Cervical Pedicle Screw Insertion Research Articles

Impact of osteosclerosis on cervical pedicle screw insertion using preoperative CT-based navigation.

Preoperative computed tomography (CT)-based navigation is used for cervical pedicle screw (CPS) insertion to mitigate the risk of spinal cord and vertebral artery injury. In vertebrae with osteosclerosis due to degeneration or other factors, however, probing may not proceed easily, with difficulty creating the CPS insertion hole. This study investigated the impact of osteosclerosis on the accuracy of CPS insertion. A total of 138 patients with CPS inserted at the C3-C7 level using preoperative CT navigation were retrospectively analyzed. Pre- and postoperative CT was employed to investigate screw position and Hounsfield unit (HU) values at the lateral mass to evaluate the degree of osteosclerosis in the CPS insertion pathway. Among 561 CPS insertions, the Grade 3 perforation rate was 1.8%, and the Grade 2 or higher perforation rate was 8.0%. When comparing insertions with and without CPS perforation, HU values were significantly higher in the perforation group (578 ± 191 vs. 318 ± 191, p < 0.01). The frequency of CPS insertion into the mid-cervical spine was also significantly greater in the perforation group (68.9% vs. 62.5%, p < 0.01). Logistic regression analysis revealed that a high HU value at the lateral mass (odds ratio 1.09, 95% confidence interval: 1.07-1.11, p < 0.01) was a significant independent factor associated with CPS deviation. The screw perforation rate of Grade 2 or higher in CPS insertion using preoperative CT-based navigation was 8.0%. Since osteosclerosis was an independent factor related to CPS deviation, additional care may be required during insertion into affected vertebrae.

Modified Tap-drilling Technique for Mid-cervical Pedicle Screw Placement: A Case Series of 473 Consecutive Screws.

Retrospective cohort study. To report our modified tap-drilling technique for mid-cervical pedicle screw placement and to evaluate its safety and accuracy. Cervical pedicle screw fixation, which provides a strong stabilization, has been a major concern due to the potential risks to neurovascular structures despite its increasing use. Several insertion techniques have been described so far to improve the cervical pedicle screw placement accuracy. This study retrospectively reviewed patients who underwent mid-cervical (C3-C6) pedicle screw fixation between September 2005 and September 2020. Laminectomy, laminoforaminotomy, or notch-referred anatomic landmark methods were used to adjust the entry point and the direction of the screws. After the cortical bone was removed at the entry point with a diamond burr, the cancellous bone was slowly drilled with a hand drill starting from 8 to 10 millimeters in length. Then, all of the bone walls were checked with a ball-tip probe to determine if there was any breach. The procedure was repeated several times. After completing the drilling, the screw was inserted without tapping. The breach rate of pedicle screws was analyzed on postoperative computed tomography scans. A total of 473 mid-cervical pedicle screws were placed in 122 consecutive patients. No navigation or computer-assisted system was used, and the first 2 authors inserted all of the screws. All patients completed the surgery, and no evident intraoperative complications occurred. Postoperative CT scans were obtained for 405 screws. Although deviation was observed for 131 pedicle screws, a critical deviation was observed for only 25 pedicle screws. Cervical pedicle screw insertion is a risky but applicable technique. Checking all of the bone walls with a ball-tip probe before gradually advancing the hand drill in small amounts, as presented in this article, may lead to the safe and effective placement of cervical pedicle screws.

CT-navigated C2 Pedicle Screw insertion using dynamic reference array on C2 spinous process: A Novel Technique

ntroduction: Spine surgeons have endeavoured to improve the accuracy of pedicle screw insertion. Computed tomography (CT) guided navigation has been helpful in precisely passing pedicle screws even further accurately but, there were shortcomings noted with the technique due to movement between reference frame and anatomical landmarks, especially in the cervical spine which led to injury of vital neurovascular structures. Thus, there was a need for developing a technique which would eliminate the inherent error due to movement in the vertebral body while passing screws. Research Question: Can using C2 spinous process as an attachment for the reference array improve accuracy of C2 pedicle screws. Material and Methods: We prospectively studied data of 10 patients (20 screws) in whom Computed tomography navigated C2 pedicle screws insertion was carried out using the reference array on C2 spinous process. Accuracy of pedicle screws were confirmed by post instrumentation Computed tomography scan immediately intra operatively. Results: With the presented technique overall breach rate was 5% with one screw having a medial breach of grade 1 with no incidence of neurovascular injury or need for further revision. Discussion and Conclusion: Results from this study shows better accuracy than other techniques described to pass C2 pedicle screws eliminating the error in movement from the cervical vertebrae and the reference frame being nearest to the C2 pedicle. Although there is a learning curve with the adoption of the navigation system, with experience, the challenges associated with Cervical pedicle screws (CPS) insertion can be overcome.

A rotary trans-osseous ultrasound blood flow detection method for endoscopic application

Due to the small size and proximity to the spinal cord and vertebral artery, the cervical pedicle screw fixation procedure remains to be challenging in clinical practice. The screw misplacement has a high probability of occurrence of severe complications. How to prevent direct injury to the vertebral artery is a vital study focus in cervical spine surgery. In this work, a trans-osseous ultrasound Doppler method is proposed to explore the possibility of detecting blood flow through thin cortical bone. A miniature single-element prototype probe with a center frequency of 2.5 MHz is prepared. With the classical pulse-echo acquisition, a Spectral Power Index (SPI) algorithm based on Spectral Doppler and sliding window traversal is designed to enhance the Doppler signal intensity. In vitro and in vivo experiments were conducted to investigate the feasibility of this method. The results of in vitro experiments suggest that the anticoagulated bovine blood flowing at a mean velocity of 15 cm/s to 80 cm/s is detectable when the thickness of cortical bone is 0.7 ± 0.1 mm. The in vivo experiment showed that the large blood vessel with a diameter of about 3 mm (radial artery) can be detected through thin cortical bone (thickness of 0.7 ± 0.1 mm). The proposed trans-osseous Doppler method achieves artery detection through thin cortical bone, which has demonstrated the possibility of intraoperative vessel pre-warning. The present study poses a promising strategy to reduce the risk of vertebral artery injury and misalignment rate in the cervical pedicle screw insertion procedure.

Application of a Navigated Drill for Cervical Pedicle Screw Insertion at C3-6.

Background Perforation of the cervical pedicle screw, especially lateral perforation, may lead to critical complications, such as vertebral artery injury. Sub-axial cervical spines (C3-6) are at risk of complications because these levels have limited area and angle. This study aimed to compare a navigated drill and a navigated probe for the insertion of cervical pedicle screws at C3-6. Methodology This retrospective study included 106 patients treated with cervical pedicle screws at C3-6. In total, 52 patients with 200 cervical pedicle screws using a navigated drill (group D) and 54 patients with 170 cervical pedicle screws using a navigated probe (group P) were compared. The perforation rate, anatomical medial angle of the pedicle, and actual angle of the screw were investigated using computed tomography. The planning error was defined as when the pedicle screw was applied for a small pedicle width of <3.5 mm. All perforations except for planning errors were defined as technical perforations. Results Grade 1 screw perforations were identified in 16 and 17 screws in groups D and P, respectively. Overall, 88% of the perforations were medial in group D, and 82% of perforations were lateral in group P. Technical perforations were found in 7/191 (3.7%, group D) and 15/168 (8.9%, group P) screws. There were no significant differences in the anatomical angle of the pedicle between the groups. The mean medial angle of the pedicle screws was 24.7° (group D) and 30.9° (group P) (p < 0.05). Conclusions The perforation rate of group D was less than half of that of group P. This was because a navigated drill was able to create a bony pilot hole at the hard medial cortical wall of the pedicle with a small medial angle, which was difficult to do with a navigated probe. A navigated drill can be useful for cervical pedicle screw insertion at C3-6 because of its easiness and safety.

Operative Effect Comparison of Flexible Drill Guiding vs. Traditional Drill Guiding Template for Lower Cervical Pedicle Screw Insertion: A Retrospective Analysis.

Accurately inserting pedicle screws is the key point of posterior pedicle screw fixation for lower cervical spine (C3-C7) instability. 3D printing technology can improve the accuracy of screw placement. This study compared the safety of 3D-printed flexible drill guiding template vs. traditional rigid drill guiding template for lower cervical pedicle screw insertion. This was a retrospective study. A total of 34 patients who underwent lower cervical pedicle screw fixation from March 2018 to May 2021 were enrolled in this study, and they were divided into the flexible drill flexible drill group and the traditional drill group. A total of 18 patients in the flexible drill flexible drill group underwent pedicle screw fixation assisted by 3D printed flexible drill guiding templates for the lower cervix, and 16 patients in the traditional drill group underwent pedicle screw fixation assisted by 3D printed regular drill guiding templates for the lower cervix. The length of the incision and intraoperative blood loss during surgery were recorded and compared for the two groups. The grade, deviation of the screw entry point, deviation of the screw medial angle and screw length were measured and compared after surgery for the two groups by independent-sample tests. There was a significant difference in the length of the incision and blood loss between the two groups (P < 0.05). There was a significant difference between the two groups for grade (P = 0.016). The deviation of the screw entry point was 0.65 ± 0.50 mm in the flexible drill group and 0.78 ± 0.83 mm in the traditional drill group. The deviation of the screw medial angle was 2.14 ± 1.78 in the flexible drill group and 4.23 ± 2.51 in the traditional drill group, with a significant difference between the two groups (P < 0.05). Compared with regular guiding techniques, lower cervical pedicle screw placement assisted by multistep navigation templates and flexible K-wires results in less trauma and better safety.

Cervical transpedicular irrigation and drainage in a patient with cervical spondylodiscitis after hypopharyngeal cancer treatment A case report

Cervical spondylodiscitis is a rare condition, but it is usually associated with rapid neurological deterioration so urgent surgical intervention mostly is indicated. We are presenting a case of cervical spondylodiscitis in a patient with a history of cancer hypopharynx. The patient had lateral pharyngotomy-wide excision followed by radiotherapy, but the presence of an epidural abscess made surgical intervention inevitable. Anterior cervical debridement might lead to esophageal perforation due to the extensive tissue scaring, so transpedicular irrigation and drainage technique was decided. Our emerging MPPP technique allows us to do safe and effective debridement, however, there were some concerns regarding cervical pedicle screw insertion. So, we are reporting the first case of transpedicular curettage and drainage using the freehand cervical pedicle screw insertion technique for the treatment of cervical SD. After surgery, the infection subsided with no need for further intervention. Ultimately, the transpedicular irrigation and drainage technique is effective and less aggressive treatment for cervical SD after hypopharyngeal cancer treatment.

Morphometric Study and Anatomical Variation with its Incidence of Foramina Transversaria on the Lower Cervical Vertebrae

Anatomical variation of the foramina transversaria (FT) is associated with vertebral neurovascular symptoms and can cause complications after lower spine surgery, especially cervical pedicle screw (CPS) insertion. FT variation has been documented and classified in various populations, as this information can help increase cervical stability in subaxial vertebral surgery. Although the morphometry of the upper cervical spine in Thai populations has been reported, there have yet been no studies examining the features of FT. The FT of dried cervical spines (C3-C7; left and right side; n = 107, male = 53 and female = 54) were examined for morphological variation, and their anteroposterior (AP) and transverse (T) diameters were measured using a digital vernier caliper. Morphometric data and variations were compared by sex and lateral side. It was that the C3-C6 FT in both sexes were round, and the C7 FT was elliptical with an oblique right side. FT diameters did not differ significantly by sex except for the AP diameters of C6-C7 and for T diameters of C4 and C7. The left AP diameters of C3-C6 were significantly longer than the right, as were the T diameters of C4 and C7 FT. Additionally, T diameter was significantly longer than that of the AP, except that of the left C6 in male spines, which did not differ from the AP. Most FT examined were round. These findings should be considered in the provisional diagnosis of vertebral neurovascular symptoms caused by FT variation as well as that of neurovascular damage after cervical pedicle screw placement.

Patient-Specific Drill Guide Template for Pedicle Screw Insertion into the Atlantoaxial Cervical Spine Using Stereolithographic Modeling: An In Vitro Study.

Cadaveric study. This study aimed to assess the accuracy and feasibility of cervical pedicle screw (CPS) insertion into the atlantoaxial cervical spine using a patient-specific drill guide template constructed from a stereolithographic model. CPS fixation is a widely accepted procedure for posterior cervical fixation because of its biomechanical advantages, particularly in the subaxial cervical region. The extremely narrow corridors of the atlantoaxial spine make CPS insertion more difficult, requiring the development of new tools to ensure accurate placement. Fifteen atlantoaxial cervical vertebra specimens from 15 cadavers were scanned into thin slices using computed tomography. Images of the cadaver spine were digitally processed and rendered stl files so that they could be printed to scale as threedimensional (3D) plastic models. Manually molded dental acrylic drill guide templates with pins inserted in the pedicles of the plastic cervical models were placed over the 3D printed models. The drill guide templates were used for precise placement of the drill holes in the pedicles of cadaveric specimens for pedicle screw fixation. The accuracy of screw placement was evaluated by an independent evaluator. A total of 60 pedicles (combined C1 and C2) from 15 cadaveric axial cervical vertebrae were evaluated. The total acceptable accuracy for pedicle screw insertion in the atlantoaxial cervical vertebrae is 95%. An accuracy rate of 100% was achieved for C1 while an acceptable accuracy rate of 90% was achieved for C2. The use of a patient-specific drill guide constructed using stereolithography improved the accuracy of CPS placement in a cadaveric model.

Comparison of the Safety and Efficacy of Three-Dimensional Guiding Templates and Free Hand Technique for Cervical Pedicle Screw Fixation: A Retrospective Study

Aim. To compare the safety and efficacy of computed tomography (CT)-assisted three-dimensional guiding templates (3DGTs) and free-hand (FH) technique for posterior cervical pedicle screw fixation in cervical spondylotic myelopathy (CSM) treatment. Methods. Thirty-five patients (216 screws) with CSM and developmental cervical stenosis were randomly divided into groups A (FH) and B (3DGTs). All patients underwent modified posterior surgery with cervical pedicle screw insertion (C1-7). Preoperative, postoperative, and intergroup comparisons of efficacy were evaluated using the visual analog scale (VAS), Japanese Orthopaedic Association (JOA), and Short Form 12 (SF-12) scores and JOA score improvement rate. Incidence of intra- and postoperative complications was analyzed. Postoperative cervical spine CT was performed to evaluate (i) the pedicle screws' deviation angle from the optimal path (sagittal deviation, α; coronal deviation angle, β), screw insertion point's deviation distance (d), and screw accuracy and (ii) the deviation angle and distance of screw entrance point of pedicle screws from the optimal channel. Results. All patients successfully completed the procedures. Groups A and B did not significantly differ in age, sex ratio, body mass index, operative time, or intraoperative blood loss amount. Postoperative VAS, JOA, and SF-12 scores improved in both groups. VAS, JOA, or SF-12 scores did not significantly differ between the 2 groups. The α, β, and d scores were lower in group B, but accuracy was higher in group B. Conclusions. 3DGTs and FH technique show comparable outcomes with respect to neurological improvement and safety.

O-Arm Navigated Cervical Pedicle Screw Fixation in the Treatment of Lower Cervical Fracture-Dislocation.

ObjectiveTo evaluate the safety and efficacy of cervical pedicle screw (CPS) placement with O‐arm navigation in the treatment of lower cervical fracture‐dislocation.MethodsA retrospective clinical study was performed involving 42 consecutive patients with lower cervical spine fracture‐dislocation who underwent CPS fixation surgery with O‐arm navigation (CPS group) or received conventional lateral mass screw (LMS) fixation surgery (LMS group) between August 2015 and August 2019. Accuracy of CPS position was evaluated by postoperative CT. The clinical parameters including preoperative and final follow‐up Japanese Orthopaedic Association (JOA) score and American Spinal Injury Association (ASIA) Impairment Scale, preoperative Sub‐axial Injury Classification (SLIC) score, number of fixation segments, operation time, intraoperative blood loss, injury mechanism, injury location, surgical complications were also assessed between the two groups.ResultsIn LMS group, the preoperative SLIC score was 7.5 ± 0.9, ASIA score improvement was 0.8 ± 0.5, JOA score improvement was 3.0 ± 1.8, mean operation time was 204 ± 89 min, intraoperative blood loss was 311 ± 127 ml. In CPS group, the preoperative SLIC score was 7.3 ± 1.2, ASIA score improvement was 0.9 ± 0.5, JOA score improvement was 3.2 ± 2.4, mean operation time is 241 ± 85 min, intraoperative blood loss is about 327 ± 120 ml. There was no significant difference in terms of above clinical parameters between the two groups (P > 0.05), the fixation segments in CPS group (3.5 ± 1.1) were less than that in LMS group (4.2 ± 0.7) (P = 0.037). The accuracy of CPS insertion was evaluated based on postoperative CT. Of all the 118 CPSs, 83 (70.3%) were defined as Grade 0; 27 (22.9%) as Grade 1; eight (6.8%) as Grade 2; and none as Grade 3. CPS malposition rate in this study was 6.8%. In this study, there was no direct intraoperative or postoperative complication caused by CPS or LMS insertion. All the operations were successfully completed in two groups. One of the patients in LMS group presented cerebrospinal fluid leak caused by bone fragment broken of the dural sac, which led to delayed incision healing. CPS group and LMS group both had two patients who suffered pulmonary infection after surgery. A total of 78.6% of the patients showed evidence of neurologic recovery. Satisfactory reduction was achieved in all cases and maintained throughout the follow‐up duration.ConclusionIn the treatment of lower cervical spine fracture‐dislocation, cervical pedicle screw insertion with O‐arm navigation is a safe and effective method for posterior fixation.

Safety and Efficacy of Intraoperative Doppler Sonography-Assisted Cervical Pedicle Screw Fixation-A Retrospective Comparison with Conventional Pedicle Screw Implantation.

A Retrospective Cohort Study. To introduce a new Doppler sonography-assisted pedicle screw fixation technique that enables vertebral artery (VA) monitoring during surgery and compares the accuracies of Doppler sonography-assisted cervical pedicle screw fixation and the conventional technique. This retrospective study was performed on 164 consecutive patients that underwent pedicle-based screw fixation from C2 to C6 between January 2013 and August 2020. Surgery was performed without intraoperative Doppler sonography in 84 cases (the Control group) or with intraoperative Doppler sonography in 80 cases (the Doppler group). Proper positioning of pedicle screws was graded, and the incidences of VA injury and screw breach in the Control and Doppler groups were compared. Three hundred and ninety-nine screws were placed in the 164 patients (Doppler, 186 screws; Control, 213 screws). The percentages of well-positioned screws in the two groups were significantly different (Doppler, 97.8%; Control, 85.0%). There were two cases of VA injury in the Control group, an incidence of 2.4%, but no case in the Doppler group. Doppler sonography can be used intraoperatively to help guide the trajectory of the cervical pedicle screw insertion. It can detect the VA inside the screw trajectory and may reduce the risk of VA injury during cervical pedicle screw fixation.

Minimally Invasive Subaxial Cervical Pedicle Screw Placement with Routine Fluoroscopy: Cadaveric Feasibility Study and Report of 6 Clinical Cases

Objective: Conventional cervical pedicle screw insertion necessitates extensive paraspinal muscle dissection and retraction in order to achieve the lateral to medial angulation needed to achieve the optimal screw trajectory. Minimally invasive transmuscular approach can comfortably achieve this angulation without significant injury to the midline structures and its musculo-ligamentous attachments.Methods: Minimally invasive cervical pedicle screws were inserted in 4 fresh frozen cadaveric specimens. Pre-procedure and post-procedure CT scans were done to assess the pedicle dimensions, suitability for screw insertion and integrity of the screws. The same technique was applied in a clinical cohort of six cases – 3 cases of traumatic subluxation; one case of traumatic vertebral fracture and 2 cases of infective facet destruction (Koch’s); with successful outcomes.Results: Among the 38 screws in the cadaver specimens, a total of 11 screws (28.9%) had breached the pedicle wall (Lateral wall breach–9; Medial wall breach–2). Of the 9 screws (23.6%) that had a lateral breach into the vertebral canal, 4 (10.5%) each had Grade IIa breach and one (2.6%) had Grade III breach. The mean transverse screw angle in the subset of pedicle screws with no breach was 34.1 whereas it was 22.1 in screws that had lateral breach and 43.6 in those with medial breach. Among the 22 screws inserted in the clinical cohort of 6 cases, 4 screws (18.1%) had breached the pedicle wall. All the identified breaches were in the lateral wall (Grade IIa – 3; Grade IIb–1; Grade III–nil). Conclusion: Minimally invasive subaxial pedicle screw insertion can be utilized in cases where a robust posterior fixation is required, either in isolation or as an adjunct to anterior surgery, in cases where a direct posterior decompression is not warranted. It is a safe and effective approach which minimizes injury to the paraspinal structures and midline attachments.

Medial Pedicle Pivot Point Using Preoperative Computed Tomography Morphometric Measurements for Cervical Pedicle Screw Insertion: A Novel Technique and Case Series.

This study describes a new and safe freehand cervical pedicle screw insertion technique using preoperative computed tomography (CT) morphometric measurements as a guide and a medial pedicle pivot point (MPPP) during the procedure. This study included 271 pedicles at 216 cervical spine levels (mean: 4.75 pedicles per patient). A pedicle diameter (PD) ≥ 3.5 mm was the cut-off for pedicle screw fixation. The presence and grade of perforation were detected using postoperative CT scans, where perforations were graded as follows: 0, no perforation; 1, perforation < 0.875 mm; 2, perforation 0.875–1.75 mm; and 3, perforation > 1.75 mm. The surgical technique involved the use of an MPPP, which was the point at which the lines representing the depth of the lateral mass and total length of the pedicle intersected, deep in the lateral mass. The overall success rate was 96.3% (261/271, Grade 0 or 1 perforations). In total, 54 perforations occurred, among which 44 (81.5%) were Grade 1 and 10 (18.5%) were Grade 2. The most common perforation direction was medial (39/54, 72.2%). The freehand technique for cervical pedicle screw fixation using the MPPP may allow for a safe and accurate procedure in patients with a PD ≥3.5 mm.

Comparison between O-arm Navigation and Conventional Fluoroscopic Guidance in Corrective Posterior Fixation for Cervical Spinal Injury.

Purpose : To compare the effectiveness of O-arm navigation with that of conventional fluoroscopic guidance in corrective posterior fixation for cervical spinal injury. Methods : This retrospective comparative study involved 11 consecutive patients who underwent corrective posterior fixation using O-arm navigation or conventional fluoroscopy for cervical spinal injury between February 2016 and May 2021. Patient-specific characteristics (age and sex), number of screws, number of pedicle screws, accuracy of pedicle screw insertion, number of vertebral bodies fixed, operating time, and length of hospital stay were analyzed using the t-test. A P-value < 0.05 was considered statistically significant. Results : Corrective posterior fixation was performed under O-arm navigation in 5 patients and under conventional fluoroscopic guidance in 6. A significantly greater number of pedicle screws was used in the O-arm group (6.4 vs 2.7, P = 0.046). According to the Neo classification for pedicle screw placement, there were no grade 2 or 3 breaches. No other items showed a significant difference between the groups (P > 0.05). Conclusion : O-arm navigation can improve the accuracy of cervical pedicle screw insertion. Its introduction could expand the indications for use of pedicle screws in posterior fixation of cervical spinal injury beyond those that are possible using conventional fluoroscopy. J. Med. Invest. 69 : 273-277, August, 2022.

The comparative accuracy and safety of fluoroscopic and navigation-based techniques in cervical pedicle screw fixation: systematic review and meta-analysis.

The goal of this study was to evaluate the comparative accuracy and safety of navigation-based approaches for cervical pedicle screw (CPS) placement over fluoroscopic techniques. A systematic search of the literature published between January 2006 and December 2019 relating to CPS instrumentation and the comparative accuracy and safety of fluoroscopic and intraoperative computer-based navigation techniques was conducted. Several databases, including the Cochrane Library, PubMed, and EMBASE, were systematically searched to identify potentially eligible studies. Data relating to CPS insertion accuracy and associated complications, in particular neurovascular complications, were extrapolated from the included studies and summarized for analysis. A total of 17 studies were identified from the search methodology. Eleven studies evaluated CPS placement under traditional fluoroscopic guidance and 6 studies addressed outcomes following navigation-assisted placement (3D C-arm or CT-guided placement). Overall, a total of 4278 screws were placed in 1065 patients. Misplacement rates of CPS were significantly lower (p < 0.0001) in navigation-assisted techniques (12.51% [range 2.5%-20.5%]) compared to fluoroscopy-guided techniques (18.8% [range 0%-43.5%]). Fluoroscopy-guided CPS insertion was associated with a significantly higher incidence of postoperative complications relating to neurovascular injuries (p < 0.038), with a mean incidence of 1.9% compared with 0.3% in navigation-assisted techniques. This systematic review supports a logical conclusion that navigation-based techniques confer a statistically significantly more accurate screw placement and resultant lower complication rates.

Accuracy of pedicle screw placement using patient-specific template guide system

BackgroundDespite repeated efforts for accurate cervical pedicle screw insertion, malpositioning of the inserted screw is commonly noted. To avoid neurovascular complications during cervical pedicle screw insertion, we have developed a new patient-specific screw guide system. This study aimed to evaluate the accuracy of cervical PS placement using the new patient-specific screw guide system. MethodsThis study is a retrospective clinical evaluation of prospectively enrolled patients. Seventeen consecutively enrolled patients who underwent posterior cervical fusion using the guide system were included. Firstly, three-dimensional planning of pedicle screw placement was done using simulation software. A screw guide for each vertebra was constructed preoperatively. A total of 77 screws were inserted with the guides. Postoperative computed tomography was used to evaluate pedicle perforation, and screw deviations, between the planned and actual screw positions, were measured. ResultsA total of 76 screws (98.7%) were completely inside the pedicle (C3-7), without neurovascular injuries. The mean screw deviations from the planned trajectory at the narrowest point of the pedicle and at the entry point in the axial and sagittal planes were 0.56 ± 0.43 mm and 0.43 ± 0.35 mm and 0.43 ± 0.30 mm and 0.63 ± 0.50 mm, respectively. There were no significant differences in any parameter at different spinal levels. Angular deviations in the sagittal and axial planes were 2.94 ± 2.04° and 2.53 ± 1.85°, respectively. Sagittal angular deviations tended to increase in the cranial vertebra (C3 and C4) compared to the middle cervical spine. ConclusionsWe demonstrated that our patient-specific screw guide is vital for guiding precise screw insertion in the cervical pedicle. This technique may be an effective solution for achieving precise screw insertion and reducing the incidence of complications.

Computed tomographic analysis of cervical spine pedicles in the adult Indian population.

Background: Cervical pedicle screw insertion is a technically demanding procedure that carries the risk of catastrophic damage to surrounding neurovascular structures. Here, we analyzed computed tomography (CT)-based three-dimensional cervical spine pedicle geometry to determine the level and sex-specific morphologic differences in the adult Indian population.Methods: The CT scans of 200 patients (2400 pedicles) without significant cervical spine pathology were collected. The mean pedicle width (PW), pedicle height (PH), pedicle axial length (PAL), and pedicle transverse angle (PTA) from C2 to C7 were measured.Results: The smallest mean PW was at C3 in both males (4.85 ± 0.73 mm) and females (4.31 ± 0.43 mm); 7.08% of all pedicles were found to have mean PW of <4 mm. The smallest mean PH was at C5 in both males (6.25 ± 0.67mm) and females (5.54 ± 0.52 mm). The smallest mean PAL was at C2 in both males (27.46 ± 1.69mm) and females (25.90 ± 1.88 mm). The mean PW, PH, and PAL were significantly greater in males than females at all levels (P < 0.05). The smallest mean PTA was at C3 in males (41.79 ± 2.53°) and at C7 in females (42.40 ± 2.27°).Conclusion: In the adult Indian population, the PW, PH and PAL were smaller than in the typical western population. Females had even smaller PW, PH and PAL as compared to males. We recommend that a small inventory of 3.5mm screws between 20mm to 30mm length be used in most cases where cervical pedicle screws are being used in the Indian population. However, individual vertebrae should be screened preoperatively with CT scans to exclude gross anatomical variations, especially in females and at the C3 and C4 levels.

Subaxial Cervical Pedicular Screw Insertion via the Nonanatomic Axis: Identification of Entry Point and Trajectory Based on a Radiographic Study and Workshop.

A radiological study and workshop. To propose a novel technique for subaxial cervical pedicle screw (CPS) insertion via the nonanatomic axis (nAA) and identify a new entry point (EP) and trajectory based on a radiological study. The new EP was determined to be the center of the upper half of the lateral mass, and the nAA was defined as the line connecting the EP and center of the pedicle. CT images of 493 subaxial cervical pedicles from 51 adults were utilized. The pedicle axis length (PAL/nPAL), pedicle transverse angle (PTA/nPTA), sagittal and transverse pedicle screw depth ratio (S-DO, T-DO), and sagittal and transverse angles (S-angle, T-angle) were measured in the anatomical axis (AA) and nAA. nAA-CPS insertions were conducted on dry specimens, and the positions of the screws were graded. The nPTA (22.35° ± 1.57°), nPAL (23.75 ± 2.07 mm), T-DO (45.61% ± 3.10%), and S-DO (70.46% ± 4.44%) of the nAA-CPS were significantly different from the PTA (41.86° ± 2.77°), PAL (31.98 ± 2.40 mm), T-DO and S-DO of the AA-CPS (both 100% in ideal conditions), respectively(P < .05). The T-angle and S-angle were 92.78° ± 3.07° and 92.18° ± 3.78°, respectively. A constant EP and consistent trajectory of the nAA-CPS identified by 2 perpendicular angles were summarized and utilized as the manipulation protocols of the workshop, and a perfect position was achieved in 80.00% (24/30) of screws. The nAA-CPS is a novel alternative to the classic CPS technique. A constant entry point and 2 perpendicular angles in the sagittal and transverse planes for identifying the trajectory of the nAA-CPS should be taken into account in the establishment of a manipulation protocol.

The accuracy of a novel pedicle screw insertion technique assisted by a special angular scale in the subaxial cervical spine using lateral mass as a reference marker

BackgroundPosterior cervical pedicle screw (CPS) internal fixation has better biomechanical stability than other posterior cervical fixation methods. However, this technique is limited in clinical practice due to the complex anatomical structure and the adjacent relationship of the cervical pedicle, and the high risk of neurovascular injury. The purpose of this study was to describe a novel subaxial CPS insertion technique assisted by a special angular scale using lateral mass as a reference marker and to evaluate the accuracy of CPS placement and the distribution characteristics of CPS misplacement.MethodsA total of 36 patients with subaxial cervical spine diseases who underwent posterior CPS fixation were consecutively selected. The optimal entry point on the posterior surface of the lateral mass was identified on the three-dimensional cervical model reconstructed from preoperative computed tomography (CT) images. The pedicle transverse angle (PTA) and pedicle-lateral mass angle (PLMA) were measured on the transverse and sagittal CT images respectively. The pedicle screws were inserted according to the preoperatively planned entry point and angles. We analysed the postoperative CT images for CPS misplacement rates and perforation directions following the Lee classification.ResultsOverall, 177 pedicle screws were inserted, of which 119 (67.2%) were classified as grade 0, 43 (24.3%) as grade 1, 12 (6.8%) as grade 2 and 3 (1.7%) as grade 3 by the postoperative CT images. The accuracy rate of CPS placement was 91.5%. Of the 15 misplaced pedicle screws (grades 2 and 3), 11 were lateral pedicle perforations, 3 were superior perforations and 1 was an inferior perforation. There were no neurovascular injuries related to CPS misplacement.ConclusionsWith our technique, the optimal entry point and two angles (PTA and PLMA) were identified for CPS insertion. The novel CPS insertion technique assisted by a special angular scale provides high accuracy and few complications.