An anatomical study comparing standard fluoroscopy and virtual fluoroscopy for the placement of C1–2 transarticular screws

Morphometric Analysis of the Lumbar Vertebrae Concerning the Optimal Screw Selection for Transpedicular Stabilization

Transpedicular stabilization is a frequently used spinal surgery for fractures, degenerative changes, or neoplastic processes. Improper screw fixation may cause substantial vascular or neurological complications. This study seeks to define detailed morphometric measurements of the pedicle (height, width, and surface area) in the aspects of screw length and girth selection and the trajectory of its implantation, i.e., sagittal and transverse angle of placement. The study was based on CT examinations of 100 Caucasian patients (51 women and 49 men) aged 27-75 with no anatomical, degenerative, or post-traumatic spine changes. The results were stratified by gender and body side, and they were counter compared with the available literature database. Pedicle height decreased from L1 to L4, ranging from 15.9 to 13.3 mm. Pedicle width increased from L1 to L5, extending from 6.1 to 13.2 mm. Pedicle surface area increased from L1 to L5, ranging from 63 to 140 mm². Distance from the point of entry into the pedicle to the anterior surface of the vertebral body, defining the maximum length of a transpedicular screw, varied from 54.0 to 50.2 mm. Variations concerning body sides were inappreciable. A transverse angle of screw trajectory extended from 20° to 32°, shifting caudally from L1 to L5, with statistical differences in the L3-L5 segments. A sagittal angle varied from 10° to 12°, without such definite relations. We conclude that the L1 and L2 segments display the most distinct morphometric similarities, while the greatest differences, in both genders, are noted for L3, L4, and L5. The findings enable the recommendation of the following screw diameters: 4 mm for L1-L2, 5 mm for L3, 6 mm for L4-L5, and the length of 50 mm. We believe the study has extended clinical knowledge on lumbar spine morphometry, essential in the training physicians engaged in transpedicular stabilization.

Operating room radiation exposure in cone beam computed tomography-based, image-guided spinal surgery: clinical article

OBJECT

Surgeon and operating room (OR) staff radiation exposure during spinal surgery is a concern, especially with the increasing use of multiplanar fluoroscopy in minimally invasive spinal surgery procedures. Cone beam computed tomography (cbCT)-based, 3D image guidance does not involve the use of active fluoroscopy during instrumentation placement and therefore decreases radiation exposure for the surgeon and OR staff during spinal fusion procedures. However, the radiation scatter of a cbCT device can be similar to that of a standard 64-slice CT scanner and thus could expose the surgeon and OR staff to radiation during image acquisition. The purpose of the present study was to measure radiation exposure at several unshielded locations in the OR when using cbCT in conjunction with 3D image-guided spinal surgery in 25 spinal surgery cases.

METHODS

Five unshielded badge dosimeters were placed at set locations in the OR during 25 spinal surgery cases in which cbCT-based, 3D image guidance was used. The cbCT device (O-ARM) was used in conjunction with the Stealth S7 image-guided platform. The radiology department analyzed the badge dosimeters after completion of the last case.

RESULTS

Fifty high-definition O-ARM spins were performed in 25 patients for spinal registration and to check instrumentation placement. Image-guided placement of 124 screws from C-2 to the ileum was accomplished without complication. Badge dosimetry analysis revealed minimal radiation exposure for the badges 6 feet from the gantry in the area of the anesthesiology equipment, as well as for the badges located 10-13 feet from the gantry on each side of the room (mean 0.7-3.6 mrem/spin). The greatest radiation exposure occurred on the badge attached to the OR table within the gantry (mean 176.9 mrem/spin), as well as on the control panel adjacent to the gantry (mean 128.0 mrem/spin).

CONCLUSIONS

Radiation scatter from the O-ARM was minimal at various distances outside of and not adjacent to the gantry. Although the average radiation exposure at these locations was low, an earlier study, undertaken in a similar fashion, revealed no radiation exposure when the surgeon stood behind a lead shield. This simple precaution can eliminate the small amount of radiation exposure to OR staff in cases in which the O-ARM is used.

Clinical and methodological precision of spinal navigation assisted by 3D intraoperative O-arm radiographic imaging

OBJECT

In recent years, the importance of intraoperative navigation in neurosurgery has been increasing. Multiple studies have proven the advantages and safety of computer-assisted spinal neurosurgery. The use of intraoperative 3D radiographic imaging to acquire image information for navigational purposes has several advantages and should increase the accuracy and safety of screw guidance with navigation. The aim of this study was to evaluate the clinical and methodological precision of navigated spine surgery in combination with the O-arm multidimensional imaging system.

METHODS

Thoracic, lumbar, and sacral pedicle screws that were placed with the help of the combination of the O-arm and StealthStation TREON plus navigation systems were analyzed. To evaluate clinical precision, 278 polyaxial pedicle screws in 139 vertebrae were reviewed for medial or caudal perforations on coronal projection. For the evaluation of the methodological accuracy, virtual and intraoperative images were compared, and the angulation of the pedicle screw to the midsagittal line was measured.

RESULTS

Pedicle perforations were recorded in 3.2% of pedicle screws. None of the perforated pedicle screws damaged a nerve root. The difference in angulation between the actual and virtual pedicle screws was 2.8° ± 1.9°.

CONCLUSIONS

The use of the StealthStation TREON plus navigation system in combination with the O-arm system showed the highest accuracy for spinal navigation compared with other studies that used traditional image acquisition and registration for navigation.

Radiation exposure during pedicle screw placement in adolescent idiopathic scoliosis: is fluoroscopy safe?

STUDY DESIGN

With institutional review board approval, prospective data were collected during fluoroscopically guided pedicle screw placement.

OBJECTIVE

To estimate a surgeon's radiation exposure with all screw constructs during surgery to repair idiopathic scoliosis.

SUMMARY OF BACKGROUND DATA

To our knowledge, there is no established consensus regarding the safety of radiation exposure during fluoroscopically guided procedures.

METHODS

A surgeon was outfitted intraoperatively with a thermoluminescent dosimeter to estimate radiation exposure to his whole body and thyroid gland.

RESULTS

The index surgeon is projected to receive 13.49 mSv of whole body ionizing radiation and 4.31 mSv of thyroid gland irradiation annually. The National Council on Radiation Protection's current recommendations set lifetime dose equivalent limits for classified workers (radiologists) at 10 mSv per year of life and at 3 mSv for nonclassified workers (spinal surgeons). At the levels estimated, a surgeon beginning his/her career at age 30 years would exceed the lifetime limit for nonclassified workers in less than 10 years. The National Council on Radiation Protection limits the single-year maximum safe dosage to the thyroid to 500 mSv; the yearly exposure estimated here is significantly less.

CONCLUSIONS

The spinal surgeon's intraoperative radiation exposure may be unacceptable. Spinal surgeons should be considered classified workers and monitored accordingly. Methods to lower radiation dosage seem strongly indicated.

Anterior retropharyngeal fixation C1-2 for stabilization of atlantoaxial instabilities: study of feasibility, technical description and preliminary results

Posterior transarticular screw fixation C1-2 with the Magerl technique is a challenging procedure for stabilization of atlantoaxial instabilities. Although its high primary stability favoured it to sublaminar wire-based techniques, the close merging of the vertebral artery (VA) and its violation during screw passage inside the axis emphasizes its potential risk. Also, posterior approach to the upper cervical spine produces extensive, as well as traumatic soft-tissue stripping. In comparison, anterior transarticular screw fixation C1-2 is an atraumatic technique, but has been neglected in the literature, even though promising results are published and lectured to date. In 2004, anterior screw fixation C1-2 was introduced in our department for the treatment of atlantoaxial instabilities. As it showed convincing results, its general anatomic feasibility was worked up. The distance between mid-sagittal line of C2 and medial border of the VA groove resembles the most important anatomic landmark in anterior transarticular screw fixation C1-2. Therefore, CT based measurements on 42 healthy specimens without pathology of the cervical spine were performed. Our data are compiled in an extended collection of anatomic landmarks relevant for anterior transarticular screw fixation C1-2. Based on anatomic findings, the technique and its feasibility in daily clinical work is depicted and discussed on our preliminary results in seven patients.