Screw Breach Research Articles

Technique, Safety, and Accuracy Assessment of Percutaneous Pedicle Screw Placement Utilizing Computer-Assisted Navigation in Lateral Decubitus Single-Position Surgery.

Percutaneous pedicle screw (PPS) placement has become a pivotal technique in spinal surgery, increasing surgical efficiency and limiting the invasiveness of surgical procedures. The aim of this study was to analyze the accuracy of computer-assisted PPS placement with a standardized technique in the lateral decubitus position. A retrospective review of prospectively collected data was performed on 44 consecutive patients treated between 2021 and 2023 with lateral decubitus single-position surgery. PPS placement was assessed by computed tomography scans, and breaches were graded based on the magnitude and direction of the breach. Facet joint violations were assessed. Variables collected included patient demographics, indication, intraoperative complications, operative time, fluoroscopy time, estimated blood loss, and length of stay. Forty-four patients, with 220 PPSs were identified. About 79.5% of all patients underwent anterior lumbar interbody fusion only, 13.6% underwent lateral lumbar interbody fusion only, and 6.8% received a combination of both anterior lumbar interbody fusion and lateral lumbar interbody fusion. Eleven screw breaches (5%) were identified: 10 were Grade II breaches (<2 mm), and 1 was a Grade IV breach (>4 mm). All breaches were lateral. About 63.6% involved down-side screws indicating a trend toward the laterality of breaches for down-side pedicles. When analyzing breaches by level, 1.2% of screws at L5, 13% at L4, and 11.1% at L3 demonstrated Grade II breaches. No facet joint violations were noted. PPS placement utilizing computer-assisted navigation in lateral decubitus single-position surgery is both safe and accurate. An overall breach rate of 5% was found; considering a safe zone of 2 mm, only 1 screw (0.5%) demonstrated a relevant breach. PPS placement is both safe and accurate. Breaches are rare, and when breaches do occur, they are lateral.

284 CT-Based Assessment of Prone Versus Lateral Pedicle Screw Placement Accuracy: A Retrospective Single-surgeon Study

INTRODUCTION: Lateral lumbar interbody fusion (LLIF) including the anterior-to-psoas oblique lumbar interbody fusion (OLIF) has conventionally relied on pedicle screw placement (PSP) for construct stabilization. Single-position surgery with lumbar interbody fusion (LIF) in the lateral decubitus position with concomitant PSP has been associated with increased operative efficiency. What remains unclear is the accuracy of PSP with robotic guidance when compared to the more familiar prone patient positioning. METHODS: We identified all consecutive patients treated with interbody fusion and PSP in the prone or lateral position by a single surgeon between January 2019 and October 2022. All pedicle screws placed were analyzed using CT imaging to determine appropriate positioning according to the Gertzbein-Robbins Classification Grading System. Multivariate logistic regression models were constructed to identify risk factors for the occurrence of a radiographically significant breach. RESULTS: 89 consecutive patients were included (n = 690 screws), of whom 46 were treated in the prone position (n = 477 screws) and 43 in the lateral decubitus position (n = 213 screws). There were fewer breaches in the prone (n = 13; 2.7%) versus lateral decubitus group (n = 15; 7.0%; p = 0.012). Nine (1.9%) radiographically significant breaches occurred in the prone group compared to 10 (4.7%) in the lateral decubitus group (p = 0.019), for a prone vs. lateral decubitus pedicle screw accuracy rate of 98.1% vs. 95.3%. There were no significant differences in BMI between prone vs. lateral decubitus cohorts (30.1 vs. 29.6) or breached patients vs. non-breached patients (31.2 vs. 29.5). In multivariate models, prone position was the only significant protective factor for screw accuracy; we did not identify any other significant risk factors for screw breach. CONCLUSIONS: The present data suggest pedicle screws placed with robotic assistance have higher placement accuracy in the prone position.

Evaluating the safe zone for lumbar pedicle screws: are midline crossing screws indicative of pedicle breach?

BACKGROUND CONTEXTPedicle screw breach (PSB) is not uncommon following lumbar instrumentation, and in some instances, it may lead to vascular and/or neurologic complications. Previous literature suggested that screws crossing the vertebral midline on an anterior-posterior (AP) radiograph (or midsagittal on CT) are concerning for medial pedicle breach. OBJECTIVEOur primary aim was to map out the safe zones (SZ) of bilateral pedicle instrumentation and their relationship at each lumbar vertebral level. Our secondary aim was to evaluate the presence of SZs’ intersection at each lumbar level, denoting safe midline pedicle screw crossing not otherwise associated with medial pedicle breach. STUDY DESIGN/SETTINGRetrospective Anatomical Study. PATIENT SAMPLEAdult patients in the from “The Cancer Imaging Archive” (TCIA) database who have not had thoraco-lumbo-sacral fusion. OUTCOME MEASURESPhysiologic measures obtained through 3D analysis of CT images and virtual pedicle screws. METHODCT scans of 51 patients were randomly selected from “The Cancer Imaging Archive” (TCIA) online database for analysis. The Sectra 3D Spine software was used to create 3D renderings, place virtual screws, and make measurements. At each lumbar vertebra, the right and left pedicle corridors were mapped. At each pedicle, two screw positions were templated, the “medial limit screw” (MLS) and the “lateral limit screw” (LLS). Each limit screw was the most extreme position that the screw could exist in without causing a medial or lateral breach. The safe zone was defined as the zone between MLS and LLS. Measurements were taken for each level (between L1 and L5) and side (Left, Right). RESULTSA total of 253 lumbar vertebrae from 51 patients (mean age 53.1, 56.9% male) were included. Two vertebrae from two patients were removed for poor image quality. Out of the 506 screw positions analyzed in our study, 97.4% had overlapping SZ and crossed the midplane without medial pedicle breach. The significant factors (p<.01) for safe midplane-crossing screws included: the screw length (L1–L5); the laterality of the screw entry point (L1–L4); and the pedicle diameter (L2 and L5). CONCLUSIONSA midline crossing pedicle screw on a lumbar AP radiograph is not necessarily indicative of a medial pedicle screw breach. Anatomical (ie, larger pedicle diameter) and technical (ie, longer screws, and lateral entry points) factors allow for safety zone intersections and indicate safe midline crossing by pedicle screws.

Effect of L5 spinal canal type on pedicle screw placement based on CT imaging: a retrospective clinical study.

The objective of this study was to investigate the optimal entry point and pedicle camber angle for L5 pedicle screws of different canal types. CT imaging data were processed by Mimics for simulated pedicle screw placement, and PD (Pedicle diameter), PCA (Pedicle camber angle), LD (Longitudinal distance), TD (Transverse distance), and PBG (Pedicle screw breach grade) were measured. Then they were divided into the Round group and Trefoil group according to the type of spinal canal. When comparing PD, PCA, LD, TD, and PBG, the two sides of the pedicle were compared separately, so they were first divided into the round-type pedicle group and the trefoil-type pedicle group. In the round-type pedicle group (n = 134) and the trefoil-type pedicle group (n = 264), there was no significant difference in PD and LD, but there was a significant difference in PCA between the two groups (t = - 4.072, P < 0.05). A statistically significant difference in the distance of the Magerl point relative to the optimal entry point (t = - 3.792, P < 0.05), and the distance of the Magerl point relative to the optimal entry point was greater in the trefoil-type pedicle group than in the round-type pedicle group. The optimal entry point for L5 is more outward than the Magerl point, and the Trefoil spinal canal L5 is more outwardly oriented than the Round spinal canal L5, with a greater angle of abduction during pedicle screw placement.

"Critical pedicle wall" breaches analysis in complex spinal deformity using O-arm navigation.

Free-hand and fluoroscopic-guided pedicle screw placement has been associated with higher rates of pedicle breaches (frequency range 15-40% especially in deformed pedicles). Neurological complications are more "critical" (i.e., frequent and significant) with medial and inferior pedicle-wall breaches due to the proximity of the neural elements. Here, we analyzed the effectiveness of O-arm navigation in minimizing "critical" pedicle wall breaches and their complications in 21 complex spinal deformity cases. Twenty-one complex spinal deformity cases were prospectively managed with O-arm-navigated posterior-instrumented fusions. Preoperative assessment included; evaluation of the type of scoliosis, the magnitude of the deformity, and the anatomy of the pedicles - (i.e., classified using Watanabe et al.). The O-arm was used to confirm and grade both the intraoperative and postoperative location of screws. Other variables analyzed included; duration of surgery, estimated blood loss, complications, and radiation exposure. In 21 patients, 259 (63.45%) of 384 pedicles were instrumented; we observed 22 of 259 pedicle screw breaches. Significant (>2 mm) breaches were observed in two medial and one inferior wall cases that required revision; the overall biomechanically significant screw breach rate was (3/259) 1.2% with an accuracy rate of 98.8%. Pedicle screw placement resulted in another 14 nonsignificant (<2 mm) breaches; ten were medial and four involved the inferior wall. As anterior, lateral, and "in-out-in" trajectory pedicle screws beaches were nonsignificant, they were not included in our analysis. O-arm navigation decreased the incidence of medial and inferior (i.e., >2 mm "critical") pedicle screw breaches applied in 21 patients with deformed pedicles due to scoliosis. Further, the O-arm minimized the operating time, decreased the estimated blood loss, and reduced the incidence of complications.

Intravascular ultrasound to aid in the diagnosis and revision of an intra-aortic pedicle screw: illustrative case.

Pedicle screw impingement on vessel walls has the potential for complications due to pulsatile effects and wall erosion. Artifacts from spinal instrumentation create difficulty in accurately evaluating this interface. The authors present the first case of intravascular ultrasound (IVUS) used to characterize a pedicle screw breach into the aortic lumen. A 21-year-old female with surgically corrected scoliosis underwent computed tomography angiography (CTA) 3 years postoperatively, which revealed a pedicle screw within the thoracic aorta lumen. Metal artifact distorted the CTA images, which prompted the decision to use intraoperative IVUS. The IVUS confirmed the noninvasive imaging findings and guided final decisions regarding aortic endograft size and location during spine hardware revision. For asymptomatic patients presenting with pedicle screws malpositioned in or near the aorta, treatment decisions revolve around the extent of vessel wall penetration. Intraluminal depth can be obscured by artifact on computed tomography or magnetic resonance imaging or inadequately evaluated by a transesophageal echocardiogram. In our intraoperative experience, IVUS confirmed the depth of vessel lumen violation by a single pedicle screw and no wall penetration by two additional screws of concern. This was useful in deciding on thoracic endovascular aortic repair graft size and landing zone and facilitated safe spinal instrumentation removal and revision.

Retrospective single-surgeon study of prone versus lateral robotic pedicle screw placement: a CT-based assessment of accuracy.

Lateral lumbar interbody fusion including anterior-to-psoas oblique lumbar interbody fusion has conventionally relied on pedicle screw placement (PSP) for construct stabilization. Single-position surgery with lumbar interbody fusion in the lateral decubitus position with concomitant PSP has been associated with increased operative efficiency. What remains unclear is the accuracy of PSP with robotic guidance when compared with the more familiar prone patient positioning. The present study aimed to compare robot-assisted screw placement accuracy between patients with instrumentation placed in the prone and lateral positions. The authors identified all consecutive patients treated with interbody fusion and PSP in the prone or lateral position by a single surgeon between January 2019 and October 2022. All pedicle screws placed were analyzed using CT scans to determine appropriate positioning according to the Gertzbein-Robbins classification grading system (grade C or worse was considered as a radiographically significant breach). Multivariate logistic regression models were constructed to identify risk factors for the occurrence of a radiographically significant breach. Eighty-nine consecutive patients (690 screws) were included, of whom 46 (477 screws) were treated in the prone position and 43 (213 screws) in the lateral decubitus position. There were fewer breaches in the prone (n = 13, 2.7%) than the lateral decubitus (n = 15, 7.0%) group (p = 0.012). Nine (1.9%) radiographically significant breaches occurred in the prone group compared with 10 (4.7%) in the lateral decubitus group (p = 0.019), for a prone versus lateral decubitus PSP accuracy rate of 98.1% versus 95.3%. There were no significant differences in BMI between prone versus lateral decubitus cohorts (30.1 vs 29.6) or patients with screw breach versus those without (31.2 vs 29.5). In multivariate models, the prone position was the only significant protective factor for screw accuracy; no other significant risk factors for screw breach were identified. The present data suggest that pedicle screws placed with robotic assistance have higher placement accuracy in the prone position. Further studies will be needed to validate the accuracy of PSP in the lateral position as single-position surgery becomes more commonplace in the treatment of spinal disorders.

Intraoperative triggered electromyographic monitoring of pedicle screw efficiently reduces the lumbar pedicle breach and re-operative rate-a retrospective analysis based on postoperative computed tomography scan

BackgroundTo investigate whether intraoperative triggered electromyographic (T-EMG) monitoring could effectively reduce the breach rate of pedicle screws and the revision rate.MethodsPatients with posterior pedicle screw fixation from L1-S1 were enrolled between June 2015 and May 2021. The patients in whom T-EMG was utilized were placed in the T-EMG group, and the remaining patients were considered in the non-T-EMG group. Three spine surgeons evaluated the images. The two groups were divided into subgroups based on screw position (lateral/superior and medial/inferior) and breach degree (minor and major). Patient demographics, screw positions, and revision procedures were reviewed.ResultsA total of 713 patients (3403 screws) who underwent postoperative computed tomography (CT) scans were included. Intraobserver and interobserver reliabilities were perfect. The T-EMG and non-T-EMG groups had 374(1723 screws) and 339 (1680 screws) cases, respectively. T-EMG monitoring efficiently reduced the overall screw breach (T-EMG 7.78% vs. non-T-EMG 11.25%, p = 0.001). in the subgroup analysis, the medial/inferior breach rate was higher in the T-EMG group than in the non-T-EMG group (T-EMG 6.27% vs. non-T-EMG 8.93%, p = 0.002); however, no difference was observed between the lateral and superior breaches (p = 0.064). A significant difference was observed between the minor (T-EMG 6.21% vs. non-T-EMG 8.33%, p = 0.001) and major (T-EMG 0.06% vs. non-T-EMG 0.6%, p = 0.001) medial or inferior screw breach rates. Six screws (all in the non-T-EMG group) underwent revision, with a significant difference between the groups (T-EMG 0.0% vs. non-T-EMG 3.17%, p = 0.044).ConclusionsT-EMG is a valuable tool in improving the accuracy of screw placement and reducing the screw revision rate. The screw-nerve root distance is vital in causing symptomatic screw breach.Trial registrationThe study is retrospective registered in China National Medical Research Registration and Archival information system in Nov 17th 2022.

Decreasing the Pedicle Screw Misplacement Rate in the Thoracic Spine With Robot-guided Navigation.

A retrospective chart review. The aim of this study was to evaluate the screw accuracy of thoracic pedicle screws placed with a robot-guided navigation system. Thoracic pedicles are smaller in diameter than lumbar pedicles, making pedicle screw placement difficult. Misplaced pedicle screws may present complications including decreased construct stability, and increased risks of neurological deficits and blood vessel perforation. There is a dearth of knowledge on thoracic pedicle screw accuracy placed with a robot. A retrospective analysis of the robot-assisted placement of thoracic pedicle screws was performed. Preoperative and postoperative computed tomography (CT) scans of the implanted thoracic screws were collected to assess screw placement accuracy, pedicle breadth, and placement deviations. A CT-based Gertzbein and Robbins System was used to classify pedicle screw accuracy in 2mm increments. A custom image overlay software was used to determine the deviations between the preoperatively planned trajectory of pedicle screws and final placement at screw entry (tail), and tip in addition to the angular deviation. Seventy-five thoracic pedicle screws were implanted by navigated robotic guidance in 17 patients, only 1.3% (1/75) were repositioned intraoperatively. Average patient age and body mass index were 57.5 years and 25.9kg/m 2 , respectively, with 52.9% female patients. Surgery diagnoses were degenerative disk disease (47.1%) and adjacent segment disease (17.6%). There were zero complications, with no returns to the operating room. According to the CT-based Gertzbein and Robbins pedicle screw breach classification system, 93.3% (70/75) screws were grade A or B, 6.6% (5/75) were grade C, and 0% were grade D or E. The average deviation from the preoperative plan to actual final placement was 1.8±1.3mm for the screw tip, 1.6±0.9mm for the tail, and 2.1±1.5 degrees of angulation. The current investigation found a 93.3% accuracy of pedicle screw placement in the thoracic spine. Navigated robot assistance is a useful system for placing screws in the smaller pedicles of the thoracic spine. Level III-retrospective nonexperimental study.

Robot-assisted percutaneous pedicle screw placement accuracy compared with alternative guidance in lateral single-position surgery: a systematic review and meta-analysis.

While single-position surgery (SPS) eliminates the need for patient repositioning, the placement of screws in the unconventional lateral position poses unique challenges related to asymmetry relative to the surgical table. Use of robotic guidance or intraoperative navigation can help to overcome this. The aim of this study was to compare the relative accuracies offered by these various navigation modalities for pedicle screws placed in lateral SPS. According to Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines, the PubMed/Medline, Embase, and Cochrane Library databases were queried for studies reporting pedicle screw placement accuracy using fluoroscopic, CT-navigated, O-arm, or robotic guidance in lateral SPS, and a systematic review and meta-analysis was performed. Included studies all compared evaluated screw placement accuracy in lateral SPS using a single navigation method. Quality assessment was performed using the Grading of Recommendations Assessment, Development and Evaluation (GRADE) system; risk of bias was assessed using the Newcastle-Ottawa Scale and the Joanna Briggs Institute checklist. The primary outcome, rate of pedicle screw breach, was analyzed using random-effects meta-analysis. Eleven studies were included comprising 548 patients who underwent the placement of instrumentation with 2488 screws. For the fluoroscopic, CT-navigated, O-arm, and robotic guidance cohorts, there were 3, 2, 3, and 3 studies, respectively. Breach rates by modality were as follows: fluoroscopic guidance (6.6%), CT navigation (4.7%), O-arm (3.9%), and robotic guidance (3.9%). Random-effects meta-analysis showed a significant difference between studies, with an overall breach rate of 4.9% (95% CI 3.1%-7.5%; p < 0.001); however, testing for subgroup differences failed to show a significant difference between guidance modalities (QM = 0.69, df = 3; p = 0.88). Heterogeneity between studies was significant (I2 = 79.0%, τ2 = 0.41, χ2 = 47.65, df = 10; p < 0.001). Robotic guidance of screws is noninferior to alternative guidance modalities in lateral SPS; however, additional prospective studies directly comparing different guidance types are merited.

O-arm real-time guidance in cervical pedicle screw fixation

To explore the technical aspects of the accuracy of cervical pedicle screw placement with O-arm guidance. The clinical data of 21 patients who underwent cervical pedicle screw fixation by O-arm real-time guidance from December 2015 to January 2020 were analyzed retrospectively. There were 15 males and 6 females, aged from 29 to 76 years old with an average of (45.3±11.5) years. The postoperative CT scan was utilized to evaluate the placement of the pedicle screw and classified according to the Gertzbein and Robbins classification. A total of 132 pedicle screws were implanted in 21 patients, 116 at C3-C6 and 16 at C1 and C2. According to Gertzbein & Robbins classification, the overall breach rates were found to be 11.36% (15/132) with 73.33% (11 screws) Grade B, 26.67% (4 screws) Grade C, and no Grade D or E screw breaches. There were no pedicle screw placement related complications at final follow-up. The application of O-arm real-time guidance technology can make cervical pedicle screw placement reliable. High accuracy and better intra-operative control can increase surgeon's confidence in using cervical pedicle instrumentation. Considering the high-risk nature of anatomical area around cervical pedicle and the possibility of catastrophic complications, the spine surgeon should have sufficient surgical skills, experience, ensures stringent verification of the system, and never relies solely on the navigation system.

“Satellite pedicle screws” - A novel technique of pedicle screw insertion in obese patients undergoing lumbar fusion

The presence of thick sub-cutaneous fat and bulky paraspinal musculature mandates extensive surgical dissection in obese patients undergoing open Transforaminal lumbar interbody fusion surgery. Securing a ‘converging’ pedicle screw trajectory becomes difficult by the counterforces of the erector spinae muscles and thick sub-cutaneous fat in obese patients, especially at the L5-S1 level. We describe the use of a limited standard posterior midline exposure and a separate, far lateral ‘satellite’ incision to insert pedicle screws in an optimal trajectory in obese patients. Through proper pre-operative planning of the axial and sagittal MRI, the appropriate entry site is determined which is executed intra-operatively to insert pedicle screws freehand. Through a single 1.5 cm incision, both L5-S1 screws were inserted. Fourteen obese patients (mean BMI was 30.5 ± 1.1) received 56 satellite pedicle screws for TLIF at L5-S1 level. The mean age was 48.3 ± 9.7 years. The mean blood loss was 244.8 ± 114 ml and the mean operative time was 126.7 ± 82.8 min. In all patients, the screws were inserted as per pre-operative planning without any difficulties. All wounds healed well without wound complications. There were no screw related complications, and in the antero-posterior and lateral radiographs, there were no screw breaches. Satellite free-hand pedicle screws are safe and easily reproducible. They enable limited dissection of the main surgical wound and well-medialised converging pedicle screws in obese patients.

A Comparison of Percutaneous Pedicle Screw Accuracy Between Robotic Navigation and Novel Fluoroscopy-Based Instrument Tracking for Patients Undergoing Instrumented Thoracolumbar Surgery.

The accuracy of pedicle screws placed with instrument tracking and robotic navigation are individually comparable or superior to placement using standard fluoroscopy, however head-to-head comparisons between these adjuncts in a similar surgical population have yet to be performed. Consecutive patients undergoing percutaneous thoracic and lumbosacral spinal instrumentation were retrospectively enrolled. Instrumentation was performed using either fluoroscopy-based instrument tracking system (TrackX, TrackX Technologies) or robotic-navigation (ExcelsiusGPS, Globus Medical). Postinstrumentation computed tomography scans were graded for breach according to the Gertzbein-Robbins scale, with "acceptable" screws deemed as Grade A or B and "unacceptable" screws deemed as Grades C through E. Accuracy data was compared between both instrumentation modalities. Fifty-three patients, comprising a total of 250 screws (167 robot, 83 instrument tracking) were included. The overall accuracy between both modalities was similar, with 96.4% and 97.6% of screws with acceptable accuracy between instrument tracking and robotic navigation, respectively (I-squared 0.30, df=1, P= 0.58). Between instrument tracking and robotic navigation, 92.8% and 95.8% of screws received Grade A, 3.6% and 1.8% a Grade B, 1.2% and 1.2% a Grade C, 1.2% and 0.6% a Grade D, and 1.2% and 0.6% a Grade E, respectively. The robot was abandoned intraoperatively in 2 cases due to unrecoverable registration inaccuracy or software failure, leading to abandonment of 8 potential screws (4.8%). In a similar patient population, there is a similarly high degree of instrumentation accuracy between fluoroscopy-based instrument tracking and robotic navigation. There is a rare chance for screw breach with either surgical adjunct.

Clinical Significance of Lateral Pedicle Screw Malposition in Lumbar Spine Fusion.

Retrospective cohort study. Our objective was to determine whether lateral pedicle screw breach affects fusion rates and patient-reported outcomes in lumbar fusion surgery. Although lateral pedicle screw malposition is considered relatively benign, few studies have focused specifically on clinical outcomes or fusion rates associated with lateral screw malposition. Twelve-month postoperative computed tomography scans were reviewed for lateral breach, severity of breach, and fusion status. Patients with lateral breach were compared with patients with no breach. Outcome measures included Numerical Pain Rating Scale for back and leg pain, Oswestry Disability Index, and SF-36 physical function (SF-36 PF). Multivariable linear and logistic regression and were adjusted for age, procedure, level, and/or baseline pain score. Forty-five patients (31%) demonstrated 1 or more lateral breaches as compared with 99 patients without breach. After adjusting for baseline scores and fusion level, patients with 2 or more screw breaches experienced SF-36 PF score improvements that were 3.43 points less ( P =0.016) than patients with no lateral breach. After adjusting for baseline Numerical Pain Rating Scale, there was also a significant decrease in the odds of achieving minimally clinical important difference in back pain relief in these patients. There was no observed effect of lateral breach on the odds of successful fusion. The current study did not observe an association between laterally malpositioned pedicle screws and nonunion. However, results are consistent with a negative effect on SF-36 PF scores and self-reported back pain at 12 months.

Preliminary experience with a novel facet-based lateral mass drill guide for the placement of lateral mass screws compared to freehand technique: a cadaveric study

BACKGROUND CONTEXTLateral mass screw fixation is the standard for posterior subaxial cervical fixation. Several freehand surgical techniques for placing lateral mass screws have been described which rely on anatomical landmarks and surgeon mastery of the technique to safely place screws. The accuracy of these freehand techniques is inherently variable and can be influenced by a surgeon's level of clinical experience. A novel technique was developed that utilizes the plane of the facet joint to create lateral mass screw pilot holes parallel with the joint line to improve the safety and accuracy of lateral mass screw placement regardless of experience. PURPOSETo assess the safety and accuracy of lateral mass screw placement using a novel lateral mass drill guide instrument (LM Guide), compared to standard freehand technique. STUDY DESIGNRandomized cadaveric study utilizing multiple surgeon evaluators to compare the safety and accuracy of guided cervical lateral mass placement compared to traditional freehand techniques. MATERIALS AND METHODSLateral mass screws were placed from C3 to C7 in 20 cadaver specimens by 8 spine surgeons of varying levels of clinical experience (4 attendings, 4 fellows). Screws were placed bilaterally using standard anatomic landmarks (“freehand”) randomly allocated on one side and using the LM Guide on the other. Cadaveric specimens were imaged with high-resolution CT to assess screw placement. Zone grading for safety was conducted based on screw tip position and clinical severity of screw breach was based on proximity to surrounding neurovascular anatomy. Screws were graded as safe, at-risk, or critical, with at-risk and critical screws considered malpositioned. To assess the accuracy of screw trajectory placed using the LM Guide compared to freehand, sagittal screw angle was measured and compared to an “ideal” screw path parallel to the facet joint line. Freehand and LM Guide groups were compared using Pearson's chi-square correlation. RESULTSScrew placement using the LM guide yielded a significantly lower rate of screw malpositioning, with 7 of 91 (7.7%) compared with 18 of 99 (18.2%) screws placed in the At-Risk or Critical Zones, p<.05. Of the 91 screws inserted using the LM Guide, 84 (92.3%) were in the Safe Zone, 7 (7.7%) were At-Risk, and 0 were in Critical zones. There was no incidence of neural or transverse foramen breaches with the LM Guide. In comparison, for the 99 screws inserted freehand, 81 (81.8%) were Safe, 14 (14.1%) were At-Risk, and 4 (4.1%) were in Critical zones. The 4 Critical zone freehand screw breaches included 1 neural foramen breach, 2 transverse foramen breaches, and 1 facet breach. The LM Guide also resulted in higher accuracy of screw trajectory, as indicated by a significant reduction in sagittal screw angle compared with freehand, p<.01. Notably, in the less-experienced surgeon cohort, the LM Guide significantly reduced the sagittal screw angle and resulted in no critical screw breaches compared to 3 critical breaches with freehand technique suggesting there might be a benefit in decreasing the learning curve associated with lateral mass screw placement. CONCLUSIONSLateral mass screw placement with a novel LM Guide that uses the facet joint to control screw trajectory improved the accuracy and reproducibility of screw placement with a significant reduction in screw breach rate and sagittal screw angle compared to freehand techniques regardless of surgeon experience level. CLINICAL SIGNIFICANCEThe inherent variability of freehand lateral mass screw placement can increase the risk of clinical complications associated with screw malpositioning. The technique presented in this cadaveric study may be a viable alternative to standard freehand technique that can improve the overall safety of lateral mass screw placement.

Reduction in Radiation Exposure in Minimally Invasive Pedicle Screw Placement Using a Tubular Retractor: A Pilot Study

Percutaneous pedicle screw (PPS) placement is a minimally invasive spinal procedure that has been rapidly adopted over the last decade. However, PPS placement has elicited fear of increased radiation exposure from some surgeons, medical staff, and patients. This is because PPS placement is performed using a K-wire, and the operator must perform K-wire insertion into the pedicle under fluoroscopy. In order to prevent erroneous insertion, there are many occasions when direct insertion is required during radiation exposure, and the amount of radiation exposure to hands and fingers in particular increases. Although these problems are being addressed by navigation systems, these systems are still expensive and not widely available. Attempts have been made to address this situation using instrumentation commonly used in spinal surgery. First, it was considered to visualize anatomical bone markers using a tubular retractor and a microscope. In addition, the use of a self-drilling pin was adopted to locate the pedicle in a narrower field of view. Based on these considerations, a minimally invasive and highly accurate pedicle screw placement technique was developed while avoiding direct radiation exposure. This study evaluated radiation exposure and accuracy of pedicle screw placement using this new procedure in one-level, minimally invasive, transforaminal lumbar interbody fusion (MIS-TLIF). Data were collected retrospectively to review pedicle screw placement in single-level MIS TLIFs using a tubular retractor under a microscope. The total fluoroscopy time, radiation dose, and screw placement accuracy were reviewed. Extension of operating time was also evaluated. Twenty-four patients underwent single-level MIS TLIFs, with placement of 96 pedicle screws. There were 15 females and 9 males, with an average age of 64.8 years and a mean body mass index of 25.5 kg/m2. The mean operating time was 201.8 min. The mean fluoroscopic time was 26.8 s. The mean radiation dose of the area dose product was 0.0706 mGy∗m2. The mean radiation dose of air kerma was 6.0 mGy. The mean radiation dose of the entrance skin dose was 11.31 mGy. Postoperative computed tomography scans demonstrated 93 pedicle screws confined to the pedicle (97%) and three pedicle screw breaches (3.2%; two lateral, one medial). A patient with screw deviation of the medial pedicle wall developed right-foot numbness necessitating reoperation. There were no complications after reoperation. The average added time with this combined procedure was 39 min (range 16-69 min) per patient. This novel pedicle screw insertion technique compares favorably with other reports in terms of radiation exposure reduction and accuracy and is also useful from the viewpoint of avoiding direct radiation exposure to hands and fingers. It is economical because it uses existing spinal surgical instrumentation.

A standardized method of measuring screw breach on postoperative computed tomography scans following percutaneous fixation of the posterior pelvic ring.

To assess the reliability of a standardized measurement of screw breach on postoperative computed tomography (CT) scans following percutaneous fixation of the posterior pelvic ring. Three orthopedic trauma surgeons independently utilized a standardized method of measuring posterior pelvic ring screw breaches on post-operative CT scan images. Breaches were measured as a continuous variable on sagittal images reformatted to be perpendicular to the screw on axial images. The inter-rater and intra-rater reliability of screw breach distance measurements was assessed. Measurements were performed on 42 screws in 20 patients. Screw types included S1-iliosacral (IS) (n = 16), S1-transsacral (TS) (n = 8), S2-IS (n = 2), and S2-TS (n = 16). Patients with varying degrees ofscrew breacheswere chosen to test measurements across breach severities, including0mm (n = 10), ≤ 2mm (n = 12), > 2 to 4mm (n = 11), and > 4mm (n = 9). The mean difference and 95% confidence interval (CI) between screw breach measurements between the three surgeons was - 0.13mm (CI - 0.48 to 0.20), 0.05mm (CI - 0.6 to 0.7), and 0.18mm (CI - 0.47 to 0.85), respectively. The inter-rater reliability of the measurements was considered excellent (intraclass correlation coefficient (ICC), 0.93). The mean intra-rater reliability for the observers was considered good (ICC 88.5, CI 82 to 95). This simple standardized method of measuring screw breaches had excellent inter-rater reliability and would support comparisons of screw breach severity across studies. Level III.

Defining Sacral Dysmorphism: What Size Corridor Precludes Transsacral Screw Placement.

To determine what size S1-transsacral (TS) corridor is amenable to TS screw placement, as this is commonly used to identify sacral dysmorphism, and to determine if gender, ethnicity, or screw breach is associated with narrow corridors. Retrospective review. Urban level-1 trauma center. Two hundred ninety patients with pelvic ring injuries and preoperative computed tomography (CT) scans. Percutaneous posterior pelvic ring fixation. The width of the S1-TS corridor was measured on the axial (inlet) and coronal (outlet) reformatted CT images. Patients with S1-TS screw fixation and postoperative CT scans were identified. Corridor size, gender, ethnicity, and screw breach were documented. S1-TS screws were placed in 55 of the 290 patients. No S1-TS screws were placed in corridors less than 8 mm. Corridors of &lt;8 mm were present in 114 (39%) of the 290 patients and were not associated with gender or ethnicity. S1-TS screws placed in small (&lt;10 mm) versus large (≥10 mm) corridors did not have a detectable difference in screw breaches (5 of 8, 62% versus 19 of 47 40%; difference, 22%, 95% confidence interval -14% to 52%) or median (interquartile range) screw breach distance [3 mm (2.5-4.8) versus 3 mm (1.2-4.8); difference, 0.9 mm; confidence interval -1.6 to 2.2]. These data are useful for the standardization of sacral dysmorphism reporting based on corridor size. Screw breaches were common irrespective of TS corridor size, emphasizing the small degree of error allowed by this procedure. Prognostic Level III. See Instructions for Authors for a complete description of levels of evidence.

Risk factors for screw breach and iatrogenic nerve injury in percutaneous posterior pelvic ring fixation

BackgroundPercutaneous screw fixation of the posterior pelvic ring is technically demanding and can result in cortical breach. The purpose of this study was to examine risk factors for screw breach and iatrogenic nerve injury. MethodsA retrospective review at a single level-one trauma center identified 245 patients treated with 249 screws for pelvic ring injuries with postoperative computed tomography (CT) scans. Cortical screw breach, iatrogenic nerve injury, and associated risk factors were evaluated. ResultsThere were 86 (35%) breached screws. The breach rate was similar between screw types (33% S1-iliosacral (S1-IS), 44% S1-transsacral (S1-TS), 31% S2-IS, and 30% S2-TS) and was not associated with patient characteristics, Tile C injuries, or corridor size or angle. The overall rate of screw revision for screw malpositioning was 1.2% (3/249). Iatrogenic nerve injuries occurred in 8 (3.2%) of the 249 screws. Screws that caused iatrogenic nerve injuries had greater screw breach distances (5.4 vs. 0 mm, MD 5, CI 2.3 to 8.7, p < 0.0001), were more likely to be S1-IS screws (88% vs. 47%, PD 40%, CI 7 to 58%, p = 0.006), more likely to be placed in Tile C injuries (75% vs. 44%, PD 31%, CI -3 to 55%, p = 0.04), and there was a trend for having a screw corridor size <10 mm (75% vs. 47%, PD 28, CI -6 to 52%, p = 0.06). Of the 7 iatrogenic nerve injuries adjacent to screw breaches, two nerve injuries recovered after screw removal, three recovered with screw retention, and two did not recover with screw retention. ConclusionScrew breaches were common and iatrogenic nerve injuries were more likely with S1-IS screws. Surgeons should maintain a high degree of caution when placing these screws and consider removal of any breached screw associated with nerve injury.

Freehand S2-Alar-Iliac Screw Placement Technique in Lumbosacral Spinal Tumors: A Preliminary Study.

ObjectiveS2‐alar‐iliac (S2AI) screw technique is widely used in spinal surgery, but it is rarely seen in the field of spinal tumors. The aim of the study is to report the preliminary outcomes of the freehand S2AI screw fixation after lumbosaral tumor resection.MethodsThe records of patients with lumbosacral tumor who underwent S2AI screw fixation between November 2016 to November 2020 at our center were reviewed retrospectively. Outcome measures included operative time, blood loss, complications, accuracy of screws, screw breach, and overall survival. Mean ± standard deviation or range was used to present continuous variables. Kaplan–Meier curve was used to present postoperative survival.ResultsA total of 23 patients were identified in this study, including 12 males and 11 females, with an average age of 47.3 ± 14.5 (range,15–73). The mean operation time was 224.6 ± 54.1 (range, 155–370 min). The average estimated blood loss was 1560.9 ± 887.0 (600–4000 ml). A total of 46 S2AI screws were implanted by freehand technique. CT scans showed three (6.5%) screws had penetrated the iliac cortex, indicating 93.5% implantation accuracy rate. No complications of iatrogenic neurovascular or visceral structure were observed. The average follow‐up time was 31.6 ± 15.3 months (range, 13–60 months). Two patients' postoperative plain radiography showed lucent zone around the screw. One patient underwent reoperation for wound delayed infection. At the latest follow‐up, eight patients had tumor‐free survival, 11 had survival with tumor, and four died of disease.ConclusionThe freehand S2AI screw technique is reproducible, safe, and reliable in the management of lumbosacral spinal tumors.