for the identification of cervical spinal levels in a slight neck-extended position as in anterior approach cervical spinal surgery.Overview of LiteratureStandard, palpable anatomical landmarks for the identification of cervical spinal levels were described by Hoppenfeld using the midline palpable anterior structures (angle of the mandible [C2 body], hyoid bone [C3 body], thyroid cartilage [C4–C5 disc], cricoid cartilage [C6 body], and carotid tubercle [C6 body]) to determine the approximate level for skin incisions. However, in clinical practice, patients are positioned with a slight neck extension to achieve cervical lordosis. This positioning (neck extension) may result in changes in the locations of anatomical landmarks compared with those reported in previous studies.MethodsThis experimental study was conducted on 96 volunteers. Each volunteer was palpated for locating four anatomical landmarks three times by three different orthopedic surgeons. We collected data from the level of the vertebral body or the vertebral disc matching the surface anatomical landmarks from the vertical reference line.ResultsAccuracy of the angle of the mandible located at the C2 vertebral body was 95.5%, the hyoid bone located at the C2/3 intervertebral disc was 51.7%, the thyroid cartilage located at the C4 vertebral body was 42%, and the cricoid cartilage located at the C5/6 intervertebral disc was 43.4%.ConclusionsWith the neck in a slightly extended position to achieve cervical lordosis, the angle of the mandible, the hyoid bone, the thyroid cartilage, and the cricoid cartilage were most often located at the C2 body, the C2/3 disc, the C4 body, and the C5/6 disc, respectively. The angle of the mandible and the hyoid bone are highly reliable surface anatomical landmarks for the identification of cervical spinal levels than the thyroid cartilage and the cricoid cartilage

Biomechanical Study of Posterior Pelvic Fixations in Vertically Unstable Sacral Fractures: An Alternative to Triangular Osteosynthesis

Study Design Biomechanical study. Purpose To investigate the relative stiffness of a new posterior pelvic fixation for unstable vertical fractures of the sacrum. Overview of Literature The reported operative fixation techniques for vertical sacral fractures include iliosacral screw, sacral bar fixations, transiliac plating, and local plate osteosynthesis. Clinical as well as biomechanical studies have demonstrated that these conventional techniques are insufficient to stabilize the vertically unstable sacral fractures. Methods To simulate a vertically unstable fractured sacrum, 12 synthetic pelvic models were prepared. In each model, a 5-mm gap was created through the left transforaminal zone (Denis zone II). The pubic symphysis was completely separated and then stabilized using a 3.5-mm reconstruction plate. Four each of the unstable pelvic models were then fixed with two iliosacral screws, a tension band plate, or a transiliac fixation plus one iliosacral screw. The left hemipelvis of these specimens was docked to a rigid base plate and loaded on an S1 endplate by using the Zwick Roell z010 material testing machine. Then, the vertical displacement and coronal tilt of the right hemipelves and the applied force were measured. Results The transiliac fixation plus one iliosacral screw constructions could withstand a force at 5 mm of vertical displacement greater than the two iliosacral screw constructions (p=0.012) and the tension band plate constructions (p=0.003). The tension band plate constructions could withstand a force at 5° of coronal tilt less than the two iliosacral screw constructions (p=0.027) and the transiliac fixation plus one iliosacral screw constructions (p=0.049). Conclusions This study proposes the use of transiliac fixation in addition to an iliosacral screw to stabilize vertically unstable sacral fractures. Our biomechanical data demonstrated the superiority of adding transiliac fixation to withstand vertical displacement forces

COX-2 expression mediated by calcium-TonEBP signaling axis under hyperosmotic conditions serves osmoprotective function in nucleus pulposus cells.

The nucleus pulposus (NP) of intervertebral discs experiences dynamic changes in tissue osmolarity because of diurnal loading of the spine. TonEBP/NFAT5 is a transcription factor that is critical in osmoregulation as well as survival of NP cells in the hyperosmotic milieu. The goal of this study was to investigate whether cyclooxygenase-2 (COX-2) expression is osmoresponsive and dependent on TonEBP, and whether it serves an osmoprotective role. NP cells up-regulated COX-2 expression in hyperosmotic media. The induction of COX-2 depended on elevation of intracellular calcium levels and p38 MAPK pathway, but independent of calcineurin signaling as well as MEK/ERK and JNK pathways. Under hyperosmotic conditions, both COX-2 mRNA stability and its proximal promoter activity were increased. The proximal COX-2 promoter (-1840/+123 bp) contained predicted binding sites for TonEBP, AP-1, NF-κB, and C/EBP-β. While COX-2 promoter activity was positively regulated by both AP-1 and NF-κB, AP-1 had no effect and NF-κB negatively regulated COX-2 protein levels under hyperosmotic conditions. On the other hand, TonEBP was necessary for both COX-2 promoter activity and protein up-regulation in response to hyperosmotic stimuli