Are We Underestimating the Significance of Pedicle Screw Misplacement?

Precision and effort in robot-assisted placement of pedicle screws compared to standard surgical navigation

Aim was to compare image-guided navigation with a robot-assisted solution for performing MISS regarding precision, required time and subjective aspects. 90 pedicles were instrumented on two torsos, half with navigation, half robot-assisted. Precision analysis between both solutions didn't show a significant difference. Time measurement showed a significantly longer duration per wire for the robot-arm on the first torso and a not significant longer duration on the second torso, where a significant reduction in the mean duration was shown. There was no significant difference in the subjective impressions comparing navigation and robot except the possibility to change the procedure. Precision of both methods is suitable for clinical use. A time advantage using the robot-arm couldn't be demonstrated in the present study. A significant learning curve was shown, so a reduction in the longer duration on the robot can be expected. Further studies in clinical use are necessary.

The Influence of Increased Pedicle Screw Diameter and Thicker Rods on Surgical Results in Adolescents Undergoing Posterior Spinal Fusion for Idiopathic Scoliosis

Background: Modern surgical techniques allow for the correction of spinal deformity, stopping its progression and improving pain relief and social and physical functioning. These instruments have different implant designs, screws, and rod diameters and can be composed of different metal alloys with different hardnesses, which can have a significant impact on the effect of correcting spinal deformities. We designed a retrospective cohort study based on the same surgical technique and spine system using different implant sizes, and compared the results across them. Methods: This is a retrospective review of adolescent idiopathic scoliosis (AIS) patients who underwent posterior spinal fusion (PSF) between 2016 and 2022 with a minimum two-year follow-up (FU) using two spinal implant systems: 5.5 and 6.0 mm diameter screws with double 5.5 mm titanium rods (Group 1 (G1)), and 6.0 and 6.5 mm diameter pedicle screws with double 6.0 mm cobalt-chromium rods (Group 2 (G2)). The evaluated data were as follows: preoperative personal data, radiographic outcomes, complications, and health-related quality of life questionnaire (HRQoL). The parameters were reviewed preoperatively, after the final fusion, and during the FU. Results: The mean age of all 260 patients at surgery was 14.8 years. The average BMI was also similar in both groups and was noted as 21. The mean levels of fusion and screw density were similar in both groups. The mean preoperative major curves (MCs) were 57.6° and 62.5° in G1 and G2, respectively. The mean flexibility of the curves was noted as 35% in G1 and 33% in G2. After definitive surgery, the mean percentage correction of the MC was better in G2 vs. G1, with 74.5% vs. 69.8%, respectively (p < 0.001). At the final FU, the average loss of correction was 5.9° for G1 and 3.2° for G2 (p < 0.001). The mean preoperative (TK) thoracic kyphosis (T2-T5) was 12.2° in G1 and 10.8° in G2. It was corrected to 15.2° in G1 and to 13° in G2. At the FFU, we noted a significant difference in the TK (T2-T5) between the groups, with 16.7° vs. 9.6° for G1 vs. G2, respectively (p < 0.001). Statistical significance was observed between the preoperative sagittal balance and the final follow-up for both groups (p < 0.001). Conclusions: AIS patients surgically treated with screws with a larger diameter and thicker and stiffer rods showed greater correction and postoperative thoracic kyphosis without implant failure. The complication rates, implant density, and clinical outcomes remained similar. The radiographic benefits reported in this cohort study suggest that large-sized screws and stiffer rods for the correction of pediatric spinal deformities are safe and very effective.

Usefulness of the spectral shaping dual-source computed tomography imaging technique in posterior corrective fusion for adolescent idiopathic scoliosis

PURPOSE

Since childhood exposure to radiation has been demonstrated to increase cancer risk with increase in radiation dose, reduced radiation exposure during computed tomography (CT) evaluation is desired for adolescent idiopathic scoliosis (AIS). Therefore, this retrospective study aimed to investigate the radiation dose of dual-source CT using a spectral shaping technique and the accuracy of the thoracic pedicle screw (TPS) placement for posterior spinal fusion (PSF) in patients with AIS.

METHODS

Fifty-nine female patients with thoracic AIS who underwent PSF using CT-guided TPSs were included and divided into two groups comprised of 23 patients who underwent dual-source CT (DSCT) with a tin filter (DSCT group) and 36 who underwent conventional multislice CT (MSCT group). We assessed the CT radiation dose using the CT dose index (CTDIvol), effective dose (ED), and accuracy of TPS insertion according to the established Neo's classification.

RESULTS

The DSCT and MSCT groups differed significantly (p < 0.001) in the mean CTDIvol (0.76 vs. 3.31 mGy, respectively) and ED (0.77 vs. 3.47 mSv, respectively). Although the correction rate of the main thoracic curve in the DSCT group was lower (65.7% vs. 71.2%) (p = 0.0126), the TPS accuracy (Grades 0-1) was similar in both groups (381 screws [88.8%] vs. 600 screws [88.4%], respectively) (p = 0.8133). No patient required replacement of malpositioned screws.

CONCLUSION

Spectral shaping DSCT with a tube-based tin filter allowed a 75% radiation dose reduction while achieving TPS insertion accuracy similar to procedures based on conventional CT without spectral shaping.

3D printed pedicle screw guides reduce the rate of intraoperative screw revision in adolescent idiopathic scoliosis surgery

BACKGROUND CONTEXT

Pedicle screw fixation has become common in the treatment of adolescent idiopathic scoliosis (AIS). Malpositioned pedicle screws have significant complications and identifying surgical techniques to optimize screw placement accuracy is imperative.

PURPOSE

To compare the rate of intraoperative revision, replacement, or removal of pedicle screws placed utilizing 3D printed guides compared with pedicle screws placed utilizing a freehand technique.

STUDY DESIGN/SETTING

Retrospective cohort study/single academic center.

PATIENT SAMPLE

Thirty-two patients aged 10 to 18 with AIS.

OUTCOME MEASURES

Revision rate of pedicle screws and operative time between groups.

METHODS

A retrospective study was performed on patients 10 to 18 years of age who underwent posterior spinal instrumented fusion for AIS from February 2021 to July 2022. The study received an IRB exemption. Patient demographics, intraoperative measures, and outcome variables were recorded. Intraoperatively, all patients underwent a 3-dimensional fluoroscopic "check scan," which included axial, sagittal, and coronal images, to assess for screw accuracy. A secondary outcome of operative time was compared between groups. The p-values <.05 were considered significant.

RESULTS

A total of 32 patients were included in this study. There were 17 cases in the 3D guided and 15 cases in fluoroscopy-guided freehand cohort. There was a total of 254 pedicle screws using 3D guides and 402 screws using freehand technique. Between cohorts, there were no significant differences in a number of levels fused (p=.54) or length of surgery (p=.36). The total revision rate of 3D guided screw placement was 5.5% and that of the freehand technique was 8.5%. The freehand screw placement group had significantly higher revision rates per vertebral level compared with 3D guided (p=.0096). Notably, 3D printed guides had fewer screws that were removed/revised for being too anterior (7.1%) compared with freehand (23.5%). Surgical time was not significantly different between the 3D guided and freehand cohort (p=.35).

CONCLUSIONS

3D printed guides reduce intraoperative revision rate compared with freehand techniques. Total operative time is comparable to freehand technique.

Effect of Pedicle Screw Size on Surgical Outcomes Following Surgery for 412 Adolescent Idiopathic Scoliosis Patients

STUDY DESIGN

Retrospective Review.

OBJECTIVE

The objective of this study was to determine differences in surgical and post-operative outcomes in AIS patients undergoing spinal deformity correction surgery using standard or large pedicle screw size.

SUMMARY OF BACKGROUND

Use of pedicle screw fixation in spinal deformity correction surgery is considered safe and effective. Still, the small size of the pedicle and the complex 3D anatomy of the thoracic spine makes screw placement challenging, with improper pedicle screw fixation leading to catastrophic complications including injuries to nerve roots, spinal cord, and major vessels. Thus, insertion of larger diameter screw sizes has raised concerns amongst surgeons, especially in the pediatric population.

MATERIALS AND METHODS

AIS patients undergoing PSF between 2013 and 2019 were included. Demographic, radiographic, and operative outcomes collected. Patients in the large screw size group (GpI) received 6.5 mm diameter screw sizes at all levels while standard screw size group (GpII) received 5.0 to 5.5 mm diameter screw sizes at all levels. Kruskall-Wallis and Fisher's exact test performed for continuous and categorical variables respectively.Subanalyses included (1) screw accuracy in patients with available CT scans, (2) stratified analysis of large- and standard-screw patients with ≥60% flexibility rate, (3) stratified analysis of large- and standard-screw patients with <60% flexibility rate, and (4) matched analysis of large- and standard-screw patients by surgeon and year of surgery.

RESULTS

GpI patients experienced significantly higher overall curve correction ( P <0.001), with 87.6% experiencing at least one grade reduction of apical vertebral rotation from preoperative to postoperative visit( P =0.008).Patients with larger screws displayed higher postoperative kyphosis. No patient experienced medial breaching.

CONCLUSION

Large screw sizes have similar safety profiles to standard screws without negatively impacting surgical and perioperative outcomes in AIS patients undergoing PSF. Additionally, coronal, sagittal, and rotational correction is superior for larger-diameter screws in AIS patients.

Clinical Outcomes of Robotic Versus Freehand Pedicle Screw Placement After One-to Three-Level Lumbar Fusion

STUDY DESIGN

Retrospective cohort study.

OBJECTIVES

The purpose of this study is to compare patient-reported outcome measures (PROMs) for patients undergoing one-to three-level lumbar fusion using robotically assisted vs freehand pedicle screw placement.

METHODS

Patients who underwent either robotically assisted or freehand pedicle screw placement for one-to three-level lumbar fusion surgery from January 1, 2014 to August 31, 2020 at a single academic institution were identified. Propensity score matching was performed based on demographic variables. Clinical and surgical outcomes were compared between groups. Recovery Ratios (RR) and the proportion of patients achieving the minimally clinically important difference (%MCID) were calculated for Oswestry Disability Index, PCS-12, MCS-12, VAS Back, and VAS Leg at 1 year. Surgical outcomes included complication and revision rates.

RESULTS

A total of 262 patients were included in the study (85 robotic and 177 freehand). No significant differences were found in ΔPROM scores, RR, or MCID between patients who underwent robotically assisted vs freehand screw placement. The rates of revision (1.70% freehand vs 1.18% robotic, P = 1.000) and complications (.57% freehand vs 1.18% robotic, P = .546) were not found to be statically different between the 2 groups. Controlling for demographic factors, procedure type (robotic vs freehand) did not emerge as a significant predictor of ΔPROM scores on multivariate linear regression analysis.

CONCLUSIONS

Robotically assisted pedicle screw placement did not result in significantly improved clinical or surgical outcomes compared to conventional freehand screw placement for patients undergoing one-to three-level lumbar fusion.

The Role of 3D Printing in Treatment Planning of Spine and Sacral Tumors

Three-dimensional (3D) printing technology has proven to have many advantages in spine and sacrum surgery. 3D printing allows the manufacturing of life-size patient-specific anatomic and pathologic models to improve preoperative understanding of patient anatomy and pathology. Additionally, virtual surgical planning using medical computer-aided design software has enabled surgeons to create patient-specific surgical plans and simulate procedures in a virtual environment. This has resulted in reduced operative times, decreased complications, and improved patient outcomes. Combined with new surgical techniques, 3D-printed custom medical devices and instruments using titanium and biocompatible resins and polyamides have allowed innovative reconstructions.

Accuracy and Safety of Pedicle Screw Placement for Treating Adolescent Idiopathic Scoliosis: A Narrative Review Comparing Available Techniques

Posterior spinal fusion and segmental spinal instrumentation using pedicle screws (PS) is the most used procedure to correct adolescent idiopathic scoliosis. Computed navigation, robotic navigation, and patient-specific drill templates are available, besides the first described free-hand technique. None of these techniques are recognized as the gold standard. This review compares the PS placement accuracy and misplacement-related complication rates achieved with the techniques mentioned above. It further reports PS accuracy classifications and anatomic PS misplacement risk factors. The literature suggests a higher PS placement accuracy for robotic relative to computed navigation and for the latter relative to the free-hand technique (misplacement rates: 0.4-7.2% versus 1.9-11% versus 1.5-50.7%) using variable accuracy classifications. The reported PS-misplacement-related complication rates are, however, uniformly low (0-1.4%) for every technique, while robotic and computed navigation induce a roughly fourfold increase in the patient's intraoperative radiation exposure relative to the free-hand technique with fluoroscopic implant positioning control. The authors, therefore, recommend dedicating robotic and computed navigation for complex deformities or revisions with altered landmarks, underline the need for a generally accepted PS accuracy classification, and advise against PS placement in grade 4 pedicles yielding higher misplacement rates (22.2-31.5%).

Metal-Free Cortico-Pedicular Device for Supplemental Fixation in Lumbar Interbody Fusion

OBJECTIVE

Pedicle screw fixation is a commonly utilized adjunct for lumbar interbody fusion, yet risks include screw malposition, pullout, loosening, neurovascular injury, and stress transfers leading to adjacent segment degeneration. This report describes the preclinical and initial clinical results of a minimally invasive, metal-free cortico-pedicular fixation device used for supplemental posterior fixation in lumbar interbody fusion.

METHODS

Safety of arcuate tunnel creation was evaluated in cadaveric lumbar (L1-S1) specimens. A finite element analysis study evaluated clinical stability of the device to pedicular screw-rod fixation at L4-L5. Preliminary clinical results were assessed by analysis of Manufacturer and User Facility Device Experience database complications, and 6-month outcomes in 13 patients treated with the device.

RESULTS

Among 35 curved drill holes in 5 lumbar specimens, no breaches of the anterior cortex were identified. The mean minimum distance from the anterior surface of the hole to the spinal canal ranged from 5.1 mm at L1-L2 to 9.8 mm at L5-S1. In the finite element analysis study, the polyetheretherketone strap provided comparable clinical stability and reduced anterior stress shielding compared to the conventional screw-rod construct. The Manufacturer and User Facility Device Experience database identified 1 device fracture with no clinical sequelae among 227 procedures. Initial clinical experience showed a 53% decrease in pain severity (P = 0.009), a 50% decrease in Oswestry Disability Index (P < 0.001), and no device-related complications.

CONCLUSIONS

Cortico-pedicular fixation is a safe and reproducible procedure that may address limitations of pedicle screw fixation. Longer term clinical data in large clinical studies are recommended to confirm these promising early results.

Characteristics of pedicle screw misplacement using freehand technique in degenerative scoliosis surgery

PURPOSE

This study aimed to estimate the accuracy of pedicle screw (PS) placement in degenerative scoliosis surgery, characterize a patient population with PS misplacement, and analyze the association between misplaced PS vector and lumbar coronal curve.

METHODS

In this study, 122 patients (average age 68.6 years), who underwent corrective and decompression surgery, were selected retrospectively. PS accuracy was evaluated in the thoracic to lumbar spine. We identified characteristics of misplacement in each patient. Screw positions were categorized into grade A, entirely in the pedicle; grade B, < 2 mm breach; grade C, 2-4 mm breach; and grade D, > 4 mm breach using postoperative computed tomography.

RESULTS

The mean preoperative lumbar coronal curve was 32.3 ± 18.4°, and the number of fused vertebrae was 8.9 ± 2.8. A total of 2032 PS were categorized as follows: grade A, 1897 PS (93.3%); grade B, 67 (3.3%); grade C, 26 (1.3%); and grade D, 43 (2.1%). One PS (grade D), inserted at T5, needed surgery for removal due to neurological deficit. The misplacement group (grades C and D) had a significantly stronger lumbar coronal curve and apical vertebral rotation than the accuracy group (grades A and B). Misplaced PS vector (direction and degree) was significantly correlated with inserted vertebral rotation. Grade D misplacement was distributed mainly around the transitional vertebra of the lumbar curve.

CONCLUSIONS

The accuracy of PS insertion in the thoracic to lumbar spine was high in DS surgery, but the need for care was highlighted in the transitional vertebra.

Robotic and navigated pedicle screws are safer and more accurate than fluoroscopic freehand screws: a systematic review and meta-analysis

BACKGROUND CONTEXT

Navigated and robotic pedicle screw placement systems have been developed to improve the accuracy of screw placement. However, the literature comparing the safety and accuracy of robotic and navigated screw placement with fluoroscopic freehand screw placement in thoracolumbar spine surgery has been limited.

PURPOSE

To perform a systematic review and meta-analysis of randomized control trials that compared the accuracy and safety profiles of robotic and navigated pedicle screws with fluoroscopic freehand pedicle screws.

STUDY DESIGN/SETTING

Systematic review and meta-analysis PATIENT SAMPLE: Only randomized controlled trials comparing robotic-assisted or navigated pedicle screws placement with freehand pedicle screw placement in the thoracolumbar spine were included.

OUTCOME MEASURES

Odds ratio (OR) estimates for screw accuracy according to the Gertzbein-Robbins scale and relative risk (RR) for various surgical complications.

METHODS

We systematically searched PubMed and EMBASE for English-language studies from inception through April 7, 2022, including references of eligible articles. The search was conducted according to PRISMA guidelines. Two reviewers conducted a full abstraction of all data, and one reviewer verified accuracy. Information was extracted on study design, quality, bias, participants, and risk estimates. Data and estimates were pooled using the Mantel-Haenszel method for random-effects meta-analysis.

RESULTS

A total of 14 papers encompassing 12 randomized controlled trials were identified (n=892 patients, 4,046 screws). The pooled analysis demonstrated that robotic and navigated pedicle screw placement techniques were associated with higher odds of screw accuracy (OR 2.66, 95% CI 1.24-5.72, p=.01). Robotic and navigated screw placement was associated with a lower risk of facet joint violations (RR 0.09, 95% CI 0.02-0.38, p<.01) and major complications (RR 0.31, 95% CI 0.11-0.84, p=.02). There were no observed differences between groups in nerve root injury (RR 0.50, 95% CI 0.11-2.30, p=.37), or return to operating room for screw revision (RR 0.28, 95% CI 0.07-1.13, p=.07).

CONCLUSIONS

These estimates suggest that robotic and navigated screw placement techniques are associated with higher odds of screw accuracy and superior safety profile compared with fluoroscopic freehand techniques. Additional randomized controlled trials will be needed to further validate these findings.

Percutaneous Versus Open Pedicle Screw Fixation for Pyogenic Spondylodiscitis of the Thoracic and Lumbar Spine: Systematic Review and Meta-Analysis

STUDY DESIGN

A systematic review and meta-analysis.

OBJECTIVE

This meta-analysis aimed to compare percutaneous (PPS) versus open pedicle screw (OPS) fixation for treatment of thoracic and lumbar spondylodiscitis.

SUMMARY OF BACKGROUND DATA

Pyogenic spondylodiscitis of the thoracic and lumbar spine can produce instability, deformity, and/or neurological compromise. When medical treatment is unsuccessful, surgical treatment is indicated, with the conventional open approach the usual standard of care. However, percutaneous techniques can be advantageous in medically vulnerable patients.

MATERIALS AND METHODS

A literature search was performed using the PubMed, Web of Science, and Scopus databases, looking for comparative articles on pyogenic spondylodiscitis requiring surgical stabilization with pedicle screws. This systematic review is reported according to PRISMA guidelines.

RESULTS

From 215 articles initially identified, 7 retrospective studies were analyzed, encapsulating an overall sample of 722 patients: 405 male (56.1%) and 317 female (43.9%). The treatment modality was PPS fixation in 342 patients (47.4%) and OPS fixation in 380 (52.6%). For PPS, operating time was 29.75 minutes ( P <0.0001), blood loss 390.18 mL ( P <0.00001), postoperative pain 1.54 points ( P <0.00001), and length of stay 4.49 days ( P =0.001) less than with OPS fixation, and wound infection 7.2% ( P =0.003) less frequent. No difference in screw misplacement ( P =0.94) or loosening ( P =0.33) rates was observed.

CONCLUSION

Employing PPS fixation to treat pyogenic spondylodiscitis of the thoracic and lumbar spine is associated with significantly reduced operating time, blood loss, postoperative pain, length of stay, and rates of wound infection than OPS fixation, with no difference between the 2 treatments in rates of screw misplacement or screw loosening.

Pedicle screw placement safety with the aid of patient-specific guides in a case series of patients with thoracic scoliosis

PURPOSE

Pedicle screw (PS) placement in thoracic scoliotic deformities can be challenging due to altered vertebral anatomy; malposition can result in severe functional disability or inferior construct stability. Three-dimensional (3D) printed patient-specific guides (PSGs) have been recently used to supplement other PS placement techniques. We conducted a single-center, retrospective observational study to assess the accuracy of PS placement using PSGs in a consecutive case series of pediatric and adult patients with thoracic scoliosis.

METHODS

We analyzed the data of patients with thoracic scoliosis who underwent PS placement using 3D-printed PSG as a vertebral cannulation aid between June 2013 and July 2018. PS positions were determined via Gertzbein-Robbins (GR) and Heary classifications on computed tomography images. We determined the concordance of actual and preoperatively planned PS positions and defined the technique learning curve using a receiver-operating characteristic (ROC) curve.

RESULTS

We performed 362 thoracic PS placement procedures in 39 consecutive patients. We classified 352 (97.2%), 2 (0.6%), and 8 (2.2%) screws as GR grades 0 (optimal placement), I, and II, respectively. The average instrumented PS entry point offsets on the X- and Y-axes were both 0.8 mm, and the average differences in trajectory between the planned and the actual screw placements on the oblique sagittal and oblique transverse planes were 2.0° and 2.4°, respectively. The learning process was ongoing until the first 12 PSs were placed.

CONCLUSIONS

The accuracy of PS placement using patient-specific 3D templates in our case series exceeds the accuracies of established thoracic PS placement techniques.

Reoperation for Misplaced Pedicle Screws: A Multicenter Retrospective Study

STUDY DESIGN

A multicenter retrospective analysis.

OBJECTIVE

This study aims to investigate reoperation of misplaced pedicle screws (MPSs) after posterior spinal fusion (PSF), focusing on neurological complications.

SUMMARY OF BACKGROUND DATA

The management strategy for MPSs and the clinical results after reoperation are poorly defined.

MATERIALS AND METHODS

Subjects were 10,754 patients (73,777 pedicle screws) who underwent PSF at 11 hospitals over 15 years. The total number of reoperations for MPS and patient clinical data were obtained from medical records at each hospital.

RESULTS

The rate of reoperation for screw misplacement per screw was 0.17%. A total of 69 patients (mean age, 67.4±16.5 yr) underwent reoperation because of 82 MPS. Reasons for reoperation were neurological symptoms (58 patients), contact with vessels (5), suboptimal bone purchase (4), and misplacement recognized during operation (2). Neurological symptoms were the major reason for reoperation in cervical (5/5 screws, 100%) and lumbo-sacral (60/67 screws, 89.6%) regions. Contact with vessels was the major reason for reoperation in the thoracic spine (6/10 screws, 60.0%). We further evaluated 60 MPSs in the lumbo-sacrum necessitating reoperation because of neurological symptoms. The majority of MPSs necessitating reoperation were placed in the lower lumbar spine (43/60 screws, 71.7%). The mean pedicle breach tended to be larger in the incomplete recovery group than in the complete recovery group (6.8±2.4 vs . 5.9±2.2 mm, P =0.146), and the cutoff value resulting in incomplete resolution was 5.0 mm. Multivariate analysis revealed that medial-caudal breaches ( vs . medial breach, odds ratio: 25.8, 95% confidence interval: 2.58-258, P =0.0057) and sensory and motor disturbances ( vs . sensory only, odds ratio: 8.57, 95% confidence interval: 1.30-56.6, P =0.026) were significant factors for incomplete resolution of neurological symptoms.

CONCLUSIONS

After reoperation, 70.1% of the patients achieved complete resolution of neurological symptoms. Factors associated with residual neurological symptoms included sensory and motor disturbance, medial-caudal breach, and larger pedicle breach (>5 mm).

The effect of hydroxyapatite on titanium pedicle screw resistance: an electrical model

BACKGROUND CONTEXT

Intraoperative detection of a pedicle wall breach implicitly reduces surgical risk, but the reliability of intraoperative neuromonitoring has been contested. Hydroxyapatite (HA) has been promulgated to increase pedicle screw resistance and negatively influence the accuracy of electromyography.

PURPOSE

The primary purpose of this experiment is to evaluate the effect of HA on pedicle screw electrical resistance using a controlled laboratory model.

STUDY DESIGN

Controlled laboratory study.

METHODS

Stimulation of pedicle screws was performed in normal saline (0.9% NaCl). The experimental group included 8 HA coated (HAC) pedicle screws and matched manufacturer control pedicle screws without HAC (Ti6Al4V). All screws were stimulated at 5, 10-, 15-, 20-, and 25-mm submersion depths. Circuit current return was recorded, and pedicle screw electrical resistance was calculated according to Ohm's Law. Data were assessed for normality and variance. Mann-Whitney U and Kruskal-Wallis tests compared groups with Bonferroni correction for multiple testing. Effect size is reported with 95% confidence intervals (95CI). p values <.05 were considered significant.

RESULTS

Current return was detected for all screws (N=24) following subclinical 8.5 µA stimulation at 5, 10-, 15-, 20-, and 25-mm submersion depths (N=144). The effect estimate of HA on pedicle screw electrical resistance is -0.07 (-0.17 to 0.01 95CI). The estimated effect of HA on pedicle screw electrical resistance did not differ across manufacturers. Electrical resistance values were inversely related to submersion depth. Electrical resistance values were lower in the experimental group at 10 mm (p=.04), 15 mm (p=.04), and 25 mm (p=.02) submersion depths. The HA effect ranged from -0.03 to -0.08 as submersion depth varied.

CONCLUSIONS

We found no evidence that HA increased pedicle screw electrical resistance in a matched manufacturer control laboratory model. Electrical stimulation of pedicle screws may be reliable for pedicle breach detection in the presence of HA. Future research should investigate if laboratory findings translate to clinical practice and confirm that electrical stimulation of pedicle screws is a reliable method to detect pedicle breach in the presence of HA.

Pedicle screw accuracy in thoracolumbar fractures- is routine postoperative CT scan necessary?

BACKGROUND

While several studies report on accuracy rates of pedicle screws, risk factors associated with inaccurate pedicle screw positioning in patients with thoracolumbar fractures are reported rarely. CT scan as a routine postoperative control is advocated by various authors, however its necessity remains unclear.

METHODS

Two hundred forty-five patients were included in this retrospective study. Percutaneous dorsal instrumentation was most commonly performed (n = 201). Classification of Zdichavsky et al. and Rao et al. were used to classify screw misplacement and anterior perforation was further evaluated according to the extent of perforation (< 2 mm; > 2 mm). Multivariate analysis was performed to identify risk factors for misplacement of screws.

RESULTS

One thousand sixty-eight pedicle screws were inserted in 245 patients. Misplacement was found in 51 screws (4.8%) in 42 patients (17.1%) according to the classification of Zdichavsky et al. and in 75 screws (7.0%) in 64 patients (26.1%) according to the classification of Rao et al.. An anterior perforation of the vertebral cortex was found in 56 screws (5.2%). Multivariate analysis showed fracture location in the upper thoracic (p = 0.048) and lumbar spine (p = 0.013) to be the only independent predictors for screw misplacement. In addition a significant correlation between pedicle diameter and the occurrence of screw malposition was found (p = 0.003). No consequences were drawn from postoperative routine CT in asymptomatic patients.

CONCLUSION

An overall low rate of screw misplacement was found with fracture location in the upper thoracic and lumbar spine being the only factors independently associated with the risk of screw misplacement. No consequences were drawn from postoperative routine CT in asymptomatic patients. Therefore its use has to be discussed critically.

Morphometric analysis of the proximal thoracic pedicles in Lenke II and IV adolescent idiopathic scoliosis: an evaluation of the feasibility for pedicle screw insertion

PURPOSE

Pedicles on the concave side of the proximal thoracic (PT) curve in adolescent idiopathic scoliosis (AIS) patients with Lenke II and IV deformities tend to be narrow and dysplastic, making pedicle screw (PS) insertion challenging. The aim of this study was to evaluate the feasibility for PS placement in these patients using pedicle chord length, diameter, and channel morphology.

METHODS

In this retrospective study, 56 consecutive AIS patients with Lenke II or IV curves who underwent instrumented posterior spinal fusion (PSF) were studied. The mean age at surgery was 14.8 years and the mean PT curve measured 45°. Two independent investigators evaluated all visible pedicles from T₁ to T₆ vertebral levels using axial images from intraoperative computed tomography-guided navigation recording the pedicle: (1) maximum transverse diameter 'd' at the isthmus, (2) maximum chord length 'l', and (3) qualitative assessment of the channel morphology (types A-D).

RESULTS

Two hundred and sixty-eight concave and 264 convex pedicles were measured. The mean 'd' of the concave pedicles at T₃ and T₄ was < 3.0 mm, compared to > 5.0 mm for the convex counterparts (p < 0.001). Of all concave pedicle channels, 48% had morphology characteristics that were riskier for PS cannulation (type C or D) compared to 2% of all convex pedicle channels (type A or B) (p < 0.001).

CONCLUSION

Almost half of all concave pedicles have morphologic characteristics that make them too small to accommodate a PS. Though PSs could be inserted using an in-out-in technique in these patients, alternative fixation anchors may improve strength and safety.

Screw Malposition: Are There Long-term Repercussions to Malposition of Pedicle Screws?

BACKGROUND/INTRODUCTION

Pedicle screws have long been part of the continued advancements in spine surgery. Despite the many techniques that have been devised for their safe placement, malposition of screws continues to occur. Studies have evaluated the possible safe limits of screw malposition, and have given some insight on anatomic variation in spinal deformity. Review of the literature reveals several cases of deleterious long-term sequelae of malpositioned screws.

DISCUSSION

With the current experience, proposed recommendations are provided to detect and avoid the potential long-term sequelae. Though the literature has helped to define possible concerning screws, there are no good studies predicting long-term risk.

CONCLUSION

Improvements in technology and techniques, advancements in intraoperative confirmation and postoperative surveillance, studies that assist risk stratification, and expert consensus evaluations will help guide surgeons in their decision for addressing misplaced screws.

The Feasibility of Assessing the Cortical Bone Trajectory Screw Placement Accuracy Using a Traditional Pedicle Screw Insertion Evaluation System

STUDY DESIGN

This was a retrospective observational study.

OBJECTIVE

We aimed to characterize the feasibility of assessing the accuracy of cortical bone trajectory (CBT) screw placement in midline lumbar interbody fusion using a traditional pedicle screw insertion accuracy evaluation system based on computed tomography (CT).

SUMMARY OF BACKGROUND DATA

Since Santoni and colleagues proposed CBT as an alternative approach for the treatment of lumbar degenerative disease, CBT has been biomechanically and clinically investigated in detail. The reported misplacement rate was 0%-12.5%. Therefore, these cortical screws may result in severe complications, such as nerve root, vascular, and spinal cord injuries. However, to the best of our knowledge, the accuracy of the current assessment system of cortical bone screw placement has not been described clearly.

MATERIALS AND METHODS

Overall, 342 cortical screws of 69 consecutive patients with lumbar degenerative disease who underwent midline lumbar interbody fusion surgery in one surgeon's initial phase were examined retrospectively. A comprehensive and detailed pedicle screw accuracy classification and grading system was introduced in our study, including 5 types of misplacement: (1) medial and (2) lateral cortical bone perforation (MCP and LCP) of the corresponding pedicle, (3) anterior cortical bone perforation of the vertebral body, (4) endplate perforation, and (5) foraminal perforation (FP). The degree of interobserver and intraobserver agreement with regard to the screw positions based on CT were used as indicators of the reliability of the modified classification system. All patients were retrospectively assessed for screw placement-related complications throughout the entire treatment course to evaluate the relationship between the procedure adequacy and neurological symptoms.

RESULTS

The interobserver and intraobserver agreements were substantial-to-almost perfect (κ=0.78 and 0.88, respectively) in distinguishing the acceptable-placed pedicle screws from those with partial or complete cortical perforation. In the MCP and LCP-the most common types of misplacement-the interobserver agreement was substantial (κ=0.70 and 0.76, respectively), and the intraobserver agreement was almost perfect (κ=0.85 and 0.89, respectively). In total, there are 7 (2.05%) MCP and 65 (19.01%) LCP screws. The screw placement-related complication rate is significantly higher in the MCP and FP groups than that in the LCP group.

CONCLUSIONS

Our study demonstrated that using a pedicle screw classification and grading system based on CT to assess the accuracy of CBT screw placement is feasible and practical. MCP and FP screws are more likely to cause neurological deficits with statistical significance, especially grade 2 MCP. We recommend inexperienced surgeons choose a lateral trajectory rather than a medial one if they cannot ensure accurate screw insertion.

LEVEL OF EVIDENCE

Level III.

Accuracy of fluoroscopic guidance with the coaxial view of the pedicle for percutaneous insertion of lumbar pedicle screws and risk factors for pedicle breach

OBJECTIVE

In this study the authors aimed to evaluate the rate of malposition, including pedicle breach and superior facet violation, after percutaneous insertion of pedicle screws using the coaxial fluoroscopic view of the pedicle, and to assess the risk factors for pedicle breach.

METHODS

In total, 394 percutaneous screws placed in 85 patients using the coaxial fluoroscopic view of the pedicle between January 2014 and September 2017 were assessed, and 445 pedicle screws inserted in 116 patients using conventional open procedures were used for reference. Pedicle breach and superior facet violation were evaluated by postoperative 0.4-mm slice CT.

RESULTS

Superior facet violation was observed in 0.5% of the percutaneous screws and 1.8% of the conventionally inserted screws. Pedicle breach occurred more frequently with percutaneous screws (28.9%) than with conventionally inserted screws (11.9%). The breaches in percutaneous screws were minor and did not reduce the interbody fusion rate. The angle difference between the percutaneous and conventionally inserted screws was comparable. Insertion at the L3 or L4 level, right-sided insertion, placement around a trefoil canal, smaller pedicle angle, and a small difference between the screw and pedicle diameters were found to be risk factors for pedicle breach by percutaneous pedicle screws.

CONCLUSIONS

Percutaneous pedicle screw placement using the coaxial fluoroscopic view of the pedicle carries a low risk of superior facet violation. The screws should be placed carefully considering the level and side of insertion, canal shape, and pedicle angle.

Comparison of the perioperative parameters between computer navigation and fluoroscopy guidance for pedicle screw placement: A protocol for a systematic review and meta-analysis

BACKGROUND

Computer navigation technology is gradually applied to the placement of pedicle screws, but its security and effectiveness still lack of high-quality evidence-based medical evidence. In this study, we will perform a systematic review of previously published randomized controlled trials to investigate the accuracy and effectiveness of computer navigation vsersus fluoroscopy guidance for pedicle screw placement.

METHODS

All study protocols adhered to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. PubMed (MEDLINE), The excerpta medica database, Web of Science (science and social science citation index), The Cochrane Library (Cochrane Database of Systematic Reviews, Cochrane Central Register of Controlled Trials (CENTRAL), Cochrane Methodology Register), China National Knowledge Infrastructure, Chinese Science and Technology Periodical Database, WanFang, Chinese Biomedical Literature Database will be searched for relevant articles up to 18 April, 2020. We will include randomized controlled trials of computer navigation and fluoroscopy guidance for pedicle screw placement. The Cochrane Handbook (v6) will be used for assessment of study bias and reliability, and a meta-analysis will be performed using STATA 16.0. The main outcome will be the proportion of accurate implanted screws. Additional outcomes including: overall complication rate, radiation dosage, length of surgery, length of stay, estimated blood loss.

RESULTS

The quality of the assessments will be assessed through Grading of Recommendations Assessment, Development, and Evaluation. Data will be disseminated through publications in peer-reviewed journals.

CONCLUSION

We will evaluate the accuracy and other perioperative parameters between computer navigation and fluoroscopy guidance for pedicle screw placement.

TRIAL REGISTRATION NUMBER

PROSPERO 2020 CRD42020172087.

Comparison of the accuracy of the cannulated pedicle screw and the classical pedicle screw in the treatment of Scheuermann's kyphosis: A retrospective study

Objectives

This study aims to investigate if use of cannulated pedicle screw (CPS) in the dysplastic pedicles in Scheuermann’s kyphosis (SK) increases the accuracy rate of the screw and reduces screw-related complications.

Patients and methods

This retrospective study included 21 patients (11 males, 10 females; mean age 19.1 years; range, 13 to 22 years) (550 screws) who received correction with pedicle screws due to SK deformity between May 2015 and January 2019. Between 2017 and 2018, classical pedicle screws were used in addition to CPSs in the upper thoracic region (T2, T3, T4) and thin pedicles (group 1). However, during the years 2015 to 2016, only classical pedicle screws were used for the patients who underwent posterior instrumentation for SK (group 2). Computed tomography scanning was used to investigate the accuracy of the screws.

Results

There were 12 patients (316 screws) in group 1 and nine patients (234 screws) in group 2. Seventy-four (13.4%) of all screws were inserted incorrectly. Incorrect screw rate in group 1 was significantly lower than group 2; 21 (6.6%) and 53 (22.6%), respectively (p<0.001). There were no complications related to the use of CPSs after a mean follow-up of two-and-a-half years.

Conclusion

The use of CPS in the surgical treatment of SK does not increase the complication rate; instead it increases the accuracy of the screw. For this reason, we believe that CPS may be an effective and reliable option in the treatment of SK.

The Screw-Aorta Dilemma: Changing Patient Position in Computed Tomography Scan Is Critical in Documenting Aortic Mobility

STUDY DESIGN

Retrospective chart review.

OBJECTIVE

To determine if obtaining a prone computed tomography (CT)-scan can better delineate a questionable screw-aorta relationship.

SUMMARY OF BACKGROUND DATA

Pedicle screw misplacement rate is reported between 6% and 15%. Studies looking at misplacements on a per patient basis show up to 14% of patients have screws at risk (impinging vital structures). A screw abutting the aorta is a management challenge and often requires vascular surgery intervention. However, CT scans routinely done in supine position may overestimate screw-aorta relationship. Change in patient position may allow the aorta to roll away and, in most cases, reveal an uncompromised aorta. This will allow safe removal of pedicle screws without any vascular intervention.

METHODS

One hundred eleven spinal deformity patients who underwent Posterior spinal fusion from 2004 to 2009 were evaluated. Patients with concerning screw-aorta relationship underwent additional prone CT scan. Mobility of the aorta was determined and distance was compared using prone and supine CT scans.

RESULTS

Two thousand two hundred ninety five screws were reviewed, 36 screws in 18 patients were in proximity to the aorta. Fourteen screws (nine patients) appeared to be impinging the aorta. On prone CT, 13 out of the 14 instances the aorta moved away from the screw. The average distance at the screw level was 13.6 ± 4.8 mm in supine position and 8.9 ± 5.4 mm in prone position (P = 0.001). In one instance the relationship was unchanged on prone CT. No screw was noted to violate the lumen or distort the aorta.

CONCLUSION

Supine CT scan alone is not entirely accurate in determining screw-aorta relationship. Prone-CT scan provides additional information for better delineation. This additional diagnostic step can change the treatment option by limiting the need for vascular intervention. When in doubt, the additional use of an arteriogram can allow for improved visualization.

LEVEL OF EVIDENCE

3.

Validity of a Novel Free-Hand Pedicle Screw Placement Training Tool

INTRODUCTION

This study establishes the construct validity of a low-cost training platform designed for high-repetition training of the skills required for fluent use of the five specific tools described for free-hand pedicle screw placement and breach avoidance.

METHODS

A total of 19 participants were included and divided into three groups based on spine surgery experience. Participants were asked to place five pedicle screws into the model. The performance was assessed by recording breaches, technical criteria (0 to 44 points), time to completion, and angulation of the screws. Success (no breaches, no protrusions) frequency (success/time) was calculated and analyzed.

RESULTS

Participants included three spine surgeons, seven advanced trainees (who had placed >10 pedicle screws), and nine inexperienced trainees. None of the screws placed by the spine surgeons breached the pedicle wall. Eight of 35 screws placed by advanced trainees (22.9%) and 31 of 45 screws placed by inexperienced trainees (68.9%) had a pedicle breach. Spine surgeons had a higher median success frequency compared with inexperienced trainees and advanced trainees (P = 0.015). The time needed to place a screw decreased over time (P < 0.0001). There was a trend toward an association between increased training level and decreased time to place five screws (P = 0.076). Increased training level was associated with greater total points scored (P < 0.0001). More screws placed by inexperienced trainees were further away from the ideal pedicle axis compared with those placed by advanced trainees or spine surgeons.

CONCLUSION

An association exists between training level and performance on the pedicle screw model, which suggests construct validity when evaluating our model's use for teaching surgeon learners. The model is easily assembled and is an alternative spine surgery training tool that overcomes limited availability and considerable costs of other training platforms. It can be used in high repetition to establish tool-skill fluency.

LEVEL OF EVIDENCE

Level I.

End Vertebra Versus Apical Vertebra: Where Are We More Likely to Misplace in Spine Deformity?

BACKGROUND DATA

Pedicle screws placement remains technically demanding. The thoracic curve apex is considerably difficult due to its unique morphology and severe rotation. In comparison the upper end vertebrae have smaller pedicles and limited soft tissue exposure. This study seeks to evaluate the likelihood of screw misplacement at the end vertebra and apex.

METHODS

A retrospective review of preoperative and postoperative computed tomographic (CT) scans of spinal deformity patients who underwent posterior spinal fusion with pedicle screw constructs between 2004 and 2011 was performed. Pedicles located at the upper instrumented vertebra (UIV) and lower instrumented vertebra (LIV), and the major and minor apices were evaluated. Pedicle morphology was studied on preoperative CT and screw placement on postoperative CT.

RESULTS

In total, 188 patients met the inclusion criteria, 172 had preoperative CT scans and 133 had postoperative CT scans. The UIV had a significantly lower percentage of normal pedicles (type A) compared with apex major, apex minor, or LIV (59.1% vs. 76.1% vs. 77.3% vs. 98.7%; P<0.001). UIV had significantly the lowest percentage of normal normally placed screws compared with LIV, apex major, or apex minor (69.4% vs. 97.3% vs. 87.6% vs. 92.1%; P<0.001). In a logistic regression adjusted for preoperative Cobb angles, UIV was more likely to have screws misplaced (odds ratio =7.56; 95% confidence interval, 4.01-14.30; P<0.001) and abnormal pedicles (odds ratio=2.81; 95% confidence interval, 1.52-5.19; P=0.001) compared with any other location studied. In abnormal pedicles, 41 (39.8%) of the 103 UIV screws were misplaced, whereas 10 (16.4%) of the 61 apex major, apex minor, or LIV screws were misplaced (P=0.007).

CONCLUSIONS

The UIV presents more of a risk for pedicle screw misplacement and abnormal morphology when compared with LIV and apical vertebra. We believe these findings can aid in the surgeon's preoperative and intraoperative management to ensure increased success in accurate and safe pedicle screw placement.

LEVEL OF EVIDENCE

Level III.

Analysis of spinal stress analysis application in determining method for the pedicle screw placement under the guidance of X-Ray

OBJECTIVE

To evaluate the accuracy of a novel guidance method of pedicle screw implantation determined by spinal stress.

METHODS

We retrospectively analyzed patients underwent pedicle screw internal fixation between January 2015 and August 2018 in our hospital. Patients were divided into two groups according to the methods of pedicle screw implantation namely, the conventional nail placement and novel guidance method of pedicle screw implantation determined by spinal stress. Accuracy of spinal pedicle screw placements was evaluated using intraoperative and postoperative X-ray computed tomography (CT) examination and intraoperative touch of nerve root dissection pedicle bone. The success rate of intraoperative one-time screw placement was calculated according to Heary classification I.

RESULTS

A total of 785 patients underwent pedicle screw internal fixation were retrospectively analyzed. Among them 384 patients were treated using conventional nail placement (Group A) and 401 patients were treated using the technique according to analysis of spinal stress (Group B). There was no significant difference in terms of the characteristics between two groups. There were significant differences in terms of the success rate of total of screw placement (88.7% vs. 96.2%, P < 0.001) including thoracic screw placement (87.8% vs. 94.5%, P = 0.003) and lumbar screw placement (88.8% vs. 96.5%, P = 0.001) for Group A and Group B, respectively.

CONCLUSIONS

Using the novel guidance method of pedicle screw implantation determined by spinal stress might improve the accuracy of pedicle screw implantation.

Grade II Spondylolisthesis: Reverse Bohlman Procedure with Transdiscal S1-L5 and S2 Alar Iliac Screws Placed with Robotic Guidance

BACKGROUND

Grade II spondylolisthesis remains a complex surgical pathology for which there is no consensus regarding optimal surgical strategies. Surgical strategies vary regarding extent of reduction, use of instrumentation/interbody support, and anterior versus posterior approaches with or without decompression. Here we provide the first report on the efficacy of robotic spinal surgery systems in support of the treatment of grade II spondylolisthesis.

METHODS

Using 2 illustrative cases, we provide a technical report describing how robotic spinal surgery platform can be used to treatment grade II spondylolisthesis with a novel instrumentation strategy.

RESULTS

We describe how the "reverse Bohlman" technique to achieve a large anterior fusion construct spanning the pathological level and buttressed by the adjacent level above, coupled with a novel, high-fidelity posterior fixation scheme with transdiscal S1-L5 and S2 alar iliac (S2AI) screws placed in a minimally invasive fashion with robot guidance allows for the best chance of fusion in situ.

CONCLUSIONS

The reverse Bohlman technique coupled with transdiscal S1-L5 and S2AI screw fixation accomplishes the surgical goals of creating a solid fusion construct, avoiding neurologic injury with aggressive reduction, and halting the progression of anterolisthesis. The use of robot guidance allows for efficient placement of these difficult screw trajectories in a minimally invasive fashion.

Navigated robotic assistance results in improved screw accuracy and positive clinical outcomes: an evaluation of the first 54 cases

Computer-aided navigation and robotic guidance systems have become widespread in their utilization for spine surgery. A recent innovation combines these two advances, which theoretically provides accuracy in spinal screw placement. This study describes the cortical and pedicle screw accuracy for the first 54 cases where navigated robotic assistance was used in a surgical setting. This is a retrospective chart review of the initial 54 patients undergoing spine surgery with pedicle and cortical screws using robotic guidance with navigation. A computed tomography (CT)-based Gertzbein and Robbins System (GRS) was used to classify pedicle screw accuracy. Screw tip, tail, and angulation offsets were measured using image overlay analysis. Screw malposition, reposition, and return to operating room rates were collected. 1 of the first 54 cases was a revision surgery and was excluded from the study. Ten screws were placed without the robot due to surgeon discretion and were excluded for the data analysis of 292 screws. Only 0.68% (2/292) of the robot-assisted screws was repositioned based on surgeon discretion. Based on the GRS CT-based grading, 98.3% (287/292) were graded A or B, 1.0% (3/292) screws were graded C, and only 0.7% (2/292) screws was graded D. The average offset from preoperative plan to actual final placement was 1.9 mm from the tip, 2.3 mm from the tail, and 2.8° of angulation. In the first 53 cases, 292 screws placed with navigated robotic assistance resulted in a high level of accuracy (98.3%), adequate screw offsets from planned trajectory, and zero complications.

Robotic-assisted navigated minimally invasive pedicle screw placement in the first 100 cases at a single institution

Proper pedicle screw placement is an integral part of spine fusion requiring expertly trained spine surgeons. Advances in medical imaging guidance have improved accuracy. There is high interest in the emerging field of robot-assisted spine surgery; however, safety and accuracy studies are needed. This study describes the pedicle screw placement of the first 100 cases in which navigated robotic assistance was used in a private practice clinical setting. A single-surgeon, single-site retrospective Institutional Review Board-exempt review of the first 100 navigated robot-assisted spine surgery cases was performed. An orthopaedic surgeon evaluated screw placement using plain film radiographs. In addition, pedicle screw malposition, reposition, and return to operating room (OR) rates were collected. Results demonstrated a high level (99%) of successful surgeon assessed pedicle screw placement in minimally invasive navigated robot-assisted spine surgery, with no malpositions requiring return to the OR.

Accuracy of Current Techniques for Placement of Pedicle Screws in the Spine: A Comprehensive Systematic Review and Meta-Analysis of 51,161 Screws

BACKGROUND

Pedicle screws (PSs) are routinely used for stabilization to enhance fusion in a variety of spinal diseases. Although the accuracy of different PS placement methods has been previously reported, most of these studies have been limited to 1 or 2 techniques. The purpose was to determine the current accuracy of PS placement among 4 modalities of PS insertion (freehand [FH], fluoroscopy-assisted [FA], computed tomography navigation-guided [CTNav], and robot-assisted [RA]) and analyze variables associated with screw misplacement.

METHODS

A systematic review was performed of peer-reviewed articles reporting PS accuracy of 1 technique from January 1990 to June 2018. Accuracy of PS placement, PS insertion technique, and pedicle breach (PB) data were collected. A meta-analysis was performed to estimate the overall pooled (OP) rates of PS accuracy as a primary outcome, stratified by screw insertion techniques. Potential determinants were analyzed via meta-regression analyses.

RESULTS

Seventy-eight studies with 7858 patients, 51,161 PSs, and 3614 cortical PBs were included. CTNav showed the highest PS placement accuracy compared with other techniques: OP accuracy rates were 95.5%, 93.1%, 91.5%, and 90.5%, via CTNav, FH, FA, and RA techniques, respectively. RA and CTNav were associated with the highest PS accuracy in the thoracic spine, compared with FH.

CONCLUSIONS

The OP data show that CTNav has the highest PS accuracy rates. Thoracic PSs were associated with lower accuracy rates; however, RA showed fewer breaches in the thoracic spine compared with FH and FA. Given the heterogeneity among studies, further standardized and comparative investigations are required to confirm our findings.

Comparison of the accuracy of cannulated pedicle screw versus conventional pedicle screw in the treatment of adolescent idiopathic scoliosis: A randomized retrospective study

BACKGROUND

Pedicle screws are commonly used to treat adolescent idiopathic scoliosis (AIS). Many studies have discussed the rates and effects of pedicle screw misplacement. In this study, to increase the accuracy rate, cannulated pedicle screws were inserted into the periapical vertebrae, highly rotated vertebrae, and vertebrae with very thin pedicles in a single patient group. We compared these results with those of a patient group who underwent conventional pedicle screw placement.

METHODS

Twenty-eight AIS patients treated surgically between 2015 and 2017 with cannulated pedicle screws or conventional pedicle screws were included. Group 1 (n = 15) received cannulated pedicle screws, whereas group 2 (n = 13) received conventional pedicle screws. Postoperative computed tomography scans were used to evaluate pedicle screw position. Pedicle perforation was assessed using the classification by Rao et al: grade 0, no perforation; grade 1, only the threads outside the pedicle (less than 2 mm); grade 2, core screw diameter outside the pedicle (2-4 mm); and grade 3, screw entirely outside the pedicle. Medial screw malposition was measured between the medial pedicle wall and the medial margin of the screw. Lateral screw malposition was measured between the lateral corpus wall and lateral screw margin.

RESULTS

Placement accuracy of 703 screws (group 1, 376; group 2, 327) was evaluated. A total of 142 (20.1%) pedicle screw perforations occurred: 63 (17.1%) in group 1 and 79 (25%) in group 2 (P < .05). There was no statistically significant intergroup difference in medial perforation (group 1, 34 [9%] vs group 2, 31 [10%]). Lateral perforation was significantly less common in group 1 (n = 29; 7.7%) than in group 2 (n = 4; 14.7%) (P = .0002).

CONCLUSIONS

The use of cannulated screws to treat AIS decreases perforation and complication rates. Although it did not significantly lower the medial perforation rate, it dramatically reduced the lateral perforation rate. The use of cannulated screws enables intraoperative confirmation of placement accuracy. Our data suggest that cannulated pedicle screw use to treat AIS is safer and more efficient.

Intraoperative CT Scan Verification of Pedicle Screw Placement in AIS to Prevent Malpositioned Screws: Safety Benefit and Cost

STUDY DESIGN

Prospective database review.

OBJECTIVES

Determine if use of intraoperative 3D imaging of pedicle screw position provides clinical and cost benefit.

SUMMARY OF BACKGROUND

Injury or reoperation from malpositioned pedicle screws in adolescent idiopathic scoliosis (AIS) surgery occurs but is increasingly considered to be a never-event. To avoid complications, intraoperative 3D imaging of screw position may be obtained.

METHODS

A prospective, consecutive AIS database at a high-volume pediatric spine center was examined three years before and after implementation of an intraoperative low-dose computed tomographic (CT) scan protocol. All screws were placed via freehand technique and corrected if found to be outside optimal trajectory on the postplacement CT scan. Demographic and outcome data were compared between cohorts, along with number, location, and reason for screw change. Cost analysis was based on the average cost of revision surgery for screw malposition versus intraoperative CT use.

RESULTS

There were 153 patients in the pre-CT and 153 in the post-CT cohorts with a minimum 2-year follow-up. Two reoperations were needed for revision of improper screw placement in the pre-CT group and none in the post-CT group. Number of patients needed to harm was 76 (absolute risk increase = 1.31% [-0.49%, 3.11%]). Of those who had intraoperative CT scans, 80 (52.3%) needed on average 1.75 screw trajectories/lengths changed. Forty-three percent were medial breaches; of these, 39% were in the concavity. There were no differences between patients who did and did not need screw repositioning with regard to body mass index (BMI), age, curve size, surgeon/trainee side, screw density, or preoperative and one-year postoperative Scoliosis Research Society-22 patient questionnaire (SRS-22) scores. The average cost of reoperation for malposition was $4,900, whereas the cost of a single intraoperative CT was $232.

CONCLUSION

Intraoperative CT is an effective tool to prevent reoperation in AIS surgery for incorrect screw placement. Despite high volume, experience, and specialty training, incorrect trajectories occur and systems should be in place for preventable error.

LEVEL OF EVIDENCE

Level II.

Morphometrical evaluation of decompression obtained through corpectomy. Heading towards to posterior approaches

INTRODUCTION

We analysed the decompression obtained by dorsal or dorsolumbar corpectomy measured by Cobb angle and the spinal area prior to and after surgery and compared the evolution of the technique over the last five years of the study.

MATERIAL AND METHOD

A retrospective review of patients operated between 2005 and 2015 through anterior or posterior approaches was performed.

RESULTS

24 patients were studied and a significant improvement was observed between the preoperative and postoperative morphometrical measurement (4.18° correction of the kyphosis and an increase of 130.8mm² in the spinal canal, p<.001 in both cases) and in clinical parameters (45.8% of patients improved in ASIA, and Karnofsky showed 13 points of improvement, p<.001 in both cases). However, there was no correlation between clinical and morphological parameters. We also observed that in the last five years of the study posterior approaches were more frequently used with good results.

CONCLUSIONS

Dorsal corpectomy allows significant spinal decompression, with neurological improvement but this does not correlate with the measurement of decompression. Thanks to technical improvements, less invasive techniques (posterior approaches and MISS) allow good clinical results, which are similar to those obtained by anterior techniques.

Variability Analysis of Manual and Computer-Assisted Preoperative Thoracic Pedicle Screw Placement Planning

STUDY DESIGN

A comparison among preoperative pedicle screw placement plans, obtained from computed tomography (CT) images manually by two spine surgeons and automatically by a computer-assisted method.

OBJECTIVE

To analyze and compare the manual and computer-assisted approach to pedicle screw placement planning in terms of the inter- and intraobserver variability.

SUMMARY OF BACKGROUND DATA

Several methods for computer-assisted pedicle screw placement planning have been proposed; however, a systematic variability analysis against manual planning has not been performed yet.

METHODS

For 256 pedicle screws, preoperative placement plans were determined manually by two experienced spine surgeons, each independently performing two sets of measurements by using a dedicated software for surgery planning. For the same 256 pedicle screws, preoperative placement plans were also obtained automatically by a computer-assisted method that was based on modeling of the vertebral structures in 3D, which were used to determine the pedicle screw size and insertion trajectory by maximizing its fastening strength through the underlying bone mineral density.

RESULTS

A total of 1024 manually (2 observers × 2 sets × 256 screws) and 256 automatically (1 computer-assisted method × 256 screws) determined preoperative pedicle screw placement plans were obtained and compared in terms of the inter- and intraobserver variability. A large difference was observed for the pedicle screw sagittal inclination that was, in terms of the mean absolute difference and the corresponding standard deviation, equal to 18.3° ± 7.6° and 12.3° ± 6.5°, respectively for the intraobserver variability of the second observer and for the interobserver variability between the first observer and the computer-assisted method.

CONCLUSION

The interobserver variability among the observers and the computer-assisted method is within the intraobserver variability of each observer, which indicates on the potential use of the computer-assisted approach as a useful tool for spine surgery that can be adapted according to the preferences of the surgeon.

LEVEL OF EVIDENCE

3.

Quantitative comparison of a laterally misplaced pedicle screw with a re-directed screw. How much pull-out strength is lost?

Objective

Redirecting of a laterally misplaced pedicle screw into the accurate position decreases the pull-out strength due to the reinsertion, lateral wall cortical perforation and widening of the pedicle hole. Thus, this biomechanical study was performed to quantitatively analyze the pullout strength of a redirected laterally misplaced pedicle screw into the accurate position.

Methods

Thirty pedicules of 15 bovine vertebrae were separated to 3 groups, according to the screw placement method: 1) standard flawless trajectory; 2) trajectory with lateral pedicle wall perforation; 3) trajectory with lateral wall perforation redirected to the standard trajectory. Samples were placed on a universal testing machine and pullout loads were measured. Kruskal-Wallis test was utilized within 95% confidence interval and p value <0.05 to test for the statistical significance.

Results

The mean pullout strength was 2891±654,2 N(1383-3814,5) in Group 1; 817,8±227,6 N(308,6-1144,9) in Group 2 and 2081,1±487,7 N(1583,5-2962,5) in Group 3. The results found out to be statistically significant (p<0.05). Inter-group comparisons revealed that lateral pedicle wall perforation significantly decreases the pullout strength (p<0.05) and redirection of the screw increases the strength (p<0.05), however it was still weaker than the screws with flawless standard trajectory but this was not statistically significant (p>0.05).

Conclusion

The results of this study confirm that pullout strength of pedicle screw decreases by approximately 71% when the lateral wall is perforated and decreases 28% after redirection to the accurate position.

Safety of Pedicle Screws in Adolescent Idiopathic Scoliosis Surgery

To review existing publications on the safety of pedicle screw insertions in adolescent idiopathic scoliosis (AIS). Despite having increased risk for neurological and visceral injuries, the use of pedicle screws have led to increased correction rates in scoliosis surgery. A review was performed on topics pertinent to pedicle screw insertion in AIS, which included pedicle morphometry in AIS, structures at risk during pedicle screw insertion, and accuracy and safety of various pedicle screw insertion techniques. The importance of computer navigation and future research regarding pedicle screw placement in AIS were also briefly reviewed. Many authors have reported abnormal pedicle anatomy in AIS. Injury to the neural structures was highest over the apical region, whereas aortic injury was the highest at T5 and T10. In the proximal thoracic spine, the esophagus could be injured even with screws as short as 25 mm. Overall pedicle perforation rates for perforations >0 and >2 mm (assessed by computed tomography) ranged from 6.4% to 65.0% and 3.7% to 29.9%, respectively. The critical pedicle perforation (>2 mm excluding lateral thoracic) and anterior perforation (>0 mm) rates was reported to range from 1.5% to 14.5% and 0.0% to 16.1%, respectively. Pedicle perforation rates were lower with the use of computer navigation. The incidence of neurological adverse events after scoliosis surgery was 0.06%–1.9%. Aortic injury has only been observed in case reports. According to the available literature, pedicle screw insertion in AIS is considered safe with low rates of clinical adverse events. Moreover, the use of navigation technology has been shown to reduce pedicle perforation rates.

Review of Cortical Bone Trajectory: Evidence of a New Technique

This article summarizes recent evidence on the cortical bone trajectory (CBT) obtained from published anatomical, biomechanical, and clinical studies. CBT was proposed by Santoni in 2009 as a new trajectory that can improve the fixation of pedicle screws in response to screw loosening in osteoporotic patients. Recently, research interest has been growing with increasing numbers of published series and frequent reports of new applications. We performed an online database search using the terms “cortical bone trajectory,” “pedicle screw,” “CBT spine,” “CBT fixation,” “MISS CBT,” and “traditional trajectory.” The search included the PubMed, Ovid MEDLINE, Cochrane, and Google Scholar databases, resulting in an analysis of 42 articles in total. These covered three aspects of CBT research: anatomical studies, biomechanical parameters, and clinical cases or series. Compared to the traditional trajectory, CBT improves pullout strength, provides greater stiffness in cephalocaudal and mediolateral loading, and shows superior resistance to flexion/extension; however, it is inferior in lateral bending and axial rotation. CBT seems to provide better immediate implant stability. In clinical studies, CBT has shown better perioperative results for blood loss, length of stay in hospital, and surgery time; similar or better clinical postoperative scores; and similar comorbidity, without any major fixation system complications due to instrumentation failure or screw misplacement. In addition, advantages such as less lateral exposure allow it to be used as a minimally invasive technique. However, most of the clinical studies were retrospective case series or case-control studies; prospective evidence on this technique is scarce, making a definitive comparison with the traditional trajectory difficult. Nevertheless, we can conclude that CBT is a safe technique that offers good clinical results with similar biomechanical and perioperative parameters to those of the traditional trajectory. In addition, new applications can improve its results and make it useful for additional pathologies.

Can Postoperative Radiographs Accurately Identify Screw Misplacements?

STUDY DESIGN

Retrospective case series.

OBJECTIVE

The objective of this study was to determine the safety of postoperative radiographs to assess screw placement.

SUMMARY OF BACKGROUND DATA

Previously defined criteria are frequently employed to determine pedicle screw placement on intraoperative supine radiographs. Postoperatively, radiographs are typically used as a precursor to identify screws of concern, and a computed tomographic (CT) is typically ordered to confirm screw safety.

METHODS

First, available postoperative PA and lateral radiographs were reviewed by 6 independently blinded observers. Screw misplacement was assessed using previously defined criteria. A musculoskeletal radiologist assessed all CT scans for screw placement. Pedicle screw position was classified either as acceptable or misplaced. Misplacements were subclassified as medial, lateral, or anterior.

RESULTS

One hundred four patients with scoliosis or kyphosis underwent posterior spinal fusion and had postoperative CT scan available were included. In total, 2,034 thoracic and lumbar screws were evaluated. On CT scan, 1,772 screws were found to be acceptable, 142 were laterally misplaced, 30 medially, and 90 anteriorly. Of the 30 medially placed screws, 80% to 87% screws were believed to be in positions other than medial, with a median of 73% (63% to 92%) of these screws presumed to be in normal position. Similarly, of the 142 screws placed laterally, 49% to 81% screws were identified in positions other than lateral, with a median of 77% (59% to 96%) of these screws felt to be in normal position. Of the 90 anteriorly misplaced screws, 16% to 87% screws were identified in positions other than anterior, with 72% (20% to 98%) identified as normal. The criteria produced a median 52% sensitivity, 70% specificity, and 68% accuracy across the 6 observers.

CONCLUSION

Radiograph is a poor diagnostic modality for observing screw position.

LEVEL OF EVIDENCE

Level IV.