Percutaneous placement of posterior cervical screws using three-dimensional fluoroscopy

Low Radiation Protocol for Intraoperative Robotic C-Arm Can Enhance Adolescent Idiopathic Scoliosis Deformity Correction Accuracy and Safety

STUDY DESIGN

Retrospective case-series study.

OBJECTIVES

To assess (1) low cone beam CT (CBCT) mediated intraoperative navigation to limit radiation exposure without compromising surgical accuracy, and (2) the potential of intraoperative C-arm CBCT navigation to augment pedicle screw (PS) placement accuracy in AIS surgery compared to pre-surgery CT-based planning.

METHODS

The first part involved a prospective phantom study, comparing radiation doses for conventional CT, and standard (6sDCT) and a low dose (5sDCT) Artis Zeego®-imaging. Next, 5sDCT- and 6sDCT-navigation were compared on PS accuracy and radiation exposure during AIS correction. The final part compared surgical AIS deformity correction through intraoperative 5sDCT navigation to a matched cohort treated using conventional pre-surgery CT-scans for navigation. Outcome parameters included operation time, skin dose (SD), dose area product (DAP), intraoperative blood loss, postoperative complications, and PS deviation rates.

RESULTS

The phantom study demonstrated a reduction in radiation for the 5sDCT protocol. Moreover, 5sDCT-imaged patients (n = 15) showed a significantly lower SD (-27.41%) and DAP (-30.92%), without compromising PS accuracy compared with 6sDCT-settings (n = 15). Finally, AIS correction through intraoperative CBCT C-arm navigation (n = 27) significantly reduced screw deviation rates (6.83% versus 10.75%, P = .016) without increasing operation times, compared with conventional CT (n = 37).

CONCLUSIONS

Intraoperative navigation using a CBCT C-arm system improved the accuracy of PS insertion and reduced surgery time. Moreover, it reduced radiation exposure compared with conventional CT, which was further curtailed by adapting the low-dose 5sDCT protocol. In short, our study highlights the benefits of intraoperative CBCT navigation for PS placement in AIS surgery.

Minimally Invasive Instrumentation of the Cervical Spine: Past, Present, and Future

Posterior cervical instrumentation and fusion procedures are becoming more and more common with the aging population and rising numbers of multisegmental and revision procedures. The instrumentation of the cervical spine has so far been performed almost exclusively via open approaches. Over the past two decades, minimally invasive surgery (MIS) techniques have gained increasing popularity. To date, only a few attempts to instrument the cervical spine in a minimally invasive fashion have been reported. The following article, after a detailed review of the currently available literature, overviews MIS in dorsal cervical instrumentation and past, present and future techniques, and it discusses the current limitations. Nevertheless, and because of the multiple advantages of MIS instrumentation, a lot of work remains to be carried out to fully establish MIS procedures for posterior cervical instrumentation.

Minimally invasive lateral occipitocervical fixation: case series and technique description

PURPOSE

Occipitocervical junction (OCJ) instability is commonly treated with fixation via open posterior approach. The use of intraoperative navigation allows us to perform occipitocervical fixation via minimally invasive approach. We report a series of patients treated with percutaneous occipitocervical fixation, describing the surgical procedure in detail and discussing the technique.

METHODS

We prospectively enrolled 8 patients affected by OCJ instability secondary to trauma and rheumatoid arthritis. Traumatic patients were preoperatively evaluated with CT scan and MRI scan if needed. Rheumatoid arthritis group was evaluated with both CT and MR. Patients underwent percutaneous occipitocervical fixation with the assist of intraoperative 3D imaging and navigation. All patients were functionally and radiologically evaluated pre-, at 6 weeks, and at 1 year postoperatively.

RESULTS

Percutaneous occipitocervical fixation was successfully performed in all of the patients. 33 screws were placed. 29 (87.88%) were placed without any pedicle breach. In 3 (9.09%) screws we observed a minor; and in 1 (3.03%) screw we observed a major pedicle breach. We did not have any postoperative complications.

CONCLUSIONS

Described method of occipitocervical fixation is a minimally invasive method that has a similar outcome to the open technique. It requires the experience in open techniques and the assist of intraoperative 3D imaging and navigation to be performed efficiently.

The limitations of fully threaded screws in isolated percutaneous transarticular screw fixation of C1/C2

Demographic aging accompanied by increased falls inevitably leads to an increased incidence of atlantoaxial instabilities (AAI). Minimally invasive surgical procedures decrease the perioperative risk and regarding the treatment of AAI, percutaneous transarticular screw fixation of C1/C2 was more frequently considered in the past. This study aims to investigate the outcome of patients treated for AAI by isolated percutaneous transarticular screw fixation of C1/C2 (IPTSFC1/C2) using 3.5 mm fully threaded screws to identify its chances and limitations. In this retrospective study, data from patients who underwent IPTSFC1/C2 were analyzed. 23 patients (17 females and 6 males) with an average age of 73.1 years (y) were included. Mean VAS decreased significantly from preoperative 3.9 ± 1.8 to the last follow-up 2.6 ± 2.5 (p = 0.020) and neurological functions were preserved. In the radiological follow-up, we saw a single malposition of an inserted screw (2.27%) and one single bony fusion (4.54%). However, in 6 of 7 patients (85.71%), there was a loosening of the inserted screws due course. We demonstrated that the use of 3.5 mm fully threaded screws for IPTSFC1/C2 results in low rates of osseous fusions between C1 and C2. Therefore, their use in IPTSFC1/C2 is not suitable, especially for geriatric patients with impaired bone status.

Percutaneous Posterior Cervical Pedicle Instrumentation (C1 to C7) With Navigation Guidance: Early Series of 27 Cases

STUDY DESIGN

This is a technique paper describing minimally invasive, navigated, percutaneous pedicle screw fixation of the cervical spine. In addition, we include a retrospective feasibility analysis of our initial experience with 27 patients undergoing this procedure.

OBJECTIVE

The purpose of this study is to describe the technique of MIS navigated percutaneous cervical pedicle screw instrumentation and to report our initial experience.

METHODS

This is a retrospective review of 27 patients undergoing MIS navigated percutaneous posterior cervical pedicle screw fixation at 2 institutions. We describe the technique and report the radiographic outcomes and all intraoperative and postoperative complications.

RESULTS

A total of 27 patients underwent MIS navigated percutaneous pedicle screw fixation. Indications included odontoid fracture, subaxial fracture dislocations and burst fracture, pathological fracture, and degenerative spondylosis. There were no nerve root or vascular injuries. There were no spinal cord injuries. Two screws required repositioning intraoperatively, and 1 patient required reoperation for symptomatic malpositioned screw.

CONCLUSIONS

MIS navigated percutaneous posterior pedicle screw fixation can be performed safely. These constructs are biomechanically superior with neurovascular complication rates comparable to traditional lateral mass screw technique. While the current indications for this technique are relatively limited, the evolution of MIS cervical decompression techniques as well as navigation and robotics will provide an expanded role for percutaneous cervical pedicle screw instrumentation.

Advances in tissue state recognition in spinal surgery: a review

Spinal disease is an important cause of cervical discomfort, low back pain, radiating pain in the limbs, and neurogenic intermittent claudication, and its incidence is increasing annually. From the etiological viewpoint, these symptoms are directly caused by the compression of the spinal cord, nerve roots, and blood vessels and are most effectively treated with surgery. Spinal surgeries are primarily performed using two different techniques: spinal canal decompression and internal fixation. In the past, tactile sensation was the primary method used by surgeons to understand the state of the tissue within the operating area. However, this method has several disadvantages because of its subjectivity. Therefore, it has become the focus of spinal surgery research so as to strengthen the objectivity of tissue state recognition, improve the accuracy of safe area location, and avoid surgical injury to tissues. Aside from traditional imaging methods, surgical sensing techniques based on force, bioelectrical impedance, and other methods have been gradually developed and tested in the clinical setting. This article reviews the progress of different tissue state recognition methods in spinal surgery and summarizes their advantages and disadvantages.

Percutaneous, Navigated Minimally Invasive Posterior Cervical Pedicle Screw Fixation

BACKGROUND

Cervical pedicle screws provide significant biomechanical advantage but can be technically challenging and associated with morbid exposure. Improvements in intraoperative navigation guidance and instrumentation have made feasible this biomechanically robust, but technically challenging procedure. We present our initial experience with minimally invasive (MIS) percutaneous pedicle screw fixation in the cervical atlantoaxial and subaxial spine.

METHODS

A retrospective review was performed on 27 cases that involved a novel MIS percutaneous cervical pedicle screw technique. Small lateral skin incisions were made bilaterally on the neck using intraoperative navigation guidance. Subsequently, navigated, percutaneous screws were placed using the Proficient Minimally Invasive System (PROMIS; Spine Wave, Shelton, CT). Computed tomography (CT)-guided navigation was used for cervical pedicle screw placement with subsequent placement of percutaneous rods.

RESULTS

Indications for surgery included type II odontoid fractures, subaxial fracture dislocations and burst fracture, metastatic pathological burst fracture, and degenerative spondylosis with stenosis. There were 15 men and 12 women, with an average age 63.5 years. Follow-up ranged from 3 to 24 months (average = 16.7 months). One screw was revised intraoperatively. Two patients (7.7%) required reoperation, 1 patient required repositioning of a C5 pedicle screw, and 1 suffered a C7 body fracture. No nerve root injury, spinal cord injury, or vertebral artery injuries were reported.

CONCLUSIONS

Percutaneous cervical pedicle screw fixation is a feasible and safe technique when performed with CT-guided intraoperative navigation techniques. Cervical pedicle screw fixation provides a biomechanically superior construct in comparison with a lateral mass technique. In addition, the lack of paraspinal muscle disruption preserves important stabilizers of the posterior ligamentous complex and may reduce wound-healing issues in high-risk cases (eg, trauma patients). Although the current role for percutaneous instrumentation is relatively narrow, the advancement of MIS posterior cervical techniques may provide expanded opportunities in the future.

The Subaxial Cervical Pedicle Screw for Cervical Spine Diseases: The Review of Technical Developments and Complication Avoidance

This study aimed to review information on the subaxial cervical pedicle screw (CPS) including recent anatomical considerations, entry points, placement techniques, accuracy, learning curve, and complications. Relevant literatures were reviewed, and the authors’ experiences were summarized. The CPS is used for reconstruction of unstable cervical spine and achieves superior biomechanical stability compared to other fixation techniques. Various insertion and guidance techniques are established, among which, lateral fluoroscopy-assisted placement is the most common and cost-effective technique. Generally, placement under imaging guidance is more accurate than other techniques, and a three-dimensional template allows optimal trajectory for each pedicle regardless of intraoperative changes in spinal alignment. The free-hand technique using a curved pedicle probe without a funnel-like hole increases screw stability and reduces operation time, radiation exposure, and soft tissue injury. Compared to conventional lateral fluoroscopy-assisted placement, free-hand CPS placement by trained surgeons achieves superior accuracy comparable to that of image-guided navigation; in general, 30 training cases are sufficient for learning a safe and accurate technique for CPS placement. The complications of subaxial CPS are classified into three categories: complications due to screw misplacement, complications without screw misplacement, and others. Inexperienced surgeons may benefit from advanced techniques; however, the accuracy of CPS ultimately depends on the surgeon’s experience. Inexperienced surgeons should master the placement of the thoracolumbar pedicle screw in real practice and practice CPS insertion using cadavers. During the initial phase of the learning curve, careful preparation of surgery, reiterated identification, patterned safety steps, and supervision of the expert are necessary.

Posterior percutaneous transarticular stand-alone screw instrumentation of C1-C2 with endoscopic assistance: A report of two cases

We present two cases of minimally invasive posterior transarticular screw fixation of C1-C2. The points for screw insertion were visualized by endoscopy via the instrumental port. A patient with a type III odontoid fracture with subluxation underwent a minimally invasive posterior stand-alone transarticular screw fixation. Despite the application of compression screws, for technical reasons, only minimal compression on the anterior third of the C1-C2 lateral joint was achieved. However, complete fracture fusion was achieved with stable fibrous C1-C2 fusion 2.5 years postoperatively. A second patient with a chronic type II odontoid fracture underwent percutaneous C1-C2 fixation by the same method. After 2 years, fracture fusion and C1-C2 lateral mass ankylosis were achieved. The use of a tubular retractor and endoscopy in stand-alone screw fixation of C1-C2 allows direct visualization of the screw entry point and decreases surgical trauma. This procedure might be an alternative to other methods of transarticular instrumentation.

A new anatomical approach of cervical lateral mass for cervical pedicle screw and paravertebral foramen screw insertion

Thus far, anatomical studies have reported data on the cervical pedicle, with the focus remaining on the pedicle itself. It was necessary to obtain more comprehensive data about the relationships between the lateral mass, pedicle, and transverse foramen for cervical pedicle screwing (CPS) and paravertebral foramen screwing (PVFS), a new technique. The purpose of this study was to describe the relationships between the lateral mass, pedicle, and transverse foramen. This study analyzed computed tomography images from 77 patients (42 female, 35 male; mean age: 63.95 years). The anatomical pedicle transverse angle (PTA) and linear parameters of the lateral mass were measured, and the relationship between the calculated angles and the anatomical PTA was investigated. θp was defined as the convergence angle from the posterolateral edge of the lateral mass to the pedicle, and θc was defined as the convergence angle from the posterolateral edge of the lateral mass to the anterolateral corner of the vertebral foramen. The thickness of the cortical bone of the medial wall of the lateral mass (cT) and the medial (mT) and lateral (lT) walls of the pedicle at C3-7 were also measured. The PTA was similar to θp and θc at C3-6, but different at C7. In all cases, the transverse foramen was located more anterior to the posterior wall of the cervical body at C3-6, but not at C7. mT and cT were significantly thicker than lT at all levels. Lateral fluoroscopic images show that when the probe is inserted along θc, it meets the counter corner of the lateral mass at C3-6 without invasion of the transverse foramen if it does not cross the posterior wall of the vertebral body. This can be significant when performing CPS and PVFS.

Minimally Invasive Posterior Transarticular Stand-Alone Screw Instrumentation of C1-C2 Using a Transmuscular Approach: Description of Technique, Results and Comparison with Posterior Midline Exposure

PURPOSE

The aim of this study was to compare the feasibility, safety, and fusion results of posterior transarticular stand-alone screw (SAS) instrumentation of C1-C2 with a minimally invasive technique to those of a posterior midline exposure.

METHODS

Between 2008 and 2016, 164 patients underwent surgical treatment for traumatic injuries to the upper cervical vertebrae at our institution. We included 38 patients (27 men and 11 women; age range, 17-81 years) in the study. The posterior midline approach (PMA) group (23 patients) included patients who underwent surgery by means of a conventional midline incision after percutaneous screw insertion. The transmuscular approach (TMA) group (15 patients) included patients who underwent SAS fixation by use of a minimally invasive technique. The mean follow-up period was 58 months (range, 12-118 months).

RESULTS

Statistical analysis revealed that the operative time, blood loss volume, and severity of postoperative pain were lower in the TMA group. No significant excess of radiation exposure to the surgical team and the patients occurred in TMA group compared with the PMA group. C1-C2 fusion was observed in 37 patients. Stable fibrous fusion between the C1 and C2 vertebrae was found in 1 patient.

CONCLUSIONS

A minimally invasive technique by use of a paravertebral transmuscular approach provides an alternative to routine posterior transarticular SAS fixation of C1 and C2 through a posterior midline approach. The minimally invasive technique reduces the duration of surgery and the volume of blood loss, decreases the severity of postoperative pain, and does not increase the amount of radiation exposure for the surgical team and the patient.

Min-invasive surgical treatment for multiple axis fractures: A case report

BACKGROUND

Fractures of the axis are commonly seen in spinal injuries. Upper cervical fractures are usually managed conservatively. However, the complications due to long-term external immobilization cannot be ignored. The traditional open surgery has the disadvantages of too much blood loss and soft tissue injury. The aim of our paper is to introduce a minimally invasive surgical treatment for multiple axis fractures.

CASE SUMMARY

We report a 40-year-old Chinese male who had severe neck pain and difficult neck movement after falling from 3 meters. X-ray and computed tomography (CT) scan revealed an axis injury consisting of an odontoid Type III fracture associated with a Hangman fracture categorized as a Levine-Edwards Type I fracture. The patient underwent anterior odontoid screw fixation and posterior percutaneous screw fixation using intraoperative O-arm navigation. Neck pain was markedly improved after surgery. X-rays and CT scan reconstructions of 3-mo follow-up showed good stability and fusion. The range of cervical motion was well preserved.

CONCLUSION

Anterior odontoid screw fixation and posterior direct C2 percutaneous pedicle screw fixation with the aid of O-arm navigation and neurophysiological monitoring can be an interesting alternative option for complicated multiple axis fractures.

Minimally Invasive Cervical Pedicle Screw Fixation by a Posterolateral Approach for Acute Cervical Injury

STUDY DESIGN

This is a retrospective case series.

OBJECTIVE

To avoid lateral misplacement of midcervical pedicle screws, T.T., one of our authors, developed a method for minimally invasive cervical pedicle screw (MICEPS) fixation by a posterolateral approach. We reviewed our initial experience with this fixation for trauma cases.

SUMMARY OF BACKGROUND DATA

Excellent clinical results with cervical screws have been reported for trauma cases. Although cervical pedicle screw fixation can be an essential part of reconstruction in spinal disorders, there is also a risk for injury to the vertebral artery.

METHODS

This study included 56 consecutive patients who received surgery for cervical fractures. We inserted a total of 203 cervical pedicle screws. Nineteen patients were treated by conventional methods. Thirty-seven patients were treated by MICEPS fixation. According to the MICEPS fixation, 12 patients were treated by unilateral fusion, 25 patients by bilateral fusion. All pedicle screws were inserted using spinal navigation system in the both groups.

RESULTS

The average surgical time was 217 minutes with the conventional pedicle screw fixation and 165 minutes with the MICEPS fixation (P=0.0014). The average intraoperative bleeding was 560 mL in the conventional fixation and 140 mL in the MICEPS fixation (P<0.0001). Clinically significant screw deviation was significantly lower in the MICEPS fixation group than in the conventional cervical pedicle screw group (P=0.0039). There was not any deep wound infection in both groups.

CONCLUSIONS

This intramuscular approach allows for horizontal pedicle screw insertion. This technique is probably useful for reducing intraoperative bleeding. In this study, incidence of screw perforation was significantly lower in the MICEPS fixation group than in the conventional cervical pedicle screw group. In particular, neither of the misplaced screws was laterally deviated in the MICEPS group.

Reduced Acute Care Costs With the ERAS® Minimally Invasive Transforaminal Lumbar Interbody Fusion Compared With Conventional Minimally Invasive Transforaminal Lumbar Interbody Fusion

BACKGROUND

Enhancing Recovery After Surgery (ERAS®) programs have been widely adopted throughout the world, but not in spinal surgery. In this report, we review the implementation of a “fast track” surgery for lumbar fusion and its effect on acute care hospitalization costs.

OBJECTIVE

To determine if a “fast track” surgery methodology results in acute care cost savings.

METHODS

Thirty-eight consecutive ERAS patients were compared with patients undergoing conventional minimally invasive transforaminal lumbar interbody fusion. Differences between these groups included the use of endoscopic decompression, injections of liposomal bupivacaine, and performing the surgery under sedation in the ERAS® group.

RESULTS

Patients had similar medical comorbidities (2.02 vs 2 for ERAS® and comparator groups, respectively; P = .458). Body mass index was similar (26.5 vs 27.0; P = .329). ERAS® patients were older (65 vs 59 yr, P = .031). Both groups had excellent clinical results with an improvement of 23% and 24%, respectively. Intraoperative blood loss was less (68 ± 31 cc vs 231 ± 73, P &lt; 0.001). Length of stay was also less with ERAS® surgery, at a mean of 1.23 ± 0.8 d vs 3.9 ± 1.1 d (P = 0.009). When comparing ERAS® surgery to standard minimally invasive transforaminal lumbar interbody fusion, the total cost for the acute care hospitalization was $19 212 vs $22 656, respectively (P &lt; 0.001). This reflected an average of $3444 in savings, which was a 15.2% reduction.

CONCLUSION

ERAS® programs for spinal fusion surgery have the potential to reduce the costs of acute care. This is made possible by leveraging less invasive interventions to minimize soft tissue damage.

Differences between Manufacturers of Computed Tomography-Based Computer-Assisted Surgery Systems Do Exist: A Systematic Literature Review

STUDY DESIGN

Literature review.

OBJECTIVE

Several studies have shown that the accuracy of pedicle screw placement significantly improves with use of computed tomography (CT)-based navigation systems. Yet, there has been no systematic review directly comparing accuracy of pedicle screw placement between different CT-based navigation systems. The objective of this study is to review the results presented in the literature and compare CT-based navigation systems relative only to screw placement accuracy.

METHODS

Data sources included CENTRAL, Medline, PubMed, and Embase databases. Studies included were randomized clinical trials, case series, and case-control trials reporting the accuracy of pedicle screws placement using CT-based navigation. Two independent reviewers extracted the data from the selected studies that met our inclusion criteria. Publications were grouped based on the CT-based navigation system used for pedicle screw placement.

RESULTS

Of the 997 articles we screened, only 26 met all of our inclusion criteria and were included in the final analysis, which showed a significant statistical difference (p < 0.0001, 95% confidence interval 0.92 to 1.23) in accuracy of pedicle screw placement between three different CT-based navigation systems. The mean (weighted) accuracy of pedicle screws placement based on the CT-based navigation system was found to be 97.20 ± 2.1% in StealthStation (Medtronic, United States) and 96.1 ± 3.9% in VectorVision (BrainLab, Germany).

CONCLUSION

This review summarizes results presented in the literature and compares screw placement accuracy using different CT-based navigation systems. Although certain factors such as the extent of the procedure and the experience and skills of the surgeon were not accounted for, the differences in accuracy demonstrated should be considered by spine surgeons and should be validated for effects on patients' outcome.

Endoscopic minimally invasive transforaminal interbody fusion without general anesthesia: initial clinical experience with 1-year follow-up

OBJECTIVE One of the principal goals of minimally invasive surgery has been to speed postoperative recovery. In this case series, the authors used an endoscopic technique for interbody fusion combined with percutaneous screw fixation to obviate the need for general anesthesia. METHODS The first 10 consecutive patients treated with a minimum of 1 year's follow-up were included in this series. The patients were all treated using endoscopic access through Kambin's triangle to allow for neural decompression, discectomy, endplate preparation, and interbody fusion. This was followed by percutaneous pedicle screw and connecting rod placement using liposomal bupivacaine for long-acting analgesia. No narcotics or regional anesthetics were used during surgery. RESULTS All patients underwent the procedure successfully without conversion to open surgery. The patients' average age was 62.2 ± 9.0 years (range 52-78 years). All patients had severe disc height collapse, and 60% had a Grade I spondylolisthesis. The mean operative time was 113.5 ± 6.3 minutes (range 105-120 minutes), and blood loss was 65 ± 38 ml (range 30-190 ml). The mean length of hospital stay was 1.4 ± 1.3 nights. There were no intraoperative or postoperative complications. Comparison of preoperative and final clinical metrics demonstrated that the Oswestry Disability Index improved from 42 ± 11.8 to 13.3 ± 15.1; the 36-Item Short Form Health Survey (SF-36) Physical Component Summary improved from 47.6 ± 3.8 to 49.7 ± 5.4; the SF-36 Mental Component Summary decreased from 47 ± 3.9 to 46.7 ± 3.4; and the EQ-5D improved from 10.7 ± 9.5 to 14.2 ± 1.6. There were no cases of nonunion identified radiographically on follow-up imaging. CONCLUSIONS Endoscopic fusion under conscious sedation may represent a feasible alternative to traditional lumbar spine fusion in select patients. Larger clinical series are necessary to validate that clinical improvements are sustained and that arthrodesis rates are successful when compared with open surgery. This initial experience demonstrates the possible utility of this procedure.

Morphometric measurement of the cervical spine for minimally invasive pedicle screw fixation using reverse engineering and three-dimensional reconstruction

BACKGROUND

Percutaneous cervical pedicle screw fixation has been proven to be an effective method of cervical screw instrumentation, which has the advantages of less invasiveness and low blood loss. Emerging evidence has indicated that the cervical spinous process plays an important role in percutaneous spine surgery. However, there is a limited amount of information on the fundamental research of pedicle and its associated imaging parameter measurement. The purpose of this study was to measure the anatomic data of the pedicle screw channel (PSC) using reverse engineering and three-dimensional reconstruction, and also to discuss the three-dimensional relationship between the cervical spinous process and the pedicle screw channel.

METHODS

Twenty adult subjects (10 males, 10 females, age range 19-46 years) were studied using the method of three-dimensional CT reconstruction and reverse engineering. The centrum was divided into 10 equal parts from front to back. The bisectors were defined as borderline depths of the centrum, from front to back, 100%, 90%, 80%, 70%, 60%, 50%, 40%, 30%, 20%, 10%, 0% of borderline depths were presented. Then, a 3D coordinate system was constructed to measure all the data, including the radius of the inscribed circle, the length of the PSC, the insertion angle, the distances from entry point to cervical spinous process and skin depth. All the indexes were measured from 70% to 90% borderline depth.

RESULTS

The radius of the inscribed circles from C₃ to C₇ at 90% borderline depth were 2.94 ± 0.55 mm, 3.04 ± 0.40 mm, 3.15 ± 0.36 mm, 3.28 ± 0.47 mm, 3.89 ± 0.54 mm, respectively. The lengths of the PSC were between 25 and 32 mm. The insertion angles for 70% to 90% borderline depth were 28.33°, 34.28°, 37.92°, respectively. The relationship between the PSC and spinous process was measured as the distance from the entry point to the end of the spinous process, which were, respectively, 26.91 mm, 28.18 mm, 30.03 mm, 35.67 mm, 41.99 mm from C₃ to C₇ .The distance from the skin to the entry point of C_3-7 increased gradually.

CONCLUSIONS

The measurements of this study could provide detailed information for percutaneous cervical screw fixation. The data of the relationship between the cervical spinous process and the pedicle screw channel present valuable technical information for the design, optimization and clinical application of the aiming device for percutaneous cervical pedicle screw fixation. Copyright © 2016 John Wiley & Sons, Ltd.

Direct C2 Pedicle Screw Fixation for Axis Body Fracture

BACKGROUND

Acute complex C2 vertebral body fracture specifically does not involve the odontoid process or C2 pars interarticularis. External stabilization can be effective but may prolong healing and increase morbidity. Many traditional surgical techniques can achieve internal stabilization at the expense of normal cervical motion. We describe direct surgical C2 pedicle screw fixation as an option for managing acute complex C2 vertebral body fracture.

CASE DESCRIPTION

Three patients were treated with direct pedicle screw fixation of acute traumatic complex C2 vertebral body fractures. All fractures were coronally oriented Benzel type 1. None of the patients sustained neurological injury. Stereotactic navigation with intraoperative computed tomography scanning was used for each procedure. Surgery provided immediate internal orthosis and stability, as judged by intraoperative dynamic fluoroscopy. Rigid cervical collar bracing was used for 1 month after surgery when the patients were out of bed. Initial radiographs showed acceptable screw placement and fracture alignment. Dynamic radiographs at 3 months showed structural stability at the fracture site and adjacent levels, and complete bony union was confirmed with late computed tomography scanning (>1 year) in each case. Each patient reported resolution of trauma-related and postsurgical pain at 30-day follow-up. Postoperative Neck Disability Index questionnaires for each patient suggested no significant disability at 1 year.

CONCLUSIONS

Direct pedicle screw fixation of acute complex C2 vertebral body fracture appeared to be safe and effective in our 3 patients. It may provide a more-efficient and less-morbid treatment than halo brace or cervical collar immobilization in some patients.

Thoracic Pedicle Screw Placement Guide Plate Produced by Three-Dimensional (3-D) Laser Printing

Background

The aim of this study was to evaluate the accuracy and feasibility of an individualized thoracic pedicle screw placement guide plate produced by 3-D laser printing.

Material/Methods

Thoracic pedicle samples of 3 adult cadavers were randomly assigned for 3-D CT scans. The 3-D thoracic models were established by using medical Mimics software, and a screw path was designed with scanned data. Then the individualized thoracic pedicle screw placement guide plate models, matched to the backside of thoracic vertebral plates, were produced with a 3-D laser printer. Screws were placed with assistance of a guide plate. Then, the placement was assessed.

Results

With the data provided by CT scans, 27 individualized guide plates were produced by 3-D printing. There was no significant difference in sex and relevant parameters of left and right sides among individuals (P>0.05). Screws were placed with assistance of guide plates, and all screws were in the correct positions without penetration of pedicles, under direct observation and anatomic evaluation post-operatively.

Conclusions

A thoracic pedicle screw placement guide plate can be produced by 3-D printing. With a high accuracy in placement and convenient operation, it provides a new method for accurate placement of thoracic pedicle screws.

Minimally Invasive Pedicle Screw Fixation Using Intraoperative 3-dimensional Fluoroscopy-based Navigation (CAMISS Technique) for Hangman Fracture

STUDY DESIGN

Retrospective comparative cohort series.

OBJECTIVE

To evaluate the accuracy and feasibility of minimally invasive surgical (MIS) techniques incorporating with intraoperative 3-dimensional fluoroscopy-based navigation (ITFN) for treating Hangman fracture.

SUMMARY OF BACKGROUND DATA

MIS screw fixation for Hangman fracture can decrease iatrogenic soft-tissue injury, but increase the risk of instrumentation-related complications due to lack of anatomical landmarks. With the advantages of obtaining intraoperative real-time images, automatic registration, and 3-dimensional views, the ITFN system seems to be an inherent partner for MIS.

METHODS

20 patients with Hangman fracture underwent C2-C3 pedicle screw fixation using ITFN. 6 patients used MIS technique, with the other 14 patients using conventional open technique. Operative time and blood loss were recorded. The accuracy of screw positions was studied by postoperative CT scan. Neck pain visual analogue score (VAS) was evaluated and the fusion status was ascertained in 6-month follow-up.

RESULTS

The average operative time was 134.2 ± 8.0 minutes in computer-assisted orthopaedics surgery (CAOS)-MIS group and 139.3 ± 25.8 minutes in CAOS-open group (P > 0.01). The blood loss was 66.7 ± 25.8 mL in CAOS-MIS group and 250.0 ± 141.4 mL in CAOS-open group (P < 0.01). A total of 80 screws were inserted. No screw-related neurovascular injury was observed. 83.3% (20/24) screws in CAOS-MIS group and 89.3% (50/56) screws in CAOS-open group were grade 1 screw (P > 0.01). No grade 3 screw was detected in both groups. Compared with the CAOS-open group (1.7 ± 0.6), neck pain VAS in 6-month follow-up in CAOS-MIS group (0.3 ± 0.5) was significantly lower (P < 0.01). Solid fusion was demonstrated in all the cases.

CONCLUSION

The integration of these 2 techniques MIS and ITFN, we call "computer assisted minimally invasive spinal surgery," is proved to be feasible and safe for treating Hangman fracture with the advantage of significantly reduced iatrogenic soft tissue injury. So we think CAMISS technique represents the most recent modification of spine surgery.

3D navigation of endoscopic rhizotomy at the lumbar spine

We present a detailed description of the surgical technique and the preliminary results of an endoscopic denervation for patients with chronic low back pain (CLBP) originating from the facet joints (FJ). Endoscopic denervation of the medial branches of the dorsal rami supplying the FJ has recently been appraised as providing excellent intraoperative visualization and long term pain relief for these patients. Conventional endoscopic rhizotomy has been expanded to include a the precise localization of 3D navigation. A surgical description and the results of our first four patients treated with 3D navigated endoscopic rhizotomy (3DNER) are presented. Four patients with a mean age of 59years and a follow-up time of 2months were included. All patients reported pain reduction in the immediate postoperative period, while three patients (75%) had long lasting relief. The patient without persisting relief had previously sustained a lumbar disc prolapse and only achieved minor pain relief with preoperative FJ infiltration, compared to the significant relief that was seen in the other patients. In contrast to conventional rhizotomy, 3DNER enables the surgeon to ablate more precisely and extensively, which is especially useful if scar tissue is present from previous injuries or surgeries. When successful, this technique may provide long lasting pain relief, especially if the preoperative FJ infiltrations are followed by a substantial pain reduction.

Safe and accurate placement of thoracic and thoracolumbar percutaneous pedicle screws without image-navigation

Background:

Percutaneous pedicle screw placement is now commonly used to treat spinal instability. It is imperative, especially at thoracic levels, to avoid damage to adjacent neurovascular structures. Although more technically demanding when compared with the lumbar spine, we believe that the percutaneous placement of thoracic pedicle screws can be performed safely without image-navigation.

Purpose:

The purpose was to evaluate the safety of percutaneous pedicle screw placement in the thoracic and thoracolumbar spine without image-navigation.

Study Design/Setting:

A retrospective study at a single institution.

Patient Sample:

Patients over the age of 18 years who presented with degenerative disease, trauma or tumor that required surgical stabilization.

Outcome Measures:

Our outcomes included postoperative plain film X-rays and computerized tomography (CT).

Materials and Methods:

We performed a retrospective study of patients who underwent percutaneous pedicle screw placement without image-navigation between T2 and L2.

Results:

Between 2005 and 2011, a total of 507 pedicle screws were placed in 120 patients. The indications included trauma (17%), tumor (8%), and degenerative conditions (75%). The mean age was 61.3 years (range: 20–81 years). Fifty-seven percent were male, and 43% were female. The mean blood loss was 297 ± 40 ml. All patients underwent postoperative anterior-posterior and lateral films that showed safe placement of pedicle screws. Moreover, 57% of patients underwent postoperative CT imaging. There was 1 (0.4%) medial breach and 13 (5%) lateral breaches of the pedicle screw patients who underwent CT imaging as read by an independent neuroradiologist. None of the breaches resulted in adverse neurological sequelae either immediately after or at most recent follow-up.

Conclusion:

Thoracic and thoracolumbar percutaneous pedicle screw placement can be performed safely and accurately without image-navigation.

Cervical pedicle screw fixation at C6 and C7: A cadaveric study

BACKGROUND

Cervical pedicle screw fixation is an effective method for treating traumatic and non traumatic injuries. But many studies have reported higher incidence of cervical pedicle penetration, so many research efforts have aimed at improving the accuracy of cervical screw fixation. Most of the anatomical studies on cervical pedicle screw placement previously published focused on the measurements of anatomical parameters, the entry point of pedicle screw is vague. We preliminarily designed a C3, C4 and C5 pedicle screw fixation method that had clear entry point and clinical cases confirmed that this method is feasible and safe. So we did this study of cervical pedicle screw fixation for C6 and C7 vertebrae.

MATERIALS AND METHODS

Fifteen cervical vertebrae specimens were prepared and bilateral pedicle screws were manually inserted into C6 and C7. The intersection of the horizontal line through the midpoint of the transverse process root and the vertical line through the intersection of the posterolateral and posterior planes of the isthmus was the entry point. The screws were inserted along the axis of the pedicle, with the screw axis coinciding with the pedicle. The pedicle was truncated axially and sagittally along the trajectory and the narrowest pedicular height (PH), pedicular width (PW), overall length of the screw channel (LSC), transverse angle (E) and vertical angle (F) were measured.

RESULTS

In C6, the PW and PH were 6.12 ± 0.78 and 7.48 ± 0.81 mm, respectively. In C7, the PW and PH were 6.85 ± 0.73 and 8.03 ± 0.38 mm, respectively. The LSC was 30.83 ± 0.91 mm. Two E angles were identified, namely E1 and E2 and their values were 89.61 ± 1.24 and 59.71 ± 1.10°, respectively. Meanwhile, F averaged 75.86 ± 1.12°.

CONCLUSION

The intersection of the horizontal line through the midpoint of the transverse process root and vertical line through the intersection of the posterolateral and posterior planes of the isthmus can be used as an entry point for C6 and C7 pedicle screw fixation. The screws should be inserted at 60 or 90° with the posterolateral isthmus in the horizontal plane and at 75° with the posterior isthmus in the sagittal plane. The LSC should not exceed 30 mm.

Three-dimensional Intraoperative Imaging Modalities in Orthopaedic Surgery: A Narrative Review

Intraoperative imaging and navigation systems have revolutionized orthopaedic surgery for the spine, joints, and orthopaedic trauma. Imaging modalities such as the isocentric C-arm, O-arm imaging, and intraoperative MRI or navigation systems allow the visualization of surgical instruments and implants relative to a three-dimensional CT image or MRI. Studies show that these technologies lower the rates of implant misplacement and inadequate fracture reduction, thereby improving surgical outcomes and reducing reoperation rates. An additional benefit is reduced radiation exposure compared with that for conventional fluoroscopy. Concerns surrounding adoption of these technologies include cost and increased operating times, but improvements in design and protocol may improve the integration of these imaging modalities into the operating room.

Neuronavigation in minimally invasive spine surgery

OBJECT

Parallel advancements in image guidance technology and minimal access techniques continue to push the frontiers of minimally invasive spine surgery (MISS). While traditional intraoperative imaging remains widely used, newer platforms, such as 3D-fluoroscopy, cone-beam CT, and intraoperative CT/MRI, have enabled safer, more accurate instrumentation placement with less radiation exposure to the surgeon. The goal of this work is to provide a review of the current uses of advanced image guidance in MISS.

METHODS

The authors searched PubMed for relevant articles concerning MISS, with particular attention to the use of image-guidance platforms. Pertinent studies published in English were further compiled and characterized into relevant analyses of MISS of the cervical, thoracic, and lumbosacral regions.

RESULTS

Fifty-two studies were included for review. These describe the use of the iso-C system for 3D navigation during C1-2 transarticular screw placement, the use of endoscopic techniques in the cervical spine, and the role of navigation guidance at the occipital-cervical junction. The authors discuss the evolving literature concerning neuronavigation during pedicle screw placement in the thoracic and lumbar spine in the setting of infection, trauma, and deformity surgery and review the use of image guidance in transsacral approaches.

CONCLUSIONS

Refinements in image-guidance technologies and minimal access techniques have converged on spinal pathology, affording patients the ability to undergo safe, accurate operations without the associated morbidities of conventional approaches. While percutaneous transpedicular screw placement is among the most common procedures to benefit from navigation, other areas of spine surgery can benefit from advances in neuronavigation and further growth in the field of image-guided MISS is anticipated.

Miniopen pedicle subtraction osteotomy: surgical technique and initial results

As minimally invasive surgery (MIS) has advanced to treat diverse diseases, there has been an increasing need for MIS surgery to be able to restore lumbar lordosis and treat sagittal balance abnormalities. In this article, the surgical technique and initial clinical and radiographic outcomes with a new miniopen pedicle subtraction osteotomy technique are outlined. Combining the MIS techniques of interbody fusion, percutaneous screw fixation, and facet fusion with a selective opening for the osteotomy site allows for safe and efficient deformity corrections. This technique resulted in an average increase of 29.2° of lumbar lordosis (range 17°-44°).

A biomechanical comparison of three different posterior fixation constructs used for c6-c7 cervical spine immobilization: a finite element study

The intralaminar screw construct has been recently introduced in C6–C7 fixation. The aim of the study is to compare the stability afforded by three different C7 posterior fixation techniques using a three-dimensional finite element model of a C6–C7 cervical spine motion segment. Finite element models representing three different cervical anchor types (C7 intralaminar screw, C7 lateral mass screw, and C7 pedicle screw) were developed. Range of motion (ROM) and maximum von Mises stresses in the vertebra for the three screw techniques were compared under pure moments in flexion, extension, lateral bending, and axial rotation. ROM for pedicle screw construct was less than the lateral mass screw construct and intralaminar screw construct in the three principal directions. The maximum von Misses stress was observed in the C7 vertebra around the pedicle in all the three screw constructs. Maximum von Mises stress in pedicle screw construct was less than the lateral mass screw construct and intralaminar screw construct in all loading modes. This study demonstrated that the pedicle screw fixation is the strongest instrumentation method for C6–C7 fixation. Pedicle screw fixation resulted in least stresses around the C7 pedicle-vertebral body complex. However, if pedicle fixation is not favorable, the laminar screw can be a better option compared to the lateral mass screw because the stress around the pedicle-vertebral body complex and ROM predicted for laminar screw construct was smaller than those of lateral mass screw construct.

A Biomechanical Comparison of Intralaminar C7 Screw Constructs with and without Offset Connector Used for C6-7 Cervical Spine Immobilization : A Finite Element Study

OBJECTIVE

The offset connector can allow medial and lateral variability and facilitate intralaminar screw incorporation into the construct. The aim of this study was to compare the biomechanical characteristics of C7 intralaminar screw constructs with and without offset connector using a three dimensional finite element model of a C6-7 cervical spine segment.

METHODS

Finite element models representing C7 intralaminar screw constructs with and without the offset connector were developed. Range of motion (ROM) and maximum von Mises stresses in the vertebra for the two techniques were compared under pure moments in flexion, extension, lateral bending and axial rotation.

RESULTS

ROM for intralaminar screw construct with offset connector was less than the construct without the offset connector in the three principal directions. The maximum von Misses stress was observed in the C7 vertebra around the pedicle in both constructs. Maximum von Mises stress in the construct without offset connector was found to be 12-30% higher than the corresponding stresses in the construct with offset connector in the three principal directions.

CONCLUSION

This study demonstrated that the intralaminar screw fixation with offset connector is better than the construct without offset connector in terms of biomechanical stability. Construct with the offset connector reduces the ROM of C6-7 segment more significantly compared to the construct without the offset connector and causes lower stresses around the C7 pedicle-vertebral body complex.

A novel method of cervical pedicle screw placement from C3 to C5 and its clinical applications

STUDY DESIGN

Applied anatomical study and clinical application.

OBJECTIVE

To design and optimize the method of cervical pedicle screw placement for cervical vertebrae C3-C5, and to test it in clinical applications.

SUMMARY OF BACKGROUND DATA

Most of the anatomical studies on cervical pedicle screw placement previously published focused on the lower cervical vertebrae. Clinically, it is much more difficult to place C3, C4, and C5 screws than C6 and C7 screws; therefore, anatomical measurements of C3-C5 pedicles and design of an appropriate screw placement method are required.

METHODS

A total of 20 cervical vertebrae specimens were prepared, and bilateral pedicle screws were manually inserted for C3-C5. The intersection of the horizontal line through the midpoint of the transverse process root and the vertical line through the mediolateral third of the superior articular process was used as the entry point. The screws were inserted along the axis of the pedicle, with the axis of the screw coinciding with that of the pedicle. The specimens were truncated along the horizontal or sagittal plane of the pedicle, and a variety of measurements were made to determine appropriate screw type and placement. Finally, this screw fixation technique was applied in clinical situations with the placement of 26 C3 screws, 26 C4 screws, and 38 C5 screws.

RESULTS

Pedicular height was larger than pedicular width for the same segment of C3-C5, and pedicular width of the different segments did not significantly vary. The lengths of the screw channels for C3-C5 screw placement were similar. The transverse angles of C3-C5 segments displayed a decreasing trend, whereas the vertical angles did not. In all clinical cases, all screws were properly within the pedicles examined using postoperative computed tomography scan. Only 1 C3 screw penetrated the medial cortex and slightly entered the spinal canal, but no clinical symptoms occurred.

CONCLUSION

The intersection of the horizontal line through the midpoint of the transverse process root and the vertical line through the mediolateral third of the superior articular process represents a superior frame of reference for the entry point for C3-C5 pedicle screw fixation. Clinically, we recommend the transverse angles to be 90° for C3 and 80° for C4 and C5, and the vertical angles to be 70° for C3-C5. We found that screws with a diameter of 3.5 mm and length of 20 mm or 22 mm to be safe, objective, and reliable.

Navigated guide tube for the placement of mini-open pedicle screws using stereotactic 3D navigation without the use of K-wires

Object

Three-dimensional spinal navigation increases screw accuracy, but its implementation in clinical practice has been difficult, mainly because of surgeons' concerns about increased operative times, disturbance of workflow, and safety. The authors present a custom-designed navigated guide that addresses some of these concerns by allowing for drilling, tapping, and placing the final screw via a minimally invasive approach without the need for K-wires. In this paper, the authors' goal was to describe the technical aspects of the navigated guide tube as well as pedicle screw accuracy.

Methods

The authors present the technical details of a navigated guide that allows drilling, tapping, and the placement of the final screw without the need for K-wires. The first 10 patients who received minimally invasive mini-open spinal pedicle screws are presented. The case series focuses on the immediate postoperative outcomes, pedicle screw accuracy, and pedicle screw–related complications. An independent board-certified neuroradiologist determined pedicle screw accuracy according to a 4-tiered grading system.

Results

The navigated guide allowed successful placement of mini-open pedicle screws as part of posterior fixation from L-1 to S-1 without the use of K-wires. Only 7-mm-diameter screws were placed, and 72% of screws were completely contained within the pedicle. Breaches less than 2 mm were seen in 23% of cases, and these were all lateral except for one screw. Breaches were related to the lateral to medial trajectory chosen to avoid the superior facet joint. There were no complications related to pedicle screw insertion.

Conclusions

A novel customized navigated guide tube is presented that facilitates the workflow and allows accurate placement of mini-open pedicle screws without the need for K-wires.

A novel radiographic targeting guide for percutaneous placement of transfacet screws in the cervical spine with limited fluoroscopy: A cadaveric feasibility study

Background

We describe a technique for percutaneous transfacet screw placement in the cervical spine without the need for lateral-view fluoroscopy.

Methods

Previously established articular pillar morphometry was used to define the ideal trajectory for transfacet screw placement in the subaxial cervical spine. A unique targeting guide was developed to allow placement of Kirschner wires across the facet joint at 90° without the guidance of lateral-view fluoroscopy. Kirschner wires and cannulated screws were placed percutaneously in 7 cadaveric specimens. Placement of instrumentation was performed entirely under modified anteroposterior-view fluoroscopy. All specimens were assessed for acceptable screw placement by 2 fellowship-trained orthopaedic spine surgeons using computed tomography. Open dissection was used to confirm radiographic interpretation. Acceptable placement was defined as a screw crossing the facet joint, achieving purchase in the inferior and superior articular processes, and not violating critical structures. Malposition was defined as a violation of the transverse foramen, spinal canal, or nerve root or inadequate fixation.

Results

A total of 48 screws were placed. Placement of 45 screws was acceptable. The 3 instances of screw malposition included a facet fracture, a facet distraction, and a C6-7 screw contacting the C7 nerve root in a specimen with a small C7 superior articular process.

Conclusions

Our data show that with the appropriate radiographic technique and a targeting guide, percutaneous transfacet screws can be safely placed at C3-7 without the need for lateral-view fluoroscopy during the targeting phase. Because of the variable morphometry of the C7 lateral mass, however, care must be taken when placing a transfacet screw at C6-7.

Clinical Relevance

This study describes a technique that has the potential to provide a less invasive strategy for posterior instrumentation of the cervical spine. Further investigation is needed before this technique can be applied clinically.

Comparison of revision strategies for failed C2-posterior cervical pedicle screws: a biomechanical study

STUDY PURPOSE

With increasing usage within challenging biomechanical constructs, failures of C2 posterior cervical pedicle screws (C2-pCPSs) will occur. The purpose of the study was therefore to investigate the biomechanical characteristics of two revision techniques after the failure of C2-pCPSs.

MATERIALS AND METHODS

Twelve human C2 vertebrae were tested in vitro in a biomechanical study to compare two strategies for revision screws after failure of C2-pCPSs. C2 pedicles were instrumented using unicortical 3.5-mm CPS bilaterally (Synapse/Synthes, Switzerland). Insertion accuracy was verified by fluoroscopy. C2 vertebrae were potted and fixed in an electromechanical testing machine with the screw axis coaxial to the pullout direction. Pullout testing was conducted with load and displacement data taken continuously. The peak load to failure was measured in newtons (N) and is reported as the pullout resistance (POR). After pullout, two revision strategies were tested in each vertebra. In Group-1, revision was performed with 4.0-mm C2-pCPSs. In Group-2, revision was performed with C2-pedicle bone-plastic combined with the use of a 4-mm C2-pCPSs. For the statistical analysis, the POR between screws was compared using absolute values (N) and the POR of the revision techniques normalized to that of the primary procedures (%).

RESULTS

The POR of primary 3.5-mm CPSs was 1,140.5 ± 539.6 N for Group-1 and 1,007.7 ± 362.5 N for Group-2; the difference was not significant. In the revision setting, the POR in Group-1 was 705.8 ± 449.1 N, representing a reduction of 38.1 ± 32.9 % compared with that of primary screw fixation. For Group-2, the POR was 875.3 ± 367.9 N, representing a reduction of 13.1 ± 23.4 %. A statistical analysis showed a significantly higher POR for Group-2 compared with Group-1 (p = 0.02). Although the statistics showed a significantly reduced POR for both revision strategies compared with primary fixation (p < 0.001/p = 0.001), the loss of POR (in %) in Group-1 was significantly higher compared with the loss in Group-2 (p = 0.04).

CONCLUSIONS

Using a larger-diameter screw combined with the application of a pedicle bone-plastic, the POR can be significantly increased compared with the use of only an increased screw diameter.

Percutaneous Pedicle Screw Fixation of a Hangman's Fracture Using Intraoperative, Full Rotation, Three-dimensional Image (O-arm)-based Navigation: A Technical Case Report

Surgical treatment of a hangman's fractures is technically demanding, even when using the standard open procedure. In this case report, a type II hangman's fracture was treated by percutaneous posterior screw fixation, without a midline incision, using intraoperative, full rotation, three-dimensional (3D) image (O-arm)-based navigation. A 48-year-old woman was injured in a motor vehicle accident and diagnosed with a unilateral hangman's fracture associated with subluxation of the C2 vertebral body on C3. After attaching the reference arc of the 3D-imaging system to the headholder, the cervical spine was screened using an O-arm without anatomical registration. Drilling and screw fixation were performed using a guide tube while referring to the reconstructed 3D-anatomical views. The operation was successfully completed without technical difficulties or neurovascular complications. This percutaneous procedure requires less dissection of normal tissue, which may allow earlier recovery. However, further validation of this procedure for its effectiveness and safety is required.

Radiation exposure during 3D fluoroscopy of the knee: an experimental study

PURPOSE

To measure the radiation exposure at the knee and surrounding area during the use of 3D fluoroscopy.

METHODS

An experimental study was conducted by using a human cadaveric knee as a focus point for the 3D fluoroscope. An isocentric C-arm fluoroscope machine was applied on the lateral side of the knee. The radiation dosage at the focus point and surrounding area was measured. The mean radiation exposure in each location was compared between low- and high-resolution scanning.

RESULTS

The mean radiation sustained at the focus point was 44.0 ± 5.6 μSv and 20.0 ± 1.0 μSv in high- and low-resolution scanning, respectively. Radiation exposure on the opposite side of the C-arm machine was found to be higher than that on the other locations with the same distance from the focus point. In low-resolution scanning, radiation could not be detected beyond 75 cm from the focus point at the proximal, distal and same side of the machine. Radiation could be measured at a distance of up to 1.25 m on the opposite side of the machine. In high-resolution scanning, radiation could be measured at a distance of up to 1 m at the proximal, distal and same side of the C-arm, but up to 1.5 m on the opposite side.

CONCLUSION

Radiation exposure during 3D fluoroscopy of the knee decreases with increasing distance from the focus point. A higher number of scans in the high-resolution mode causes greater radiation exposure. In isocentric 3D fluoroscopy of the knee, a safe zone is located at least 1.5 m away from the focus point.

Neurovascular complications of cervical pedicle screw fixation

We rarely use the cervical transpedicular fixation (CPF) technique in the neurosurgery departments of the authors' institutions because the pedicle is thin and there is a risk of neurovascular damage. In this study we investigated postoperative neurovascular injury caused by the transpedicular screws of 210 pedicles in 45 patients on whom we performed CPF for various cervical pathologies. Fixation was performed between C3 and C7, and the iliac crest and lamina were used as autografts for fusion. In 205 of 210 pedicles (97.6%), the screws were in the correct position, while a non-critical lateral orientation was detected in three pedicles (1.4%). Two screws (one in each of two patients) were positioned inappropriately (0.9%, Grade 3), unilaterally and directly in the vertebral foramen, as shown on postoperative CT scans; blood circulation was normal on angiography. The fusion rate was 100%. The average screw length used for C3 to C7 was 32 mm. The patients were followed up for an average of 35.7 months (range: 17-60 months). There was no morbidity or mortality in our study. We concluded that CPF provides very strong cervical spine fixation but also carries a risk of pedicle perforation without neurovascular injury. However, a free-hand technique performed by an experienced surgeon is acceptable for CPF for various cervical pathologies.

Complications of cervical pedicle screw fixation for nontraumatic lesions: a multicenter study of 84 patients

OBJECT

The cervical pedicle screw (PS) provides strong stabilization but poses a potential risk to the neurovascular system, which may be catastrophic. In particular, vertebrae with degenerative changes complicate the process of screw insertion, and PS misplacement and subsequent complications are more frequent. The purpose of this study was to evaluate the peri- and postoperative complications of PS fixation for nontraumatic lesions and to determine the risk factors of each complication.

METHODS

Eighty-four patients who underwent cervical PS fixation for nontraumatic lesions were independently reviewed to identify associated complications. The mean age of the patients was 60.1 years, and the mean follow-up period was 4.1 years (range 6-168 months). Pedicle screw malpositioning was classified on postoperative CT scans as Grade I (< 50% of the screw outside the pedicle) or Grade II (≥ 50% of the screw outside the pedicle). Risk factors of each complication were evaluated using a multivariate analysis.

RESULTS

Three hundred ninety cervical PSs and 24 lateral mass screws were inserted. The incidence of PS misplacement was 19.5% (76 screws); in terms of malpositioning, 60 screws (15.4%) were classified as Grade I and 16 (4.1%) as Grade II. In total, 33 complications were observed. These included postoperative neurological complications in 11 patients in whom there was no evidence of screw misplacement (C-5 palsy in 10 and C-7 palsy in 1), implant failure in 11 patients (screw loosening in 5, broken screws in 4, and loss of reduction in 2), complications directly attributable to screw insertion in 5 patients (nerve root injury by PS in 3 and vertebral artery injury in 2), and other complications in 6 patients (pseudarthrosis in 2, infection in 1, transient dyspnea in 1, transient dysphagia in 1, and adjacent-segment degeneration in 1). The multivariate analysis showed that a primary diagnosis of cerebral palsy was a risk factor for postoperative implant failure (HR 10.91, p = 0.03) and that the presence of preoperative cervical spinal instability was a risk factor for both Grade I and Grade II screw misplacement (RR 2.12, p = 0.03), while there were no statistically significant risk factors for postoperative neurological complications in the absence of evidence of screw misplacement or complications directly attributable to screw insertion.

CONCLUSIONS

In the present study, misplacement of cervical PSs and associated complications occurred more often than in previous studies. The rates of screw-related neurovascular complications and neurological deterioration unrelated to PSs were high. Insertion of a PS for nontraumatic lesions is surgically more challenging than that for trauma; consequently, experienced surgeons should use PS fixation for nontraumatic cervical lesions only after thorough preoperative evaluation of each patient's cervical anatomy and after considering the risk factors specified in the present study.

Cervical transpedicular fixation aided by biplanar flouroscopy

PURPOSE; To evaluate the accuracy of fluoroscopyassisted cervical transpedicular fixation in different pathologies.

METHODS

28 men and 17 women aged 34 to 65 (mean, 41) years underwent 210 one-stage cervical transpedicular fixations. The indications were trauma (n=35), degenerative disease leading to cervical spondylotic myelopathy (n=4), tumours (n=4), and Pott's disease (n=2). Regarding the 35 trauma patients, fractures were at C5-C6 (n=22), C4-C5 (n=8), and C3-C5 (n=5); 16 of them had dislocated vertebrae, of whom 13 had cervical disc herniation. Two of the patients with degenerative disease underwent additional laminectomy. Both anterior and posterior surgeries were performed for the 2 of the patients with tumours; all other patients underwent posterior surgery only. The length, diameters, and frontal, sagittal, and longitudinal angles of all pedicle screws were calculated. The dominant vertebral artery was detected using Doppler ultrasonography. Biplanar fluoroscopy was also used. Postoperatively, patients were allowed to mobilise at day 1; a collar was not used. The position of the pedicle screws was graded.

RESULTS

The mean operating time was 105 (range, 90-155) minutes. The mean follow-up period was 26 (range, 17-34) months. Of the 210 pedicles fixed, 192 (91%) were at the correct screw position (grade I), 16 (8%) were at an acceptable position (grade II), and 2 (1%) were completely perforated but without morbidity (grade III). The overall perforation rate was 9%. There were no neurovascular injuries or instrumentation-associated complications (failure of implant components, screw loosening, or lucent zone formation around the pedicle screws). The fusion rate was 100%.

CONCLUSION

Cervical transpedicular fixation provides strong stabilisation. With the aid of biplanar fluoroscopy, the risk of pedicle perforation was about 8%, but no neurovascular injury was ensued.

Multilevel decompressive laminectomy and transpedicular instrumented fusion for cervical spondylotic radiculopathy and myelopathy: A minimum follow-up of 3 years

Objective:

Cervical laminectomies with transpedicular insertion technique is known to be a biomechanically stronger method in cervical pathologies. However, its frequency of use is low in the routine practice, as the pedicle is thin and risk of neurovascular damage is high. In this study, we emphasize the results of cervical laminectomies with transpedicular fixation using fluoroscopy in degenerative cervical spine disorder.

Materials and Methods:

Postoperative malposition of the transpedicular screws of the 70 pedicles of the 10 patients we operated due to degenerative stenosis in the cervical region, were investigated. Fixation was performed between C3 and C7, and we used resected lamina bone chips for fusion. Clinical indicators included age, gender, neurologic status, surgical indication, and number of levels stabilized. Dominant vertebral artery of all the patients was evaluated with Doppler ultrasonography. Preoperative and postoperative Nurick grade of each patient was documented.

Results:

No patients experienced neurovascular injury as a result of pedicle screw placement. Two patients had screw malposition, which did not require reoperation due to minor breaking. Most patients had 32-mm screws placed. Postoperative computed tomography scanning showed no compromise of the foramen transversarium. A total of 70 pedicle screws were placed. Good bony fusion was observed in all patients. At follow-up, 9/10 (90%) patients had improved in their Nurick grades. The cases were followed-up for an average of 35.7 months (30–37 months).

Conclusions:

Use of the cervical pedicular fixation (CPF) provides a very strong three-column stabilization but also carries vascular injury without nerve damage. Laminectomies technique may reduce the risk of malposition due to visualization of the spinal canal. CPF can be performed in a one-stage posterior procedure. This technique yielded good fusion rate without complications and can be considered as a good alternative compared other techniques.

Efficacy and accuracy of a novel rapid prototyping drill template for cervical pedicle screw placement

OBJECTIVE

To develop and validate the efficacy and accuracy of a novel drill template for cervical pedicle instrumentation.

MATERIALS AND METHODS

A CT scan of the cervical vertebrae was performed, and a 3D model of the vertebrae was reconstructed using MIMICS 10.01 software. The 3D vertebral model was then exported in STL format, and opened in a workstation running UGS Imageware 12.0 software to determine the optimal pedicle screw size and orientation. A virtual navigational template was established according to the laminar anatomic trait, and physical navigational templates were manufactured using rapid prototyping. The navigational templates were used intraoperatively to assist in the placement of cervical pedicle screws.

RESULTS

In all, 84 pedicle screws were placed, and the accuracy of screw placement was confirmed with postoperative X-rays and CT scans. Eighty-two screws were rated as Grade 0, 2 as Grade 1, and no screws as Grade 2 or 3. Hence, safer screw positioning was accomplished with the drill template technique.

CONCLUSIONS

This study demonstrates a patient-specific template technique that is easy to use, can simplify the surgical act, and generates highly accurate cervical pedicle screw placement. The advantages of this technology over traditional techniques are that it enables planning of the screw trajectory to be completed prior to surgery, and that the screw can be sized to fit the patient's anatomy.

Accuracy of Image-Guided Pedicle Screw Placement Using Intraoperative Computed Tomography-Based Navigation With Automated Referencing, Part I: Cervicothoracic Spine

BACKGROUND:

Image-guided spinal instrumentation reduces the incidence of implant misplacement.

OBJECTIVE:

To assess the accuracy of intraoperative computed tomography (iCT)-based neuronavigation (iCT-N).

METHODS:

In 35 patients (age range, 18-87 years), a total of 248 pedicle screws were placed in the cervical (C1-C7) and upper and midthoracic (T1-T8) spine. An automated iCT registration sequence was used for multisegmental instrumentation, with the reference frame fixed to either a Mayfield head clamp and/or the most distal spinous process within the instrumentation. Pediculation was performed with navigated drill guides or Jamshidi cannulas. The angular deviation between navigated tool trajectory and final implant positions (evaluated on postinstrumentation iCT or postoperative CT scans) was calculated to assess the accuracy of iCT-N. Final screw positions were also graded according to established classification systems. Mean follow-up was 16.7 months.

RESULTS:

Clinically significant screw misplacement or iCT-N failure mandating conversion to conventional technique did not occur. A total of 71.4% of patients self-rated their outcome as excellent or good at 12 months; 99.3% of cervical screws were compliant with Neo classification grades 0 and 1 (grade 2, 0.7%), and neurovascular injury did not occur. In addition, 97.8% of thoracic pedicle screws were assigned grades I to III of the Heary classification, with 2.2% grade IV placement. Accuracy of iCT-N progressively deteriorated with increasing distance from the spinal reference clamp but allowed safe instrumentation of up to 10 segments.

CONCLUSION:

Image-guided spinal instrumentation using iCT-N with automated referencing allows safe, highly accurate multilevel instrumentation of the cervical and upper and midthoracic spine. In addition, iCT-N significantly reduces the need for reregistration in multilevel surgery.

Percutaneous instrumentation of the cervical and cervico-thoracic spine using pedicle screws: preliminary clinical results and analysis of accuracy

The pedicle screw instrumentation represents the most rigid construct of the cervical and cervicothoracic spine and in spite of the risks to neurovascular structures clinical relevant complications do not occur frequently. The steep angles of the cervical pedicles result in a wide surgical exposure with extensive muscular trauma. The objective of this study was the evaluation of the accuracy of cervical pedicle screw insertion through a minimally invasive technique to reduce access-related muscular trauma. Therefore, percutaneous transpedicular instrumentation of the cervical and cervicothoracic spine was performed in 15 patients using fluoroscopy. All instrumentations from C2 to Th4 were inserted bilaterally through 2 to 3-cm skin and fascia incisions even in multilevel procedures and the rods were placed by blunt insertion through the incision. Thin-cut CT scan was used postoperatively to analyze pedicle violations. 76.4% of 72 screws were placed accurately. Most pedicle perforations were seen laterally towards the vertebral artery. Critical breaches >2 mm or narrowing of the transversal foramen occurred in 12.5% of screws; however, no revision surgery for screw displacement was needed in the absence of clinical symptoms. No conversion from percutaneous to open surgery was necessary. It was concluded that percutaneous transpedicular instrumentation of the cervical spine is a surgically demanding technique and should be reserved for experienced spine surgeons. The indications are limited to instrumentation-only procedures or in combination with anterior treatment, but with the potential to minimize access-related morbidity.

Stimulus-evoked electromyography testing of percutaneous pedicle screws for the detection of pedicle breaches: a clinical study of 409 screws in 93 patients

Object

Percutaneous pedicle screws have recently become popularized for lumbar spinal fixation. However, successful anatomical hardware placement is highly dependent on intraoperative imaging. In traditional open surgery, stimulus-evoked electromyography (EMG) responses can be useful for detecting pedicle screw breaches. The use of insulated sleeves for percutaneous screws has allowed for EMG testing in minimally invasive surgery; however, no reports on the reliability of this testing modality have been published.

Methods

A total of 409 lumbar percutaneous pedicle screws were placed in 93 patients. Levels of instrumentation included L-1 (in 12 patients), L-2 (in 34), L-3 (in 44), L-4 (in 120), L-5 (in 142), and S-1 (in 57 patients). Intraoperative EMG stimulation thresholds were obtained using insulating sleeves over a metallic tap prior to final screw placement. Data were compared with postoperative fine-cut CT scans to assess pedicle screw placement. Data were collected prospectively and analyzed retrospectively.

Results

There were 5 pedicle breaches (3 medial and 2 lateral; 3 Grade 1 and 2 Grade 2 breaches) visualized on postoperative CT scans (1.2%). Two of these breaches were symptomatic. In 2 instances, intraoperative thresholds were the sole basis for screw trajectory readjustment, which resulted in proper placement on postoperative imaging. Thirty-five screw trajectories were associated with a threshold of less than 12 mA. However, all breaches were associated with thresholds of greater than 12 mA. Using thresholds below 12 mA as the indicator of a screw breach, this resulted in a sensitivity of 0.0, specificity of 90.3, positive predictive value of 0.0, and negative predictive value of 0.98. Utilizing a threshold of any decreased stimulus (< 20 mA) would have detected 60% of breaches, with a mean threshold of 16.25 mA.

Conclusions

While these data are limited by the low number of radiographic breaches, it appears that tap stimulation with an insulating sleeve may not be reliable for detecting low-grade radiographically breached pedicles using typical stimulation thresholds (< 12 mA). Imaging-based modalities remain more reliable for assessing percutaneous pedicle screw trajectories until more robust and sensitive electrophysiological testing methods can be devised.

Vertebral rotation during pedicle screw insertion in patients with cervical injury

BACKGROUND

Cervical pedicle screws, when misplaced, tend to perforate laterally. One of the reasons for lateral perforation is vertebral rotation during screw insertion. However, actual vertebral rotation during pedicle screw insertion is unknown. In this study, we measured vertebral rotation during pedicle screw insertion in patients with cervical injury.

METHODS

We inserted 76 pedicle screws into 38 vertebrae (C2 to C7) in 17 patients. All patients had some type of cervical injury. Screws were placed using intraoperative acquisition of data acquired with the isocentric C-arm fluoroscope (Iso-C3D) and computer navigation. We made screw holes using an image-guided awl, and we took images of cervical vertebrae in the neutral and rotational positions using navigation. Images of 76 insertions and rotational positions were taken while each cervical vertebra was under maximum stress at the time we were making the pedicle hole by awl.

RESULTS

Average cervical vertebra rotation was 10.6 degrees (range 6 to 17) at C2, 9.1 degrees (5 to 13) at C3, 7.8 degrees (6 to 9) at C4, 6.7 degrees (4 to 11) at C5, 4.9 degrees (2 to 8) at C6, and 2.8 degrees (0 to 4) at C7. Vertebrae in the upper and middle cervical spine rotated more than the lower cervical spine vertebrae. Of the 76 pedicle screws inserted into vertebrae between C2 and C7, 74 screws (97.4%) were classified as grade 1 (no pedicle perforation).

CONCLUSIONS

In this study, upper and middle cervical vertebrae in patients with neck injuries rotated more than the lower vertebrae. We should be especially careful of cervical rotation during screw insertion from C2 to C6, so as to prevent vertebral artery injury.

Image-guided placement of occipitocervical instrumentation using a reference arc attached to the headholder

OBJECTIVE

To develop a safe and accurate method of image-guided placement of instrumentation in the upper cervical spine and occiput in which the reference arc is fixed to the headholder.

METHODS

The authors describe a technique for placing screws at the occipital, C1, and C2 levels using 3-dimensional image guidance in which the reference arc is fixed to the headholder. Technical details are discussed as well as modifications to the technique to maximize navigation accuracy and decrease the need for re-registration. One of 2 paired systems, the BrainLAB Vector Vision system (BrainLAB Inc., Westchester, IL) used in conjunction with the Arcadis Orbic Isocentric C-arm (Siemens Medical Solutions, Erlangen, Germany) or the Stealth Treon system (Medtronic, Littleton, MA) paired with the O-arm (Medtronic), was used for image guidance in this study. A total of 18 patients had 82 screws placed at the occipital, C1, or C2 level using this technique. An independent radiologist interpreted postoperative computed tomographic scans of these patients and graded the screws for bony breach.

RESULTS

No complications resulted from the use of image guidance or from the placement of instrumentation. Postoperative computed tomography revealed 1 screw with a minimal breach of the outer lamina of C2. Another screw was replaced intraoperatively secondary to a minimal bony breach. No other bony breach occurred.

CONCLUSIONS

This technique allows safe and accurate placement of instrumentation in the posterior occipitocervical junction using 3-dimensional image guidance in which the reference arc is attached to the headholder.

Minimally Invasive Atlantoaxial Fusion

BACKGROUND

C1–C2 fusion has significantly advanced from predominantly wiring/cable modalities to more biomechanically stable screw-rod techniques. Minimally invasive surgical techniques represents the most recent modification of atlantoaxial fixation. The indications, rationale, and surgical technique of this novel procedure are described.

METHODS

Six patients requiring C1–C2 fusion (5 type II odontoid fractures and 1 os odontoideum) underwent minimally invasive C1–C2 fusion over a 2-year period. The cohort consisted of 5 men and 1 woman with a mean age of 51 years (age range, 39–64 y). All 6 patients underwent bilateral segmental atlantoaxial fixation using an expandable tubular retractor.

RESULTS

The mean follow-up time was 32 months (age range, 24–46 mo) There were no intraoperative complications, and the mean estimated blood loss was 100 mL. Solid fusion was achieved in all 6 patients, without pathological motion on dynamic studies. Postoperative computed tomographic images showed no hardware malposition in the scanned patients (4 of the 6 patients).

CONCLUSIONS

Placement of C1 and C2 instrumentation using minimally invasive techniques is technically feasible. Because the instrumentation and the means of obtaining arthrodesis do not differ substantively from the standard approach, we would not anticipate long-term results to be different from those of an open procedure, apart from the approach-related morbidity.