Pedicle Screw Insertion Technique Research Articles

Does intraoperative navigation improve the accuracy of pedicle screw placement in the apical region of dystrophic scoliosis secondary to neurofibromatosis type I: comparison between O-arm navigation and free-hand technique.

To assess the accuracy of O-arm-navigation-based pedicle screw insertion in dystrophic scoliosis secondary to NF-1 and compare it with free-hand pedicle screw insertion technique. 32 patients with dystrophic NF-1-associated scoliosis were divided into two groups. A total of 92 pedicle screws were implanted in apical region (two vertebrae above and below the apex each) in 13 patients using O-arm-based navigation (O-arm group), and 121 screws were implanted in 19 patients using free-hand technique (free-hand group). The postoperative CT images were reviewed and analyzed for pedicle violation. The screw penetration was divided into four grades: grade 0 (ideal placement), grade 1 (penetration <2mm), grade 2 (penetration between 2 and 4mm), and grade 3 (penetration >4mm). The accuracy rate of pedicle screw placement (grade 0, 1) was significantly higher in the O-arm group (79%, 73/92) compared to 67% (81/121) of the free-hand group (P=0.045). Meanwhile, a significantly lower prevalence of grade 2-3 perforation was observed in the O-arm group (21 vs. 33%, P<0.05), and the incidence of medial perforation was significantly minimized by using O-arm navigation compared to free-hand technique (2 vs. 15%, P<0.01). Moreover, the implant density in apical region was significantly elevated by using O-arm navigation (58 vs. 42%, P<0.001). We reported 79% accuracy of O-arm-based pedicle screw placement in dystrophic NF-1-associated scoliosis. O-arm navigation system does facilitate pedicle screw insertion in dystrophic NF-1-associated scoliosis, demonstrating superiorities in the safety and accuracy of pedicle screw placement in comparison with free-hand technique.

Radiation Exposure during Pedicle Screw Placement using the Pediguard Pedicle Probe

Introduction Pedicle screws have been used for decades. Both the advantages and complications related to this technique are well documented. Screw malposition has been described in 10 to 55% of the cases, especially with the free-hand technique. Complications related to screw malposition are neurologic involvement in 1.8 to 6.9% of the cases, great vessel injury in 4.5%. Another consideration is the radiation exposure for the patients and the physicians. There are studies suggesting that spine surgeons can overwhelm the maximum radiation recommended during their whole life during 10 years of clinical practice. In addition to that, there is evidence showing that the radiation exposure during spine surgeries is between 10 to 12 times higher than the one in nonspine orthopedic procedures. Recently, the 2D fluoroscopy, intraoperative neurologic monitoring and electromyography, intraoperative CT scan, and navigation systems have reduced the incidence of these complications, but they can still happen. In the year 2000, a special pedicle probe was developed; it has a bipolar sensor on its tip that produces a direct current, thus, an electromagnetic field that is able to detect changes in the different tissues conductivity. This may help to reduce the time and radiation exposure during pedicle screw insertion. Material and Methods Prospective study that compares two pedicle screw insertion techniques in thoracic, lumbar spine, and in the sacrum; Group 1: X-rays and bipolar pedicle probe-guided screw insertion. Group 2: X-ray–guided pedicle screw insertion. The patients were randomly assigned to either group and all the surgeries were performed by the same surgical team. This study had the local ethics committee approval. Technique for group 1; Identification of the entry point for the pedicle screw in anteroposterior (AP) and lateral (lat) X-rays. The pedicle was penetrated using the bipolar probe. The wall integrity was verified. The pedicle screw insertion was done. AP and lat X-rays were taken. Technique for group 2; the same technique than group 1 using a regular probe, X-ray was used as needed. Results Overall, 20 patients were performed a surgery between 2013 and 2014. Of the 20 patients, 11 women and 9 men with an average age of 59.5 years (range, 37–84 years). Overall, eight patients had a spinal stenosis, five isthmic spondylolisthesis, five degenerative spondylolisthesis, and one transitional syndrome. A posterolateral fusion was performed in two patients; 14 posterolateral fusion and decompression, 4 posterolateral fusion and decompression and TLIF. Surgical time; 183 minutes (range, 110–240 minutes). Bleeding; 442 mL (range, 300–1,300 mL). Average X-ray use time per patient; Group 1: 12 patients, 64 screws, and 34.9 seconds. Group 2: 8 patients, 36 screws, and 17.4 seconds. Average time to put the screws; Group 1: 105 seconds, Group 2: 111.6 seconds. Conclusion Although the time spent in screw positioning was similar in both groups, there was a significant difference in the X-ray time between both the groups. The X-ray time required in group 2 almost doubled the X-ray time required in group 1 for an equivalent surgery. The use of bipolar probe during pedicle screw placement reduces both the patient and surgical team radiation exposure.

Accuracy of Pedicle Screw Placement in Dystrophic Neurofibromatosis Scoliosis: A Comparison between Free-Hand and 3D O-Arm Navigation Technique

Introduction Recently, the importance of intraoperative navigation in scoliosis surgery has been increasing. Multiple studies have proven the superiorities of computer-assisted scoliosis surgery. Using intraoperative 3D images for navigational purposes has several advantages and should increase the accuracy and safety of pedicle screw placement. The purpose of the present study was to assess the accuracy of O-arm navigation-based pedicle screw insertion in dystrophic neurofibromatosis scoliosis and compare it with free-hand pedicle screw insertion technique. Patients and Methods A total of 32 patients with dystrophic neurofibromatosis scoliosis were nonrandomly included in the two groups, one consisting of O-arm navigation-based pedicle screw insertion (13 patients, Group A) and the other with free-hand technique (19 patients, Group B). A total of 213 pedicle screws were placed in apical region, 92 pedicles were inserted assisted by O-arm navigation system and the rest were inserted by free-hand technique. The postoperative CT scan image were reviewed and analyzed for pedicle violation. The screw penetration was divided into the following four grades: grade 0 (ideal placement), grade 1 (penetration &lt; 2 mm), grade 2 (penetration between 2 and 4 mm), grade 3 (penetration &gt; 4 mm). Results The mean age in group A was 14.8 years (range,11–22 years), whereas in group B was 15.3 years (range, 6–30 years). The preoperative Cobb angle of the main curve in group A was 70.3 ± 6.7 degrees compared with 62.2 ± 8.7 degrees in group B. The correction rates were comparable between group A (75.7%) and group B (78.1%), and the difference was not statistically significant ( p &gt; 0.05). The overall perforation rate was 27.7% (59/213) in all 32 patients, and group A had a perforation rate of 20.7% (19/92) in comparison to 33.1% (40/121) noted in group B ( p &lt; 0.05, χ2 test) separately. Moreover, the lateral margin was the most common site of perforation for 73.4% (14/19) in group A and 50.0% (20/40) in group B. Conclusion O-arm navigation does provide superiority over conventional free-hand technique in terms of accuracy of pedicle screw insertion in dystrophic curves associated with neurofibromatosis type 1. The lateral cortex is the most common site of screw perforation in either technique.

Pedicle screw placement in the lumbar spine: effect of trajectory and screw design on acute biomechanical purchase.

OBJECT Low bone mineral density in patients undergoing lumbar spinal surgery with screws is an especially difficult challenge because poor bone quality can severely compromise the maximum achievable purchase of the screws. A relatively new technique, the cortical bone screw trajectory, utilizes a medialized trajectory in the caudocephalad direction to engage a greater amount of cortical bone within the pars interarticularis and pedicle. The objectives of this cadaveric biomechanical study were to 1) evaluate a cortical screw system and compare its mechanical performance to the traditional pedicle screw system; 2) determine differences in bone quality associated with the cortical screw trajectory versus the normal pedicle screw insertion technique; 3) determine the cortical wall breach rate with both the cortical and traditional screw trajectories; and 4) determine the performance of the traditional screw in the cortical screw trajectory. METHODS Fourteen fresh frozen human lumbar spine sections (L1-5) were used in this study (mean age 57 ± 19 years). The experimental plan involved drilling and tapping screw holes for 2 trajectories under navigation (a traditional pedicle screw and a cortical screw) in both high-and low-quality vertebrae, measuring the bone quality associated with these trajectories, placing screws in the trajectories, and evaluating the competence of the screw purchase via 2 mechanical tests (pullout and toggle). The 3 experimental variants were 1) traditional pedicle screws placed in the traditional pedicle screw trajectory, 2) traditional pedicle screws placed in the cortical screw trajectory, and 3) cortical screws placed in the cortical screw trajectory. RESULTS A statistically significant increase in bone quality was observed for the cortical trajectories with a cortical screw (42%; p < 0.001) and traditional pedicle screw (48%; p < 0.001) when compared to the traditional trajectory with a traditional pedicle screw within the high-quality bone group. These significant differences were also found in the lowquality bone cohort. All mechanical parameter comparisons (screw type and trajectory) between high-quality and lowquality samples were significant (p < 0.01), and these data were all linearly correlated (r ≥ 0.65) to bone mineral density. Not all mechanical parameters determined from pullout and toggle testing were statistically significant between the 3 screw/trajectory combinations. The incidence of cortical wall breach with the cortical or traditional pedicle screw trajectories was not significantly different. CONCLUSIONS The data demonstrated that the cortical trajectory provides denser bone that allows for utilization of smaller screws to obtain mechanical purchase that is equivalent to long pedicle screws placed in traditional pedicle screw trajectories for both normal- and low-quality bone. Overall, this biomechanical study in cadavers provides evidence that the cortical screw trajectory represents a good option to obtain fixation for the lumbar spine with low-quality bone.

Significance of preoperative planning simulator for junior surgeons' training of pedicle screw insertion.

A prospective study to access the significance of preoperative planning simulator for junior surgeons' training of pedicle screw insertion. Pedicle screw insertion is particularly challenging to carry out on patients with abnormal spine morphology, especially for the doctors who lack experience. Currently, preoperative planning for pedicle screw insertion is carried out using patient computed tomography and magnetic resonance imaging scans. In addition, there is no projection fluoroscopy provided to the user. The aim of this study was to investigate the feasibility and efficacy of a 3-dimensional, patient-specific volume rendering combined with the projection fluoroscopy simulator for training junior surgeons with no experience of pedicle screw insertion, and to help identify the role such simulation has in surgical education. Two junior surgeons with no experience of pedicle screw insertion were trained on the technique through the preoperative planning simulator; the operative time and the position of the pedicle screws were assessed before training (control group 1) and after training (experimental group) and compared with 2 senior spine surgeons with >10 years' experience of pedicle screw insertion (control group 2). The time of per pedicle screw insertion was 43.5±3.9 seconds in control group 1, 31.6±2.9 seconds in control group 2, and 50.8±3.7 seconds in experimental group. The relative position of the screw to the pedicle was graded regarding pedicle breach (I, no breach; II, <2 mm; III, 2-4 mm; IV, >4 mm). The pedicle breach grading I and II was 20 pedicle screws (20/56, 35.7%) in control group 1, 54 pedicle screws (54/56, 96.4%) in control group 2, and 44 pedicle screws (44/56, 78.6%) in the experimental group. There were significant differences between control group 1 and experimental group in the time of per pedicle screw insertion (P<0.001) and the rate of pedicle breach grading I and II (P<0.001). There were significant differences between control group 2 and experimental group in the time of per pedicle screw insertion (P<0.001) and the rate of pedicle breach grading I and II (P=0.004). The simulator offers many helpful features to the surgeon with respect to the surgical trainee learning the basic technique of pedicle screw insertion, using free-hand technique or under the guiding of intraoperative fluoroscopy. The surgical skills of the junior surgeons can be significantly improved through the training of simulator.

Are pedicle screw perforation rates influenced by registered or unregistered vertebrae in multilevel registration using a CT-based navigation system in the setting of scoliosis?

We developed a new multilevel registration technique for pedicle screw (PS) insertion that has the capability of registering three consecutive vertebrae simultaneously, using a reference frame set to one of the caudal vertebrae. PSs are inserted in the consecutive and adjacent one or two vertebrae. This study aimed to investigate the perforation rates of the registered and unregistered adjacent vertebrae and compare the perforation rate of the PS and insertion time per PS between the conventional and new techniques. Sixty-nine consecutive scoliosis patients who underwent PS insertion using multilevel registration were enrolled. The conventional and new techniques were used in 29 subjects, and in 40 subjects, respectively. The total numbers of PSs used were 375 and 492, respectively. Of the 492 PSs, 301 were inserted to the registered vertebrae and 191 were inserted to the unregistered adjacent vertebrae. The PS malposition on postoperative axial computed tomography was classified as grades 2 and 3 perforation, using the Rao classification. The perforation rate and insertion time per PS were compared between the conventional and new techniques. The perforation rates did not significantly differ between the registered and unregistered vertebrae (10.3 vs. 6.3 %,), and between the new and conventional techniques (8.7 vs. 9.6 %). The insertion time per PS was significantly shorter in the new technique than in the conventional technique (3.9 ± 1.0 vs. 4.9 ± 1.3 min; p < 0.001). The new technique may be less invasive and decrease operative time without compromising the accuracy of PS placement.

The difference in superior adjacent segment pathology after lumbar posterolateral fusion by using 2 different pedicle screw insertion techniques in 9-year minimum follow-up.

A prospective study was performed. To test the hypothesis that different pedicle screw insertion positions would increase the likelihood of superior adjacent segment degeneration (ASD). Lumbar fusion surgery is a widely accepted treatment of lumbar diseases, such as lumbar stenosis, trauma, tumor, and spondylolisthesis. Fusion and clinical success rates have increased because of improvements in instrumentation and bone graft material. In contrast, numerous complications and problems of fusion surgery have been reported, with ASD being one of the most important. This prospective study included 210 patients with low-grade isthmic spondylolisthesis. From January 1999 to December 2003, patients were randomized underwent posterolateral fusion using 2 different pedicle screw insertion positions. The patients were followed up postoperatively and were assessed with regard to radiological and clinical outcomes. Radiological outcomes were assessed mainly on the basis of disc degeneration, facet joint degeneration, and bone fusion. Clinical outcomes were evaluated mainly with the use of visual analogue scale for pain and the Oswestry Disability Index. A total of 178 of 210 (84.7%) patients were available for at least 9-year radiological and clinical follow-up data: 85.3% (87/102) patients in group A and 84.3% (91/108) patients in group B. Bone fusion was achieved in all patients at the last follow-up. ASD was proven in 110 (61.8%) of 178 patients. The incidences of radiographical and symptomatic ASD were 57.9% (103/178) and 3.9% (7/178), respectively. The incidence of ASD in group B was significantly lower than that in group A. Results of clinical outcomes showed lower visual analogue scale and Oswestry Disability Index scores in 2 groups than preoperative scores, but group B had greater improvement on the Oswestry Disability Index scores than group A in patients with ASD. The degeneration of superior adjacent segment is closely related to the position of the pedicle screws during lumbar fusion surgery. The position of the pedicle screw farther from the facet joint surface can reduce the degeneration of superior adjacent segment. 3.

Using the Freehand Pedicle Screw Placement Technique in Adolescent Idiopathic Scoliosis Surgery

Retrospective case series. This study evaluated the incidence of postoperative neurological symptoms after a freehand pedicle screw insertion technique in idiopathic posterior scoliosis surgery. It is generally accepted that pedicle screws can be inserted by a freehand technique in the thoracic and lumbar spine in patients with adolescent idiopathic scoliosis (AIS) with a very low frequency of major complications. The prevalence of clinically significant screw misplacement, with or without the need for revision surgery is less well defined. Between January 1, 2000, and October 2, 2012, five hundred fifty-nine patients with AIS had thoracolumbar posterior instrumented spine surgery at the Children's Hospital of Pittsburgh. Each patient's chart and radiographs were reviewed and only those with AIS were included. Patients with neuromuscular and syndromic diagnoses were excluded as well as those with congenital or traumatic etiologies, incomplete charts, less than 3 months of follow-up and those without pedicle screws. The records were studied for complaints of radicular pain, neurological deficit, or severe headache that could be indicative of potential screw misplacement. Four hundred eighty-one patients with 5923 pedicle screws met the inclusion criteria. Nine patients (1.9%) developed symptoms and underwent computed tomographic scanning. Six patients were found to have pedicle screw malposition (8 screws) and 3 of these patients underwent revision surgery. Of the 3 revision patients, 2 presented with radicular symptoms (leg pain) and 1 with an orthostatic headache due to cerebrospinal fluid leakage. At the final follow-up, all revision patients had complete symptom resolution. In total, there were 8 symptomatic, misplaced pedicle screws (0.14%) in 6 patients (1.25%). During a 12-year period in a dedicated pediatric orthopedic hospital using the freehand placement technique, the incidence of symptomatic misplaced pedicle screws was exceedingly low. 4.

Feasibility of bilateral crossing c7 intralaminar screws: a cadaveric study.

ObjectiveWhen the pedicle screw insertion technique is failed or not applicable, C7 intralaminar screw insertion method has been used as an alternative or salvage fixation method recently. However, profound understanding of anatomy is required for safe application of the bilaterally crossing laminar screw at C7 in clinic. In this cadaveric study, we evaluated the anatomic feasibility of the bilateral crossing intralaminar screw insertion and especially focused on determination of proper screw entry point.MethodsThe C7 vertebrae from 18 adult specimens were studied. Morphometric measurements of the mid-laminar height, the minimum laminar thickness, the maximal screw length, and spino-laminar angle were performed and cross-sectioned vertically at the screw entry point (spino-laminar junction). The sectioned surface was equally divided into 3 parts and maximal thickness and surface area of the parts were measured. All measurements were obtained bilaterally.ResultsThe mean mid-laminar height was 13.7 mm, mean minimal laminar thickness was 6.6 mm, mean maximal screw length was 24.6 mm, and mean spinolaminar angle was 50.8±4.7°. Based on the measured laminar thickness, the feasibility of 3.5 mm diameter intralaminar screw application was 83.3% (30 sides laminae out of total 36) when assuming a tolerance of 1 mm on each side. Cross-sectional measurement results showed that the mean maximal thickness of upper, middle, and lower thirds was 5.0 mm, 7.5 mm, and 7.3 mm, respectively, and mean surface area for each part was 21.2 mm2, 46.8 mm2, and 34.7 mm2, respectively. Fourteen (38.9%) sides of laminae would be feasible for 3.5 mm intralaminar screw insertion when upper thirds of C7 spino-laminar junction is the screw entry point. In case of middle and lower thirds of C7 spino-laminar junction, 32 (88.9%) and 28 (77.8%) sides of laminae were feasible for 3.5 mm screw insertion, respectively.ConclusionThe vertical cross-sectioned area of middle thirds at C7 spinolaminar junction was the largest area and 3.5 mm screw can be accommodated with 77.8% of feasibility when lower thirds were the screw entry point. Thus, selection of middle and lower thirds for each side of screw entry point in spino-laminar junction would be the safest way to place bilateral crossing laminar screw within the entire lamina. This anatomic study result will help surgeons to place the screw safely and accurately.

Percutaneous pedicle screw placement with computer-navigated mapping in place of Kirschner wires

Percutaneous pedicle screw insertion techniques are commonly used to treat a variety of spinal disorders. Typically, Kirschner (K)-wires are used to guide the insertion of taps and screws during placement since the normal anatomical landmarks are not visualized. The use of K-wires adds risks, such as vascular and nerve injuries as well as increased radiation exposure given the use of fluoroscopy. The authors describe a series of patients who had percutaneous pedicle screws placed using a new computer-assisted navigation technique without the need for K-wires. Minimally invasive percutaneous pedicle screw placement in the thoracic and lumbar spine was performed in a consecutive series of 15 patients for a variety of spinal pathologies. Intraoperative 3D CT images were obtained and used with a computer-assisted navigation system to insert an awl-tap into each pedicle. The tap location in the pedicle was marked with the navigation software, and the awl-tap was then removed. The navigation system was used to identify each landmark to insert the pedicle screw. Connecting rods were then inserted percutaneously under fluoroscopic guidance. Postoperative CT scans were obtained in each patient to evaluate screw placement. On postprocedure scanning, only 1 screw had a minor lateral and superior breach that was asymptomatic. To date, there have been no hardware failures. Percutaneous pedicle screws can be placed effectively and safely without the use of K-wires.

Development of a New Technique for Pedicle Screw and Magerl Screw Insertion Using a 3-Dimensional Image Guide

We developed a new technique for cervical pedicle screw and Magerl screw insertion using a 3-dimensional image guide. In posterior cervical spinal fusion surgery, instrumentation with screws is virtually routine. However, malpositioning of screws is not rare. To avoid complications during cervical pedicle screw and Magerl screw insertion, the authors developed a new technique which is a mold shaped to fit the lamina. Cervical pedicle screw fixation and Magerl screw fixation provide good correction of cervical alignment, rigid fixation, and a high fusion rate. However, malpositioning of screws is not a rare occurrence, and thus the insertion of screws has a potential risk of neurovascular injury. It is necessary to determine a safe insertion procedure for these screws. Preoperative computed tomographic (CT) scans of 1-mm slice thickness were obtained of the whole surgical area. The CT data were imported into a computer navigation system. We developed a 3-dimensional full-scale model of the patient's spine using a rapid prototyping technique from the CT data. Molds of the left and right sides at each vertebra were also constructed. One hole (2.0 mm in diameter and 2.0 cm in length) was made in each mold for the insertion of a screw guide. We performed a simulated surgery using the bone model and the mold before operation in all patients. The mold was firmly attached to the surface of the lamina and the guide wire was inserted using the intraoperative image of lateral vertebra. The proper insertion point, direction, and length of the guide were also confirmed both with the model bone and the image intensifier in the operative field. Then, drilling using a cannulated drill and tapping using a cannulated tapping device were carried out. Eleven consecutive patients who underwent posterior spinal fusion surgery using this technique since 2009 are included. The screw positions in the sagittal and axial planes were evaluated by postoperative CT scan to check for malpositioning. The screw insertion was done in the same manner as the simulated surgery. With the aid of this guide the pedicle screws and Magerl screws could be easily inserted even at the level where the pedicle seemed to be very thin and sclerotic on the CT scan. Postoperative CT scan showed that there were no critical breaches of the screws. This method employing the device using a 3-dimensional image guide seems to be easy and safe to use. The technique may improve the safety of pedicle screw and Magerl screw insertion even in difficult cases with narrow sclerotic pedicles.

O-Arm-based image guidance in minimally invasive spine surgery: Technical note

Three-dimensional (3D) image guidance technology is gaining popularity in spine surgery. The O-Arm navigation platform, which relies on cone-beam CT images acquired in the operative position, represents the most recent advancement in this field. We report our technique for MIS pedicle screw insertion using the O-Arm system and present two illustrative cases. We used percutaneous technique for short construct cases and “transfascial” technique for long-construct cases. O-Arm based navigation in minimally invasive spine surgery is safe and feasible. This technology may improve surgical accuracy and clinical outcomes but long term prospective studies are needed to validate this.

Insertion technique and clinical application of regional method axis pedicle screw

To explore the clinical efficacies and outcomes of regional method axis pedicle screw insertion technique. During the period of April 2004 to June 2010, a total of 23 cases with traumatic instability of upper cervical vertebrae were recruited. There were 19 males and 4 females with a mean age of 45.8 years. They underwent surgical operations after an excellent traction reduction of cervical vertebrae. The entry points were drawn on axial facet joint and all of them distributed in the region of upper inner 1/4 of lower articular process. So the regional method was employed to determine the entry point. All subjects underwent the reconstruction of posterior stability. Axial pedicle screws were inserted by the insertion technique of axial pedicle screw via the "regional method". The entry region was in the upper inner 1/4 area of lower articular process. The entry angle, medial inclination and superior inclination were determined by the direction of inner wall and upper wall of isthmus. Postoperative cervical radiography and CT examination were performed to confirm the screw position. Forty-six axial pedicle screws were implanted. No significant complications occurred. All screws stayed in excellent positions without the invasion of vertebral artery and spinal canal. The "regional method" insertion technique of axial pedicle screw require no memory of complex entry points and entry angle parameters. And there is no need of identifying the anatomical landmarks. Thus this approach is accurate, safe and suitable for most patients.

Video Object Tracking and Analysis for Computer Assisted Surgery

Pedicle screw insertion technique has made revolution in the surgical treatment of spinal fractures and spinal disorders. Although X- ray fluoroscopy based navigation is popular, there is risk of prolonged exposure to X- ray radiation. Systems that have lower radiation risk are generally quite expensive. The position and orientation of the drill is clinically very important in pedicle screw fixation. In this paper, the position and orientation of the marker on the drill is determined using pattern recognition based methods, using geometric features, obtained from the input video sequence taken from CCD camera. A search is then performed on the video frames after preprocessing, to obtain the exact position and orientation of the drill. An animated graphics, showing the instantaneous position and orientation of the drill is then overlaid on the processed video for real time drill control and navigation.

Assessment of pedicle screw pullout strength based on various screw designs and bone densities—an ex vivo biomechanical study

The pedicle screw fixation system has been used for various spinal disorders. Many studies have been conducted on the fixation ability of the pedicle screw, but variable results have been reported based on bone qualities, pedicle screw properties, insertion techniques, and experimental methods. An experimental and biomechanical study. To evaluate the geometric factors of screws affecting fixation ability after assessing pullout strength based on various pedicle screw designs and different bone densities. Nine types of pedicle screws were prepared according to the outer diameter shape (cylindrical or conical), the inner diameter shape (cylindrical or conical), and thread shape (V shape, buttress shape, and square shape). The pedicle screws were inserted into standardized polyurethane foams of Grades 5, 15, and 20. The pullout strength of each pedicle screw was determined using an MTS 858 machine (Material Testing System Corp., Minneapolis, MN, USA), and the results were analyzed statistically. Pullout strength based on the shape of thread was the highest in the V shape and lowest in the square shape for all foam grades (p<.05). The outer cylindrical and inner conical shape of pedicle screw showed the highest pullout strength in Grades 5 and 15 foam (p<.05). An outer cylindrical and inner conical shape with a V-shaped thread showed the highest pullout strength in all foam grades (p<.05). Pedicle screw with an outer cylindrical and inner conical configuration witha V-shaped thread may have maximum pullout strength, regardless of bone density.

Clinically relevant complications related to pedicle screw placement in thoracolumbar surgery and their management: a literature review of 35,630 pedicle screws

The technique of pedicle screw insertion is a mainstay of spinal instrumentation. Some of its potential complications are clinically relevant and may require reoperation or further postoperative care. A literature search was performed using MEDLINE (between 1999 and June 2011) for studies on pedicle screw placement in thoracolumbar surgery. The authors included randomized controlled trials, case-control studies, and case series (≥ 20 patients) from the English-, German-, and French-language literature. The authors assessed study type, the number of patients, the anatomical area, the number of pedicle screws, duration of follow-up, type of pedicle screw placement, incidence of complications, and type of complication. The management of specific complications is discussed. Thirty-nine articles with 46 patient groups were reviewed with a total of 35,630 pedicle screws. One study was a randomized controlled trial, 8 were case-control studies, and the remaining articles were case series. Dural lesions and irritation of nerve roots were reported in a mean of 0.18% and 0.19% per pedicle screws, respectively. Thirty-two patients in 10 studies (of 5654 patients from all 39 studies) required further revision surgeries for misplaced pedicle screws causing neurological problems. None of the analyzed studies reported vascular complications, and only 2 studies reported visceral complications of clinical significance. Pedicle screw placement in the thoracolumbar region is a safe procedure with an overall high accuracy and a very low rate of clinically relevant complications.

Accuracy of pedicle screw placement: a systematic review of prospective in vivo studies comparing free hand, fluoroscopy guidance and navigation techniques

With the advances and improvement of computer-assisted surgery devices, computer-guided pedicle screws insertion has been applied to the lumbar, thoracic and cervical spine. The purpose of the present study was to perform a systematic review of all available prospective evidence regarding pedicle screw insertion techniques in the thoracic and lumbar human spine. We considered all prospective in vivo clinical studies in the English literature that assessed the results of different pedicle screw placement techniques (free-hand technique, fluoroscopy guided, computed tomography (CT)-based navigation, fluoro-based navigation). MEDLINE, OVID, and Springer databases were used for the literature search covering the period from January 1950 until May 2010. 26 prospective clinical studies were eventually included in the analysis. These studies included in total 1,105 patients in which 6,617 screws were inserted. In the studies using free-hand technique, the percentage of the screws fully contained in the pedicle ranged from 69 to 94%, with the aid of fluoroscopy from 28 to 85%, using CT navigation from 89 to 100% and using fluoroscopy-based navigation from 81 to 92%. The screws positioned with free-hand technique tended to perforate the cortex medially, whereas the screws placed with CT navigation guidance seemed to perforate more often laterally. In conclusion, navigation does indeed exhibit higher accuracy and increased safety in pedicle screw placement than free-hand technique and use of fluoroscopy.

Cervical pedicle screw insertion using a gutter entry point at the transitional area between the lateral mass and lamina

The purpose of this study was to describe a free-hand pedicle screw insertion technique and to evaluate the accuracy of pedicle screw placement and validity of pedicle screw fixation in patients with subaxial cervical spine injuries. We retrospectively reviewed 32 consecutive patients with subaxial cervical spine injuries who underwent posterior cervical fixation using our cervical pedicle screw (CPS) insertion technique. We also assessed the clinical and radiological outcomes and the accuracy of pedicle screw placement. The mean preoperative kyphosis was 4.0°, which was corrected to -5.2° after the operation, and the mean kyphosis angle was -4.4° at the final follow-up. The mean preoperative disc height ratio was 81.9%, and it improved to 105.4% after the operation, which was maintained until the final follow-up measurement of 103.4%. Bony union was achieved, and there were no instrumentation failures in any patient. Overall, 127 pedicle screws were inserted, of which 112 (88.1%) were classified as grade 1 (exact intrapedicular screw positioning), 10 (7.8%) as grade 2 (perforation <50% of the screw diameter), and 5 (3.9%) as grade 3 (perforation more than 50% of the screw diameter). In our technique, a gutter is created using a high-speed burr at the transitional area between the lateral mass and lamina similar to the procedure in double-door laminoplasty to identify an entry point for CPS insertion. It is easy for general spine surgeons to identify a CPS insertion entry point using our technique.

Exploring the Role of 3-Dimensional Simulation in Surgical Training

Randomized control study assessing the efficacy of a pedicle screw insertion simulator. To evaluate the efficacy of an in-house developed 3-dimensional software simulation tool for teaching pedicle screw insertion, to gather feedback about the utility of the simulator, and to help identify the context and role such simulation has in surgical education. Traditional instruction for pedicle screw insertion technique consists of didactic teaching and limited hands-on training on artificial or cadaveric models before guided supervision within the operating room. Three-dimensional computer simulation can provide a valuable tool for practicing challenging surgical procedures; however, its potential lies in its effective integration into student learning. Surgical residents were recruited from 2 sequential years of a spine surgery course. Patient and control groups both received standard training on pedicle screw insertion. The patient group received an additional 1-hour session of training on the simulator using a CT-based 3-dimensional model of their assigned cadaver's spine. Qualitative feedback about the simulator was gathered from the trainees, fellows, and staff surgeons, and all pedicles screws physically inserted into the cadavers during the courses were evaluated through CT. A total of 185 thoracic and lumbar pedicle screws were inserted by 37 trainees. Eighty-two percent of the 28 trainees who responded to the questionnaire and all fellows and staff surgeons felt the simulator to be a beneficial educational tool. However, the 1-hour training session did not yield improved performance in screw placement. A 3-dimensional computer-based simulation for pedicle screw insertion was integrated into a cadaveric spine surgery instructional course. Overall, the tool was positively regarded by the trainees, fellows, and staff surgeons. However, the limited training with the simulator did not translate into widespread comfort with its operation or into improvement in physical screw placement.

CT-based Patient-specific Simulation Software for Pedicle Screw Insertion

Development of a 3-dimensional, patient-specific simulator for pedicle screw insertion. To allow the user to practice the insertion of pedicle screws into a 3-dimensional model of a patient-specific spine, and have both visual and quantitative feedback provided to the user. The goal is to better prepare surgeons to perform pedicle screw insertion surgery and help reduce the risk of pedicle screw misplacement. Pedicle screw insertion is particularly challenging to carry out on patients with abnormal spine morphology. Currently, preoperative planning for pedicle screw insertion is carried out using patient computed tomography and magnetic resonance imaging scans. In addition, once screws are inserted, there are no quantitative metrics against which to measure the results. The simulator was developed in the TCL scripting language as a graphical plug-in for the commercial visualization software AmiraDev 3.11. Surgical simulation uses a 3-dimensional model of patient's spine developed from the patient's computed tomography scan. Pedicle screw insertion can be practiced using pedicle screws of various sizes and analyzed in both 2-dimension and 3-dimension. Quantitative feedback is provided to the user in the form of anatomic lengths and angles, relative purchase of inserted screws, and a screw placement grading system. The software allows the user to adjust the translucency of a patient's spine to develop a better sense of the trajectories and depths involved with performing pedicle screw insertion on a patient. The simulator offers many helpful features to the surgeon with respect to complex cases and to the surgical trainee learning the basic technique of pedicle screw insertion. A study is currently underway to evaluate the efficacy of the simulator as a teaching tool for surgical trainees in placing pedicle screws. Future work will focus on the transfer of the software to a stand-alone platform.