Anatomic parameters of the sacral lamina for osteosynthesis in transverse sacral fractures.

PURPOSE: To analyze the morphometric parameters of the dorsal sacral lamina and pedicles to determine if there is adequate bony architecture to support plate osteosynthesis. METHODS: Two reviewers performed measurements on 98 randomly selected high-resolution CT scans of the pelvis to quantify the bony anatomy of the sacral lamina. Measurements included the depths of the lamina at each sacral level, the trajectory and depth of the sacral pedicles from the sacral lamina, and the width of the sacral canal. A bone mineral density analysis was performed on the sacral lamina using Hounsfield units (HU) and compared to the L1 and S1 vertebral bodies. RESULTS: The sacral lamina were found to form peaks and troughs which we refered to as major and minor sections. On average, the thickness was > 4 mm at all major screw starting points, indicating adequate geometry for screw fixation. The sacral pedicle depths were 27, 18, 16, and 14 mm at S2-S5, respectively. The average angulation from midline of this screw path directed laterally to avoid the sacral canal was 20°, 17°, 8°, and - 8° for the S2-5 pedicles, respectively. Average sacral canal diameter was 11 mm for S2 and 8 mm for S3-5. The sacral lamina had an average bone mineral density of 635 HU, which was significantly different from the density of the L5 (220 HU) and S1 (165 HU) vertebral bodies (p < 0.005). This morphometric data was used to pilot a new plating technique. CONCLUSIONS: The sacral lamina offers a novel target for screw fixation and meets the basic geometric and compositional criteria for screw purchase. To our knowledge, this study represents the first morphometric analysis performed on the sacral lamina and pedicles for plate application.

Artifacts in musculoskeletal ultrasonography.

During the past 2 decades, high-resolution ultrasonography (US) has been increasingly utilized in the diagnosis of musculoskeletal trauma and diseases with results comparable with MR imaging. US has an advantage over other cross-sectional modalities in many circumstances due to its superior spatial resolution and ability to allow dynamic assessment. When performing musculoskeletal US, the examiner has to be knowledgeable in the complex anatomy of the musculoskeletal system and US imaging technique. Additionally, he or she must be familiar with several common imaging artifacts in musculoskeletal US that may be mistaken for pathology, as well as several artifacts that frequently accompany pathologic conditions. These artifacts may occur with both B-mode gray-scale and Doppler imaging. In this article, we discuss common artifacts seen in musculoskeletal US and techniques to avoid or minimize these artifacts during clinical US examinations.

Radiographic Analysis of Cervical and Spinal Alignment in Multilevel ACDF with Lordotic Interbody Device.

BACKGROUND: Restoration and maintenance of cervical lordosis is an important clinical parameter in spine surgery. The purpose of this study was to determine the extent to which a multilevel anterior cervical discectomy and fusion (ACDF: greater than 3 levels) procedure restores cervical lordosis and the affect of increasing lordosis on sagittal vertical axis. METHODS: We performed a retrospective radiographic analysis of 69 patients who underwent multilevel ACDF by 2 surgeons between 2013 and 2014. We measured the global and segmental sagittal alignment of the cervical spine using the cobb method at 4 time intervals (preop, post op 4wks, 10wks and 6 months) as well as the sagittal vertical axis (SVA) using both a C1-S1 and C7-S1 plumb line methods at 2 time intervals (preop and post op 4wks). Radiographs were measured by three reviewers. RESULTS: Interrater reliability was good to excellent for all measurements. Cervical lordosis significantly increased from preop 10.26° to 4 weeks postop 19.44° and was maintained up to 6 months 19.34 (p<0.0005). Segmental cervical lordosis was also significantly increased from preop 8.22° to post op at 4 weeks (20.26°) and was maintained at post op 10weeks 20.30° and post op 6 months 19.56° (p<0.0005). C7-S1 SVA and C1-S1 SVA also significantly increased from 12.04mm preop to 27.49mm post op 4 wks (p<0.0005) and -1.93mm preop to 8.67mm post op (p<0.0005) respectively. A change in C2-C7 lordosis positively correlated with a change in C7-SVA and C1-SVA (r=0.37, P<0.005, and r=0.312, p<0.05 respectively). CONCLUSIONS: Multilevel ACDF significantly increases and maintains both segmental and global cervical lordosis up to 6 months after surgery. Increasing C2-C7 global lordosis is correlated with increasing positive sagittal vertical axis. Level of evidence: IV.