Use of intraoperative isocentric C-arm 3D fluoroscopy for sextant percutaneous pedicle screw placement: case report and review of the literature

Image-Guided Navigation in Spine Surgery: From Historical Developments to Future Perspectives

Intraoperative navigation is critical during spine surgery to ensure accurate instrumentation placement. From the early era of fluoroscopy to the current advancement in robotics, spinal navigation has continued to evolve. By understanding the variations in system protocols and their respective usage in the operating room, the surgeon can use and maximize the potential of various image guidance options more effectively. At the same time, maintaining navigation accuracy throughout the procedure is of the utmost importance, which can be confirmed intraoperatively by using an internal fiducial marker, as demonstrated herein. This technology can reduce the need for revision surgeries, minimize postoperative complications, and enhance the overall efficiency of operating rooms.

High Accuracy and Safety of Intraoperative CT-Guided Navigation for Transpedicular Screw Placement in Revision Spinal Surgery

Background: Intraoperative CT-guided navigation (iCT-navigation) has been reported to improve the accuracy and safety of transpedicular screw placement in primary spinal surgery. However, due to a disrupted bony anatomy and scarring tissue, revision spinal surgery can be challenging. The purpose of this study was to evaluate the accuracy and safety of iCT-navigation for screw placement at the virgin site versus the revision site in revision thoracolumbar spinal surgery. Method: In total, 254 screws were inserted in 27 revision surgeries, in which 114 (44.9%) screws were inserted at the site with previous laminectomy or posterolateral fusion (the revision site), 64 (25.2%) were inserted at the virgin site, and 76 (29.9%) were inserted to replace the pre-existing screws. CT scans were conducted for each patient after all screws were inserted to intraoperatively confirm the screw accuracy. Results: In total, 248 (97.6%) screws were considered accepted. The rate of accepted screws at the virgin site was 98.4% (63/64) versus 95.6% (109/114) at the revision site (p: 0.422). There were six (2.4%) unaccepted screws, which were immediately revised during the same operation. There was no neurological injury noted in our patients. Conclusion: With the use of iCT-navigation, the rate of accepted screws at the revision site was found to be comparable to that at the virgin site. We concluded that iCT-navigation could achieve high accuracy and safety for transpedicular screw placement in revision spinal surgery and allow for the immediate revision of unaccepted screws.

Metal artifacts in intraoperative O-arm CBCT scans

Background

Cone-beam computed tomography (CBCT) has become an increasingly important medical imaging modality in orthopedic operating rooms. Metal implants and related image artifacts create challenges for image quality optimization in CBCT. The purpose of this study was to develop a robust and quantitative method for the comprehensive determination of metal artifacts in novel CBCT applications.

Methods

The image quality of an O-arm CBCT device was assessed with an anthropomorphic pelvis phantom in the presence of metal implants. Three different kilovoltage and two different exposure settings were used to scan the phantom both with and without the presence of metal rods.

Results

The amount of metal artifact was related to the applied CBCT imaging protocol parameters. The size of the artifact was moderate with all imaging settings. The highest applied kilovoltage and exposure level distinctly increased artifact severity.

Conclusions

The developed method offers a practical and robust way to quantify metal artifacts in CBCT. Changes in imaging parameters may have nonlinear effects on image quality which are not anticipated based on physics.

Is bony attachment necessary for dynamic reference frame in navigation-assisted minimally invasive lumbar spine fusion surgery?

This study aimed to compare the accuracy of navigation-assisted percutaneous pedicle screw insertions between traditional posterior superior iliac spine (PSIS) fixed and cutaneously fixed dynamic reference frame (DRF) in minimally invasive surgery of transforaminal lumbar interbody fusion (MIS TLIF). This is a prospective randomized clinical study. Between May 2016 and Nov 2017, 100 patients who underwent MIS TLIF were randomly divided into bone fixed group (with PSIS fixed DRF) and skin fixed group (with cutaneously fixed DRF). The pedicel screws were inserted under navigational guidance using computed tomography (CT) data acquired intraoperatively with a Ziehm 3-dimensional fluoroscopy-based navigation system. Screw positions were immediately checked by a final intraoperative scan. The accuracy of screw placement was evaluated by a sophisticated computed tomography protocol. Both groups had similar patient demographics. Totally Five-hundred Twelve pedicle screws were placed in the lumbar spine. There were 2 moderate (2-4 mm) pedicle perforations in each group. The accuracy showed no significant difference between bone fixed and skin fixed DRF. There were no significant procedure-related complications. The skin fixed DRF provides similar accuracy in pedicle screw insertions with bone fixed DRF using intraoperative 3D image guided navigation in MIS TLIF. Skin fixed DRF not only serves as an alternative method but also saves a separate incision wound for bony attachment.

Evaluation of a Three-Dimensional Printed Guide and a Polyoxymethylene Thermoplastic Regulator for Percutaneous Pedicle Screw Fixation in Patients with Thoracolumbar Fracture

BACKGROUND This study aimed to evaluate the efficacy of a porous polyoxymethylene thermoplastic regulator combined with a three-dimensional (3D) printed template to guide pedicle needle insertion in patients undergoing percutaneous pedicle screw fixation (PPSF) for thoracolumbar fracture. MATERIAL AND METHODS Forty patients were randomly divided into group A, treated using a porous polyoxymethylene thermoplastic regulator combined with a 3D printed template, and group B, who underwent conventional PPSF. Data recorded included the number of pedicle screws successfully inserted on the first attempt, the number of attempts, the time to successful needle insertion, the total time of fluoroscopy, and the duration of surgery. The Visual Analogue Scale (VAS) and the Oswestry Disability Index (ODI) scores one day before surgery, and at day 1, day 7, month 1, and month 3 after surgery were recorded. The postoperative vertebral posterior kyphotic angle (KA) and the rate of change of KA were recorded. RESULTS Group A had a significantly increased total number of successful first insertions compared with group BV (P<0.05). Postoperative VAS and ODI scores of patients in both groups were significantly lower than before surgery (P<0.05), with no significant difference between the two groups at postoperative month 1 and month 3 (P>0.05). The postoperative vertebral posterior KA decreased significantly in both groups after surgery, with no significant difference between the two groups (P>0.05). CONCLUSIONS The use of a porous polyoxymethylene thermoplastic regulator combined with a 3D printed template may improve the success of pedicle insertion in patients undergoing PPSF.

The evolution of surgical management for vertebral column tumors

In BriefThere has been a significant shift in treatment paradigms for both primary and metastatic spine tumors over the last several decades. This article highlights some of the more important treatment advances that practitioners should be made aware of. It is important to not only incorporate these changes into individual practice but also appreciate the treatment trends that herald a significantly different future for spine tumor treatment.

Percutaneous screw placement in the lumbar spine with a modified guidance technique based on 3D CT navigation system

Several guidance techniques have been employed to increase accuracy and reduce surgical time during percutaneous placement of pedicle screws (PS). The purpose of our study was to present a modified technique for percutaneous placement of lumbar PS that reduces surgical time. We reviewed 23 cases of percutaneous PS placement using our technique for minimally invasive lumbar surgeries and 24 control cases where lumbar PS placement was done via common technique using Jamshidi needles (Becton, Dickinson and Company, Franklin Lakes, NJ, USA). An integrated computer-guided navigation system was used in all cases. In the technique modification, a handheld drill with a navigated guide was used to create the path for inserting guidewires through the pedicles and into the vertebral bodies. After drill removal, placement of the guidewires through the pedicles took place. The PS were implanted over the guidewires, through the pedicles and into the vertebral bodies. Intraoperative computed tomography was performed after screw placement to ensure optimal positioning in all cases. There were no intraoperative complications with either technique. PS placement was correct in all cases. The average time for each PS placement was 6.9 minutes for the modified technique and 9.2 minutes for the common technique. There was no significant difference in blood loss. In conclusion, this modified technique is efficient and contributes to reduced operative time.

Accuracy of pedicle screw placement in patients with Marfan syndrome

BACKGROUND

There is no study concerning safety and accuracy of pedicle screw placement in Marfan syndrome. The objective of this study is to investigate accuracy and safety of pedicle screw placement in scoliosis associated with Marfan syndrome.

METHODS

CT scanning was performed to analyze accuracy of pedicle screw placement. Pedicle perforations were classified as medial, lateral or anterior and categorized to four grades: ≤ 2 mm as Grade 1, 2.1-4.0 mm as Grade 2, 4.1-6.0 mm as Grade 3, ≥6.1 mm as Grade 4. Fully contained screws or with medial wall perforation ≤ 2 mm or with lateral wall perforation ≤ 6 mm and without injury of visceral organs were considered acceptable, otherwise were unacceptable.

RESULTS

976 pedicle screws were placed, 713 screws (73.1%) were fully contained within the cortical boundaries of the pedicle. 924 (94.7%) screws were considered as acceptable, and 52 (5.3%) as unacceptable. The perforation rate was higher using free-hand technique than O-arm navigation technique (30.8% VS. 11.4%, P < 0.05), higher in lumbar region than in thoracic region (34.1% VS. 22.3%, P < 0.05) and higher in concave side than in convex side (33.5% VS. 21.9%, P < 0.05). No injury of visceral organs especially aorta erosion was noted in the series. 7 cases of dural tear caused by misplaced screws occurred, and 4 cases developed cerebro-spinal fluid leak. Drainage and pressure dressings were applied for these patients, and no infection was observed. Leg pain was observed in 7 cases, and 2 cases simultaneously complained of leg weakness. Revision surgery was conducted to remove the misplaced screws for these 2 patients. Conservative treatment was applied for the 5 patients without leg weakness. Symptoms of leg weakness and pain resolved in all patients.

CONCLUSION

Placement of pedicle screw in Marfan syndrome is accuracy and safe. O-arm navigation was an effective modality to ensure the safety and accuracy of screw placement. Special attention should be paid when screws were placed at the lumber spine and the concave side of spine deformity to avoid the higher rate of complications.

Percutaneous Transpedicular Fixation: Technical tips and Pitfalls of Sextant and Pathfinder Systems

Study Design

The efficacy of the operative techniques, possible benefits as well as pitfalls and limitations of the techniques are discussed. Potential drawbacks are also detected.

Purpose

This study aims to report indications, techniques, and our experience with the use of the Sextant and PathFinder percutaneous transpedicular screw fixation systems.

Overview of Literature

Percutaneous pedicle screw insertion is a novel technique. Successful percutaneous placement of pedicle screws requires surgical skill and experience because of lack of anatomic surface landmarks. Fluoroscopy-guided percutaneous placement of pedicle screws is effective. Many systems are now available.

Methods

We conducted a prospective operative and postoperative analysis of 40 patients with absolute indication for thoracic or lumbar instability between January 2009 and June 2013. All procedures were performed with the Sextant (group A) and PathFinder (group B) systems under fluoroscopic guidance. Operative techniques are discussed and the results compared.

Results

Percutaneous transpedicular screw fixation minimizes the morbidity associated with open techniques without compromising the quality of fixation. A total of 190 screws were inserted. There was no additional morbidity. Postoperative computed tomography images and plain X-rays were analyzed. Reduction of visual analog scale scores of back pain was evident.

Conclusions

Fluoroscopy-guided percutaneous pedicular screws are feasible and can be safely done. Current systems allow multi-segmental fixation with significantly less difficulties. The described techniques have acceptable intra- and postoperative complication rates, and overall sufficient pain control with early mobilization of patients.

Novel method for setting up 3D navigation system with skin-fixed dynamic reference frame in anterior cervical surgery

PURPOSE

To introduce easy and useful methods using 3D navigation system with skin-fixed dynamic reference frame (DRF) in anterior cervical surgery and to validate its accuracy.

METHODS

From September 2012 to May 2013, 31 patients underwent anterior cervical surgery and a total of 48 caspar distraction pins were inserted into each cervical vertebra. Every operation was performed using O-arm® navigation system with skin-fixed DRF. To validate the accuracy of these methods, a custom-made metal sleeve was used. In surgical field, through the metal sleeve, the tip of a navigation probe promptly contacts to the tip of caspar pin. We measured the vertical and horizontal distances and the angular deviation in sagittal plane between the caspar pin and the navigation probe on the virtual images and evaluated accuracy of navigation system with skin fixed DRF.

RESULTS

Total 31 (males 20, females 11) patients and 48 caspar pins were included in this study. The mean horizontal distance between the caspar pin and the navigation probe displayed in navigation monitor was 0.49 ± 0.71 mm. The mean vertical distance between the caspar pin and the navigation probe displayed in navigation monitor was 0.88 ± 0.93 mm. And the mean angular deviation in sagittal plane between the caspar pin and the navigation probe displayed in navigation monitor was 0.59 ± 0.55°.

CONCLUSIONS

3D navigation system with skin-fixed DRF in anterior cervical surgery is a simple and reliable method and it can be a helpful supplement to a spine surgeon's judgement.

A New Electromagnetic Navigation System for Pedicle Screws Placement: A Human Cadaver Study at the Lumbar Spine

Introduction

Technical developments for improving the safety and accuracy of pedicle screw placement play an increasingly important role in spine surgery. In addition to the standard techniques of free-hand placement and fluoroscopic navigation, the rate of complications is reduced by 3D fluoroscopy, cone-beam CT, intraoperative CT/MRI, and various other navigation techniques. Another important aspect that should be emphasized is the reduction of intraoperative radiation exposure for personnel and patient.

The aim of this study was to investigate the accuracy of a new navigation system for the spine based on an electromagnetic field.

Material and Method

Twenty pedicle screws were placed in the lumbar spine of human cadavers using EMF navigation. Navigation was based on data from a preoperative thin-slice CT scan. The cadavers were positioned on a special field generator and the system was matched using a patient tracker on the spinous process. Navigation was conducted using especially developed instruments that can be tracked in the electromagnetic field. Another thin-slice CT scan was made postoperatively to assess the result. The evaluation included the position of the screws in the direction of trajectory and any injury to the surrounding cortical bone. The results were classified in 5 groups: grade 1: ideal screw position in the center of the pedicle with no cortical bone injury; grade 2: acceptable screw position, cortical bone injury with cortical penetration ≤ 2 mm; grade 3: cortical bone injury with cortical penetration 2,1-4 mm, grad 4: cortical bone injury with cortical penetration 4,1-6 mm, grade 5: cortical bone injury with cortical penetration >6 mm.

Results

The initial evaluation of the system showed good accuracy for the lumbar spine (65% grade 1, 20% grade 2, 15% grade 3, 0% grade 4, 0% grade 5). A comparison of the initial results with other navigation techniques in literature (CT navigation, 2D fluoroscopic navigation) shows that the accuracy of this system is comparable.

Conclusion

EMF navigation offers a high accuracy in Pedicle screw placement with additional advantages compared to other techniques. The short set-up time and easy handling of EMF navigation should be emphasized. Additional advantages are the absence of intraoperative radiation exposure for the operator and surgical team in the current set-up and the operator’s free mobility without interfering with navigation. Further studies with navigation at higher levels of the spine, larger numbers of cases and studies with control group are planned.

Determination of detection depth of optical probe in pedicle screw measurement device

BACKGROUND

There is a high probability of accidental perforation of the vertebral pedicle wall in pedicle screw insertion surgery. A pedicle screw (PS) measurement device with an optical probe has been reported to send out a warning signal before the PS tip breaking the vertebral pedicle wall.

METHODS

In this study, we explored the detection depth of optical probe in this measurement device, which was closely related to the effective alarm distance. In the boundary, the vertebrae tissues could be treated as 2-layer models including spongy bones and compact bones. The Monte Carlo simulation and phantom models were performed to analyse and define the detection depth. Then the porcine vertebrae models were performed to obtain optical spectrum and reduced scattering coefficient, based on which the detection depths were deduced. Moreover, a comparison was made to explore the most significant pattern factor from the experiment results.

RESULTS

According to the pattern factor, an alarm threshold was successfully deduced to define the alarm distance during pedicle screw monitoring.

CONCLUSIONS

Thus, the proposed alarm standard based on detection depth provides a potential for guiding pedicle screw in surgery.

Percutaneous pedicle screw placement in the thoracic spine: A cadaveric study

STUDY DESIGN

A cadaveric study to determine the accuracy of percutaneous screw placement in the thoracic spine using standard fluoroscopic guidance.

SUMMARY OF BACKGROUND DATA

While use of percutaneous pedicle screws in the lumbar spine has increased rapidly, its acceptance in the thoracic spine has been slower. As indications for pedicle screw fixation increase in the thoracic spine so will the need to perform accurate and safe placement of percutaneous screws with or without image navigation. To date, no study has determined the accuracy of percutaneous thoracic pedicle screw placement without use of stereotactic imaging guidance.

MATERIALS AND METHODS

Eighty-six thoracic pedicle screw placements were performed in four cadaveric thoracic spines from T1 to T12. At each level, Ferguson anterior-posterior fluoroscopy was used to localize the pedicle and define the entry point. Screw placement was attempted unless the borders of the pedicle could not be delineated solely using intraoperative fluoroscopic guidance. The cadavers were assessed using pre- and postprocedural computed tomography (CT) scans as well as dissected and visually inspected in order to determine the medial breach rate.

RESULTS

Ninety pedicles were attempted and 86 screws were placed. CT analysis of screw placement accuracy revealed that only one screw (1.2%) breached the medial aspect of the pedicle by more than 2 mm. A total of four screws (4.7%) were found to have breached medially by visual inspection (three Grade 1 and one Grade 2). One (1.2%) lateral breach was greater than 2 mm and no screw violated the neural foramen. The correlation coefficient of pedicle screw violations and pedicle diameter was found to be 0.96.

CONCLUSIONS

This cadaveric study shows that percutaneous pedicle screw placement can be performed in the thoracic spine without a significant increase in the pedicle breach rate as compared with standard open techniques. A small percentage (4.4%) of pedicles, especially high in the thoracic spine, may not be safely visualized.

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

OBJECT

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.

METHODS

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.

RESULTS

On postprocedure scanning, only 1 screw had a minor lateral and superior breach that was asymptomatic. To date, there have been no hardware failures.

CONCLUSIONS

Percutaneous pedicle screws can be placed effectively and safely without the use of K-wires.

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

OBJECT

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Percutaneous fixation of thoracolumbar fractures: current concepts

Numerous improvements in minimally invasive spine surgery (MISS) have been made during the last decade. MISS in thoracolumbar spine trauma management must achieve the same results as conventional treatment but with less morbidity. The increased use of MISS technologies in spine trauma has been correlated to the availability of more versatile instrumentation, which makes the fixation of all thoracic and lumbar levels possible. Balloon-assisted techniques have been used to support the anterior column in a stand-alone manner or in combination with open or percutaneous pedicle screw fixation. Fluoroscopy-assisted pedicle screw insertion is associated with less pedicle wall violation when compared to open surgery, but with increased radiation exposure for the surgeon and patient. Surgeons must be aware of this issue and new technologies are available to decrease irradiation. The advantages of percutaneous pedicle screw fixation relative to open surgery are discussed: preservation of posterior musculature, less blood loss, shorter operative time, lower infection risk, less postoperative pain, shorter rehabilitation time as well as shorter hospital stay. Limitations of percutaneous fixation include the inability to achieve direct spinal canal decompression and not having the option to perform a fusion. Nevertheless, these limitations can be addressed by combining MISS with open techniques. Indications for percutaneous spine fixation alone or in combination with MISS or open techniques are discussed based on the AO classification. The benefits of percutaneous spinal fixation for unstable spine fractures in polytrauma patients are also discussed. Posterior instrumentation can be easily removed after bone union to allow young patients to regain their mobility. Large well-controlled prospective studies are needed to draw up guidelines for less invasive procedures in spine trauma. In the future, development of new technologies can expand the scope of indications and treatment possibilities using MISS techniques in spine trauma.

Application of intraoperative computed tomography with or without navigation system in surgical correction of spinal deformity: a preliminary result of 59 consecutive human cases

STUDY DESIGN

A retrospective analysis of patients undergoing spinal deformity correction surgery by the assistance of intraoperative computed tomography (iCT) with or without navigation system.

OBJECTIVE

To share our preliminary experience and analysis of the iCT navigation system applied to spinal deformity surgery.

SUMMARY OF BACKGROUND DATA

The iCT navigation system has been shown to improve accuracy and safety in posterior instrumentation. It not only decreased the operation time but also prevented excessive radiation exposure to the medical staff. To date, there are only few reports about the application of the iCT navigation system in spinal deformity surgery.

METHODS

From April 2009 to September 2010, 59 patients who had a diagnosis of scoliosis, kyphosis, or scoliokyphosis and underwent iCT-assisted surgical correction were included. Without randomization, 28 patients were operated with the iCT-navigation system, and the other 31 patients were operated with standard procedure under iCT assistance. The detailed procedures, preoperative and intraoperative images were illustrated. The accuracy of screw placement, time for screw insertion, postoperative correction rate, and iCT scanning data were analyzed.

RESULTS

There were significant differences between 2 groups in (1) the preoperative Cobb angle (76.2° and 62.6° in the navigation and non-navigation groups), (2) the accuracy and the revision rate of thoracic pedicle screws and total pedicle screws, and (3) the average screw insertion time. The breach rate and the revision rate of thoracic pedicle screws and total pedicle screws were significantly lower and the average screw insertion time was significantly lesser in the navigation group than in the non-navigation group. There were no statistically significant difference in (1) the breach rate and the revision rate of lumbar pedicle screws, (2) the mean iCT scanning time and time-out, (3) the mean number of fusion segments, (4) the mean number of iCT scans, and (5) the postoperative correction rate. Complications were encountered in 2 patients in the non-navigation group but none in the navigation group. There was no reoperation due to implant malposition in both groups.

CONCLUSION

The iCT navigation system provides desirable accuracy of posterior spinal instrumentation for patients during surgical correction of spinal deformity without radiation exposure to the medical staff, especially in thoracic spine instrumentation. Meanwhile, the iCT in itself is an effective means of assessing complex instrumentation of the spinal deformity.

Evaluation of percutaneous surgery in the treatment of thoracolumbar fractures. Preliminary results of a prospective study on 65 patients

INTRODUCTION

We conducted a prospective, single-center, continuous study of patients operated for fractures urelated to osteoporosis at the thoracolumbar junction level using percutaneous techniques. The aim of this study was to investigate the clinical and radiological outcomes of percutaneous techniques for these indications.

PATIENTS AND METHODS

This study included patients who underwent standalone balloon kyphoplasty surgery or combined with percutaneous posterior osteosynthesis in cases of associated distraction. The fractures were classified according to the Magerl classification. The patients were evaluated clinically (visual analog scale [VAS], the Oswestry Disability Index, and autonomy) and radiologically (vertebral kyphosis and height variations of the vertebral body) for 12 months.

RESULTS

Sixty-five patients were included. The mean age at the time of the surgery was 45.4 years (range, 19-72 years). The main indications were A.1 fractures of L1. We noted 22% cement leakages, none having a clinical impact. In the overall series, the VAS at the lesional level improved from 5.5 (range, 3-8) preoperatively to 0.6 (range, 1-3) at 12 months. In all, 95% of the workers resumed their occupation. Traumatic kyphosis improved from 13.3° (range, 5-23°) before the surgery to 8.3° (range, 1-20°).

DISCUSSION

The complication rate was low. The radiological results are comparable to those reported in the literature for other series with percutaneous surgery. Only the loss of the correction observed in the group undergoing standalone kyphoplasty with calcium phosphate cement led us to propose another type of treatment for these indications. This study must be continued over the long term to detect the appearance of discopathy related to cement leakage and to answer questions as to how cement evolves.

LEVEL OF EVIDENCE

III, prospective study with low statistical power.

Volume slicing of cone-beam computed tomography images for navigation of percutaneous scaphoid fixation

PURPOSE

Percutaneous scaphoid fixation (PSF) is growing in popularity as a treatment option for non-displaced fractures. Success of this procedure demands high-precision screw placement, which can be difficult to achieve with standard 2D imaging. This study aimed to develop and test a system for computer-assisted navigation using volume slicing of 3D cone-beam computed tomography (CBCT).

METHODS

The navigated technique involved a distinctive workflow in which a 3D CBCT imager was calibrated preoperatively, circumventing the need for intraoperative patient-based registration. Intraoperatively, a 3D CBCT image was acquired for both preoperative planning and direct navigation using volume-rendered slices. An in vitro study was conducted to compare the navigated approach to two conventional fluoroscopic methods for volar PSF. The surgical goal was to insert a guide wire to maximize both length and central placement.

RESULTS

There was no significant difference in the mean central placement of guide wire, although the variance in central placement was significantly lower using VS navigation (P < 0.01). The lengths of the drill paths were significantly longer for the VS-navigated group compared with one 2D group (P < 0.1). Each navigated trial required only one drilling attempt and resulted in less radiation exposure than conventional C-arm (P < 0.01).

CONCLUSIONS

Volume-sliced navigation achieved a more repeatable and reliable central pin placement, with fewer drilling attempts than conventional 2D techniques. Volume-sliced navigation had a higher number of drill paths within the optimal zone maximizing both length of the path and depth from the surface.

Minimally invasive percutaneous transpedicular screw fixation: increased accuracy and reduced radiation exposure by means of a novel electromagnetic navigation system

Background

Minimally invasive percutaneous pedicle screw instrumentation methods may increase the need for intraoperative fluoroscopy, resulting in excessive radiation exposure for the patient, surgeon, and support staff. Electromagnetic field (EMF)-based navigation may aid more accurate placement of percutaneous pedicle screws while reducing fluoroscopic exposure. We compared the accuracy, time of insertion, and radiation exposure of EMF with traditional fluoroscopic percutaneous pedicle screw placement.

Methods

Minimally invasive pedicle screw placement in T8 to S1 pedicles of eight fresh-frozen human cadaveric torsos was guided with EMF or standard fluoroscopy. Set-up, insertion, and fluoroscopic times and radiation exposure and accuracy (measured with post-procedural computed tomography) were analyzed in each group.

Results

Sixty-two pedicle screws were placed under fluoroscopic guidance and 60 under EMF guidance. Ideal trajectories were achieved more frequently with EMF over all segments (62.7% vs. 40%; p = 0.01). Greatest EMF accuracy was achieved in the lumbar spine, with significant improvements in both ideal trajectory and reduction of pedicle breaches over fluoroscopically guided placement (64.9% vs. 40%, p = 0.03, and 16.2% vs. 42.5%, p = 0.01, respectively). Fluoroscopy time was reduced 77% with the use of EMF (22 s vs. 5 s per level; p < 0.0001) over all spinal segments. Radiation exposure at the hand and body was reduced 60% (p = 0.058) and 32% (p = 0.073), respectively. Time for insertion did not vary between the two techniques.

Conclusions

Minimally invasive pedicle screw placement with the aid of EMF image guidance reduces fluoroscopy time and increases placement accuracy when compared with traditional fluoroscopic guidance while adding no additional time to the procedure.

Clinical accuracy of computer-assisted two-dimensional fluoroscopy for the percutaneous placement of lumbosacral pedicle screws

STUDY DESIGN

Clinical case series.

OBJECTIVE

The primary objective of this study was to evaluate the clinical accuracy of computer-assisted two-dimensional fluoroscopy (2D-CAS) for the percutaneous placement of lumbosacral pedicle screws.

SUMMARY OF BACKGROUND DATA

Loss of visual anatomic landmarks and reduced tactile feedback increases the risk of pedicle screw misplacement by when using minimally invasive (MIS) percutaneous techniques. However, objective data on screw misplacement in this scenario is lacking.

METHODS

A MIS-2D-CAS technique (FluoroNav) was used for the placement of pedicle screws in 41 consecutive patients undergoing MIS-interbody instrumented fusion. Postoperative computerized tomography (CT) was obtained in all patients at 6 months after surgery and was evaluated by 3 observers. 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), breach direction, vertebral body perforation and screw trajectory. Interobserver reliability of CT grading was assessed with kappa statistics.

RESULTS

A total of 161 screws were placed. No neurologic, vascular, or visceral injuries occurred. About 37 (23%) screws breached the pedicle. The majority (83.8%, 31/37) of breaches were graded II. There were 5 Grade III and 1 Grade IV breaches. Medial versus lateral breaches occurred in 30% (11/37) and 60% (22/37), respectively; 10% (4/37) of the breaches were superior. Overall, 8 (5%) vertebral body breaches occurred. Of the pedicle screws, 19 (12%) had trajectories that deviated from acceptable, with the majority being medial (16/19, 84%). Fluoroscopy time for screw placement was typically less than 20 seconds total per case. There was 1 clinically significant breach at L5 (III, medial) which resulted in a L5 radiculopathy. Kappa statistics showed excellent overall agreement between reviewers (k = 0.73-0.92; 90%-96% agreement).

CONCLUSION

The two-dimensional (2D) virtual fluoroscopy is a clinically acceptable option for percutaneous placement of pedicle screws. However, this technique requires cautious application and is particularly vulnerable to axial trajectory errors.

Comparison of the percutaneous screw placement precision of isocentric C-arm 3-dimensional fluoroscopy-navigated pedicle screw implantation and conventional fluoroscopy method with minimally invasive surgery

STUDY DESIGN

Retrospective clinical study to compare the percutaneous screw placement precision of isocentric C-arm (Iso-C) 3-dimensional fluoroscopy-navigated pedicle screw implantation and conventional fluoroscopy.

OBJECTIVE

The purpose of this study was to evaluate the accuracy of clinical percutaneous pedicle screw placement (PPSP) using Iso-C 3-dimensional fluoroscopy navigation.

SUMMARY OF BACKGROUND DATA

The technique of PPSP recently has been applied to internal fixation for segmental lumbar instability as a form of minimally invasive spine surgery. The percutaneous insertion technique requires surgical skill and experience. The 3-dimensional fluoroscopy-based image-guidance navigation system has been proven to be effective in guiding accurate PPSP in the lumbar area of cadavers. However, there have been few clinical reports comparing the accuracy of Iso-C 3-dimensional fluoroscopy-navigated pedicle screw implantation and the conventional fluoroscopy method.

METHODS

Here, 300 percutaneous pedicle screws were evaluated; half of them were inserted under Iso-C 3-dimensional navigation and the others under fluoroscopy. The accuracy of pedicle screw placement was examined postoperatively using an axial 2-mm slice computed tomography. Screw malpositioning was classified either as exposed screw (<50% of the screw outside the pedicle) or perforated pedicle (>50% of the screw outside the pedicle boundaries).

RESULTS

Of the 150 pedicle screws placed with Iso-C 3-dimensional fluoroscopy-based image-guide assistance, 11 (7.3%) were classified as exposed screws and 0 (0%) as perforated pedicle. Of the 150 pedicle screws inserted under fluoroscopy, 18 (12%) were classified as exposed screw and 5 (3.3%) as perforated pedicle. The difference in frequency of screw misplacement between the procedure using Iso-C 3-dimensional fluoroscopy-based image-guide assistance and that using fluoroscopy was statistically significant (P<0.05; chi test).

CONCLUSIONS

This study demonstrates the feasibility of placing percutaneous posterior lumbar pedicle screws with the assistance of Iso-C 3-dimensional navigation.

Image-guided spine surgery: state of the art and future directions

Navigation technology is a widely available tool in spine surgery and has become a part of clinical routine in many centers. The issue of where and when navigation technology should be used is still an issue of debate. It is the aim of this study to give an overview on the current knowledge concerning the technical capabilities of image-guided approaches and to discuss possible future directions of research and implementation of this technique. Based on a Medline search total of 1,462 publications published until October 2008 were retrieved. The abstracts were scanned manually for relevance to the topics of navigated spine surgery in the cervical spine, the thoracic spine, the lumbar spine, as well as ventral spine surgery, radiation exposure, tumor surgery and cost-effectivity in navigated spine surgery. Papers not contributing to these subjects were deleted resulting in 276 papers that were included in the analysis. Image-guided approaches have been investigated and partially implemented into clinical routine in virtually any field of spine surgery. However, the data available is mostly limited to small clinical series, case reports or retrospective studies. Only two RCTs and one metaanalysis have been retrieved. Concerning the most popular application of image-guided approaches, pedicle screw insertion, the evidence of clinical benefit in the most critical areas, e.g. the thoracic spine, is still lacking. In many other areas of spine surgery, e.g. ventral spine surgery or tumor surgery, image-guided approaches are still in an experimental stage. The technical development of image-guided techniques has reached a high level as the accuracies that can be achieved technically meet the anatomical demands. However, there is evidence that the interaction between the surgeon ('human factor') and the navigation system is a source of inaccuracy. It is concluded that more effort needs to be spend to understand this interaction.

Image guided percutaneous trans-pedicular screw fixation of the thoracic spine. A clinical evaluation

OBJECTIVE

We report our preliminary experience with a minimally invasive image guided percutaneous trans-pedicular fixation technique of the thoracic spine in patients with significant co-morbidity. This study aims to demonstrate the feasibility and efficacy of the presented operative technique as well as to detect potential drawbacks.

METHOD

A navigated percutaneous application of trans-pedicular screws was performed in 14 patients with radiological validated instability of the thoracic spine and significant medical co-morbidity. Due to poor bone quality, vertebroplasty of the affected levels had to be performed in nine patients. The levels involved were (T9-12) in ten patients, the middle (T5-8) in two patients and the upper thoracic (T1-4) segments in two others. VAS scores for local back pain were used to assess clinical outcome.

RESULTS

A total of 56 screws were inserted. There was no additional morbidity associated with the procedure. Post-operative CT scans and plain X-rays were obtained in all patients. In 2 (3.5%) medial penetration of the pedicle border occurred without neurological sequelae for the patient. Reduction of VAS scores regarding back pain during the first post-operative week was noted. Follow up ranged between 6 months and 12 months.

CONCLUSION

Navigated percutaneous trans-pedicular fixation of the thoracic spine is feasible and can be performed safely in patients where open surgery is of significant risk. Pre-operative planning is essential in order to avoid intra-operative complications with the instrumentation system.

Utility of intraoperative three-dimensional imaging at the hip and knee joints with and without navigation

Intraoperative three-dimensional imaging in orthopaedic trauma care has achieved greater importance over the last few years in some specialized hospital centers. For various types of peripheral-extremity trauma, clinical studies have confirmed, on the basis of three-dimensional information, an intraoperative revision rate ranging from 7% to 19%. Three-dimensional C-arm imaging may be used to achieve adequate intraoperative information about the quality of fracture reduction, residual steps, and correct implant placement, and this technique has been described for use in both the hip joint (for acetabular fractures, isolated femoral head [Pipkin-type] fractures, three-dimensional navigated sacroiliac screw or acetabular column screw placements, and, less frequently, for navigated drilling of tumors or osteochondral lesions) and the knee joint (for tibial plateau fractures, complex distal femoral condylar fractures, and navigated targeting of osteochondral lesions in combination with the use of preoperative magnetic resonance imaging scans). Major limitations of this technology include increased intraoperative time requirements, limited image quality compared with that of computed tomographic scans, cost, specific positioning techniques, and the need for radiolucent operating-room tables. Although prospective studies have yet to be conducted, the ways in which the surgeon will benefit from the use of intraoperative three-dimensional imaging are apparent, but indications for combined three-dimensional C-arm navigated procedures at the hip and knee joint are still limited. Future directions may include the use of digital flat-panel detectors and even robotic-controlled C-arm motion.

Computer-assisted surgical planning and image-guided surgical navigation in refractory adult scoliosis surgery: case report and review of the literature

STUDY DESIGN

Case report and literature review.

OBJECTIVE

In this case report, we present the utility of computer-assisted surgical planning and image-guided surgical navigation in the planning and execution of a major osteotomy to correct severe kyphoscoliosis.

SUMMARY OF BACKGROUND DATA

Computer-assisted surgical planning is useful to appreciate the three-dimensional nature of scoliotic deformities and allows for operative maneuvers to be simulated on a computer before their implementation in the operating room. Image-guided surgical navigation improves surgical accuracy and can help translate a virtual surgical plan to the operative setting.

METHODS

We report the case of a 38-year-old woman with severe, congenital kyphoscoliosis refractory to many previous surgeries, who presents with moderate progressive myelopathy and severe pain attributable to a sharp angular deformity at T12. Three-dimensional computed tomography reconstruction and computer-assisted surgical planning were used to determine the optimal corrective osteotomy. The surgical plan was translated to the operating room where a posterior vertebrectomy and instrumented correction were executed with the aid of image-guided surgical navigation.

RESULTS

The osteotomy was safely performed resulting in improved sagittal and coronal alignments, as well as, correction of the sharp kyphoscoliotic deformity at the thoracolumbar junction. At 6-month follow-up, the patient's myelopathy and pain had largely resolved and she expressed high satisfaction with the procedure.

CONCLUSION

We advocate this novel application of virtual surgical planning and intraoperative surgical navigation to improve the safety and efficacy of complex spinal deformity corrections.

A comparison of optical and electromagnetic computer-assisted navigation systems for fluoroscopic targeting

OBJECTIVES

Freehand targeting using fluoroscopic guidance is routine for placement of interlocking screws associated with intramedullary nailing and for insertion of screws for reconstruction of pelvic and acetabular injuries. New technologies that use fluoroscopy with the assistance of computer guidance have the potential to improve accuracy and reduce radiation exposure to patient and surgeon. We sought to compare 2 fluoroscopic navigation tracking technologies, optical and electromagnetic versus standard freehand fluoroscopic targeting in a standardized model.

INTERVENTION

Three experienced orthopaedic trauma surgeons placed 3.2-mm guide pins through test foam blocks that simulate cancellous bone. The entry site for each pin was within a circular (18-mm) entry zone. On the opposite surface of the test block (130-mm across), the target was a 1-mm-diameter radioopaque spherical ball marker. Each surgeon placed 10 pins using freehand targeting (control group) navigation using Medtronic iON StealthStation (Optical A), navigation using BrainLAB VectorVision (Optical B), or navigation using GE Medical Systems InstaTrak 3500 system (EM).

OUTCOME MEASUREMENTS

Data were collected for accuracy (the distance from the exit site of the guidewire to the target spherical ball marker), fluoroscopy time (seconds), and total number of individual fluoroscopy images taken.

RESULTS

The 2 optical systems and the electromagnetic system provided significantly improved accuracy compared to freehand technique. The average distance from the target was significantly (3.5 times) greater for controls (7.1 mm) than for each of the navigated systems (Optical A = 2.1 mm, Optical B = 1.9 mm EM = 2.4 mm; P < .05). Accuracy was similar for the 3 navigated systems, (P > 0.05). The ability to place guidewires in a 5-mm safe zone surrounding the target sphere was also significantly improved with the optical systems and the EM system (99% of wires in the safe zone) compared to controls (47% in the safe zone) (P < 0.002). Safe zone placement was similar among the 3 navigated systems (P > 0.05). Fluoroscopy time (seconds) and number of fluoroscopy images were similar among the three navigated groups (P > 0.05). Each of these parameters was significantly less when using the computer-guided systems than for freehand-unguided insertion (P < 0.01).

CONCLUSIONS

Both optical and electromagnetic computer-assisted guidance systems have the potential to improve accuracy and reduce radiation use for freehand fluoroscopic targeting in orthopaedic surgery.

Placement of C2 laminar screws using three-dimensional fluoroscopy-based image guidance

The use of C2 laminar screws in posterior cervical fusion is a relatively new technique that provides rigid fixation of the axis with minimal risk to the vertebral artery. The techniques of C2 laminar screw placement described in the literature rely solely on anatomical landmarks to guide screw insertion. The authors report on their experience with placement of C2 laminar screws using three-dimensional (3D) fluoroscopy-based image-guidance in eight patients undergoing posterior cervical fusion. Overall, fifteen C2 laminar screws were placed. There were no complications in any of the patients. Average follow-up was 10 months (range 3-14 months). Postoperative computed tomographic (CT) scanning was available for seven patients allowing evaluation of placement of thirteen C2 laminar screws, all of which were in good position with no spinal canal violation. The intraoperative planning function of the image-guided system allowed for 4-mm diameter screws to be placed in all cases. Using modified Odom's criteria, excellent or good relief of preoperative symptoms was noted in all patients at final follow-up.

The risks of pedicle wall breech with larger screws after undertapping

BACKGROUND CONTEXT

A linear relation exists between the insertional torque when placing a screw and the ultimate screw pullout strength; therefore, undertapping of the pedicle followed by insertion of a larger screw may enhance the pullout strength of the screw.

PURPOSE

To report the risk of pedicle wall breech with placement of 6.2-mm pedicle screws after undertapping with a 5.2-mm tap and to evaluate the effectiveness of direct visualization to identify these breeches. STUDY DESIGN/SETTINGS: Prospective evaluation of risks of pedicle wall breech with undertapping for a larger screw and the utility of directly visualizing pedicle walls during access and placement of pedicle screws for evidence of breech.

PATIENT SAMPLE

Sixty-five consecutive patients.

OUTCOME MEASURES

Intraoperative direct visualization of pedicle wall breech. Postoperative radicular leg symptoms.

METHODS

We prospectively analyzed placement of pedicle screws in sixty-five consecutive patients during lumbar-instrumented fusions after laminectomies performed by a single spine surgeon. Forty-four patients were primary fusions, and 21 were revisions. Twenty-seven were male, and 38 were female, with a mean age of 54.7 years (range, 15-85 years). Four hundred twenty-eight total pedicle screws were placed for an average of 6.6 screws per patient (range, 2-12 screws).

RESULTS

The incidence of pedicle wall breech during access was 0.7% (3/428) and 1.6% (7/428) after screw placement. 71% (5/7) of the screw breeches were noted with direct inspection of the pedicles intraoperatively, and 29% (2/7) were identified on postoperative X-ray films as lateral breakthroughs that were missed on intraoperative fluoroscopy and direct visualization. Therefore, 100% of misplaced screws potentially harmful to nerve roots were identified on direct visualization. Eighty percent occurred from L2-4.

CONCLUSIONS

This study provides evidence that undertapping of pedicles followed by placement of a larger diameter pedicle screw may breech the pedicle cortices. Although the risk is low, the authors recommend direct visualization of the pedicle walls during screw placement to identify caudad, medial, and cephalad breeches. This technique is for open laminectomies and should be added to the armamentarium of other techniques and not as a replacement.

Image guidance in spine surgery

Computer image guidance is one of the most significant recent technologic advancements in the field of spine surgery, because preoperative or intraoperative images can be used for multiplanar, three-dimensional intraoperative navigation. Laboratory and clinical studies have demonstrated that image guidance increases the safety and accuracy of a variety of spinal procedures. This article describes the application of intraoperative image guidance to spinal surgery, with a particular focus on minimal access procedures. Although commonly performed separately, these techniques can work in a complementary fashion. The apparent benefits and limitations of the various image-guided modalities are described.

Pedicle screw placement accuracy: a meta-analysis

STUDY DESIGN

A meta-analysis of the published literature was conducted specifically looking at accuracy and the postoperative methods used for the assessment of pedicle screw placement in the human spine.

OBJECTIVES

This study specifically aimed to identify postoperative methods used for pedicle screw placement assessment, including the most common method, and to report cumulative pedicle screw placement study statistics from synthesis of the published literature.

SUMMARY OF BACKGROUND DATA

Safety concerns have driven specific interests in the accuracy and precision of pedicle screw placement. A large variation in reported accuracy may exist partly due to the lack of a standardized evaluation method and/or the lack of consensus to what, or in which range, is pedicle screw placement accuracy considered satisfactory.

METHODS

A MEDLINE search was executed covering the span from 1966 until 2006, and references from identified papers were reviewed. An extensive database was constructed for synthesis of the identified studies. Subgroups and descriptive statistics were determined based on the type of population, in vivo or cadaveric, and separated based on whether the assistance of navigation was employed.

RESULTS

In total, we report on 130 studies resulting in 37,337 total pedicle screws implanted, of which 34,107 (91.3%) were identified as accurately placed for the combined in vivo and cadaveric populations. The most common assessment method identified pedicle screw violations simply as either present or absent. Overall, the median placement accuracy for the in vivo assisted navigation subgroup (95.2%) was higher than that of the subgroup without the use of navigation (90.3%).

CONCLUSIONS

Navigation does indeed provide a higher accuracy in the placement of pedicle screws for most of the subgroups presented. However, an exception is found at the thoracic levels for both the in vivo and cadaveric populations, where no advantage in the use of navigation was found.

Kosten- und Nutzenanalyse der intraoperativen 3D-Bildgebung

BACKGROUND

With intraoperative 3D imaging, inevitable corrections may be done already during the operation, and a second procedure can be avoided. The purpose of this study was to perform a cost-benefit analysis during the first year of intraoperative 3D application in order to provide a cost transparency for the surgeon within the current DRG system.

METHODS

On the basis of internal data and the literature, the annual operating costs of the ISO-C(3D) were calculated at 27,940 euros (purchase price, depreciation, maintenance, repair), the costs of an average revision as a secondary operation at 2,385 euros (costs avoided with the ISO-C(3D), Siremobil, Siemens, Erlangen, Germany), and the dynamic costs of an intraoperative 3D scan were averaged to 131.08 euros (draping, additional time, personnel).

RESULTS

In the year 2003 intraoperative 3D scanning was done in 126 patients, and intraoperative revision was performed in 24 (19%) due to the additional intraoperative 3D information provided by the Siremobil. In 11 (8.7%) patients the implant position was corrected and in 13 (10.3%) patients the reduction was improved. Taking only fixed costs into consideration, 29,311.52 euros could be saved, and when fixed and dynamic costs are taken into account 12,795.44 euros could be saved. Since the parameters for each hospital are different, the following formula for an individual computation is suitable. For the calculation of the cost the following mathematical relationship results: (annual fixed costs) + (costs per scan x number of cases) - (revision costs x revision rate [p]) x number of cases [N]) = 0.

DISCUSSION

Although the costs of an ISO-C(3D) are considerably high, an economic benefit can also accrue with frequent application and high rates of avoided revision. However, if the rate of avoided revision adds up to only 5%, a substantial deficit may result.

Minimally Invasive Transmuscular Pedicle Screw Fixation of the Thoracic and Lumbar Spine

OBJECTIVE:

This study assessed the feasibility and safety of percutaneous posterior pedicle screw fixation for instabilities of the thoracic and lumbar spine, using standard instruments designed for the open approach and fluoroscopy.

METHODS:

All patients who underwent percutaneous posterior pedicle screw fixation of the thoracic and lumbar spine were studied retrospectively. Charts and operative notes were analyzed for epidemiological data, underlying spinal pathological features, and indications for stabilization, stabilized segments, number of implanted pedicle screws, surgical time, and complications. Postoperative computed tomographic scans were analyzed for screw position.

RESULTS:

From May 2002 through May 2005, 115 internal fixators were implanted percutaneously in 104 patients. A total of 488 pedicle screws were implanted, stabilizing 1 to 5 spinal motion segments. Median surgical time was 93 minutes. On postoperative computed tomographic scans, 87% of screw positions were rated good, 10% were rated acceptable, and 3% were rated unacceptable. A total of 11 revisions were necessary, 9 for misplaced screws and 2 for loosening of anchor bolts. Only two of the patients experienced new clinical symptoms (i.e., radicular pain) because of screw misplacement. No patients experienced new neurological deficits or other surgery-related morbidity. @@@@CONCLUSION:@@ This study shows that percutaneous internal pedicle screw fixation using standard instruments is feasible and safe for posterior stabilization of the thoracic and lumbar spine. It is a straightforward alternative for open approaches or minimally invasive ones using navigation in conjunction with customized instruments. Accuracy of screw placement is similar to that reported for other techniques.

Minimally Invasive Fusion and Fixation Techniques

Instrumented fusion plays an important role in treating a variety of degenerative and traumatic diseases of the spine. Traditional open techniques have been associated with a high degree of approach-related morbidity because of muscle retraction and blood loss. A variety of minimally invasive techniques have been developed for instrumentation of the entire spine. Advances in our understanding of the cellular and molecular mechanisms for stable bony fusion should promote the use of even less invasive techniques in the future.

Minimally Invasive Approaches to Vertebral Column and Spinal Cord Tumors

Minimally invasive approaches to spinal tumors have evolved rapidly over the past 15 to 20 years as clinicians seek to avoid the morbidity and long-term dysfunction associated with traditional open surgical procedures. We review the noninvasive, percutaneous, and minimally invasive surgical techniques currently available for the treatment of spinal column and intradural spinal tumors, including minimal access thoracic corpectomy and minimal access intradural tumor surgery. The various advantages and limitations of these approaches as well as their appropriate indications and uses are also presented here. A measured understanding of surgical objectives and iatrogenic effects on patients' quality of life allows the surgeon to implement such minimally invasive approaches in the design of individualized treatment plans that range from pure palliation to definitive cure.