Combined vertebroplasty and pedicle screw insertion for vertebral consolidation: feasibility and technical considerations

PURPOSE

To assess the feasibility and technical accuracy of performing pedicular screw placement combined with vertebroplasty in the radiological setting.

METHODS

Patients who underwent combined vertebroplasty and pedicle screw insertion under combined computed tomography and fluoroscopic guidance in 4 interventional radiology centers from 2018 to 2023 were retrospectively assessed. Patient demographics, vertebral lesion type, and procedural data were analyzed. Strict intra-pedicular screw positioning was considered as technical success. Pain score was assessed according to the Visual Analogue Scale before the procedure and in the 1-month follow-up consultation.

RESULTS

Fifty-seven patients (38 men and 19 women) with a mean age of 72.8 (SD = 11.4) years underwent a vertebroplasty associated with pedicular screw insertion for the treatment of traumatic fractures (29 patients) and neoplastic disease (28 patients). Screw placement accuracy assessed by post-procedure CT scan was 95.7% (89/93 inserted screws). A total of 93 pedicle screw placements (36 bi-pedicular and 21 unipedicular) in 32 lumbar, 22 thoracic, and 3 cervical levels were analyzed. Mean reported procedure time was 48.8 (SD = 14.7) min and average injected cement volume was 4.4 (SD = 0.9) mL. A mean VAS score decrease of 5 points was observed at 1-month follow-up (7.7, SD = 1.3 versus 2.7, SD = 1.7), p < .001.

CONCLUSION

Combining a vertebroplasty and pedicle screw insertion is technically viable in the radiological setting, with a high screw positioning accuracy of 95.7%.

Pressure Dynamics on Intervertebral Disc Cages in Transforaminal Lumbar Interbody Fusion: A Cadaver Study

OBJECTIVE

This study aimed to quantify the change in pressure on the cage during compression manipulation in lumbar interbody fusion. While the procedure involves applying compression between pedicle screws to press the cage against the endplate, the exact compression force remains elusive. We hypothesize that an intact facet joint might serve as a fulcrum, potentially reducing cage pressure.

METHODS

Pressure on the intervertebral disc cage was measured during compression manipulation in 4 donor cadavers undergoing lumbar interbody fusion. Unilateral facetectomy models with both normal and parallel compression and bilateral facetectomy models were included. A transforaminal lumbar interbody fusion cage with a built-in load cell measured the compression force.

RESULTS

Pressure data from 14 discs indicated a consistent precompression pressure average of 68.16 N. Following compression, pressures increased to 125.99 N and 140.84 N for normal and parallel compression postunilateral facetectomy, respectively, and to 154.58 N and 150.46 N for bilateral models. A strong linear correlation (correlation coefficient: 0.967, P < 0.0001) between precompression and postcompression pressures emphasized the necessity of sufficient precompression pressure for achieving desired postcompression outcomes. None of the data showed a decrease in compression force to the cage with the compression maneuver.

CONCLUSIONS

Both normal and parallel compression maneuvers effectively increased the pressure on the cage, irrespective of the facet joint resection status. Compression manipulation consistently enhanced compressive force on the cage. However, when baseline pressure is low, the manipulation might not yield significant increases in compression force. This underlines the essential role of meticulous precompression preparation in enhancing surgical outcomes.

Implant density in adolescent idiopathic scoliosis: a meta-analysis of clinical and radiological outcomes

BACKGROUND

Adolescent idiopathic scoliosis (AIS) affects 1-3% of adolescents, and treatment approaches, including the density of constructs in surgical fusion, vary among orthopedic surgeons. Studies have sought to establish whether high-density or low-density constructs offer superior clinical and radiological outcomes, yet conclusive results are lacking. This meta-analysis aims to provide a definitive answer to the controversial and ambiguous question surrounding the efficacy of different pedicle screw densities in treating AIS.

METHODS

PubMed, Cochrane, and Google Scholar (page 1-20) were searched till December 2023. The studied outcomes were Major Cobb angle, major curve correction, lumbar curve, kyphosis (T5-T12), lumbar lordosis, coronal balance, LIV Tilt angle, TAV translation, LAV translation, apical trunk rotation, trunk shift, SRS-22, operative time, blood loss, complications and cost.

RESULTS

Twenty-four studies (total of 1985 patients, 1045 in LD group and 940 in HD group) were included in this meta-analysis. A statistically significant better improvement in ATR (p = 0.02) and LIV tilt angle (p = 0.02) was seen in the high-density group. On the other hand, longer operative time (p = 0.002), blood loss (p = 0.0004) and costs (p = 0.02) were seen in the high-density group. No difference was seen in the remaining radiographic and clinical outcomes between both surgeries.

CONCLUSION

Both low-density (LD) and high-density (HD) screw constructs show comparable and satisfactory radiographic and QOL for AIS patients. Furthermore, HD constructs had increased costs, operative time, and blood loss associated. However, a definitive conclusion cannot be made and more studies taking into account multiple additional variables are necessary to do so.

Instrumentation of hypoplastic pedicles with patient-specific guides

PURPOSE

Hypoplastic pedicles of the thoracolumbar spine (<5 mm diameter) are often found in syndromic deformities of the spine and pose a challenge in pedicle screw instrumentation. 3D-printed patient-specific guides might help overcome anatomical difficulties when instrumenting pedicles with screws, thereby reducing the necessity for less effective fixation methods such as hooks or sublaminar wires. In this study, the surgical feasibility and clinical outcome of patients with hypoplastic pedicles following pedicle screw instrumentation with 3D-printed patient-specific guides were assessed.

METHODS

Hypoplastic pedicles were identified on preoperative computed tomography (CT) scans in six patients undergoing posterior spinal fusion surgery between 2017 and 2020. Based on these preoperative CT scans, patient-specific guides were produced to help with screw instrumentation of these thin pedicles. Postoperatively, pedicle-screw-related complications or revisions were analyzed.

RESULTS

93/105 (88.6%) pedicle screws placed with patient-specific guides were instrumented. 62/93 (66.7%) of these instrumented pedicles were defined as hypoplastic with a mean width of 3.07 mm (SD  ±0.98 mm, 95% CI [2.82-3.32]). Overall, 6 complications in the 62 hypoplastic pedicles (9.7%) were observed and included intraoperatively managed 4 cerebrospinal fluid leaks, 1 pneumothorax and 1 delayed revision due to 2 lumbar screws (2/62, 3.3%) impinging the L3 nerve root causing a painful radiculopathy. The mean follow-up time was 26.7 (SD  ±11.7) months. Complications were only noted when the pedicle-width-to-screw-diameter ratio measured less than 0.62.

CONCLUSION

Patient-specific 3D-printed guides can aid in challenging instrumentation of hypoplastic pedicles in the thoracolumbar spine, especially if the pedicle-width-to-screw-diameter ratio is greater than 0.62.

Superior metal artifact reduction of tin-filtered low-dose CT in imaging of lumbar spinal instrumentation compared to conventional computed tomography

OBJECTIVE

To compare the image quality of low-dose CT (LD-CT) with tin filtration of the lumbar spine after metal implants to standard clinical CT, and to evaluate the potential for metal artifact and dose reduction.

MATERIALS AND METHODS

CT protocols were optimized in a cadaver torso. Seventy-four prospectively included patients with metallic lumbar implants were scanned with both standard CT (120 kV) and tin-filtered LD-CT (Sn140kV). CT dose parameters and qualitative measures (1 = worst,4 = best) were compared. Quantitative measures included noise, signal-to-noise ratio (SNR), contrast-to-noise ratio (CNR), and the width and attenuation of the most prominent hypodense metal artifact. Standard CT and LD-CT were assessed for imaging findings.

RESULTS

Tin-filtered LD-CT was performed with 60% dose saving compared to standard CT (median effective dose 3.22 mSv (quartile 1-3: 2.73-3.49 mSv) versus 8.02 mSv (6.42-9.27 mSv; p < .001). Image quality of CT and tin-filtered low-dose CT was good with excellent depiction of anatomy, while image noise was lower for CT and artifacts were weaker for tin-filtered LD-CT. Quantitative measures also revealed increased noise for tin-filtered low-dose CT (41.5HU), lower SNR (2) and CNR (0.6) compared to CT (32HU,3.55,1.03, respectively) (all p < .001). However, tin-filtered LD-CT performed superior regarding the width and attenuation of hypodense metal artifacts (2.9 mm and -767.5HU for LD-CT vs. 4.1 mm and -937HU for CT; all p < .001). No difference between methods was observed in detection of imaging findings.

CONCLUSION

Tin-filtered LD-CT with 60% dose saving performs comparable to standard CT in detection of pathology and surgery related complications after lumbar spinal instrumentation, and shows superior metal artifact reduction.

Intraoperative anteroposterior and oblique fluoroscopic views for detection of mediolateral pedicle screw misplacement in the lumbar spine: a randomized cadaveric study

BACKGROUD CONTEXT

Pedicle screws are commonly used for posterior fixation of the lumbar spine. Inaccuracy of screw placement can lead to disastrous complications.

PURPOSE

As fluoroscopic assisted pedicle screw instrumentation is the most frequently used technique, the aim of this study was to assess the specificity, sensitivity and accuracy of intraoperative fluoroscopy to detect mediolateral screw malpositioning. We also analyzed whether the addition of an oblique view could improve these parameters.

STUDY DESIGN

On 12 human cadavers, 138 pedicle screws were placed intentionally either with 0 to 2 mm (75 screws), with 2 to 4 mm (six medial and 12 lateral screws) and with >4 mm (22 medial and 23 lateral screws) breach of the pedicle from Th12 to L5.

METHODS

Three experienced spine surgeons evaluated the screw positioning in fluoroscopic AP views and 4 weeks later in AP views and additional oblique views. The surgeons' interpretation was compared with the effective screw position on postoperative CT scans.

RESULTS

Pedicle breaches greater than 2 mm were detected in 68% with AP views and in 67% with additional oblique views (p=.742). The specificity of AP views was 0.86 and 0.93 with additional oblique views (p=<.01). The accuracy was 0.78 with AP views and 0.81 with AP + oblique views (p=.114). There was a substantial inter-reader agreement (Fleiss's kappa: 0.632).

CONCLUSIONS

Fluoroscopic screening of pedicle screw misplacement has a limited sensitivity. Adding an oblique view improves specificity but not sensitivity and accuracy in detecting screw malpositions.

CLINICAL SIGNIFICANCE

When in doubt of a screw malpositioning, other modalities than a fluoroscopic assisted pedicle screw instrumentation such as intraoperative CT imaging or an intraoperative exploration of the screw trajectory must be evaluated.

Freehand power-assisted pedicle screw placement in scoliotic patients: results on 5522 consecutive pedicle screws

Pedicle screws is the current gold standard in spine surgery, achieving a solid tricolumnar fixation which is unreachable by wires and hooks. The freehand technique is the most widely adopted for pedicle screws placing. While freehand technique has been classically performed with manual tools, there has been a recent trend toward the use of power tools. However, placing a pedicle screw remains a technically demanding procedure with significant risk of complications. The aim of this article is to retrospectively evaluate safety and accuracy of free-hand power-assisted pedicle screw placement in a cohort of patients who underwent correction and fusion surgery for scoliosis (both idiopathic and non-idiopathic) in our department. A retrospective review of all patients with scoliosis who underwent surgery and received a postoperative CT scan in our department in a 9-year period was undertaken. Screw density, number and location of pedicle screws were measured using pre and postoperative full-length standing and lateral supine side-bending radiographs. Then, postoperative CT scan was used to assess the accuracy of screw placement according to Gertzbein-Robbins scale. Malpositioned screws were divided according to their displacement direction. Finally, intra and postoperative neurological complications and the need for revision of misplaced screws were recorded. A total of 205 patients were included, with a follow-up of 64.9 ± 38.67 months. All constructs were high density (average density 1.97 ± 0.04), and the average number of fusion levels was 13.72 ± 1.97. A total of 5522 screws were placed: 5308 (96.12%) were grade A, 141 (2.5%) grade B, 73 (1.32%) grade C. Neither grade D nor grade E trajectories were found. The absolute accuracy (grade A) rate was 96.12% (5308/5522) and the effective accuracy (within the safe zone, grade A + B) was 98.6% (5449/5522). Of the 73 misplaced screws (grade C), 59 were lateral (80.80%), 8 anterior (10.95%) and 6 medial (8.22%); 58 were in convexity, while 15 were in concavity (the difference was not statistically significant, p = 0.33). Intraoperatively, neither neurological nor vascular complications were recorded. Postoperatively, 4 screws needed revision (0.072% of the total): Power-assisted pedicle screw placing may be a safe an accurate technique in the scoliosis surgery, both of idiopathic and non-idiopathic etiology. Further, and higher quality, research is necessary in order to better assess the results of this relatively emerging technique.

Robotic-Assisted Spine Surgery: Role in Training the Next Generation of Spine Surgeons

OBJECTIVE

This study aimed to assess the degree of interest in robot-assisted spine surgery (RASS) among residents and to investigate the learning curve for beginners performing robotic surgery.

METHODS

We conducted a survey to assess awareness and interest in RASS among young neurosurgery residents. Subsequently, we offered a hands-on training program using a dummy to educate one resident. After completing the program, the trained resident performed spinal fusion surgery with robotic assistance under the supervision of a mentor. The clinical outcomes and learning curve associated with robotic surgery were then analyzed.

RESULTS

Neurosurgical residents had limited opportunities to participate in spinal surgery during their training. Despite this, there was a significant interest in the emerging field of robotic surgery. A trained resident performed RASS under the supervision of a senior surgeon. A total of 166 screw insertions were attempted in 28 patients, with 2 screws failing due to skiving. According to the Gertzbein-Robbins classification, 85.54% of the screws were rated as grade A, 11.58% as grade B, 0.6% as grade C, and 1.2% as grade D. The clinical acceptance rate was approximately 96.99%, which is comparable to the results reported by senior experts and time per screw statistically significantly decreased as experience was gained.

CONCLUSION

RASS can be performed with high accuracy within a relatively short timeframe, if residents receive adequate training.

Spondylodiscitis instrumented fusion, a prospective case series on a standardized neurosurgical protocol with long term follow up

PURPOSE

To investigate the fusion construct properties, construct length, intervertebral prosthesis (IVP) selection, bone grafting methods, complications management, and follow-up outcomes of spondylodiscitis fusion.

METHOD

This case series was conducted in Al-Zahra University referral hospital from March 2016 to November 2021. All the surgery-eligible patients were enrolled. Those who did not participate or failed the neurosurgical intervention were excluded. A unified neurosurgical protocol was defined. After operation and follow-up, all variables were documented. IBM SPSS v.26 was used for data analysis. P-value ≤ 0.05 was considered significant.

RESULT

Ninety-two patients were reviewed in the final analysis with 65.2 % males. The mean age was 55.07 ± 14.22 years old. The most frequent level of pathology and surgery was the lumbar spine (48.9 %). Short and long constructs were almost equally used (57.6 and 42.4 %, respectively). Bone graft mixture was the dominant IVP (75 %). The most frequent persistent postoperative symptom was back pain (55.4 %), while the neurological deficits resolution rate was 76.7 %. The fusion rate was 92.3 %. Proximal junctional kyphosis incidence was 16.3 % and had a significant association with on-admission neurological symptoms, thoracic and thoracolumbar junction involvements (p < 0.05). Follow-up Oswestry disability index scores showed 44.6 % of the patients had mild or no functional disabilities. Advanced age, On-admission deficits, comorbidities, titanium cages, and poor fusion status were associated with poor functional outcomes and higher mortality rates (P < 0.05).

CONCLUSION

The introduced neurosurgical protocol could effectively achieve acceptable SD treatment, spine stabilization, and fusion with low long-term surgical complications. Autologous bone graft mixture in comparison to titanium cages showed a higher fusion rate with a lower mortality rate. Patients with older age, neurological symptoms, and comorbidities are expected to experience less favorable clinical outcomes.

Cement Augmentation of Pedicle Screw Instrumentation: A Literature Review

This literature review aimed to review the current understanding, indications, and limitations of pedicle screw instrumentation cement augmentation. Since they were first reported in the 1980s, pedicle screw cement augmentation rates have been increasing. Several studies have been published to date that describe various surgical techniques and the biomechanical changes that occur when cement is introduced through the screw-bone interface. This article provides a concise review of the uses, biomechanical properties, cost analysis, complications, and surgical techniques used for pedicle screw cement augmentation to help guide physician practices. A comprehensive review of the current literature was conducted, with key studies, and contributions from throughout history being highlighted. Patients with low bone mineral density are the most well-studied indication for pedicle screw cement augmentation. Many studies show that cement augmentation can improve pullout strength in patients with low bone mineral density; however, the benefit varies inversely with pathology severity and directly with technique. The various screw types are discussed, with each having its own mechanical advantages. Cement distribution is largely dependent on the filling method and volume of cement used. Cement composition and timing of cement use after mixing are critical considerations in practice because they can significantly alter the bone-cement and screw-cement interfaces. Overall, studies have shown that pedicle screw cement augmentation has a low complication rate and increased pullout strength, justifying its universal use in patients with a suboptimal bone-implant interface.

Simultaneous Single-Position Lateral Lumbar Interbody Fusion Surgery and Unilateral Percutaneous Pedicle Screw Fixation for Spondylolisthesis

OBJECTIVE

To evaluate the clinical and radiological efficacy of a combine of lateral single screw-rod and unilateral percutaneous pedicle screw fixation (LSUP) for lateral lumbar interbody fusion (LLIF) in the treatment of spondylolisthesis.

METHODS

Sixty-two consecutive patients with lumbar spondylolisthesis who underwent minimally invasive (MIS)-TLIF with bilateral pedicle screw (BPS) or LLIF-LSUP were retrospectively studied. Segmental lordosis angle (SLA), lumbar lordosis angle (LLA), disc height (DH), slipping percentage, the cross-sectional areas (CSA) of the thecal sac, screw placement accuracy, fusion rate and foraminal height (FH) were used to evaluate radiographic changes postoperatively. Visual analogue scale (VAS) and Oswestry Disability Index (ODI) were used to evaluate the clinical efficacy.

RESULTS

Patients who underwent LLIF-LSUP showed shorter operating time, less length of hospital stay and lower blood loss than MIS-TLIF. No statistical difference was found between the 2 groups in screw placement accuracy, overall complications, VAS, and ODI. Compared with MIS-TLIF-BPS, LLIF-LSUP had a significant improvement in sagittal parameters including DH, FH, LLA, and SLA. The CSA of MIS-TLIF-BPS was significantly increased than that of LLIF-LSUP. The fusion rate of LLIF-LSUP was significantly higher than that of MIS-TLIF-BPS at the follow-up of 3 months postoperatively, but there was no statistical difference between the 2 groups at the follow-up of 6 months, 9 months, and 12 months.

CONCLUSION

The overall clinical outcomes and complications of LLIF-LSUP were comparable to that of MIS-TLIF-BPS in this series. Compared with MIS-TLIF-BPS, LLIF-LSUP for lumbar spondylolisthesis represents a significantly shorter operating time, hospital stay and lower blood loss, and demonstrates better radiological outcomes to maintain lumbar lordosis, and reveal an overwhelming superiority in the early fusion rate.

Three-Dimensional Quantitative Assessment of Pedicle Screw Accuracy in Clinical Utilization of a New Robotic System in Spine Surgery: A Multicenter Study

OBJECTIVE

The objective of this study was to evaluate the accuracy of pedicle screw placement in patients undergoing percutaneous pedicle screw fixation with robotic guidance, using a newly developed 3-dimensional quantitative measurement system. The study also aimed to assess the clinical feasibility of the robotic system in the field of spinal surgery.

METHODS

A total of 113 patients underwent pedicle screw insertion using the CUVIS-spine pedicle screw guide system (CUREXO Inc.). Intraoperative O-arm images were obtained, and screw insertion pathways were planned accordingly. Image registration was performed using paired-point registration and iterative closest point methods. The accuracy of the robotic-guided pedicle screw insertion was assessed using 3-dimensional offset calculation and the Gertzbein-Robbins system (GRS).

RESULTS

A total of 448 screws were inserted in the 113 patients. The image registration success rate was 95.16%. The average error of entry offset was 2.86 mm, target offset was 2.48 mm, depth offset was 1.99 mm, and angular offset was 3.07°. According to the GRS grading system, 88.39% of the screws were classified as grade A, 9.60% as grade B, 1.56% as grade C, 0.22% as grade D, and 0.22% as grade E. Clinically acceptable screws (GRS grade A or B) accounted for 97.54% of the total, with no reported neurologic complications.

CONCLUSION

Our study demonstrated that pedicle screw insertion using the novel robot-assisted navigation method is both accurate and safe. Further prospective studies are necessary to explore the potential benefits of this robot-assisted technique in comparison to conventional approaches.

Spectral metal artifact reduction after posterior spinal fixation in photon-counting detector CT datasets

PURPOSE

To investigate the usefulness of virtual monoenergetic image (VMI) reconstructions derived from scans on a novel photon-counting detector CT (PCD-CT) for artifact reduction in patients after posterior spinal fixation.

METHODS

This retrospective cohort study included 23 patients status post posterior spinal fixation. Subjects were scanned on a novel PCD-CT (NAEOTOM Alpha, Siemens Healthineers, Erlangen, Germany) as part of routine clinical care. 14 sets of VMI reconstructions were derived in 10 keV increments for the interval 60-190 keV. The mean and the standard deviation (SD) of CT-values in 12 defined locations around a pair of pedicle screws on one vertebral level and the SD of homogenous fat were measured and used to calculate an artifact index (AIx).

RESULTS

Averaged over all regions, the lowest AIx was observed at VMI levels of 110 keV (32.5 (27.8-37.9)) which was significantly different from those of VMIs ≤ 90 keV (p < 0.001) or ≥160 keV (p < 0.015), respectively. Overall AIx values increased in both lower- and higher-keV levels. Regarding individual locations, either a monotonous AIx-decrease for increasing keV values or an AIx-minimum in intermediate-keV levels (100-140 keV) was found. In locations adjacent to larger metal parts, the increase of AIx values at the high-end of the keV spectrum was mainly explained by a reappearance of streak artifacts.

CONCLUSION

Our findings suggest that 110 keV is the optimal VMI setting for overall artifact suppression. In specific anatomical regions, however, slight adjustments towards higher-keV levels may provide better results.

Perioperative Clinical Features and Long-term Prognosis After Oblique Lateral Interbody Fusion (OLIF), OLIF With Anterolateral Screw Fixation, or OLIF With Percutaneous Pedicle Fixation: A Comprehensive Treatment Strategy for Patients With Lumbar Degenerative Disease

OBJECTIVE

To compare the efficacy of oblique lateral interbody fusion (OLIF), OLIF combined with anterolateral screw fixation (OLIF-AF), and OLIF combined with percutaneous pedicle screw fixation (OLIF-PF) in the treatment of single-level or 2-level degenerative lumbar disease.

METHODS

Between January 2017 and 2021, 71 patients were treated with OLIF and combined OLIF. The demographic data, clinical outcomes, radiographic outcomes, and complications were compared among the 3 groups.

RESULTS

The operative time and intraoperative blood loss in the OLIF (p<0.05) and OLIF-AF (p<0.05) groups were lower than in the OLIF-PF group. Posterior disk height improvement in the OLIF-PF group was better than in the OLIF (p<0.05) and OLIF-AF (p<0.05) groups. In terms of foraminal height (FH), the OLIF-PF group was significantly better than the OLIF group (p<0.05), but there was no significant difference between the OLIF-PF and OLIF-AF groups (p>0.05) or between the OLIF and OLIF-AF groups (p>0.05). There were no significant differences in fusion rates, the incidence of complications, lumbar lordosis, anterior disc height, and cross-sectional area among the 3 groups (p>0.05). The OLIF-PF group had significantly lower rates of subsidence than the OLIF group (p<0.05).

CONCLUSION

OLIF remains a viable option with similar patient-reported outcomes and fusion rates compared with surgeries that include lateral and posterior internal fixation while greatly reducing the financial burden, intraoperative time, and intraoperative blood loss. OLIF has a higher subsidence rate than lateral and posterior internal fixation, but most subsidence is mild and has no adverse effect on clinical and radiographic outcomes.

Detection of Common Anatomical Landmarks and Vertical Trajectories for Freehand Pedicle Screw Placement

OBJECTIVE

It is clinically important for pedicle screws to be placed quickly and accurately. Misplacement of pedicle screws results in various complications. However, the incidence of complications varies greatly due to the different professional titles of physicians and surgical experience. Therefore, physicians must minimize pedicle screw dislocation. This study aims to compare the three nail placement methods in this study, and explore which method is the best for determining the anatomical landmarks and vertical trajectories.

METHODS

This study involved 70 patients with moderate idiopathic scoliosis who had undergone deformity correction surgery between 2018 and 2021. Two spine surgeons used three techniques (preoperative computed tomography scan [CTS], visual inspection-X-freehand [XFH], and intraoperative detection [ID] of anatomical landmarks) to locate pedicle screws. The techniques used include visual inspection for 287 screws in 21 patients, preoperative planning for 346 screws in 26 patients, and intraoperative probing for 309 screws in 23 patients. Observers assessed screw conditions based on intraoperative CT scans (Grade A, B, C, D).

RESULTS

There were no significant differences between the three groups in terms of age, sex, and degree of deformity. We found that 68.64% of screws in the XFH group, 67.63% in the CTS group, and 77.99% in the ID group were placed within the pedicle margins (grade A). On the other hand, 6.27% of screws in the XFH group, 4.33% in the CTS group, and 6.15% in the ID group were considered misplaced (grades C and D). The results show that the total amount of upper thoracic pedicle screws was fewer, meanwhile their placement accuracy was lower. The three methods used in this study had similar accuracy in intermediate physicians (P > 0.05). Compared with intermediate physicians, the placement accuracy of three techniques in senior physicians was higher. The intraoperative detection group was better than the other two groups in the good rate and accuracy of nail placement (P < 0.05).

CONCLUSION

Intraoperative common anatomical landmarks and vertical trajectories were beneficial to patients with moderate idiopathic scoliosis undergoing surgery. It is an optimal method for clinical application.

Comparative effectiveness of different pedicle screw density patterns in spinal deformity correction of small and flexible operative adolescent idiopathic scoliosis: inverse probability of treatment weighting analysis

PURPOSES

An optimal pedicle screw density for spinal deformity correction in adolescent idiopathic scoliosis (AIS) remains poorly defined. We compared radiographic correction, operative time, estimated blood loss, and implant cost among different screw density patterns in operatively treated AIS patients.

METHODS

A retrospective observational cohort study of AIS patients who underwent posterior spinal fusion using all-pedicle screw instrumentation was conducted from January 2012 to December 2018. All patients were categorized into three different pedicle screw density groups: the very low density (VLD), the low density (LD), and the high density (HD) group. The comparative effectiveness between each pairwise comparison was performed under the inverse probability of the treatment weighting method to minimize the possible confounders imbalance among treatment groups. The primary endpoints in this study were the degrees of correction and deformity progression at 2 years postoperatively.

RESULTS

A total of 174 AIS patients were included in this study. The adjusted treatment effects demonstrated similar degrees of deformity correction after 2 years in the three treatment groups. However, the VLD and LD group slightly increased the curve progression at 2 years compared to the HD group by 3.9° (p = 0.005) and 3.2° (p = 0.044), respectively. Nevertheless, the limited screw density patterns (VLD and LD) significantly reduced the operative time, estimated blood loss, and implant cost per operated level.

CONCLUSION

The limited pedicle screw pattern (VLD and LD) in relatively flexible AIS spinal deformity correction results in similar coronal and sagittal radiological outcomes while reducing operative time, estimated blood loss, and implant cost compared to the high-density pedicle screw instrumentation.

Intraoperative Cone-Beam Computed Tomography Assessment of Spinal Pedicle Screws Placement Precision Is in Full Agreement with Postoperative Computed Tomography Assessment

OBJECTIVE

To assess agreement between pedicle screw placement evaluated on postoperative computed tomography (CT) and on intraoperative cone-beam CT (CBCT) and compare procedure characteristics when using first-generation and second-generation robotic C-arm systems in the hybrid operating room.

METHODS

All patients who received pedicle screws for spinal fusion at our institution between June 2009 and September 2019 and underwent intraoperative CBCT and postoperative CT were included. The CBCT and CT images were reviewed by 2 surgeons to assess the screw placement using the Gertzbein-Robbins and the Heary classifications. Intermethod agreement of screw placement classifications as well as interrater agreement were assessed using Brennan-Prediger and Gwet agreement coefficients. Procedure characteristics using first-generation and second-generation generation robotic C-arm systems were compared.

RESULTS

Fifty-seven patients were treated with 315 pedicle screws at thoracic, lumbar, and sacral levels. No screw had to be repositioned. On CBCT, accurate placement was found for 309 screws (98.1%) using the Gertzbein-Robbins classification and 289 (91.7%) using the Heary classification and on CT, these were 307 (97.4%) and 293 (93.0%), respectively. Intermethod between CBCT and CT and interrater agreements between the 2 raters were almost perfect (>0.90) for all assessment. There were no significant differences in mean radiation dose (P = 0.83) and fluoroscopy time (P = 0.82), but length of surgery using the second-generation system was estimated at 107.7 minutes (95% confidence interval, 31.9-183.5 minutes; P = 0.006) shorter.

CONCLUSIONS

Intraoperative CBCT provides accurate assessment of pedicle screw placement and enables intraoperative repositioning of misplaced screws.

When spinal instrumentation revision is not an option: Salvage vertebral augmentation with polymethylmethacrylate for mechanical complications: A systematic review

Intoduction

Mechanical complications from spinal fusion including implant loosening or junctional failure result in poor outcomes, particularly in osteoporotic patients. While the use of percutaneous vertebral augmentation with polymethylmethacrylate (PMMA) has been studied for augmentation of junctional levels to offset against kyphosis and failure, its deployment around existing loose screws or in failing surrounding bone as a salvage percutaneous procedure has been described in small case series and merits review.

Research Question

How effective and safe is the use of PMMA as a salvage procedure for mechanical complications in failed spinal fusion?.

Materials and Methods

Systematic search of online databases for clinical studies using this technique.

Results

11 studies were identified, only consisting of two case reports and nine case series. Consistent improvements were observed in pre- to post-operative VAS and with sustained improvements at final follow-up. The extra- or para-pedicular approach was the most frequent access trajectory. Most studies cited difficulties with visibility on fluoroscopy, using navigation or oblique views as a solution for this.

Discussion and Conclusions

Percutaneous cementation at a failing screw-bone interface stabilises further micromotion with reductions in back pain. This rarely used technique is manifested by a low but increasing number of reported cases. The technique warrants further evaluation and is best performed within a multidisciplinary setting at a specialist centre. Notwithstanding that underlying pathology may not be addressed, awareness of this technique may allow an effective and safe salvage solution with minimal morbidity for older sicker patients.

Accuracy and safety of 3D printed surgical guides combined with monitored guidewires for placement of cervicothoracic pedicle screws: Technical note

Subaxial cervical pedicle screws provide rigid fixation, but their placement poses an important neurovascular injury risk. 3D printed guides have successfully been used to place pedicle screws, but experience in the subaxial cervical spine is limited. We present a case of cervicothoracic dissociation after a pathological fracture due to tumour involvement of the upper thoracic spine, causing paraparesis and intense pain. The cervicothoracic junction is of difficult visualization on fluoroscopy and the patients' severe instability made navigation unreliable. 3D printed individualized guidewire guides were used to help place canulated pedicle screws from C4 to T6. We successfully report the use of impedance guidewire monitoring to prevent pedicle violation and improve procedure safety.

Complications associated with subaxial placement of pedicle screws versus lateral mass screws in the cervical spine (C2-T1): systematic review and meta-analysis comprising 4,165 patients and 16,669 screws

Lateral mass screw (LMS) and cervical pedicle screw (CPS) fixation are among the most popular techniques for posterior fusion of the cervical spine. Early research prioritized the LMS approach as the trajectory resulted in fewer neurovascular complications; however, with the incorporation of navigation assistance, the CPS approach should be re-evaluated. Our objective was to report the findings of a meta-analysis focused on comparing the LMS and CPS techniques in terms of rate of various complications with inclusion of all levels from C2 to T1. We conducted a systematic review of PubMed and EMBASE databases with final inclusion criteria focused on identifying studies that reported outcomes and complications for either the CPS or LMS technique. These studies were then pooled, and statistical analyses were performed from the cumulative data. A total of 60 studies comprising 4165 participants and 16,669 screws placed within the C2-T1 levels were identified. Within these studies, the LMS group had a significantly increased odds for lateral mass fractures (odds ratio [OR] = 43.2, 95% confidence interval [CI] = 2.62-711.42), additional cervical surgeries (OR = 5.56, 95%CI = 2.95-10.48), and surgical site infections (SSI) (OR = 5.47, 95%CI = 1.65-18.16). No other significant differences between groups in terms of complications were identified. Within the subgroup analysis of navigation versus non-navigation-guided CPS placement, no significant differences were identified for individual complications, although collectively significantly fewer complications occurred with navigation (OR = 5.29, 95%CI = 2.03-13.78). The CPS group had significantly fewer lateral mass fractures, cervical revision surgeries, and SSIs. Furthermore, navigation-assisted CPS placement was associated with a significant reduction in complications overall.

Virtual and Augmented Reality in Spine Surgery: A Systematic Review

BACKGROUND

Augmented reality (AR) and virtual reality (VR) implementation in spinal surgery has expanded rapidly over the past decade. This systematic review summarizes the use of AR/VR technology in surgical education, preoperative planning, and intraoperative guidance.

METHODS

A search query for AR/VR technology in spine surgery was conducted through PubMed, Embase, and Scopus. After exclusions, 48 studies were included. Included studies were then grouped into relevant subsections. Categorization into subsections yielded 12 surgical training studies, 5 preoperative planning, 24 intraoperative usage, and 10 radiation exposure.

RESULTS

VR-assisted training significantly reduced penetration rates or increased accuracy rates compared to lecture-based groups in 5 studies. Preoperative VR planning significantly influenced surgical recommendations and reduced radiation exposure, operating time, and estimated blood loss. For 3 patient studies, AR-assisted pedicle screw placement accuracy ranged from 95.77% to 100% using the Gertzbein grading scale. Head-mounted display was the most common interface used intraoperatively followed by AR microscope and projector. AR/VR also had applications in tumor resection, vertebroplasty, bone biopsy, and rod bending. Four studies reported significantly reduced radiation exposure in AR group compared to fluoroscopy group.

CONCLUSIONS

AR/VR technologies have the potential to usher in a paradigm shift in spine surgery. However, the current evidence indicates there is still a need for 1) defined quality and technical requirements for AR/VR devices, 2) more intraoperative studies that explore usage outside of pedicle screw placement, and 3) technological advancements to overcome registration errors via the development of an automatic registration method.

Pedagogy in spine surgery: developing a free and open-access virtual simulator for lumbar pedicle screws placement

PURPOSE

Simulators for pedicle screws placement range from basic sawbones to virtual reality. Yet, they remain expensive and often require specific devices. No free online virtual simulator has yet been developed. The goal was to design a freely accessible Web-based simulator.

METHODS

The computer simulator consisted of a lumbar spine, a red box hiding the pedicles and five pairs of screws. After inserting the screws, the red box was removed to assess their position. A validation study was conducted with 24 medical students randomized into a simulation and a control group. All had a basic course on pedicle screws. The 12 simulation group students performed two sessions on computer. All 24 students then conducted a final common step on sawbones. The number of misplaced screws, types of breaches, and simulation times were analyzed.

RESULTS

In the final sawbones simulation, 96 real screws were studied. Control group misplaced 50% of their screws compared with only 20.8% in the simulation group (p < 0.05). More careful, simulation group students were slower to insert their real screws. Over the two computer simulations, the rate of misplaced screws decreased (12.5% vs. 38.3%), showing a good handling of the simulator. Students were able to analyze and correct their pedicle breaches.

CONCLUSION

This tool is the first free online lumbar pedicle screws simulator. Simulation helped students to better position the final real screws on sawbones. This project showed it was possible to create a free educational tool with no special equipment.

LEVEL OF EVIDENCE

Level 3.

[Robot-assisted pedicle screw placement]

OBJECTIVE

Pedicle screw-based posterior instrumentation of the spine.

INDICATIONS

Instability of the spine due to trauma, infection, degenerative spinal disease or tumor.

CONTRAINDICATIONS

None.

SURGICAL TECHNIQUE

Robot-assisted navigated pedicle screw placement.

POSTOPERATIVE MANAGEMENT

Early functional mobilization starting on the first postoperative day.

RESULTS

A study by Lee et al. analyzed the clinical application of the system Mazor X Stealth Edition (Medtronic Navigation, Louisville, CO, USA; Medtronic Spine, Memphis, TN, USA) in 186 cases with a total of 1445 pedicle screws [1]. Correct screw positioning was achieved in 1432 pedicle screws (99.1%); six pedicle screws (0.4%) were revised intraoperatively. The mean duration of pedicle screw placement was 6.1 ± 2.3 min. Pojskić et al. published a case series regarding the application of the system Cirq (Brainlab, Munich, Germany) in 13 cases with a total number of 70 pedicle screws implanted [2]. Intraoperative imaging showed screw positioning according to the Gertzbein Robbins classification (GR) category A in 65 screws (92.9%) and GR B in one screw (1.4%). Screw positioning GR D with intraoperative revision was reported in two screws (2.9%). Mean duration of pedicle screw placement was 08:27 ± 06:54 min.

Cirq® robotic assistance for thoracolumbar pedicle screw placement - feasibility, accuracy, and safety

Introduction

New technologies providing higher degree of precision, less risk for damage and less harmful exposure to radiation are necessary for correct transpedicular screw trajectory, but their efficacy should be evaluated.

Research Question

Evaluate the feasibility, accuracy and safety of Brainlab Cirq® navigated robotic arm assistance for pedicle screw placement in comparison to fluoroscopic guidance.

Material and Methods

Group I "Cirq® robotic-assisted group" - 97 screws in 21 prospectively analyzed patients. Group II "Fluoroscopy-guided group" - 98 screws in 16 consecutive patients analyzed retrospectively. Comparative evaluations included screw accuracy on Gertzbein-Robbins's scale and fluoroscopy time. Time per screw and subjective mental workload (MWL) measured with the raw NASA task load index tool were assessed for Group I.

Results

195 screws were evaluated. Group I: 93 screws grade A (95.88%); 4 grade B (4.12%). In Group II, 87 screws grade A (88.78%); 9 grade B (9.18%); 1 grade C (1.02%); 1 grade D (1.02%). While the screws placed using the Cirq® system were more accurate overall, there was no statistical significance between the two groups, p=0.3714. There was no significant difference in operation length or radiation exposure between the two groups, however with the Cirq® system the radiation exposure for the surgeon was limited. Reduction in time per screw (p<0.0001) and in the MWL (p=0.0024) correlated with the surgeon's experience with Cirq®.

Discussion and Conclusion

The initial experience suggests that navigated, passive robotic arm assistance is feasible, at least as accurate as fluoroscopic guidance, and safe for pedicle screw placement.

Deformity Correction with Interbody Fusion Using Lateral versus Posterior Approach in Adult Degenerative Scoliosis: A Systematic Review and Observational Meta-analysis

This study was designed to systematically review and meta-analyze the functional and radiological outcomes between lateral and posterior approaches in adult degenerative scoliosis (ADS). Both lateral (lumbar, extreme, and oblique) and posterior interbody fusion (posterior lumbar and transforaminal) are used for deformity correction in patients with ADS with unclear comparison in this cohort of patients in the existing literature. A literature search using three electronic databases was performed to identify studies that reported outcomes of lateral (group L) and posterior interbody fusion (group P) in patients with ADS with curves of 10°-40°. Group P was further subdivided into minimally invasive surgery (MIS-P) and open posterior (Op-P) subgroups. Data on functional, radiological, and operative outcomes, length of hospital stay (LOHS), fusion rates, and complications were extracted and meta-analyzed using the random-effects model. A total of 18 studies (732 patients) met the inclusion criteria. No significant difference was found in functional and radiological outcomes between the two groups on data pooling. Total operative time in the MIS-P subgroup was less than that of group L (233.86 minutes vs. 401 minutes, p <0.05). The total blood loss in group L was less than that in the Op-P subgroup(477 mL vs. 1,325.6 mL, p <0.05). Group L had significantly less LOHS than the Op-P subgroup (4.15 days vs. 13.5 days, p <0.05). No significant difference was seen in fusion rates, but complications were seen except for transient sensorimotor weakness (group L: 24.3%, group P: 5.6%; p <0.05). Complications, such as postoperative thigh pain (7.7%), visceral injuries (2%), and retrograde ejaculation (3.7%), were seen only in group L while adjacent segment degeneration was seen only in group P (8.6%). Lateral approach has an advantage in blood loss and LOHS over the Op-P subgroup. The MIS-P subgroup has less operative time than group L, but with comparable blood loss and LOHS. No significant difference was found in functional, radiological, fusion rates, pseudoarthrosis, and complications, except for transient sensorimotor deficits. Few complications were approach-specific in each group.

Comparing radiation dose of image-guided techniques in lumbar fusion surgery with pedicle screw insertion; A systematic review

Background Context

Fluoroscopic devices can be used to visualize subcutaneous and osseous tissue, a useful feature during pedicle screw insertion in lumbar fusion surgery. It is important that both patient and surgeon are exposed as little as possible, since these devices use potential harmful ionizing radiation.

Purpose

This study aims to compare radiation exposure of different image-guided techniques in lumbar fusion surgery with pedicle screw insertion.

Study Design

Systematic review.

Methods

Cochrane, Embase, PubMed and Web of Science databases were used to acquire relevant studies. Eligibility criteria were lumbar and/or sacral spine, pedicle screw, mGray and/or Sievert and/or mrem, radiation dose and/or radiation exposure. Image-guided techniques were divided in five groups: conventional C-arm, C-arm navigation, C-arm robotic, O-arm navigation and O-arm robotic. Comparisons were made based on effective dose for patients and surgeons, absorbed dose for patients and surgeons and exposure. Risk of bias was assessed using the 2017 Cochrane Risk of Bias tool on RCTs and the Cochrane ROBINS-I tool on NRCTs. Level of evidence was assessed using the guidelines of Oxford Centre for Evidence-based Medicine 2011.

Results

A total of 1423 studies were identified of which 38 were included in the analysis and assigned to one of the five groups. Results of radiation dose per procedure and per pedicle screw were described in dose ranges. Conventional C-arm appeared to result in higher effective dose for surgeons, higher absorbed dose for patients and higher exposure, compared to C-arm navigation/robotic and O-arm navigation/robotic. Level of evidence was 3 to 4 in 29 studies. Risk of bias of RCTs was intermediate, mostly due to inadequate blinding. Overall risk of bias score in NRCTs was determined as 'serious'.

Conclusions

Ranges of radiation doses using different modalities during pedicle screw insertion in lumbar fusion surgery are wide. Based on the highest numbers in the ranges, conventional C-arm tends to lead to a higher effective dose for surgeons, higher absorbed dose for patients and higher exposure, compared to C-arm-, and O-arm navigation/robotic. The level of evidence is low and risk of bias is fairly high. In future studies, heterogeneity should be limited by standardizing measurement methods and thoroughly describing the image-guided technique settings.

The Use of High-Density Pedicle Screw Construct with Direct Vertebral Derotation of the Lowest Instrumented Vertebra in Selective Thoracic Fusion for Adolescent Idiopathic Scoliosis: Comparison of Two Surgical Strategies

Study Design

This study was a retrospective case series.

Purpose

This study was designed to determine whether direct vertebral rotation (DVR) of the lowest instrumented vertebra (LIV) using a high-density (HD) construct can reduce fusion segments without increasing adverse outcomes in selective thoracic fusion (STF) for adolescent idiopathic scoliosis (AIS).

Overview of Literature

LIV DVR is used to maximize spontaneous lumbar curve correction and reduce adverse outcomes during STF for AIS. However, evidence is limited on whether LIV DVR can allow a proximally located LIV and reduce fusion segments without increasing adverse outcomes.

Methods

We reviewed consecutive patients with Lenke 1 AIS who underwent STF from 2000 to 2017. The patients were divided into two groups based on the surgical strategy used: low-density (LD) construct without DVR of the LIV (LD group) versus HD construct with DVR of the LIV (HD group). We collected data on the patient's demographic characteristics, skeletal maturity, operative data, and measured radiological parameters in the preoperative and final follow-up radiographs. The occurrence of adding-on (AO) and coronal decompensation was also determined.

Results

In this study, 72 patients (five males and 67 females) with a mean age of 14.1±2.3 years were included. No significant differences in the demographics, skeletal maturity, and Lenke type distribution were observed between the two groups; however, the follow-up duration was significantly longer in the LD group (64.3±25.7 months vs. 40.7±22.2 months, p <0.001). The HD group had significantly shorter fusion segments (7.1±1.3 vs. 8.5±1.2, p <0.001) and a more proximal LIV level (12.1±0.9 vs. 12.7±1.0, p =0.009). In the radiological measurements, the improvement of LIV+1 rotation (Nash-Moe scale) was significantly larger in the HD group (0.53±0.51 vs. 0.21±0.41, p =0.008). AO and decompensation occurred in 7 (9.7%) and 4 (5.6%) patients in the HD and LD groups, respectively, without any significant difference between the two groups.

Conclusions

In this study, the HD group had a significantly shorter fusion level and a more proximal LIV than the LD group; however, the two groups had similar curve correction and adverse radiological outcome rates.

Statistical shape modelling of the thoracic spine for the development of pedicle screw insertion guides

Spinal fixation and fusion are surgical procedures undertaken to restore stability in the spine and restrict painful or degenerative motion. Malpositioning of pedicle screws during these procedures can result in major neurological and vascular damage. Patient-specific surgical guides offer clear benefits, reducing malposition rates by up to 25%. However, they suffer from long lead times and the manufacturing process is dependent on third-party specialists. The development of a standard set of surgical guides may eliminate the issues with the manufacturing process. To evaluate the feasibility of this option, a statistical shape model (SSM) was created and used to analyse the morphological variations of the T4-T6 vertebrae in a population of 90 specimens from the Visible Korean Human dataset (50 females and 40 males). The first three principal components, representing 39.7% of the variance within the population, were analysed. The model showed high variability in the transverse process (~ 4 mm) and spinous process (~ 4 mm) and relatively low variation (< 1 mm) in the vertebral lamina. For a Korean population, a standardised set of surgical guides would likely need to align with the lamina where the variance in the population is lower. It is recommended that this standard set of surgical guides should accommodate pedicle screw diameters of 3.5-6 mm and transverse pedicle screw angles of 3.5°-12.4°.

Comparing the efficacy and safety of cement-augmented fenestrated pedicle screws and conventional pedicle screw in surgery for spinal metastases: a retrospective comparative cohort study

Background

The incidence of cancer patients with bone metastasis is increasing annually. With the advancement of medical treatment for malignant tumors, the survival time of patients with spinal metastases is gradually being prolonged, and adjacent segment vertebral metastases often occur after conventional pedicle screw (CPS) surgery, leading to spinal instability, pain and nerve function injury again, with repeated symptoms. Combined pedicle screw fixation can maintain or reconstruct the spinal stability. This study aimed to investigate the efficacy and safety of cement-augmented fenestrated pedicle screws in the posterior approach for spinal metastases by comparing with CPS.

Methods

From January 2017 to August 2019, 52 patients with spinal metastases who underwent separation surgery and internal fixation via posterior approach were retrospectively enrolled. Cases were divided into the cement-augmented pedicle screw (CAPS) group (28 cases) and the CPS group (24 cases). The baseline data [age, gender, surgical sites, surgical segment, Tomita classification, Tomita score, Tokuhashi score, spinal instability neoplastic score (SINS)], surgical information, and local progression-free survival (PFS) time were compared between the two groups. Every patient was followed-up every 3 months with imaging examination. The visual analog scale (VAS) score and Frankel grade of the two groups were recorded before and 3 months after the operation were used to evaluate the efficacy. The operation time, the amount of intraoperative blood loss, the amount of bone cement injected in the pedicle screw group, and the complications of the surgery were recorded to evaluate the safety of CAPS.

Results

The baseline characteristics were comparable between the two group. Compared with the CPS group, the CAPS group showed significantly longer operation time (163±20 vs. 138±18 min, P<0.001) and lower VAS scores (2.93±1.33 vs. 4.17±1.34, P=0.002). Adjacent segment vertebral metastasis occurred in 10 cases (2 in the CAPS group and 8 in the CPS group, P=0.017). Internal implant failure occurred in 8 cases (1 in the CAPS group and 7 in the CPS group, P=0.011). Compared with the CPS group, the CAPS group had a significantly longer local PFS time (P<0.05).

Conclusions

CAPS could be a safe and effective choice in surgery for spinal metastases with the posterior approach.

Biomechanical Study on Three Screw-Based Atlantoaxial Fixation Techniques: A Finite Element Study

STUDY DESIGN

This is a finite element study.

PURPOSE

This study is aimed to compare the biomechanical behaviors of three screw-based atlantoaxial fixation techniques.

OVERVIEW OF LITERATURE

Screw-based constructs that are widely used to stabilize the atlantoaxial joint come with their own challenges in surgery. Clinical and in vitro studies have compared the effectiveness of screw-based constructs in joint fixation. Nevertheless, there is limited information regarding the biomechanical behavior of these constructs, such as the stresses and strains they experience.

METHODS

A finite element model of the upper cervical spine was developed. A type II dens fracture was induced in the intact model to produce the injured model. The following three constructs were simulated on the intact and injured models: transarticular screw (C1- C2TA), lateral mass screw in C1 and pedicle screw in C2 (C1LM1-C2PD), and lateral mass screw in C1 and translaminar screw in C2 (C1LM1-C2TL).

RESULTS

In the intact model, flexion-extension range of motion (ROM) was reduced by up to 99% with C11-C2TA and 98% with C1LM1-C2PD and C1LM1-C2TL. The lateral bending ROM in the intact model was reduced by 100%, 95%, and 75% with C11-C2TA, C1LM1-C2PD, and C1LM1-C2TL, respectively. The axial rotation ROM in the intact model was reduced by 99%, 98%, and 99% with C11-C2TA, C1LM1-C2PD, and C1LM1-C2TL, respectively. The largest maximum von Mises stress was predicted for C1LM1-C2TL (332 MPa) followed by C1LM1-C2PD (307 MPa) and C11-C2TA (133 MPa). Maximum stress was predicted to be at the lateral mass screw head of the C1LM1-C2TL construct.

CONCLUSIONS

Our model indicates that the biomechanical stability of the atlantoaxial joint in lateral bending with translaminar screws is not as reliable as that with transarticular and pedicle screws. Translaminar screws experience large stresses that may lead to failure of the construct before the required bony fusion occurs.

Derotation screws provide no advantage over polyaxial screws regarding coronal & sagittal correction in thoracic curves of AIS patients

PURPOSE

We compared two techniques for thoracic apical derotation; one using conventional reduction screws (Single-Innie-SI) and one requiring special derotation screws that can be converted to monoaxial screws to enhance dorotation (Dual-Innie-DI) for coronal and sagittal correction and.

METHODS

A total of 200 patients with thoracic AIS have been included. In the SI-Group (n = 127) the convex rod was applied first. Vertebral derotation was done by translation to the concave rod with the convex rod being in place and center of rotation (COR). In the DI-Group (n = 73) correction started with translation on the concave side as well but now followed by derotation around the concave rod using the DI-mechanism.

RESULTS

The mean rotation according to Raimondi and coronal correction was not sig. affected (72 (± 12) % in the SI-Group versus 68 (± 15) % in the DI-Group), even when flexibility was respected (Cincinnati Correction Index CCI was 2.9 (± 4.9) versus 3.5 (± 4.4). (p < 0.01). The gain of kyphosis was sig greater (2.7°) in the SI-group, but not clinical relevant.

CONCLUSION

The use of DI screws for apical derotation did not provide an advantage for coronal correction or derotation in thoracic curves. Presumably after translation is performed in the DI-group, there was too much tension and friction in the construct impeding further derotation. Simultaneous translation and derotation in the SI-group, with the convex rod being the COR, yielded similar correction with better kyphosis and was faster and more economic.

Qualitative Assessment of Titanium versus Carbon Fiber/Polyetheretherketone Pedicle Screw-Related Artifacts: A Cadaveric Study

BACKGROUND

Dorsal instrumentation and decompression are the mainstays of spinal tumor treatment. Replacing titanium screws with carbon fiber-reinforced polyetheretherketone (CFRP) screws can reduce imaging artifacts on neural structures and perturbations of radiation dose. Further reduction of metal content in such screws might enhance the benefit. The aim of this study was to assess the artifacts produced by all-titanium screws (Ti-Ti), CFRP thread-titanium screw heads (C-Ti), and all-CFRP screws (C-C).

METHODS

A cadaveric spine was used to place Ti-Ti, C-Ti, and C-C consecutively from T2 to S1. Computed tomography and 1.5T and 3T magnetic resonance imaging were performed for each screw system. Axial T1- and T2-weighted sequences of representative thoracic and lumbar regions were assessed for artifacts. The artifacts were classified as not relevant, considerable, or severe.

RESULTS

We evaluated 92 screws and made 178 artifact assessments. The artifacts were clearly visible in computed tomography scans but did not influence the visualization of intraspinal structures. Severe magnetic resonance imaging artifacts were found in 28% (17/60, mostly in the thoracic spine) of Ti-Ti, 2% (1/60, all T1 sequences) of C-Ti, and 0% of C-C, and considerable artifacts were found in 47% (28/60) of Ti-Ti, 10% (6/60, only 1 T2 sequence) of C-Ti, and 0% of C-C screws (P < 0.001).

CONCLUSIONS

CFRP pedicle screws reduced the artifact intensity in spinal structures compared with titanium screws, and may be beneficial for planning radiotherapy and for follow-up imaging. C-C demonstrated an enhanced effect on dorsal structures.

[Effects of short-segment pedicle screw internal fixation surgery combined with hyperbaric oxygen treatment for acute spinal injury on the morphology and function of the spine]

OBJECTIVE

To explore effect of short-segment pedicle screw internal fixation combined with hyperbaric oxygen in treating acute spinal fractures and its influence on recovery of spinal nerve function.

METHODS

A total of 96 patients with acute spinal fracture admitted from February 2017 to March 2020 were divided into combined group and control group, with 48 cases in each group. Both groups were treated with short-segment pedicle screw internal fixation. The combined group was given hyperbaric oxygen after surgery. The operation time, surgical blood loss, incision length and other general operation conditions between two groups were recorded. The differences in spinal morphology and function, Ameraican Spinal Injury Assiciation(ASIA) neurological function grade, serum inflammatory factors and ability of daily living activities were observed before and after surgery.

RESULTS

There was no significant difference in operation time, surgical blood loss, and incision length between combined group and control group(P>0.05). There were no significant differences in anterior height ratio and Cobb angle between two groups before surgery, 1 week and 6 months after surgery(P>0.05). The height ratio of anterior margin of the injured spine was significantly improved in both groups at 1 week and 6 months after surgery compared with preoperative period (P<0.05), and Cobb angle was significantly reduced in both groups compared with preoperative period (P<0.05). There was no statistically significant difference in serum interleukin-6(IL-6), interleukin-8(IL-8), and tumor necrosis factor-α(TNF-α) levels between two groups at 1 d after surgery(P>0.05);the serum IL-6, IL-8, and TNF-α levels of combined group were lower than those of control group at 1 week after surgery (P<0.05). At 6 months after surgery, ASIA neurological function grade of combined group was C grade in 2 cases, D grade in 23 cases, E grade in 22 cases. In control group, 7 cases was grade C, 26 cases was grade D, 13 cases was grade E, and the difference between two groups was statistically significant(P<0.05). The Barthel score of combined group was higher than that of control group at 1 month and 3 months after surgery, and the difference was statistically significant (P<0.05);at 6 months after surgery, there was no significant difference in Barthel score between two groups(P>0.05).

CONCLUSION

Short-segment pedicle screw internal fixation combined with hyperbaric oxygen for the treatment of acute spinal fractures is beneficial to the recovery of spinal nerve function after surgery, and has a certain effect on the early improvement of the patients' activities of daily living.

Predicting pullout strength of pedicle screws in broken bones from X-ray images

Pedicle screw fixation is one of the most common procedures used in spinal fusion surgery. The screw loosening is a major concern, which may be caused by broken pedicles. In vitro pullout tests or insertion torque are the main approaches for assessing the stability of the screw; however, direct evidence was lacking for clinical human spines. Here, we aim to provide a model that can predict the pullout strengths of pedicle screws in various pedicle conditions from X-ray images. A weighted embedded bone volume (EBV) model is proposed for pullout strengths prediction by considering the bone heterogeneity and confinement of the screw. We showed that the pullout strength is proportional to the EBV for homogeneous bone and the weighted EBV for layered composite bone. The proposed weighted EBV model is validated with in vitro Sawbones® pullout experiments. The results show that the model has better accuracy than the simple EBV model, with a coefficient of determination of 0.94. The proposed weighted EBV model can help assess the stability of a pedicle screw in a broken pedicle by simply examining 2D X-ray images.

Accuracy of pedicle screw placement using neuronavigation based on intraoperative 3D rotational fluoroscopy in the thoracic and lumbar spine

INTRODUCTION

In spinal surgery, precise instrumentation is essential. This study aims to evaluate the accuracy of navigated, O-arm-controlled screw positioning in thoracic and lumbar spine instabilities.

MATERIALS AND METHODS

Posterior instrumentation procedures between 2010 and 2015 were retrospectively analyzed. Pedicle screws were placed using 3D rotational fluoroscopy and neuronavigation. Accuracy of screw placement was assessed using a 6-grade scoring system. In addition, screw length was analyzed in relation to the vertebral body diameter. Intra- and postoperative revision rates were recorded.

RESULTS

Thoracic and lumbar spine surgery was performed in 285 patients. Of 1704 pedicle screws, 1621 (95.1%) showed excellent positioning in 3D rotational fluoroscopy imaging. The lateral rim of either pedicle or vertebral body was protruded in 25 (1.5%) and 28 screws (1.6%), while the midline of the vertebral body was crossed in 8 screws (0.5%). Furthermore, 11 screws each (0.6%) fulfilled the criteria of full lateral and medial displacement. The median relative screw length was 92.6%. Intraoperative revision resulted in excellent positioning in 58 of 71 screws. Follow-up surgery due to missed primary malposition had to be performed for two screws in the same patient. Postsurgical symptom relief was reported in 82.1% of patients, whereas neurological deterioration occurred in 8.9% of cases with neurological follow-up.

CONCLUSIONS

Combination of neuronavigation and 3D rotational fluoroscopy control ensures excellent accuracy in pedicle screw positioning. As misplaced screws can be detected reliably and revised intraoperatively, repeated surgery for screw malposition is rarely required.

Do the benefits of hook-hybrid construct justify their use over all-pedicle screws constructs in maintaining postoperative curve correction for adolescent idiopathic scoliosis patients from an Asian population?

STUDY DESIGN

Retrospective study.

OBJECTIVE

(1) Compare outcomes of all-pedicle screws (PS) and hook-hybrid (H) constructs in adolescent idiopathic scoliosis (AIS) patients; and (2) investigate whether BMI, height or pedicle size may modify the effect of the type of surgical construct on the extent of curve decompensation.

METHODS

AIS patients who underwent surgical fixation with H or PS constructs at a single tertiary institution were reviewed. Patients with implant density of at least 70% and 2-year follow-up were included. Demographic and perioperative data collected were age, sex, height, BMI, implant density and pedicle diameter. Cobb's angles and curve correction were compared preoperatively, postoperatively and at follow-up.

RESULTS

In total, 59 patients were included. H group had a lower pedicle size at the highest level of construct and at T4 compared to PS group. Postoperatively, H group (30.2° ± 11.7°) and PS group (32.1° ± 10.4°) had similar correction (mean diff. 2.0°, p = 0.516). At 2-year follow-up, H group (1.6° ± 3.5°) and PS group (0.1° ± 2.8°) had similar curve deterioration (mean diff. 1.5°, p = 0.079). Uni- and multivariate analyses revealed that BMI and height were not associated with curve deterioration at 2-year follow-up among the H and PS groups.

CONCLUSION

H constructs provided similar maintenance of curve correction at 2-year follow-up compared to PS constructs. BMI and Stature did not modify curve deterioration between both groups at follow-up. This study supports the use of H constructs when faced with difficult pedicle morphology associated with shorter stature as it provides comparable and satisfactory long-term maintenance of curve correction.

LEVEL OF EVIDENCE

Level III, retrospective cohort study.

[Development and clinical application of a new transverse process retractor based on computer-aided design and 3D printing technology]

OBJECTIVE

To manufacture a new type of transverse process retractor by using computer-aided design(CAD) combined with 3D printing technology and investigate its clinical application effect.

METHODS

A new type of transverse protrusion retractor was developed by CAD combined with 3D printing technology. From September 2018 to September 2019, the new transverse process retractor was applied in clinic. Sixty patients with lumbar single segment lesions who needed treatment by pedicle screw fixation, bone grafting and interbody fusion were divided into new transverse process retractor group and control group, with 30 cases in each group. There were 14 males and 16 females in new type transverse process retractor group, the age was (68.0±4.3) years old on average; lesion segment of 8 cases were L_3,4, 9 cases were L_4,5, 13 cases were L₅S₁;5 cases of lumbar disc herniation, 20 cases of lumbar spinal stenosis, 5 cases of degenerative lumbar spondylolisthesis;new transverse process retractor was used to pedicle screw placement. While there were 15 males and 15 females in control group, with an average age of (69.2±4.5) years old;lesion segment of 8 cases were L_3,4, 10 cases were L_4,5, 12 cases were L₅S₁;5 cases of lumbar disc herniation, 21 cases of lumbar spinal stenosis, 4 cases of degenerative lumbar spondylolisthesis;the traditional lamina retractor was used for soft tissue pulling and finished pedicle screw placement by freehand. The length of surgical incision, the time required for inserting a single screw, fluoroscopy times, the times of adjusting the positioning needle or screw in insertion process, and the visual analogue scale (VAS) of surgical incision 72 hours after operation were compared between two groups.

RESULTS

Using CAD and 3D printing technology, a new type of transverse protrusion retractor was developed quickly. The length of surgical incision, the time required for inserting a single screw, fluoroscopy time, and the times of adjusting the positioning needle or screw in insertion process in new transverse process retractor group were less than those in control group(P<0.05). There was no significant difference in VAS of lumbar incision pain at 72 hours after operation between two groups(P>0.05).

CONCLUSION

Using CAD combined with 3D printing technology to develop a new transverse protrusion retractor has the advantages of convenient design, short development cycle and low cost. It provides a new idea for the research and development of new medical devices. The new transverse process retractor has the advantages of easy operation, reliable fixation, less damage to paravertebral muscle, convenient pedicle screw placement, reducing fluoroscopy time and so on.

Anatomical analysis of the C2 pedicle in patients with basilar invagination

PURPOSE

To evaluate and describe the morphologic features of the C2 pedicle in patients with basilar invagination (BI) for informing the placement of pedicle screws. C2 pedicle screw placement is an important surgical technique for the treatment of atlantoaxial instability in patients with BI. However, no systematic and comprehensive anatomical study of the C2 pedicle in patients with BI has been reported.

METHODS

The data from 100 patients diagnosed with BI (BI group) and 100 patients without head or cervical disease (control group) were included in the study. Radiographic parameters, including the pedicle width, length, height, transverse angle, lamina angle, and superior angle, were measured and analyzed on CT images. After summary analysis, the effect of C2-3 congenital fusion on C2 pedicle deformity in patients with BI was also investigated.

RESULTS

The width, length, and height of the C2 pedicle of the BI patients were smaller than those of the control group. The pedicle cancellous bone was smaller in the BI group, while no significant difference in cortical bone was observed. In total, 44% of the pedicles were smaller than 4.5 mm in the BI group. Patients with C2-3 congenital fusion presented with smaller pedicle transverse angles and larger pedicle superior angles than those without fusion. Wide variations in the left and right angles of the pedicle were observed in the BI group with atlantoaxial dislocation or atlantooccipital fusion.

CONCLUSION

The C2 pedicle in the BI group was thinner than that in the control group due to a smaller cortical bone. Cases of C2-3 congenital fusion, atlantoaxial dislocation, and atlantooccipital fusion displayed variation in the angle of the C2 pedicle.

Pars interarticularis repair using pedicle screws and laminar hooks fixation technique in patients with symptomatic lumbar spondylolysis

Study Design: Prospective case series. Purpose: To assess the outcomes of pars repair surgery using pedicle screws and laminar hooks. Methods: This study was conducted on 22 patients with symptomatic lumbar spondylolysis. Curettage of the fibrocartilage in the defect and drilling of the sclerotic bone ends were done, followed by impaction of cancellous bone graft. Pedicle screws were inserted bilaterally in the corresponding pedicles and connected to a laminar hook via rods (screw-rod-hook fixation). The intensity of back pain and the functional outcome were assessed using the visual analog scale (VAS) and the Oswestry disability index (ODI). Plain radiographs were performed immediately postoperatively and after 3 and 6 months. CT scan was done at the final follow-up to assess pars healing. The mean follow-up period was 27 months. Results: The mean preoperative VAS and ODI were 7.4 ± 0.8 and 64.8 ± 6.7, which improved to 2.4 ± 0.8 and 20 ± 6 respectively at the final follow-up (P < 0.001). Healing of the defect was found in 19 patients at the final follow-up. Non-fusion with graft resorption was noticed in the remaining 3 cases (13.6%). However, postoperative VAS and ODI values improved even in the radiologically non-fused patients. Level of evidence: Therapeutic study, Level IV. Conclusion: Pars repair using pedicle screws and laminar hooks is a relatively simple yet effective procedure.

Comparison of novel machine vision spinal image guidance system with existing 3D fluoroscopy-based navigation system: a randomized prospective study

BACKGROUND CONTEXT

The use of spinal image guidance systems (IGS) has increased patient safety, accuracy, operative efficiency, and reduced revision rates in pedicle screw placement procedures. Traditional intraoperative 3D fluoroscopy or CT imaging produces potentially harmful ionizing radiation and increases operative time to register the patient. An IGS, FLASH Navigation, uses machine vision through high resolution stereoscopic cameras and structured visible light to build a 3D topographical map of the patient's bony surface anatomy enabling navigation use without ionizing radiation.

PURPOSE

We aimed to compare FLASH navigation system to a widely used 3D fluoroscopic navigation (3D) platform by comparing radiation exposure and pedicle screw accuracy.

DESIGN

A randomized prospective comparative cohort study of consecutive patients undergoing open posterior lumbar instrumented fusion.

PATIENT SAMPLE

Adults diagnosed with spinal pathology requiring surgical treatment and planning for open posterior lumbar fusion with pedicle screws implanted into 1-4 vertebral levels.

OUTCOME MEASURES

Outcome measures included mean intraoperative fluoroscopy time and dose, mean CT dose length product (DLP) for preoperative and day 2 CT, pedicle screw accuracy by CT, estimated blood loss and revision surgery rate.

METHODS

Consecutive patients were randomized 1:1 to FLASH or 3D and underwent posterior lumbar instrumented fusion. Radiation doses were recorded from pre- and postoperative CT and intraoperative 3D fluoroscopy. 2 independent blinded radiologists reviewed pedicle screw accuracy on CT.

RESULTS

A total of 429 (n=210 FLASH, n=219 3D) pedicle screws were placed in 90 patients (n=45 FLASH, n=45 3D) over the 18-month study period. Mean age and indication for surgery were similar between both groups, with a non-significantly higher ratio of males in the 3D group. Mean intraoperative fluoroscopy time and doses were significantly reduced in FLASH compared to 3D (4.51±3.71s vs 79.6±23.0s, p<.001 and 80.9±68.1cGycm² vs 3704.1±3442.4 cGycm², p<.001, respectively). This represented a relative reduction of 94.3% in the total intraoperative radiation time and a 97.8% reduction in the total intraoperative radiation dose. Mean preoperative CT DLP and mean day 2 postoperative CT DLP were significantly reduced in FLASH compared to 3D (662.0±440.4mGy-cm vs 1008.9±616.3 mGy-cm, p<.001 and 577.9±294.3 mGy-cm vs 980.7±441.6 mGy-cm, p<.001, respectively). This represented relative reductions of 34.4% and 41.0% in the preoperative CT dose and postoperative total DLP, respectively. The FLASH group required an average of 1.2 registrations in each case with an average of 2447 (±961.3) data points registered with a mean registration time of 106s (±52.1). A rapid re-registration mechanism was utilized in 22% (n=10/45) of cases and took 22.7s (±11.3). Re-registration was used in 7% (n=3/45) in the 3D group. Pedicle screw accuracy was high in FLASH (98.1%) and 3D (97.3%) groups with no pedicle breach >2mm in either group (p<.001). EBL was not statistically different between the groups (p=.38). No neurovascular injuries occurred, and no patients required return to theatre for screw repositioning.

CONCLUSIONS

FLASH and 3D IGS demonstrate high accuracy for pedicle screw placement. FLASH showed significant reduction in intraoperative radiation time and dose with lower but non-significant blood loss. FLASH showed significant reduction in preoperative and postoperative radiation, but this may be associated to the lower number of males/females preponderance in this group. FLASH provides similar accuracy to contemporary IGS without requiring 3D-fluoroscopy or radiolucent operating tables. Reducing registration time and specialized equipment may reduce costs.

Pedicle Screw Placement Using Intraoperative Computed Tomography and Computer-Aided Spinal Navigation Improves Screw Accuracy and Avoids Postoperative Revisions: Single-Center Analysis of 1400 Pedicle Screws

OBJECTIVE

Intraoperative computed tomography and navigation (iCT-Nav) is increasingly used to aid spinal instrumentation. We aimed to document the accuracy and revision rate of pedicle screw placement across many screws placed using iCT-Nav. We also assess patient-level factors predictive of high-grade pedicle breach.

METHODS

Medical records of patients who underwent iCT-Nav pedicle screw placement between 2015 and 2017 at a single center were retrospectively reviewed. Screw placement accuracy was individually assessed for each screw using the 2-mm incremental grading system for pedicle breach. Predictors of high-grade (>2 mm) breach were identified using multiple logistic regression.

RESULTS

In total, 1400 pedicle screws were placed in 208 patients undergoing cervicothoracic (29; 13.9%), thoracic (30; 14.4), thoracolumbar (19; 9.1%) and lumbar (130; 62.5%) surgeries. iCT-Nav afforded high-accuracy screw placement, with 1356 of 1400 screws (96.9%) being placed accurately. In total, 37 pedicle screws (2.64%) were revised intraoperatively during the index surgery across 31 patients, with no subsequent returns to the operating room because of screw malpositioning. After correcting for potential confounders, males were less likely to have a high-grade breach (odds ratio [OR] 0.21; 95% confidence interval [CI] 0.10-0.59, P = 0.003) whereas lateral (OR 6.21; 95% CI 2.47-15.52, P < 0.001) or anterior (OR 5.79; 95% CI2.11-15.88, P = 0.001) breach location were predictive of a high-grade breach.

CONCLUSIONS

iCT-Nav with postinstrumentation intraoperative imaging is associated with a reduced need for costly postoperative return to the operating room for screw revision. In comparison with studies of navigation without iCT where 1.5%-1.7% of patients returned for a second surgery, we report 0 revision surgeries due to screw malpositioning.

[Accuracy and safety of robot assisted pedicle screw placement]

OBJECTIVE

To investigate the accuracy and safety of pedicle screw placement assisted by orthopedic robot and C-arm fluoroscopy.

METHODS

The clinical data of 36 patients with spinal diseases underwent surgical treatment from January 2019 to August 2020 was retrospectively analyzed. Among them, 18 cases were implanted pedicle screws assisted by orthopaedic robot(observation group), including 12 males and 6 females, aged from 16 to 61 years with an average of (38.44±3.60) years;there were 1 case of adolescent scoliosis, 1 case of spinal tuberculosis, 7 cases of lumbar spondylolisthesis, 4 cases of thoracic fracture and 5 cases of lumbar fracture. Another 18 cases were implanted pedicle screws assisted by C-arm fluoroscopy(control group), including 10 males and 8 females, aged from 18 to 58 years with an average of (43.22±2.53) years;there were 1 case of adolescent scoliosis, 6 cases of lumbar spondylolisthesis, 6 cases of thoracic fracture and 5 cases of lumbar fracture. The intraoperative fluoroscopy times, nail placement time and postoperative complications were recorded in two groups. CT scan was performed after operation. The Gertzbein-Robbins standard was used to evaluate the accuracy of pedicle screw placement which was calculated.

RESULTS

The number of intraoperative fluoroscopy in observation group was(6.89±0.20) times, which was significantly higher than that in control group(14.00±0.18)times(P<0.05). The placement time of each screw in observation group was(2.56±0.12) min, which was significantly different from that in control group(4.22±0.17) min (P<0.05). One case of incision infection occurred in control group after operation, and recovered after active dressing change. During the follow-up period, no serious complications such as screw loosening and fracture occurred in two groups, and there was no significant difference in complications between two groups(P>0.05). A total of 107 screws were placed in observation group, including 101 screws in class A, 4 in class B, 2 in class C, 0 in class D and 0 in class E, the accuracy rate of pedicle screw placement=[(number of screws in class A+B) / the number of all screws placed in the group] ×100%=98.1%(105/107); and a total of 104 screws were placed in control group, including 90 screws in class A, 4 in class B, 5 in class C, 5 in class D and 0 in class E, the accuracy rate of pedicle screw implantation=[(number of screws in class A+B/the number of all screws placed in the group]×100%=90.3% (94/104); there was significant difference between two groups (P<0.05).

CONCLUSION

Orthopaedic robot assisted pedicle screw placement has the advantages of less fluoroscopy times, shorter screw placement time and higher accuracy, which can further improve the surgical safety and has a broad application prospect in the orthopaedic.

Complications associated with subaxial placement of pedicle screws versus lateral mass screws in the cervical spine: systematic review and meta-analysis comprising 1768 patients and 8636 screws

Lateral mass screw (LMS) fixation for the treatment of subaxial cervical spine instability or deformity has been traditionally associated with few neurovascular complications. However, cervical pedicle screw (CPS) fixation has recently increased in popularity, especially with navigation assistance, because of the higher pullout strength of the pedicle screws. To their knowledge, the authors conducted the first meta-analysis comparing the complication rates during and/or after CPS and LMS placement for different pathologies causing cervical spine instability. A systematic literature search of PubMed and Embase from inception to January 12, 2021 was performed to identify studies reporting CPS and/or LMS-related complications. Complications were categorized into intraoperative and early postoperative (within 30 days of surgery) and late postoperative (after 30 days from surgery) complications. All studies that met the prespecified inclusion criteria were pooled and cumulatively analyzed. A total of 24 studies were conducted during the time frame of the search and comprising 1768 participants and 8636 subaxially placed screws met the inclusion criteria. The CPS group experienced significantly more postoperative C5 palsy (odds ratio [OR] = 3.48, 95% confidence interval [CI] = 1.27-9.53, p < 0.05). Otherwise, there were no significant differences between the LMS and CPS groups. There were no significant differences between the CPS and LMS groups in terms of neurovascular procedure-related complications other than significantly more C5 palsy in the CPS group.

Dual pitch screw design provides equivalent fixation to upsized screw diameter in revision pedicle screw instrumentation: a cadaveric biomechanical study

BACKGROUND CONTEXT

There are situations that require the replacement of pedicle screws. They are often exchanged when loose or broken or to accommodate a different sized rod or pedicle screw system. Traditionally, pedicle screws are replaced by up-sizing the core diameter until an interference fit is obtained. However, this method carries a risk of pedicle screw breach.

PURPOSE

To determine if dual pitch screws, with cancellous pitch in the vertebral body and cortical pitch throughout the pedicle, allows for in-line screw revision without upsizing screw diameter.

STUDY DESIGN

Cadaveric biomechanical Study PATIENT SAMPLE: Not applicable OUTCOME MEASURES: Not applicable METHODS: Pedicle screws were tested in the lumbar vertebrae from eleven cadavers. Standard pitch 5.5 mm screws were inserted and loaded using a "break-in" protocol. Screws were removed and replaced with one of four screw types: 5.5 mm Standard Pitch, 5.5 mm Dual Pitch, 6.0 mm Standard Pitch, or 6.0 mm Dual Pitch. Failure testing was done using a stepwise increasing cyclic loading protocol for 100 cycles at each increasing load level. The loading consisted of a combined axial and bending load simulating the load seen by the most inferior screw.

RESULTS

Failure was consistent, with the tip of the screw displacing inferiorly into the vertebral body while simultaneously pulling out. Failure strength was lowest in the 5.5mm Standard (135.8±29.4N) followed by 6.0mm Standard (141.8±38.6N), 5.5mm Dual (158.1±53.8N), and 6.0mm Dual (173.6±52.1N, p=.023). There was no difference in the failure strength between the 5.5mm Dual and 6.0mm Standard. Lumbar level (p=.701) and donor spine (p=.062) were not associated with failure strength.

CONCLUSIONS

After pedicle screw removal, screws with a larger core diameter or with a dual pitch have similar failure strengths. Dual pitch screws may allow for in-line revision of screws without upsizing screw diameter, minimizing the risk of pedicle breach or fracture.

CLINICAL SIGNIFICANCE

Dual pitch screws, with cancellous pitch in the vertebral body and cortical pitch through the pedicle, allows for in-line revision of pedicle screws without upsizing screw diameter; reducing the risk of pedicle breach or fracture when exchanging screws.

Sagittal reduction of spinal deformity: Superior versus lateral screw-rod connection

INTRODUCTION

Spinal malalignment can greatly impact a patient's quality of life. Various sagittal parameters are used as realignment goals; however, about 50% of patients end up being under-corrected postoperatively. To improve the correction, prebent rods are available with a radius of curvature corresponding to the patient's "ideal" sagittal alignment. But no studies have been done on how the radius of curvature changes according to the type of connection between the pedicle screws and rods. The goal of this experimental study was to quantify how much prebent rods flatten based on the method used to connect the screw and rod: top-loading screw vs. dome screw with lateral connector.

METHODS

The experiment was done on a material testing system in axial compression on three constructs consisting of two rods secured with top-loading screws and three other constructs consisting of two rods secured with dome screws and lateral connector. The maximum angle of the construct was measured during loading and after removing the load. The primary outcome measure was the mean angle in each construct at each step.

RESULTS

The mean angle of the constructs with top-loading screws when subjected to 500 N load was significantly less than in the constructs with dome screws and lateral connector: 18.6° vs. 24.5° respectively (p<0.0003). The mean angle of the constructs with top-loading screws after removing the load was significantly less than in the constructs with dome screws and lateral connector: 25.7° vs. 32.3° respectively, (p<0.0005).

CONCLUSION

In vitro, top-loading screws produced significantly greater flattening than dome screws with lateral connector. These findings must be confirmed in vivo. Understanding the behavior of rods as a function of the type of screw connection can be an important factor to minimize the risk of under-correction in the sagittal plane.

LEVEL OF EVIDENCE

III.

A meta-analysis of complications associated with the use of cement-augmented pedicle screws in osteoporosis of spine

PURPOSE

Our study aimed to provide updated and comprehensive evidence on the complications associated with the use of cement-augmented pedicle screws (CAPS) in osteoporosis patients undergoing spinal instrumentation.

METHODS

Databases of PubMed, Embase, Ovoid, and Google Scholar were screened from January 2000-February 2020 for studies reporting complications of CAPS in osteoporosis patients. Pooled estimates (with 95% confidence intervals) were calculated.

RESULTS

Twenty studies were included. The pooled risk of screw loosening, screw breakage and screw migration was 2.0% (0.2%-4.9%), 0.6% (0%-2.0%) and 0.2% (0%-1.2%) respectively. On pooling of data from 1277 patients, we found the risk of all cement leakage to be 21.8% (6%-43.1%). However, data from 1654 patients indicated the risk of symptomatic cement leakage was 1.2% (0.6%-1.9%). The incidence of pulmonary embolism was 3.0% (0.5%-6.8%) while the risk of symptomatic pulmonary embolism was 0.8% (0.2%-1.5%). Pooled risk of neurovascular complications was 1.6% (0.3%-3.6%), adjacent compression fracture was 3.3% (1.2%-6.2%) and infectious complications was 3.1% (1.1%-5.7%). There were high heterogeneity and variability in the study outcomes.

CONCLUSION

The incidence of screw-related complications like loosening, breakage, and migration with the use of CAPS in spinal instrumentation of osteoporotic patients is low. The risk of cement leakage is high and variable but the incidence of symptomatic cement leakage and related neurovascular or pulmonary complications is low. Further studies using homogenous methods of reporting are needed to strengthen current evidence.

LEVEL OF EVIDENCE

II, Systematic Review and Meta-analysis.

Vertebral augmentation plus short-segment fixation versus vertebral augmentation alone in Kümmell's disease: a systematic review and meta-analysis

Osteoporotic vertebral compression fractures of the thoracolumbar spine can progress to Kümmell's disease, an avascular vertebral osteonecrosis. Vertebral augmentation (VA)-vertebroplasty and/or kyphoplasty-is the main treatment modality, but additional short-segment fixation (SSF) has been recommended concomitant to VA. The aim is to compare clinical and radiological outcomes of VA + SSF versus VA alone. Systematic review, including comparative articles in Kümmell's disease, was performed. This study assessed the following outcome measurements: visual analog scale (VAS), Oswestry Disability Index (ODI), anterior vertebral height (AVH), local kyphotic angle (LKA), operative time, blood loss, length of stay, and cement leakage. Six retrospective studies were included, with 126 patients in the VA + SSF group and 152 in VA alone. Pooled analysis showed the following: VAS, non-significant difference favoring VA + SSF: MD -0.61, 95% CI (-1.44, 0.23), I² 91%, p = 0.15; ODI, non-significant difference favoring VA + SSF: MD -9.85, 95% CI (-19.63, -0.07), I² 96%, p = 0.05; AVH, VA + SSF had a non-significant difference over VA alone: MD -3.21 mm, 95% CI (-7.55, 1.14), I² 92%, p = 0.15; LKA, non-significant difference favoring VA + SSF: MD -0.85°, 95% CI (-5.10, 3.40), I² 95%, p = 0.70. There were higher operative time, blood loss, and hospital length of stay for VA + SSF (p < 0.05), but with lower cement leakage (p < 0.05). VA + SFF and VA alone are effective treatment modalities in Kümmell's disease. VA + SSF may provide superior long-term results in clinical and radiological outcomes but required a longer length of stay.

Clinical efficiency of operating room-based sliding gantry CT as compared to mobile cone-beam CT-based navigated pedicle screw placement in 853 patients and 6733 screws

PURPOSE

Multiple solutions for navigation-guided pedicle screw placement are available. However, the efficiency with regard to clinical and resource implications has not yet been analyzed. The present study's aim was to analyze whether an operating room sliding gantry CT (ORCT)-based approach for spinal instrumentation is more efficient than a mobile cone-beam CT (CBCT)-based approach.

METHODS

This cohort study included a random sample of 853 patients who underwent spinal instrumentation using ORCT-based or CBCT-based pedicle screw placement due to tumor, degenerative, trauma, infection, or deformity disorders between November 2015 and January 2020.

RESULTS

More screws had to be revised intraoperatively in the CBCT group due to insufficient placement (ORCT: 98, 2.8% vs. CBCT: 128, 4.0%; p = 0.0081). The mean time of patients inside the OR (Interval 5 Entry-Exit) was significantly shorter for the ORCT group (ORCT: mean, [95% CI] 256.0, [247.8, 264.3] min, CBCT: 283.0, [274.4, 291.5] min; p < 0.0001) based on shorter times for Interval 2 Positioning-Incision (ORCT: 18.8, [18.1, 19.9] min, CBCT: 33.6, [32.2, 35.5] min; p < 0.0001) and Interval 4 Suture-Exit (ORCT: 24.3, [23.6, 26.1] min, CBCT: 29.3, [27.5, 30.7] min; p < 0.0001).

CONCLUSIONS

The choice of imaging technology for navigated pedicle screw placement has significant impact on standard spine procedures even in a high-volume spine center with daily routine in such devices. Particularly with regard to the duration of surgeries, the shorter time needed for preparation and de-positioning in the ORCT group made the main difference, while the accuracy was even higher for the ORCT.

Bone density optimized pedicle screw instrumentation improves screw pull-out force in lumbar vertebrae

Pedicle screw instrumentation is performed in the surgical treatment of a wide variety of spinal pathologies. A common postoperative complication associated with this procedure is screw loosening. It has been shown that patient-specific screw fixation can be automated to match standard clinical practice and that failure can be estimated preoperatively using computed tomography images. Hence, we set out to optimize three-dimensional preoperative planning to achieve more mechanically robust screw purchase allowing deviation from intuitive, standard screw parameters. Toward this purpose, we employed a genetic algorithm optimization to find optimal screw sizes and trajectories by maximizing the CT derived bone mechanical properties. The method was tested on cadaveric lumbar vertebrae (L1 to L5) of four human spines (2 female/2 male; age range 60-78 years). The main boundary conditions were the predefined, level-dependent areas of possible screw entry points, as well as the automatically located pedicle structures. Finite element analysis was used to compare the genetic algorithm output to standard clinical planning of screw positioning in terms of the simulated pull-out strength. The genetic algorithm optimization successfully found screw sizes and trajectories that maximize the sum of the Young's modulus within the screw's volume for all 40 pedicle screws included in this study. Overall, there was a 26% increase in simulated pull-out strength for optimized compared to traditional screw trajectories and sizes. Our results indicate that optimizing pedicle screw instrumentation in lumbar vertebrae based on bone quality measures improves screw purchase as compared to traditional instrumentation.