Posterior thoracic segmental pedicle screw instrumentation: evolving methods of safe and effective placement

Pedicle Screw Placement Aided by C-Arm Fluoroscopy: A "Nevermore without" Technology to Pursue Optimal Spine Fixation

The surgical technique and the intraoperative technology that support spinal pedicle screw placement have consistently evolved over the past decades to decrease the misplacement rate of pedicle screws. We retrospectively evaluated our case series by analyzing the period 2016-2020. Patients undergoing pedicle screw fixation for cervical, thoracic, or lumbar spine degenerative diseases have been included. Surgery was carried out with the aid of intraoperative 3D C-arm fluoroscopy to assess and optimize screw placement and/or correct possible mispositioning. Each patient underwent a postoperative CT scan. Our aim was to evaluate the safety and accuracy of pedicle screw placement and estimate the variation in mispositioning rates. We carried out 329 surgical procedures, as follows: 70 cervical, 78 thoracic spine, and 181 lumbar spine surgeries. An excellent overall pedicle screw positioning was obtained, with slight differences between the cervical (98.6%), thoracic (100%), and lumbar (98.9%) tracts. Accordingly, only three patients required a revision surgery owing to mispositioning (0.91%). In particular, intraoperative C-arm fluoroscopy significatively improved the accuracy of thoracic screw positioning, as shown by postoperative CT scans. Our experience proves the crucial role of intraoperative C-arm fluoroscopy in pursuing optimal technical results and improving patient outcomes at follow-up.

The Transverse Process Trajectory Technique: An Alternative for Thoracic Pedicle Screw Implantation-Radiographic and Biomechanical Analysis

BACKGROUND

This study evaluates the accuracy, biomechanical profile, and learning curve of the transverse process trajectory technique (TPT) compared to the straightforward (SF) and in-out-in (IOI) techniques. SF and IOI have been used for fixation in the thoracic spine. Although widely used, there are associated learning curves and symptomatic pedicular breaches. We have found the transverse process to be a reproducible pathway into the pedicle.

METHODS

Three surgeons with varying experience (experienced [E] with 20 years in practice, surgeon [S] with less than 10 years in practice, and senior resident trainee [T] with no experience with TPT) operated on 8 cadavers. In phase 1, each surgeon instrumented 2 cadavers, alternating between TPT and SF from T1 to T12 (n = 48 total levels). In phase 2, the E and T surgeons instrumented 1 cadaver each, alternating between TPT and IOI. Computed tomography scans were analyzed for accuracy of screw placement, defined as the percentage of placements without critical breaches. Axial pullout and derotational force testing were performed. Statistical analyses include paired t test and analysis of variance with Tukey correction.

RESULTS

Overall accuracy of screw placement was comparable between techniques (TPT: 92.7%; SF: 97.2%; IOI: 95.8%; P = .4151). Accuracy by technique did not differ for each individual surgeon (E: P = .7733; S: P = .3475; T: P = .4191) or by experience level by technique (TPT: P = .1127; FH: P = .5979; IOI: P = .5935). Pullout strength was comparable between TPT and SF (571 vs 442 N, P = .3164) but was greater for TPT versus IOI (454 vs 215 N, P = .0156). There was a trend toward improved derotational force for TPT versus SF (1.06 vs 0.93 Nm/degrees, P = .0728) but not for TPT versus IOI (1.36 vs 1.16 Nm/degrees, P = .74). Screw placement time was shortest for E and longest for T for TPT and SF and not different for IOI (TPT: P = .0349; SF: P < .0001; IOI: P = .1787) but did not vary by technique.

CONCLUSIONS

We describe the TPT, which uses the transverse process as a corridor through the pedicle. TPT is an accurate method of thoracic pedicle screw placement with potential biomechanical advantages and with acceptable learning curve characteristics.

CLINICAL RELEVANCE

This study provides the surgeon with a new trajectory for pedicle screw placement that can be used in clinical practice.

Esophageal perforation following pedicle screw placement for the treatment of upper thoracic spinal tuberculosis: a case report and review of the literature

Background

The technique of posterior pedicle screw fixation has already been widely applied in the treatment of upper thoracic spinal tuberculosis. However, lesions of tuberculosis directly invade the vertebrae and surrounding soft tissues, which increases the risk of esophageal perforation induced by the posterior pedicle screw placement. Herein, we report the first case of esophageal perforation following pedicle screw placement in the upper thoracic spinal tuberculosis, and describe the underlying causes, as well as the treatment and prognosis.

Case presentation

A 48-year-old female patient with upper thoracic spinal tuberculosis presented sputum-like secretions from the wound after she was treated with one-stage operation through the posterolateral approach. Endoscopy was immediately conducted, which confirmed that the patient complicated with postoperative esophageal perforation caused by screws. CT scan showed that the right screw perforated the anterior cortex of the vertebrae and the esophagus at the T4 level. Fortunately, mediastinal infection was not observed. The T4 screw was removed, Vacuum Sealing Drainage (VSD) was performed, and jejunum catheterization was used for enteral nutrition. After continuous treatment with sensitive antibiotics for 2.5 months and 5 times of VSD aspiration, the infected wound recovered gradually. With 18-month follow-up, the esophagus healed well, without symptoms of dysphagia and stomach discomfort, and CT scan showed that T2–4 had complete osseous fusion without sequestrum.

Conclusion

Tuberculosis increases the risk of postoperative esophageal perforation in a certain degree for patients with upper thoracic tuberculosis. The damages to esophagus during the operation should be prevented. The screws with the length no more than 30 mm should be selected. Moreover, close monitoring after operation should be conducted to help the early identification, diagnosis and treatment, which could help preventing the adverse effects induced by the delayed diagnosis and treatment of esophageal perforation.

Incidence of pedicle breach following open and minimally invasive spinal instrumentation: A postoperative CT analysis of 513 pedicle screws applied under fluoroscopic guidance

Background

Even though pedicle screw application is a common procedure, and in-spite of spine surgeons being proficient with the technique, mal-positioning of pedicle screws can still occur. We intend to determine by postoperative CT analysis, the incidence of pedicle screw breach in the thoracolumbar spine despite satisfactory intraoperative placement confirmed by fluoroscopy.

Materials and methods

Consecutive patients diagnosed with thoracolumbar fractures who underwent open or minimally invasive posterior stabilization under fluoroscopic guidance were retrospectively reviewed. Postoperative CT scans of patients were analysed to determine the incidence of pedicle breach despite satisfactory intraoperative placement, and also to determine the factors that can predict a breach during intraoperative assessment.

Results

A total of 61 patients with 513 thoracolumbar pedicle screws were available for analysis. Based on our postoperative CT assessment, 28 screws (5.5%; 18 thoracic screws; 10 lumbar screws) had breached the pedicle. There were 14 minor (<3 mm) and 14 major (≥3 mm) breaches. The minimally invasive technique had a significantly lower breach rate compared to open surgery (1.9% vs. 7.9%). By retrospectively analysing the intra-operative fluoroscopic images, we determined certain parameters that could predict a breach during surgery.

Conclusion

Pedicle breaches can still be present despite satisfactory placement of screws visualized intra-operatively. A medial breach is most likely when the length of the pedicle screw spans only up to 50% of the vertebral body as seen on the lateral view but the pedicle screw tip has already transgressed the midline as seen on an AP view. A lateral breach is likely when the tip of the pedicle screw is overlapped by the screw head or is only minimally visualized on an AP view.

Percutaneous Pedicle Screw Placement Aided by a New Drill Guide Template Combined with Fluoroscopy: An Accuracy Study

Objective

To evaluate the accuracy of percutaneous pedicle screw (PPS) placement aided by a new drill guide template.

Methods

The patients were divided into guide template group and conventional perspective group. In the conventional perspective group, the screws were placed by hand under fluoroscopy. In the guide template group, the screw placement was aided by a new drill guide template, and the drill guide template is designed according to the patient's ideal pedicle screw, but not based on skin morphology. The accuracy was evaluated by comparing the following parameters between the two groups: pedicle breach level, inclination angle deviation between the left and right screws, sagittal angle deviation between the left and right screws, and position deviation of the left and right screw entry points. The consistency of the postoperative screw angle and the corresponding guide template inclination angle was compared in the guide template group. The operative time, blood loss, and radiation times were compared between the groups.

Results

A total of 146 patients (876 screws) were enrolled in our study including 79 (474 screws) in the guide template group and 67 (402 screws) in the conventional perspective group. The pedicle breach level in the guide template group (22/474) was significantly lower than that in the conventional perspective group (47/402) (P < 0.05). The position and direction deviations of the left and right screws in the guide template group (2.06 ± 1.02 mm, 1.23 ± 1.25 mm, 1.83° ± 1.49°) were significantly less than those in the conventional perspective group (5.33 ± 2.99 mm, 4.32 ± 3.25 mm, 2.87° ± 1.56°). The operation time, blood loss, and radiation times were significantly lower in the guide template group (80.49 ± 9.14 min, 50.42 ± 8.9 mL, 11.02 ± 2.44) than those in the conventional perspective group (108.1 ± 21.18 min, 71.7 ± 17.09 mL, 23.53 ± 4.54). There were no significant differences between the postoperative screw angle and the corresponding guide template angle in the guide template group.

Conclusion

PPS placement aided by a new drill guide template yielded higher screw accuracy and less operative time, blood loss, and radiation exposure than traditional screw placement.

Contribution of Dynamic Surgical Guidance to the Accurate Placement of Pedicle Screws in Deformity Surgery: A Retrospective Case Series

OBJECTIVE

We assessed the contribution of a dynamic surgical guidance (DSG) probe in the accurate placement of thoracic and lumbar pedicle screws (PSs) in patients with spinal deformity.

METHODS

A retrospective review was performed of 98 patients (104 procedures) with various spinal deformities, who had received posterior instrumentation with PSs inserted using either DSG or the conventional free-hand (FH) technique. A total of 882 PSs were inserted using DSG (DSG group) and 603 using the FH technique (FH group). The DSG probe was preferably chosen for large osteosyntheses and severe deformities. Two neurosurgeons, unaware of the surgical groups, reviewed all the intraoperative computed tomography scans and assessed all the PS placements.

RESULTS

Of the PSs used, 95.4% in the DSG group and 92.2% in the FH group were correctly placed (P = 0.0136). The difference in screw placement accuracy was greater at the thoracic level (DSG group, 92.5%; vs. FH group, 87.0%; P = 0.0310) than at the lumbar level (DSG group, 98.0%; vs. FH group, 95.4%; P = 0.0385). Severe (>4 mm) lateral breaches occurred in 24 cases (4.0%) in the FH group but in only 5 (0.6%) in the DSG group (P < 0.0001). No severe medial breach was observed in either group.

CONCLUSIONS

Despite having more patients with severe deformities in the DSG group, PS insertion was significantly more accurate with DSG. This technique also reduced the severe unacceptable lateral misplacement rate (>4 mm) and, consequently, the incidence of intraoperative screw revisions even in patients with severe deformities.

Transmuscular Ultrasonography of the Placement of Thoracolumbar Pedicle Screws: A Cadaveric Study

BACKGROUND

Transpedicular screw fixation has a biomechanical advantage of improving fusion rates. In posterior thoracolumbar immobilization, a large number of screws cause perforation to the pedicle or vertebral body. Radiography and computed tomography (CT) have been used to minimize this complication. The ability of ultrasound (US) to detect the pedicle breach during placement of the screw is unknown. The aim of this study was to evaluate the sensitivity of US for detecting breaches.

METHODS

A B-type transducer was used to scan 216 titanium pins inserted into cadaveric pedicles. Of the pins, 180 were intentionally misplaced: 90 pins breached the lateral wall of the pedicle, and 90 pins pierced the anterior wall of the vertebral body. US images were reviewed by 3 examiners blinded to both the procedure and the corresponding CT findings. The perforation length of pins was measured by 3 radiologists on CT images.

RESULTS

CT data were divided into 2 groups. In group 1 (perforation length 0-2 mm), sensitivity of US for detecting lateral wall and anterior wall perforation was 80.95% and 76.42%, respectively; in group 2 (perforation length 2-4 mm), sensitivity was 94.79% and 91.93%. Overall sensitivity of US to detect lateral wall and anterior wall perforation was 89.63% and 86.30%, respectively. The sensitivity of US for detecting perforation was greater in the lateral wall than in the anterior wall. Sensitivity of US was greater in group 2 than group 1 for both lateral and anterior perforation.

CONCLUSIONS

US can be applied to detect perforation of ≤4 mm. Use of US may improve patient safety.

Sagittal orientation and uniform entry for thoracic pedicle screw placement with free-hand technique: A retrospective study on 382 pedicle screws

BACKGROUND

One of the most important factors in obtaining a successful outcome in spinal surgery is appropriate placement of the pedicle screw. A number of different techniques are used to achieve successful pedicle screw placement. The free-hand technique has the advantage of no requirement for radiation exposure, but its success is highly dependent on surgeon experience. Here, we describe our entry point and perioperative sagittal orientation method, and evaluate postoperative sagittal alignment of pedicle screws with the free-hand pedicle screw placement technique.

MATERIALS AND METHODS

Eighty-two patients undergoing spinal surgery between 2015 and 2016 were included in this study. Pedicle screw placement was evaluated retrospectively on postoperative anterior-posterior (A-P) and lateral load-bearing radiographs of the entire spinal column. The vertebral body was divided into five areas in the lateral plane. Sagittal orientation of the pedicle screws on lateral radiographs was evaluated by two spine surgeons with 3 years of experience and one radiologist experienced in musculoskeletal radiology, with each observer evaluating the image twice according to a 1-month interval.

RESULTS

A total of 382 pedicle screws were evaluated. There was no statistically significant difference between the first and second measurements, performed by individual observers, and there was good concordance among the three observers.

CONCLUSIONS

Use of a uniform entry point at all levels may increase the effectiveness of the free-hand technique and decrease the pedicle screw misplacement rate. Our technique may standardize the free-hand technique, which does not require radiation exposure, and make it more practical to apply uniformly.

Retrospective Review on Accuracy: A Pilot Study of Robotically Guided Thoracolumbar/Sacral Pedicle Screws Versus Fluoroscopy-Guided and Computerized Tomography Stealth-Guided Screws

Introduction Pedicle screw insertion is the mainstay of thora-cic and lumbosacral posterior spinal instrumentation. However, it may be associated with complications such as screw mal-positioning. The purpose of this study was to develop a pilot study to compare the accuracy of robot-guided screw insertion versus hand-guided screw placement for spinal instrumentation. The hand-guided screws were placed with assistance from computerized tomography (CT) stealth guidance or fluoroscopy. Materials and methods A retrospective analysis of medical records was done for all patients that had pedicle screw insertion for instrumentation between the dates of December 2013 and January 2016 with post-screw placement CT imaging. The analysis was conducted on screw accuracy between the two categories based on the Gertzbein-Robbins classification. Results A total of 49 screws were analyzed for accuracy in six patients. There was no statistically significant difference between the accuracy of hand-placed pedicle screws versus the robotically placed screws (p = 0.311). There was no statistically significant difference in blood loss (p = 0.616), length of procedure (p = 0.192), or post-operative length of stay (p = 0.587). Conclusion The findings of our pilot study agree with most prior studies that there was no statistically significant difference in the accuracy of pedicle screw placement between the two methods of screw placement. Therefore, the techniques are equivocal in accuracy. The new technology (robotic-guidance) is as safe as conventional techniques for screw placement. Just like in any surgery, the technique preference should remain surgeon dependent. The results are only from a small sample size in the development of a pilot study so a strong reliance on the data would not be suggested. The study was a preliminary study that will be used as a template and learning process to create a future prospective study to investigate CT stealth and robotically guided screw placement versus "free hand" guided screws.

Inserting pedicle screws in lumbar spondylolisthesis - The easy bone conserving way

BACKGROUND

Pedicle screw fixation in high grade lumbar listhetic vertebral body has been nightmare for Orthopaedic and spine surgeons. This is because of abnormally positioned listhetic pedicles and non-visualization of pedicle in conventional image intensifier (C-Arm). This results into increased surgical time, more blood loss, radiation exposure and more chances of infection. To overcome this problem, we have devised a new Technique of putting of pedicle screw fixation in listhetic vertebrae.

METHODS

Total 20 patients of average age of 42 (25-56) were included during 2010 to 2015. Listhesis was classified according to etiology, Meyerding grading and DeWald modification of Newman criteria used for assessment of severity for spondylolisthesis on standing X-ray lumbosacral spine. Patients satisfying following criteria were considered for surgery. Age more than 20 years, with single involvement of either L4-5/L5-S1, high grade spondylolisthesis (≥ 50% Meyerding grade), unresolving radiculopathy, cauda equina syndrome or pain with and without instability not relieved by 6 months of conservative treatment. According to Meyerding radiographic grading system,10 patients were of type II and 8 of type III and 2 of type IV. Treatment given was pedicle screw fixation, reduction of listhesis vertebra and spinal fusion with our technique. PLT was done in 10 cases and transforaminal lumbar interbody fusion (TLIF) in the other 10 cases.

RESULTS

Mean follow up duration was 2 years (range 1.3-3.3 year). The average preoperative LBP VAS of low back pain were 6.7 and average LP VAS for leg pain 5.7. Postoperatively at final follow up there was reduction of LBP VAS to 2.2 and LP VAS to 0.5. There was rapid reduction in their LBP VAS in first two visits at 4 weeks and in LP VAS in first three visits at 8 weeks. The pain-free walking distance improved significantly. The average pre-operative ODI score was 51.4, improved to 18.6 postoperatively. There was no difference in above scores between PLT and TLIF.

CONCLUSION

Our surgical technique used for high grade spondylolisthesis is safe, cost-effective, bone-preserving, reliable, and reproducible for high grade Lumber spondylolisthesis.

A low invasiveness patient’s specific template for spine surgery

Free-hand pedicle screw placement is still conventional in surgery, although it has potentially high risks. The surgical procedures such as pedicle screw placement are usually designed based on medical imaging, but during surgery, the procedures are not normally followed due to the fact that some points are missed in two-dimensional images and seen only during surgery. In this regards, some highly accurate computer-assisted systems have been proposed and are currently used. Moreover, it is possible to reduce or completely avoid hand working by applying modern digital technology. Therefore, using these technologies has remarkable advantages. In this study, we have presented a new approach of pedicle screw placement in the lumbar and sacral regions using a specific drill guide template. The template was created by additive manufacturing technology and was verified in a clinical study as well. The main aim of this research includes the following: design, analyze, manufacture and evaluate the accuracy of a new patient-specific drill guide template, for lumbar pedicle screw placement, and compare the template to the free-hand technique under fluoroscopy supervision. Our results show that the incidence of cortex perforation is substantially reduced compared to existing methods. Finally, we believe that this approach remarkably lowers the incidence of cortex perforation and could be potentially used in clinical applications, particularly in certain selected cases.

Evaluation of Titanium-Coated Pedicle Screws: In Vivo Porcine Lumbar Spine Model

OBJECTIVE

Many studies have addressed the problem of loosening pedicle screws in spinal surgery, which is a serious concern. Titanium coating of medical implants (arthroplasty) is common, but few studies involving in vivo spine models have been reported. We evaluated the radiological, mechanical, and histological characteristics of titanium-coated pedicle screws compared with uncoated or hydroxyapatite-coated pedicle screws.

METHODS

Three different types of pedicle screws, i.e., uncoated, hydroxyapatite-coated, and titanium-coated, were implanted into the lumbar 3-4-5 levels of 9 mature miniature pigs. Radiological evaluation of loosening of pedicle screws was performed. Peak torsional extraction torque was tested in the 42 screws from 7 miniature pigs at 12 weeks postoperatively. The implant-bone interface of the remaining 12 pedicle screws from 2 miniature pigs in each group was assessed by micro-computed tomography and histologic studies.

RESULTS

The incidence of loosening at 12 weeks postoperatively was not significantly different between the titanium-coated pedicle screw group and the other groups. The titanium-coated pedicle screw group exhibited the greatest mean extraction torsional peak torque at 12 weeks postoperatively (P < 0.05). Quantitative micro-computed tomography data were greatest in the titanium-coated pedicle screw group (P < 0.05). Histologic findings showed osteointegration with densely packed new bone formation at the screw coating-bone interface in the titanium-coated pedicle screw group.

CONCLUSIONS

Fixation strength was greatest in the titanium-coated pedicle screw group. Osteointegration at the interface between the titanium-coated implant and bone produced prominent and firm bonding. The titanium-coated pedicle screw is a promising device for application in spinal surgery.

A novel anchoring system for use in a nonfusion scoliosis correction device

BACKGROUND CONTEXT

Insertion of a pedicle screw in the mid- and high thoracic regions has a serious risk of facet joint damage. Because flexible implant systems require intact facet joints, we developed an enhanced fixation that is less destructive to spinal structures. The XSFIX is a posterior fixation system that uses cables that are attached to the transverse processes of a vertebra.

PURPOSE

To determine whether a fixation to the transverse process using the XSFIX is strong enough to withstand the loads applied by the XSLATOR (a novel, highly flexible nonfusion implant system) and thus, whether it is a suitable alternative for pedicle screw fixation.

STUDY DESIGN

The strength of a novel fixation system using transverse process cables was determined and compared with the strength of a similar fixation using polyaxial pedicle screws on different vertebral levels.

METHODS

Each of the 58 vertebrae, isolated from four adult human cadavers, was instrumented with either a pedicle screw anchor (PSA) system or a prototype of the XSFIX. The PSA consisted of two polyaxial pedicle screws and a 5 mm diameter rod. The XSFIX prototype consisted of two bodies that were fixed to the transverse processes, interconnected with a similar rod. Each fixation system was subjected to a lateral or an axial torque.

RESULTS

The PSA demonstrated fixation strength in lateral loading and torsion higher than required for use in the XSLATOR. The XSFIX demonstrated high enough fixation strength (in both lateral loading and torsion), only in the high and midthoracic regions (T10-T12).

CONCLUSIONS

This experiment showed that the fixation strength of XSFIX is sufficient for use with the XSLATOR only in mid- and high thoracic regions. For the low thoracic and lumbar region, the PSA is a more rigid fixation. Because the performance of the new fixation system appears to be favorable in the high and midthoracic regions, a clinical study is the next challenge.

Novel free-hand T1 pedicle screw method: Review of 44 consecutive cases

Summary of Background Data:

Multilevel posterior cervical instrumented fusions are becoming more prevalent in current practice. Biomechanical characteristics of the cervicothoracic junction may necessitate extending the construct to upper thoracic segments. However, fixation in upper thoracic spine can be technically demanding owing to transitional anatomy while suboptimal placement facilitates vascular and neurologic complications. Thoracic instrumentation methods include free-hand, fluoroscopic guidance, and CT-based image guidance. However, fluoroscopy of upper thoracic spine is challenging secondary to vertebral geometry and patient positioning, while image-guided systems present substantial financial commitment and are not readily available at most centers. Additionally, imaging modalities increase radiation exposure to the patient and surgeon while potentially lengthening surgical time.

Materials and Methods:

Retrospective review of 44 consecutive patients undergoing a cervicothoracic fusion by a single surgeon using the novel free-hand T1 pedicle screw technique between June 2009 and November 2012. A starting point medial and cephalad to classic entry as well as new trajectory were utilized. No imaging modalities were employed during screw insertion. Postoperative CT scans were obtained on day 1. Screw accuracy was independently evaluated according to the Heary classification.

Results:

In total, 87 pedicle screws placed were at T1. Grade 1 placement occurred in 72 (82.8%) screws, Grade 2 in 4 (4.6%) screws and Grade 3 in 9 (10.3%) screws. All Grade 2 and 3 breaches were <2 mm except one Grade 3 screw breaching 2-4 mm laterally. Only two screws (2.3%) were noted to be Grade 4, both breaching medially by less than 2 mm. No new neurological deficits or returns to operating room took place postoperatively.

Conclusions:

This modification of the traditional starting point and trajectory at T1 is safe and effective. It attenuates additional bone removal or imaging modalities while maintaining a high rate of successful screw placement compared to historical controls.

Independent assessment of a new pedicle probe and its ability to detect pedicle breach: a cadaveric study

OBJECT

The authors undertook an independent, non-industry funded cadaveric study to evaluate the efficacy of a pedicle-probing device, which uses impedance measurement to warn of impending and actual pedicle screw breach.

METHODS

A previously validated fresh-frozen cadaver model (saline-soaked spine) was used. Individuals at 3 levels of training (attending spine surgeon, orthopedic surgery resident, and medical student) used a cannulated pedicle-probing device to cannulate each of the levels between T-2 and S-1. Each pedicle was cannulated freehand using 2 approaches: 1) a standard trajectory through the middle of the pedicle, and 2) a medial trajectory aimed to breach the medial wall of the pedicle. A 16-slice helical CT scanner was used. The images were interpreted and analyzed by 2 orthopedic spine surgeons and a neuroradiologist.

RESULTS

The sensitivity of the pedicle probe to detect impending breach or breach of 4 mm or less was 90.06%. The sensitivity in detecting medial wall breach was 95.8%. The positive predictive value was 87.1%. The device detected medial breach more often than lateral breach.

CONCLUSIONS

This study showed that this pedicle-probing device could reasonably be used to detect impending breach and actual breach of 4 mm or less. Medial breach was detected better than lateral breach. Use of the pedicle probe may improve patient safety.

The safety of spinal pedicle screws in children ages 1 to 12

BACKGROUND CONTEXT

Pedicle screws have shown to be a safe and effective method of spinal fixation, offering superior multiplanar correction compared with hooks or sublaminar wires in selected situations. Though only food and drug administration (FDA) approved in the adolescent population, they are commonly used in an off-label manner in the preadolescent population.

PURPOSE

To determine if the complication rate of the off-label use of pedicle screws for spinal fixation in the preadolescent 0- to 12-year-old population is comparable with the complication rate in the FDA-approved 13- to 18-year-old population.

STUDY DESIGN/SETTING

Retrospective medical record and radiograph review.

PATIENT SAMPLE

A total of 726 pediatric patients who underwent a spinal fusion procedure at a single tertiary institution between January 2003 and December 2008 were reviewed.

OUTCOME MEASURES

Incidence of instrumentation failure, infection, neurological complication, and total complications.

METHODS

The study population was divided into two groups based on age: the younger group included 0- to 12-year olds and the older group included 13- to 18-year olds at the time of surgery. Groups were further subdivided based on diagnosis: "A," neuromuscular scoliosis; "B," idiopathic scoliosis, and "C," other spinal deformities. Rates of neurovascular complications, infections, and instrumentation complications were compared statistically between the younger and the older groups. Only patients with greater than or equal to 1-year follow-up and greater than or equal to 2-year follow-up were included in the calculations for infection and instrumentation complication rates, respectively.

RESULTS

There were 206 patients (33% males, 67% females) in the younger group (0 to 12 years) and 520 (41% males, 59% females) in the older group (13 to 18 years). Overall, younger group had a 13.6% complication rate compared with 16.9% in the older group. Younger subjects showed a 13.4% complication rate because of instrumentation-related complications, 0.5% for neurovascular complications, and an infection rate of 9.2%. The older group showed a 15.4% complication rate because of instrumentation-related complications, 1.92% for neurovascular complications, and an infection rate of 11.0%. Complication rates were statistically insignificant between the two groups. Other complications in the younger group included one patient with aspiration pneumonia, two with ileus, and one with pulmonary and other complications in the older group included one patient with aspiration pneumonia, two with ileus, three with superior mesenteric artery syndrome, and three with wound dehiscence.

CONCLUSIONS

The complication rates in the young pediatric population associated with the off-label use of pedicle screws for spinal fusions are not statistically different from the complication rates associated with the FDA-approved adolescent population.

A multi-level rapid prototyping drill guide template reduces the perforation risk of pedicle screw placement in the lumbar and sacral spine

INTRODUCTION

The method of free-hand pedicle screw placement is generally safe although it carries potential risks. For this reason, several highly accurate computer-assisted systems were developed and are currently on the market. However, these devices have certain disadvantages. We have developed a method of pedicle screw placement in the lumbar and sacral region using a multi-level drill guide template, created with the rapid prototyping technology and have validated it in a clinical study. The aim of the study was to manufacture and evaluate the accuracy of a multi-level drill guide template for lumbar and first sacral pedicle screw placement and to compare it with the free-hand technique under fluoroscopy supervision.

MATERIALS AND METHODS

In 2011 and 2012, a randomized clinical trial was performed on 20 patients. 54 screws were implanted in the trial group using templates and 54 in the control group using the fluoroscopy-supervised free-hand technique. Furthermore, applicability for the first sacral level was tested. Preoperative CT-scans were taken and templates were designed using the selective laser sintering method. Postoperative evaluation and statistical analysis of pedicle violation, displacement, screw length and deviation were performed for both groups.

RESULTS

The incidence of cortex perforation was significantly reduced in the template group; likewise, the deviation and displacement level of screws in the sagittal plane. In both groups there was no significantly important difference in deviation and displacement level in the transversal plane as not in pedicle screw length. The results for the first sacral level resembled the main investigated group.

CONCLUSIONS

The method significantly lowers the incidence of cortex perforation and is therefore potentially applicable in clinical practice, especially in some selected cases. The applied method, however, carries a potential for errors during manufacturing and practical usage and therefore still requires further improvements.

Learning retention of thoracic pedicle screw placement using a high-resolution augmented reality simulator with haptic feedback

BACKGROUND

We evaluated the use of a part-task simulator with 3D and haptic feedback as a training tool for a common neurosurgical procedure--placement of thoracic pedicle screws.

OBJECTIVE

To evaluate the learning retention of thoracic pedicle screw placement on a high-performance augmented reality and haptic technology workstation.

METHODS

Fifty-one fellows and residents performed thoracic pedicle screw placement on the simulator. The virtual screws were drilled into a virtual patient's thoracic spine derived from a computed tomography data set of a real patient.

RESULTS

With a 12.5% failure rate, a 2-proportion z test yielded P = .08. For performance accuracy, an aggregate Euclidean distance deviation from entry landmark on the pedicle and a similar deviation from the target landmark in the vertebral body yielded P = .04 from a 2-sample t test in which the rejected null hypothesis assumes no improvement in performance accuracy from the practice to the test sessions, and the alternative hypothesis assumes an improvement.

CONCLUSION

The performance accuracy on the simulator was comparable to the accuracy reported in literature on recent retrospective evaluation of such placements. The failure rates indicated a minor drop from practice to test sessions, and also indicated a trend (P = .08) toward learning retention resulting in improvement from practice to test sessions. The performance accuracy showed a 15% mean score improvement and more than a 50% reduction in standard deviation from practice to test. It showed evidence (P = .04) of performance accuracy improvement from practice to test session.

A role for motor and somatosensory evoked potentials during anterior cervical discectomy and fusion for patients without myelopathy: Analysis of 57 consecutive cases

BACKGROUND

Although the usage of combined motor and sensory intraoperative monitoring has been shown to improve the surgical outcome of patients with cervical myelopathy, the role of transcranial electric motor evoked potentials (tceMEP) used in conjunction with somatosensory evoked potentials (SSEP) in patients presenting with radiculopathy but without myelopathy has been less clear.

METHODS

We retrospectively reviewed all patients (n = 57) with radiculopathy but without myelopathy, undergoing anterior cervical decompression and fusion at a single institution over the past 3 years, who had intraoperative monitoring with both tceMEPs and SSEPs.

RESULTS

Fifty-seven (100%) patients presented with radiculopathy, 53 (93.0%) with mechanical neck pain, 35 (61.4%) with motor dysfunction, and 29 (50.9%) with sensory deficits. Intraoperatively, 3 (5.3%) patients experienced decreases in SSEP signal amplitudes and 4 (6.9%) had tceMEP signal changes. There were three instances where a change in neuromonitoring signal required intraoperative alteration of the surgical procedure: these were deemed clinically significant events/true positives. SSEP monitoring showed two false positives and two false negatives, whereas tceMEP monitoring only had one false positive and no false negatives. Thus, tceMEP monitoring exhibited higher sensitivity (33.3% vs. 100%), specificity (95.6% vs. 98.1%), positive predictive value (33.3% vs. 75.0%), negative predictive value (97.7% vs. 100%), and efficiency (91.7% vs. 98.2%) compared to SSEP monitoring alone.

CONCLUSIONS

Here, we present a retrospective series of 57 patients where tceMEP/SSEP monitoring likely prevented irreversible neurologic damage. Though further prospective studies are needed, there may be a role for combined tceMEP/SSEP monitoring for patients undergoing anterior cervical decompression without myelopathy.

Usefulness of a navigation system in surgery for scoliosis: segmental pedicle screw fixation in the treatment

STUDY DESIGN

Postoperative outcomes of segmental pedicle screw fixation were evaluated in posterior scoliosis surgery with the use of navigation system.

OBJECTIVES

We report the usefulness of a navigation system and a segmental pedicle screw fixation in surgery for scoliosis.

SUMMARY OF BACKGROUND DATA

Few reports on a segmental pedicle screw fixation method for scoliosis surgery using a navigation system have been published. This is the report on the usefulness of a navigation system in segmental pedicle screw fixation.

METHODS

We targeted 16 cases in which segmental pedicle screw fixation had been performed using a navigation system at our hospital. We inserted 264 pedicle screws in total, and we did not perform registration for each corpus vertebrate in order to shorten the duration of the surgery. We reviewed screw deviation among the items for review using Neo classification with postoperative CT images (1.25 mm). For screw deviation in this case, grade 2 or higher in the Neo classification system was designated as total deviation. Furthermore, we evaluated the registration period per corpus vertebrae, the complications, duration of surgery, blood loss, Cobb angle, and the correction rate.

RESULTS

In terms of screw deviation, 11 (4.2%) of the 264 inserted screws were classified as total deviation. However, there were no neurovascular complications during or after surgery in any cases, and all cases maintained strong internal fixation. In the relationship between the use or nonuse of registration and the deviation, four screws (3.2%) in the corpus vertebrae for which registration was performed and seven screws (5.0%) in the adjacent corpus vertebrae for which registration was not performed had deviated. The duration of registration per corpus vertebrate averaged 4 min and 24 s (58-791 s), but registration also requires a learning curve, so the duration of registration per corpus vertebrae averaged 1 min and 14 s in more recent cases, thus marking a significant shortening.

CONCLUSION

Segmental pedicle screw fixation are excellent in regard to their fixing and correction force and have been clinically applied even in surgery for scoliosis, but the potential risk of neurovascular complications is unavoidable. The adoption of a navigation system in surgery for scoliosis is useful to increase the safety and certainty of the insertion of pedicle screws.

Pedicle screw surface coatings improve fixation in nonfusion spinal constructs

STUDY DESIGN

Biomechanical and histologic analysis.

OBJECTIVE

To compare the strength of the bone-screw interface of standard uncoated pedicle screws with screws treated with hydroxyapatite (HA), titanium plasma spray (TPS), and a composite HA-TPS coating.

SUMMARY OF BACKGROUND DATA

Transpedicular screw fixation has become the gold standard in the treatment of various thoracolumbar spinal conditions. Pedicle screw loosening, however, has been reported, especially in mechanically demanding constructs or in vertebrae with low bone mineral density.

METHODS

Six mature porcine were instrumented with 4 types of titanium monoaxial pedicle screws (uncoated, HA-only coated, TPS-only coated, and HA-TPS composite coated) in a systematically varied, single-blinded fashion. After a 3-month survival period, the spines were harvested en-bloc and "time zero" control screws were instrumented in adjacent vertebrae. Screw placement and bone mineral density were evaluated with a postharvest computed tomography, and the strength of the tissue-implant interface was evaluated with a torsional screw extraction analysis (60 screws) and a nondecalcified histologic analysis (16 screws).

RESULTS

At 3 months postoperative, peak torque increased for all 3 types of coated screws (increased fixation) and decreased significantly for the uncoated screws (P < 0.001). Although 3-month peak torque was not statistically different between the 3 screw coatings, 4 of 10 TPS-only coated screws had a peak torque that was nearly 0 (<0.1 N m) versus only 1 of 10 HA-only screws and 0 of 10 HA-TPS composite screws. Histologic analysis confirmed the biomechanical findings with improved osseointegration in the HA-only and HA-TPS composite screws.

CONCLUSION

Pedicle screw coatings that promote mechanical interlocking, TPS, or direct osteoblast bonding(HA) increased screw fixation in this nonfusion model. More non-HA coated screws, however, were thought to be "loose" with a nearly zero peak extraction torque and fibrous encapsulation. Increased osseointegration with HA may result in a decreased incidence of screw loosening and improved outcomes of transpedicular spinal instrumentation in nonfusion procedures.

Scoliosis: a straightforward approach to diagnosis and management

Scoliosis should be no more intimidating to manage than acute otitis media. This article reviews how to treat patients with the condition before and after referral to a specialist.

Accuracy and safety of pedicle screw placement in neuromuscular scoliosis with free-hand technique

It is a retrospective analytic study of 1,009 transpedicular screws (689 thoracic and 320 lumbosacral), inserted with free-hand technique in neuromuscular scoliosis using postoperative CT scan. The aim of paper was to determine the accuracy and safety of transpedicular screw placement with free-hand technique in neuromuscular scoliosis and to compare the accuracy at different levels in such population. All studies regarding accuracy and safety of pedicle screw in scoliosis represent idiopathic scoliosis using various techniques such as free-hand, navigation, image intensifier, etc., for screw insertion. Anatomies of vertebrae and pedicle are distorted in scoliosis, hence accurate and safe placement of pedicle screw is prerequisite for surgery. Between 2004 and 2006, 37 consecutive patients, average age 20 years (9-44 years), of neuromuscular scoliosis were operated with posterior pedicle screw fixation using free-hand technique. Accuracy of pedicle screws was studied on postoperative CT scan. Placement up to 2 mm medial side and 4 mm lateral side was considered within-safe zone. Of the 1,009 screws, 273 screws were displaced medially, laterally or on the anterior side showing that 73% screws (68% in thoracic and 82.5% in lumbar spine) were accurately placed within pedicle. Considering the safe zone, 93.3% (942/1009, 92.4% in thoracic and 95.3% in lumbar spine) of the screws were within the safe zone. Comparing accuracy according to severity of curve, accuracy was 75% in group 1 (curve <90 degrees ) and 69% in group 2 (curve >90 degrees) with a safety of 94.8 and 91.2%, respectively (P = 0.35). Comparing the accuracy at different thoracic levels, it showed 67, 64 and 72% accuracy in upper, middle and lower thoracic levels with safety of 96.6, 89.2 and 93.1%, respectively, exhibiting no statistical significant difference (P = 0.17). Pedicle screw placement in neuromuscular scoliosis with free-hand technique is accurate and safe as other conditions.

Accuracy of pedicle and mass screw placement in the spine without using fluoroscopy: a prospective clinical study

BACKGROUND CONTEXT

Spinal instrumentation is accompanied by various problems, including screw malpositioning. One way of preventing this is the employment of intraoperative biplanar fluoroscopy. However, screw malpositioning despite the use of fluoroscopy has been reported, and exposure to radiation is another burden of this method. Therefore, the purpose of this article was to compare the results of instrumentation applications without using scopy versus the harmful effects of radiation exposed during spinal instrumentation.

PURPOSE

The aim of this article was to review the literature and this is the first prospective clinical study performed on this subject.

STUDY DESIGN

Patient report.

PATIENT SAMPLE

One hundred thirty-two patients with spinal instrumentations were included.

OUTCOME MEASURES

Radiological investigation with computed tomography (CT) scans was performed 2 days after the procedure.

METHODS

Craniosacral posterior spinal instrumentation was performed without using scopy at the Neurosurgery Clinic of Haseki Training and Research Hospital between January 2000 and January 2005. Postoperative CT analyses were performed to evaluate whether the 527 screws used during posterior instrumentation in a total of 132 patients were positioned correctly. In all cases, the screw applications were performed with regard to anatomic landmarks, whereas the distances were determined according to lesion localizations. Screw malpositioning and the functional effects and relations with interactions with neurovascular structures were examined. At the end of the operations, all patients were examined with direct lateral roentgenograms and CT scans for the evaluation of screw positions.

RESULTS

According to their locations, 75 cervical screwing in 24 patients, 32 upper thoracic screwing in 7 patients, 30 midthoracic screwing in 7 patients, 306 thoracolumbar screwing in 54 patients, and 84 sacral screwing in 40 patients were performed by the senior spinal surgeon (KK). Among all posterior spinal instrumentation applications, the cervical region analyses revealed penetration of the medial wall of vertebral foramen with two (0.4%) screws, penetration of the lateral wall with one (0.2%) screw, and protrusion into the vertebral foramen without vascular penetration with one (0.2%) screw, whereas in the upper thoracic region there was penetration into the lateral pedicle wall with one (0.2%) screw and deviation toward the disc space through the superior end plate with two (0.4%) screws. In the midthoracic region, there was penetration into the disc space with two (0.4%) screws in only one case, whereas in the thoracolumbar complex, there was deviation toward the superior end plate with seven (1.4%) screws in four cases, deviation toward the disc space with two (0.4%) screws, medial wall penetration with six (1.2%) screws (two of which caused nerve root irritation in three cases), and penetration of the lateral wall of pedicle with four (0.8%) screws. In the sacral instrumentations, malpositioning occurred with only two (0.4%) screws because of deviation toward the medial wall. In summary, malpositioning occurred with 30 (5.6%) of the total 527 screws; none of the cases had neural or vascular damage. Two (1.5%) cases were revised for malpositioning and distance errors. The mean duration for preparation of screw introduction site and placement of the screw was 3 minutes. Infection occurred in only one (0.75%) case.

CONCLUSIONS

Screw application without fluoroscopy is performed with calculation of all essential anatomic details, and because of the reduction of surgery time, the absence of exposure to radiation, and very low infection rates as a consequence of reduced surgery time, it is a method recommendable for surgeons experienced with screw placement. Besides, its malpositioning rates are within acceptable limits. Because screw malpositioning is also found after biplanar fluoroscopy, the prevention of screw malpositioning requires knowing the anatomic landmarks accurately.

Accuracy of thoracic pedicle screw placement in scoliosis using the ideal pedicle entry point during the freehand technique

Previously, we described the ideal pedicle entry point (IPEP) for the thoracic spine at the base of the superior facet at the junction of the lateral one third and medial two thirds with the freehand technique on cadavers. Here we measured the accuracy of thoracic pedicle screw placement (Chung et al. Int Orthop 2008) on post-operative computed tomography (CT) scans in 43 scoliosis patients who underwent operation with the freehand technique taking the same entry point. Of the 854 inserted screws, 268 (31.3%) were displaced; 88 (10.3%) and 180 (21.0%) screws were displaced medially and laterally, respectively. With regard to the safe zone, 795 screws were within the safe zone representing an accuracy rate of 93%; 448 and 406 thoracic screws inserted in adolescent idiopathic and neuromuscular scoliosis showed an accuracy of 89.9 and 94%, respectively (p = 0.6475). The accuracy rate of screws inserted in the upper, middle and lower thoracic pedicles were 94.2, 91.6 and 93.7%, respectively (p = 0.2411). The results indicate that IPEP should be considered by surgeons during thoracic pedicle screw instrumentation.