Lumbar and sacral pedicle screw placement using a template does not improve the midterm pain and disability outcome in comparison with free-hand method

Background

The free-hand technique carries a higher risk of pedicle weakening and neurovascular injuries in comparison with pedicle screw placement using a drill guide. Due to this evidence and because of some variances in the surgical method, different outcome can be expected. The objective of the study was to evaluate the disability, the back and leg pain before and at least 3 years after the surgery between examined groups.

Materials and methods

Eleven patients in drill guide and 13 in control group were randomly assigned for vertebral fusion in the lumbar and first sacral regions. Pre- and post-operative CT scans, Oswestry disability index (ODI) and visual analogue scale (VAS) for back and leg pain were taken. Post-operative evaluations of cortex perforation and statistical analysis between studied groups have been performed.

Results

Seventy-two screws were inserted in each group. All patients completed a 3-year follow-up. Comparing groups, there was no statistical significant difference in VAS and ODI before or after surgery. Cortex perforation incidence in drill guide group was 6 and in free-hand group 29 (p < 0.05). In each group, pain and disability were significantly lower as before the procedure.

Conclusions

The application of a drill guide template for pedicle screw placement is not more effective in reducing pain and disability after midterm follow-up in comparison with the free-hand technique. However, it reduces the cortex perforation incidence. Concerning this evidence, a drill guide is still an additional tool that could in the future potentially compete with other screw placement techniques.

     

Accuracy of thoracic pedicle screw placement in adolescent patients with severe spinal deformities: a retrospective study comparing drill guide template with free-hand technique

Purpose

Patients with severe spinal deformities often have small pedicle diameters, and pedicle dimensions vary between segments and individuals. Free-hand pedicle screw placement can be inaccurate. Individualized drill guide templates may be used, but the accuracy of pedicle screw placement in severe scoliosis remains unknown. The accuracy of drill guide templates and free-hand technique for the treatment of adolescent patients with severe idiopathic scoliosis are compared in this study.

Methods

This study included 37 adolescent patients (mean age 16.4 ± 1.3 years) with severe idiopathic scoliosis treated surgically at a single spine center between January 2014 and June 2017. Spinal deformities were corrected using posterior pedicle screw fixation. Patients in group I were treated with rapid prototype drill guide template technique (20 patients; 396 screws) and patients in group II were treated with free-hand technique (17 patients; 312 screws). Outcomes that included operative time, correction rate, and the incidence and distribution of screw misplacement were evaluated.

Results

Operative time in group I was 283 ± 22.7 min compared to 285 ± 25.8 min in group II (p = 0.89). The scoliosis correction rate was 55.0% in group I and 52.9% in group II (p = 0.33). Based on both axial and sagittal reconstruction images, the accuracy rate of pedicle screw placement was 96.7% in group I and 86.9% in group II (p = 0.000).

Conclusion

The drill guide template technique has potential to offer more accurate and thus safer placement of pedicle screws than free-hand technique in the treatment of severe scoliosis in adolescents.

     

Computed tomography assessment of lateral pedicle wall perforation by free-hand subaxial cervical pedicle screw placement

Purpose

To present the technique of free-hand subaxial cervical pedicle screw (CPS) placement without using intra-operative navigating devices, and to investigate the crucial factors for safe placement and avoidance of lateral pedicle wall perforation, by measuring and classifying perforations with postoperative computed tomography (CT) scan.

Summary of background data

The placement of CPS has generally been considered as technically demanding and associated with considerable lateral wall perforation rate. For surgeons without access to navigation systems, experience of safe free-hand technique for subaxial CPS placement is especially valuable.

Materials and methods

A total of 214 consecutive traumatic or degenerative patients with 1,024 CPS placement using the free-hand technique were enrolled. In the operative process, the lateral mass surface was decorticated. Then a small curette was used to identify the pedicle entrance by touching the cortical bone of the medial pedicle wall. It was crucial to keep the transverse angle and make appropriate adjustment with guidance of the resistance of the thick medial cortical bone. The hand drill should be redirected once soft tissue breach was palpated by a slim ball-tip prober. With proper trajectory, tapping, repeated palpation, the 26–30 mm screw could be placed. After the procedure, the transverse angle of CPS trajectory was measured, and perforation of the lateral wall was classified by CT scan: grade 1, perforation of pedicle wall by screw placement, with the external edge of screw deviating out of the lateral pedicle wall equal to or less than 2 mm and grade 2, critical perforation of pedicle wall by screw placement, large than 2 mm.

Results

A total of 129 screws (12.64 %) were demonstrated as lateral pedicle wall perforation, of which 101 screws (9.86 %) were classified as grade 1, whereas 28 screws (2.73 %) as grade 2. Among the segments involved, C3 showed an obviously higher perforating rate than other (P < 0.05). The difference between the anatomical pedicle transverse angle and the screw trajectory angle was higher in patients of grade 2 perforation than the others. In the 28 screws of grade 2 perforation verified by axial CT, 26 screws had been palpated as abnormal during operation. However, only 19 out of the 101 screws of grade 1 perforation had shown palpation alarming signs during operation. The average follow-up was 36.8 months (range 5–65 months). There was no symptom and sign of neurovascular injuries. Two screws (0.20 %) were broken, and one screw (0.10 %) loosen.

Conclusion

Placement of screw through a correct trajectory may lead to grade 1 perforation, which suggests transversal expansion and breakage of the thinner lateral cortex, probably caused by mismatching of the diameter of 3.5 mm screws and the tiny cancellous bone cavity of pedicle. Grade 1 perforation is deemed as relatively safe to the vertebral artery. Grade 2 perforation means obvious deviation of the trajectory angle of hand drill, which directly penetrates into the transverse foramen, and the risk of vertebral artery injury (VAI) or development of thrombi caused by the irregular blood flow would be much greater compared to grade 1 perforation. Moreover, there are two crucial maneuvers for increasing accuracy of screw placement: identifying the precise entry point using a curette or hand drill to touch the true entrance of the canal after decortication, and guiding CPS trajectory on axial plane by the resistant of thick medial wall.     

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

Purpose

To assess the accuracy of O-arm-navigation-based pedicle screw insertion in dystrophic scoliosis secondary to NF-1 and compare it with free-hand pedicle screw insertion technique.

Methods

32 patients with dystrophic NF-1-associated scoliosis were divided into two groups. A total of 92 pedicle screws were implanted in apical region (two vertebrae above and below the apex each) in 13 patients using O-arm-based navigation (O-arm group), and 121 screws were implanted in 19 patients using free-hand technique (free-hand group). The postoperative CT images were reviewed and analyzed for pedicle violation. The screw penetration was divided into four grades: grade 0 (ideal placement), grade 1 (penetration <2 mm), grade 2 (penetration between 2 and 4 mm), and grade 3 (penetration >4 mm).

Results

The accuracy rate of pedicle screw placement (grade 0, 1) was significantly higher in the O-arm group (79 %, 73/92) compared to 67 % (81/121) of the free-hand group (P = 0.045). Meanwhile, a significantly lower prevalence of grade 2–3 perforation was observed in the O-arm group (21 vs. 33 %, P < 0.05), and the incidence of medial perforation was significantly minimized by using O-arm navigation compared to free-hand technique (2 vs. 15 %, P < 0.01). Moreover, the implant density in apical region was significantly elevated by using O-arm navigation (58 vs. 42 %, P < 0.001).

Conclusion

We reported 79 % accuracy of O-arm-based pedicle screw placement in dystrophic NF-1-associated scoliosis. O-arm navigation system does facilitate pedicle screw insertion in dystrophic NF-1-associated scoliosis, demonstrating superiorities in the safety and accuracy of pedicle screw placement in comparison with free-hand technique.

     

A CT-based study investigating the relationship between pedicle screw placement and stimulation threshold of compound muscle action potentials measured by intraoperative neurophysiological monitoring

Purpose

Neurophysiological monitoring aims to improve the safety of pedicle screw placement, but few quantitative studies assess specificity and sensitivity. In this study, screw placement within the pedicle is measured (post-op CT scan, horizontal and vertical distance from the screw edge to the surface of the pedicle) and correlated with intraoperative neurophysiological stimulation thresholds.

Methods

A single surgeon placed 68 thoracic and 136 lumbar screws in 30 consecutive patients during instrumented fusion under EMG control. The female to male ratio was 1.6 and the average age was 61.3 years (SD 17.7). Radiological measurements, blinded to stimulation threshold, were done on reformatted CT reconstructions using OsiriX software. A standard deviation of the screw position of 2.8 mm was determined from pilot measurements, and a 1 mm of screw—pedicle edge distance was considered as a difference of interest (standardised difference of 0.35) leading to a power of the study of 75 % (significance level 0.05).

Results

Correct placement and stimulation thresholds above 10 mA were found in 71 % of screws. Twenty-two percent of screws caused cortical breach, 80 % of these had stimulation thresholds above 10 mA (sensitivity 20 %, specificity 90 %). True prediction of correct position of the screw was more frequent for lumbar than for thoracic screws.

Conclusion

A screw stimulation threshold of >10 mA does not indicate correct pedicle screw placement. A hypothesised gradual decrease of screw stimulation thresholds was not observed as screw placement approaches the nerve root. Aside from a robust threshold of 2 mA indicating direct contact with nervous tissue, a secondary threshold appears to depend on patients’ pathology and surgical conditions.     

An anatomic study on the placement of the second sacral screw and its clinical applications

Background

The fixation of lumbosacral and sacral pelvis can be performed on the ilium and the Second Sacrum Vertebrae (S2). Although several studies on the anatomical and biomechanical features of S2 screw fixation have been published, little clinical application has been reported, especially combination of anatomical investigation and clinical study. This study was performed to design and optimize the method of pedicle screw placement for S2.

Materials and methods

Fifteen adult dry sacrum specimens were prepared and truncated from the S1–S2 and S2–S3 vertebral fusion remnants, and the morphology of the S2 vertebral body was observed from this section. The intersection of the horizontal line through the lowest point of the inferior edge of the first posterior sacral foramen and the lateral sacral crest was the entry point (Point X). The screws were inserted anterolaterally or anteromedially at Point X in 10 cadavers, with all of the screws penetrating the sacrum. Finally, the S2 sacral screw fixation technique was applied to a total of 13 patients with lumbosacral lesions, and the clinical outcome was evaluated at a minimum follow-up of 1 year.

Results

Two S2 sacral screw placement methods were developed, i.e., the anterolateral and anteromedial insertions. Seven patients had complete preoperative, postoperative, and follow-up data. In all cases, the bilateral S2 screws were placed in good position and the fixation was firm. There was no surgical wound infection or internal fixation loosening. All the patients achieved partial bone graft healing, which was verified by computed tomography.

Conclusions

The intersection of the horizontal line through the lowest point of the inferior edge of the first posterior sacral foramen and the lateral sacral crest can be used as the entry point for S2 sacral screw fixation. The S2 pedicle screw fixation shows good clinical effectiveness and safety for stable reconstruction of lumbosacral lesions.     

Pedicle screw diameter selection for safe insertion in the thoracic spine

Objective

Many thoracic pedicles are too small for the safe acceptance of a transpedicular screw. However, few studies have so far reported on the methods to select a proper pedicle screw size and to confirm the morphologic changes for such a small thoracic spine pedicle. The objective of this work was to determine the potential limits of a pedicle screw diameter for transpedicular screw placement in the thoracic spine.

Methods

T2–T9 vertebrae from eleven patients that underwent posterior thoracic instrumentation with the use of fluoroscopically assisted insertion method were analyzed. The outcome measures were the pedicle widths, the gap between the outer pedicle width and the selected pedicle screw diameter, and the penetration length of the pedicle screws using computed tomography. The screws were distributed into two groups according to the pedicle width and screw diameter, and the screw perforation rate of the two groups was compared. The relationships of the gap and the distance of the screw penetration were compared and investigated in regard to the pedicle screw diameter selection.

Results

A total of 16 screws demonstrated a smaller diameter than the inner pedicle widths, while 22 screws had a larger diameter than the inner pedicle widths. One screw (6.3%) perforated the pedicle cortex in the smaller screw group, and twelve screws (54.5%) perforated the pedicle cortex in the larger screw group (P?=?0.006). A linear regression analysis in the larger screw group revealed that when the gap was less than 0.5?mm, a risk of a pedicle wall violation was observed.

Conclusions

When the screws with a larger diameter than the inner pedicle width are selected, the screw perforation rate increases. Therefore, the size of the screw diameter must be at least 0.5?mm less than the outer pedicle width to ensure safe transpedicular screw placement.     

Robot-assisted and fluoroscopy-guided pedicle screw placement: a systematic review

Purpose

At present, most spinal surgeons undertake pedicle screw implantation using either anatomical landmarks or C-arm fluoroscopy. Reported rates of screw malposition using these techniques vary considerably, though the evidence generally favors the use of image-guidance systems. A miniature spine-mounted robot has recently been developed to further improve the accuracy of pedicle screw placement. In this systematic review, we critically appraise the perceived benefits of robot-assisted pedicle screw placement compared to conventional fluoroscopy-guided technique.

Methods

The Cochrane Central Register of Controlled Trials, PubMed, and EMBASE databases were searched between January 2006 and January 2013 to identify relevant publications that (1) featured placement of pedicle screws, (2) compared robot-assisted and fluoroscopy-guided surgery, (3) assessed outcome in terms of pedicle screw position, and (4) present sufficient data in each arm to enable meaningful comparison (>10 pedicle screws in each study group).

Results

A total of 246 articles were retrieved, of which 5 articles met inclusion criteria, collectively reporting placement of 1,308 pedicle screws (729 robot-assisted, 579 fluoroscopy-guided). The findings of these studies are mixed, with limited higher level of evidence data favoring fluoroscopy-guided procedures, and remaining comparative studies supporting robot-assisted pedicle screw placement.

Conclusions

There is insufficient evidence to unequivocally recommend one surgical technique over the other. Given the high cost of robotic systems, and the high risk of spinal surgery, further high quality studies are required to address unresolved clinical equipoise in this field.     

Accuracy of patient-specific template-guided vs. free-hand fluoroscopically controlled pedicle screw placement in the thoracic and lumbar spine: a randomized cadaveric study

Purpose

Dorsal spinal instrumentation with pedicle screw constructs is considered the gold standard for numerous spinal pathologies. Screw misplacement is biomechanically disadvantageous and may create severe complications. The aim of this study was to assess the accuracy of patient-specific template-guided pedicle screw placement in the thoracic and lumbar spine compared to the free-hand technique with fluoroscopy.

Methods

Patient-specific targeting guides were used for pedicle screw placement from Th2–L5 in three cadaveric specimens by three surgeons with different experience levels. Instrumentation for each side and level was randomized (template-guided vs. free-hand). Accuracy was assessed by computed tomography (CT), considering perforations of <2 mm as acceptable (safe zone). Time efficiency, radiation exposure and dependencies on surgical experience were compared between the two techniques.

Results

96 screws were inserted with an equal distribution of 48 screws (50 %) in each group. 58 % (n = 28) of template-guided (without fluoroscopy) vs. 44 % (n = 21) of free-hand screws (with fluoroscopy) were fully contained within the pedicle (p = 0.153). 97.9 % (n = 47) of template-guided vs. 81.3 % (n = 39) of free-hand screws were within the 2 mm safe zone (p = 0.008). The mean time for instrumentation per level was 01:14 ± 00:37 for the template-guided vs. 01:40 ± 00:59 min for the free-hand technique (p = 0.013), respectively. Increased radiation exposure was highly associated with lesser experience of the surgeon with the free-hand technique.

Conclusions

In a cadaver model, template-guided pedicle screw placement is faster considering intraoperative instrumentation time, has a higher accuracy particularly in the thoracic spine and creates less intraoperative radiation exposure compared to the free-hand technique.

     

CT-navigation versus fluoroscopy-guided placement of pedicle screws at the thoracolumbar spine: single center experience of 4,500 screws

Purpose

Single center evaluation of the placement accuracy of thoracolumbar pedicle screws implanted either with fluoroscopy or under CT-navigation using 3D-reconstruction and intraoperative computed tomography control of the screw position. There is in fact a huge variation in the reported placement accuracy of pedicle screws, especially concerning the screw placement under conventional fluoroscopy most notably due to the lack of the definition of screw misplacement, combined with a potpourri of postinstrumentation evaluation methods.

Methods

The operation data of 1,006 patients operated on in our clinic between 1995 and 2005 is analyzed retrospectively. There were 2,422 screws placed with the help of CT-navigation compared to 2,002 screws placed under fluoroscopy. The postoperative computed tomography images were reviewed by a radiologist and an independent spine surgeon.

Results

In the lumbar spine, the placement accuracy was 96.4 % for CT-navigated screws and 93.9 % for pedicle screws placed under fluoroscopy, respectively. This difference in accuracy was statistically significant (Fishers Exact Test, p = 0.001). The difference in accuracy became more impressing in the thoracic spine, with a placement accuracy of 95.5 % in the CT-navigation group, compared to 79.0 % accuracy in the fluoroscopy group (p < 0.001).

Conclusion

This study underlines the relevance of CT-navigation-guided pedicle screw placement, especially when instrumentation of the middle and upper thoracic spine is carried out.     

A five-step remedial screw placement method to treat severe spinal deformity with free-hand transpedicular screw placement

Purpose

Severe spinal deformity is a complex morphological deformation that occurs and develops in three-dimensional space combined with abnormal development and morphology of anatomical structures, which presents great difficulties in the process of transpedicular screw placement. This study tried to explore the methods of transpedicular screw placement in surgical correction of severe spinal deformities.

Methods

Surgical corrections through posterior approach were performed in all the 76 cases (mean age 20.4 years). The averaging preoperative Cobb’s angle of scoliosis was 108.2° ± 33.6° (range 100°–170°). Among these patients, 34 cases were combined with kyphosis; the average Cobb’s angle of kyphosis was 77.3° (range 63°–160°). During operation, the screw tract was first established with the regular free-hand pedicle screw placement method. When this failed, in order to adjust the screw trajectory, a five-step remedial method was performed in the following order: (1) the“funnel” method; (2) exploring the pedicle exterior edge through the costotransverse joint; (3) exploring the superior and inferior edges of pedicle through the nerve root canal; (4) the vertebral plate fenestration; and (5) hemilaminectomy.

Results

Among all 1,472 screws planned to be placed for the patients, 1,210 (82.2 %) were successfully placed after using the regular method, and 262 (17.8 %) failed in this stage. After applying the five-step remedial method, 256 of the failed 262 screws were successfully placed. Among them, 176 screws (68.8 %) were successfully placed after Step 1, 44 (17.2 %) after Step 2, 21 (8.2 %) after Step 3, 12 (4.7 %) after Step 4, and 3 (1.2 %) after Step 5. In only six, pedicles screws could not be placed eventually. No nerve or blood vessel damages occurred in all cases. All final screw positions were validated by CT.

Conclusion

The five-step remedial method proved to be an effective supplementary method for transpedicular screw placement to treat patients with severe spinal deformities. The key points include a detailed preoperative plan, a meticulous hand drilling sensation, and an experienced probing technique for screw tract.     

Accuracy of percutaneous pedicle screws for thoracic and lumbar spine fractures: a prospective trial

Purpose

The percutaneous insertion technique requires surgical skill and experience. However, there have been few clinical reports evaluating the accuracy of minimally invasive pedicle screw placement using the conventional fluoroscopy method. The purpose of this study was to evaluate the accuracy of percutaneous pedicle screw placement in the treatment of thoracic and lumbar spine fractures using two-plane conventional fluoroscopy.

Methods

A prospective clinical trial was performed. A total of 502 percutaneous pedicle screws in 111 patients, all inserted with the assistance of conventional fluoroscopy, were evaluated. The safety and accuracy of pedicle screw placement were based on the evaluation of postoperative axial 3-mm slice computed tomography scans using the scoring system described by Zdichavsky et al. [Eur J Trauma 30:234–240, 2004; Eur J Trauma 30:241–247, 2004].

Results

427/502 pedicle screws (85 %) were classified as good and excellent concerning the best possible screw length and 494/502 (98 %) were found to have good or excellent position. One screw had to be revised due to medial position with a neurological deficit.

Conclusions

This study demonstrates the feasibility of placing percutaneous posterior thoracolumbar pedicle screws with the assistance of conventional fluoroscopy. Minimally invasive transpedicular instrumentation is an accurate, reliable and safe method to treat a variety of spinal disorders, including thoracic and lumbar spine fractures.     

Preliminary application of a multi-level 3D printing drill guide template for pedicle screw placement in severe and rigid scoliosis

Purpose

Accurate implantation of pedicle screw in spinal deformity correction surgeries is always challenging. We have developed a method of pedicle screw placement in severe and rigid scoliosis with a multi-level 3D printing drill guide template.

Methods

From November 2011 to March 2015, ten patients (4 males and 6 females) with severe and rigid scoliosis (Cobb angle >70° and flexibility <30%)were included. Multi-level template was designed and manufactured according to the part (two or three levels) of the most severe deformity. The drill template was then placed on the corresponding vertebral surface. Then, pedicle screws were carefully inserted along the trajectories. The other screws were placed in free hand. After surgery, the positions of the pedicle screws were evaluated by CT scan and graded for validation.

Results

48 screws were implanted using templates, other 104 screws in free hand, and the accuracies were 93.8 and 78.8%, respectively, with significant difference. The deformity correction ratio was 67.1 and 41.2% in coronal and sagittal plane post-operatively, respectively. The average operation time was 234.0 ± 34.1 min, and average blood loss was 557 ± 67.4 ml.

Conclusions

With the application of multi-level template, the incidence of cortex perforation in severe and rigid scoliosis decreased and this technology is, therefore, potentially applicable in clinical practice.

     

A customized modular reference array clamp for navigated spine surgery

Introduction

The current authors have developed a modular system of reference array fixation which is tailored specifically to the spinal level being operated upon. They believe that this system may further increase the precision and accuracy of pedicle screw placement.

Materials and methods

Two formalin-fixed whole body cadavers were used for this study. For cervical spine evaluation of the reference clamp, four odontoid screws (two per cadaver) for C1/C2-fusion and four lateral mass screws (two per cadaver) were implanted. Following navigated screw placement with 2D and 3D fluoroscopic verification, insertion of two lateral mass screws was performed. In the same way, lumbar and thoracic pedicle screws were implanted. Two pedicle screws were placed at two levels of the lumbar and two levels of the thoracic areas giving an overall of 16 screws implanted (8 cervical, 4 thoracic, and 4 lumbar). Postoperative evaluation involved comparison of postoperative 3D scans and preoperative planning images. A simple classification system was used for evaluation of any deviation from the planned trajectory.

Results

All pedicle screw placements were performed as planned without any technical problems. The reference array clamps remained in position at all the spinal levels at which they were employed with no loosening or displacement and no secondary damage to any of the spinous processes. Manual manipulation was performed but no displacement or slippage was observed. Image artefacts caused by the reference clamp were not significant as to obscure the area of interest. Both imaging modalities (Iso-C 3D and Vario 3D) generated sufficiently precise 3D images. There was no substantial difference in quality when those two systems were compared.

Discussion

Insufficient fixation of the reference clamp can lead to failure and complications. To date, no reference clamp systems have been developed specifically for navigated spine surgery.

Conclusions

Stable reference array fixation is a critical step in navigated surgery. To date, the same reference clamps have been applied to the spinal anatomy as have been developed originally for the appendicular skeleton. The current investigators have developed a novel modular clamp and have demonstrated its efficacy in a cadaveric model.     

Pedicle screw placement accuracy in thoracic and lumbar spinal surgery with a patient-matched targeting guide: a cadaveric study

Purpose

Pedicle screw placement is an increasingly common procedure for the correction of spine degenerative disease, deformity and trauma. However, screw placement is demanding, with complications resulting from inaccurate screw placement. While several different techniques have been developed to improve accuracy, they all have their limitations.

Methods

We examined the MySpine (Medacta International SA, Castel San Pietro, CH) patient-matched pedicle targeting guide in three cadaveric spine specimens operated on by three surgeons. A three-dimensional (3D) preoperative plan was constructed from spinal computed tomography scans, from which individualised guides were developed for the placement of Medacta Unconstrained Screw Technology pedicle screws. Following screw placement, the 3D positioning of the screws was compared to the preoperative plan against a series of pre-defined criteria.

Results

Of 46 inserted screws eligible for assessment, 91.3 % were fully inside the pedicle. There were no cases of Grade B (2–4 mm) or C (>4 mm) pedicle perforation. The mean deviation between the planned and actual screw position at the midpoint of the pedicle was 0.70 mm, the mean horizontal deviation was 0.60 mm and the mean vertical deviation was 0.77 mm. The mean angular deviation in the sagittal plane was 1.74°, versus 1.32° in the transverse plane. The mean deviation in screw depth was 1.55 mm. On all measures, the accuracy of screw placement was within the predefined criteria.

Conclusions

Our cadaver study indicates that pedicle screw placement with the system is accurate and should be investigated in larger in vitro and in vivo studies.

     

Computer tomography assessment of pedicle screw placement in thoracic spine: comparison between free hand and a generic 3D-based navigation techniques

Introduction

Although pedicle screw fixation is a well-established technique for the lumbar spine, screw placement in the thoracic spine is more challenging because of the smaller pedicle size and more complex 3D anatomy. The intraoperative use of image guidance devices may allow surgeons a safer, more accurate method for placing thoracic pedicle screws while limiting radiation exposure. This generic 3D imaging technique is a new generation intraoperative CT imaging system designed without compromise to address the needs of a modern OR.

Aim

The aim of our study was to check the accuracy of this generic 3D navigated pedicle screw implants in comparison to free hand technique described by Roy-Camille at the thoracic spine using CT scans.

Material and methods

The material of this study was divided into two groups: free hand group (group I) (18 patients; 108 screws) and 3D group (27 patients; 100 screws). The patients were operated upon from January 2009 to March 2010. Screw implantation was performed during internal fixation for fractures, tumors, and spondylodiscitis of the thoracic spine as well as for degenerative lumbar scoliosis.

Results

The accuracy rate in our work was 89.8 % in the free hand group compared to 98 % in the generic 3D navigated group.

Conclusion

In conclusion, 3D navigation-assisted pedicle screw placement is superior to free hand technique in the thoracic spine.     

CT accuracy of percutaneous versus open pedicle screw techniques: a series of 1609 screws

Introduction

Traditional open exposure for posterior instrumentation requires significant soft tissue mobilization and causes significant blood loss and increased recovery time. Mal-placed screws can injure nerve roots, the spinal cord, viscera, vasculature and the cardiopulmonary system. Placement of pedicle screws using a minimally invasive technique can decrease bleeding risk, damage to soft tissues, and post-operative pain. The purpose of this study is to compare the radiographic accuracy of open free-hand versus percutaneous technique for pedicle screw placement.

Methods

Consecutive patients undergoing thoracolumbar surgery from September 2006 to October 2011 with post-operative CT imaging were included in this study. Three-dimensional screw positioning within the pedicle and the vertebral body was assessed on CT. The magnitude and location of violations were measured and recorded. Facet breaches at the cephalad and caudad ends of the construct were documented and graded.

Results

Two-hundred and twenty-three patients met the inclusion criteria for a total of 1609 pedicle screws. Seven-hundred and twenty-four screws were placed using a standard open free-hand technique and 885 were placed percutaneously. There was a significant difference in overall pedicle breach rates: 7.5 % for open and 4.7 % for percutaneous techniques. The magnitude of breach was greater for the percutaneous technique compared to the open technique: 5.4 versus 3.7 mm, respectively. The difference in vertebral body breaches was also significant: 11.3 % for open and 3.6 % for percutaneous. The rates of facet breach did not significantly differ.

Discussion and conclusion

This is the largest series comparing the accuracy of percutaneous to open pedicle screw placement. The rates of pedicle, vertebral body, and facets breaches in the percutaneous group were similar to the rates in the open technique group as well as rates reported in the literature. This demonstrates that the percutaneous technique described here is an accurate alternative to standard open free-hand technique.