C-arm assessment of cervical pedicle screw - Screw coaxial fluoroscopy and oblique view
ABSTRACT Oblique view and screw coaxial fluoroscopy were used to assess cervical pedicle screw position in human cadaveric spine, results of which were compared with those of direct visual inspection by an anatomist.
To determine whether clinicians can detect misplaced cervical pedicle screws with accurate sensitivity and specificity using conventional C-arm equipment.
In the cervical region, pedicle screws have not been used so popularly as in lumbar or in thoracic regions. The reasons are related to the risk of inserting screw in small pedicle. So far, no method has been studied to assess the position of cervical pedicle screw during the operation.
Ten human cadavers were prepared for this study. Headed and nonheaded pedicle screws were inserted bilaterally from C3-C7. Using C-arm oblique and screw coaxial fluoroscopy, the depth of penetration was recorded in 2-dimension scale (superoinferior and mediolateral direction) by 6 different observers. The vertebrae were all harvested, and the penetration depth was recorded by an anatomist under direct visualization. The accuracy of C-arm measurements was analyzed. The results of nonheaded and headed screws also were compared.
A total of 98 pedicle screw positions were finally enrolled into the study. The oblique view can verify screw position with the sensitivity of 86.1% and specificity of 64.5%. Coaxial fluoroscopy had a sensitivity of 89.8% and a specificity of 56.9% in superoinferior direction. Mediolaterally coaxial fluoroscopy had a sensitivity of 70.0% and a specificity of 51.3%.
C-arm assessment of pedicle position has acceptable accuracy. With C-arm swing motion of the coaxial fluoroscopy, headed screws were also inspected without any difference as nonheaded screws. Measurements for superoinferior direction showed better sensitivity than those for mediolateral direction, which are supposed to be related to be elliptical shape and thin lateral margin of cervical pedicle.
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ABSTRACT: Prospective study evaluating the sterility of 25 C-arm drapes after their use during spine surgery. To use swab samples to evaluate the sterility of draped C-arms at the end of spine surgical cases and assess the integrity of the sterile technique. Intraoperative fluoroscopy is used routinely in the operating room for a variety of spinal applications. Although the C-arm may help the surgeon assess spinal alignment and facilitate the placement of instrumentation, there are concerns that the C-arm may represent a potential source of contamination and increase the risk of developing a postoperative infection. METHODS.: This study included 25 surgical cases requiring a standard fluoroscopic C-arm that were performed by 2 spine surgeons. Sterile culture swabs were used to obtain samples from 5 defined locations on the C-arm drape after its use during the operation. The undraped technician's console was sampled in each case as a positive control and an additional 25 C-arm drapes were swabbed immediately after they were applied to the C-arm unit in order to obtain negative controls. Swab samples were assessed for bacterial growth on 5% sheep blood Columbia agar plates using a semiquantitative technique. Contamination was noted on only 1 of 25 negative control drapes at a single location (4%). One hundred percent and 96% of the positive control swabs that were obtained from the negative controls and postoperative drapes exhibited growth, respectively. Although at least some degree of contamination was observed at all locations of the C-arm drape after surgery, the upper 2 sample sites demonstrated the greatest degree of contamination; the incidences of postoperative contamination were significantly greater for the top (56%, P < 0.000001) and upper front of the receiver (28%, P = 0.010) compared to the negative controls. In contrast, the lower front, receiver plate, and midportion of the C-arm were associated with lower rates of contamination (12%-20%). The upper portions of the C-arm clearly exhibited the greatest rates of contamination during spinal operations. This contamination most likely occurs when the undraped portions of the C-arm are rotated to acquire lateral images. As a result, we no longer consider the top portion of the C-arm drape to be sterile in these situations and we believe that avoiding contact with these areas may decrease the risks of intraoperative contamination and possibly postoperative infection as well.Spine 07/2008; 33(17):1913-7. DOI:10.1097/BRS.0b013e31817bb130 · 2.45 Impact Factor
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ABSTRACT: To describe a free-hand method for pedicle screw placement in the lower cervical spine with no intraoperative imaging monitors, and to evaluate the safety of this technique. A study of the free-hand technique of cervical pedicle screw placement was conducted by postoperative radiological review and follow-up. Thirty-six patients who had had cervical reconstruction with posterior plate utilizing pedicle screw fixation, and been followed for a minimum of 2 years, were studied. The position of the pedicle screw was evaluated by postoperative oblique radiographs and axial computed tomograms. Clinical outcomes were measured by Odem's criteria. A total of 144 screws of diameter 3.5 or 4.0 mm were inserted into the cervical pedicles in 36 patients. Postoperative images showed that 16 (11.1%) of the screws had penetrated the pedicle walls. Among them, 10 (6.9%) screws had penetrated the lateral, 4 (2.8%) the superior and 2 (1.3%) the inferior walls. However, there were no neurological or vascular complications related to the malpositioned screws during a minimum of 2 years follow-up. In addition, Odem's scores were applied postoperatively in all patients except one with complete neurological deficit. Based on 144 screw placements, cervical pedicle screw insertion utilizing a free-hand technique without intraoperative imaging guidance seems to be safe and reliable. However, solid knowledge of the anatomy of the cervical pedicle and adjacent neurovascular bundles, and careful preoperative review of cervical images, are imperative for successful screw placement in the cervical spine.Orthopaedic Surgery 05/2009; 1(2):107-12. DOI:10.1111/j.1757-7861.2009.00023.x
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ABSTRACT: Reconstruction of the highly unstable, anteriorly decompressed cervical spine poses biomechanical challenges to current stabilization strategies, including circumferential instrumented fusion, to prevent failure. To avoid secondary posterior surgery, particularly in the elderly population, while increasing primary construct rigidity of anterior-only reconstructions, the authors introduced the concept of anterior transpedicular screw (ATPS) fixation and plating. We demonstrated its morphological feasibility, its superior biomechanical pull-out characteristics compared with vertebral body screws and the accuracy of inserting ATPS using a manual fluoroscopically assisted technique. Although accuracy was high, showing non-critical breaches in the axial and sagittal plane in 78 and 96%, further research was indicated refining technique and increasing accuracy. In light of first clinical case series, the authors analyzed the impact of using an electronic conductivity device (ECD, PediGuard) on the accuracy of ATPS insertion. As there exist only experiences in thoracolumbar surgery the versatility of the ECD was also assessed for posterior cervical pedicle screw fixation (pCPS). 30 ATPS and 30 pCPS were inserted alternately into the C3-T1 vertebra of five fresh-frozen specimen. Fluoroscopic assistance was only used for the entry point selection, pedicle tract preparation was done using the ECD. Preoperative CT scans were assessed for sclerosis at the pedicle entrance or core, and vertebrae with dense pedicles were excluded. Pre- and postoperative reconstructed CT scans were analyzed for pedicle screw positions according to a previously established grading system. Statistical analysis revealed an astonishingly high accuracy for the ATPS group with no critical screw position (0%) in axial or sagittal plane. In the pCPS group, 88.9% of screws inserted showed non-critical screw position, while 11.1% showed critical pedicle perforations. The usage of an ECD for posterior and anterior pedicle screw tract preparation with the exclusion of dense cortical pedicles was shown to be a successful and clinically sound concept with high-accuracy rates for ATPS and pCPS. In concert with fluoroscopic guidance and pedicle axis views, application of an ECD and exclusion of dense cortical pedicles might increase comfort and safety with the clinical use of pCPS. In addition, we presented a reasonable laboratory setting for the clinical introduction of an ATPS-plate system.European Spine Journal 08/2009; 18(9):1300-13. DOI:10.1007/s00586-009-1054-1 · 2.47 Impact Factor